sdp_types/

attributes.rs

// Copyright (C) 2026 Taruntej Kanakamalla <tarun@centricular.com>
//
// Licensed under the MIT license, see the LICENSE file or <http://opensource.org/licenses/MIT>

//! Contains all the Session description Attributes defined as Structs/Enums

use std::{
    convert::TryFrom,
    fmt::{Display, Write},
    net::IpAddr,
    str::FromStr,
};

use crate::{
    builders, enums::*, parse_connection_address, parse_connection_ip_address, parser::is_token,
    Attribute, ConnectionAddress, ConnectionAddressError,
};

/// Trait for Typed Attribute structs
pub trait TypedAttribute: Display + FromStr<Err = AttributeError> {
    const NAME: &'static str;
}

impl<T: TypedAttribute> From<T> for Attribute {
    fn from(attr: T) -> Attribute {
        let value = attr.to_string();
        Attribute {
            attribute: T::NAME.to_string(),
            // Property attributes format as the empty string and carry no value.
            value: (!value.is_empty()).then_some(value),
        }
    }
}

/// Attribute error with specific details
#[derive(Debug, PartialEq, Eq, thiserror::Error)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub enum AttributeError {
    /// If an Attribute is not found in a media or the session
    #[error("Attribute {} not found", .0)]
    NotFound(String),
    /// If a parameter is missing in an attribute
    #[error("Param {} not found in {}", .param, .attr)]
    ParamNotFound { param: String, attr: String },
    /// If a parameter value is not valid type or not in range
    #[error("Invalid value {} for Param {} in {}", .val ,.param, .attr)]
    InvalidParamValue {
        param: String,
        val: String,
        attr: String,
    },
    /// If an attribute is not in expected format
    #[error("Unsupported attribute format: {} for {}", .val, .attr)]
    UnsupportedFormat { val: String, attr: String },
    /// If there are more than expected items trailing in the attribute parameters
    #[error("Unexpected trailing item {} for in {}", .val, .attr)]
    UnexpectedTrailingItem { val: String, attr: String },
    /// Unspecified error
    #[error("{}: {}", .attr, .error)]
    Other { error: String, attr: String },
}

impl AttributeError {
    pub fn is_attribute_not_found(&self) -> bool {
        matches!(self, AttributeError::NotFound(_))
    }

    /// Preprends the provided `param_context` to the parameter field of this AttributeError if applicable
    fn add_param_context(&mut self, param_context: &str) {
        use AttributeError::*;
        match self {
            NotFound(_)
            | Other { .. }
            | UnsupportedFormat { .. }
            | UnexpectedTrailingItem { .. } => (),
            ParamNotFound { param, .. } | InvalidParamValue { param, .. } => {
                param.push(')');
                param.insert_str(0, " (");
                param.insert_str(0, param_context);
            }
        }
    }

    /// Sets the attribute field of this AttributeError to new_attr
    pub(crate) fn set_attr(&mut self, new_attr: impl ToString) {
        use AttributeError::*;
        match self {
            NotFound(attr)
            | ParamNotFound { attr, .. }
            | InvalidParamValue { attr, .. }
            | UnsupportedFormat { attr, .. }
            | UnexpectedTrailingItem { attr, .. }
            | Other { attr, .. } => *attr = new_attr.to_string(),
        }
    }
}

pub(crate) trait ErrorContext {
    fn with_param_context(self, param_context: &str) -> Self;
    fn with_attr(self, new_attr: impl ToString) -> Self;
}

impl<T> ErrorContext for Result<T, AttributeError> {
    /// Returns this error with the provided `param_context` prepended to the parameter field if applicable
    fn with_param_context(self, param_context: &str) -> Self {
        self.map_err(|mut err| {
            err.add_param_context(param_context);
            err
        })
    }

    /// Returns this error with the attribute field set to new_attr
    fn with_attr(self, new_attr: impl ToString) -> Self {
        self.map_err(|mut err| {
            err.set_attr(new_attr);
            err
        })
    }
}

/// RtpMap Attribute
///
/// See [RFC 8866 Section 6.6](https://datatracker.ietf.org/doc/html/rfc8866#section-6.6) for more details
#[derive(Debug, Clone, PartialEq, Eq)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct RtpMap {
    /// Payload type, a numerical value between 0 and 127
    pub payload_type: u8,
    /// Name of the encoding
    // TODO: is it useful to have an enum for all known encoding?
    pub encoding_name: String,
    /// Clock rate
    pub clock_rate: u32,
    /// Encoding parameters.
    ///
    /// Currently used only for audio channel count
    pub encoding_params: Option<String>,
}

impl RtpMap {
    pub fn new(payload_type: u8, encoding_name: impl ToString, clock_rate: u32) -> Self {
        RtpMap {
            payload_type,
            encoding_name: encoding_name.to_string(),
            clock_rate,
            encoding_params: None,
        }
    }

    pub fn builder(
        payload_type: u8,
        encoding_name: impl ToString,
        clock_rate: u32,
    ) -> builders::RtpMap {
        builders::RtpMap::new(payload_type, encoding_name, clock_rate)
    }

    pub fn with_encoding_params(
        payload_type: u8,
        encoding_name: impl ToString,
        clock_rate: u32,
        encoding_params: impl ToString,
    ) -> Self {
        RtpMap {
            payload_type,
            encoding_name: encoding_name.to_string(),
            clock_rate,
            encoding_params: Some(encoding_params.to_string()),
        }
    }

    pub fn set_encoding_params(&mut self, encoding_params: impl ToString) {
        self.encoding_params = Some(encoding_params.to_string());
    }
}

impl FromStr for RtpMap {
    type Err = AttributeError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        let Some((pt, rest)) = s.split_once(' ') else {
            return Err(AttributeError::UnsupportedFormat {
                val: s.to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        };

        let Ok(pt) = pt.parse::<u8>() else {
            return Err(AttributeError::InvalidParamValue {
                param: "Payload type".to_string(),
                val: pt.to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        };

        if pt > 127 {
            return Err(AttributeError::InvalidParamValue {
                param: "Payload type".to_string(),
                val: format!("{pt}(expected 0-127)"),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        }

        let mut i = rest.splitn(3, '/');
        let Some(encoding) = i.next() else {
            return Err(AttributeError::ParamNotFound {
                param: "Encoding name".to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        };

        let Some(clock_rate) = i.next() else {
            return Err(AttributeError::ParamNotFound {
                param: "Clock rate".to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        };

        let Ok(clock_rate) = clock_rate.parse::<u32>() else {
            return Err(AttributeError::InvalidParamValue {
                param: "Clock rate".to_string(),
                val: clock_rate.to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        };

        let params = i.next().map(String::from);

        Ok(Self {
            payload_type: pt,
            encoding_name: encoding.to_owned(),
            clock_rate,
            encoding_params: params,
        })
    }
}

impl Display for RtpMap {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(
            f,
            "{} {}/{}",
            self.payload_type, self.encoding_name, self.clock_rate
        )?;
        if let Some(params) = &self.encoding_params {
            f.write_char('/')?;
            f.write_str(params)?;
        }
        Ok(())
    }
}

impl TypedAttribute for RtpMap {
    const NAME: &'static str = "rtpmap";
}

/// Format specific parameters
#[derive(Debug, Clone, PartialEq, Eq)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct FmtpParam {
    pub param: String,
    pub val: Option<String>,
}

impl FmtpParam {
    pub fn new(param: impl ToString) -> Self {
        FmtpParam {
            param: param.to_string(),
            val: None,
        }
    }

    pub fn builder(param: impl ToString) -> builders::FmtpParam {
        builders::FmtpParam::new(param)
    }

    pub fn with_value(param: impl ToString, value: impl ToString) -> Self {
        FmtpParam {
            param: param.to_string(),
            val: Some(value.to_string()),
        }
    }

    pub fn set_value(&mut self, value: impl ToString) {
        self.val = Some(value.to_string());
    }
}

/// Format Parameters
///
/// See [RFC 8866 Section 6.15](https://datatracker.ietf.org/doc/html/rfc8866#section-6.15) for more details
#[derive(Debug, Clone, PartialEq, Eq)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct Fmtp {
    /// Payload format
    pub fmt: u8,
    /// Format specific parameters
    // Multiple params are expected to be semicolon separated
    // Each param can be a 'key=value' pair or just single parameter
    pub format_specific_params: Vec<FmtpParam>,
}

impl Fmtp {
    pub fn new(fmt: u8) -> Self {
        Fmtp {
            fmt,
            format_specific_params: vec![],
        }
    }

    pub fn builder(fmt: u8) -> builders::Fmtp {
        builders::Fmtp::new(fmt)
    }

    pub fn add_format_specific_param(&mut self, format_specific_param: FmtpParam) {
        self.format_specific_params.push(format_specific_param)
    }

    pub fn add_format_specific_params(
        &mut self,
        format_specific_params: impl IntoIterator<Item = FmtpParam>,
    ) {
        self.format_specific_params.extend(format_specific_params)
    }
}

impl FromStr for Fmtp {
    type Err = AttributeError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        let Some((fmt, rest)) = s.split_once(' ') else {
            return Err(AttributeError::UnsupportedFormat {
                val: s.to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        };

        let Ok(fmt) = fmt.parse::<u8>() else {
            return Err(AttributeError::InvalidParamValue {
                param: "fmtp".to_string(),
                val: fmt.to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        };

        let mut params: Vec<FmtpParam> = Vec::new();
        for param in rest.split(';') {
            if let Some((key, value)) = param.split_once('=') {
                params.push(FmtpParam {
                    param: key.to_string(),
                    val: Some(value.to_string()),
                });
            } else {
                params.push(FmtpParam {
                    param: param.to_string(),
                    val: None,
                });
            }
        }

        Ok(Self {
            fmt,
            format_specific_params: params,
        })
    }
}

impl Display for Fmtp {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{} ", self.fmt)?;
        let mut iter = self.format_specific_params.iter().peekable();
        while let Some(p) = iter.next() {
            write!(f, "{}", p.param)?;
            if let Some(val) = &p.val {
                f.write_char('=')?;
                f.write_str(val.as_str())?;
            }
            if iter.peek().is_some() {
                f.write_char(';')?;
            }
        }
        Ok(())
    }
}

impl TypedAttribute for Fmtp {
    const NAME: &'static str = "fmtp";
}

/// RTCP port number and address
///
/// To be used if not algorithmically derived
/// from the RTP port described in the media line
///
/// The address part is optional: when absent, RTCP is sent to the
/// connection address given for the media.
///
/// See [RFC 3605 Section 2.1](https://datatracker.ietf.org/doc/html/rfc3605#section-2.1)
#[derive(Debug, Clone, PartialEq, Eq)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct Rtcp {
    /// Port used for the RTCP stream
    pub port: u16,
    /// Network Type
    ///
    /// `None` if the address part is absent
    pub nettype: Option<NetType>,
    /// Address type
    ///
    /// `None` if the address part is absent
    pub addrtype: Option<AddrType>,
    /// Connection address: can be IP Address, unicast, multicast, ...
    /// Conformity may be checked against the `addrtype`.
    ///
    /// `None` if the address part is absent
    pub connection_address: Option<String>,
}

impl Rtcp {
    /// Construct an [`Rtcp`] with only a port number, i.e. without an address
    /// part.
    ///
    /// RTCP is then sent to the connection address given for the media.
    pub fn with_port(port: u16) -> Self {
        Rtcp {
            port,
            nettype: None,
            addrtype: None,
            connection_address: None,
        }
    }

    /// Construct an [`Rtcp`] with the specified IP `connection_address`
    pub fn with_ip_addr(port: u16, connection_address: impl Into<IpAddr>) -> Self {
        let connection_address = connection_address.into();
        Rtcp {
            port,
            nettype: Some(NetType::In),
            addrtype: Some(connection_address.into()),
            connection_address: Some(connection_address.to_string()),
        }
    }

    /// Construct an [`Rtcp`]
    ///
    /// See also [`Rtcp::with_ip_addr`] and [`Rtcp::with_port`]
    pub fn new(
        port: u16,
        nettype: NetType,
        addrtype: AddrType,
        connection_address: impl ToString,
    ) -> Self {
        Rtcp {
            port,
            nettype: Some(nettype),
            addrtype: Some(addrtype),
            connection_address: Some(connection_address.to_string()),
        }
    }

    /// Tries to parse the `connection_address` `String` of `self` as `IpAddr`
    ///
    /// An optional time-to-live suffix in `address/ttl` notation
    /// ([RFC 8866 Section 5.7](https://tools.ietf.org/html/rfc8866#section-5.7))
    /// is ignored, see [`Rtcp::try_address`].
    ///
    /// Returns `None` if the address part is absent, the `Ok` with the parsed
    /// `IpAddr` or `Err` with the string address if parsing failed.
    #[deprecated(since = "0.3.1", note = "use Rtcp::try_address instead")]
    pub fn try_parse_connection_ip_address(&self) -> Option<Result<IpAddr, &str>> {
        self.connection_address
            .as_deref()
            .map(parse_connection_ip_address)
    }

    /// The effective `addrtype` of the `connection_address`
    ///
    /// The `addrtype` field, or the address family inferred from the parsed
    /// `IpAddr` if the field is `None`. `None` if the address part is absent
    /// or its address family cannot be determined.
    fn effective_addrtype(&self) -> Option<AddrType> {
        self.addrtype.clone().or_else(|| {
            let address = parse_connection_ip_address(self.connection_address.as_deref()?).ok()?;
            Some(address.into())
        })
    }

    /// Parses the `connection_address` into its components
    ///
    /// The `connection_address` of `a=rtcp` reuses the SDP connection
    /// address token, so a multicast address may carry a time-to-live and a
    /// number-of-addresses count in `address/ttl[/count]` notation, e.g.
    /// `"224.2.1.1/16/3"`
    /// ([RFC 3605 Section 2](https://datatracker.ietf.org/doc/html/rfc3605#section-2),
    /// [RFC 8866 Section 5.7](https://tools.ietf.org/html/rfc8866#section-5.7)).
    ///
    /// The address must parse as an [`IpAddr`]; an IPv4 multicast
    /// time-to-live and a number-of-addresses suffix must parse as numbers.
    /// A time-to-live is only defined for "IP4", for "IP6" the only suffix
    /// is the address count.
    ///
    /// Returns `None` if the address part is absent, otherwise the parsed
    /// [`ConnectionAddress`] or a [`ConnectionAddressError`] for the first
    /// invalid component.
    pub fn try_address(&self) -> Option<Result<ConnectionAddress, ConnectionAddressError>> {
        let address = self.connection_address.as_deref()?;
        match self.effective_addrtype() {
            Some(addrtype) => Some(parse_connection_address(address, &addrtype)),
            None => Some(Err(ConnectionAddressError::InvalidAddress(
                address.to_string(),
            ))),
        }
    }

    /// Whether the `connection_address` is an IP multicast address
    ///
    /// Returns `false` if the address part is absent or cannot be parsed as
    /// an [`IpAddr`].
    pub fn is_multicast(&self) -> bool {
        matches!(self.connection_address.as_deref().map(parse_connection_ip_address),
            Some(Ok(address)) if address.is_multicast())
    }

    /// Like [`Rtcp::is_multicast`] but returns the parse error instead
    /// of `false` if the address cannot be parsed. Only the address itself
    /// is considered, invalid TTL or address-count suffixes do not error.
    ///
    /// Returns `None` if the address part is absent.
    pub fn try_is_multicast(&self) -> Option<Result<bool, ConnectionAddressError>> {
        let address = self.connection_address.as_deref()?;
        Some(
            parse_connection_ip_address(address)
                .map(|address| address.is_multicast())
                .map_err(|_| ConnectionAddressError::InvalidAddress(address.to_string())),
        )
    }

    /// Whether the `connection_address` is an IPv4 address
    ///
    /// Returns `false` if the address part is absent or cannot be parsed as
    /// an [`IpAddr`].
    pub fn is_ipv4(&self) -> bool {
        matches!(self.connection_address.as_deref().map(parse_connection_ip_address),
            Some(Ok(address)) if address.is_ipv4())
    }

    /// Whether the `connection_address` is an IPv6 address
    ///
    /// Returns `false` if the address part is absent or cannot be parsed as
    /// an [`IpAddr`].
    pub fn is_ipv6(&self) -> bool {
        matches!(self.connection_address.as_deref().map(parse_connection_ip_address),
            Some(Ok(address)) if address.is_ipv6())
    }

    /// Sets the `connection_address` & `addrtype` of `self` from the specified `IpAddr`
    ///
    /// Also sets the `nettype` to `IN` if it is not set yet.
    pub fn set_connection_ip_address(&mut self, connection_address: impl Into<IpAddr>) {
        let connection_address = connection_address.into();
        self.nettype.get_or_insert(NetType::In);
        self.addrtype = Some(connection_address.into());
        self.connection_address = Some(connection_address.to_string());
    }
}

impl FromStr for Rtcp {
    type Err = AttributeError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        // Runs of spaces are a single separator, like in o= and c= lines,
        // so that no field can end up empty.
        let mut i = s.split(' ').filter(|part| !part.is_empty());
        let Some(port) = i.next() else {
            return Err(AttributeError::ParamNotFound {
                param: "Port".to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        };

        let Ok(port) = port.parse::<u16>() else {
            return Err(AttributeError::InvalidParamValue {
                param: "Port".to_string(),
                val: port.to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        };

        // The address part is optional (RFC 3605): if the port is the only
        // field, RTCP is sent to the media's connection address.
        let Some(nettype) = i.next() else {
            return Ok(Self::with_port(port));
        };

        // RFC 3605 reuses the SDP nettype and addrtype tokens (RFC 8866,
        // section 9), same as in o= and c= lines.
        if !is_token(nettype.as_bytes()) {
            return Err(AttributeError::InvalidParamValue {
                param: "Network type".to_string(),
                val: nettype.to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        }
        let nettype = NetType::from_str(nettype).expect("infallible");

        let Some(addrtype) = i.next() else {
            return Err(AttributeError::ParamNotFound {
                param: "Address type".to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        };

        if !is_token(addrtype.as_bytes()) {
            return Err(AttributeError::InvalidParamValue {
                param: "Address type".to_string(),
                val: addrtype.to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        }
        let addrtype = AddrType::from_str(addrtype).expect("infallible");

        let Some(connection_address) = i.next() else {
            return Err(AttributeError::ParamNotFound {
                param: "Connection address".to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        };

        if let Some(unexpected) = i.next() {
            return Err(AttributeError::UnexpectedTrailingItem {
                val: unexpected.to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        }

        Ok(Self {
            port,
            nettype: Some(nettype),
            addrtype: Some(addrtype),
            connection_address: Some(connection_address.to_string()),
        })
    }
}

impl Display for Rtcp {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{}", self.port)?;
        if let Some(nettype) = &self.nettype {
            write!(f, " {nettype}")?;
        }
        if let Some(addrtype) = &self.addrtype {
            write!(f, " {addrtype}")?;
        }
        if let Some(connection_address) = &self.connection_address {
            write!(f, " {connection_address}")?;
        }
        Ok(())
    }
}

impl TypedAttribute for Rtcp {
    const NAME: &'static str = "rtcp";
}

/// RTCP Feedback Capability
///
/// See [RFC 4585 Section 4.2](https://datatracker.ietf.org/doc/html/rfc4585#section-4.2)
#[derive(Debug, PartialEq, Eq, Clone)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct RtcpFb {
    /// Payload format for which feedback messages may be used
    pub pt: RtcpFbPt,
    /// RTCP Feedback value
    pub val: RtcpFbVal,
}

impl RtcpFb {
    pub fn new(pt: impl Into<RtcpFbPt>, val: impl Into<RtcpFbVal>) -> Self {
        RtcpFb {
            pt: pt.into(),
            val: val.into(),
        }
    }
}

impl FromStr for RtcpFb {
    type Err = AttributeError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        let mut i = s.split(' ');
        let Some(pt) = i.next() else {
            return Err(AttributeError::ParamNotFound {
                param: "Payload format".to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        };

        let pt = if let Ok(pt) = pt.parse::<u8>() {
            RtcpFbPt::Fmt(pt)
        } else if pt == "*" {
            RtcpFbPt::Wildcard
        } else {
            return Err(AttributeError::InvalidParamValue {
                param: "Payload format".to_string(),
                val: pt.to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        };

        let Some(val) = i.next() else {
            return Err(AttributeError::ParamNotFound {
                param: "Rtcp feedback value".to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        };

        let rtcp_fb_val = match val {
            "ack" => {
                if let Some(ack_val) = i.next() {
                    let ack_val = match ack_val {
                        "rpsi" => RtcpFbAck::Rpsi,
                        "app" => {
                            if let Some(app_param) = i.next() {
                                RtcpFbAck::App(Some(app_param.to_string()))
                            } else {
                                RtcpFbAck::App(None)
                            }
                        }
                        "ccfb" => {
                            // The payload type used with "ccfb" feedback MUST be the wildcard type
                            // See https://datatracker.ietf.org/doc/html/rfc8888#section-6
                            if let RtcpFbPt::Fmt(pt) = pt {
                                return Err(AttributeError::InvalidParamValue {
                                    param: "Payload type of Congestion control feedback (ccfb)"
                                        .to_string(),
                                    val: format!("{pt}(expected wildcard (*))"),
                                    attr: <Self as TypedAttribute>::NAME.to_string(),
                                });
                            } else {
                                RtcpFbAck::Ccfb
                            }
                        }
                        other => RtcpFbAck::Other(other.to_string()),
                    };
                    RtcpFbVal::Ack(Some(ack_val))
                } else {
                    RtcpFbVal::Ack(None)
                }
            }
            "nack" => {
                if let Some(nack_val) = i.next() {
                    let nack_val = match nack_val {
                        "pli" => RtcpFbNack::Pli,
                        "sli" => RtcpFbNack::Sli,
                        "rpsi" => RtcpFbNack::Rpsi,
                        "app" => {
                            if let Some(app_param) = i.next() {
                                RtcpFbNack::App(Some(app_param.to_string()))
                            } else {
                                RtcpFbNack::App(None)
                            }
                        }
                        "ecn" => RtcpFbNack::Ecn,
                        other => RtcpFbNack::Other(other.to_string()),
                    };
                    RtcpFbVal::Nack(Some(nack_val))
                } else {
                    RtcpFbVal::Nack(None)
                }
            }
            "trr-int" => {
                if let Some(val) = i.next() {
                    let Ok(i) = val.parse::<u64>() else {
                        return Err(AttributeError::InvalidParamValue {
                            param: "Minimum interval between RTCP packets (trr-int)".to_string(),
                            val: val.to_string(),
                            attr: <Self as TypedAttribute>::NAME.to_string(),
                        });
                    };
                    RtcpFbVal::TrrInt(i)
                } else {
                    return Err(AttributeError::Other {
                        error: "Minimum interval between RTCP packets (trr-int) not specified"
                            .to_string(),
                        attr: <Self as TypedAttribute>::NAME.to_string(),
                    });
                }
            }
            "ccm" => {
                if let Some(ccm_val) = i.next() {
                    let ccm_val = match ccm_val {
                        "fir" => RtcpFbCcm::Fir,
                        "tmmbr" => {
                            if let Some(tmmbr_val) = i.next() {
                                RtcpFbCcm::Tmmbr(Some(tmmbr_val.to_string()))
                            } else {
                                RtcpFbCcm::Tmmbr(None)
                            }
                        }
                        "tstr" => RtcpFbCcm::Tstr,
                        "vbcm" => {
                            let mut v = vec![];
                            for vbcm_val in i {
                                let Ok(p) = vbcm_val.parse::<u8>() else {
                                    return Err(AttributeError::InvalidParamValue {
                                        param: "Video backchannel messages (vbcm)".to_string(),
                                        val: vbcm_val.to_string(),
                                        attr: <Self as TypedAttribute>::NAME.to_string(),
                                    });
                                };
                                v.push(p);
                            }
                            RtcpFbCcm::Vbcm(v)
                        }
                        other => RtcpFbCcm::Other(other.to_string()),
                    };
                    RtcpFbVal::Ccm(ccm_val)
                } else {
                    return Err(AttributeError::ParamNotFound {
                        param: "Codec control messages (ccm)".to_string(),
                        attr: <Self as TypedAttribute>::NAME.to_string(),
                    });
                }
            }
            "transport-cc" => RtcpFbVal::TransportCc,
            other => RtcpFbVal::Other(other.to_string()),
        };

        Ok(Self {
            pt,
            val: rtcp_fb_val,
        })
    }
}

impl Display for RtcpFb {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self.pt {
            RtcpFbPt::Wildcard => f.write_char('*')?,
            RtcpFbPt::Fmt(pt) => write!(f, "{pt}")?,
        }

        f.write_char(' ')?;
        write!(f, "{}", self.val)
    }
}

impl TypedAttribute for RtcpFb {
    const NAME: &'static str = "rtcp-fb";
}

/// Media Direction Attributes
///
/// See [RFC 8866 Section 6.7](https://datatracker.ietf.org/doc/html/rfc8866#section-6.7)
#[derive(Debug, Default, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub enum Direction {
    #[default]
    SendRecv,
    SendOnly,
    RecvOnly,
    Inactive,
}

impl Direction {
    pub fn as_str(&self) -> &'static str {
        match self {
            Self::SendOnly => "sendonly",
            Self::RecvOnly => "recvonly",
            Self::SendRecv => "sendrecv",
            Self::Inactive => "inactive",
        }
    }

    pub fn has_send(self) -> bool {
        matches!(self, Self::SendRecv | Self::SendOnly)
    }

    pub fn has_recv(self) -> bool {
        matches!(self, Self::SendRecv | Self::RecvOnly)
    }

    pub fn reverse(self) -> Self {
        match self {
            Self::SendRecv => Self::SendRecv,
            Self::SendOnly => Self::RecvOnly,
            Self::RecvOnly => Self::SendOnly,
            Self::Inactive => Self::Inactive,
        }
    }

    pub fn intersect_with_remote(self, remote: Self) -> Self {
        match (self, remote) {
            (Self::Inactive, _)
            | (_, Self::Inactive)
            | (Self::RecvOnly, Self::RecvOnly)
            | (Self::SendOnly, Self::SendOnly) => Self::Inactive,
            (Self::SendRecv, Self::SendRecv) => Self::SendRecv,
            (Self::SendOnly, Self::RecvOnly | Self::SendRecv)
            | (Self::SendRecv, Self::RecvOnly) => Self::SendOnly,
            (Self::RecvOnly, Self::SendRecv | Self::SendOnly)
            | (Self::SendRecv, Self::SendOnly) => Self::RecvOnly,
        }
    }
}

impl FromStr for Direction {
    type Err = ParseEnumError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        if "sendonly".eq_ignore_ascii_case(s) {
            Ok(Direction::SendOnly)
        } else if "recvonly".eq_ignore_ascii_case(s) {
            Ok(Direction::RecvOnly)
        } else if "sendrecv".eq_ignore_ascii_case(s) {
            Ok(Direction::SendRecv)
        } else if "inactive".eq_ignore_ascii_case(s) {
            Ok(Direction::Inactive)
        } else {
            Err(ParseEnumError::Invalid(s.to_string()))
        }
    }
}

impl Display for Direction {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.write_str(self.as_str())
    }
}

impl From<Direction> for Attribute {
    fn from(attr: Direction) -> Attribute {
        Attribute {
            attribute: attr.to_string(),
            value: None,
        }
    }
}

/// RTP header extensions map
///
/// See [RFC 8285 Section 8](https://datatracker.ietf.org/doc/html/rfc8285#section-8)
#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct ExtMap {
    /// The local identifier (ID) of this extension
    pub id: u8,
    /// Direction
    pub direction: Option<Direction>,
    /// The format and meaning of the extension
    pub uri: String,
    /// Extension attributes
    pub attributes: Option<String>,
}

impl ExtMap {
    pub fn new(id: u8, uri: impl ToString) -> Self {
        ExtMap {
            id,
            direction: None,
            uri: uri.to_string(),
            attributes: None,
        }
    }

    pub fn builder(id: u8, uri: impl ToString) -> builders::ExtMap {
        builders::ExtMap::new(id, uri)
    }

    pub fn with_direction(id: u8, direction: Direction, uri: impl ToString) -> Self {
        ExtMap {
            id,
            direction: Some(direction),
            uri: uri.to_string(),
            attributes: None,
        }
    }

    pub fn with_direction_and_attributes(
        id: u8,
        direction: Direction,
        uri: impl ToString,
        attributes: impl ToString,
    ) -> Self {
        ExtMap {
            id,
            direction: Some(direction),
            uri: uri.to_string(),
            attributes: Some(attributes.to_string()),
        }
    }

    pub fn set_direction(&mut self, direction: Direction) {
        self.direction = Some(direction);
    }

    pub fn set_attributes(&mut self, attributes: impl ToString) {
        self.attributes = Some(attributes.to_string());
    }
}

impl FromStr for ExtMap {
    type Err = AttributeError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        let mut i = s.splitn(3, ' ');

        let Some(id_direction) = i.next() else {
            return Err(AttributeError::ParamNotFound {
                param: "id/direction".to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        };

        let mut d = id_direction.split('/');

        let Some(id) = d.next() else {
            return Err(AttributeError::ParamNotFound {
                param: "id".to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        };

        let direction = if let Some(d) = d.next() {
            let Ok(dir) = Direction::from_str(d) else {
                return Err(AttributeError::InvalidParamValue {
                    param: "Direction".to_string(),
                    val: d.to_string(),
                    attr: <Self as TypedAttribute>::NAME.to_string(),
                });
            };
            Some(dir)
        } else {
            None
        };

        let Ok(id) = id.parse::<u8>() else {
            return Err(AttributeError::InvalidParamValue {
                param: "Id".to_string(),
                val: id.to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        };

        if id == 0 {
            return Err(AttributeError::InvalidParamValue {
                param: "Id".to_string(),
                val: id.to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        }

        let Some(uri) = i.next() else {
            return Err(AttributeError::ParamNotFound {
                param: "URI".to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        };

        let attributes = i.next().map(|attr| attr.to_string());

        Ok(Self {
            id,
            direction,
            uri: uri.to_string(),
            attributes,
        })
    }
}

impl Display for ExtMap {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{}", self.id)?;
        if let Some(direction) = &self.direction {
            f.write_char('/')?;
            f.write_str(direction.as_str())?;
        }

        f.write_char(' ')?;
        f.write_str(&self.uri)?;

        if let Some(attr) = &self.attributes {
            f.write_char(' ')?;
            f.write_str(attr.as_str())?;
        }
        Ok(())
    }
}

impl TypedAttribute for ExtMap {
    const NAME: &'static str = "extmap";
}

/// Fingerprint Attribute
///
/// See [RFC 8122 Section 5](https://datatracker.ietf.org/doc/html/rfc8122#section-5)
#[derive(Debug, Clone, PartialEq, Eq)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct Fingerprint {
    /// Name of hash function used
    pub hash_func: HashFunc,
    /// Hash value
    pub fingerprint: Vec<u8>,
}

impl Fingerprint {
    pub fn new(hash_func: HashFunc) -> Self {
        Fingerprint {
            hash_func,
            fingerprint: vec![],
        }
    }

    pub fn with_fingerprint(
        hash_func: HashFunc,
        fingerprint: impl IntoIterator<Item = u8>,
    ) -> Self {
        Fingerprint {
            hash_func,
            fingerprint: std::iter::FromIterator::from_iter(fingerprint),
        }
    }

    pub fn set_fingerprint(&mut self, fingerprint: impl IntoIterator<Item = u8>) {
        self.fingerprint.clear();
        self.fingerprint.extend(fingerprint);
    }
}

impl FromStr for Fingerprint {
    type Err = AttributeError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        let mut i = s.splitn(2, ' ');

        let hash_func = if let Some(hash_func) = i.next() {
            HashFunc::new(hash_func)
        } else {
            return Err(AttributeError::ParamNotFound {
                param: "Hash function".to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        };

        let mut fingerprint: Vec<u8> = vec![];
        if let Some(fp) = i.next() {
            for f in fp.split(':') {
                let Ok(mut f) = hex::decode(f) else {
                    return Err(AttributeError::InvalidParamValue {
                        param: "Fingerprint value".to_string(),
                        val: f.to_string(),
                        attr: <Self as TypedAttribute>::NAME.to_string(),
                    });
                };

                fingerprint.append(&mut f);
            }
        } else {
            return Err(AttributeError::ParamNotFound {
                param: "Hash value".to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        };

        Ok(Self {
            hash_func,
            fingerprint,
        })
    }
}

impl Display for Fingerprint {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.write_str(self.hash_func.as_str())?;
        let mut first = true;
        for v in &self.fingerprint {
            if first {
                f.write_char(' ')?;
                first = false;
            } else {
                f.write_char(':')?;
            }
            write!(f, "{v:02X}")?;
        }
        Ok(())
    }
}

impl TypedAttribute for Fingerprint {
    const NAME: &'static str = "fingerprint";
}

/// Group Attribute
///
/// See [RFC 5888 Section 5](https://datatracker.ietf.org/doc/html/rfc5888#section-5)
#[derive(Debug, Clone, PartialEq, Eq)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct Group {
    pub semantics: GroupSemantics,
    pub mid_tags: Vec<String>,
}

impl Group {
    pub fn new(semantics: GroupSemantics) -> Self {
        Group {
            semantics,
            mid_tags: vec![],
        }
    }

    pub fn add_mid_tag(&mut self, mid_tag: impl ToString) {
        self.mid_tags.push(mid_tag.to_string())
    }

    pub fn add_mid_tags(&mut self, mid_tags: impl IntoIterator<Item = impl ToString>) {
        self.mid_tags
            .extend(mid_tags.into_iter().map(|i| i.to_string()))
    }
}

impl FromStr for Group {
    type Err = AttributeError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        let mut i = s.split(' ');

        let Some(semantics) = i.next() else {
            return Err(AttributeError::ParamNotFound {
                param: "Semantics".to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        };

        let semantics = GroupSemantics::new(semantics);

        let mut mid_tags = vec![];
        for mid in i {
            mid_tags.push(mid.to_string());
        }

        if mid_tags.is_empty() {
            return Err(AttributeError::ParamNotFound {
                param: "Media identification tags".to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        }

        Ok(Self {
            semantics,
            mid_tags,
        })
    }
}

impl Display for Group {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.write_str(self.semantics.as_str())?;
        for m in &self.mid_tags {
            f.write_char(' ')?;
            f.write_str(m)?;
        }
        Ok(())
    }
}

impl TypedAttribute for Group {
    const NAME: &'static str = "group";
}

/// Setup attribute for the session or media.
///
/// See [RFC 4145 Section 4](https://datatracker.ietf.org/doc/html/rfc4145#section-4) for more details.
#[derive(Debug, Clone, PartialEq, Eq)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub enum Setup {
    /// Initiator of the connection.
    Active,
    /// Acceptor of the connection.
    Passive,
    /// Act as either initiator or acceptor of the connection.
    ActPass,
    /// Do not establish a connection.
    HoldConn,
}

impl FromStr for Setup {
    type Err = AttributeError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        if "active".eq_ignore_ascii_case(s) {
            Ok(Setup::Active)
        } else if "passive".eq_ignore_ascii_case(s) {
            Ok(Setup::Passive)
        } else if "actpass".eq_ignore_ascii_case(s) {
            Ok(Setup::ActPass)
        } else if "holdconn".eq_ignore_ascii_case(s) {
            Ok(Setup::HoldConn)
        } else {
            Err(AttributeError::Other {
                error: format!("Invalid Setup value {s}"),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            })
        }
    }
}

impl Display for Setup {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        let s = match self {
            Setup::Active => "active",
            Setup::Passive => "passive",
            Setup::ActPass => "actpass",
            Setup::HoldConn => "holdconn",
        };
        f.write_str(s)
    }
}

impl TypedAttribute for Setup {
    const NAME: &'static str = "setup";
}

/// SSRC media attribute.
///
/// See [RFC 5576 Section 4.1](https://datatracker.ietf.org/doc/html/rfc5576#section-4.1)
#[derive(Debug, Clone, PartialEq, Eq)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct Ssrc {
    pub ssrc_id: u32,
    pub attribute: SsrcAttribute,
    pub value: Option<String>,
}

impl Ssrc {
    pub fn new(ssrc_id: u32, attribute: SsrcAttribute) -> Self {
        Ssrc {
            ssrc_id,
            attribute,
            value: None,
        }
    }

    pub fn with_typed_attribute(ssrc_id: u32, attribute: impl TypedAttribute) -> Self {
        let value = attribute.to_string();
        Ssrc {
            ssrc_id,
            attribute: SsrcAttribute::from(attribute),
            value: Some(value),
        }
    }

    pub fn with_value(ssrc_id: u32, attribute: SsrcAttribute, value: impl ToString) -> Self {
        Ssrc {
            ssrc_id,
            attribute,
            value: Some(value.to_string()),
        }
    }

    pub fn set_value(&mut self, value: impl ToString) {
        self.value = Some(value.to_string());
    }

    /// Gets the inner attribute as a `TypedAttribute`.
    ///
    /// # Errors
    ///
    /// * `AttributeError::Other` if the inner attribute doesn't match
    ///   the specified `TypedAttribute` or if the value is empty.
    /// * a specific `AttributeError` if the typed attribute couldn't be built.
    pub fn get_typed<T: TypedAttribute>(&self) -> Result<T, AttributeError> {
        if !self.attribute.as_str().eq_ignore_ascii_case(T::NAME) {
            return Err(AttributeError::Other {
                error: format!("Attribute type mismatch (requested {})", T::NAME),
                attr: self.attribute.as_str().to_string(),
            });
        }

        // Property attributes have no value; they parse the empty string,
        // consistent with Session::attributes_typed().
        T::from_str(self.value.as_deref().unwrap_or_default())
    }
}

impl FromStr for Ssrc {
    type Err = AttributeError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        let Some((ssrc_id_str, rest)) = s.split_once(' ') else {
            return Err(AttributeError::ParamNotFound {
                param: "Ssrc id".to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        };

        let Ok(ssrc_id) = ssrc_id_str.parse::<u32>() else {
            return Err(AttributeError::InvalidParamValue {
                param: "Ssrc id".to_string(),
                val: ssrc_id_str.to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        };

        let (attr, value) = if let Some((attr_str, value)) = rest.split_once(':') {
            (attr_str, Some(value.to_string()))
        } else {
            (rest, None)
        };

        Ok(Self {
            ssrc_id,
            attribute: SsrcAttribute::new(attr),
            value,
        })
    }
}

impl Display for Ssrc {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        use crate::{Fmtp, MediaClockSource, ReferenceClock, Rtcp};

        let attr_str = match &self.attribute {
            SsrcAttribute::Cname => "cname",
            SsrcAttribute::PreviousSsrc => "previous-ssrc",
            SsrcAttribute::Fmtp => <Fmtp as TypedAttribute>::NAME,
            SsrcAttribute::Rtcp => <Rtcp as TypedAttribute>::NAME,
            SsrcAttribute::ReferenceClock => <ReferenceClock as TypedAttribute>::NAME,
            SsrcAttribute::MediaClockSource => <MediaClockSource as TypedAttribute>::NAME,
            SsrcAttribute::Other(other) => other.as_str(),
        };
        write!(f, "{} {attr_str}", self.ssrc_id)?;

        if let Some(value) = &self.value {
            f.write_char(':')?;
            f.write_str(value)?;
        }

        Ok(())
    }
}

impl TypedAttribute for Ssrc {
    const NAME: &'static str = "ssrc";
}

/// SSRC group attribute
///
/// See [RFC 5576 Section 4.2](https://datatracker.ietf.org/doc/html/rfc5576#section-4.2)
#[derive(Debug, Clone, PartialEq, Eq)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct SsrcGroup {
    pub semantics: GroupSemantics,
    pub ssrc_ids: Vec<u32>,
}

impl SsrcGroup {
    pub fn new(semantics: GroupSemantics) -> Self {
        SsrcGroup {
            semantics,
            ssrc_ids: vec![],
        }
    }

    pub fn add_ssrc_id(&mut self, ssrc_id: u32) {
        self.ssrc_ids.push(ssrc_id)
    }

    pub fn add_ssrc_ids(&mut self, ssrc_ids: impl IntoIterator<Item = u32>) {
        self.ssrc_ids.extend(ssrc_ids)
    }
}

impl FromStr for SsrcGroup {
    type Err = AttributeError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        let mut i = s.split(' ');

        let Some(semantics) = i.next() else {
            return Err(AttributeError::ParamNotFound {
                param: "Semantics".to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        };

        let semantics = if "FEC".eq_ignore_ascii_case(semantics) {
            GroupSemantics::FEC
        } else if "FID".eq_ignore_ascii_case(semantics) {
            GroupSemantics::FID
        } else {
            // The initial defined semantics for ssrc-group attribute are FID and FEC
            // The other registered group semantics are not useful for source grouping
            // But keep this open for any other new semantics that are not part of GroupSemantics
            GroupSemantics::Other(semantics.to_string())
        };

        let mut ssrc_ids = vec![];
        for ssrc_id in i {
            let Ok(ssrc_id) = ssrc_id.parse::<u32>() else {
                return Err(AttributeError::InvalidParamValue {
                    param: "Ssrc id".to_string(),
                    val: ssrc_id.to_string(),
                    attr: <Self as TypedAttribute>::NAME.to_string(),
                });
            };
            ssrc_ids.push(ssrc_id);
        }

        if ssrc_ids.is_empty() {
            return Err(AttributeError::ParamNotFound {
                param: "ssrc_id".to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        }

        Ok(Self {
            semantics,
            ssrc_ids,
        })
    }
}

impl Display for SsrcGroup {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        let sem = match &self.semantics {
            GroupSemantics::FEC => "FEC",
            GroupSemantics::FID => "FID",
            // Semantics other than FEC and FID are not useful for source grouping but still displaying
            // them for debugging purpose
            GroupSemantics::LS => "LS",
            GroupSemantics::SRF => "SRF",
            GroupSemantics::ANAT => "ANAT",
            GroupSemantics::DDP => "DDP",
            GroupSemantics::Other(s) => s.as_str(),
        };

        f.write_str(sem)?;
        for ssrc_id in &self.ssrc_ids {
            f.write_char(' ')?;
            write!(f, "{ssrc_id}")?;
        }

        Ok(())
    }
}

impl TypedAttribute for SsrcGroup {
    const NAME: &'static str = "ssrc-group";
}

/// SRTP Key parameter
///
/// See [RFC 4568 Section 6.1](https://datatracker.ietf.org/doc/html/rfc4568#section-6.1)
#[derive(Debug, PartialEq, Eq, Clone)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct SrtpKeyParam {
    /// Concatenated key and salt, base64 encoded
    pub key_and_salt: String,
    /// Master key lifetime (max number of SRTP or SRTCP packets using this master key)
    ///
    /// The value must not exceed 2^48 (RFC 4568, section 8.1).
    pub lifetime: Option<u64>,
    /// MKI (Master Key Identifier) and length of the MKI field in SRTP packets
    pub mki_and_length: Option<(u32, u32)>,
}

impl SrtpKeyParam {
    pub fn new(key_and_salt: impl ToString) -> Self {
        SrtpKeyParam {
            key_and_salt: key_and_salt.to_string(),
            lifetime: None,
            mki_and_length: None,
        }
    }

    pub fn with_lifetime(key_and_salt: impl ToString, lifetime: u64) -> Self {
        SrtpKeyParam {
            key_and_salt: key_and_salt.to_string(),
            lifetime: Some(lifetime),
            mki_and_length: None,
        }
    }

    pub fn with_lifetime_and_mki_and_length(
        key_and_salt: impl ToString,
        lifetime: u64,
        mki: u32,
        length: u32,
    ) -> Self {
        SrtpKeyParam {
            key_and_salt: key_and_salt.to_string(),
            lifetime: Some(lifetime),
            mki_and_length: Some((mki, length)),
        }
    }

    pub fn set_lifetime(&mut self, lifetime: u64) {
        self.lifetime = Some(lifetime);
    }

    pub fn set_mki_and_length(&mut self, mki: u32, length: u32) {
        self.mki_and_length = Some((mki, length));
    }
}

// Parse a plain decimal integer as used in the crypto attribute: digits
// only, no sign and no leading zeroes, except for the value 0 itself
// (RFC 4568, section 8.1).
fn parse_decimal_no_leading_zeroes(s: &str) -> Option<u64> {
    if s.is_empty() || !s.bytes().all(|b| b.is_ascii_digit()) {
        return None;
    }
    if s.len() > 1 && s.starts_with('0') {
        return None;
    }
    s.parse().ok()
}

impl FromStr for SrtpKeyParam {
    type Err = AttributeError;
    fn from_str(key_param: &str) -> Result<Self, Self::Err> {
        let mut k = key_param.split('|');

        let Some(key_and_salt_with_method) = k.next() else {
            return Err(AttributeError::ParamNotFound {
                param: "Srtp Key and Salt".to_string(),
                attr: Crypto::NAME.to_string(),
            });
        };

        let key_and_salt = if key_and_salt_with_method
            .get(..7)
            .is_some_and(|p| p.eq_ignore_ascii_case("inline:"))
        {
            &key_and_salt_with_method[7..]
        } else {
            return Err(AttributeError::InvalidParamValue {
                param: "Srtp Key and Salt".to_string(),
                val: key_and_salt_with_method.to_string(),
                attr: Crypto::NAME.to_string(),
            });
        };

        let (lifetime, mki_and_length) = if let Some(next_param) = k.next() {
            match next_param.split_once(':') {
                Some(mki_and_length) => {
                    // lifetime is not specified, but only MKI and its length
                    let Ok(mki) = mki_and_length.0.parse::<u32>() else {
                        return Err(AttributeError::InvalidParamValue {
                            param: "MKI".to_string(),
                            val: next_param.to_string(),
                            attr: Crypto::NAME.to_string(),
                        });
                    };

                    let Ok(len) = mki_and_length.1.parse::<u32>() else {
                        return Err(AttributeError::InvalidParamValue {
                            param: "Length".to_string(),
                            val: next_param.to_string(),
                            attr: Crypto::NAME.to_string(),
                        });
                    };
                    (None, Some((mki, len)))
                }
                None => {
                    // lifetime is specified
                    // The maximum master key lifetime is 2^48 packets for all
                    // crypto suites (RFC 4568, section 8.1).
                    const MAX_LIFETIME: u64 = 1 << 48;
                    let lifetime = match next_param.strip_prefix("2^") {
                        Some(exp) => {
                            let Some(exp) = parse_decimal_no_leading_zeroes(exp)
                                .and_then(|exp| u32::try_from(exp).ok())
                            else {
                                return Err(AttributeError::InvalidParamValue {
                                    param: "Lifetime".to_string(),
                                    val: next_param.to_string(),
                                    attr: Crypto::NAME.to_string(),
                                });
                            };
                            let Some(lifetime) = 1u64.checked_shl(exp) else {
                                return Err(AttributeError::InvalidParamValue {
                                    param: "Lifetime".to_string(),
                                    val: next_param.to_string(),
                                    attr: Crypto::NAME.to_string(),
                                });
                            };
                            // 1u64.checked_shl() never returns zero
                            if lifetime > MAX_LIFETIME {
                                return Err(AttributeError::InvalidParamValue {
                                    param: "Lifetime".to_string(),
                                    val: next_param.to_string(),
                                    attr: Crypto::NAME.to_string(),
                                });
                            }
                            Some(lifetime)
                        }
                        None => {
                            let Some(lifetime) = parse_decimal_no_leading_zeroes(next_param) else {
                                return Err(AttributeError::InvalidParamValue {
                                    param: "Lifetime".to_string(),
                                    val: next_param.to_string(),
                                    attr: Crypto::NAME.to_string(),
                                });
                            };
                            if lifetime == 0 || lifetime > MAX_LIFETIME {
                                return Err(AttributeError::InvalidParamValue {
                                    param: "Lifetime".to_string(),
                                    val: next_param.to_string(),
                                    attr: Crypto::NAME.to_string(),
                                });
                            }
                            Some(lifetime)
                        }
                    };

                    // now parse the MKI and length
                    let mki_and_length = if let Some(m) = k.next() {
                        if let Some(p) = m.split_once(':') {
                            let Ok(mki) = p.0.parse::<u32>() else {
                                return Err(AttributeError::InvalidParamValue {
                                    param: "MKI".to_string(),
                                    val: m.to_string(),
                                    attr: Crypto::NAME.to_string(),
                                });
                            };

                            let Ok(len) = p.1.parse::<u32>() else {
                                return Err(AttributeError::InvalidParamValue {
                                    param: "Length".to_string(),
                                    val: m.to_string(),
                                    attr: Crypto::NAME.to_string(),
                                });
                            };
                            Some((mki, len))
                        } else {
                            return Err(AttributeError::ParamNotFound {
                                param: "MKI and Length".to_string(),
                                attr: Crypto::NAME.to_string(),
                            });
                        }
                    } else {
                        None
                    };

                    (lifetime, mki_and_length)
                }
            }
        } else {
            (None, None)
        };

        if let Some((_, len)) = mki_and_length {
            if !(1..=128).contains(&len) {
                return Err(AttributeError::InvalidParamValue {
                    param: "MKI length".to_string(),
                    val: len.to_string(),
                    attr: Crypto::NAME.to_string(),
                });
            }
        }

        if let Some(unexpected) = k.next() {
            return Err(AttributeError::UnexpectedTrailingItem {
                val: unexpected.to_string(),
                attr: Crypto::NAME.to_string(),
            });
        }

        Ok(Self {
            key_and_salt: key_and_salt.to_string(),
            lifetime,
            mki_and_length,
        })
    }
}

impl Display for SrtpKeyParam {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "inline:{}", self.key_and_salt)?;
        if let Some(lifetime) = self.lifetime {
            if lifetime.is_power_of_two() {
                write!(f, "|2^{}", lifetime.trailing_zeros())?;
            } else {
                write!(f, "|{lifetime}")?;
            }
        }
        if let Some((mki, length)) = self.mki_and_length {
            write!(f, "|{mki}:{length}")?;
        }
        Ok(())
    }
}

/// Cryptographic information for the media
///
/// See [RFC 4568 Section 4](https://datatracker.ietf.org/doc/html/rfc4568#section-4)
#[derive(Debug, PartialEq, Eq, Clone)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct Crypto {
    pub tag: u32,
    pub crypto_suite: CryptoSuite,
    pub key_params: Vec<SrtpKeyParam>,
    pub session_params: Vec<SrtpSessionParam>,
}

impl Crypto {
    pub fn new(tag: u32, crypto_suite: CryptoSuite) -> Self {
        Crypto {
            tag,
            crypto_suite,
            key_params: vec![],
            session_params: vec![],
        }
    }

    pub fn add_key_param(&mut self, key_param: SrtpKeyParam) {
        self.key_params.push(key_param)
    }

    pub fn add_key_params(&mut self, key_params: impl IntoIterator<Item = SrtpKeyParam>) {
        self.key_params.extend(key_params)
    }

    pub fn add_session_param(&mut self, session_param: SrtpSessionParam) {
        self.session_params.push(session_param)
    }

    pub fn add_session_params(
        &mut self,
        session_params: impl IntoIterator<Item = SrtpSessionParam>,
    ) {
        self.session_params.extend(session_params)
    }
}

impl FromStr for Crypto {
    type Err = AttributeError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        let mut i = s.split(' ');

        let Some(tag) = i.next() else {
            return Err(AttributeError::ParamNotFound {
                param: "Tag".to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        };

        let Ok(tag) = tag.parse::<u32>() else {
            return Err(AttributeError::InvalidParamValue {
                param: "Tag".to_string(),
                val: tag.to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        };

        let Some(crypto_suite) = i.next() else {
            return Err(AttributeError::ParamNotFound {
                param: "CryptoSuite".to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        };

        let crypto_suite = CryptoSuite::new(crypto_suite);

        let Some(key_params_str) = i.next() else {
            return Err(AttributeError::ParamNotFound {
                param: "Key params".to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        };

        let mut key_params: Vec<SrtpKeyParam> = Vec::new();

        for key_param in key_params_str.split(';') {
            let key_param = SrtpKeyParam::from_str(key_param)?;
            key_params.push(key_param);
        }

        let mut session_params: Vec<SrtpSessionParam> = Vec::new();
        for s in &mut i {
            let param = if s.get(..4).is_some_and(|p| p.eq_ignore_ascii_case("KDR=")) {
                let kdr_val = &s[4..];
                let Ok(kdr_val) = kdr_val.parse::<u8>() else {
                    return Err(AttributeError::InvalidParamValue {
                        param: "KDR".to_string(),
                        val: kdr_val.to_string(),
                        attr: <Self as TypedAttribute>::NAME.to_string(),
                    });
                };

                // Note: the range for KDR value is conflicting in the spec,
                // rfc4568#section-6.3.1 says the range should be 1,2,...24 and
                // the grammar in rfc4568#section-9.2 says it should be 0..24.
                // So using the bigger range i.e., 0..24 for now
                if !(0..=24).contains(&kdr_val) {
                    return Err(AttributeError::InvalidParamValue {
                        param: "KDR".to_string(),
                        val: format!("{kdr_val}(expected range 0..24)"),
                        attr: <Self as TypedAttribute>::NAME.to_string(),
                    });
                }
                SrtpSessionParam::Kdr(kdr_val)
            } else if s.eq_ignore_ascii_case("UNENCRYPTED_SRTCP") {
                SrtpSessionParam::UnencryptedSrtcp
            } else if s.eq_ignore_ascii_case("UNENCRYPTED_SRTP") {
                SrtpSessionParam::UnencryptedSrtp
            } else if s.eq_ignore_ascii_case("UNAUTHENTICATED_SRTP") {
                SrtpSessionParam::UnauthenticatedSrtp
            } else if s
                .get(..10)
                .is_some_and(|p| p.eq_ignore_ascii_case("FEC_ORDER="))
            {
                let fec_ord = &s[10..];
                if fec_ord.eq_ignore_ascii_case("FEC_SRTP") {
                    SrtpSessionParam::FecOrder(FecOrder::FecSrtp)
                } else if fec_ord.eq_ignore_ascii_case("SRTP_FEC") {
                    SrtpSessionParam::FecOrder(FecOrder::SrtpFec)
                } else {
                    return Err(AttributeError::InvalidParamValue {
                        param: "FEC order".to_string(),
                        val: s.to_string(),
                        attr: <Self as TypedAttribute>::NAME.to_string(),
                    });
                }
            } else if s
                .get(..8)
                .is_some_and(|p| p.eq_ignore_ascii_case("FEC_KEY="))
            {
                let key_params_str = &s[8..];
                let mut key_params: Vec<SrtpKeyParam> = Vec::new();

                for key_param in key_params_str.split(';') {
                    let key_param = SrtpKeyParam::from_str(key_param)?;
                    key_params.push(key_param);
                }
                SrtpSessionParam::FecKey(key_params)
            } else if s.get(..4).is_some_and(|p| p.eq_ignore_ascii_case("WSH=")) {
                let wsh_val = &s[4..];
                let Ok(wsh_val) = wsh_val.parse::<u8>() else {
                    return Err(AttributeError::InvalidParamValue {
                        param: "WSH".to_string(),
                        val: wsh_val.to_string(),
                        attr: <Self as TypedAttribute>::NAME.to_string(),
                    });
                };

                if wsh_val < 64 {
                    return Err(AttributeError::InvalidParamValue {
                        param: "WSH".to_string(),
                        val: wsh_val.to_string(),
                        attr: <Self as TypedAttribute>::NAME.to_string(),
                    });
                }
                SrtpSessionParam::Wsh(wsh_val)
            } else {
                // Extension
                SrtpSessionParam::Extension(s.to_string())
            };
            session_params.push(param);
        }

        Ok(Self {
            tag,
            key_params,
            crypto_suite,
            session_params,
        })
    }
}

impl Display for Crypto {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{} {}", self.tag, self.crypto_suite.as_str())?;

        for (i, key_param) in self.key_params.iter().enumerate() {
            if i == 0 {
                f.write_char(' ')?;
            } else {
                f.write_char(';')?;
            }

            write!(f, "{}", key_param)?;
        }

        for session_param in &self.session_params {
            match session_param {
                SrtpSessionParam::Kdr(kdr) => write!(f, " KDR={kdr}")?,
                SrtpSessionParam::UnencryptedSrtp => write!(f, " UNENCRYPTED_SRTP")?,
                SrtpSessionParam::UnencryptedSrtcp => write!(f, " UNENCRYPTED_SRTCP")?,
                SrtpSessionParam::UnauthenticatedSrtp => write!(f, " UNAUTHENTICATED_SRTP")?,
                SrtpSessionParam::FecOrder(fec_order) => {
                    let order = match fec_order {
                        FecOrder::FecSrtp => "FEC_SRTP",
                        FecOrder::SrtpFec => "SRTP_FEC",
                    };
                    write!(f, " FEC_ORDER={order}")?;
                }
                SrtpSessionParam::FecKey(srtp_key_params) => {
                    write!(f, " FEC_KEY")?;
                    for (i, key_param) in srtp_key_params.iter().enumerate() {
                        if i == 0 {
                            f.write_char('=')?;
                        } else {
                            f.write_char(';')?;
                        }

                        write!(f, "{}", key_param)?;
                    }
                }
                SrtpSessionParam::Wsh(wsh) => write!(f, " WSH={wsh}")?,
                SrtpSessionParam::Extension(extn) => {
                    f.write_char(' ')?;
                    f.write_str(extn)?;
                }
            }
        }
        Ok(())
    }
}

impl TypedAttribute for Crypto {
    const NAME: &'static str = "crypto";
}

/// ICE Candidate attribute of the media
///
/// See [RFC 8839 Section 5.1](https://datatracker.ietf.org/doc/html/rfc8839#section-5.1)
#[derive(Debug, PartialEq, Eq, Clone)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct Candidate {
    /// Arbitrary string used in the freezing algorithm to group similar candidates
    /// See [RFC 8445 Section 5.1.1.3](https://datatracker.ietf.org/doc/html/rfc8445#section-5.1.1.3)
    pub foundation: String,
    /// Identifies the specific component of the data stream
    /// 1 for RTP and 2 for RTCP
    pub component_id: u32,
    /// Transport protocol of the candidate
    pub transport: String,
    /// Candidate's priority
    pub priority: u64,
    /// IP address of the candidate
    /// IPv4, IPv6 addresses and FQDN allowed
    pub address: CandidateAddress,
    /// Port of the candidate
    pub port: u16,
    /// Type of the candidate
    pub typ: CandidateType,
    /// Address related to the candidate
    /// Required for srflx, prflx and relay type candidates
    pub rel_addr: Option<IpAddr>,
    /// Port related to the candidate
    /// Required for srflx, prflx and relay type candidates
    pub rel_port: Option<u16>,
    /// Extensions
    pub extensions: Vec<(String, String)>,
}

impl Candidate {
    pub fn new(
        foundation: impl ToString,
        component_id: u32,
        transport: impl ToString,
        priority: u64,
        address: CandidateAddress,
        port: u16,
        typ: CandidateType,
    ) -> Self {
        Candidate {
            foundation: foundation.to_string(),
            component_id,
            transport: transport.to_string(),
            priority,
            address,
            port,
            typ,
            rel_addr: None,
            rel_port: None,
            extensions: vec![],
        }
    }

    #[allow(clippy::too_many_arguments)]
    pub fn with_rel_addr(
        foundation: impl ToString,
        component_id: u32,
        transport: impl ToString,
        priority: u64,
        address: CandidateAddress,
        port: u16,
        typ: CandidateType,
        rel_addr: impl Into<IpAddr>,
    ) -> Self {
        Candidate {
            foundation: foundation.to_string(),
            component_id,
            transport: transport.to_string(),
            priority,
            address,
            port,
            typ,
            rel_addr: Some(rel_addr.into()),
            rel_port: None,
            extensions: vec![],
        }
    }

    #[allow(clippy::too_many_arguments)]
    pub fn with_rel_addr_and_port(
        foundation: impl ToString,
        component_id: u32,
        transport: impl ToString,
        priority: u64,
        address: CandidateAddress,
        port: u16,
        typ: CandidateType,
        rel_addr: impl Into<IpAddr>,
        rel_port: u16,
    ) -> Self {
        Candidate {
            foundation: foundation.to_string(),
            component_id,
            transport: transport.to_string(),
            priority,
            address,
            port,
            typ,
            rel_addr: Some(rel_addr.into()),
            rel_port: Some(rel_port),
            extensions: vec![],
        }
    }

    pub fn set_rel_addr(&mut self, rel_addr: impl Into<IpAddr>) {
        self.rel_addr = Some(rel_addr.into());
    }

    pub fn set_rel_port(&mut self, rel_port: u16) {
        self.rel_port = Some(rel_port);
    }

    pub fn add_extension(&mut self, name: impl ToString, value: impl ToString) {
        self.extensions.push((name.to_string(), value.to_string()))
    }
}

impl FromStr for Candidate {
    type Err = AttributeError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        let mut i = s.split(' ');

        let Some(foundation) = i.next() else {
            return Err(AttributeError::ParamNotFound {
                param: "Foundation".to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        };

        let Some(comp_id) = i.next() else {
            return Err(AttributeError::ParamNotFound {
                param: "Component id".to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        };

        let Ok(comp_id) = comp_id.parse::<u32>() else {
            return Err(AttributeError::InvalidParamValue {
                param: "Component id".to_string(),
                val: comp_id.to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        };

        let Some(transport) = i.next() else {
            return Err(AttributeError::ParamNotFound {
                param: "Transport".to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        };

        let Some(priority) = i.next() else {
            return Err(AttributeError::ParamNotFound {
                param: "Priority".to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        };

        let Ok(priority) = priority.parse::<u64>() else {
            return Err(AttributeError::InvalidParamValue {
                param: "Priority".to_string(),
                val: priority.to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        };

        let Some(address) = i.next() else {
            return Err(AttributeError::ParamNotFound {
                param: "Address".to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        };

        let address = match address.parse::<IpAddr>() {
            Ok(a) => CandidateAddress::IpAddr(a),
            Err(_) => CandidateAddress::FQDN(address.to_string()),
        };

        let Some(port) = i.next() else {
            return Err(AttributeError::ParamNotFound {
                param: "Port".to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        };

        let Ok(port) = port.parse::<u16>() else {
            return Err(AttributeError::InvalidParamValue {
                param: "Port".to_string(),
                val: port.to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        };

        let Some(typ_str) = i.next() else {
            return Err(AttributeError::ParamNotFound {
                param: "'typ' string".to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        };

        if !typ_str.eq_ignore_ascii_case("typ") {
            return Err(AttributeError::ParamNotFound {
                param: "'typ' string".to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        }

        let Some(cand_type) = i.next() else {
            return Err(AttributeError::ParamNotFound {
                param: "Candidate type".to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        };

        let cand_type = CandidateType::new(cand_type);

        let mut rel_addr: Option<IpAddr> = None;
        let mut rel_port: Option<u16> = None;
        let mut exts: Vec<(String, String)> = Vec::new();

        while let Some(key) = i.next() {
            if key.eq_ignore_ascii_case("raddr") {
                let Some(raddr) = i.next() else {
                    return Err(AttributeError::ParamNotFound {
                        param: "Relative address".to_string(),
                        attr: <Self as TypedAttribute>::NAME.to_string(),
                    });
                };

                if let Ok(raddr) = raddr.parse::<IpAddr>() {
                    rel_addr = Some(raddr);
                } else {
                    return Err(AttributeError::InvalidParamValue {
                        param: "Relative address".to_string(),
                        val: raddr.to_string(),
                        attr: <Self as TypedAttribute>::NAME.to_string(),
                    });
                };
            } else if key.eq_ignore_ascii_case("rport") {
                let Some(rport) = i.next() else {
                    return Err(AttributeError::ParamNotFound {
                        param: "Relative port".to_string(),
                        attr: <Self as TypedAttribute>::NAME.to_string(),
                    });
                };

                if let Ok(rport) = rport.parse::<u16>() {
                    rel_port = Some(rport);
                } else {
                    return Err(AttributeError::InvalidParamValue {
                        param: "Relative port".to_string(),
                        val: rport.to_string(),
                        attr: <Self as TypedAttribute>::NAME.to_string(),
                    });
                }
            } else {
                let Some(val) = i.next() else {
                    return Err(AttributeError::Other {
                        error: format!("No val for the extension {key}"),
                        attr: <Self as TypedAttribute>::NAME.to_string(),
                    });
                };

                exts.push((key.to_string(), val.to_string()));
            }
        }

        Ok(Self {
            foundation: foundation.to_string(),
            component_id: comp_id,
            transport: transport.to_string(),
            priority,
            address,
            port,
            typ: cand_type,
            rel_addr,
            rel_port,
            extensions: exts,
        })
    }
}

impl Display for Candidate {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        let candidate_addr = match &self.address {
            CandidateAddress::IpAddr(a) => a.to_string(),
            CandidateAddress::FQDN(d) => d.clone(),
        };
        write!(
            f,
            "{} {} {} {} {} {} typ {}",
            self.foundation,
            self.component_id,
            self.transport,
            self.priority,
            candidate_addr,
            self.port,
            self.typ.as_str(),
        )?;
        if let Some(rel_addr) = self.rel_addr {
            write!(f, " raddr {rel_addr}")?;
        }
        if let Some(rel_port) = self.rel_port {
            write!(f, " rport {rel_port}")?;
        }
        for (key, val) in &self.extensions {
            write!(f, " {key} {val}")?;
        }
        Ok(())
    }
}

impl TypedAttribute for Candidate {
    const NAME: &'static str = "candidate";
}

/// Restricted identification line (`a=rid`) attribute
///
/// Represents the send/recv restriction that defines a unique RTP payload
/// configuration, see
/// [RFC 8851 Section 4](https://datatracker.ietf.org/doc/html/rfc8851#section-4).
/// Restriction parameters (`pt=`, `max-width=`, `max-br=`, ...) are kept as raw
/// `name[=value]` tokens, in order, without interpretation. The optional `pt=`
/// payload format list is the first parameter when present.
#[derive(Debug, Clone, PartialEq, Eq)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct Rid {
    /// The restriction identifier, referenced by `a=extmap` and SDES items.
    pub id: String,
    /// Whether the restriction applies to a `send` or `recv` stream.
    pub direction: RidDirection,
    /// Restriction parameters, e.g. `pt=99,102` or `max-br=64000`.
    pub params: Vec<String>,
}

impl Rid {
    pub fn new(id: impl ToString, direction: RidDirection) -> Self {
        Rid {
            id: id.to_string(),
            direction,
            params: Vec::new(),
        }
    }

    pub fn add_param(&mut self, param: impl ToString) {
        self.params.push(param.to_string());
    }

    pub fn with_params(
        id: impl ToString,
        direction: RidDirection,
        params: impl IntoIterator<Item = impl ToString>,
    ) -> Self {
        Rid {
            id: id.to_string(),
            direction,
            params: params.into_iter().map(|p| p.to_string()).collect(),
        }
    }
}

impl FromStr for Rid {
    type Err = AttributeError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        let attr = <Self as TypedAttribute>::NAME.to_string();
        let (id, rest) = s
            .split_once(' ')
            .ok_or_else(|| AttributeError::ParamNotFound {
                param: "Direction".to_string(),
                attr: attr.clone(),
            })?;

        let id = id.trim();
        if id.is_empty() {
            return Err(AttributeError::ParamNotFound {
                param: "ID".to_string(),
                attr: attr.clone(),
            });
        }

        // RFC 8851, section 10: rid-id = 1*(alpha-numeric / "-" / "_"),
        // with alpha-numeric = ALPHA / DIGIT (RFC 8866, section 8).
        if !id
            .bytes()
            .all(|b| b.is_ascii_alphanumeric() || b == b'-' || b == b'_')
        {
            return Err(AttributeError::InvalidParamValue {
                param: "ID".to_string(),
                val: id.to_string(),
                attr,
            });
        }

        // The direction is optionally followed by a single space and the
        // restriction parameter list.
        let (direction_str, params_str) = match rest.trim().split_once(' ') {
            Some((d, p)) => (d, p),
            None => (rest.trim(), ""),
        };

        let direction = direction_str
            .parse()
            .map_err(|_| AttributeError::InvalidParamValue {
                param: "Direction".to_string(),
                val: direction_str.to_string(),
                attr: attr.clone(),
            })?;

        let params = if params_str.trim().is_empty() {
            Vec::new()
        } else {
            params_str
                .trim()
                .split(';')
                .map(|p| p.trim())
                .filter(|p| !p.is_empty())
                .map(|p| {
                    if p.contains(char::is_whitespace) {
                        Err(AttributeError::InvalidParamValue {
                            param: "Parameter".to_string(),
                            val: p.to_string(),
                            attr: attr.clone(),
                        })
                    } else {
                        Ok(p.to_string())
                    }
                })
                .collect::<Result<Vec<_>, _>>()?
        };

        Ok(Rid {
            id: id.to_string(),
            direction,
            params,
        })
    }
}

impl Display for Rid {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{} {}", self.id, self.direction)?;
        if !self.params.is_empty() {
            write!(f, " {}", self.params.join(";"))?;
        }
        Ok(())
    }
}

impl TypedAttribute for Rid {
    const NAME: &'static str = "rid";
}

/// Key management protocol of the [`KeyMgmt`] attribute.
///
/// The identifiers (KMPIDs) are case-sensitive, registered at IANA in the
/// "SDP/RTSP key management protocol identifiers" subregistry
/// ([RFC 4567 Section 9.3](https://datatracker.ietf.org/doc/html/rfc4567#section-9.3));
/// `mikey` is the only value defined so far.
#[derive(Debug, Clone, PartialEq, Eq)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub enum KeyMgmtMethod {
    /// Multimedia Internet KEYing ([RFC 3830](https://datatracker.ietf.org/doc/html/rfc3830)).
    Mikey,
    /// Any other, possibly unregistered method, kept verbatim.
    Other(String),
}

impl From<&str> for KeyMgmtMethod {
    fn from(s: &str) -> Self {
        match s {
            "mikey" => KeyMgmtMethod::Mikey,
            other => KeyMgmtMethod::Other(other.to_string()),
        }
    }
}

impl std::str::FromStr for KeyMgmtMethod {
    // FIXME use the never type when it is stable
    type Err = ();

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        Ok(s.into())
    }
}

impl Display for KeyMgmtMethod {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            KeyMgmtMethod::Mikey => f.write_str("mikey"),
            KeyMgmtMethod::Other(other) => f.write_str(other),
        }
    }
}

/// Key management attribute (`a=key-mgmt`) attribute
///
/// See [RFC 4567 Section 4.1](https://datatracker.ietf.org/doc/html/rfc4567#section-4.1).
/// The key management data is kept verbatim; for the `mikey` method it is
/// the base64-encoded MIKEY message (RFC 3830, RFC 4567 section 7).
///
/// Media-level `key-mgmt` attributes override session-level ones, which
/// consumers have to resolve themselves.
#[derive(Debug, Clone, PartialEq, Eq)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct KeyMgmt {
    /// Key management protocol.
    pub method: KeyMgmtMethod,
    /// Key management data, if any.
    pub data: Option<String>,
}

impl KeyMgmt {
    pub fn new(method: KeyMgmtMethod) -> Self {
        KeyMgmt { method, data: None }
    }

    pub fn with_data(method: KeyMgmtMethod, data: impl ToString) -> Self {
        KeyMgmt {
            method,
            data: Some(data.to_string()),
        }
    }
}

impl FromStr for KeyMgmt {
    type Err = AttributeError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        let s = s.trim();
        if s.is_empty() {
            return Err(AttributeError::ParamNotFound {
                param: "Method".to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        }

        let (method, data) = match s.split_once(char::is_whitespace) {
            Some((method, data)) => (method, Some(data.trim().to_string())),
            None => (s, None),
        };

        // RFC 4567, section 3: KMPID = 1*(ALPHA / DIGIT).
        if !method.bytes().all(|b| b.is_ascii_alphanumeric()) {
            return Err(AttributeError::InvalidParamValue {
                param: "Method".to_string(),
                val: method.to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        }

        Ok(KeyMgmt {
            method: method.into(),
            data,
        })
    }
}

impl Display for KeyMgmt {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match &self.data {
            Some(data) => write!(f, "{} {}", self.method, data),
            None => write!(f, "{}", self.method),
        }
    }
}

impl TypedAttribute for KeyMgmt {
    const NAME: &'static str = "key-mgmt";
}

/// Remote candidate for one component of a data stream
///
/// A single entry of the [`RemoteCandidates`] attribute, in
/// `component-id connection-address port` form
/// ([RFC 8839 Section 5.2](https://datatracker.ietf.org/doc/html/rfc8839#section-5.2)).
///
/// The address must be an IP address: agents generating candidates MUST NOT
/// use FQDNs and agents receiving them MUST ignore them
/// ([RFC 8839 Section 5.1](https://datatracker.ietf.org/doc/html/rfc8839#section-5.1)).
#[derive(Debug, Clone, PartialEq, Eq)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct RemoteCandidate {
    /// Component identifier of the data stream, 1 for RTP and 2 for RTCP.
    pub component_id: u32,
    /// Remote address (IPv4 or IPv6).
    pub address: IpAddr,
    /// Remote port.
    pub port: u16,
}

impl RemoteCandidate {
    pub fn new(component_id: u32, address: impl Into<IpAddr>, port: u16) -> Self {
        RemoteCandidate {
            component_id,
            address: address.into(),
            port,
        }
    }
}

impl FromStr for RemoteCandidate {
    type Err = AttributeError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        let attr = <RemoteCandidates as TypedAttribute>::NAME.to_string();
        let mut parts = s.split_whitespace();

        let component_id_token = parts.next().ok_or_else(|| AttributeError::ParamNotFound {
            param: "Component ID".to_string(),
            attr: attr.clone(),
        })?;
        let component_id =
            component_id_token
                .parse()
                .map_err(|_| AttributeError::InvalidParamValue {
                    param: "Component ID".to_string(),
                    val: component_id_token.to_string(),
                    attr: attr.clone(),
                })?;

        let address_token = parts.next().ok_or_else(|| AttributeError::ParamNotFound {
            param: "Address".to_string(),
            attr: attr.clone(),
        })?;
        let address = address_token
            .parse()
            .map_err(|_| AttributeError::InvalidParamValue {
                param: "Address".to_string(),
                val: address_token.to_string(),
                attr: attr.clone(),
            })?;

        let port_token = parts.next().ok_or_else(|| AttributeError::ParamNotFound {
            param: "Port".to_string(),
            attr: attr.clone(),
        })?;
        let port = port_token
            .parse()
            .map_err(|_| AttributeError::InvalidParamValue {
                param: "Port".to_string(),
                val: port_token.to_string(),
                attr: attr.clone(),
            })?;

        if let Some(val) = parts.next() {
            return Err(AttributeError::UnexpectedTrailingItem {
                val: val.to_string(),
                attr,
            });
        }

        Ok(RemoteCandidate {
            component_id,
            address,
            port,
        })
    }
}

impl Display for RemoteCandidate {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{} {} {}", self.component_id, self.address, self.port)
    }
}

/// Remote candidates attribute (`a=remote-candidates`)
///
/// Lists the remote ICE candidates corresponding to the nominated pair for
/// each component of the data stream
/// ([RFC 8839 Section 5.2](https://datatracker.ietf.org/doc/html/rfc8839#section-5.2)).
/// The ordering of the components is irrelevant.
///
/// The grammar allows multiple entries in a single attribute; implementations
/// also send one entry per `a=remote-candidates` line, which results in
/// multiple attributes on the wire.
#[derive(Debug, Clone, PartialEq, Eq)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct RemoteCandidates(pub Vec<RemoteCandidate>);

impl RemoteCandidates {
    pub fn new(candidates: impl IntoIterator<Item = RemoteCandidate>) -> Self {
        RemoteCandidates(candidates.into_iter().collect())
    }
}

impl FromStr for RemoteCandidates {
    type Err = AttributeError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        let attr = <Self as TypedAttribute>::NAME.to_string();
        let mut tokens = s.split_whitespace();
        let mut candidates = Vec::new();

        // Every entry consists of exactly three tokens.
        loop {
            let triple: Vec<&str> = tokens.by_ref().take(3).collect();
            match triple.len() {
                0 => break,
                1..=2 => {
                    return Err(AttributeError::UnexpectedTrailingItem {
                        val: triple.join(" "),
                        attr,
                    })
                }
                _ => candidates.push(triple.join(" ").parse()?),
            }
        }

        if candidates.is_empty() {
            return Err(AttributeError::ParamNotFound {
                param: "Candidate".to_string(),
                attr,
            });
        }

        Ok(RemoteCandidates(candidates))
    }
}

impl Display for RemoteCandidates {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        for (i, candidate) in self.0.iter().enumerate() {
            if i > 0 {
                f.write_char(' ')?;
            }
            write!(f, "{}", candidate)?;
        }
        Ok(())
    }
}

impl TypedAttribute for RemoteCandidates {
    const NAME: &'static str = "remote-candidates";
}

/// Filter mode of the [`SourceFilter`] (`a=source-filter`) attribute.
///
/// See [RFC 4570 Section 4](https://datatracker.ietf.org/doc/html/rfc4570#section-4).
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub enum SourceFilterMode {
    /// Accept only packets sent by the listed sources.
    Incl,
    /// Reject packets sent by the listed sources.
    Excl,
}

impl SourceFilterMode {
    pub fn as_str(&self) -> &'static str {
        match self {
            SourceFilterMode::Incl => "incl",
            SourceFilterMode::Excl => "excl",
        }
    }
}

impl FromStr for SourceFilterMode {
    type Err = ParseEnumError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        if "incl".eq_ignore_ascii_case(s) {
            Ok(SourceFilterMode::Incl)
        } else if "excl".eq_ignore_ascii_case(s) {
            Ok(SourceFilterMode::Excl)
        } else {
            Err(ParseEnumError::Invalid(s.to_string()))
        }
    }
}

impl Display for SourceFilterMode {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.write_str(self.as_str())
    }
}

/// Address type of the entries of the [`SourceFilter`] (`a=source-filter`)
/// attribute.
///
/// Models the `address-types` production, which extends the SDP `addrtype`
/// token with a `*` wildcard for FQDNs
/// ([RFC 4570 Appendix A](https://datatracker.ietf.org/doc/html/rfc4570#appendix-A)).
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub enum SourceFilterAddrType {
    /// Any address family, only allowed with FQDN destinations.
    Any,
    /// IPv4 address
    Ip4,
    /// IPv6 address
    Ip6,
}

impl SourceFilterAddrType {
    pub fn as_str(&self) -> &'static str {
        match self {
            SourceFilterAddrType::Any => "*",
            SourceFilterAddrType::Ip4 => "IP4",
            SourceFilterAddrType::Ip6 => "IP6",
        }
    }
}

impl FromStr for SourceFilterAddrType {
    type Err = ParseEnumError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        if s == "*" {
            Ok(SourceFilterAddrType::Any)
        } else if "IP4".eq_ignore_ascii_case(s) {
            Ok(SourceFilterAddrType::Ip4)
        } else if "IP6".eq_ignore_ascii_case(s) {
            Ok(SourceFilterAddrType::Ip6)
        } else {
            Err(ParseEnumError::Invalid(s.to_string()))
        }
    }
}

impl Display for SourceFilterAddrType {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.write_str(self.as_str())
    }
}

/// Address of the [`SourceFilter`] (`a=source-filter`) attribute
///
/// Models the `unicast-address` and `basic-multicast-address` productions:
/// an IP address or an FQDN, but without the `/ttl` and `/number of
/// addresses` suffixes that a connection address may carry
/// ([RFC 4570 Appendix A](https://datatracker.ietf.org/doc/html/rfc4570#appendix-A)).
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub enum SourceFilterAddress {
    /// IP address
    IpAddr(IpAddr),
    /// Fully qualified domain name
    FQDN(String),
}

impl From<&str> for SourceFilterAddress {
    fn from(s: &str) -> Self {
        match s.parse::<IpAddr>() {
            Ok(address) => SourceFilterAddress::IpAddr(address),
            Err(_) => SourceFilterAddress::FQDN(s.to_string()),
        }
    }
}

impl FromStr for SourceFilterAddress {
    // FIXME use the never type when it is stable
    type Err = ();

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        Ok(s.into())
    }
}

impl Display for SourceFilterAddress {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            SourceFilterAddress::IpAddr(address) => write!(f, "{}", address),
            SourceFilterAddress::FQDN(domain) => f.write_str(domain),
        }
    }
}

/// Destination of the [`SourceFilter`] (`a=source-filter`) attribute
///
/// Models the `dest-address` production
/// ([RFC 4570 Appendix A](https://datatracker.ietf.org/doc/html/rfc4570#appendix-A)).
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub enum SourceFilterDestination {
    /// The `"*"` wildcard, matching all of the session's connection addresses
    Wildcard,
    /// Unicast, multicast address or FQDN
    Address(SourceFilterAddress),
}

impl FromStr for SourceFilterDestination {
    // FIXME use the never type when it is stable
    type Err = ();

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        if s == "*" {
            Ok(SourceFilterDestination::Wildcard)
        } else {
            Ok(SourceFilterDestination::Address(s.into()))
        }
    }
}

impl Display for SourceFilterDestination {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            SourceFilterDestination::Wildcard => f.write_str("*"),
            SourceFilterDestination::Address(address) => write!(f, "{}", address),
        }
    }
}

/// Source filter attribute (`a=source-filter`)
///
/// Restricts the set of source addresses accepted for a destination
/// address, e.g. for source-specific multicast.
///
/// See [RFC 4570 Section 4](https://datatracker.ietf.org/doc/html/rfc4570#section-4).
/// The destination must be one of the session's connection addresses or the
/// `"*"` wildcard; unlike a connection address it never carries the `/ttl`
/// and `/number of addresses` suffixes (RFC 4570, section 3.1).
///
/// Media-level source filters completely override session-level ones, which
/// consumers have to resolve themselves.
#[derive(Debug, Clone, PartialEq, Eq)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct SourceFilter {
    /// Inclusion or exclusion filter mode.
    pub mode: SourceFilterMode,
    /// Network type, usually [`NetType::In`].
    pub nettype: NetType,
    /// Address family of the destination and source addresses.
    pub addrtype: SourceFilterAddrType,
    /// Destination address or the `"*"` wildcard.
    pub destination: SourceFilterDestination,
    /// Source addresses, at least one entry.
    pub sources: Vec<SourceFilterAddress>,
}

impl FromStr for SourceFilter {
    type Err = AttributeError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        let attr = <Self as TypedAttribute>::NAME.to_string();

        // Runs of spaces are a single separator, like in c= lines,
        // so that no field can end up empty.
        let mut i = s.split(' ').filter(|part| !part.is_empty());

        let Some(mode) = i.next() else {
            return Err(AttributeError::ParamNotFound {
                param: "Filter mode".to_string(),
                attr,
            });
        };
        let mode = mode
            .parse()
            .map_err(|_| AttributeError::InvalidParamValue {
                param: "Filter mode".to_string(),
                val: mode.to_string(),
                attr: attr.clone(),
            })?;

        let Some(nettype) = i.next() else {
            return Err(AttributeError::ParamNotFound {
                param: "Network type".to_string(),
                attr,
            });
        };
        // RFC 4570 reuses the SDP nettype token (RFC 8866, section 9).
        if !is_token(nettype.as_bytes()) {
            return Err(AttributeError::InvalidParamValue {
                param: "Network type".to_string(),
                val: nettype.to_string(),
                attr: attr.clone(),
            });
        }
        let nettype = NetType::from_str(nettype).expect("infallible");

        let Some(addrtype) = i.next() else {
            return Err(AttributeError::ParamNotFound {
                param: "Address types".to_string(),
                attr,
            });
        };
        let addrtype = addrtype
            .parse()
            .map_err(|_| AttributeError::InvalidParamValue {
                param: "Address types".to_string(),
                val: addrtype.to_string(),
                attr: attr.clone(),
            })?;

        let Some(destination) = i.next() else {
            return Err(AttributeError::ParamNotFound {
                param: "Destination address".to_string(),
                attr,
            });
        };

        // RFC 4570, section 3.1: a multicast destination MUST NOT include
        // the /ttl and /number of addresses sub-fields.
        if destination.contains('/') {
            return Err(AttributeError::InvalidParamValue {
                param: "Destination address".to_string(),
                val: destination.to_string(),
                attr,
            });
        }
        let destination = SourceFilterDestination::from_str(destination).expect("infallible");
        // RFC 4570, section 3.1: the "*" address type MUST only be used with
        // FQDN destinations.
        if addrtype == SourceFilterAddrType::Any
            && matches!(
                destination,
                SourceFilterDestination::Address(SourceFilterAddress::IpAddr(_))
            )
        {
            return Err(AttributeError::InvalidParamValue {
                param: "Destination address".to_string(),
                val: destination.to_string(),
                attr,
            });
        }

        let sources: Vec<&str> = i.collect();
        if sources.is_empty() {
            return Err(AttributeError::ParamNotFound {
                param: "Source list".to_string(),
                attr,
            });
        }
        // RFC 4570, section 3.1: only the destination allows the "*" wildcard.
        if let Some(source) = sources.iter().find(|source| source == &&"*") {
            return Err(AttributeError::InvalidParamValue {
                param: "Source address".to_string(),
                val: source.to_string(),
                attr,
            });
        }
        let sources = sources.into_iter().map(SourceFilterAddress::from).collect();

        Ok(SourceFilter {
            mode,
            nettype,
            addrtype,
            destination,
            sources,
        })
    }
}

impl Display for SourceFilter {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(
            f,
            "{} {} {} {}",
            self.mode, self.nettype, self.addrtype, self.destination
        )?;
        for source in &self.sources {
            write!(f, " {}", source)?;
        }
        Ok(())
    }
}

impl TypedAttribute for SourceFilter {
    const NAME: &'static str = "source-filter";
}

/// Media stream identification tag attribute (`a=mid`)
///
/// Assigns an identification tag to a media description, unique within
/// the session description, used to reference media descriptions from
/// grouping semantics such as BUNDLE.
///
/// See [RFC 5888 Section 4](https://datatracker.ietf.org/doc/html/rfc5888#section-4).
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct Mid(pub String);

impl FromStr for Mid {
    type Err = AttributeError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        if !is_token(s.as_bytes()) {
            return Err(AttributeError::InvalidParamValue {
                param: "Identification tag".to_string(),
                val: s.to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        }

        Ok(Mid(s.to_string()))
    }
}

impl Display for Mid {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.write_str(&self.0)
    }
}

impl TypedAttribute for Mid {
    const NAME: &'static str = "mid";
}

/// RTP/RTCP multiplexing attribute (`a=rtcp-mux`)
///
/// Indicates that RTP and RTCP packets are sent to the same transport
/// address and port. It is a property attribute without a value, used
/// at the media level.
///
/// See [RFC 5761 Section 5](https://datatracker.ietf.org/doc/html/rfc5761#section-5).
#[derive(Debug, Default, Clone, Copy, PartialEq, Eq, Hash)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct RtcpMux;

impl FromStr for RtcpMux {
    type Err = AttributeError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        if !s.is_empty() {
            return Err(AttributeError::UnsupportedFormat {
                val: s.to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        }

        Ok(RtcpMux)
    }
}

impl Display for RtcpMux {
    fn fmt(&self, _: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        Ok(())
    }
}

impl TypedAttribute for RtcpMux {
    const NAME: &'static str = "rtcp-mux";
}

/// RTP/RTCP multiplexing-only attribute (`a=rtcp-mux-only`)
///
/// Indicates that the endpoint can only receive RTP/RTCP multiplexed
/// packets, i.e. it does not accept RTCP packets on a separate
/// transport address and port even if one is indicated. It is a
/// property attribute without a value, used at the media level.
///
/// See [RFC 8858 Section 3](https://datatracker.ietf.org/doc/html/rfc8858#section-3).
#[derive(Debug, Default, Clone, Copy, PartialEq, Eq, Hash)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct RtcpMuxOnly;

impl FromStr for RtcpMuxOnly {
    type Err = AttributeError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        if !s.is_empty() {
            return Err(AttributeError::UnsupportedFormat {
                val: s.to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        }

        Ok(RtcpMuxOnly)
    }
}

impl Display for RtcpMuxOnly {
    fn fmt(&self, _: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        Ok(())
    }
}

impl TypedAttribute for RtcpMuxOnly {
    const NAME: &'static str = "rtcp-mux-only";
}

/// Reduced-size RTCP attribute (`a=rtcp-rsize`)
///
/// Indicates that the endpoint supports the reduced-size RTCP
/// compound packet format for the media stream. It is a property
/// attribute without a value, used at the media level.
///
/// See [RFC 5506 Section 5](https://datatracker.ietf.org/doc/html/rfc5506#section-5).
#[derive(Debug, Default, Clone, Copy, PartialEq, Eq, Hash)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct RtcpRsize;

impl FromStr for RtcpRsize {
    type Err = AttributeError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        if !s.is_empty() {
            return Err(AttributeError::UnsupportedFormat {
                val: s.to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        }

        Ok(RtcpRsize)
    }
}

impl Display for RtcpRsize {
    fn fmt(&self, _: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        Ok(())
    }
}

impl TypedAttribute for RtcpRsize {
    const NAME: &'static str = "rtcp-rsize";
}

/// ICE-lite implementation attribute (`a=ice-lite`)
///
/// Indicates that the agent implements the ICE-lite implementation,
/// which does not run the full ICE connectivity checks. It is a
/// property attribute without a value, used at the session level.
///
/// See [RFC 5245 Section 15.3](https://datatracker.ietf.org/doc/html/rfc5245#section-15.3).
#[derive(Debug, Default, Clone, Copy, PartialEq, Eq, Hash)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct IceLite;

impl FromStr for IceLite {
    type Err = AttributeError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        if !s.is_empty() {
            return Err(AttributeError::UnsupportedFormat {
                val: s.to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        }

        Ok(IceLite)
    }
}

impl Display for IceLite {
    fn fmt(&self, _: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        Ok(())
    }
}

impl TypedAttribute for IceLite {
    const NAME: &'static str = "ice-lite";
}

/// ICE character of the `ice-char` production (RFC 5245, section 15.1).
fn is_ice_char(c: char) -> bool {
    matches!(c, 'a'..='z' | 'A'..='Z' | '0'..='9' | '+' | '/')
}

/// ICE username fragment attribute (`a=ice-ufrag`)
///
/// Conveys the username fragment used by ICE for message integrity,
/// 4 to 256 ICE characters. It can appear at the session level or the
/// media level, where the media level value takes precedence.
///
/// See [RFC 5245 Section 15.4](https://datatracker.ietf.org/doc/html/rfc5245#section-15.4).
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct IceUfrag(pub String);

impl FromStr for IceUfrag {
    type Err = AttributeError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        // ICE characters are ASCII, so the byte length is the length.
        if !(4..=256).contains(&s.len()) || !s.chars().all(is_ice_char) {
            return Err(AttributeError::InvalidParamValue {
                param: "ICE username fragment".to_string(),
                val: s.to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        }

        Ok(IceUfrag(s.to_string()))
    }
}

impl Display for IceUfrag {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.write_str(&self.0)
    }
}

impl TypedAttribute for IceUfrag {
    const NAME: &'static str = "ice-ufrag";
}

/// ICE password attribute (`a=ice-pwd`)
///
/// Conveys the password used by ICE for message integrity, 22 to 256
/// ICE characters. It can appear at the session level or the media
/// level, where the media level value takes precedence.
///
/// See [RFC 5245 Section 15.4](https://datatracker.ietf.org/doc/html/rfc5245#section-15.4).
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct IcePwd(pub String);

impl FromStr for IcePwd {
    type Err = AttributeError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        // ICE characters are ASCII, so the byte length is the length.
        if !(22..=256).contains(&s.len()) || !s.chars().all(is_ice_char) {
            return Err(AttributeError::InvalidParamValue {
                param: "ICE password".to_string(),
                val: s.to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        }

        Ok(IcePwd(s.to_string()))
    }
}

impl Display for IcePwd {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.write_str(&self.0)
    }
}

impl TypedAttribute for IcePwd {
    const NAME: &'static str = "ice-pwd";
}

/// ICE extension option tags attribute (`a=ice-options`)
///
/// Lists the ICE extension option tags supported by the agent, e.g.
/// `trickle` (RFC 8839). It is used at the session level.
///
/// See [RFC 5245 Section 15.5](https://datatracker.ietf.org/doc/html/rfc5245#section-15.5).
#[derive(Debug, Clone, PartialEq, Eq)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct IceOptions(pub Vec<String>);

impl IceOptions {
    pub fn new(tags: impl IntoIterator<Item = impl ToString>) -> Self {
        IceOptions(tags.into_iter().map(|tag| tag.to_string()).collect())
    }
}

impl FromStr for IceOptions {
    type Err = AttributeError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        let attr = <Self as TypedAttribute>::NAME.to_string();
        let mut tags = Vec::new();

        for tag in s.split_whitespace() {
            if !tag.chars().all(is_ice_char) {
                return Err(AttributeError::InvalidParamValue {
                    param: "ICE option tag".to_string(),
                    val: tag.to_string(),
                    attr,
                });
            }

            tags.push(tag.to_string());
        }

        if tags.is_empty() {
            return Err(AttributeError::ParamNotFound {
                param: "ICE option tags".to_string(),
                attr,
            });
        }

        Ok(IceOptions(tags))
    }
}

impl Display for IceOptions {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        for (i, tag) in self.0.iter().enumerate() {
            if i > 0 {
                f.write_char(' ')?;
            }
            f.write_str(tag)?;
        }
        Ok(())
    }
}

impl TypedAttribute for IceOptions {
    const NAME: &'static str = "ice-options";
}

/// End of ICE candidates attribute (`a=end-of-candidates`)
///
/// Indicates that the sending agent will not trickle further ICE
/// candidates. It is a property attribute without a value, used at the
/// session level or the media level.
///
/// See [RFC 8840 Section 8.1](https://datatracker.ietf.org/doc/html/rfc8840#section-8.1).
#[derive(Debug, Default, Clone, Copy, PartialEq, Eq, Hash)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct EndOfCandidates;

impl FromStr for EndOfCandidates {
    type Err = AttributeError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        if !s.is_empty() {
            return Err(AttributeError::UnsupportedFormat {
                val: s.to_string(),
                attr: <Self as TypedAttribute>::NAME.to_string(),
            });
        }

        Ok(EndOfCandidates)
    }
}

impl Display for EndOfCandidates {
    fn fmt(&self, _: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        Ok(())
    }
}

impl TypedAttribute for EndOfCandidates {
    const NAME: &'static str = "end-of-candidates";
}

/// MediaStream identification attribute (`a=msid`)
///
/// Associates a media description with a MediaStream and identifies the
/// MediaStreamTrack it conveys in the application data. Both fields are
/// tokens of 1 to 64 characters.
///
/// See [RFC 8830 Section 2](https://datatracker.ietf.org/doc/html/rfc8830#section-2).
#[derive(Debug, Clone, PartialEq, Eq)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct Msid {
    /// Identifier of the MediaStream this media description belongs to.
    pub id: String,
    /// Application data, the identifier of the MediaStreamTrack.
    pub appdata: Option<String>,
}

impl Msid {
    pub fn new(id: impl ToString, appdata: Option<impl ToString>) -> Self {
        Msid {
            id: id.to_string(),
            appdata: appdata.map(|appdata| appdata.to_string()),
        }
    }
}

impl FromStr for Msid {
    type Err = AttributeError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        let attr = <Self as TypedAttribute>::NAME.to_string();
        let mut tokens = s.split_whitespace();

        let id = tokens.next().ok_or_else(|| AttributeError::ParamNotFound {
            param: "MSID id".to_string(),
            attr: attr.clone(),
        })?;
        let appdata = tokens.next();

        let trailing: Vec<_> = tokens.collect();
        if !trailing.is_empty() {
            return Err(AttributeError::UnexpectedTrailingItem {
                val: trailing.join(" "),
                attr,
            });
        }

        // Both fields are 1*64 token-chars (RFC 8830, section 2).
        if id.len() > 64 || !is_token(id.as_bytes()) {
            return Err(AttributeError::InvalidParamValue {
                param: "MSID id".to_string(),
                val: id.to_string(),
                attr,
            });
        }

        if let Some(appdata) = appdata {
            if appdata.len() > 64 || !is_token(appdata.as_bytes()) {
                return Err(AttributeError::InvalidParamValue {
                    param: "MSID appdata".to_string(),
                    val: appdata.to_string(),
                    attr,
                });
            }
        }

        Ok(Msid {
            id: id.to_string(),
            appdata: appdata.map(ToString::to_string),
        })
    }
}

impl Display for Msid {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.write_str(&self.id)?;
        if let Some(appdata) = &self.appdata {
            f.write_char(' ')?;
            f.write_str(appdata)?;
        }
        Ok(())
    }
}

impl TypedAttribute for Msid {
    const NAME: &'static str = "msid";
}

/// SCTP port attribute (`a=sctp-port`)
///
/// Indicates the SCTP port number of the association used by the media
/// description, used with the "UDP/DTLS/SCTP" and "TCP/DTLS/SCTP"
/// proto values at the media level. The port range is 0 to 65535 and
/// leading zeroes are not used.
///
/// See [RFC 8841 Section 5.2](https://datatracker.ietf.org/doc/html/rfc8841#section-5.2).
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct SctpPort(pub u16);

/// Parses `1*5DIGIT` without leading zeroes into a `u16` port or count.
fn parse_1_5_digits(s: &str) -> Option<u16> {
    if s.is_empty()
        || s.len() > 5
        || !s.chars().all(|c| c.is_ascii_digit())
        || (s.len() > 1 && s.starts_with('0'))
    {
        return None;
    }

    s.parse().ok()
}

impl FromStr for SctpPort {
    type Err = AttributeError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        let invalid = || AttributeError::InvalidParamValue {
            param: "SCTP port".to_string(),
            val: s.to_string(),
            attr: <Self as TypedAttribute>::NAME.to_string(),
        };

        // sctp-port-value = 1*5DIGIT, leading zeroes must not be used.
        let port = parse_1_5_digits(s).ok_or_else(invalid)?;
        Ok(SctpPort(port))
    }
}

impl Display for SctpPort {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{}", self.0)
    }
}

impl TypedAttribute for SctpPort {
    const NAME: &'static str = "sctp-port";
}

/// Maximum SCTP user message size attribute (`a=max-message-size`)
///
/// Indicates the maximum SCTP user message size, in bytes, that the
/// endpoint is willing to receive, where zero means any size. It is
/// used at the media level and defaults to 64 KiB when absent. Leading
/// zeroes are not used.
///
/// See [RFC 8841 Section 6.2](https://datatracker.ietf.org/doc/html/rfc8841#section-6.2).
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct MaxMessageSize(pub u64);

impl FromStr for MaxMessageSize {
    type Err = AttributeError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        let invalid = || AttributeError::InvalidParamValue {
            param: "Max message size".to_string(),
            val: s.to_string(),
            attr: <Self as TypedAttribute>::NAME.to_string(),
        };

        // max-message-size-value = 1*DIGIT, leading zeroes must not be used.
        let size = parse_decimal_no_leading_zeroes(s).ok_or_else(invalid)?;
        Ok(MaxMessageSize(size))
    }
}

impl Display for MaxMessageSize {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{}", self.0)
    }
}

impl TypedAttribute for MaxMessageSize {
    const NAME: &'static str = "max-message-size";
}

/// SCTP port map attribute (`a=sctpmap`)
///
/// Legacy association of the SCTP port with the application running on
/// the association and the number of streams, sent as
/// `a=sctpmap:<port> <app> [<streams>]`. It was defined only in
/// `draft-ietf-mmusic-sctp-sdp`, never published as an RFC, and is
/// superseded by `a=sctp-port` (RFC 8841, section 5).
///
/// See [draft-ietf-mmusic-sctp-sdp](https://datatracker.ietf.org/doc/html/draft-ietf-mmusic-sctp-sdp).
#[derive(Debug, Clone, PartialEq, Eq)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct SctpMap {
    /// SCTP port number, in the range 0 to 65535.
    pub number: u16,
    /// Application running on top of the association, e.g.
    /// `webrtc-datachannel`.
    pub app: String,
    /// Number of streams supported by each side of the association.
    pub streams: Option<u16>,
}

impl SctpMap {
    pub fn new(number: u16, app: impl ToString, streams: Option<u16>) -> Self {
        SctpMap {
            number,
            app: app.to_string(),
            streams,
        }
    }
}

impl FromStr for SctpMap {
    type Err = AttributeError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        let attr = <Self as TypedAttribute>::NAME.to_string();
        let mut tokens = s.split_whitespace();

        let number = tokens.next().ok_or_else(|| AttributeError::ParamNotFound {
            param: "SCTP port number".to_string(),
            attr: attr.clone(),
        })?;
        let number = parse_1_5_digits(number).ok_or_else(|| AttributeError::InvalidParamValue {
            param: "SCTP port number".to_string(),
            val: number.to_string(),
            attr: attr.clone(),
        })?;

        let app = tokens.next().ok_or_else(|| AttributeError::ParamNotFound {
            param: "Application".to_string(),
            attr: attr.clone(),
        })?;
        if !is_token(app.as_bytes()) {
            return Err(AttributeError::InvalidParamValue {
                param: "Application".to_string(),
                val: app.to_string(),
                attr,
            });
        }

        let streams = match tokens.next() {
            Some(streams) => Some(parse_1_5_digits(streams).ok_or_else(|| {
                AttributeError::InvalidParamValue {
                    param: "Stream count".to_string(),
                    val: streams.to_string(),
                    attr: attr.clone(),
                }
            })?),
            None => None,
        };

        let trailing: Vec<_> = tokens.collect();
        if !trailing.is_empty() {
            return Err(AttributeError::UnexpectedTrailingItem {
                val: trailing.join(" "),
                attr,
            });
        }

        Ok(SctpMap {
            number,
            app: app.to_string(),
            streams,
        })
    }
}

impl Display for SctpMap {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{} {}", self.number, self.app)?;
        if let Some(streams) = self.streams {
            write!(f, " {}", streams)?;
        }
        Ok(())
    }
}

impl TypedAttribute for SctpMap {
    const NAME: &'static str = "sctpmap";
}

#[cfg(test)]
mod tests {
    use std::net::{IpAddr, Ipv4Addr, Ipv6Addr};

    use super::*;
    use crate::*;

    #[test]
    fn direction_parse() {
        assert_eq!("sendonly".parse::<Direction>(), Ok(Direction::SendOnly));
        assert_eq!("recvonly".parse::<Direction>(), Ok(Direction::RecvOnly));
        assert_eq!("sendrecv".parse::<Direction>(), Ok(Direction::SendRecv));
        assert_eq!("inactive".parse::<Direction>(), Ok(Direction::Inactive));
        assert!("invalid".parse::<Direction>().is_err());
    }

    #[test]
    fn direction_display() {
        assert_eq!(Direction::SendOnly.to_string(), "sendonly");
        assert_eq!(Direction::RecvOnly.to_string(), "recvonly");
        assert_eq!(Direction::SendRecv.to_string(), "sendrecv");
        assert_eq!(Direction::Inactive.to_string(), "inactive");
    }

    #[test]
    fn parse_rtcp_fb() {
        let sdp = "v=0\r
o=alice 3203093520 3203093520 IN IP4 host.example.com\r
s=Multicast video with feedback\r
t=3203130148 3203137348\r
m=audio 49170 RTP/AVP 0\r
c=IN IP4 224.2.1.183\r
a=rtpmap:0 PCMU/8000\r
m=video 51372 RTP/AVPF 98 99\r
c=IN IP4 224.2.1.184\r
a=rtpmap:98 H263-1998/90000\r
a=rtpmap:99 H261/90000\r
a=rtcp-fb:* nack\r
a=rtcp-fb:98 nack rpsi\r
a=rtcp-fb:* trr-int 1000\r
a=rtcp-fb:98 ccm vbcm 1 2\r
a=rtcp-fb:* ccm tmmbr smaxpr=120\r
";

        let parsed = Session::parse(sdp.as_bytes()).unwrap();
        let mut written = vec![];
        parsed.write(&mut written).unwrap();

        let v = fallible_iterator::convert(parsed.medias[1].attributes_typed::<RtcpFb>())
            .collect::<Vec<_>>()
            .expect("Valid vector of attributes");
        assert_eq!(v[0].pt, RtcpFbPt::Wildcard);
        assert_eq!(v[1].val, RtcpFbVal::Nack(Some(RtcpFbNack::Rpsi)));
        assert_eq!(v[2].val, RtcpFbVal::TrrInt(1000));
        assert_eq!(v[3].val, RtcpFbVal::Ccm(RtcpFbCcm::Vbcm(vec![1, 2])));
        assert_eq!(
            v[4].val,
            RtcpFbVal::Ccm(RtcpFbCcm::Tmmbr(Some("smaxpr=120".to_string())))
        );
    }

    #[test]
    fn parse_group_attribute() {
        let sdp = "v=0\r
o=Laura 289083124 289083124 IN IP4 two.example.com\r
c=IN IP4 233.252.0.1/127\r
t=0 0\r
a=group:LS 1 2\r
m=audio 30000 RTP/AVP 0\r
a=mid:1\r
m=video 30002 RTP/AVP 31\r
a=mid:2\r
m=audio 30004 RTP/AVP 0\r
i=This media stream contains the Spanish translation\r
a=mid:3\r
";
        let parsed = Session::parse(sdp.as_bytes()).unwrap();

        let g = parsed.attributes_typed::<Group>().collect::<Vec<_>>();
        assert_eq!(g.len(), 1);
        assert_eq!(g[0].as_ref().unwrap().semantics, GroupSemantics::LS);
        assert_eq!(
            g[0].as_ref().unwrap().mid_tags,
            vec!["1".to_string(), "2".to_string()]
        );
    }

    #[test]
    fn parse_setup_attribute() {
        let sdp = "v=0\r
m=image 54111 TCP t38\r
c=IN IP4 192.0.2.2\r
a=setup:actpass\r
a=connection:new\r
";
        let media = Session::parse(sdp.as_bytes()).unwrap().medias;

        let s = media[0].attributes_typed::<Setup>().collect::<Vec<_>>();

        assert_eq!(s.len(), 1);
        assert_eq!(s[0].as_ref().unwrap().to_owned(), Setup::ActPass);
    }

    #[test]
    fn parse_ssrc_attributes() {
        let sdp = "v=0\r
o=jdoe 2890844526 2890842807 IN IP4 10.47.16.5\r
m=video 49174 RTP/AVPF 96 98\r
a=rtpmap:98 rtx/90000\r
a=fmtp:98 apt=96;rtx-time=3000\r
a=ssrc-group:FID 11111 22222\r
a=ssrc:11111 cname:user3@example.com\r
a=ssrc:22222 fmtp:0 0-15\r
a=ssrc-group:FID 33333 44444\r
a=ssrc:33333 cname:user3@example.com\r
a=ssrc:44444 cname:user3@example.com\r
a=ssrc:1698359993 rtcp:5003 IN IP4 127.0.0.1
";

        let parsed = Session::parse(sdp.as_bytes()).unwrap();
        let m = &parsed.medias[0];

        let ssrcs = m
            .attributes_typed::<Ssrc>()
            .filter(|s| {
                let Ok(ssrc) = s else { return false };
                ssrc.attribute == SsrcAttribute::Fmtp || ssrc.attribute == SsrcAttribute::Rtcp
            })
            .collect::<Vec<_>>();

        let ssrc_id = ssrcs[0].as_ref().unwrap().ssrc_id;

        let ssrc_groups = m
            .attributes_typed::<SsrcGroup>()
            .filter(|s| {
                let Ok(ssrc_group) = s else { return false };

                ssrc_group.ssrc_ids[1] == ssrc_id
            })
            .collect::<Vec<_>>();

        assert_eq!(
            ssrc_groups[0].as_ref().unwrap().semantics,
            GroupSemantics::FID
        );

        assert_eq!(ssrcs[1].as_ref().unwrap().attribute, SsrcAttribute::Rtcp);
    }

    #[test]
    fn parse_crypto_attributes() {
        let sdp = "v=0\r
o=sam 2890844526 2890842807 IN IP4 10.47.16.5\r
s=SRTP Discussion\r
i=A discussion of Secure RTP\r
u=http://www.example.com/seminars/srtp.pdf\r
e=marge@example.com (Marge Simpson)\r
c=IN IP4 168.2.17.12\r
t=2873397496 2873404696\r
m=audio 49170 RTP/SAVP 0\r
a=crypto:1 AES_CM_128_HMAC_SHA1_80 inline:WVNfX19zZW1jdGwgKCkgewkyMjA7fQp9CnVubGVz|2^20|1:4 FEC_ORDER=SRTP_FEC\r
a=crypto:2 F8_128_HMAC_SHA1_80 inline:MTIzNDU2Nzg5QUJDREUwMTIzNDU2Nzg5QUJjZGVm|2^20|1:4;inline:QUJjZGVmMTIzNDU2Nzg5QUJDREUwMTIzNDU2Nzg5|2^20|2:4 FEC_ORDER=FEC_SRTP\r
m=video 51372 RTP/SAVP 31\r
a=crypto:1 AES_CM_128_HMAC_SHA1_80 inline:YUJDZGVmZ2hpSktMbW9QUXJzVHVWd3l6MTIzNDU2|1066:4\r
";

        let parsed = Session::parse(sdp.as_bytes()).unwrap();
        let a = &parsed.medias[0];

        let audio_cryptos = a.attributes_typed::<Crypto>().collect::<Vec<_>>();

        assert_eq!(
            audio_cryptos[0].as_ref().unwrap().crypto_suite,
            CryptoSuite::AesCm128HmacSha1_80
        );
        assert_eq!(audio_cryptos[1].as_ref().unwrap().key_params.len(), 2);

        assert_eq!(
            audio_cryptos[1].as_ref().unwrap().key_params[1].mki_and_length,
            Some((2, 4))
        );

        assert_eq!(
            audio_cryptos[1].as_ref().unwrap().session_params[0],
            SrtpSessionParam::FecOrder(FecOrder::FecSrtp)
        );

        let v = &parsed.medias[1];

        let video_cryptos = v
            .attributes_typed::<Crypto>()
            .filter(|c| {
                let Ok(crypto) = c else { return false };

                crypto.tag == 1
            })
            .collect::<Vec<_>>();

        let test_crypto = Crypto {
            tag: 1,
            crypto_suite: CryptoSuite::AesCm128HmacSha1_80,
            key_params: vec![SrtpKeyParam {
                key_and_salt: "YUJDZGVmZ2hpSktMbW9QUXJzVHVWd3l6MTIzNDU2".to_string(),
                lifetime: None,
                mki_and_length: Some((1066, 4)),
            }],
            session_params: Vec::new(),
        };

        assert_eq!(&test_crypto, video_cryptos[0].as_ref().unwrap());
    }

    #[test]
    fn write_crypto_attribute() {
        let crypto = Crypto {
            tag: 1,
            crypto_suite: CryptoSuite::AesCm128HmacSha1_80,
            key_params: vec![
                SrtpKeyParam {
                    key_and_salt: "WVNfX19zZW1jdGwgKCkgewkyMjA7fQp9CnVubGVz".to_string(),
                    lifetime: Some(1048576),
                    mki_and_length: Some((1, 4)),
                },
                SrtpKeyParam {
                    key_and_salt: "WVNfX19zZW1jdGwgKCkgewkyMjA7fQp9CnVubGVz".to_string(),
                    lifetime: Some(1048576),
                    mki_and_length: Some((1, 4)),
                },
            ],
            session_params: vec![SrtpSessionParam::FecOrder(FecOrder::SrtpFec)],
        };

        assert_eq!(
            crypto.to_string(),
            "1 AES_CM_128_HMAC_SHA1_80 inline:WVNfX19zZW1jdGwgKCkgewkyMjA7fQp9CnVubGVz|2^20|1:4;inline:WVNfX19zZW1jdGwgKCkgewkyMjA7fQp9CnVubGVz|2^20|1:4 FEC_ORDER=SRTP_FEC"
        );
    }

    #[test]
    fn parse_srtp_key_param_lifetime() {
        // RFC 4568 allows lifetimes up to 2^48, which doesn't fit into u32.
        let param = SrtpKeyParam::from_str("inline:YWJj|2^48").unwrap();
        assert_eq!(param.lifetime, Some(1 << 48));
        assert_eq!(param.to_string(), "inline:YWJj|2^48");

        let param = SrtpKeyParam::from_str("inline:YWJj|1000000000000").unwrap();
        assert_eq!(param.lifetime, Some(1_000_000_000_000));
        assert_eq!(param.to_string(), "inline:YWJj|1000000000000");

        for invalid in [
            // larger than the maximum of 2^48
            "inline:YWJj|2^49",
            "inline:YWJj|2^100",
            "inline:YWJj|281474976710657",
            // zero is not a positive integer
            "inline:YWJj|0",
            // leading zeroes and signs are not allowed
            "inline:YWJj|007",
            "inline:YWJj|0123",
            "inline:YWJj|2^007",
            "inline:YWJj|+1048576",
            "inline:YWJj|2^+20",
        ] {
            assert!(
                SrtpKeyParam::from_str(invalid).is_err(),
                "{} should be invalid",
                invalid
            );
        }
    }

    #[test]
    fn parse_candidate_attributes() {
        use std::net::{Ipv4Addr, Ipv6Addr};

        let sdp = "v=0\r
o=- 2890844526 2890842807 IN IP4 192.168.1.1\r
s=-\r
c=IN IP4 192.168.1.1\r
t=0 0\r
m=audio 49152 RTP/AVP 0\r
a=candidate:1 1 UDP 2130706432 192.168.1.1 49152 typ host raddr 10.0.1.1 rport 49153 generation 0\r
a=candidate:2 1 UDP 1692467200 10.0.1.1 49152 typ srflx raddr 192.168.1.1 rport 49153\r
a=candidate:3 2 UDP 1692467184 192.168.1.1 49153 typ host\r
a=candidate:4 1 UDP 100 2001:db8::1 49152 typ host\r
a=candidate:5 1 UDP 50 192.168.1.1 49154 typ prflx\r
a=candidate:6 1 UDP 25 192.168.1.1 49155 typ relay raddr 10.0.0.1 rport 49156\r
a=candidate:7 1 UDP 10 192.168.1.1 49157 typ unknown_type\r
";

        let session = Session::parse(sdp.as_bytes()).unwrap();
        let candidates: Vec<Candidate> =
            fallible_iterator::convert(session.medias[0].attributes_typed::<Candidate>())
                .collect::<Vec<_>>()
                .expect("Valid vector of candidates");

        assert_eq!(candidates.len(), 7);

        assert_eq!(candidates[0].foundation, "1");
        assert_eq!(candidates[0].component_id, 1);
        assert_eq!(
            candidates[0].address,
            CandidateAddress::IpAddr(IpAddr::V4(Ipv4Addr::new(192, 168, 1, 1)))
        );
        assert_eq!(candidates[0].port, 49152);
        assert_eq!(candidates[0].typ, CandidateType::Host);
        assert_eq!(
            candidates[0].rel_addr,
            Some(IpAddr::V4(Ipv4Addr::new(10, 0, 1, 1)))
        );
        assert_eq!(candidates[0].rel_port, Some(49153));
        assert_eq!(
            candidates[0].extensions,
            vec![("generation".to_string(), "0".to_string())]
        );

        assert_eq!(candidates[1].foundation, "2");
        assert_eq!(candidates[1].typ, CandidateType::Srflx);
        assert_eq!(
            candidates[1].rel_addr,
            Some(IpAddr::V4(Ipv4Addr::new(192, 168, 1, 1)))
        );
        assert_eq!(candidates[1].rel_port, Some(49153));

        assert_eq!(candidates[2].foundation, "3");
        assert_eq!(candidates[2].component_id, 2);
        assert_eq!(candidates[2].typ, CandidateType::Host);

        assert_eq!(candidates[3].foundation, "4");
        assert_eq!(
            candidates[3].address,
            CandidateAddress::IpAddr(IpAddr::V6(Ipv6Addr::new(0x2001, 0xdb8, 0, 0, 0, 0, 0, 1)))
        );
        assert_eq!(candidates[3].typ, CandidateType::Host);

        assert_eq!(candidates[4].foundation, "5");
        assert_eq!(candidates[4].typ, CandidateType::Prflx);

        assert_eq!(candidates[5].foundation, "6");
        assert_eq!(candidates[5].typ, CandidateType::Relay);

        assert_eq!(candidates[6].foundation, "7");
        assert_eq!(
            candidates[6].typ,
            CandidateType::Other("unknown_type".to_string())
        );
    }

    #[test]
    fn write_candidate() {
        use std::net::Ipv4Addr;

        let candidate = Candidate {
            foundation: "abcd/1234".into(),
            component_id: 1,
            transport: "UDP".into(),
            priority: 2130706432,
            address: CandidateAddress::IpAddr(IpAddr::V4(Ipv4Addr::new(192, 168, 0, 1))),
            port: 49152,
            typ: CandidateType::Srflx,
            rel_addr: Some(IpAddr::V4(Ipv4Addr::new(10, 0, 0, 1))),
            rel_port: Some(49153),
            extensions: vec![("tcptype".to_string(), "active".to_string())],
        };

        assert_eq!(
            candidate.to_string(),
            "abcd/1234 1 UDP 2130706432 192.168.0.1 49152 typ srflx raddr 10.0.0.1 rport 49153 tcptype active"
        );
    }

    #[test]
    fn test_attribute_errors() {
        // Test RtpMap error paths
        assert_eq!(
            "99".parse::<RtpMap>().unwrap_err(),
            AttributeError::UnsupportedFormat {
                val: "99".to_string(),
                attr: "rtpmap".to_string()
            }
        );
        assert_eq!(
            "abc 90000".parse::<RtpMap>().unwrap_err(),
            AttributeError::InvalidParamValue {
                param: "Payload type".to_string(),
                val: "abc".to_string(),
                attr: "rtpmap".to_string()
            }
        );
        assert_eq!(
            "200 enc/90000".parse::<RtpMap>().unwrap_err(),
            AttributeError::InvalidParamValue {
                param: "Payload type".to_string(),
                val: "200(expected 0-127)".to_string(),
                attr: "rtpmap".to_string()
            }
        );
        assert_eq!(
            "99 ".parse::<RtpMap>().unwrap_err(),
            AttributeError::ParamNotFound {
                param: "Clock rate".to_string(),
                attr: "rtpmap".to_string()
            }
        );
        assert_eq!(
            "99 /".parse::<RtpMap>().unwrap_err(),
            AttributeError::InvalidParamValue {
                param: "Clock rate".to_string(),
                val: "".to_string(),
                attr: "rtpmap".to_string()
            }
        );

        assert_eq!(
            "invalid".parse::<Fmtp>().unwrap_err(),
            AttributeError::UnsupportedFormat {
                val: "invalid".to_string(),
                attr: "fmtp".to_string()
            }
        );
        assert_eq!(
            "abc profile=1".parse::<Fmtp>().unwrap_err(),
            AttributeError::InvalidParamValue {
                param: "fmtp".to_string(),
                val: "abc".to_string(),
                attr: "fmtp".to_string()
            }
        );

        // Test Rtcp error paths
        assert_eq!(
            "".parse::<Rtcp>().unwrap_err(),
            AttributeError::ParamNotFound {
                param: "Port".to_string(),
                attr: "rtcp".to_string()
            }
        );
        assert_eq!(
            "abc IN IP4 127.0.0.1".parse::<Rtcp>().unwrap_err(),
            AttributeError::InvalidParamValue {
                param: "Port".to_string(),
                val: "abc".to_string(),
                attr: "rtcp".to_string()
            }
        );

        // Test Fingerprint error paths
        assert_eq!(
            "".parse::<Fingerprint>().unwrap_err(),
            AttributeError::ParamNotFound {
                param: "Hash value".to_string(),
                attr: "fingerprint".to_string()
            }
        );
        assert_eq!(
            "SHA-1".parse::<Fingerprint>().unwrap_err(),
            AttributeError::ParamNotFound {
                param: "Hash value".to_string(),
                attr: "fingerprint".to_string()
            }
        );

        // Test Candidate error paths
        assert_eq!(
            "".parse::<Candidate>().unwrap_err(),
            AttributeError::ParamNotFound {
                param: "Component id".to_string(),
                attr: "candidate".to_string()
            }
        );
        assert_eq!(
            "1 1 UDP 100".parse::<Candidate>().unwrap_err(),
            AttributeError::ParamNotFound {
                param: "Address".to_string(),
                attr: "candidate".to_string()
            }
        );

        // Test ExtMap error paths
        assert_eq!(
            "".parse::<ExtMap>().unwrap_err(),
            AttributeError::InvalidParamValue {
                param: "Id".to_string(),
                val: "".to_string(),
                attr: "extmap".to_string()
            }
        );
        assert_eq!(
            "999999 http://example.com".parse::<ExtMap>().unwrap_err(),
            AttributeError::InvalidParamValue {
                param: "Id".to_string(),
                val: "999999".to_string(),
                attr: "extmap".to_string()
            }
        );

        // Test Group error paths
        assert_eq!(
            "".parse::<Group>().unwrap_err(),
            AttributeError::ParamNotFound {
                param: "Media identification tags".to_string(),
                attr: "group".to_string()
            }
        );
        assert_eq!(
            "LS".parse::<Group>().unwrap_err(),
            AttributeError::ParamNotFound {
                param: "Media identification tags".to_string(),
                attr: "group".to_string()
            }
        );

        // Test Ssrc error paths
        assert_eq!(
            "".parse::<Ssrc>().unwrap_err(),
            AttributeError::ParamNotFound {
                param: "Ssrc id".to_string(),
                attr: "ssrc".to_string()
            }
        );
        assert_eq!(
            "abc".parse::<Ssrc>().unwrap_err(),
            AttributeError::ParamNotFound {
                param: "Ssrc id".to_string(),
                attr: "ssrc".to_string()
            }
        );

        // Test Setup error paths
        let setup_err = "foo".parse::<Setup>().err().unwrap();
        assert!(matches!(setup_err, AttributeError::Other { .. }));
        assert_eq!(format!("{}", setup_err), "setup: Invalid Setup value foo");

        // Test Crypto error paths
        assert_eq!(
            "".parse::<Crypto>().unwrap_err(),
            AttributeError::InvalidParamValue {
                param: "Tag".to_string(),
                val: "".to_string(),
                attr: "crypto".to_string()
            }
        );
        assert_eq!(
            "abc AES_CM_128_HMAC_SHA1_32 inline:key"
                .parse::<Crypto>()
                .unwrap_err(),
            AttributeError::InvalidParamValue {
                param: "Tag".to_string(),
                val: "abc".to_string(),
                attr: "crypto".to_string()
            }
        );

        // Test RtcpFb error paths
        assert_eq!(
            "".parse::<RtcpFb>().unwrap_err(),
            AttributeError::InvalidParamValue {
                param: "Payload format".to_string(),
                val: "".to_string(),
                attr: "rtcp-fb".to_string()
            }
        );
        assert_eq!(
            "*".parse::<RtcpFb>().unwrap_err(),
            AttributeError::ParamNotFound {
                param: "Rtcp feedback value".to_string(),
                attr: "rtcp-fb".to_string()
            }
        );
        assert_eq!(
            "1 ack ccfb".parse::<RtcpFb>().unwrap_err(),
            AttributeError::InvalidParamValue {
                param: "Payload type of Congestion control feedback (ccfb)".to_string(),
                val: "1(expected wildcard (*))".to_string(),
                attr: "rtcp-fb".to_string()
            }
        );

        // Test attribute_typed with missing value
        let media = Media {
            media: "video".into(),
            port: 1234,
            num_ports: None,
            proto: "RTP/SAVPF".into(),
            fmt: "".into(),
            media_title: None,
            connections: vec![],
            bandwidths: vec![],
            key: None,
            attributes: vec![Attribute {
                attribute: "rtpmap".into(),
                value: None,
            }],
        };
        assert_eq!(
            media
                .attributes_typed::<RtpMap>()
                .collect::<Vec<Result<RtpMap, AttributeError>>>()
                .remove(0)
                .unwrap_err(),
            AttributeError::UnsupportedFormat {
                val: String::new(),
                attr: "rtpmap".to_string()
            }
        );
    }

    #[test]
    #[allow(deprecated)]
    fn parse_rtcp_address() {
        let sdp = "v=0\r
o=alice 3203093520 3203093520 IN IP4 host.example.com\r
s=parse rtcp attribute address test\r
a=rtcp:5000 IN IP4 127.0.0.1\r
a=rtcp:5000 IN IP4 127.0.0.0/24\r
a=rtcp:5000 IN IP6 ::1\r
a=rtcp:5000 IN NONIP non-IP\r
a=rtcp:53020\r
";

        let parsed = Session::parse(sdp.as_bytes()).unwrap();
        let mut rtcp_attr_iter = parsed.attributes_typed::<Rtcp>();

        let rtcp = rtcp_attr_iter.next().unwrap().unwrap();
        assert_eq!(rtcp.addrtype, Some(AddrType::Ip4));
        assert_eq!(rtcp.connection_address.as_deref(), Some("127.0.0.1"));
        assert_eq!(
            rtcp.try_parse_connection_ip_address().unwrap().unwrap(),
            IpAddr::V4(Ipv4Addr::LOCALHOST),
        );

        let rtcp = rtcp_attr_iter.next().unwrap().unwrap();
        assert_eq!(rtcp.addrtype, Some(AddrType::Ip4));
        assert_eq!(rtcp.connection_address.as_deref(), Some("127.0.0.0/24"));
        // The `/24` suffix is parsed as the TTL of RFC 8866 multicast
        // notation, not as part of the address, see [`Rtcp::try_address`].
        assert_eq!(
            rtcp.try_parse_connection_ip_address().unwrap().unwrap(),
            IpAddr::V4(Ipv4Addr::new(127, 0, 0, 0)),
        );
        let address = rtcp.try_address().unwrap().unwrap();
        assert_eq!(address.ttl, Some(24));
        assert_eq!(address.count, None);
        assert!(!rtcp.is_multicast());

        let rtcp = rtcp_attr_iter.next().unwrap().unwrap();
        assert_eq!(rtcp.addrtype, Some(AddrType::Ip6));
        assert_eq!(rtcp.connection_address.as_deref(), Some("::1"));
        assert_eq!(
            rtcp.try_parse_connection_ip_address().unwrap().unwrap(),
            IpAddr::V6(Ipv6Addr::LOCALHOST),
        );

        let rtcp = rtcp_attr_iter.next().unwrap().unwrap();
        assert_eq!(rtcp.addrtype, Some(AddrType::Other("NONIP".to_string())));
        assert_eq!(rtcp.connection_address.as_deref(), Some("non-IP"));
        assert_eq!(
            rtcp.try_parse_connection_ip_address().unwrap().unwrap_err(),
            "non-IP",
        );

        // RFC 3605: the address part is optional.
        let rtcp = rtcp_attr_iter.next().unwrap().unwrap();
        assert_eq!(rtcp.port, 53020);
        assert_eq!(rtcp.nettype, None);
        assert_eq!(rtcp.addrtype, None);
        assert_eq!(rtcp.connection_address, None);
        assert_eq!(rtcp.try_parse_connection_ip_address(), None);
        assert_eq!(rtcp.try_address(), None);
        assert!(!rtcp.is_multicast());
        assert_eq!(rtcp.to_string(), "53020");
    }

    #[test]
    fn rtcp_multicast_address_helpers() {
        // RFC 3605: a=rtcp reuses the SDP connection-address token, so the
        // multicast `address/ttl[/count]` notation of RFC 8866, section 5.7
        // may also be used here. Parsing the notation itself is covered by
        // `connection_try_address`, here only its use through `a=rtcp` and
        // the address family inference that is specific to `a=rtcp`.
        let rtcp = "5000 IN IP4 233.252.0.1/127/3".parse::<Rtcp>().unwrap();
        assert!(rtcp.is_multicast());
        assert_eq!(
            rtcp.try_address().unwrap().unwrap(),
            ConnectionAddress {
                ip: Ipv4Addr::new(233, 252, 0, 1).into(),
                ttl: Some(127),
                count: Some(3),
            }
        );

        // Without `addrtype` it is inferred from the address: IPv4 gets a
        // TTL, IPv6 the address count.
        let mut rtcp = Rtcp::with_port(5000);
        rtcp.connection_address = Some("224.2.1.1/16".to_string());
        let address = rtcp.try_address().unwrap().unwrap();
        assert_eq!(address.ttl, Some(16));
        assert_eq!(address.count, None);

        let mut rtcp = Rtcp::with_port(5000);
        rtcp.connection_address = Some("ff12::5/3".to_string());
        let address = rtcp.try_address().unwrap().unwrap();
        assert_eq!(address.ttl, None);
        assert_eq!(address.count, Some(3));

        let rtcp = "5000 IN IP6 ff12::5/3".parse::<Rtcp>().unwrap();
        assert!(rtcp.is_ipv6());
        assert!(!rtcp.is_ipv4());
        assert_eq!(rtcp.try_is_multicast(), Some(Ok(true)));

        // Without the address part the multicast and family helpers report
        // `None`/`false`, `a=rtcp` only carries the port in that case.
        let rtcp = Rtcp::with_port(5000);
        assert_eq!(rtcp.try_is_multicast(), None);
        assert!(!rtcp.is_multicast());
        assert!(!rtcp.is_ipv4());
        assert!(!rtcp.is_ipv6());

        // FQDN addresses are not parseable as `IpAddr`.
        let rtcp = "5000 IN IP4 rtcp.example.com".parse::<Rtcp>().unwrap();
        assert!(!rtcp.is_multicast());
        assert!(!rtcp.is_ipv4());
        assert_eq!(
            rtcp.try_is_multicast(),
            Some(Err(ConnectionAddressError::InvalidAddress(
                "rtcp.example.com".to_string()
            )))
        );
    }

    #[test]
    fn parse_rtcp_attribute_whitespace() {
        // Runs of spaces are a single separator, like in o= and c= lines,
        // and empty fields are rejected instead of ending up as e.g. an
        // empty `nettype` or `addrtype`.
        assert_eq!(
            "6000  IN IP4 127.0.0.1".parse::<Rtcp>().unwrap(),
            Rtcp::new(6000, NetType::In, AddrType::Ip4, "127.0.0.1")
        );
        assert_eq!(
            "6001 IN  IP4 127.0.0.1 ".parse::<Rtcp>().unwrap(),
            Rtcp::new(6001, NetType::In, AddrType::Ip4, "127.0.0.1")
        );
        assert_eq!("53020 ".parse::<Rtcp>().unwrap(), Rtcp::with_port(53020));

        assert!("6002 IN  127.0.0.1".parse::<Rtcp>().is_err());
        assert!("6003 IN IP4 127.0.0.1 extra".parse::<Rtcp>().is_err());
    }

    #[test]
    fn parse_rtcp_nettype_and_addrtype_must_be_tokens() {
        // RFC 3605 reuses the SDP nettype and addrtype tokens (RFC 8866,
        // section 9), so reject other values like the o= and c= parsers do.
        assert_eq!(
            "6000 a<b IP4 127.0.0.1".parse::<Rtcp>().unwrap_err(),
            AttributeError::InvalidParamValue {
                param: "Network type".to_string(),
                val: "a<b".to_string(),
                attr: "rtcp".to_string(),
            }
        );
        assert_eq!(
            "6000 IN IP4/x 127.0.0.1".parse::<Rtcp>().unwrap_err(),
            AttributeError::InvalidParamValue {
                param: "Address type".to_string(),
                val: "IP4/x".to_string(),
                attr: "rtcp".to_string(),
            }
        );
    }

    #[test]
    fn parse_rid_attribute() {
        // RFC 8851 examples.
        let rid: Rid = "5 send pt=99,102;max-br=64000".parse().unwrap();
        assert_eq!(
            rid,
            Rid::with_params("5", RidDirection::Send, ["pt=99,102", "max-br=64000"])
        );
        assert_eq!(rid.to_string(), "5 send pt=99,102;max-br=64000");

        let rid: Rid = "6 send pt=100,97,101,102".parse().unwrap();
        assert_eq!(
            rid,
            Rid::with_params("6", RidDirection::Send, ["pt=100,97,101,102"])
        );

        let rid: Rid = "f recv max-br=19.5;apt=100".parse().unwrap();
        assert_eq!(
            rid,
            Rid::with_params("f", RidDirection::Recv, ["max-br=19.5", "apt=100"])
        );
        assert_eq!(rid.to_string(), "f recv max-br=19.5;apt=100");

        // Without parameters, and with a valueless parameter.
        let rid: Rid = "1 recv".parse().unwrap();
        assert_eq!(rid.direction, RidDirection::Recv);
        assert!(rid.params.is_empty());
        assert_eq!(rid.to_string(), "1 recv");
        assert_eq!(
            "2 send max-width".parse::<Rid>().unwrap(),
            Rid::with_params("2", RidDirection::Send, ["max-width"])
        );

        // Trailing separators are tolerated, direction is case-insensitive.
        assert_eq!(
            "2 SEND pt=99;".parse::<Rid>().unwrap(),
            Rid::with_params("2", RidDirection::Send, ["pt=99"])
        );

        for invalid in [
            "",
            "1",
            " send",
            // The ID is restricted to alphanumeric, "-" and "_"
            // (RFC 8851, section 10):
            "1! send",
            "id:1 recv",
            "1 up",
            "1 send x y",
            "1 send pt=1;max br=2",
        ] {
            assert!(
                invalid.parse::<Rid>().is_err(),
                "expected error for {:?}",
                invalid
            );
        }
    }

    #[test]
    fn parse_key_mgmt_attribute() {
        let key_mgmt: KeyMgmt = "mikey AAAAIklkAAAAdGV4dHRleHR0ZXh0".parse().unwrap();
        assert_eq!(
            key_mgmt,
            KeyMgmt::with_data(KeyMgmtMethod::Mikey, "AAAAIklkAAAAdGV4dHRleHR0ZXh0")
        );
        assert_eq!(key_mgmt.to_string(), "mikey AAAAIklkAAAAdGV4dHRleHR0ZXh0");

        // Unknown methods are kept verbatim; KMPIDs are case-sensitive
        // (RFC 4567 section 3), so `MIKEY` is not the `mikey` method.
        for method in ["rawurl", "MIKEY", "internal"] {
            let key_mgmt: KeyMgmt = format!("{} data", method).parse().unwrap();
            assert_eq!(key_mgmt.method, KeyMgmtMethod::Other(method.to_string()));
            assert_eq!(key_mgmt.data.as_deref(), Some("data"));
            assert_eq!(key_mgmt.to_string(), format!("{} data", method));
        }

        // Method without data.
        let key_mgmt: KeyMgmt = "internal".parse().unwrap();
        assert_eq!(
            key_mgmt,
            KeyMgmt::new(KeyMgmtMethod::Other("internal".to_string()))
        );
        assert_eq!(key_mgmt.to_string(), "internal");

        // Data is kept verbatim, including inner whitespace.
        let key_mgmt: KeyMgmt = "mikey bar  baz".parse().unwrap();
        assert_eq!(key_mgmt.data.as_deref(), Some("bar  baz"));
        assert_eq!(key_mgmt.to_string(), "mikey bar  baz");

        assert!("".parse::<KeyMgmt>().is_err());
        assert!("   ".parse::<KeyMgmt>().is_err());
        // The method is restricted to alphanumeric (RFC 4567, section 3):
        assert!("mi!key data".parse::<KeyMgmt>().is_err());
        assert!("-mikey".parse::<KeyMgmt>().is_err());
    }

    #[test]
    fn parse_remote_candidate_attribute() {
        let candidates: RemoteCandidates = "1 192.168.1.1 50000".parse().unwrap();
        assert_eq!(
            candidates,
            RemoteCandidates::new([RemoteCandidate::new(
                1,
                "192.168.1.1".parse::<IpAddr>().unwrap(),
                50000
            )])
        );
        assert_eq!(candidates.to_string(), "1 192.168.1.1 50000");

        // Multiple entries in a single attribute (RFC 8839, section 5.2).
        let candidates: RemoteCandidates = "1 192.0.2.3 45664 2 192.0.2.3 45665".parse().unwrap();
        assert_eq!(candidates.0.len(), 2);
        assert_eq!(candidates.0[1].component_id, 2);
        assert_eq!(
            candidates.to_string(),
            "1 192.0.2.3 45664 2 192.0.2.3 45665"
        );

        // IPv6 and the value parsed on its own.
        let candidate: RemoteCandidate = "1 2001:db8::1 9".parse().unwrap();
        assert_eq!(candidate.address, "2001:db8::1".parse::<IpAddr>().unwrap());
        assert_eq!(candidate.to_string(), "1 2001:db8::1 9");

        for invalid in [
            "",
            "1",
            "1 10.0.0.1",
            "x 10.0.0.1 50000",
            "1 x 50000",
            // FQDNs must not be used (RFC 8839, section 5.1).
            "1 example.com 50000",
            "1 10.0.0.1 70000",
            "1 10.0.0.1 50000 2",
        ] {
            assert!(
                invalid.parse::<RemoteCandidates>().is_err(),
                "expected error for {:?}",
                invalid
            );
        }
    }

    #[test]
    fn parse_source_filter_attribute() {
        // RFC 4570, section 3.2 examples.
        let filter: SourceFilter = "incl IN IP4 232.3.4.5 192.0.2.10".parse().unwrap();
        assert_eq!(filter.mode, SourceFilterMode::Incl);
        assert_eq!(filter.nettype, NetType::In);
        assert_eq!(filter.addrtype, SourceFilterAddrType::Ip4);
        assert_eq!(
            filter.destination,
            SourceFilterDestination::Address(SourceFilterAddress::IpAddr(
                "232.3.4.5".parse().unwrap()
            ))
        );
        assert_eq!(
            filter.sources,
            ["192.0.2.10".parse::<SourceFilterAddress>().unwrap()]
        );
        assert_eq!(filter.to_string(), "incl IN IP4 232.3.4.5 192.0.2.10");

        // Unicast destination.
        let filter: SourceFilter = "excl IN IP4 192.0.2.11 192.0.2.10".parse().unwrap();
        assert_eq!(filter.mode, SourceFilterMode::Excl);
        assert_eq!(filter.to_string(), "excl IN IP4 192.0.2.11 192.0.2.10");

        // Destination wildcard.
        let filter: SourceFilter = "incl IN IP4 * 192.0.2.10".parse().unwrap();
        assert_eq!(filter.destination, SourceFilterDestination::Wildcard);
        assert_eq!(filter.to_string(), "incl IN IP4 * 192.0.2.10");

        // Multiple space-separated sources.
        let filter: SourceFilter = "incl IN IP4 224.2.1.1 192.0.2.10 192.0.2.42"
            .parse()
            .unwrap();
        assert_eq!(filter.sources.len(), 2);
        assert_eq!(
            filter.to_string(),
            "incl IN IP4 224.2.1.1 192.0.2.10 192.0.2.42"
        );

        // IPv6.
        let filter: SourceFilter = "incl IN IP6 ff0e::11a 2001:db8::1".parse().unwrap();
        assert_eq!(filter.addrtype, SourceFilterAddrType::Ip6);
        assert_eq!(
            filter.destination,
            SourceFilterDestination::Address(SourceFilterAddress::IpAddr(
                "ff0e::11a".parse().unwrap()
            ))
        );
        assert_eq!(filter.to_string(), "incl IN IP6 ff0e::11a 2001:db8::1");

        // FQDNs with the "*" address type.
        let filter: SourceFilter = "incl IN * channel-1.example.com src-1.example.com"
            .parse()
            .unwrap();
        assert_eq!(filter.addrtype, SourceFilterAddrType::Any);
        assert_eq!(
            filter.destination,
            SourceFilterDestination::Address(SourceFilterAddress::FQDN(
                "channel-1.example.com".to_string()
            ))
        );
        assert_eq!(
            filter.sources,
            [SourceFilterAddress::FQDN("src-1.example.com".to_string())]
        );
        assert_eq!(
            filter.to_string(),
            "incl IN * channel-1.example.com src-1.example.com"
        );

        // Filter mode and address type matching is case-insensitive.
        let filter: SourceFilter = "EXCL IN ip6 ff0e::11a 2001:db8::1".parse().unwrap();
        assert_eq!(filter.mode, SourceFilterMode::Excl);
        assert_eq!(filter.addrtype, SourceFilterAddrType::Ip6);

        for invalid in [
            "",
            "incl",
            "incl IN",
            "incl IN IP4",
            "incl IN IP4 232.3.4.5",
            // No /ttl or /number of addresses suffixes on the destination
            // (RFC 4570 section 3.1):
            "incl IN IP4 232.3.4.5/127 192.0.2.10",
            // The "*" address type only with FQDN destinations (section 3.1):
            "incl IN * 232.3.4.5 192.0.2.10",
            // The "*" wildcard is not allowed in the source list (appendix A):
            "incl IN IP4 232.3.4.5 *",
            "unknown IN IP4 232.3.4.5 192.0.2.10",
            // The network type is a token (RFC 4570 appendix A):
            "incl IN(IP4 232.3.4.5 192.0.2.10",
            "incl IN IP8 232.3.4.5 192.0.2.10",
        ] {
            assert!(
                invalid.parse::<SourceFilter>().is_err(),
                "expected error for {:?}",
                invalid
            );
        }
    }

    #[test]
    fn parse_mid_attribute() {
        let mid: Mid = "1".parse().unwrap();
        assert_eq!(mid, Mid("1".to_string()));
        assert_eq!(mid.to_string(), "1");

        let attribute: Attribute = mid.clone().into();
        assert_eq!(attribute.attribute, "mid");
        assert_eq!(attribute.value.as_deref(), Some("1"));

        // Media descriptions commonly use opaque, browser-style tags.
        let mid: Mid = "v2R1d1".parse().unwrap();
        assert_eq!(mid.to_string(), "v2R1d1");

        for invalid in [
            "", " ", // The identification tag is a token (RFC 8866, section 5).
            "1 2", "a:b",
        ] {
            assert!(
                invalid.parse::<Mid>().is_err(),
                "expected error for {:?}",
                invalid
            );
        }
    }

    #[test]
    fn parse_rtcp_mux_attribute() {
        assert_eq!("".parse::<RtcpMux>().unwrap(), RtcpMux);

        let attribute: Attribute = RtcpMux.into();
        assert_eq!(attribute.attribute, "rtcp-mux");
        assert_eq!(attribute.value, None);

        // A property attribute must not carry a value.
        assert!("1".parse::<RtcpMux>().is_err());

        let sdp = "v=0\r
o=alice 3203093520 3203093520 IN IP4 host.example.com\r
s=Property attribute test\r
t=3203130148 3203137348\r
m=audio 49170 RTP/AVP 0\r
a=rtcp-mux\r
";
        let parsed = Session::parse(sdp.as_bytes()).unwrap();
        assert_eq!(
            parsed.medias[0].get_first_attribute_typed::<RtcpMux>(),
            Some(Ok(RtcpMux))
        );
    }

    #[test]
    fn parse_rtcp_mux_only_attribute() {
        assert!(matches!("".parse::<RtcpMuxOnly>(), Ok(RtcpMuxOnly)));

        let attribute: Attribute = RtcpMuxOnly.into();
        assert_eq!(attribute.attribute, "rtcp-mux-only");
        assert_eq!(attribute.value, None);

        // A property attribute must not carry a value.
        assert!("1".parse::<RtcpMuxOnly>().is_err());
    }

    #[test]
    fn parse_rtcp_rsize_attribute() {
        assert!(matches!("".parse::<RtcpRsize>(), Ok(RtcpRsize)));

        let attribute: Attribute = RtcpRsize.into();
        assert_eq!(attribute.attribute, "rtcp-rsize");
        assert_eq!(attribute.value, None);

        // A property attribute must not carry a value.
        assert!("1".parse::<RtcpRsize>().is_err());
    }

    #[test]
    fn parse_ice_lite_attribute() {
        assert!(matches!("".parse::<IceLite>(), Ok(IceLite)));

        let attribute: Attribute = IceLite.into();
        assert_eq!(attribute.attribute, "ice-lite");
        assert_eq!(attribute.value, None);

        // A property attribute must not carry a value.
        assert!("1".parse::<IceLite>().is_err());
    }

    #[test]
    fn parse_ice_ufrag_attribute() {
        let ufrag: IceUfrag = "EpGh".parse().unwrap();
        assert_eq!(ufrag, IceUfrag("EpGh".to_string()));
        assert_eq!(ufrag.to_string(), "EpGh");

        let attribute: Attribute = ufrag.into();
        assert_eq!(attribute.attribute, "ice-ufrag");
        assert_eq!(attribute.value.as_deref(), Some("EpGh"));

        // All ICE characters are allowed, including "+" and "/" (RFC 5245,
        // section 15.1).
        assert_eq!("a+Z/9".parse::<IceUfrag>().unwrap().to_string(), "a+Z/9");

        // The 256 characters upper bound.
        assert!("a".repeat(256).parse::<IceUfrag>().is_ok());

        let too_long = "a".repeat(257);
        for invalid in [
            "",
            "abc",             // shorter than 4 characters
            too_long.as_str(), // longer than 256 characters
            "Ep-Gh",           // "-" is not an ICE character
            "Ep Gh",           // neither is the space
            "\u{30b0}pGh",     // non-ASCII
        ] {
            assert!(
                invalid.parse::<IceUfrag>().is_err(),
                "expected error for {:?}",
                invalid
            );
        }
    }

    #[test]
    fn parse_ice_pwd_attribute() {
        let password = "aq1s2dq3w4er5ty6ui7p8o9i0u";
        let pwd: IcePwd = password.parse().unwrap();
        assert_eq!(pwd, IcePwd(password.to_string()));
        assert_eq!(pwd.to_string(), password);

        let attribute: Attribute = pwd.into();
        assert_eq!(attribute.attribute, "ice-pwd");
        assert_eq!(attribute.value.as_deref(), Some(password));

        // The shortest and longest valid passwords (RFC 5245, section 15.4).
        let shortest = "a".repeat(22);
        assert_eq!(shortest.parse::<IcePwd>().unwrap().to_string(), shortest);
        assert!("a".repeat(256).parse::<IcePwd>().is_ok());

        let too_long = "a".repeat(257);
        for invalid in [
            "",
            "a".repeat(21).as_str(),          // shorter than 22 characters
            too_long.as_str(),                // longer than 256 characters
            "abcdefghijklmnopqr-stu",         // "-" is not an ICE character
            "\u{30b0}bcdefghijklmnopqrstuvw", // non-ASCII
        ] {
            assert!(
                invalid.parse::<IcePwd>().is_err(),
                "expected error for {:?}",
                invalid
            );
        }
    }

    #[test]
    fn parse_ice_options_attribute() {
        let options: IceOptions = "trickle".parse().unwrap();
        assert_eq!(options, IceOptions::new(["trickle"]));
        assert_eq!(options.to_string(), "trickle");

        // Multiple tags in a single attribute (RFC 5245, section 15.5).
        let options: IceOptions = "trickle renomination".parse().unwrap();
        assert_eq!(options, IceOptions::new(["trickle", "renomination"]));
        assert_eq!(options.to_string(), "trickle renomination");

        let attribute: Attribute = options.into();
        assert_eq!(attribute.attribute, "ice-options");
        assert_eq!(attribute.value.as_deref(), Some("trickle renomination"));

        for invalid in ["", "   ", "tr-ickle"] {
            assert!(
                invalid.parse::<IceOptions>().is_err(),
                "expected error for {:?}",
                invalid
            );
        }
    }

    #[test]
    fn parse_end_of_candidates_attribute() {
        assert!(matches!("".parse::<EndOfCandidates>(), Ok(EndOfCandidates)));

        let attribute: Attribute = EndOfCandidates.into();
        assert_eq!(attribute.attribute, "end-of-candidates");
        assert_eq!(attribute.value, None);

        // A property attribute must not carry a value.
        assert!("1".parse::<EndOfCandidates>().is_err());
    }

    #[test]
    fn parse_msid_attribute() {
        // RFC 8830, section 2 example.
        let msid: Msid = "examplefoo examplebar".parse().unwrap();
        assert_eq!(msid, Msid::new("examplefoo", Some("examplebar")));
        assert_eq!(msid.to_string(), "examplefoo examplebar");

        let attribute: Attribute = msid.into();
        assert_eq!(attribute.attribute, "msid");
        assert_eq!(attribute.value.as_deref(), Some("examplefoo examplebar"));

        // The appdata is optional; "-" means "no MediaStream" and is a valid
        // token (RFC 8830, section 3).
        let msid: Msid = "-".parse().unwrap();
        assert_eq!(msid, Msid::new("-", None::<&str>));
        assert_eq!(msid.to_string(), "-");

        let too_long = "a".repeat(65);
        for invalid in [
            "",
            too_long.as_str(), // longer than 64 characters
            "foo \u{fffd}",    // non-token character
            "foo bar baz",     // more than two fields
        ] {
            assert!(
                invalid.parse::<Msid>().is_err(),
                "expected error for {:?}",
                invalid
            );
        }
    }

    #[test]
    fn parse_sctp_port_attribute() {
        // RFC 8841, section 5.2 example.
        let port: SctpPort = "5000".parse().unwrap();
        assert_eq!(port, SctpPort(5000));
        assert_eq!(port.to_string(), "5000");

        let attribute: Attribute = port.into();
        assert_eq!(attribute.attribute, "sctp-port");
        assert_eq!(attribute.value.as_deref(), Some("5000"));

        // The port range includes 0 and 65535 (RFC 8841, section 5.2).
        assert_eq!("0".parse::<SctpPort>().unwrap(), SctpPort(0));
        assert_eq!("65535".parse::<SctpPort>().unwrap(), SctpPort(65535));

        for invalid in [
            "", "65536",  // out of range
            "99999",  // 5 digits but out of range
            "05000",  // leading zeroes must not be used
            "500000", // more than 5 digits
            "abc", "50a",
        ] {
            assert!(
                invalid.parse::<SctpPort>().is_err(),
                "expected error for {:?}",
                invalid
            );
        }
    }

    #[test]
    fn parse_max_message_size_attribute() {
        // RFC 8841, section 6.2 example.
        let size: MaxMessageSize = "100000".parse().unwrap();
        assert_eq!(size, MaxMessageSize(100000));
        assert_eq!(size.to_string(), "100000");

        let attribute: Attribute = size.into();
        assert_eq!(attribute.attribute, "max-message-size");
        assert_eq!(attribute.value.as_deref(), Some("100000"));

        // Zero means messages of any size (RFC 8841, section 6.1).
        assert_eq!("0".parse::<MaxMessageSize>().unwrap(), MaxMessageSize(0));

        let too_large = "1".repeat(21);
        for invalid in [
            "",
            "01", // leading zeroes must not be used
            "1_000",
            "abc",
            "10a",
            too_large.as_str(), // larger than u64::MAX
        ] {
            assert!(
                invalid.parse::<MaxMessageSize>().is_err(),
                "expected error for {:?}",
                invalid
            );
        }
    }

    #[test]
    fn parse_sctpmap_attribute() {
        // Real-world legacy syntax.
        let map: SctpMap = "5000 webrtc-datachannel 256".parse().unwrap();
        assert_eq!(map, SctpMap::new(5000, "webrtc-datachannel", Some(256)));
        assert_eq!(map.to_string(), "5000 webrtc-datachannel 256");

        let attribute: Attribute = map.into();
        assert_eq!(attribute.attribute, "sctpmap");
        assert_eq!(
            attribute.value.as_deref(),
            Some("5000 webrtc-datachannel 256")
        );

        // The stream count is optional and zero is allowed.
        let map: SctpMap = "9 webrtc-datachannel".parse().unwrap();
        assert_eq!(map.streams, None);
        assert_eq!(map.to_string(), "9 webrtc-datachannel");
        assert_eq!("0 app 0".parse::<SctpMap>().unwrap().streams, Some(0));

        for invalid in [
            "",
            "5000",               // application missing
            "65536 app",          // port out of range
            "05000 app",          // leading zeroes
            "app app",            // port not a number
            "5000 app 70000",     // stream count out of range
            "5000 a:pp",          // application not a token
            "5000 app 256 extra", // trailing item
        ] {
            assert!(
                invalid.parse::<SctpMap>().is_err(),
                "expected error for {:?}",
                invalid
            );
        }
    }
}