sip-header 0.3.6

//! RFC 4538 `Target-Dialog` header parser.

use std::fmt;

use crate::replaces::{decode_uri_header_value, parse_dialog_id, write_params, DialogIdError};

/// Error parsing a Target-Dialog header.
#[derive(Debug, Clone, PartialEq, Eq)]
#[non_exhaustive]
pub enum SipTargetDialogError {
    /// The Target-Dialog header value is empty.
    Empty,
    /// The Target-Dialog header value has an invalid format.
    InvalidFormat(String),
}

impl fmt::Display for SipTargetDialogError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Self::Empty => write!(f, "Target-Dialog header is empty"),
            Self::InvalidFormat(msg) => write!(f, "Invalid Target-Dialog format: {}", msg),
        }
    }
}

impl std::error::Error for SipTargetDialogError {}

impl From<DialogIdError> for SipTargetDialogError {
    fn from(e: DialogIdError) -> Self {
        match e {
            DialogIdError::Empty => Self::Empty,
            DialogIdError::Invalid(msg) => Self::InvalidFormat(msg),
        }
    }
}

/// A parsed `Target-Dialog` header value (RFC 4538 §7).
///
/// Identifies an existing dialog: Call-ID plus the mandatory `local-tag`
/// and `remote-tag`, both from the perspective of the request recipient.
#[derive(Debug, Clone, PartialEq, Eq)]
#[non_exhaustive]
pub struct SipTargetDialog {
    call_id: String,
    local_tag: String,
    remote_tag: String,
    params: Vec<(String, Option<String>)>,
    uri_header_framing: bool,
}

impl SipTargetDialog {
    /// Parse a wire-form header value: `callid;local-tag=x;remote-tag=y`.
    pub fn parse(raw: &str) -> Result<Self, SipTargetDialogError> {
        let id = parse_dialog_id(raw, "local-tag", "remote-tag", false)?;
        Ok(Self {
            call_id: id.call_id,
            local_tag: id.first_tag,
            remote_tag: id.second_tag,
            params: id.params,
            uri_header_framing: false,
        })
    }

    /// Parse the percent-encoded framing found in a URI header,
    /// e.g. `callid%40host%3Blocal-tag%3Dx%3Bremote-tag%3Dy`.
    ///
    /// Accepts the canonicalised value returned by
    /// [`sip_uri::SipUri::header`]; [`Display`](fmt::Display) re-encodes to
    /// that same canonical form (uppercase hex).
    pub fn parse_uri_header(raw: &str) -> Result<Self, SipTargetDialogError> {
        let decoded = decode_uri_header_value(raw)?;
        let mut parsed = Self::parse(&decoded)?;
        parsed.uri_header_framing = true;
        Ok(parsed)
    }

    /// The Call-ID of the target dialog.
    pub fn call_id(&self) -> &str {
        &self.call_id
    }

    /// The host part of the Call-ID (after `@`), if present.
    pub fn host(&self) -> Option<&str> {
        self.call_id
            .split_once('@')
            .map(|(_, host)| host)
    }

    /// The mandatory `local-tag` value.
    pub fn local_tag(&self) -> &str {
        &self.local_tag
    }

    /// The mandatory `remote-tag` value.
    pub fn remote_tag(&self) -> &str {
        &self.remote_tag
    }

    /// Returns all generic parameters (tags excluded).
    pub fn params(&self) -> &[(String, Option<String>)] {
        &self.params
    }

    /// Returns a specific generic parameter by key (case-insensitive).
    pub fn param(&self, key: &str) -> Option<Option<&str>> {
        let key_lower = key.to_ascii_lowercase();
        self.params
            .iter()
            .find(|(k, _)| k == &key_lower)
            .map(|(_, v)| v.as_deref())
    }

    fn wire_form(&self) -> String {
        let mut s = format!(
            "{};local-tag={};remote-tag={}",
            self.call_id, self.local_tag, self.remote_tag
        );
        write_params(&mut s, &self.params);
        s
    }
}

impl fmt::Display for SipTargetDialog {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        let wire = self.wire_form();
        if self.uri_header_framing {
            f.write_str(&sip_uri::encode_uri_header(&wire))
        } else {
            f.write_str(&wire)
        }
    }
}

impl_from_str_via_parse!(SipTargetDialog, SipTargetDialogError);

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn parse_basic() {
        let t = SipTargetDialog::parse("abc123@203.0.113.5;local-tag=l1;remote-tag=r1").unwrap();
        assert_eq!(t.call_id(), "abc123@203.0.113.5");
        assert_eq!(t.host(), Some("203.0.113.5"));
        assert_eq!(t.local_tag(), "l1");
        assert_eq!(t.remote_tag(), "r1");
    }

    #[test]
    fn missing_local_tag_fails() {
        assert!(SipTargetDialog::parse("abc@example.com;remote-tag=r1").is_err());
    }

    #[test]
    fn missing_remote_tag_fails() {
        assert!(SipTargetDialog::parse("abc@example.com;local-tag=l1").is_err());
    }

    #[test]
    fn empty_fails() {
        assert!(matches!(
            SipTargetDialog::parse(""),
            Err(SipTargetDialogError::Empty)
        ));
    }

    #[test]
    fn generic_params_preserved() {
        let t =
            SipTargetDialog::parse("abc@example.com;local-tag=l1;remote-tag=r1;foo=bar").unwrap();
        assert_eq!(t.param("foo"), Some(Some("bar")));
    }

    #[test]
    fn parse_uri_header_encoded() {
        let t = SipTargetDialog::parse_uri_header(
            "abc123%40203.0.113.5%3Blocal-tag%3Dl1%3Bremote-tag%3Dr1",
        )
        .unwrap();
        assert_eq!(t.host(), Some("203.0.113.5"));
        assert_eq!(t.local_tag(), "l1");
        assert_eq!(t.remote_tag(), "r1");
    }

    #[test]
    fn display_roundtrip_wire() {
        let input = "abc123@203.0.113.5;local-tag=l1;remote-tag=r1;foo=bar";
        let t = SipTargetDialog::parse(input).unwrap();
        assert_eq!(t.to_string(), input);
        assert_eq!(SipTargetDialog::parse(&t.to_string()).unwrap(), t);
    }

    #[test]
    fn display_roundtrip_uri_header() {
        let input = "abc123%40203.0.113.5%3Blocal-tag%3Dl1%3Bremote-tag%3Dr1";
        let t = SipTargetDialog::parse_uri_header(input).unwrap();
        assert_eq!(t.to_string(), input);
    }

    #[test]
    fn from_str_is_wire_framing() {
        let t: SipTargetDialog = "abc123@203.0.113.5;local-tag=l1;remote-tag=r1"
            .parse()
            .unwrap();
        assert_eq!(t.local_tag(), "l1");
    }
}