sip-header 0.3.0

//! SIP Security mechanism parser (RFC 3329).
//!
//! Used by Security-Client, Security-Server, and Security-Verify headers.

use std::fmt;

/// A parsed security mechanism entry: `mechanism-name *(SEMI mech-params)`.
#[derive(Debug, Clone, PartialEq, Eq)]
#[non_exhaustive]
pub struct SipSecurityMechanism {
    mechanism: String,
    params: Vec<(String, Option<String>)>,
}

impl SipSecurityMechanism {
    /// The mechanism name (e.g. `"digest"`, `"tls"`, `"ipsec-ike"`).
    pub fn mechanism(&self) -> &str {
        &self.mechanism
    }

    /// All parameters as `(key, optional_value)` pairs.
    pub fn params(&self) -> &[(String, Option<String>)] {
        &self.params
    }

    /// Look up a parameter by key (case-insensitive).
    pub fn param(&self, key: &str) -> Option<Option<&str>> {
        self.params
            .iter()
            .find(|(k, _)| k.eq_ignore_ascii_case(key))
            .map(|(_, v)| v.as_deref())
    }

    /// The `q` preference value, if present.
    pub fn q(&self) -> Option<&str> {
        self.param("q")
            .flatten()
    }

    /// The `d-alg` parameter, if present.
    pub fn d_alg(&self) -> Option<&str> {
        self.param("d-alg")
            .flatten()
    }

    /// The `d-qop` parameter, if present.
    pub fn d_qop(&self) -> Option<&str> {
        self.param("d-qop")
            .flatten()
    }
}

impl fmt::Display for SipSecurityMechanism {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{}", self.mechanism)?;
        for (key, value) in &self.params {
            match value {
                Some(v) => write!(f, ";{key}={v}")?,
                None => write!(f, ";{key}")?,
            }
        }
        Ok(())
    }
}

/// Errors from parsing a security mechanism header value.
#[derive(Debug, Clone, PartialEq, Eq)]
#[non_exhaustive]
pub enum SipSecurityError {
    /// The input string was empty or whitespace-only.
    Empty,
    /// A mechanism entry could not be parsed.
    InvalidFormat(String),
}

impl fmt::Display for SipSecurityError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Self::Empty => write!(f, "empty security mechanism value"),
            Self::InvalidFormat(raw) => {
                write!(f, "invalid security mechanism: {raw}")
            }
        }
    }
}

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

fn parse_mechanism(raw: &str) -> Result<SipSecurityMechanism, SipSecurityError> {
    let raw = raw.trim();
    if raw.is_empty() {
        return Err(SipSecurityError::InvalidFormat(raw.to_string()));
    }

    let (mechanism_part, params_part) = match raw.split_once(';') {
        Some((m, p)) => (m.trim(), Some(p)),
        None => (raw, None),
    };

    if mechanism_part.is_empty() {
        return Err(SipSecurityError::InvalidFormat(raw.to_string()));
    }

    let mechanism = mechanism_part.to_ascii_lowercase();
    let mut params = Vec::new();

    if let Some(params_str) = params_part {
        for segment in params_str.split(';') {
            let segment = segment.trim();
            if segment.is_empty() {
                continue;
            }
            if let Some((key, value)) = segment.split_once('=') {
                params.push((
                    key.trim()
                        .to_ascii_lowercase(),
                    Some(
                        value
                            .trim()
                            .trim_matches('"')
                            .to_string(),
                    ),
                ));
            } else {
                params.push((segment.to_ascii_lowercase(), None));
            }
        }
    }

    Ok(SipSecurityMechanism { mechanism, params })
}

/// Parsed security mechanism header value.
#[derive(Debug, Clone, PartialEq, Eq)]
#[non_exhaustive]
pub struct SipSecurity(Vec<SipSecurityMechanism>);

impl SipSecurity {
    /// Parse a comma-separated security mechanism value.
    pub fn parse(raw: &str) -> Result<Self, SipSecurityError> {
        let raw = raw.trim();
        if raw.is_empty() {
            return Err(SipSecurityError::Empty);
        }
        let entries: Vec<_> = crate::split_comma_entries(raw)
            .into_iter()
            .map(parse_mechanism)
            .collect::<Result<_, _>>()?;
        if entries.is_empty() {
            return Err(SipSecurityError::Empty);
        }
        Ok(Self(entries))
    }

    /// The parsed entries as a slice.
    pub fn entries(&self) -> &[SipSecurityMechanism] {
        &self.0
    }

    /// Consume self and return entries as a `Vec`.
    pub fn into_entries(self) -> Vec<SipSecurityMechanism> {
        self.0
    }

    /// Number of entries.
    pub fn len(&self) -> usize {
        self.0
            .len()
    }

    /// Returns `true` if there are no entries.
    pub fn is_empty(&self) -> bool {
        self.0
            .is_empty()
    }
}

impl fmt::Display for SipSecurity {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        crate::fmt_joined(f, &self.0, ", ")
    }
}

impl_from_str_via_parse!(SipSecurity, SipSecurityError);

impl<'a> IntoIterator for &'a SipSecurity {
    type Item = &'a SipSecurityMechanism;
    type IntoIter = std::slice::Iter<'a, SipSecurityMechanism>;

    fn into_iter(self) -> Self::IntoIter {
        self.0
            .iter()
    }
}

impl IntoIterator for SipSecurity {
    type Item = SipSecurityMechanism;
    type IntoIter = std::vec::IntoIter<SipSecurityMechanism>;

    fn into_iter(self) -> Self::IntoIter {
        self.0
            .into_iter()
    }
}

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

    #[test]
    fn single_mechanism() {
        let sec = SipSecurity::parse("digest;d-qop=auth-int;q=0.1").unwrap();
        assert_eq!(sec.len(), 1);
        assert_eq!(sec.entries()[0].mechanism(), "digest");
        assert_eq!(sec.entries()[0].d_qop(), Some("auth-int"));
        assert_eq!(sec.entries()[0].q(), Some("0.1"));
    }

    #[test]
    fn multiple_mechanisms() {
        let sec = SipSecurity::parse("tls;q=0.2, digest;d-qop=auth;q=0.1").unwrap();
        assert_eq!(sec.len(), 2);
        assert_eq!(sec.entries()[0].mechanism(), "tls");
        assert_eq!(sec.entries()[1].mechanism(), "digest");
    }

    #[test]
    fn mechanism_no_params() {
        let sec = SipSecurity::parse("tls").unwrap();
        assert_eq!(sec.len(), 1);
        assert_eq!(sec.entries()[0].mechanism(), "tls");
        assert!(sec.entries()[0]
            .params()
            .is_empty());
    }

    #[test]
    fn empty_input() {
        assert!(matches!(
            SipSecurity::parse(""),
            Err(SipSecurityError::Empty)
        ));
    }

    #[test]
    fn display_roundtrip() {
        let raw = "digest;d-qop=auth;q=0.1";
        let sec = SipSecurity::parse(raw).unwrap();
        assert_eq!(sec.to_string(), raw);
    }

    #[test]
    fn from_str() {
        let sec: SipSecurity = "tls;q=0.2"
            .parse()
            .unwrap();
        assert_eq!(sec.len(), 1);
    }

    #[test]
    fn d_alg_param() {
        let sec = SipSecurity::parse("digest;d-alg=MD5;d-qop=auth").unwrap();
        assert_eq!(sec.entries()[0].d_alg(), Some("MD5"));
    }
}