freeswitch-sofia-trace-parser 0.10.1

use std::borrow::Cow;

use crate::frame::ParseError;
use crate::types::SipMessageType;

/// A start line still pointing into the message it came from.
pub(crate) enum StartLineRef<'a> {
    Request { method: &'a [u8], uri: &'a [u8] },
    Response { code: u16, reason: &'a [u8] },
}

pub(crate) fn parse_first_line(line: &[u8]) -> Result<SipMessageType, ParseError> {
    Ok(match parse_first_line_ref(line)? {
        StartLineRef::Request { method, uri } => SipMessageType::Request {
            method: bytes_to_string(method),
            uri: bytes_to_string(uri),
        },
        StartLineRef::Response { code, reason } => SipMessageType::Response {
            code,
            reason: bytes_to_string(reason),
        },
    })
}

pub(crate) fn parse_first_line_ref(line: &[u8]) -> Result<StartLineRef<'_>, ParseError> {
    if line.starts_with(b"SIP/2.0 ") {
        return parse_status_line(line);
    }
    parse_request_line(line)
}

fn parse_status_line(line: &[u8]) -> Result<StartLineRef<'_>, ParseError> {
    // SIP/2.0 <code> <reason>
    let after_version = &line[8..]; // skip "SIP/2.0 "

    let space = memchr::memchr(b' ', after_version)
        .ok_or_else(|| ParseError::InvalidMessage("no space after status code".into()))?;
    let code_bytes = &after_version[..space];
    let code: u16 = std::str::from_utf8(code_bytes)
        .map_err(|_| ParseError::InvalidMessage("non-UTF-8 status code".into()))?
        .parse()
        .map_err(|_| ParseError::InvalidMessage("invalid status code".into()))?;

    let reason = &after_version[space + 1..];

    Ok(StartLineRef::Response { code, reason })
}

fn is_token_byte(c: u8) -> bool {
    c.is_ascii_alphanumeric() || b"-._!%*+`'~".contains(&c)
}

fn is_sip_token(b: &[u8]) -> bool {
    !b.is_empty() && b.iter().copied().all(is_token_byte)
}

/// Whether a buffer opens on a SIP start line, for a reader that may not hold
/// the whole line yet.
pub(crate) enum SipStart {
    /// The first line is a request line or a status line.
    Yes,
    /// The first line cannot become either, however it continues.
    No,
    /// No CRLF yet, and what is buffered is still a possible prefix.
    NeedMore,
}

/// The start-line grammar [`parse_first_line_ref`] accepts, answered on bytes
/// that may still be arriving. Level 2 resynchronises on this, so anything it
/// accepts is a message Level 3 parses.
pub(crate) fn sip_start(buf: &[u8]) -> SipStart {
    if buf.starts_with(b"SIP/2.0 ") {
        return SipStart::Yes;
    }
    let mut method_end = 0;
    while method_end < buf.len() && is_token_byte(buf[method_end]) {
        method_end += 1;
    }
    if method_end == buf.len() {
        return SipStart::NeedMore;
    }
    if method_end == 0 || buf[method_end] != b' ' {
        return if b"SIP/2.0 ".starts_with(buf) {
            SipStart::NeedMore
        } else {
            SipStart::No
        };
    }

    // A start line holds no CR or LF of its own, so a lone one rules it out and
    // a trailing CR is the terminator still arriving.
    let rest = &buf[method_end + 1..];
    let mut last_space = None;
    let mut i = 0;
    while i < rest.len() {
        match rest[i] {
            b'\r' => match rest.get(i + 1) {
                Some(b'\n') => break,
                Some(_) => return SipStart::No,
                None => return SipStart::NeedMore,
            },
            b'\n' => return SipStart::No,
            b' ' => last_space = Some(i),
            _ => {}
        }
        i += 1;
    }
    if i == rest.len() {
        return SipStart::NeedMore;
    }
    match last_space {
        Some(space) if space > 0 && &rest[space + 1..i] == b"SIP/2.0" => SipStart::Yes,
        _ => SipStart::No,
    }
}

/// A syntactically valid header first line: a nonempty SIP token, optionally
/// followed by HCOLON whitespace (SP / HTAB), then a colon.
pub(crate) fn is_header_line(line: &[u8]) -> bool {
    let Some(colon) = memchr::memchr(b':', line) else {
        return false;
    };
    let mut name = &line[..colon];
    while let [rest @ .., b' ' | b'\t'] = name {
        name = rest;
    }
    is_sip_token(name)
}

fn parse_request_line(line: &[u8]) -> Result<StartLineRef<'_>, ParseError> {
    // <METHOD> <URI> SIP/2.0
    let first_space = memchr::memchr(b' ', line)
        .ok_or_else(|| ParseError::InvalidMessage("no space in request line".into()))?;
    let method = &line[..first_space];

    if !is_sip_token(method) {
        return Err(ParseError::InvalidMessage(format!(
            "invalid SIP method: {:?}",
            String::from_utf8_lossy(method)
        )));
    }
    let rest = &line[first_space + 1..];

    let last_space = memchr::memrchr(b' ', rest)
        .ok_or_else(|| ParseError::InvalidMessage("no SIP version in request line".into()))?;
    let version = &rest[last_space + 1..];
    if version != b"SIP/2.0" {
        return Err(ParseError::InvalidMessage(format!(
            "expected SIP/2.0, got {:?}",
            String::from_utf8_lossy(version)
        )));
    }
    let uri = &rest[..last_space];

    Ok(StartLineRef::Request { method, uri })
}

pub(crate) fn bytes_to_str(b: &[u8]) -> Cow<'_, str> {
    match std::str::from_utf8(b) {
        Ok(s) => Cow::Borrowed(s),
        Err(_) => String::from_utf8_lossy(b),
    }
}

fn bytes_to_string(b: &[u8]) -> String {
    bytes_to_str(b).into_owned()
}

#[cfg(test)]
mod tests {
    use crate::sip::test_support::make_sip_message;
    use crate::types::SipMessageType;

    #[test]
    fn status_line_with_long_reason() {
        let content = b"SIP/2.0 486 Busy Here\r\n\
            Call-ID: busy\r\n\
            \r\n";
        let msg = make_sip_message(content);
        let parsed = msg.parse().unwrap();

        assert_eq!(
            parsed.message_type,
            SipMessageType::Response {
                code: 486,
                reason: "Busy Here".into()
            }
        );
    }

    #[test]
    fn request_with_complex_uri() {
        let content = b"INVITE sip:+15551234567@gateway.example.com;transport=tcp SIP/2.0\r\n\
            Call-ID: complex-uri\r\n\
            \r\n";
        let msg = make_sip_message(content);
        let parsed = msg.parse().unwrap();

        assert_eq!(
            parsed.message_type,
            SipMessageType::Request {
                method: "INVITE".into(),
                uri: "sip:+15551234567@gateway.example.com;transport=tcp".into()
            }
        );
    }

    #[test]
    fn error_no_space_in_request_line() {
        let content = b"INVALID\r\n\r\n";
        let msg = make_sip_message(content);
        let result = msg.parse();
        assert!(result.is_err());
    }

    #[test]
    fn parse_request_rejects_xml_method() {
        let content =
            b"</confInfo:conference-info>NOTIFY sip:user@host SIP/2.0\r\nContent-Length: 0\r\n\r\n";
        let msg = make_sip_message(content);
        assert!(msg.parse().is_err(), "should reject XML-prefixed method");
    }

    #[test]
    fn parse_request_rejects_method_with_angle_brackets() {
        let content = b"<xml>BYE sip:host SIP/2.0\r\n\r\n";
        let msg = make_sip_message(content);
        assert!(msg.parse().is_err());
    }

    #[test]
    fn parse_request_accepts_extension_method() {
        let content = b"CUSTOM-METHOD sip:host SIP/2.0\r\nContent-Length: 0\r\n\r\n";
        let msg = make_sip_message(content);
        let parsed = msg.parse().unwrap();
        assert_eq!(
            parsed.message_type,
            SipMessageType::Request {
                method: "CUSTOM-METHOD".into(),
                uri: "sip:host".into()
            }
        );
    }

    #[test]
    fn method_with_backtick_is_a_token() {
        let msg = make_sip_message(b"X-P`ING sip:host SIP/2.0\r\nCSeq: 1 X-P`ING\r\n\r\n");
        assert_eq!(msg.parse().unwrap().method(), Some("X-P`ING"));
    }
}