use crate::rtp::SSRC;

#[derive(Debug, thiserror::Error)]
pub enum Error {
    #[error("packet truncated")]
    Truncated,
    #[error("unsupported version")]
    Version,
}

pub struct RtcpPacket<'a> {
    pub parts: Vec<RtcpPart<'a>>,
}

pub enum RtcpPart<'a> {
    SenderReport(SenderReport<'a>),
    ReceiverReport(ReceiverReport),
    SourceDescription(SourceDescription),
    Bye(Bye<'a>),
    Application(Application<'a>),
}

pub struct SenderReport<'a> {
    pub ssrc: SSRC,
    pub sender_info: SenderInfo,
    pub reports: Vec<ReportBlock>,
    pub extension: &'a [u8],
}
pub struct ReceiverReport {
    pub sender_ssrc: SSRC,
    pub reports: Vec<ReportBlock>,
}
pub struct SourceDescription {
    sources: Vec<(SSRC, Vec<SourceDescriptionItem>)>,
}
pub enum SourceDescriptionItem {
    CanonicalName(String),
    Name(String),
    Email(String),
    Phone(String),
    Location(String),
    Tool(String),
    Notice(String),
    PrivateExtension(String),
}
pub struct Bye<'a> {
    pub ssrcs: Vec<SSRC>,
    pub reason: &'a [u8],
}
pub struct Application<'a> {
    pub subtype: u8,
    pub name: [u8; 4],
    pub data: &'a [u8],
}
pub struct SenderInfo {
    pub ntp_ts: u64,
    pub rtp_ts: u32,
    pub packet_count: u32,
    pub octet_count: u32,
}
pub struct ReportBlock {
    pub ssrc: SSRC,
    pub fraction_lost: u8,
    pub cumulative_packets_lost: u32,
    pub ext_max_seq_num_recv: u32,
    pub interarrical_jitter: u32,
    pub lsr: u32,
    pub dlsr: u32,
}

impl<'a> RtcpPacket<'a> {
    pub fn parse(mut packet: &'a [u8]) -> Result<RtcpPacket<'a>, Error> {
        let mut parts = Vec::with_capacity(2);
        while packet.len() > 0 {
            if packet.len() < 4 {
                return Err(Error::Truncated);
            }
            let version = (packet[0] & 0b11000000) >> 6;
            if !matches!(version, 1 | 2) {
                return Err(Error::Version);
            }
            let padding = (packet[0] & 0b00100000) != 0;
            let num_reports = (packet[0] & 0b00011111) >> 0;
            let packet_type = packet[1];
            let length = u16::from_be_bytes([packet[2], packet[3]]);

            match packet_type {
                200 => {
                    // sender seport
                    if packet.len() < 28 + 24 * num_reports as usize {
                        return Err(Error::Truncated);
                    }
                    let ssrc = SSRC(u32::from_be_bytes(packet[4..8].try_into().unwrap()));
                    let sender_info = SenderInfo::parse(packet[8..28].try_into().unwrap());
                    let mut reports = Vec::with_capacity(num_reports as usize);
                    for n in 0..num_reports as usize {
                        reports.push(ReportBlock::parse(
                            packet[28 + 24 * n..28 + 24 * (n + 1)].try_into().unwrap(),
                        ));
                    }
                    let extension = &packet[28 + 24 * num_reports as usize..];
                    parts.push(RtcpPart::SenderReport(SenderReport {
                        reports,
                        sender_info,
                        ssrc,
                        extension,
                    }))
                }
                201 => {
                    // receiver report
                }
                202 => {
                    // source description
                }
                203 => {
                    // bye
                }
                204 => {
                    // application defined
                }
                _ => {}
            }
            packet = &packet[length as usize..];
        }
        Ok(Self { parts })
    }
    pub fn write(&self, out: &mut Vec<u8>) {
        for part in &self.parts {
            let version = 2;
            let padding = false;
            match part {
                RtcpPart::SenderReport(sender_report) => {
                    out.push(
                        version << 6 | (padding as u8) << 5 | sender_report.reports.len() as u8,
                    );
                    out.push(200);
                }
                RtcpPart::ReceiverReport(receiver_report) => todo!(),
                RtcpPart::SourceDescription(source_description) => todo!(),
                RtcpPart::Bye(bye) => todo!(),
                RtcpPart::Application(application) => todo!(),
            }
        }
    }
}
impl SenderInfo {
    pub const SIZE: usize = 5 * 4;
    pub fn parse(packet: [u8; 5 * 4]) -> SenderInfo {
        Self {
            ntp_ts: u64::from_be_bytes(packet[0..8].try_into().unwrap()),
            rtp_ts: u32::from_be_bytes(packet[8..12].try_into().unwrap()),
            packet_count: u32::from_be_bytes(packet[12..16].try_into().unwrap()),
            octet_count: u32::from_be_bytes(packet[16..20].try_into().unwrap()),
        }
    }
    pub fn write(&self, out: &mut Vec<u8>) {
        out.extend(self.ntp_ts.to_be_bytes());
        out.extend(self.rtp_ts.to_be_bytes());
        out.extend(self.packet_count.to_be_bytes());
        out.extend(self.octet_count.to_be_bytes());
    }
}
impl ReportBlock {
    pub fn parse(packet: [u8; 6 * 4]) -> ReportBlock {
        Self {
            ssrc: SSRC(u32::from_be_bytes(packet[0..4].try_into().unwrap())),
            fraction_lost: packet[4],
            cumulative_packets_lost: u32::from_be_bytes([0, packet[5], packet[6], packet[7]]),
            ext_max_seq_num_recv: u32::from_be_bytes(packet[8..12].try_into().unwrap()),
            interarrical_jitter: u32::from_be_bytes(packet[12..16].try_into().unwrap()),
            lsr: u32::from_be_bytes(packet[16..20].try_into().unwrap()),
            dlsr: u32::from_be_bytes(packet[20..24].try_into().unwrap()),
        }
    }
    pub fn write(&self, out: &mut Vec<u8>) {
        out.extend(self.ssrc.0.to_be_bytes());
        out.push(self.fraction_lost);
        out.extend(&self.cumulative_packets_lost.to_be_bytes()[1..]);
        out.extend(self.ext_max_seq_num_recv.to_be_bytes());
        out.extend(self.interarrical_jitter.to_be_bytes());
        out.extend(self.lsr.to_be_bytes());
        out.extend(self.dlsr.to_be_bytes());
    }
}