//! Diag protocol serialization/deserialization

use chrono::{DateTime, FixedOffset};
use crc::{Algorithm, Crc};
use deku::prelude::*;

use crate::hdlc::{self, hdlc_decapsulate};
use log::{warn, error};
use thiserror::Error;

pub const MESSAGE_TERMINATOR: u8 = 0x7e;
pub const MESSAGE_ESCAPE_CHAR: u8 = 0x7d;

pub const ESCAPED_MESSAGE_TERMINATOR: u8 = 0x5e;
pub const ESCAPED_MESSAGE_ESCAPE_CHAR: u8 = 0x5d;

#[derive(Debug, Clone, DekuWrite)]
pub struct RequestContainer {
    pub data_type: DataType,
    #[deku(skip)]
    pub use_mdm: bool,
    #[deku(skip, cond = "!*use_mdm")]
    pub mdm_field: i32,
    pub hdlc_encapsulated_request: Vec<u8>,
}

#[derive(Debug, Clone, PartialEq, DekuWrite)]
#[deku(type = "u32")]
pub enum Request {
    #[deku(id = "115")]
    LogConfig(LogConfigRequest),
}

#[derive(Debug, Clone, PartialEq, DekuWrite)]
#[deku(type = "u32", endian = "little")]
pub enum LogConfigRequest {
    #[deku(id = "1")]
    RetrieveIdRanges,

    #[deku(id = "3")]
    SetMask {
        log_type: u32,
        log_mask_bitsize: u32,
        log_mask: Vec<u8>,
    }
}

#[derive(Debug, Clone, PartialEq, DekuRead, DekuWrite)]
#[deku(type = "u32", endian = "little")]
pub enum DataType {
    #[deku(id = "32")]
    UserSpace,
    #[deku(id_pat = "_")]
    Other(u32),
}

#[derive(Debug, Clone, PartialEq, Error)]
pub enum DiagParsingError {
    #[error("Failed to parse Message: {0}, data: {1:?}")]
    MessageParsingError(deku::DekuError, Vec<u8>),
    #[error("HDLC decapsulation of message failed: {0}, data: {1:?}")]
    HdlcDecapsulationError(hdlc::HdlcError, Vec<u8>),
}

// this is sorta based on the params qcsuper uses, plus what seems to be used in
// https://github.com/fgsect/scat/blob/f1538b397721df3ab8ba12acd26716abcf21f78b/util.py#L47
pub const CRC_CCITT_ALG: Algorithm<u16> = Algorithm {
    poly: 0x1021,
    init: 0xffff,
    refin: true,
    refout: true,
    width: 16,
    xorout: 0xffff,
    check: 0x2189,
    residue: 0x0000,
};

pub const CRC_CCITT: Crc<u16> = Crc::<u16>::new(&CRC_CCITT_ALG);
#[derive(Debug, Clone, PartialEq, DekuRead, DekuWrite)]
pub struct MessagesContainer {
    pub data_type: DataType,
    pub num_messages: u32,
    #[deku(count = "num_messages")]
    pub messages: Vec<HdlcEncapsulatedMessage>,
}

impl MessagesContainer {
    pub fn into_messages(self) -> Vec<Result<Message, DiagParsingError>> {
        let mut result = Vec::new();
        for msg in self.messages {
            for sub_msg in msg.data.split_inclusive(|&b| b == MESSAGE_TERMINATOR) {
                match hdlc_decapsulate(sub_msg, &CRC_CCITT) {
                    Ok(data) => match Message::from_bytes((&data, 0)) {
                        Ok(((leftover_bytes, _), res)) => {
                            if !leftover_bytes.is_empty() {
                                warn!("warning: {} leftover bytes when parsing Message", leftover_bytes.len());
                            }
                            result.push(Ok(res));
                        },
                        Err(e) => result.push(Err(DiagParsingError::MessageParsingError(e, data))),
                    },
                    Err(err) => result.push(Err(DiagParsingError::HdlcDecapsulationError(err, sub_msg.to_vec()))),
                }
            }
        }
        result
    }
}

#[derive(Debug, Clone, PartialEq, DekuRead, DekuWrite)]
pub struct HdlcEncapsulatedMessage {
    pub len: u32,
    #[deku(count = "len")]
    pub data: Vec<u8>,
}

#[derive(Debug, Clone, PartialEq, DekuRead, DekuWrite)]
#[deku(type = "u8")]
pub enum Message {
    #[deku(id = "16")]
    Log {
        pending_msgs: u8,
        outer_length: u16,
        inner_length: u16,
        log_type: u16,
        timestamp: Timestamp,
        // pass the log type and log length (inner_length - (sizeof(log_type) + sizeof(timestamp)))
        #[deku(ctx = "*log_type, *inner_length - 12")]
        body: LogBody,
    },

    // kinda unpleasant deku hackery here. deku expects an enum's variant to be
    // right before its data, but in this case, a status value comes between the
    // variants and the data. so we need to use deku's context (ctx) feature to
    // pass those opcodes down to their respective parsers.
    #[deku(id_pat = "_")]
    Response {
        opcode: u32,
        subopcode: u32,
        status: u32,
        #[deku(ctx = "*opcode, *subopcode")]
        payload: ResponsePayload,
    },
}

#[derive(Debug, Clone, PartialEq, DekuRead, DekuWrite)]
#[deku(ctx = "log_type: u16, hdr_len: u16", id = "log_type")]
pub enum LogBody {
    #[deku(id = "0x412f")]
    WcdmaSignallingMessage {
        channel_type: u8,
        radio_bearer: u8,
        length: u16,
        #[deku(count = "length")]
        msg: Vec<u8>,
    },
    #[deku(id = "0x512f")]
    GsmRrSignallingMessage {
        channel_type: u8,
        message_type: u8,
        length: u8,
        #[deku(count = "length")]
        msg: Vec<u8>,
    },
    #[deku(id = "0x5226")]
    GprsMacSignallingMessage {
        channel_type: u8,
        message_type: u8,
        length: u8,
        #[deku(count = "length")]
        msg: Vec<u8>,
    },
    #[deku(id = "0xb0c0")]
    LteRrcOtaMessage{
        ext_header_version: u8,
        #[deku(ctx = "*ext_header_version")]
        packet: LteRrcOtaPacket,
    },
    // the four NAS command opcodes refer to:
    // * 0xb0e2: plain ESM NAS message (incoming)
    // * 0xb0e3: plain ESM NAS message (outgoing)
    // * 0xb0ec: plain EMM NAS message (incoming)
    // * 0xb0ed: plain EMM NAS message (outgoing)
    #[deku(id_pat = "0xb0e2 | 0xb0e3 | 0xb0ec | 0xb0ed")]
    Nas4GMessage {
        ext_header_version: u8,
        rrc_rel: u8,
        rrc_version_minor: u8,
        rrc_version_major: u8,
        // message length = hdr_len - (sizeof(ext_header_version) + sizeof(rrc_rel) + sizeof(rrc_version_minor) + sizeof(rrc_version_major))
        #[deku(count = "hdr_len - 4")]
        msg: Vec<u8>,
    },
    #[deku(id = "0x11eb")]
    IpTraffic {
        // is this right?? based on https://github.com/P1sec/QCSuper/blob/81dbaeee15ec7747e899daa8e3495e27cdcc1264/src/modules/pcap_dump.py#L378
        #[deku(count = "hdr_len - 8")]
        msg: Vec<u8>,
    },
    #[deku(id = "0x713a")]
    UmtsNasOtaMessage {
        is_uplink: u8,
        length: u32,
        #[deku(count = "length")]
        msg: Vec<u8>,
    },
    #[deku(id = "0xb821")]
    NrRrcOtaMessage {
        #[deku(count = "hdr_len")]
        msg: Vec<u8>,
    }
}

#[derive(Debug, Clone, PartialEq, DekuRead, DekuWrite)]
#[deku(ctx = "ext_header_version: u8", id = "ext_header_version")]
pub enum LteRrcOtaPacket {
    #[deku(id_pat = "0..=4")]
    V0 {
        rrc_rel_maj: u8,
        rrc_rel_min: u8,
        bearer_id: u8,
        phy_cell_id: u16,
        earfcn: u16,
        sfn_subfn: u16,
        pdu_num: u8,
        len: u16,
        #[deku(count = "len")]
        packet: Vec<u8>,
    },
    #[deku(id_pat = "5..=7")]
    V5 {
        rrc_rel_maj: u8,
        rrc_rel_min: u8,
        bearer_id: u8,
        phy_cell_id: u16,
        earfcn: u16,
        sfn_subfn: u16,
        pdu_num: u8,
        sib_mask: u32,
        len: u16,
        #[deku(count = "len")]
        packet: Vec<u8>,
    },
    #[deku(id_pat = "8..=24")]
    V8 {
        rrc_rel_maj: u8,
        rrc_rel_min: u8,
        bearer_id: u8,
        phy_cell_id: u16,
        earfcn: u32,
        sfn_subfn: u16,
        pdu_num: u8,
        sib_mask: u32,
        len: u16,
        #[deku(count = "len")]
        packet: Vec<u8>,
    },
    #[deku(id_pat = "25..")]
    V25 {
        rrc_rel_maj: u8,
        rrc_rel_min: u8,
        nr_rrc_rel_maj: u8,
        nr_rrc_rel_min: u8,
        bearer_id: u8,
        phy_cell_id: u16,
        earfcn: u32,
        sfn_subfn: u16,
        pdu_num: u8,
        sib_mask: u32,
        len: u16,
        #[deku(count = "len")]
        packet: Vec<u8>,
    },
}

impl LteRrcOtaPacket {
    fn get_sfn_subfn(&self) -> u16 {
        match self {
            LteRrcOtaPacket::V0 { sfn_subfn, .. } => *sfn_subfn,
            LteRrcOtaPacket::V5 { sfn_subfn, .. } => *sfn_subfn,
            LteRrcOtaPacket::V8 { sfn_subfn, .. } => *sfn_subfn,
            LteRrcOtaPacket::V25 { sfn_subfn, .. } => *sfn_subfn,
        }
    }
    pub fn get_sfn(&self) -> u32 {
        self.get_sfn_subfn() as u32 >> 4
    }

    pub fn get_subfn(&self) -> u8 {
        (self.get_sfn_subfn() & 0xf) as u8
    }

    pub fn get_pdu_num(&self) -> u8 {
        match self {
            LteRrcOtaPacket::V0 { pdu_num, .. } => *pdu_num,
            LteRrcOtaPacket::V5 { pdu_num, .. } => *pdu_num,
            LteRrcOtaPacket::V8 { pdu_num, .. } => *pdu_num,
            LteRrcOtaPacket::V25 { pdu_num, .. } => *pdu_num,
        }
    }

    pub fn get_earfcn(&self) -> u32 {
        match self {
            LteRrcOtaPacket::V0 { earfcn, .. } => *earfcn as u32,
            LteRrcOtaPacket::V5 { earfcn, .. } => *earfcn as u32,
            LteRrcOtaPacket::V8 { earfcn, .. } => *earfcn,
            LteRrcOtaPacket::V25 { earfcn, .. } => *earfcn,
        }
    }

    pub fn take_payload(self) -> Vec<u8> {
        match self {
            LteRrcOtaPacket::V0 { packet, .. } => packet,
            LteRrcOtaPacket::V5 { packet, .. } => packet,
            LteRrcOtaPacket::V8 { packet, .. } => packet,
            LteRrcOtaPacket::V25 { packet, .. } => packet,
        }
    }
}

#[derive(Debug, Clone, PartialEq, DekuRead, DekuWrite)]
#[deku(endian = "little")]
pub struct Timestamp {
    pub ts: u64,
}

impl Timestamp {
    pub fn to_datetime(&self) -> DateTime<FixedOffset> {
        // Upper 48 bits: epoch at 1980-01-06 00:00:00, incremented by 1 for 1/800s
        // Lower 16 bits: time since last 1/800s tick in 1/32 chip units
        let ts_upper = self.ts >> 16;
        let ts_lower = self.ts & 0xffff;
        let epoch = chrono::DateTime::parse_from_rfc3339("1980-01-06T00:00:00-00:00").unwrap();
        let mut delta_seconds = ts_upper as f64 * 1.25;
        delta_seconds += ts_lower as f64 / 40960.0;
        let ts_delta = chrono::Duration::milliseconds(delta_seconds as i64);
        epoch + ts_delta
    }
}

#[derive(Debug, Clone, PartialEq, DekuRead, DekuWrite)]
#[deku(ctx = "opcode: u32, subopcode: u32", id = "opcode")]
pub enum ResponsePayload {
    #[deku(id = "115")]
    LogConfig(#[deku(ctx = "subopcode")] LogConfigResponse),
}

#[derive(Debug, Clone, PartialEq, DekuRead, DekuWrite)]
#[deku(ctx = "subopcode: u32", id = "subopcode")]
pub enum LogConfigResponse {
    #[deku(id = "1")]
    RetrieveIdRanges {
        log_mask_sizes: [u32; 16],
    },

    #[deku(id = "3")]
    SetMask,
}

pub fn build_log_mask_request(log_type: u32, log_mask_bitsize: u32, accepted_log_codes: &[u32]) -> Request {
    let mut current_byte: u8 = 0;
    let mut num_bits_written: u8 = 0;
    let mut log_mask: Vec<u8> = vec![];
    for i in 0..log_mask_bitsize {
        let log_code: u32 = (log_type << 12) | i;
        if accepted_log_codes.contains(&log_code) {
            current_byte |= 1 << num_bits_written;
        }
        num_bits_written += 1;

        if num_bits_written == 8 || i == log_mask_bitsize - 1 {
            log_mask.push(current_byte);
            current_byte = 0;
            num_bits_written = 0;
        }
    }

    Request::LogConfig(LogConfigRequest::SetMask {
        log_type,
        log_mask_bitsize,
        log_mask,
    })
}

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

    // Just about all of these test cases from manually parsing diag packets w/ QCSuper

    #[test]
    fn test_request_serialization() {
        let req = Request::LogConfig(LogConfigRequest::RetrieveIdRanges);
        assert_eq!(req.to_bytes().unwrap(), vec![115, 0, 0, 0, 1, 0, 0, 0]);

        let req = Request::LogConfig(LogConfigRequest::SetMask {
            log_type: 0,
            log_mask_bitsize: 0,
            log_mask: vec![],
        });
        assert_eq!(req.to_bytes().unwrap(), vec![
            115, 0, 0, 0,
            3, 0, 0, 0,
            0, 0, 0, 0,
            0, 0, 0, 0,
        ]);
    }

    #[test]
    fn test_build_log_mask_request() {
        let log_type = 11;
        let bitsize = 513;
        let req = build_log_mask_request(log_type, bitsize, &crate::diag_device::LOG_CODES_FOR_RAW_PACKET_LOGGING);
        assert_eq!(req, Request::LogConfig(LogConfigRequest::SetMask {
            log_type: log_type,
            log_mask_bitsize: bitsize,
            log_mask: vec![
                0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
                0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x1, 0x0,
                0x0, 0x0, 0xc, 0x30, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
                0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
                0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
                0x0,
            ],
        }));
    }

    #[test]
    fn test_request_container() {
        let req = RequestContainer {
            data_type: DataType::UserSpace,
            use_mdm: false,
            mdm_field: -1,
            hdlc_encapsulated_request: vec![1, 2, 3, 4],
        };
        assert_eq!(req.to_bytes().unwrap(), vec![
            32, 0, 0, 0,
            1, 2, 3, 4,
        ]);
        let req = RequestContainer {
            data_type: DataType::UserSpace,
            use_mdm: true,
            mdm_field: -1,
            hdlc_encapsulated_request: vec![1, 2, 3, 4],
        };
        assert_eq!(req.to_bytes().unwrap(), vec![
            32, 0, 0, 0,
            255, 255, 255, 255,
            1, 2, 3, 4,
        ]);
    }

    #[test]
    fn test_logs() {
        let data = vec![
            16, 0, 38, 0, 38, 0, 192, 176, 26, 165, 245, 135, 118, 35, 2, 1, 20,
            14, 48, 0, 160, 0, 2, 8, 0, 0, 217, 15, 5, 0, 0, 0, 0, 7, 0, 64, 1,
            238, 173, 213, 77, 208
        ];
        let msg = Message::from_bytes((&data, 0)).unwrap().1;
        assert_eq!(msg, Message::Log {
            pending_msgs: 0,
            outer_length: 38,
            inner_length: 38,
            log_type: 0xb0c0,
            timestamp: Timestamp { ts: 72659535985485082 },
            body: LogBody::LteRrcOtaMessage {
                ext_header_version: 20,
                packet: LteRrcOtaPacket::V8 {
                    rrc_rel_maj: 14,
                    rrc_rel_min: 48,
                    bearer_id: 0,
                    phy_cell_id: 160,
                    earfcn: 2050,
                    sfn_subfn: 4057,
                    pdu_num: 5,
                    sib_mask: 0,
                    len: 7,
                    packet: vec![0x40, 0x1, 0xee, 0xad, 0xd5, 0x4d, 0xd0],
                },
            },
        });
    }

    fn make_container(data_type: DataType, message: HdlcEncapsulatedMessage) -> MessagesContainer {
        MessagesContainer {
            data_type,
            num_messages: 1,
            messages: vec![message],
        }
    }

    // this log is based on one captured on a real device -- if it fails to
    // serialize or deserialize, that's probably a problem with this mock, not
    // the DiagReader implementation
    fn get_test_message(payload: &[u8]) -> (HdlcEncapsulatedMessage, Message) {
        let length_with_payload = 31 + payload.len() as u16;
        let message = Message::Log {
            pending_msgs: 0,
            outer_length: length_with_payload,
            inner_length: length_with_payload,
            log_type: 0xb0c0,
            timestamp: Timestamp { ts: 72659535985485082 },
            body: LogBody::LteRrcOtaMessage {
                ext_header_version: 20,
                packet: LteRrcOtaPacket::V8 {
                    rrc_rel_maj: 14,
                    rrc_rel_min: 48,
                    bearer_id: 0,
                    phy_cell_id: 160,
                    earfcn: 2050,
                    sfn_subfn: 4057,
                    pdu_num: 5,
                    sib_mask: 0,
                    len: payload.len() as u16,
                    packet: payload.to_vec(),
                },
            },
        };
        let serialized = message.to_bytes().expect("failed to serialize test message");
        let encapsulated_data = hdlc::hdlc_encapsulate(&serialized, &CRC_CCITT);
        let encapsulated = HdlcEncapsulatedMessage {
            len: encapsulated_data.len() as u32,
            data: encapsulated_data,
        };
        (encapsulated, message)
    }

    #[test]
    fn test_containers_with_multiple_messages() {
        let (encapsulated1, message1) = get_test_message(&[1]);
        let (encapsulated2, message2) = get_test_message(&[2]);
        let mut container = make_container(DataType::UserSpace, encapsulated1);
        container.messages.push(encapsulated2);
        container.num_messages += 1;
        assert_eq!(container.into_messages(), vec![Ok(message1), Ok(message2)]);
    }

    #[test]
    fn test_containers_with_concatenated_message() {
        let (mut encapsulated1, message1) = get_test_message(&[1]);
        let (encapsulated2, message2) = get_test_message(&[2]);
        encapsulated1.data.extend(encapsulated2.data);
        encapsulated1.len += encapsulated2.len;
        let container = make_container(DataType::UserSpace, encapsulated1);
        assert_eq!(container.into_messages(), vec![Ok(message1), Ok(message2)]);
    }

    #[test]
    fn test_handles_parsing_errors() {
        let (encapsulated1, message1) = get_test_message(&[1]);
        let bad_message = hdlc::hdlc_encapsulate(&[0x01, 0x02, 0x03, 0x04], &CRC_CCITT);
        let encapsulated2 = HdlcEncapsulatedMessage {
            len: bad_message.len() as u32,
            data: bad_message,
        };
        let mut container = make_container(DataType::UserSpace, encapsulated1);
        container.messages.push(encapsulated2);
        container.num_messages += 1;
        let result = container.into_messages();
        assert_eq!(result[0], Ok(message1));
        assert!(matches!(result[1], Err(DiagParsingError::MessageParsingError(_, _))));
    }

    #[test]
    fn test_handles_encapsulation_errors() {
        let (encapsulated1, message1) = get_test_message(&[1]);
        let bad_encapsulation = HdlcEncapsulatedMessage {
            len: 4,
            data: vec![0x01, 0x02, 0x03, 0x04],
        };
        let mut container = make_container(DataType::UserSpace, encapsulated1);
        container.messages.push(bad_encapsulation);
        container.num_messages += 1;
        let result = container.into_messages();
        assert_eq!(result[0], Ok(message1));
        assert!(matches!(result[1], Err(DiagParsingError::HdlcDecapsulationError(_, _))));
    }
}