//! # Message Parser
//! The message parser is the low level API which takes care of encoding and decoding of Payloads.
//! The normal user should not need to interact with this directly to communicate with Tuya
//! devices, but rather create an instance of the TuyaDevice struct.
use crate::cipher::TuyaCipher;
use crate::crc::crc;
use crate::error::ErrorKind;
use crate::{Payload, Result};
use hex::FromHex;
use log::{debug, error};
use nom::{
    bytes::complete::tag,
    combinator::{map, peek, recognize},
    multi::{length_data, many1},
    number::complete::be_u32,
    sequence::tuple,
    IResult,
};

use num_derive::{FromPrimitive, ToPrimitive};
use num_traits::{FromPrimitive, ToPrimitive};
use std::cmp::PartialEq;
use std::convert::TryInto;
use std::fmt;
use std::str::FromStr;

const UDP_KEY: &str = "yGAdlopoPVldABfn";

lazy_static! {
    static ref PREFIX_BYTES: [u8; 4] = <[u8; 4]>::from_hex("000055AA").unwrap();
    static ref SUFFIX_BYTES: [u8; 4] = <[u8; 4]>::from_hex("0000AA55").unwrap();
}

/// Human readable definitions of command bytes.
#[derive(Debug, FromPrimitive, ToPrimitive, Clone, PartialEq)]
pub enum CommandType {
    Udp = 0,
    ApConfig = 1,
    Active = 2,
    Bind = 3,
    RenameGw = 4,
    RenameDevice = 5,
    Unbind = 6,
    Control = 7,
    Status = 8,
    HeartBeat = 9,
    DpQuery = 10,
    QueryWifi = 11,
    TokenBind = 12,
    ControlNew = 13,
    EnableWifi = 14,
    DpQueryNew = 16,
    SceneExecute = 17,
    DpRefresh = 18,
    UdpNew = 19,
    ApConfigNew = 20,
    LanGwActive = 240,
    LanSubDevRequest = 241,
    LanDeleteSubDev = 242,
    LanReportSubDev = 243,
    LanScene = 244,
    LanPublishCloudConfig = 245,
    LanPublishAppConfig = 246,
    LanExportAppConfig = 247,
    LanPublishScenePanel = 248,
    LanRemoveGw = 249,
    LanCheckGwUpdate = 250,
    LanGwUpdate = 251,
    LanSetGwChannel = 252,
    Error = 255,
}

#[derive(Debug, PartialEq, Clone)]
pub(crate) enum TuyaVersion {
    ThreeOne,
    ThreeThree,
}

impl TuyaVersion {
    pub fn as_bytes(&self) -> &[u8] {
        match &self {
            TuyaVersion::ThreeOne => b"3.1",
            TuyaVersion::ThreeThree => b"3.3",
        }
    }
}

impl FromStr for TuyaVersion {
    type Err = ErrorKind;

    fn from_str(s: &str) -> Result<Self> {
        let version: Vec<&str> = s.split('.').collect();
        if version.len() > 1 && version[0].ends_with('3') {
            if version[1] == "1" {
                return Ok(TuyaVersion::ThreeOne);
            } else if version[1] == "3" {
                return Ok(TuyaVersion::ThreeThree);
            }
            return Err(ErrorKind::VersionError(
                version[0].to_string(),
                version[1].to_string(),
            ));
        }
        Err(ErrorKind::VersionError(
            "Unknown".to_string(),
            "Unknown".to_string(),
        ))
    }
}

/// Representation of a message sent to and received from a Tuya device. The Payload is
/// serialized to and deserialized from JSON. The sequence number, if sent in a command, will
/// be included in the response to be able to connect command and response. The return code is
/// only included if the Message is a response from a device.
#[derive(Debug, PartialEq)]
pub struct Message {
    pub payload: Payload,
    pub command: Option<CommandType>,
    pub seq_nr: Option<u32>,
    pub ret_code: Option<u8>,
}

impl fmt::Display for Message {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(
            f,
            "Payload: \"{}\", Command: {:?}, Seq Nr: {:?}, Return Code: {:?}",
            self.payload,
            self.command.clone().unwrap_or(CommandType::Error),
            self.seq_nr,
            self.ret_code,
        )
    }
}

impl Message {
    pub fn new(payload: Payload, command: CommandType, seq_nr: Option<u32>) -> Message {
        Message {
            payload,
            command: Some(command),
            seq_nr,
            ret_code: None,
        }
    }
}

/// The message parser takes care of encoding and parsing messages before send and after
/// receive. It uses a TuyaCipher to encrypt and decrypt messages sent with the Tuya
/// protocol version 3.3.
pub struct MessageParser {
    version: TuyaVersion,
    cipher: TuyaCipher,
}

/// MessageParser encodes and parses messages sent to and from Tuya devices. It may or may not
/// encrypt the message, depending on message type and TuyaVersion. Likewise, the parsing may or may
/// not need decrypting.
impl MessageParser {
    pub fn create(ver: &str, key: Option<&str>) -> Result<MessageParser> {
        let version = TuyaVersion::from_str(ver)?;
        let key = verify_key(key)?;
        let cipher = TuyaCipher::create(&key, version.clone());
        Ok(MessageParser { version, cipher })
    }

    pub fn encode(&self, mes: &Message, encrypt: bool) -> Result<Vec<u8>> {
        let mut encoded: Vec<u8> = vec![];
        encoded.extend_from_slice(&*PREFIX_BYTES);
        match mes.seq_nr {
            Some(nr) => encoded.extend(&nr.to_be_bytes()),
            None => encoded.extend(&0_u32.to_be_bytes()),
        }
        let command = mes.command.clone().ok_or(ErrorKind::CommandTypeMissing)?;
        encoded.extend([0, 0, 0, command.to_u8().unwrap()].iter());
        let payload = self.create_payload_header(mes, encrypt)?;
        let ret_len = match mes.ret_code {
            Some(_) => 4_u32,
            None => 0_u32,
        };
        encoded.extend(
            (payload.len() as u32 + 8_u32 + ret_len)
                .to_be_bytes()
                .iter(),
        );
        if let Some(ret_code) = mes.ret_code {
            encoded.extend(&ret_code.to_be_bytes());
        }
        encoded.extend(payload);
        encoded.extend(crc(&encoded).to_be_bytes().iter());
        encoded.extend_from_slice(&*SUFFIX_BYTES);
        debug!(
            "Encoded message ({}):\n{}",
            mes.seq_nr.unwrap_or(0),
            hex::encode(&encoded)
        );

        Ok(encoded)
    }

    fn create_payload_header(&self, mes: &Message, encrypt: bool) -> Result<Vec<u8>> {
        match self.version {
            TuyaVersion::ThreeOne => {
                if encrypt {
                    self.create_payload_with_header(mes.payload.clone().try_into()?)
                } else {
                    mes.payload.clone().try_into()
                }
            }
            TuyaVersion::ThreeThree => match mes.command {
                Some(CommandType::DpQuery) | Some(CommandType::DpRefresh) => {
                    let payload: Vec<u8> = mes.payload.clone().try_into()?;
                    self.cipher.encrypt(&payload)
                }
                _ => self.create_payload_with_header(mes.payload.clone().try_into()?),
            },
        }
    }

    fn create_payload_with_header(&self, payload: Vec<u8>) -> Result<Vec<u8>> {
        let mut payload_with_header = Vec::new();
        payload_with_header.extend(self.version.as_bytes());
        match self.version {
            TuyaVersion::ThreeOne => payload_with_header.extend(vec![0; 12]),
            TuyaVersion::ThreeThree => payload_with_header.extend(self.cipher.md5(&payload)),
        }
        payload_with_header.extend(self.cipher.encrypt(&payload)?);
        Ok(payload_with_header)
    }

    pub fn parse(&self, buf: &[u8]) -> Result<Vec<Message>> {
        let (buf, messages) = self.parse_messages(buf).map_err(|err| match err {
            nom::Err::Error(e) => ErrorKind::ParseError(e.code),
            nom::Err::Incomplete(_) => ErrorKind::ParsingIncomplete,
            nom::Err::Failure(e) if e.code == nom::error::ErrorKind::ManyMN => ErrorKind::CRCError,
            nom::Err::Failure(e) => ErrorKind::ParseError(e.code),
        })?;
        if !buf.is_empty() {
            return Err(ErrorKind::BufferNotCompletelyParsedError);
        }
        Ok(messages)
    }

    fn parse_messages<'a>(&self, orig_buf: &'a [u8]) -> IResult<&'a [u8], Vec<Message>> {
        // TODO: can this be statically initialized??
        let be_u32_minus4 = map(be_u32, |n: u32| n - 4);
        let (buf, vec) = many1(tuple((
            tag(*PREFIX_BYTES),
            be_u32,
            be_u32,
            length_data(be_u32_minus4),
            tag(*SUFFIX_BYTES),
        )))(orig_buf)?;
        let mut messages = vec![];
        for (_, seq_nr, command, recv_data, _) in vec {
            // check if the recv_data contains a return code
            let (recv_data, maybe_retcode) = peek(be_u32)(recv_data)?;
            let (recv_data, ret_code, ret_len) = if maybe_retcode & 0xFFFF_FF00 == 0 {
                // Has a return code
                let (recv_data, ret_code) = recognize(be_u32)(recv_data)?;
                (recv_data, Some(ret_code[3]), 4_usize)
            } else {
                // Has no return code
                (recv_data, None, 0_usize)
            };
            let (payload, rc) = recv_data.split_at(recv_data.len() - 4);
            let recv_crc = u32::from_be_bytes([rc[0], rc[1], rc[2], rc[3]]);
            if crc(&orig_buf[0..recv_data.len() + 12 + ret_len]) != recv_crc {
                error!(
                    "Found CRC: {:#x}, Expected CRC: {:#x}",
                    recv_crc,
                    crc(&orig_buf[0..recv_data.len() + 12 + ret_len])
                );
                // I hijack the ErrorKind::ManyMN here to propagate a CRC error
                // TODO: should probably create and use a special CRC error here
                return Err(nom::Err::Failure(nom::error::Error::new(
                    rc,
                    nom::error::ErrorKind::ManyMN,
                )));
            }

            let payload = self.try_decrypt(payload);
            let message = Message {
                payload,
                command: FromPrimitive::from_u32(command).or(None),
                seq_nr: Some(seq_nr),
                ret_code,
            };
            messages.push(message);
        }
        Ok((buf, messages))
    }

    fn try_decrypt(&self, payload: &[u8]) -> Payload {
        match self.cipher.decrypt(payload) {
            Ok(decrypted) => {
                if let Ok(p) = serde_json::from_slice(&decrypted) {
                    Payload::Struct(p)
                } else {
                    Payload::String(
                        std::str::from_utf8(&decrypted)
                            .unwrap_or("Payload invalid")
                            .to_string(),
                    )
                }
            }
            Err(_) => {
                if let Ok(p) = serde_json::from_slice(payload) {
                    Payload::Struct(p)
                } else {
                    Payload::String(
                        std::str::from_utf8(payload)
                            .unwrap_or("Payload invalid")
                            .to_string(),
                    )
                }
            }
        }
    }
}

fn verify_key(key: Option<&str>) -> Result<Vec<u8>> {
    match key {
        Some(key) => {
            if key.len() == 16 {
                Ok(key.as_bytes().to_vec())
            } else {
                Err(ErrorKind::KeyLength(key.len()))
            }
        }
        None => {
            let default_key = md5::compute(UDP_KEY).0;
            Ok(default_key.to_vec())
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::PayloadStruct;
    use serde_json::json;
    use std::collections::HashMap;
    #[test]
    fn test_key_length_is_16() {
        let key = Some("0123456789ABCDEF");
        assert!(verify_key(key).is_ok());
    }

    #[test]
    fn test_key_length_not_16_gives_error() {
        let bad_key = Some("13579BDF");
        assert!(verify_key(bad_key).is_err());
    }

    #[test]
    fn test_parse_mqttversion() {
        let version = TuyaVersion::from_str("3.1").unwrap();
        assert_eq!(version, TuyaVersion::ThreeOne);

        let version2 = TuyaVersion::from_str("ver3.3").unwrap();
        assert_eq!(version2, TuyaVersion::ThreeThree);

        assert!(TuyaVersion::from_str("3.4").is_err());
    }

    #[test]
    fn test_parse_messages() {
        let packet =
            hex::decode("000055aa00000000000000090000000c00000000b051ab030000aa55").unwrap();
        let expected = Message {
            command: Some(CommandType::HeartBeat),
            payload: Payload::String("".to_string()),
            seq_nr: Some(0),
            ret_code: Some(0),
        };
        let mp = MessageParser::create("3.1", None).unwrap();
        let (buf, messages) = mp.parse_messages(&packet).unwrap();
        assert_eq!(messages[0], expected);
        assert_eq!(buf, &[] as &[u8]);
    }

    #[test]
    fn test_parse_messages_with_payload() {
        let packet = hex::decode("000055aa00000000000000070000005b00000000332e33d8bab8946c604148a45c15326ed3b99d683695a73c624e75a5aaa31f4061f5b99033e6d01f0b0abf9dbc76b2a54eb4bf60976b1dc496169db9e5a3fd627f2c3d9c4744585e471b6a2fc479ca01f7e18e0000aa55").unwrap();
        let mut dps = HashMap::new();
        dps.insert("1".to_string(), json!(true));
        let expected = Message {
            command: Some(CommandType::Control),
            payload: Payload::Struct(PayloadStruct {
                dev_id: "46052834d8f15b92e53b".to_string(),
                gw_id: None,
                uid: None,
                t: None,
                dp_id: None,
                dps: Some(dps),
            }),
            seq_nr: Some(0),
            ret_code: Some(0),
        };
        let mp = MessageParser::create("3.3", None).unwrap();
        let (buf, messages) = mp.parse_messages(&packet).unwrap();
        assert_eq!(messages[0], expected);
        assert_eq!(buf, &[] as &[u8]);
    }

    #[test]
    fn test_parse_data_format_error() {
        let packet =
            hex::decode("000055aa00000000000000070000003b00000001332e33d504910232d355a59ed1f6ed1f4a816a1e8e30ed09987c020ae45d72c70592bb233c79c43a5b9ae49b6ead38725deb520000aa55").unwrap();
        let expected = Message {
            command: Some(CommandType::Control),
            payload: Payload::String("data format error".to_string()),
            seq_nr: Some(0),
            ret_code: Some(1),
        };
        let mp = MessageParser::create("3.3", None).unwrap();
        let (buf, messages) = mp.parse_messages(&packet).unwrap();
        assert_eq!(messages[0], expected);
        assert_eq!(buf, &[] as &[u8]);
    }

    #[test]
    fn test_parse_double_messages() {
        let packet =
            hex::decode("000055aa00000000000000090000000c00000000b051ab030000aa55000055aa000000000000000a0000000c00000000b051ab030000aa55").unwrap();
        let expected = vec![
            Message {
                command: Some(CommandType::HeartBeat),
                payload: Payload::String("".to_string()),
                seq_nr: Some(0),
                ret_code: Some(0),
            },
            Message {
                command: Some(CommandType::DpQuery),
                payload: Payload::String("".to_string()),
                seq_nr: Some(0),
                ret_code: Some(0),
            },
        ];
        let mp = MessageParser::create("3.1", None).unwrap();
        let (buf, messages) = mp.parse_messages(&packet).unwrap();
        assert_eq!(messages[0], expected[0]);
        assert_eq!(messages[1], expected[1]);
        assert_eq!(buf, &[] as &[u8]);
    }

    #[test]
    fn test_encode_with_and_without_encryption_and_version_three_one() {
        let mut dps = HashMap::new();
        dps.insert("1".to_string(), json!(true));
        dps.insert("2".to_string(), json!(0));
        let payload = Payload::Struct(PayloadStruct {
            dev_id: "002004265ccf7fb1b659".to_string(),
            gw_id: None,
            uid: None,
            t: None,
            dp_id: None,
            dps: Some(dps),
        });
        let mes = Message {
            command: Some(CommandType::DpQuery),
            payload,
            seq_nr: Some(0),
            ret_code: Some(0),
        };
        let parser = MessageParser::create("3.1", None).unwrap();
        let encrypted = parser.encode(&mes, true).unwrap();
        let unencrypted = parser.encode(&mes, false).unwrap();
        // Only encrypt 3.1 if the flag is set
        assert_ne!(encrypted, unencrypted);
    }

    #[test]
    fn test_encode_with_and_without_encryption_and_version_three_three() {
        let mut dps = HashMap::new();
        dps.insert("1".to_string(), json!(true));
        let payload = Payload::Struct(PayloadStruct {
            dev_id: "002004265ccf7fb1b659".to_string(),
            gw_id: None,
            uid: None,
            t: None,
            dp_id: None,
            dps: Some(dps),
        });
        let mes = Message {
            command: Some(CommandType::DpQuery),
            payload,
            seq_nr: Some(0),
            ret_code: Some(0),
        };
        let parser = MessageParser::create("3.3", None).unwrap();

        let encrypted = parser.encode(&mes, true).unwrap();
        let unencrypted = parser.encode(&mes, false).unwrap();
        // Always encrypt 3.3, no matter what the flag is
        assert_eq!(encrypted, unencrypted);
    }
}