use crate::{Protocol300Message, message};
use thiserror::Error;

#[cfg(feature = "defmt")]
use defmt::{error};

#[cfg(feature = "log")]
use log::{error};

extern crate alloc;

use alloc::vec;
use alloc::vec::Vec;
use alloc::borrow::ToOwned;

#[derive(Debug, PartialEq, Eq)]
pub enum Protocol300Transmission {
    /// 0x06 - ACK, used by all clients as acknowledgement
    Ack,
    /// 0x05 - Gets sent periodically to indicate idle/not initialized connection by the heater
    Enq,
    /// 0x04 - Resets the connection to a known state
    Eot,
    /// 0x16 0x00 0x00 - Initializes the connection, sent by the client
    Init,
    /// 0x15 - Negative Acknowledgement, indicates an error in the last message
    Nack,
    /// A valid decoded message
    Message(Protocol300Message)
}

impl Protocol300Transmission {
    /// Try to convert bytes to a Protocol 300 Transmission
    /// 
    /// # Errors
    /// Returns a `FromBytesError` if the conversion fails in some way
    pub fn try_from_bytes(bytes: &[u8]) -> Result<Self, FromBytesError> {
        match bytes {
            [0x06] => Ok(Self::Ack),
            [0x05] => Ok(Self::Enq),
            [0x04] => Ok(Self::Eot),
            [0x15] => Ok(Self::Nack),
            [0x16, 0x00, 0x00] => Ok(Self::Init),
            [0x41, ..] => Ok(Self::Message(Protocol300Message::try_from_bytes(bytes)?)),
            b => {
                error!("Failed to parse Protocol300 transmission: invalid byte sequence (length: {}, first byte: 0x{:02X})", 
                       bytes.len(), 
                       bytes.first().unwrap_or(&0x00));
                Err(FromBytesError::InvalidBytes(b.to_owned()))
            },
        }
    }

    #[must_use]
    pub fn to_bytes(&self) -> Vec<u8> {
        match self {
            Self::Ack => vec![0x06],
            Self::Enq => vec![0x05],
            Self::Eot => vec![0x04],
            Self::Init => vec![0x16, 0x00, 0x00],
            Self::Nack => vec![0x15],
            Self::Message(protocol300_message) => protocol300_message.to_bytes(),
        }
    }

    /// Returns the length in bytes of the transmission
    #[must_use]
    pub fn length_in_bytes(&self) -> usize {
        match self {
            Self::Ack | Self::Enq | Self::Eot | Self::Nack => 1,
            Self::Init => 3,
            Self::Message(protocol300_message) => (protocol300_message.telegram_length + 3).into(),
        }
    }
}

/// Errors that can occur when getting a Protocol 300 Transmission from bytes
#[derive(Error, Debug, PartialEq, Eq)]
pub enum FromBytesError{
    #[error("Failed to parse message")]
    MessageParsing(#[from] message::MessageDecodingError),
    #[error("Invalid bytes in vec")]
    InvalidBytes(Vec<u8>)

}

#[cfg(test)]
mod tests {
    use crate::{FunctionCode, MessageIdentifier, Protocol300Message, transmission::Protocol300Transmission};

    #[test]
    fn from_bytes_ack() {
        assert_eq!(Protocol300Transmission::Ack, Protocol300Transmission::try_from_bytes(&[0x06]).unwrap());
    }

    #[test]
    fn from_bytes_nack() {
        assert_eq!(Protocol300Transmission::Nack, Protocol300Transmission::try_from_bytes(&[0x15]).unwrap());
    }

    #[test]
    fn from_bytes_eot() {
        assert_eq!(Protocol300Transmission::Eot, Protocol300Transmission::try_from_bytes(&[0x04]).unwrap());
    }

    #[test]
    fn from_bytes_enq() {
        assert_eq!(Protocol300Transmission::Enq, Protocol300Transmission::try_from_bytes(&[0x05]).unwrap());
    }

    #[test]
    fn from_bytes_init() {
        assert_eq!(Protocol300Transmission::Init, Protocol300Transmission::try_from_bytes(&[0x16, 0x00, 0x00]).unwrap());
    }

    #[test]
    fn from_bytes_message() {
        let message = Protocol300Message{
            data_address: 0x5525,
            telegram_length: 0x09,
            function_code: FunctionCode::VirtualREAD,
            message_identifier: MessageIdentifier::Response,
            data_length: 0x04,
            data: vec![0x07, 0x01, 0x27, 0x11],
            checksum: 0xC9
        };
        let bytes = vec![0x41, 0x09, 0x01, 0x01, 0x55, 0x25, 0x04, 0x07, 0x01, 0x27, 0x11, 0xC9];
        assert_eq!(Protocol300Transmission::Message(message), Protocol300Transmission::try_from_bytes(&bytes).unwrap());
    }

    #[test]
    fn to_bytes_ack() {
        assert_eq!(Protocol300Transmission::Ack.to_bytes(), &[0x06]);
    }

    #[test]
    fn to_bytes_eot() {
        assert_eq!(Protocol300Transmission::Eot.to_bytes(), &[0x04]);
    }

    #[test]
    fn to_bytes_nack() {
        assert_eq!(Protocol300Transmission::Nack.to_bytes(), &[0x15]);
    }

    #[test]
    fn to_bytes_enq() {
        assert_eq!(Protocol300Transmission::Enq.to_bytes(), &[0x05]);
    }

    #[test]
    fn to_bytes_init() {
        assert_eq!(Protocol300Transmission::Init.to_bytes(), &[0x16, 0x00, 0x00]);
    }

    #[test]
    fn to_bytes_message() {
        let message = Protocol300Message{
            data_address: 0x5525,
            telegram_length: 0x09,
            function_code: FunctionCode::VirtualREAD,
            message_identifier: MessageIdentifier::Response,
            data_length: 0x04,
            data: vec![0x07, 0x01, 0x27, 0x11],
            checksum: 0xC9
        };
        assert_eq!(Protocol300Transmission::Message(message).to_bytes(), &[0x41, 0x09, 0x01, 0x01, 0x55, 0x25, 0x04, 0x07, 0x01, 0x27, 0x11, 0xC9]);
    }

    #[test]
    fn length_in_bytes_ack() {
        assert_eq!(Protocol300Transmission::Ack.length_in_bytes(), 1);
    }

    #[test]
    fn length_in_bytes_enq() {
        assert_eq!(Protocol300Transmission::Enq.length_in_bytes(), 1);
    }

    #[test]
    fn length_in_bytes_eot() {
        assert_eq!(Protocol300Transmission::Eot.length_in_bytes(), 1);
    }

    #[test]
    fn length_in_bytes_nack() {
        assert_eq!(Protocol300Transmission::Nack.length_in_bytes(), 1);
    }

    #[test]
    fn length_in_bytes_init() {
        assert_eq!(Protocol300Transmission::Init.length_in_bytes(), 3);
    }

    #[test]
    fn length_in_bytes_message() {
        let message = Protocol300Message{
            data_address: 0x5525,
            telegram_length: 0x09,
            function_code: FunctionCode::VirtualREAD,
            message_identifier: MessageIdentifier::Response,
            data_length: 0x04,
            data: vec![0x07, 0x01, 0x27, 0x11],
            checksum: 0xC9
        };
        // telegram_length is 0x09, so expected length is 0x09 + 3 = 12
        assert_eq!(Protocol300Transmission::Message(message).length_in_bytes(), 12);
    }
}