copt 0.1.0

use crate::{
    builder::ConnectBuilder, error::*,
    DtDataBuilder
};
use bytes::{Buf, BufMut, BytesMut};
use num_enum::{IntoPrimitive, TryFromPrimitive};
use std::fmt::Debug;

#[derive(Debug, Eq, PartialEq)]
pub struct CoptFrame<F: Debug + Eq + PartialEq> {
    pub pdu_type: PduType<F>
}

impl<F: Debug + Eq + PartialEq> CoptFrame<F> {
    pub fn builder_of_dt_data(
        payload: F
    ) -> DtDataBuilder<F> {
        DtDataBuilder::new(payload)
    }

    pub fn builder_of_connect()
    -> ConnectBuilder<F> {
        ConnectBuilder::<F>::default()
    }

    pub fn length(&self) -> u8 {
        self.pdu_type.length()
    }
}

#[derive(Debug, Eq, PartialEq)]
pub enum PduType<F: Debug + Eq + PartialEq> {
    /// 0x0e
    ConnectRequest(ConnectComm),
    /// 0x0d
    ConnectConfirm(ConnectComm),
    /// 0x0f
    DtData(DtData<F>)
}

impl<F: Debug + Eq + PartialEq> PduType<F> {
    pub fn length(&self) -> u8 {
        match self {
            PduType::ConnectRequest(conn) => {
                conn.length()
            },
            PduType::ConnectConfirm(conn) => {
                conn.length()
            },
            PduType::DtData(_) => 2
        }
    }
}
#[derive(Debug, Eq, PartialEq)]
pub struct DtData<F: Debug + Eq + PartialEq> {
    pub(crate) tpdu_number:    u8,
    pub(crate) last_data_unit: bool,
    pub(crate) payload:        F
}

impl<F: Debug + Eq + PartialEq> DtData<F> {
    pub fn tpdu_number(&self) -> u8 {
        self.tpdu_number
    }

    pub fn last_data_unit(&self) -> bool {
        self.last_data_unit
    }

    pub fn payload(self) -> F {
        self.payload
    }
}

#[derive(Debug, Eq, PartialEq)]
pub struct ConnectComm {
    pub destination_ref:          [u8; 2],
    pub source_ref:               [u8; 2],
    pub class:                    u8,
    pub extended_formats:         bool,
    pub no_explicit_flow_control: bool,
    pub parameters:               Vec<Parameter>
}

impl ConnectComm {
    pub fn length(&self) -> u8 {
        6 + self
            .parameters
            .iter()
            .fold(0, |x, item| x + item.length())
    }

    pub(crate) fn decode(
        src: &mut BytesMut
    ) -> Result<Self> {
        if src.len() < 5 {
            return Err(Error::Error(
                "data not enough".to_string()
            ));
        }
        let destination_ref =
            [src.get_u8(), src.get_u8()];
        let source_ref =
            [src.get_u8(), src.get_u8()];
        let merge = src.get_u8();
        let class = merge >> 4;
        let extended_formats =
            merge << 6 >> 7 > 0;
        let no_explicit_flow_control =
            merge & 1 > 0;

        let mut parameters = Vec::new();
        while let Some(parameter) =
            Parameter::decode(src)?
        {
            parameters.push(parameter);
        }
        Ok(Self {
            destination_ref,
            source_ref,
            class,
            extended_formats,
            no_explicit_flow_control,
            parameters
        })
    }

    pub(crate) fn encode(
        &self,
        dst: &mut BytesMut
    ) {
        dst.put_slice(
            self.destination_ref.as_ref()
        );
        dst.put_slice(self.source_ref.as_ref());

        let merge = self.class << 4
            & if self.extended_formats {
                2
            } else {
                0
            }
            & if self.no_explicit_flow_control {
                1
            } else {
                0
            };
        dst.put_u8(merge);
        self.parameters
            .iter()
            .for_each(|x| x.encode(dst));
    }
}

/// https://datatracker.ietf.org/doc/html/rfc905 13.3.4
#[derive(Debug, Eq, PartialEq)]
pub enum Parameter {
    /// 0xc0
    ///            0000 1101  8192 octets (not
    /// allowed in Class 0)
    //             0000 1100  4096 octets (not
    // allowed in Class 0)             0000
    // 1011  2048 octets             0000
    // 1010  1024 octets             0000
    // 1001   512 octets             0000
    // 1000   256 octets             0000
    // 0111   128 octets
    TpduSize(TpduSize),
    /// 0xc1    todo?
    SrcTsap(Vec<u8>),
    /// 0xc2    todo?
    DstTsap(Vec<u8>)
}

#[derive(
    Debug,
    Clone,
    Copy,
    Eq,
    PartialEq,
    TryFromPrimitive,
    IntoPrimitive,
)]
#[repr(u8)]
pub enum TpduSize {
    L8192 = 0b0000_1101,
    L4096 = 0b0000_1100,
    L2048 = 0b0000_1011,
    L1024 = 0b0000_1010,
    L512  = 0b0000_1001,
    L256  = 0b0000_1000,
    L128  = 0b0000_0111
}

impl TpduSize {
    pub fn pdu_ref(&self) -> u16 {
        match self {
            TpduSize::L8192 => 8192,
            TpduSize::L4096 => 4096,
            TpduSize::L2048 => 2048,
            TpduSize::L1024 => 1024,
            TpduSize::L512 => 512,
            TpduSize::L256 => 256,
            TpduSize::L128 => 128
        }
    }
}

impl Parameter {
    pub fn new_dst_tsap(data: Vec<u8>) -> Self {
        Self::DstTsap(data)
    }

    pub fn new_src_tsap(data: Vec<u8>) -> Self {
        Self::SrcTsap(data)
    }

    pub fn new_tpdu_size(size: TpduSize) -> Self {
        Self::TpduSize(size)
    }

    pub fn length(&self) -> u8 {
        match self {
            Parameter::TpduSize(_) => 3u8,
            Parameter::SrcTsap(data) => {
                2 + data.len() as u8
            },
            Parameter::DstTsap(data) => {
                2 + data.len() as u8
            },
        }
    }

    fn decode(
        dst: &mut BytesMut
    ) -> Result<Option<Self>> {
        if dst.len() == 0 {
            return Ok(None);
        }
        let (Some(ty), Some(length)) = (dst.get(0), dst.get(1)) else {
            return Err(Error::Error("data not enough".to_string()));
        };
        let length = (length + 2) as usize;
        let ty = *ty;
        if dst.len() < length {
            return Err(Error::Error(
                "data not enough".to_string()
            ));
        }
        let mut data =
            dst.split_to(length).split_off(2);
        match ty {
            0xc0 => {
                let size = data.get_u8();
                Ok(Some(Self::TpduSize(
                    size.try_into()?
                )))
            },
            0xc1 => Ok(Some(Self::SrcTsap(
                data.to_vec()
            ))),
            0xc2 => Ok(Some(Self::DstTsap(
                data.to_vec()
            ))),
            _ => {
                return Err(Error::Error(
                    format!(
                        "not support parameter: \
                         {}",
                        ty
                    )
                ));
            }
        }
    }

    fn encode(&self, dst: &mut BytesMut) {
        match self {
            Parameter::TpduSize(data) => {
                dst.put_u8(0xc0);
                dst.put_u8(1u8);
                dst.put_u8(data.clone().into())
            },
            Parameter::SrcTsap(data) => {
                dst.put_u8(0xc1);
                dst.put_u8(data.len() as u8);
                dst.extend_from_slice(
                    data.as_ref()
                )
            },
            Parameter::DstTsap(data) => {
                dst.put_u8(0xc2);
                dst.put_u8(data.len() as u8);
                dst.extend_from_slice(
                    data.as_ref()
                )
            }
        }
    }
}