package BACK

import chisel3._
import chisel3.util._


class SlaveRecParserIO extends Module{
  val rec  = Flipped( Decoupled(new AXIS_Bundle(8)) )

  val data = Decoupled(UInt(8.W))

  val stateNext = Output(UInt(4.W))
  val stateCurr = Output(UInt(4.W))

  val frameReq = Valid( new FrameHeader )
  val subMsgReq = Valid( new SubMsgHeader )

  val resp = Input(Bool())
  val isError = Output(Bool())


}

class SlaveRecParser extends Module{
  val io: SlaveRecParserIO = IO(new SlaveRecParserIO)


  val FRAME_STYLE_COMMON = 0.U
  val FRAME_STYLE_PROBE  = 1.U


  val STATE_IDLE            = 0.U //空闲
  val STATE_HEADER          = 1.U //长度/ /保留2bits //包类型
  val STATE_PAYLOAD_INDEX_STYLE   = 2.U //子报文设备索引 //子报文类型
  val STATE_PAYLOAD_ADDR    = 3.U //子报文地址
  val STATE_PAYLOAD_OP_LENGTH   = 4.U //子报文命令类型 //子报文长度
  val STATE_PAYLOAD_WORKCNT = 5.U //子报文工作计数
  val STATE_PAYLOAD_DATA    = 6.U //子报文数据
  val STATE_CRC             = 7.U //CRC校验
  val STATE_ERROR           = 8.U //
  val STATE_WAIT = 9.U


  val stateNext = Wire(UInt(4.W)); io.stateNext := stateNext
  val stateCurr = RegNext(stateNext, STATE_IDLE(4.W)); io.stateCurr := stateCurr

  val lengthCnt = Reg(UInt(11.W)) //动态计数器
  val frameLenCnt  = Reg(UInt(12.W)) //帧长度计数
  val isCrcPass: Bool
  val isShortRx: Bool //接收长度小于预期


  val frameLenAim  = Reg(UInt(12.W)); io.frameLenAim := frameLenAim //帧长度目标
  val frameStyle = Reg(UInt(2.W)); io.frameStyle := frameStyle //包类型
  val devIndex = Reg(UInt(14.W)); io.subMsgReq.devIndex := devIndex // 子报文中设备索引
  val style    = Reg(UInt(2.W)); io.subMsgReq.style := style  // 子报文类型
  val address  = Reg(UInt(16.W)); io.subMsgReq.address := address //子报文地址
  val operator = Reg(UInt(4.W)); io.subMsgReq.operator := operator   //子报文命令类型
  val length   = Reg(UInt(12.W)); io.subMsgReq.length := length //子报文负载长度
  val workCnt  = Reg(UInt(16.W)); io.subMsgReq.workCnt := workCnt //子报文工作计数


  when( stateCurr === STATE_HEADER & lengthCnt === 0.U ){
    frameLenAim := io.rec.bits.tdata << 4
  } .elsewhen( stateCurr === STATE_HEADER & lengthCnt === 1.U ){
    frameLenAim := frameLenAim | io.rec.bits.tdata(7,4)
    frameStyle  := io.rec.bits.tdata(1,0)
  }

  when( stateCurr === STATE_PAYLOAD_INDEX_STYLE & lengthCnt === 0.U ){
    devIndex := io.rec.bits.tdata << 6
  } .elsewhen( stateCurr === STATE_PAYLOAD_INDEX_STYLE & lengthCnt === 1.U ){
    devIndex := devIndex | io.rec.bits.tdata(7,2)
    style    := io.rec.bits.tdata(1,0)
  }

  when( stateCurr === STATE_PAYLOAD_ADDR & lengthCnt === 0.U ){
    address := io.rec.bits.tdata << 8
  } .elsewhen( stateCurr === STATE_PAYLOAD_ADDR & lengthCnt === 1.U ){
    address := address | io.rec.bits.tdata
  }

  when( stateCurr === STATE_PAYLOAD_OP_LENGTH & lengthCnt === 0.U ){
    operator := io.rec.bits.tdata(7,4)
    length   := io.rec.bits.tdata(3,0) << 8
  } .elsewhen( stateCurr === STATE_PAYLOAD_OP_LENGTH & lengthCnt === 1.U ){
    length   := length | io.rec.bits.tdata(7,0)
  }

  when( stateCurr === STATE_PAYLOAD_WORKCNT & lengthCnt === 0.U ){
    workCnt := io.rec.bits.tdata(7,0) << 8
  } .elsewhen( stateCurr === STATE_PAYLOAD_WORKCNT & lengthCnt === 1.U ){
    workCnt := workCnt | io.rec.bits.tdata(7,0)
  }


  stateNext := 
    Mux1H(Seq(
                                                        //必须使用上升沿触发，以避免前一帧长度超过预期
      ( stateCurr === STATE_IDLE                ) -> Mux( ~RegNext(io.rec.valid) & io.rec.axis.valid, STATE_HEADER, STATE_IDLE ), 
      ( stateCurr === STATE_HEADER              ) -> Mux( isShortRx, STATE_ERROR,
          Mux( lengthCnt === 0, STATE_HEADER,
            MuxCase( STATE_ERROR, Array(
              ( io.rec.bits(1,0) === FRAME_STYLE_COMMON ) -> STATE_PAYLOAD_INDEX_STYLE,
              ( io.rec.bits(1,0) === FRAME_STYLE_PROBE  ) -> STATE_CRC,
            ))
          )
        ),
      ( stateCurr === STATE_PAYLOAD_INDEX_STYLE ) -> Mux( isShortRx, STATE_ERROR,
          Mux( lengthCnt === 0, STATE_PAYLOAD_INDEX_STYLE, STATE_PAYLOAD_ADDR )
        ),
      ( stateCurr === STATE_PAYLOAD_ADDR        ) -> Mux( isShortRx, STATE_ERROR,
          Mux( lengthCnt === 0, STATE_PAYLOAD_ADDR, STATE_PAYLOAD_OP_LENGTH )
        ),
      ( stateCurr === STATE_PAYLOAD_OP_LENGTH   ) -> Mux( isShortRx, STATE_ERROR,
          Mux( lengthCnt === 0, STATE_PAYLOAD_OP_LENGTH, STATE_PAYLOAD_WORKCNT )
        ),
      ( stateCurr === STATE_PAYLOAD_WORKCNT     ) -> Mux( isShortRx, STATE_ERROR,
          Mux( lengthCnt === 0.U, STATE_PAYLOAD_WORKCNT, STATE_PAYLOAD_DATA )
        ),
      ( stateCurr === STATE_PAYLOAD_DATA        ) -> Mux( isShortRx, STATE_ERROR,
          Mux( lengthCnt === ( subMsgLen - 1.U), 
            Mux( frameLenCnt === frameLenAim, STATE_CRC, STATE_PAYLOAD_INDEX_STYLE
          ), STATE_PAYLOAD_DATA )
        ),
      ( stateCurr === STATE_CRC                 ) -> Mux( isShortRx, STATE_ERROR,
          Mux( lengthCnt === (4 - 1).U, Mux( isCrcPass, STATE_IDLE, STATE_ERROR), STATE_CRC )
        ),
      ( stateCurr === STATE_ERROR               ) -> Mux( io.resp, STATE_IDLE, STATE_ERROR ), 
      ( stateCurr === STATE_WAIT                ) -> Mux( io.resp, STATE_IDLE, STATE_ERROR )
    ))



}