package BACK

import chisel3._
import chisel3.util._

class SlaveParserIO extends Module{
  val downOut = Decoupled(new AXIS_Bundle(8))
  val downIn  = Flipped( Decoupled(new AXIS_Bundle(8)) )

  val upOut = Decoupled(new AXIS_Bundle(8))
  val upIn  = Flipped( Decoupled(new AXIS_Bundle(8)) )

  val sram
}

abstract class SlaveParserBase extends Module{
  val io: SlaveParserIO = IO(new SlaveParserIO)

  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   = 4.U //子报文设备索引 //子报文类型
  val STATE_PAYLOAD_ADDR    = 6.U //子报文地址
  val STATE_PAYLOAD_OP_LENGTH   = 7.U //子报文命令类型 //子报文长度
  val STATE_PAYLOAD_WORKCNT = 9.U //子报文工作计数
  val STATE_PAYLOAD_DATA    = 10.U //子报文数据
  val STATE_CRC             = 11.U //CRC校验
  val STATE_ERROR           = 12.U //


  val downStateNext = Wire(UInt(4.W))
  val downStateCurr = RegNext(downStateNext, STATE_IDLE(4.W))

  val lengthCnt = Reg(UInt(11.W)) //动态计数器
  //val subMsgCnt = Reg(UInt(7.W)) //子报文不超过128个
  val subMsgLenAim = Reg(UInt(12.W)) //子报文长度
  val frameLenAim  = Reg(UInt(12.W)) //帧长度目标
  val frameLenCnt  = Reg(UInt(12.W)) //帧长度计数
  val isCrcPass: Bool
  val isTxEnd: Bool
  val isShortRx: Bool //接收长度小于预期
  val frameStyle = Reg(UInt(2.W)) //包类型
  val devIndex = Reg(UInt(14.W)) //当前设备索引
  val subMsg_devIndex = Reg(UInt(14.W)) // 子报文中设备索引
  val subMsg_style    = Reg(UInt(2.W))  // 子报文类型
  val subMsg_address  = Reg(UInt(16.W)) //子报文地址
  val subMsg_operator = Reg(UInt(4.W))   //子报文命令类型
  val subMsg_length   = Reg(UInt(12.W)) //子报文负载长度
  val subMsg_workCnt  = Reg(UInt(16.W)) //子报文工作计数


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

  when( downStateCurr === STATE_PAYLOAD_INDEX_STYLE & lengthCnt === 0.U ){
    subMsg_devIndex := io.downIn.bits.tdata << 6
  } .elsewhen( downStateCurr === STATE_PAYLOAD_INDEX_STYLE & lengthCnt === 1.U ){
    subMsg_devIndex := subMsg_devIndex | io.downIn.bits.tdata(7,2)
    subMsg_style    := io.downIn.bits.tdata(1,0)
  }

  when( downStateCurr === STATE_PAYLOAD_ADDR & lengthCnt === 0.U ){
    subMsg_address := io.downIn.bits.tdata << 8
  } .elsewhen( downStateCurr === STATE_PAYLOAD_ADDR & lengthCnt === 1.U ){
    subMsg_address := subMsg_address | io.downIn.bits.tdata
  }

  when( downStateCurr === STATE_PAYLOAD_OP_LENGTH & lengthCnt === 0.U ){
    subMsg_operator := io.downIn.bits.tdata(7,4)
    subMsg_length   := io.downIn.bits.tdata(3,0) << 8
  } .elsewhen( downStateCurr === STATE_PAYLOAD_OP_LENGTH & lengthCnt === 1.U ){
    subMsg_length   := subMsg_length | io.downIn.bits.tdata(7,0)
  }

  when( downStateCurr === STATE_PAYLOAD_WORKCNT & lengthCnt === 0.U ){
    subMsg_workCnt := io.downIn.bits.tdata(7,0) << 8
  } .elsewhen( downStateCurr === STATE_PAYLOAD_WORKCNT & lengthCnt === 1.U ){
    subMsg_workCnt := subMsg_workCnt | io.downIn.bits.tdata(7,0)
  }


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

  // assert( ~(downStateCurr === STATE_HEADER              & ~io.downIn.axis.fire), "Assert Failed!" )
  // assert( ~(downStateCurr === STATE_PAYLOAD_INDEX_STYLE & ~io.downIn.axis.fire), "Assert Failed!" )
  // assert( ~(downStateCurr === STATE_PAYLOAD_ADDR        & ~io.downIn.axis.fire), "Assert Failed!" )
}





class SlaveParser extends SlaveParserBase{

}