package BACK

import chisel3._
import chisel3.util._


class CDR_Master_Interface_Bundle extends CDRData{
  val op       = UInt(2.W)
}

class SpiSlvIO extends Bundle{
  val CS   = Input(Bool())
  val MISO = Output(Bool())
  val MOSI = Input(Bool())
  val SCK  = Input(Bool())

  val clk4 = Input(Bool())

  val CDRIn  = Flipped(Decoupled(new CDRData))
  val CDROut = Decoupled(new CDRData)

}

class SpiSlv extends Module{
  val io: SpiSlvIO = IO(new SpiSlvIO)

  val CDROutValidSet      = Wire(Bool())
  val CDROutValidSetAsync = ShiftRegister(CDROutValidSet, 2, false.B, true.B)
  val CDROutValidReset    = RegNext(CDROutValidSetAsync, false.B)

  // val CDRInValidSet = RegInit(false.B)
  val CDRInValidReset = Wire(Bool())
  val CDRInValidResetAsync = ShiftRegister( CDRInValidReset, 2, false.B, true.B)

  val cent = Wire(new CDR_Master_Interface_Bundle)
  withClockAndReset( io.clk4.asClock, reset ){
    val centReg = RegInit(0.U.asTypeOf(new CDR_Master_Interface_Bundle)); cent := centReg
    val sckShift = ShiftRegisters( io.SCK, 4, false.B, true.B )
    val csShift  = ShiftRegisters( io.CS, 4, true.B, true.B )


    val CDROutValidSetReg        = RegInit(false.B); CDROutValidSet := CDROutValidSetReg
    val CDROutValidResetAsync = ShiftRegister( CDROutValidReset, 2, false.B, true.B )

    val CDRInValidSetAsync = ShiftRegister( io.CDRIn.valid , 2, false.B, true.B )
    val CDRInValidResetReg = RegNext(CDRInValidSetAsync & csShift(3) & ~CDROutValidSetReg, false.B); CDRInValidReset := CDRInValidResetReg

    when( CDROutValidSetReg & CDROutValidResetAsync ){
      CDROutValidSetReg := false.B
      centReg.op := 1.U
    } .elsewhen( ~csShift(3) & csShift(2) ){
      CDROutValidSetReg := true.B
    }

    io.MISO := centReg.asUInt.extract( 6+8+32+2+16-1 )

    val sckPosedge = ~sckShift(3) & sckShift(2)
    val sckNegedge = sckShift(3) & ~sckShift(2)

    when( ~csShift(3) ){
      when( sckNegedge ){
        centReg := Cat(centReg.asUInt( 6+8+32+2+16-2, 0 ), io.MOSI).asTypeOf(new CDR_Master_Interface_Bundle)
      }
    } .otherwise{
      when( CDRInValidSetAsync & ~CDROutValidSetReg ){
        centReg.address  := io.CDRIn.bits.address
        centReg.register := io.CDRIn.bits.register
        centReg.data     := io.CDRIn.bits.data
        centReg.op       := 0.U
      }
    }
  }

  val CDROutValid = RegInit(false.B); io.CDROut.valid := CDROutValid
  val CDROutInfo  = Reg(new CDRData); io.CDROut.bits  := CDROutInfo

  when( io.CDROut.fire ){
    CDROutValid := false.B
  } .elsewhen( CDROutValidSet & ~CDROutValidSetAsync ){
    CDROutValid := true.B
    CDROutInfo  := cent
  }

  io.CDRIn.ready := CDRInValidResetAsync

}