// SPDX-License-Identifier: Apache-2.0

package chiselTests

import circt.stage.ChiselStage
import chisel3._
import chisel3.util._

class Risc extends Module {
  val io = IO(new Bundle {
    val isWr = Input(Bool())
    val wrAddr = Input(UInt(8.W))
    val wrData = Input(Bits(32.W))
    val boot = Input(Bool())
    val valid = Output(Bool())
    val out = Output(Bits(32.W))
  })
  val memSize = 256
  val file = Mem(memSize, Bits(32.W))
  val code = Mem(memSize, Bits(32.W))
  val pc = RegInit(0.U(8.W))

  val add_op :: imm_op :: Nil = Enum(2)

  val inst = code(pc)
  val op = inst(31, 24)
  val rci = inst(23, 16)
  val rai = inst(15, 8)
  val rbi = inst(7, 0)

  val ra = Mux(rai === 0.U, 0.U, file(rai))
  val rb = Mux(rbi === 0.U, 0.U, file(rbi))
  val rc = Wire(Bits(32.W))

  io.valid := false.B
  io.out := 0.U
  rc := 0.U

  when(io.isWr) {
    code(io.wrAddr) := io.wrData
  }.elsewhen(io.boot) {
    pc := 0.U
  }.otherwise {
    switch(op) {
      is(add_op) { rc := ra +% rb }
      is(imm_op) { rc := (rai << 8) | rbi }
    }
    io.out := rc
    when(rci === 255.U) {
      io.valid := true.B
    }.otherwise {
      file(rci) := rc
    }
    pc := pc +% 1.U
  }
}

/*
class RiscTester(c: Risc) extends Tester(c) {
  def wr(addr: BigInt, data: BigInt)  = {
    poke(c.io.isWr,   1)
    poke(c.io.wrAddr, addr)
    poke(c.io.wrData, data)
    step(1)
  }
  def boot()  = {
    poke(c.io.isWr, 0)
    poke(c.io.boot, 1)
    step(1)
  }
  def tick(isBoot: Boolean)  = {
    if (isBoot)
      poke(c.io.boot, 0)
    step(1)
  }
  def I (op: UInt, rc: Int, ra: Int, rb: Int) = {
    // val cr = Cat(op, rc.asUInt(8.W), ra.asUInt(8.W), rb.asUInt(8.W)).litValue
    val cr = op.litValue << 24 | rc << 16 | ra << 8 | rb
    println("I = " + cr)
    cr
  }

  val app  = Array(I(c.imm_op,   1, 0, 1), // r1 <- 1
                   I(c.add_op,   1, 1, 1), // r1 <- r1 + r1
                   I(c.add_op,   1, 1, 1), // r1 <- r1 + r1
                   I(c.add_op, 255, 1, 0)) // rh <- r1
  wr(0, 0) // skip reset
  for (addr <- 0 until app.length)
    wr(addr, app(addr))
  def dump(k: Int) {
    println("K = " + k)
    peek(c.ra)
    peek(c.rb)
    peek(c.rc)
    peek(c.io.out)
    peek(c.pc)
    peek(c.inst)
    peek(c.op)
    peek(c.rci)
    peek(c.rai)
    peek(c.rbi)
    peekAt(c.file, 1)
  }
  boot()
  dump(0)
  var k = 0
  do {
    tick(k == 0); k += 1
    dump(k)
  } while (!(peek(c.io.valid) == 1 || k > 10))
  expect(k <= 10, "TIME LIMIT")
  expect(c.io.out, 4)
}
 */

class RiscSpec extends ChiselPropSpec {

  property("Risc should elaborate") {
    ChiselStage.elaborate { new Risc }
  }

  ignore("RiscTester should return the correct result") {}
}
