package android.emu6502

import android.emu6502.instructions.BaseInstruction
import android.emu6502.instructions.Instruction
import android.emu6502.instructions.InstructionTarget
import android.emu6502.instructions.impl.*
import android.util.Log
import java.util.HashMap
import kotlin.reflect.KMemberFunction0

class CPU(val memory: Memory) {
  // Accumulator
  var A: Int = 0
  // Registers
  var X: Int = 0
  var Y: Int = 0
  // Program counter
  var PC: Int = 0x600
  // Stack pointer
  var SP: Int = 0xFF
  // Processor flags
  var P: Int = 0x30
  private var isRunning = false
  private var debug = false
  private var monitoring = false
  private var TAG = "CPU"
  val instructionList: HashMap<Int, InstructionTarget> = HashMap()
  private val operationList: HashMap<Instruction, BaseInstruction> = hashMapOf(
      Pair(Instruction.ADC, ADC(this)),
      Pair(Instruction.AND, AND(this)),
      Pair(Instruction.ASL, ASL(this)),
      Pair(Instruction.BIT, BIT(this)),
      Pair(Instruction.LDA, LDA(this)),
      Pair(Instruction.LDX, LDX(this)),
      Pair(Instruction.LDY, LDY(this)),
      Pair(Instruction.STA, STA(memory, this)),
      Pair(Instruction.STX, STX(this)),
      Pair(Instruction.TAX, TAX(this)),
      Pair(Instruction.INX, INX(this)),
      Pair(Instruction.DEX, DEX(this)),
      Pair(Instruction.ORA, ORA(this)),
      Pair(Instruction.CPX, CPX(this)),
      Pair(Instruction.BRK, BRK(this)),
      Pair(Instruction.BNE, BNE(this)),
      Pair(Instruction.JMP, JMP(this)),
      Pair(Instruction.JSR, JSR(this)),
      Pair(Instruction.RTS, RTS(this))
//      Pair(Instruction.BPL, BPL(this)),
//      Pair(Instruction.BMI, BMI(this)),
//      Pair(Instruction.BVC, BVC(this)),
//      Pair(Instruction.BVS, BVS(this)),
//      Pair(Instruction.BCC, BCC(this)),
//      Pair(Instruction.BCS, BCS(this)),
//      Pair(Instruction.BEQ, BEQ(this)),
//      Pair(Instruction.CMP, CMP(this)),
//      Pair(Instruction.CPY, CPY(this)),
//      Pair(Instruction.DEC, DEC(this)),
//      Pair(Instruction.EOR, EOR(this)),
//      Pair(Instruction.CLC, CLC(this)),
//      Pair(Instruction.SEC, SEC(this)),
//      Pair(Instruction.CLI, CLI(this)),
//      Pair(Instruction.SEI, SEI(this)),
//      Pair(Instruction.CLV, CLV(this)),
//      Pair(Instruction.CLD, CLD(this)),
//      Pair(Instruction.SED, SED(this)),
//      Pair(Instruction.INC, INC(this)),
//      Pair(Instruction.LSR, LSR(this)),
//      Pair(Instruction.NOP, NOP(this)),
//      Pair(Instruction.TXA, TXA(this)),
//      Pair(Instruction.TAY, TAY(this)),
//      Pair(Instruction.TYA, TYA(this)),
//      Pair(Instruction.DEY, DEY(this)),
//      Pair(Instruction.INY, INY(this)),
//      Pair(Instruction.ROR, ROR(this)),
//      Pair(Instruction.ROL, ROL(this)),
//      Pair(Instruction.RTI, RTI(this)),
//      Pair(Instruction.SBC, SBC(this)),
//      Pair(Instruction.TXS, TXS(this)),
//      Pair(Instruction.TSX, TSX(this)),
//      Pair(Instruction.PHA, PHA(this)),
//      Pair(Instruction.PLA, PLA(this)),
//      Pair(Instruction.PHP, PHP(this)),
//      Pair(Instruction.PLP, PLP(this)),
//      Pair(Instruction.STY, STY(this))
  )

  fun execute() {
    isRunning = true
    while (true) {
      setRandomByte()
      executeNextInstruction()

      if (PC == 0 || !isRunning) {
        break
      }
    }
    stop()
    Log.i(TAG, "Program end at PC=$" + (PC - 1).toHexString() + ", A=$" + A.toHexString() +
               ", X=$" + X.toHexString() + ", Y=$" + Y.toHexString())
  }

  private fun executeNextInstruction() {
    val instruction = popByte()
    val target = instructionList.get(instruction)
    if (target != null) {
      val function = target.method
      target.operation.function()
    } else {
      Log.e(TAG, "Address $" + PC.toHexString() + " - unknown opcode " + instruction.toHexString())
      stop()
    }
  }

  fun stop() {
    isRunning = false
  }

   fun popByte(): Int {
    return memory.get(PC++).and(0xff)
  }

  private fun setRandomByte() {
    memory.set(0xfe, Math.floor(Math.random() * 256).toInt())
  }

  fun setSZFlagsForRegA() {
    setSVFlagsForValue(A)
  }

  fun setSZflagsForRegX() {
    setSVFlagsForValue(X)
  }

  private fun setSVFlagsForValue(value: Int) {
    if (value != 0) {
      P = P.and(0xfd)
    } else {
      P = P.or(0x02)
    }
    if (value.and(0x80) != 0) {
      P = P.or(0x80)
    } else {
      P = P.and(0x7f)
    }
  }

  fun popWord(): Int {
    return popByte() + popByte().shl(8)
  }

  fun testADC(value: Int) {
    var tmp: Int
    if (A.xor(value).and(0x80) != 0) {
      CLV()
    } else {
      setOverflow()
    }

    if (decimalMode()) {
      tmp = A.and(0xf) + value.and(0xf) + P.and(1)
      if (tmp >= 10) {
        tmp = 0x10.or((tmp + 6).and(0xf))
      }
      tmp += A.and(0xf0) + value.and(0xf0)
      if (tmp >= 160) {
        SEC()
        if (overflow() && tmp >= 0x180) {
          CLV()
        }
        tmp += 0x60
      } else {
        CLC()
        if (overflow() && tmp < 0x80) {
          CLV()
        }
      }
    } else {
      tmp = A + value + P.and(1)
      if (tmp >= 0x100) {
        SEC()
        if (overflow() && tmp >= 0x180) {
          CLV()
        }
      } else {
        CLC()
        if (overflow() && tmp < 0x80) {
          CLV()
        }
      }
    }
    A = tmp.and(0xff)
    setSZFlagsForRegA()
  }

  private fun overflow(): Boolean {
    return P.and(0x40) != 0
  }

  private fun decimalMode(): Boolean {
    return P.and(8) != 0
  }

  private fun carry(): Boolean {
    return P.and(1) != 0
  }

  private fun negative(): Boolean {
    return P.and(0x80) != 0
  }

  fun zero(): Boolean {
    return P.and(0x02) != 0
  }

  fun jumpBranch(offset: Int) {
    if (offset > 0x7f) {
      PC -= (0x100 - offset)
    } else {
      PC += offset
    }
  }

  fun doCompare(reg: Int, value: Int) {
    if (reg >= value) {
      SEC()
    } else {
      CLC()
    }
    setSVFlagsForValue(reg - value)
  }

  /** CLear Carry */
  private fun CLC() {
    P = P.and(0xfe)
  }

  /** SEt Carry */
  private fun SEC() {
    P = P.or(1)
  }

  /** CLear oVerflow */
  private fun CLV() {
    P = P.and(0xbf)
  }

  private fun setOverflow() {
    P = P.or(0x40)
  }

  fun stackPush(value: Int) {
    memory.set(SP.and(0xff) + 0x100, value.and(0xff))
    SP--
    if (SP < 0) {
      SP = SP.and(0xff)
      Log.i(TAG, "6502 Stack filled! Wrapping...")
    }
  }

  fun stackPop(): Int {
    SP++;
    if (SP >= 0x100) {
      SP = SP.and(0xff)
      Log.i(TAG, "6502 Stack emptied! Wrapping...")
    }
    return memory.get(SP + 0x100)
  }

  /**
   * http://nesdev.com/6502.txt
   * Returns the processor flags in the format SV-BDIZC
   * Sign - this is set if the result of an operation is negative, cleared if positive.
   * Overflow - when an arithmetic operation produces a result too large to be represented in a byte
   * Unused - Supposed to be logical 1 at all times.
   * Break - this is set when a software interrupt (BRK instruction) is executed.
   * Decimal Mode - When set, and an Add with Carry or Subtract with Carry instruction is executed,
   *  the source values are treated as valid BCD (Binary Coded Decimal, eg. 0x00-0x99 = 0-99) numbers.
   *  The result generated is also a BCD number.
   * Interrupt - If it is set, interrupts are disabled. If it is cleared, interrupts are enabled.
   * Zero - this is set to 1 when any arithmetic or logical operation produces a zero result, and is
   *  set to 0 if the result is non-zero.
   * Carry - this holds the carry out of the most significant bit in any arithmetic operation.
   *  In subtraction operations however, this flag is cleared - set to 0 - if a borrow is required,
   *  set to 1 - if no borrow is required. The carry flag is also used in shift and rotate logical
   *  operations.
   * */
  fun flags(): String {
    val flags = StringBuilder()
    for (i in 7 downTo 0) {
      flags.append(P.shr(i).and(1))
    }
    return flags.toString()
  }
}