package mtmc.asm.instructions

import mtmc.asm.Assembler
import mtmc.tokenizer.MTMCToken
import mtmc.util.BinaryUtils

class JumpInstruction(
  type: InstructionType,
  label: List<MTMCToken>,
  instructionToken: MTMCToken
) : Instruction(type, label, instructionToken) {
  private var addressToken: MTMCToken? = null

  fun setAddressToken(addressToken: MTMCToken) {
    this.addressToken = addressToken
  }

  override fun validateLabel(assembler: Assembler) {
    if (addressToken!!.type == MTMCToken.TokenType.IDENTIFIER) {
      if (!assembler.hasLabel(addressToken!!.stringValue)) {
        addError("Unresolved label: " + addressToken!!.stringValue)
      }
    }
  }

  private fun resolveTargetAddress(assembler: Assembler): Int? {
    if (addressToken!!.type == MTMCToken.TokenType.IDENTIFIER) {
      return assembler.resolveLabel(addressToken!!.stringValue)
    } else {
      return addressToken!!.intValue()
    }
  }

  override fun genCode(output: ByteArray, assembler: Assembler) {
    var opcode = 0
    when (type) {
      InstructionType.J -> opcode = 12
      InstructionType.JZ -> opcode = 13
      InstructionType.JNZ -> opcode = 14
      InstructionType.JAL -> opcode = 15
      else -> println("Invalid instruction type")
    }
    val address = resolveTargetAddress(assembler)!!
    output[location] = (opcode shl 4 or (address ushr 8)).toByte()
    output[location + 1] = address.toByte()
  }

  companion object {
    fun disassemble(instruction: Short): String? {
      if (BinaryUtils.getBits(16, 2, instruction).toInt() == 3) {
        val jumpType = BinaryUtils.getBits(14, 2, instruction)
        val sb = StringBuilder()
        if (jumpType.toInt() == 0) {
          sb.append("j")
        } else if (jumpType.toInt() == 1) {
          sb.append("jz")
        } else if (jumpType.toInt() == 2) {
          sb.append("jnz")
        } else if (jumpType.toInt() == 3) {
          sb.append("jal")
        }
        val target = BinaryUtils.getBits(12, 12, instruction)
        sb.append(" ").append(target.toInt())
        return sb.toString()
      }
      return null
    }
  }
}