package common

import (
  "bufio"
  "strconv"
)


type CPU struct {
  registers map[string]int
}

func NewCPU() *CPU {
  return &CPU{map[string]int{"X": 1}}
}

func (cpu CPU) GetRegisterValue(r string) int {
  return cpu.registers[r]
}


type Instruction interface {
  ExecuteCycle(*CPU) bool
}


type NoOp struct {
  currentCycle int
}

func NewNoOp() *NoOp {
  return &NoOp{}
}

func (instruction *NoOp) ExecuteCycle(cpu *CPU) bool {
  instruction.currentCycle++
  return instruction.currentCycle == 1
}


type AddX struct {
  parameter int
  currentCycle int
}

func NewAddX(parameter int) *AddX {
  return &AddX{parameter: parameter, currentCycle: 0}
}

func (instruction *AddX) ExecuteCycle(cpu *CPU) bool {
  instruction.currentCycle++
  if instruction.currentCycle == 2 {
    cpu.registers["X"] += instruction.parameter
    return true
  } else {
    return false
  }
}


type Program struct {
  instructions []Instruction
  currentInstruction int
}

func (program *Program) ExecuteCycles(cpu *CPU, nCycles int) bool {
  for i := 0; i < nCycles && program.currentInstruction < len(program.instructions); i++ {
    done := program.instructions[program.currentInstruction].ExecuteCycle(cpu)
    if done {
      program.currentInstruction++
    }
  }
  return program.currentInstruction == len(program.instructions)
}


func Parse(scanner bufio.Scanner) Program {
  program := Program{}

  for scanner.Scan() {
    line := scanner.Text()

    var instruction Instruction
    switch line[0:4] {
      case "noop":
        instruction = NewNoOp()
      case "addx":
        value, _ := strconv.Atoi(line[5:])
        instruction = NewAddX(value)
    }
    program.instructions = append(program.instructions, instruction)
  }

  return program
}