const SCREEN_WIDTH = 256;
const SCREEN_HEIGHT = 240;
const WORKING_MEMORY = 0x800;
const SAMPLE_REDUCTION = 4;

const jsnes = require('jsnes')
const { Subject } = require('rxjs')

const chunk = (a, l) => Array(Math.ceil(a.length / l)).fill().map((_, i) => (a.slice ? a.slice(i * l, i * l + l) : a.substr(i * l, i * l + 1)))
const sample = (a, n) => Array(Math.floor(a.length / n)).fill().map((_, i) => a[i * n])

class NES {
  constructor(rom) {
    this.nes = new jsnes.NES({
      onFrame: this.onFrame.bind(this)
    })
    this.nes.loadROM(rom)
    this.frameCount = 0
    this.packetBuffer = new ArrayBuffer(256 * 4 + SCREEN_WIDTH * SCREEN_HEIGHT + WORKING_MEMORY)
    this.paletteBuffer = new Uint32Array(this.packetBuffer)
    this.pixelBuffer = new Uint8ClampedArray(this.packetBuffer, 256 * 4)
    this.copyMemoryBuffer = new Uint8Array(this.packetBuffer, 256 * 4 + SCREEN_WIDTH * SCREEN_HEIGHT, WORKING_MEMORY)
    this.frameBuffer = new ArrayBuffer(SCREEN_WIDTH * SCREEN_HEIGHT * 4)
    this.screen32 = new Uint32Array(this.frameBuffer)
    this.nes.ppu.buffer = this.screen32
    this.frameBytes = new Uint8ClampedArray(this.frameBuffer)
    this.frames = new Subject()
  }

  command(data) {
    if (data.type === 'button') {
      const player = data.player || 1
      this.nes.controllers[player].state[data.button] = data.pressed ? 0x41 : 0x40
    }
  }


  onFrame(frameBuffer) {
    //console.log('frames.next' + Date.now())
    const colorMap = new Map()
    for (let i = 0; i < 256; i++) {
      this.paletteBuffer[i] = this.nes.ppu.palTable.curTable[i]
      colorMap.set(this.nes.ppu.palTable.curTable[i], i)
    }
    for (let i = 0; i < this.screen32.length; i++) {
      this.pixelBuffer[i] = colorMap.get(this.screen32[i])
    }
    for (let i = 0; i < WORKING_MEMORY; i++) {
      this.copyMemoryBuffer[i] = this.nes.cpu.mem[i]
    }
    this.frames.next(this.packetBuffer)
  }

  genie(code) {
    const map = { A: 0x0, P: 0x1, Z: 0x2, L: 0x3, G: 0x4, I: 0x5, T: 0x6, Y: 0x7, E: 0x8, O: 0x9, X: 0xA, U: 0xB, K: 0xC, S: 0xD, V: 0xE, N: 0xF }
    const [n0, n1, n2, n3, n4, n5, n6, n7] = code.split('').map(c => map[c])
    let address, data, compare
    
    address = 0x8000 + 
    ((n3 & 7) << 12)
    | ((n5 & 7) << 8) | ((n4 & 8) << 8)
    | ((n2 & 7) << 4) | ((n1 & 8) << 4)
    |  (n4 & 7)       |  (n3 & 8)
    
    if (code.length === 6) {
      data = ((n1 & 7) << 4) | ((n0 & 8) << 4) | (n0 & 7)       |  (n5 & 8)
      compare = null
    } else {
      data = ((n1 & 7) << 4) | ((n0 & 8) << 4) | (n0 & 7)       |  (n7 & 8)
      compare = ((n7 & 7) << 4) | ((n6 & 8) << 4) | (n6 & 7)       |  (n5 & 8)
    }
    this.hack(address, data, compare)
  }

  hack(address, data, compare = null) {
    let val = this.nes.cpu.mem[address]
    Object.defineProperty(this.nes.cpu.mem, address, {
      get: () => compare === null || val === compare
        ? data
        : val,
      set: v => (val = v)
    })
  }

  start() {
    if (!this.timer) this.timer = setInterval(() => this.nes.frame(), 1000 / 60)
  }

  stop() {
    if (this.timer) {
      clearInterval(this.timer)
      this.timer = null
    }
  }

}

module.exports = NES