// Some non-bold Fraktur symbols are outside the contiguous block
const frakturExceptions = {
  'C': '\u212d',
  'H': '\u210c',
  'I': '\u2111',
  'R': '\u211c',
  'Z': '\u2128'
}

// constants for decoding the update blob
const SEQ_SET_COLOR_ATTR = 1
const SEQ_REPEAT = 2
const SEQ_SET_COLOR = 3
const SEQ_SET_ATTR = 4

const themes = [
  [
    '#111213',
    '#CC0000',
    '#4E9A06',
    '#C4A000',
    '#3465A4',
    '#75507B',
    '#06989A',
    '#D3D7CF',
    '#555753',
    '#EF2929',
    '#8AE234',
    '#FCE94F',
    '#729FCF',
    '#AD7FA8',
    '#34E2E2',
    '#EEEEEC'
  ]
]

class TermScreen {
  constructor () {
    this.canvas = document.createElement('canvas')
    this.ctx = this.canvas.getContext('2d')

    if ('AudioContext' in window || 'webkitAudioContext' in window) {
      this.audioCtx = new (window.AudioContext || window.webkitAudioContext)()
    } else {
      console.warn('No AudioContext!')
    }

    this.cursor = {
      x: 0,
      y: 0,
      fg: 7,
      bg: 0,
      attrs: 0,
      blinkOn: false,
      visible: true,
      hanging: false,
      blinkInterval: null
    }

    this._colors = themes[0]

    this._window = {
      width: 0,
      height: 0,
      devicePixelRatio: 1,
      fontFamily: '"DejaVu Sans Mono", "Liberation Mono", "Inconsolata", ' +
        'monospace',
      fontSize: 20,
      gridScaleX: 1.0,
      gridScaleY: 1.2,
      blinkStyleOn: true,
      blinkInterval: null
    }
    this.windowState = {
      width: 0,
      height: 0,
      devicePixelRatio: 0,
      gridScaleX: 0,
      gridScaleY: 0,
      fontFamily: '',
      fontSize: 0
    }

    const self = this
    this.window = new Proxy(this._window, {
      set (target, key, value, receiver) {
        target[key] = value
        self.updateSize()
        self.scheduleDraw()
        return true
      }
    })

    this.screen = []
    this.screenFG = []
    this.screenBG = []
    this.screenAttrs = []

    this.resetBlink()
    this.resetCursorBlink()
  }

  get colors () { return this._colors }
  set colors (theme) {
    this._colors = theme
    this.scheduleDraw()
  }

  // schedule a draw in the next tick
  scheduleDraw () {
    clearTimeout(this._scheduledDraw)
    this._scheduledDraw = setTimeout(() => this.draw(), 1)
  }

  getFont (modifiers = {}) {
    let fontStyle = modifiers.style || 'normal'
    let fontWeight = modifiers.weight || 'normal'
    return `${fontStyle} normal ${fontWeight} ${
      this.window.fontSize}px ${this.window.fontFamily}`
  }

  getCharSize () {
    this.ctx.font = this.getFont()

    return {
      width: this.ctx.measureText(' ').width,
      height: this.window.fontSize
    }
  }

  updateSize () {
    this._window.devicePixelRatio = window.devicePixelRatio || 1

    let didChange = false
    for (let key in this.windowState) {
      if (this.windowState[key] !== this.window[key]) {
        didChange = true
        this.windowState[key] = this.window[key]
      }
    }

    if (didChange) {
      const {
        width, height, devicePixelRatio, gridScaleX, gridScaleY, fontSize
      } = this.window
      const charSize = this.getCharSize()

      this.canvas.width = width * devicePixelRatio * charSize.width * gridScaleX
      this.canvas.style.width = `${width * charSize.width * gridScaleX}px`
      this.canvas.height = height * devicePixelRatio * charSize.height *
        gridScaleY
      this.canvas.style.height = `${height * charSize.height * gridScaleY}px`
    }
  }

  resetCursorBlink () {
    clearInterval(this.cursor.blinkInterval)
    this.cursor.blinkInterval = setInterval(() => {
      this.cursor.blinkOn = !this.cursor.blinkOn
      this.scheduleDraw()
    }, 500)
  }

  resetBlink () {
    clearInterval(this.window.blinkInterval)
    let intervals = 0
    this.window.blinkInterval = setInterval(() => {
      intervals++
      if (intervals >= 4 && this.window.blinkStyleOn) {
        this.window.blinkStyleOn = false
        intervals = 0
      } else {
        this.window.blinkStyleOn = true
        intervals = 0
      }
    }, 200)
  }

  drawCell ({ x, y, charSize, cellWidth, cellHeight, text, fg, bg, attrs }) {
    const ctx = this.ctx
    ctx.fillStyle = this.colors[bg]
    ctx.globalCompositeOperation = 'destination-over'
    ctx.fillRect(x * cellWidth, y * cellHeight,
      Math.ceil(cellWidth), Math.ceil(cellHeight))
    ctx.globalCompositeOperation = 'source-over'

    let fontModifiers = {}
    let underline = false
    let blink = false
    let strike = false
    if (attrs & 1) fontModifiers.weight = 'bold'
    if (attrs & 1 << 1) ctx.globalAlpha = 0.5
    if (attrs & 1 << 2) fontModifiers.style = 'italic'
    if (attrs & 1 << 3) underline = true
    if (attrs & 1 << 4) blink = true
    if (attrs & 1 << 5) text = TermScreen.alphaToFraktur(text)
    if (attrs & 1 << 6) strike = true

    if (!blink || this.window.blinkStyleOn) {
      ctx.font = this.getFont(fontModifiers)
      ctx.fillStyle = this.colors[fg]
      ctx.fillText(text, (x + 0.5) * cellWidth, (y + 0.5) * cellHeight)

      if (underline || strike) {
        let lineY = underline
          ? y * cellHeight * charSize.height
          : (y + 0.5) * cellHeight

        ctx.strokeStyle = this.colors[fg]
        ctx.lineWidth = 1
        ctx.moveTo(x * cellWidth, lineY)
        ctx.lineTo((x + 1) * cellWidth, lineY)
        ctx.stroke()
      }
    }

    ctx.globalAlpha = 1
  }

  draw () {
    const ctx = this.ctx
    const {
      width,
      height,
      devicePixelRatio,
      fontFamily,
      fontSize,
      gridScaleX,
      gridScaleY
    } = this.window

    const charSize = this.getCharSize()
    const cellWidth = charSize.width * gridScaleX
    const cellHeight = charSize.height * gridScaleY
    const screenWidth = width * cellWidth
    const screenHeight = height * cellHeight
    const screenLength = width * height

    ctx.setTransform(this.window.devicePixelRatio, 0, 0,
      this.window.devicePixelRatio, 0, 0)
    ctx.clearRect(0, 0, screenWidth, screenHeight)

    ctx.font = this.getFont()
    ctx.textAlign = 'center'
    ctx.textBaseline = 'middle'

    for (let cell = 0; cell < screenLength; cell++) {
      let x = cell % width
      let y = Math.floor(cell / width)
      let isCursor = this.cursor.x === x && this.cursor.y === y

      let text = this.screen[cell]
      let fg = isCursor ? this.screenBG[cell] : this.screenFG[cell]
      let bg = isCursor ? this.screenFG[cell] : this.screenBG[cell]
      let attrs = this.screenAttrs[cell]

      if (isCursor && fg === bg) bg = fg === 0 ? 7 : 0

      this.drawCell({
        x, y, charSize, cellWidth, cellHeight, text, fg, bg, attrs
      })
    }
  }

  loadContent (str) {
    // current index
    let i = 0

    // window size
    this.window.height = parse2B(str, i)
    this.window.width = parse2B(str, i + 2)
    this.updateSize()
    i += 4

    // cursor position
    let [cursorY, cursorX] = [parse2B(str, i), parse2B(str, i + 2)]
    i += 4
    let cursorMoved = (cursorX !== this.cursor.x || cursorY !== this.cursor.y)
    this.cursor.x = cursorX
    this.cursor.y = cursorY

    if (cursorMoved) this.resetCursorBlink()

    // attributes
    let attributes = parse2B(str, i)
    i += 2

    this.cursor.visible = !!(attributes & 1)
    this.cursor.hanging = !!(attributes & 1 << 0)

    Input.setAlts(
      !!(attributes & 1 << 2), // cursors alt
      !!(attributes & 1 << 3), // numpad alt
      !!(attributes & 1 << 4)  // fn keys alt
    )

    let trackMouseClicks = !!(attributes & 1 << 5)
    let trackMouseMovement = !!(attributes & 1 << 6)

    Input.setMouseMode(trackMouseClicks, trackMouseMovement)

    let showButtons = !!(attributes & 1 << 7)
    let showConfigLinks = !!(attributes & 1 << 8)

    $('.x-term-conf-btn').toggleClass('hidden', !showConfigLinks)
    $('#action-buttons').toggleClass('hidden', !showButtons)

    // content
    let fg = 7
    let bg = 0
    let attrs = 0
    let cell = 0 // cell index
    let text = ' '
    let screenLength = this.window.width * this.window.height

    this.screen = new Array(screenLength).fill(' ')
    this.screenFG = new Array(screenLength).fill(' ')
    this.screenBG = new Array(screenLength).fill(' ')
    this.screenAttrs = new Array(screenLength).fill(' ')

    while (i < str.length && cell < screenLength) {
      let character = str[i++]
      let charCode = character.charCodeAt(0)

      if (charCode === SEQ_SET_COLOR_ATTR) {
        let data = parse3B(str, i)
        i += 3
        fg = data & 0xF
        bg = data >> 4 & 0xF
        attrs = data >> 8 & 0xFF
      } else if (charCode == SEQ_SET_COLOR) {
        let data = parse2B(str, i)
        i += 2
        fg = data & 0xF
        bg = data >> 4 & 0xF
      } else if (charCode === SEQ_SET_ATTR) {
        let data = parse2B(str, i)
        i += 2
        attrs = data & 0xFF
      } else if (charCode === SEQ_REPEAT) {
        let count = parse2B(str, i)
        i += 2
        for (let j = 0; j < count; j++) {
          this.screen[cell] = text
          this.screenFG[cell] = fg
          this.screenBG[cell] = bg
          this.screenAttrs[cell] = attrs

          if (++cell > screenLength) break
        }
      } else {
        // unique cell character
        this.screen[cell] = text = character
        this.screenFG[cell] = fg
        this.screenBG[cell] = bg
        this.screenAttrs[cell] = attrs
        cell++
      }
    }

    this.scheduleDraw()
    if (this.onload) this.onload()
  }

  /** Apply labels to buttons and screen title (leading T removed already) */
  loadLabels (str) {
    let pieces = str.split('\x01')
    qs('h1').textContent = pieces[0]
    $('#action-buttons button').forEach((button, i) => {
      var label = pieces[i + 1].trim()
      // if empty string, use the "dim" effect and put nbsp instead to
      // stretch the button vertically
      button.innerHTML = label ? e(label) : '&nbsp;';
      button.style.opacity = label ? 1 : 0.2;
    })
  }

  load (str) {
    const content = str.substr(1)

    switch (str[0]) {
      case 'S':
        this.loadContent(content)
        break
      case 'T':
        this.loadLabels(content)
        break
      case 'B':
        this.beep()
        break
      default:
        console.warn(`Bad data message type; ignoring.\n${
          JSON.stringify(content)}`)
    }
  }

  beep () {
    const audioCtx = this.audioCtx
    if (!audioCtx) return

    let osc, gain

    // main beep
    osc = audioCtx.createOscillator()
    gain = audioCtx.createGain()
    osc.connect(gain)
    gain.connect(audioCtx.destination);
    gain.gain.value = 0.5;
    osc.frequency.value = 750;
    osc.type = 'sine';
    osc.start();
    osc.stop(audioCtx.currentTime + 0.05);

    // surrogate beep (making it sound like 'oops')
    osc = audioCtx.createOscillator();
    gain = audioCtx.createGain();
    osc.connect(gain);
    gain.connect(audioCtx.destination);
    gain.gain.value = 0.2;
    osc.frequency.value = 400;
    osc.type = 'sine';
    osc.start(audioCtx.currentTime + 0.05);
    osc.stop(audioCtx.currentTime + 0.08);
  }

  static alphaToFraktur (character) {
    if ('a' <= character && character <= 'z') {
      character = String.fromCodePoint(0x1d51e - 0x61 + character.charCodeAt(0))
    } else if ('A' <= character && character <= 'Z') {
      character = frakturExceptions[character] || String.fromCodePoint(
        0x1d504 - 0x41 + character.charCodeAt(0))
    }
    return character
  }
}

const Screen = new TermScreen()
let didAddScreen = false
Screen.onload = function () {
  if (didAddScreen) return
  didAddScreen = true
  qs('#screen').appendChild(Screen.canvas)
}