let gameState = {
  running: false,
  pixelSize: 0,
  lastReported: null,
  frameTimes: [],
  frames: 0,
  width: 0,
  height: 0,
  canvas: null,
  ctx: null,
  gameExports: null
}

const initialMessage = "Click the board above to start simulation"

export async function setup(params, wasmModule) {
  const { canvas: canvasSelector } = params;
  gameState.gameExports = wasmModule.exports

  const canvas = gameState.canvas = document.querySelector(canvasSelector)
  gameState.ctx = gameState.canvas.getContext("2d")
  gameState.ctx.fillStyle = getComputedStyle(gameState.canvas).getPropertyValue('--foreground')

  const pixelSize = gameState.pixelSize = parseInt(canvas.getAttribute('data-pixelsize') || '2')
  gameState.width = Math.floor(parseInt(canvas.width) / pixelSize)
  gameState.height = Math.floor(parseInt(canvas.height) / pixelSize)

  initialize()
  drawBoard()

  const frameTimesElem = document.getElementById('frameTimes')
  const resetButton = document.getElementById('reset')

  frameTimesElem.innerText = initialMessage

  gameState.canvas.addEventListener('click', () => {
    if (!gameState.running) {
      if (frameTimesElem.innerText === initialMessage)
        frameTimesElem.innerText = 'Starting...'

      gameState.running = true
      frameLoop()
    } else {
      gameState.running = false;
      gameState.frameTimes = []
      gameState.lastReported = null
    }
  })

  resetButton.addEventListener('click', () => {
    gameState.running = false
    gameState.frameTimes = []
    gameState.lastReported = null
    frameTimesElem.innerText = initialMessage
    initialize()
    drawBoard()
  })
}

export async function onThemeChange() {
  drawBoard()
  gameState.ctx.fillStyle = getComputedStyle(gameState.canvas).getPropertyValue('--foreground')
}

export async function cleanup() {
  gameState.running = false
}

function initialize() {
  const { gameExports, width, height } = gameState

  gameExports.initializeBoard(width, height)

  for (let row = 0; row < height; row++) {
    for (let column = 0; column < width; column++) {
      const filled = Math.random() > .5;
      gameExports.setValueAtPosition(row, column, filled ? 1 : 0)
    }
  }
}

function frameLoop() {
  const { gameExports, running, frameTimes } = gameState

  if (!gameState.lastReported)
    gameState.lastReported = performance.now()

  if (!running) return

  const beforeTick = performance.now()
  gameExports.tick()
  const afterTick = performance.now()
  drawBoard()
  const afterDraw = performance.now()

  // Push raw frame time
  frameTimes.push(afterDraw - beforeTick)

  if (frameTimes.length >= 10) {
    const averageFrame = (frameTimes.reduce((a, b) => a + b) / frameTimes.length).toFixed(2);

    const lastReported = gameState.lastReported
    const current = gameState.lastReported = performance.now()
    const tenFrameTime = (current - lastReported) / 1000
    const fps = Math.floor(10 / tenFrameTime).toFixed(0)
    gameState.frameTimes = []

    const pagesUsed = gameExports.getPagesUsed()

    document.getElementById('frameTimes').innerHTML =
      `Frames per second: ${fps}<br/>
       Milliseconds per frame: ${averageFrame}<br/>
       Memory allocated: ${pagesUsed} pages (${pagesUsed * 64} KiB)`
  }

  const tickMS = (afterTick - beforeTick).toFixed(3).padStart(7, ' ')
  const drawMS = (afterDraw -  afterTick).toFixed(3).padStart(7, ' ')

  console.log(`tick took ${tickMS}ms, draw took ${drawMS}ms`)

  requestAnimationFrame(frameLoop)
}

function drawBoard() {
  const { gameExports, width, height, pixelSize, ctx, canvas } = gameState

  ctx.clearRect(0, 0, canvas.width, canvas.height)
  ctx.beginPath()
  for (let row = 0; row < height; row++) {
    for (let column = 0; column < width; column++) {
      const alive = gameExports.getValueAtPosition(row, column)

      if (!alive) continue

      const x = column * pixelSize
      const y = row * pixelSize

      ctx.moveTo(x, y)
      ctx.lineTo(x + pixelSize, y)
      ctx.lineTo(x + pixelSize, y + pixelSize)
      ctx.lineTo(x, y + pixelSize)
      ctx.lineTo(x, y)
    }
  }
  ctx.fill()
}