function finiteNumber(value, fallback = 0) {
  const parsed = Number(value)
  return Number.isFinite(parsed) ? parsed : fallback
}

function clamp(value, minimum, maximum) {
  return Math.min(maximum, Math.max(minimum, value))
}

/**
 * 首页使用自定义导航栏，横屏时既要避开左右刘海与底部 Home
 * Indicator，也要为微信右上角胶囊留下真实空间。CSS 的 env()
 * 在部分微信横屏机型上只会返回系统安全区，不包含胶囊，因此这里
 * 以运行时尺寸为准，CSS env() 只作为脚本尚未执行时的兜底。
 */
function getHomeLayoutMetrics(windowInfo = {}, menuRect = {}) {
  const windowWidth = Math.max(320, finiteNumber(windowInfo.windowWidth, 844))
  const windowHeight = Math.max(240, finiteNumber(windowInfo.windowHeight, 390))
  const safeArea = windowInfo.safeArea || {}

  const safeLeft = clamp(
    finiteNumber(safeArea.left, 0),
    0,
    windowWidth / 3,
  )
  const safeRightEdge = clamp(
    finiteNumber(safeArea.right, windowWidth),
    windowWidth * 2 / 3,
    windowWidth,
  )
  const safeRight = clamp(
    windowWidth - safeRightEdge,
    0,
    windowWidth / 3,
  )
  const safeTop = Math.max(
    0,
    finiteNumber(windowInfo.statusBarHeight, 0),
    finiteNumber(safeArea.top, 0),
  )
  const safeBottomEdge = clamp(
    finiteNumber(safeArea.bottom, windowHeight),
    windowHeight * 2 / 3,
    windowHeight,
  )
  const safeBottom = clamp(
    windowHeight - safeBottomEdge,
    0,
    windowHeight / 3,
  )

  const menuLeft = finiteNumber(menuRect.left, windowWidth)
  const menuBottom = finiteNumber(menuRect.bottom, 0)
  const hasMenuRect = (
    menuLeft > windowWidth / 2
    && menuLeft < windowWidth
    && menuBottom > 0
  )
  const compactHeight = windowHeight <= 620
  const horizontalPageGap = compactHeight ? 10 : 14
  const capsuleGap = compactHeight ? 8 : 10

  const leftInset = Math.ceil(safeLeft + horizontalPageGap)
  const rightInset = Math.ceil(Math.max(
    safeRight + horizontalPageGap,
    hasMenuRect
      ? windowWidth - menuLeft + capsuleGap
      : safeRight + horizontalPageGap,
  ))
  const topInset = Math.ceil(safeTop + (compactHeight ? 8 : 12))
  const bottomInset = Math.ceil(safeBottom + (compactHeight ? 7 : 12))

  return {
    windowWidth,
    windowHeight,
    compactHeight,
    safeLeft,
    safeRight,
    safeTop,
    safeBottom,
    leftInset,
    rightInset,
    topInset,
    bottomInset,
    hasMenuRect,
  }
}

function getHomeLayoutStyle(metrics = {}) {
  return [
    `height:${Math.max(240, finiteNumber(metrics.windowHeight, 390))}px`,
    `--home-top-inset:${Math.max(0, finiteNumber(metrics.topInset, 8))}px`,
    `--home-right-inset:${Math.max(0, finiteNumber(metrics.rightInset, 10))}px`,
    `--home-bottom-inset:${Math.max(0, finiteNumber(metrics.bottomInset, 7))}px`,
    `--home-left-inset:${Math.max(0, finiteNumber(metrics.leftInset, 10))}px`,
  ].join(';')
}

function hasReadingProgress(progress = {}) {
  const completedChapters = Array.isArray(progress.completedChapters)
    ? progress.completedChapters
    : []
  const completedHotspots = progress.completedHotspots
    && typeof progress.completedHotspots === 'object'
    ? progress.completedHotspots
    : {}
  const hasCompletedHotspot = Object.values(completedHotspots).some(
    (ids) => Array.isArray(ids) && ids.length > 0,
  )

  return (
    completedChapters.length > 0
    || finiteNumber(progress.lastChapter, 1) > 1
    || hasCompletedHotspot
  )
}

module.exports = {
  getHomeLayoutMetrics,
  getHomeLayoutStyle,
  hasReadingProgress,
}