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))
}

const SCENE_WIDTH = 1400
const SCENE_HEIGHT = 788
const SCENE_ASPECT_RATIO = SCENE_WIDTH / SCENE_HEIGHT

function getChapterLayoutMetrics(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 statusBarHeight = Math.max(
    0,
    finiteNumber(windowInfo.statusBarHeight, 0),
  )
  const safeTop = Math.max(
    0,
    statusBarHeight,
    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 hasExplicitMenuTop = Number.isFinite(Number(menuRect.top))
    && Number(menuRect.top) >= 0
  const menuTop = hasExplicitMenuTop ? Number(menuRect.top) : 0
  const menuBottom = finiteNumber(menuRect.bottom, 0)
  const explicitMenuHeight = Number(menuRect.height)
  const menuHeight = Number.isFinite(explicitMenuHeight)
    && explicitMenuHeight > 0
    ? explicitMenuHeight
    : (
      hasExplicitMenuTop && menuBottom > menuTop
        ? menuBottom - menuTop
        : 32
    )
  const hasMenuRect = menuLeft > 0
    && menuLeft < windowWidth
    && menuBottom > 0

  // 横屏 rpx 按屏幕宽度换算；576px 高的设备仍属于短高屏。
  // 这里使用实际 windowHeight，而不是设备型号或像素比。
  const compactHeight = windowHeight <= 620
  // Every visible top-bar action has a 48px minimum target. Keep the
  // calculated row at least as tall so compact landscape phones do not clip
  // the button above or below the explicit top-bar height.
  const rowHeight = Math.max(48, menuHeight)
  const inferredMenuTop = hasMenuRect
    ? (
      hasExplicitMenuTop
        ? menuTop
        : Math.max(safeTop, menuBottom - menuHeight)
    )
    : safeTop
  const topPadding = Math.max(
    safeTop,
    hasMenuRect
      ? inferredMenuTop - Math.max(0, (rowHeight - menuHeight) / 2)
      : safeTop + (compactHeight ? 3 : 5),
  )
  const bottomPadding = compactHeight ? 4 : 6
  const borderHeight = 3
  const topbarHeight = Math.ceil(
    topPadding + rowHeight + bottomPadding + borderHeight,
  )
  const leftInset = safeLeft + (compactHeight ? 10 : 14)
  const capsuleReserve = hasMenuRect
    ? Math.max(
      safeRight + (compactHeight ? 10 : 14),
      windowWidth - menuLeft + (compactHeight ? 8 : 10),
    )
    : safeRight + (compactHeight ? 12 : 16)
  const contentHeight = Math.max(
    1,
    windowHeight - topbarHeight - safeBottom,
  )
  const layoutWidth = Math.max(
    1,
    windowWidth - safeLeft - safeRight,
  )
  const sceneColumnWidth = layoutWidth * 0.6
  const stageWidth = Math.max(
    1,
    Math.min(sceneColumnWidth, contentHeight * SCENE_ASPECT_RATIO),
  )
  const stageHeight = stageWidth / SCENE_ASPECT_RATIO
  const markerWidth = compactHeight
    ? clamp(stageWidth * 0.24, 142, 170)
    : clamp(windowWidth / 750 * 200, 160, 220)
  const markerHeight = compactHeight
    ? 56
    : clamp(windowWidth / 750 * 86, 64, 94)

  return {
    windowWidth,
    windowHeight,
    compactHeight,
    safeLeft,
    safeRight,
    safeTop,
    safeBottom,
    topPadding,
    bottomPadding,
    rowHeight,
    topbarHeight,
    leftInset,
    capsuleReserve,
    modalTop: Math.max(
      safeTop + (compactHeight ? 4 : 8),
      hasMenuRect ? menuBottom + 4 : 0,
    ),
    stageWidth: Math.round(stageWidth),
    stageHeight: Math.round(stageHeight),
    markerWidth: Math.round(markerWidth),
    markerHeight: Math.round(markerHeight),
    sceneWidth: SCENE_WIDTH,
    sceneHeight: SCENE_HEIGHT,
    sceneAspectRatio: SCENE_ASPECT_RATIO,
  }
}

function getMarkerPosition(position = {}, metrics = {}) {
  const widthPercent = finiteNumber(position.widthPercent, 0)
  const heightPercent = finiteNumber(position.heightPercent, 0)
  const rawX = finiteNumber(position.xPercent, 50) + widthPercent / 2
  const rawY = finiteNumber(position.yPercent, 50) + heightPercent / 2
  const stageWidth = Math.max(1, finiteNumber(metrics.stageWidth, 500))
  const stageHeight = Math.max(1, finiteNumber(metrics.stageHeight, 280))
  const markerWidth = finiteNumber(metrics.markerWidth, 168)
  const markerHeight = finiteNumber(metrics.markerHeight, 64)
  const horizontalMargin = clamp(
    markerWidth / 2 / stageWidth * 100 + 1.5,
    2,
    48,
  )
  const verticalMargin = clamp(
    markerHeight / 2 / stageHeight * 100 + 2,
    2,
    48,
  )
  const clampedX = clamp(rawX, horizontalMargin, 100 - horizontalMargin)
  const clampedY = clamp(rawY, verticalMargin, 100 - verticalMargin)

  return {
    xPercent: clampedX,
    yPercent: clampedY,
    xPx: Math.round(clampedX / 100 * stageWidth),
    yPx: Math.round(clampedY / 100 * stageHeight),
  }
}

module.exports = {
  SCENE_WIDTH,
  SCENE_HEIGHT,
  SCENE_ASPECT_RATIO,
  getChapterLayoutMetrics,
  getMarkerPosition,
}