pptList/src/utils/aiPptTemplateEngine.ts

import { nanoid } from "nanoid"
import { measureAiPptText, aiPptBlockHeight, aiPptTextGeometry } from "@/utils/aiPptTextMetrics"
import type {
  Gradient,
  PPTElement,
  PPTElementShadow,
  PPTImageElement,
  PPTVideoElement,
  PPTAudioElement,
  PPTCloudCoachElement,
  PPTLineElement,
  PPTAnimation,
  PPTShapeElement,
  PPTTextElement,
  Slide,
  SlideBackground,
  SlideTheme
} from "@/types/slides"
import type { AiCoursewareOutline, AiCoursewarePage } from "@/api/aiCourseware"
import { audioBindings, scoreBinding, isScorePage, usableResourceUrl, isTeacherFacingText, teacherFacingTexts, modelPageContent, rhythmRows } from "@/utils/aiPptContent"
import { compilePageDesign, hasModelPageDesign, externalVisual } from "@/utils/aiPptPageDesign"
import {
  AI_COURSEWARE_TEMPLATES,
  getAiCoursewarePalette,
  getAiCoursewareTemplate,
  DEFAULT_AI_COURSEWARE_TEMPLATE_ID,
  type AiCoursewareTemplateId,
  type AiCoursewareThemePalette
} from "@/config/aiCoursewareTemplates"
import {
  getAiCoursewareTemplateMaster,
  getTemplateMasterPage,
  selectTemplateMasterPageVariant,
  resolveTemplatePageLayout,
  validateTemplateMasterRegistry,
  type TemplateMaster,
  type TemplateMasterElement,
  type TemplateMasterPage,
  type TemplatePageRole,
  type TemplateSlot
} from "@/config/aiCoursewareTemplateMasters"

interface AiPptOptions {
  backgroundImage?: string
  enableAnimations?: boolean
  paletteVariant?: number
  templateId?: AiCoursewareTemplateId
}

type PageRole = TemplatePageRole

type Palette = AiCoursewareThemePalette

interface ImageRect {
  left: number
  top: number
  width: number
  height: number
  radius?: number
}

interface PageRenderIntent {
  role: PageRole
  density: "low" | "medium" | "high"
  visualKind: "image" | "notation" | "rhythm" | "compare" | "activity" | "text"
  showMedia: boolean
}

const SLIDE_WIDTH = 1600
const SLIDE_HEIGHT = 900
const VIEWPORT_WIDTH = 1920
const VIEWPORT_HEIGHT = 1080
const VIEWPORT_SCALE = VIEWPORT_WIDTH / SLIDE_WIDTH
const FONT_NAME = "Microsoft Yahei"
const GENERIC_PAGE_TITLES = new Set(["封面", "课程导入", "故事导入", "导入", "首页", "cover"])

export function buildAiPptSlides(
  outline: AiCoursewareOutline,
  options: AiPptOptions = {}
): { title: string; theme: Partial<SlideTheme>; slides: Slide[] } {
  const normalized = normalizeOutline(outline)
  validateTemplateMasterRegistry(AI_COURSEWARE_TEMPLATES.map(template => template.id))
  const requestedTemplateId = options.templateId || normalized.templateId
  const templateId = requestedTemplateId
    ? getAiCoursewareTemplate(requestedTemplateId).id
    : DEFAULT_AI_COURSEWARE_TEMPLATE_ID
  const palette = buildPalette(normalized, options.paletteVariant || 0, templateId)
  const resolvedOptions = { ...options, templateId }
  const layoutOccurrences = new Map<string, number>()
  const slides = normalized.pages.map((page, index) => buildSlide(page, normalized, palette, resolvedOptions, index, layoutOccurrences))
  runPreflight(slides)
  return {
    title: normalized.title || normalized.chapterName || "音乐课件",
    theme: {
      themeColor: palette.primary,
      backgroundColor: palette.background,
      fontColor: palette.text,
      fontName: FONT_NAME,
      fontSize: "36px"
    },
    slides
  }
}

function buildSlide(page: AiCoursewarePage, outline: AiCoursewareOutline, palette: Palette, options: AiPptOptions, index: number, layoutOccurrences: Map<string, number>): Slide {
  const role = pageRole(page, index)
  const intent = pageRenderIntent(page, role)
  const master = getAiCoursewareTemplateMaster(options.templateId!)
  const baseMasterPage = getTemplateMasterPage(master, role, resolveAiPptLayout(page, index))
  const occurrence = layoutOccurrences.get(baseMasterPage.id) || 0
  layoutOccurrences.set(baseMasterPage.id, occurrence + 1)
  const adapted = adaptMasterPage(selectTemplateMasterPageVariant(baseMasterPage, occurrence), intent)
  const nativeVisual = isScorePage(page) || (role === "rhythm" && adapted.layout === "diagram")
  const designed = hasModelPageDesign(page) && !isScorePage(page)
  const headline = designed ? modelPageContent(page).heading : cleanText(page.interaction?.question) || activityTask(page) || studentHeadline(page)
  let masterPage = designed
    ? compilePageDesign(page, index, master, intent.showMedia, (externalVisual(page) && hasImage(page)) || Boolean(videoBinding(page)), Boolean(headline))
    : fitVisualSlots(adapted, hasImage(page) || Boolean(videoBinding(page)), nativeVisual)
  let contentElements = designed
    ? fillDesignedPage(master, masterPage, page, outline, palette, index, headline, intent)
    : fillTemplatePage(master, masterPage, page, outline, palette, role, intent)
  if (designed && aiPptTextGeometry(scaleElementsToViewport(contentElements)).length) {
    // 实际文字放不下时只重排一次：让图文并列，为正文让出宽度，保持分组和步骤语义。
    const retryPage = { ...page, visualPlan: { ...page.visualPlan!, visualShare: .35 } }
    const retryLayout = compilePageDesign(retryPage, index, master, intent.showMedia,
      (externalVisual(page) && hasImage(page)) || Boolean(videoBinding(page)), Boolean(headline), true)
    const retryElements = fillDesignedPage(master, retryLayout, retryPage, outline, palette, index, headline, intent)
    if (aiPptTextGeometry(scaleElementsToViewport(retryElements)).length < aiPptTextGeometry(scaleElementsToViewport(contentElements)).length) {
      masterPage = retryLayout
      contentElements = retryElements
    }
  }
  assertContentContract(master, masterPage, contentElements)
  const elements = [
    ...renderTemplateMasterElements(masterPage.base),
    ...contentElements,
    ...renderTemplateMasterElements(masterPage.chrome)
  ]
  return {
    id: nanoid(10),
    elements: scaleElementsToViewport(keepInCanvas(elements)),
    background: backgroundConfig(masterPage, options),
    remark: slideRemark(page),
    animations: options.enableAnimations ? entranceAnimations(contentElements) : undefined,
    turningMode: options.enableAnimations ? "fade" : "no"
  }
}

/** 传给图片生成器的真实模板槽位比例；媒体行存在时使用独立尺寸。 */
export function getAiPptImageAspectRatios(templateId: AiCoursewareTemplateId): Record<string, number> {
  const master = getAiCoursewareTemplateMaster(templateId)
  const layouts: Record<string, string> = { cover: "cover_scene", hero: "hero_focus", media: "media_focus", split: "split_content", text: "text_focus", diagram: "diagram_focus", compare: "compare", activity: "activity", summary: "summary", objectives: "objectives" }
  const ratios: Record<string, number> = {}
  for (const page of master.pages) {
    for (const showMedia of [true, false]) {
      const adapted = fitVisualSlots(adaptMasterPage(page, { role: page.roles[0], density: "medium", visualKind: "image", showMedia }), true, false)
      const slot = adapted.slots.find(slot => slot.kind === "image" && slot.enabled !== false)
      if (slot) ratios[layouts[page.layout] + (showMedia ? ":media" : "")] = slot.width / slot.height
    }
  }
  ratios.model_design_v1 = 1 // 服务端依据本版编译器的安全区域和模型比例计算图片尺寸。
  ratios.model_design_v2 = 1
  return ratios
}

function fillDesignedPage(master: TemplateMaster, layout: TemplateMasterPage, page: AiCoursewarePage, outline: AiCoursewareOutline, palette: Palette, index: number, headline: string, intent: PageRenderIntent): PPTElement[] {
  const elements: PPTElement[] = []
  const content = modelPageContent(page)
  const points = content.points
  addSlotText(elements, slotOf(layout, 'title'), page.title, master.titleColor, true)
  if (index === 0) addSlotText(elements, slotOf(layout, 'meta'), [outline.gradeName, conciseTextbook(outline.textbookName), outline.unitName].filter(Boolean).join(' · '), master.mutedColor)
  addSlotText(elements, slotOf(layout, 'headline'), headline, master.textColor, true)
  addSlotText(elements, layout.slots.find(slot => slot.id === 'instruction'), content.task, master.mutedColor)
  addVisualOrResource(elements, slotOf(layout, 'image'), page, master, palette)
  const composition = page.visualPlan!.composition
  const presentation = page.visualPlan!.textPresentation || 'plain'
  const paintText = (slot: TemplateSlot | undefined, values: string[]) => {
    if (slot?.textFlow === 'columns' && values.length) {
      const width = (slot.width - 28 * (values.length - 1)) / values.length
      for (let index = 0; index < values.length; index++) addSlotText(elements, { ...slot, left: slot.left + index * (width + 28), width,
        preferredFontSize: 38 }, values[index], master.textColor)
      return
    }
    if (slot) slot = compactTextSlot(slot, values, presentation)
    if (presentation === 'steps') addStepGrid(elements, slot, values, master, palette)
    else if (presentation === 'grid') addCardGrid(elements, slot, values, master, palette)
    else if (presentation === 'cards' && values.length === 4 && slot && slot.width >= 1000) addCardGrid(elements, slot, values, master, palette, 2)
    else addSlotList(elements, slot, values, master, palette, presentation === 'cards')
  }
  if (composition === 'comparison' && content.groups.length === 2) {
    content.groups.forEach((group, i) => {
      const slot = slotOf(layout, i === 0 ? 'left' : 'right')!
      if (group.label) addSlotText(elements, { ...slot, height: 52 }, group.label, master.titleColor, true)
      paintText(group.label ? { ...slot, top: slot.top + 66, height: slot.height - 66 } : slot, group.points)
    })
    paintText(slotOf(layout, 'body'), points)
  } else {
    const body = slotOf(layout, 'body')!
    const rows = page.visualPlan?.visualMode === 'native_diagram' ? rhythmRows(points) : []
    const pattern = page.visualPlan?.visualMode === 'native_diagram' && pageRole(page, index) === 'rhythm'
      ? [headline, ...points].join(' ').match(/[短长](?:\s*[-—·、]\s*[短长]){1,7}/)?.[0].match(/[短长]/g) : undefined
    if (!content.steps.length && rows.length && rows.length === points.length && body.height >= rows.length * 160) {
      addRhythmRows(elements, body, rows, master, palette)
    } else if (pattern && !content.steps.length) {
      addDurationDiagram(elements, { ...body, height: body.height * .55 }, pattern, master, palette)
      paintText({ ...body, top: body.top + body.height * .60, height: body.height * .40 }, points)
    } else paintText(body, [...content.steps, ...points])
  }
  addInlineMedia(elements, slotOf(layout, 'media'), page, master, palette, intent.showMedia)
  return elements
}

function compactTextSlot(slot: TemplateSlot, values: string[], presentation: string): TemplateSlot {
  const grid = presentation === 'grid' || presentation === 'steps'
  const height = Math.min(slot.height, aiPptBlockHeight(values, slot.width, presentation))
  return { ...slot, top: slot.top + (grid ? Math.min(100, (slot.height - height) / 2) : 0), height, preferredFontSize: Math.max(slot.preferredFontSize || 34, 38) }
}

function addRhythmRows(elements: PPTElement[], slot: TemplateSlot, rows: ReturnType<typeof rhythmRows>, master: TemplateMaster, palette: Palette) {
  const rowHeight = Math.min(220, (slot.height - 24 * (rows.length - 1)) / rows.length)
  rows.forEach((row, i) => {
    const top = slot.top + i * (rowHeight + 24)
    addSlotText(elements, { ...slot, top, height: 58, preferredFontSize: 38 }, row.source, master.textColor, true)
    const width = Math.min(160, (slot.width - 12 * (row.tokens.length - 1)) / row.tokens.length)
    row.tokens.forEach((token, j) => {
      const cell = { left: slot.left + j * (width + 12), top: top + 76, width, height: Math.max(48, rowHeight - 82) }
      if (!/[|｜]/.test(token)) elements.push(shapeElement({ ...cell, fill: palette.soft, radius: 10 }))
      addSlotText(elements, { ...slot, ...cell, preferredFontSize: 44 }, token, master.textColor, true)
    })
  })
}

function fillTemplatePage(master: TemplateMaster, masterPage: TemplateMasterPage, page: AiCoursewarePage, outline: AiCoursewareOutline, palette: Palette, role: PageRole = masterPage.roles[0], intent = pageRenderIntent(page, role)): PPTElement[] {
  master = {
    ...master,
    titleColor: masterPage.titleColor || master.titleColor,
    coverTitleColor: masterPage.coverTitleColor || master.coverTitleColor,
    textColor: masterPage.textColor || master.textColor,
    mutedColor: masterPage.mutedColor || master.mutedColor
  }
  const elements: PPTElement[] = []
  const title = masterPage.layout === "cover" ? chapterTitle(outline, page) : displayPageTitle(page, outline)
  // 学生可见内容必须与编辑区保持一致，不能因模板容量静默丢弃条目。
  const headline = cleanText(page.interaction?.question) || activityTask(page) || studentHeadline(page)
  const points = uniqueVisibleTexts([activityTask(page), ...studentPoints(page), ...(page.interaction?.options || [])])
    .filter(point => !sameVisibleText(point, headline))

  addSlotText(elements, slotOf(masterPage, "title"), title, masterPage.layout === "cover" ? master.coverTitleColor : master.titleColor, true)

  if (role !== "cover" && isScorePage(page)) {
    addNotationVisual(elements, slotOf(masterPage, "image"), page, master, palette)
    addSlotList(elements, slotOf(masterPage, "body"), uniqueVisibleTexts([headline, ...points, page.interaction?.question || "", ...(page.interaction?.options || [])]), master, palette, false)
    addInlineMedia(elements, slotOf(masterPage, "media"), page, master, palette, intent.showMedia)
    return elements
  }

  if (masterPage.layout === "cover") {
    const meta = [outline.gradeName, conciseTextbook(outline.textbookName), outline.unitName].filter(Boolean).join(" · ")
    const coverSecondaryColor = master.coverTitleColor.toUpperCase() === "#FFFFFF" ? "#DDE6F4" : master.mutedColor
    addSlotText(elements, slotOf(masterPage, "meta"), meta, coverSecondaryColor)
    addSlotList(elements, slotOf(masterPage, "headline"), uniqueVisibleTexts([headline, ...points]), master, palette, false, master.coverTitleColor)
    addVisualOrResource(elements, slotOf(masterPage, "image"), page, master, palette, !masterPage.backgroundVisual)
    return elements
  }

  if (masterPage.layout === "hero") {
    addVisualOrResource(elements, slotOf(masterPage, "image"), page, master, palette, !masterPage.backgroundVisual)
    const body = uniqueVisibleTexts([page.interaction?.question || "", headline, ...points])
    addSlotList(elements, slotOf(masterPage, "body"), body, master, palette)
    addInlineMedia(elements, slotOf(masterPage, "media"), page, master, palette, intent.showMedia)
    return elements
  }

  if (masterPage.layout === "objectives") {
    addVisualOrResource(elements, slotOf(masterPage, "image"), page, master, palette)
    addCardGrid(elements, slotOf(masterPage, "body"), uniqueVisibleTexts([headline, ...points]), master, palette)
    return elements
  }

  if (masterPage.layout === "media") {
    addSlotText(elements, slotOf(masterPage, "headline"), headline || page.interaction?.question || "带着问题听音乐", palette.primary, true)
    addVisualOrResource(elements, slotOf(masterPage, "image"), page, master, palette, !masterPage.backgroundVisual)
    addSlotList(elements, slotOf(masterPage, "body"), points, master, palette)
    addInlineMedia(elements, slotOf(masterPage, "media"), page, master, palette, intent.showMedia)
    return elements
  }

  if (masterPage.layout === "split") {
    addVisualOrResource(elements, slotOf(masterPage, "image"), page, master, palette, !masterPage.backgroundVisual)
    addSlotList(elements, slotOf(masterPage, "body"), uniqueVisibleTexts([headline, ...points]), master, palette)
    addInlineMedia(elements, slotOf(masterPage, "media"), page, master, palette, intent.showMedia)
    return elements
  }

  if (masterPage.layout === "text") {
    addVisualOrResource(elements, slotOf(masterPage, "image"), page, master, palette)
    addSlotText(elements, slotOf(masterPage, "headline"), headline || (role === "lyric" ? "读一读，再唱一唱" : "抓住这一页的关键信息"), page.interaction?.question ? master.textColor : palette.primary, true)
    if (role === "lyric") addLyricLines(elements, slotOf(masterPage, "body"), points, master, palette)
    else addSlotList(elements, slotOf(masterPage, "body"), points, master, palette, false)
    addInlineMedia(elements, slotOf(masterPage, "media"), page, master, palette, intent.showMedia)
    return elements
  }

  if (masterPage.layout === "diagram") {
    const rhythmPattern = role === "rhythm" ? [headline, ...points].join(" ").match(/[短长](?:\s*[-—·、]\s*[短长]){1,7}/)?.[0].match(/[短长]/g) : undefined
    if (role === "notation") addNotationVisual(elements, slotOf(masterPage, "image"), page, master, palette, false)
    else if (rhythmPattern) addDurationDiagram(elements, slotOf(masterPage, "image"), rhythmPattern, master, palette)
    else if (role === "rhythm") addStepGrid(elements, slotOf(masterPage, "image"), points, master, palette)
    else addVisualOrResource(elements, slotOf(masterPage, "image"), page, master, palette, true)
    if (role !== "rhythm" || rhythmPattern) addSlotList(elements, slotOf(masterPage, "body"), uniqueVisibleTexts([headline, ...points]), master, palette)
    else addSlotText(elements, slotOf(masterPage, "body"), headline, master.textColor)
    addInlineMedia(elements, slotOf(masterPage, "media"), page, master, palette, intent.showMedia)
    return elements
  }

  if (masterPage.layout === "compare") {
    addVisualOrResource(elements, slotOf(masterPage, "image"), page, master, palette)
    const values = uniqueVisibleTexts([...(page.interaction?.options || []), ...points])
    const midpoint = Math.max(1, Math.ceil(values.length / 2))
    addSlotText(elements, slotOf(masterPage, "headline"), headline || page.interaction?.question || "听一听，它们有什么不同？", palette.primary, true)
    addSlotList(elements, slotOf(masterPage, "left"), values.slice(0, midpoint), master, palette)
    addSlotList(elements, slotOf(masterPage, "right"), values.slice(midpoint), master, palette)
    addInlineMedia(elements, slotOf(masterPage, "media"), page, master, palette, intent.showMedia)
    return elements
  }

  if (masterPage.layout === "activity") {
    addVisualOrResource(elements, slotOf(masterPage, "image"), page, master, palette)
    addSlotText(elements, slotOf(masterPage, "headline"), headline || "一起完成音乐任务", palette.primary, true)
    addStepGrid(elements, slotOf(masterPage, "steps"), points, master, palette)
    addInlineMedia(elements, slotOf(masterPage, "media"), page, master, palette, intent.showMedia)
    return elements
  }

  addVisualOrResource(elements, slotOf(masterPage, "image"), page, master, palette)
  addChecklist(elements, slotOf(masterPage, "body"), points, master, palette)
  addSlotText(elements, slotOf(masterPage, "headline"), headline, palette.primary, true)
  return elements
}

function slotOf(page: TemplateMasterPage, id: string) {
  return page.slots.find(item => item.id === id && item.enabled !== false)
}

function pageRenderIntent(page: AiCoursewarePage, role: PageRole): PageRenderIntent {
  const densityValue = String(page.visualPlan?.visualDensity || "").toLowerCase()
  const pointCount = Math.max(page.studentContent?.points?.length || 0, page.bullets?.length || 0, page.activity?.steps?.length || 0)
  const density: PageRenderIntent["density"] = densityValue === "low" || densityValue === "high"
    ? densityValue
    : pointCount <= 2 ? "low" : pointCount >= 5 ? "high" : "medium"
  const hasBoundMedia = (page.resourceBindings || []).some(binding =>
    binding.verified !== false && ["SONG", "VIDEO"].includes(binding.resourceType) && Boolean(binding.contentUrl)
  )
  const expectsMedia = role === "listen" || (page.resourceBindings || []).some(binding =>
    ["SONG", "VIDEO"].includes(binding.resourceType) && binding.required === true
  )
  const visualKind: PageRenderIntent["visualKind"] = role === "notation"
    ? "notation"
    : role === "rhythm"
      ? "rhythm"
      : role === "compare"
        ? "compare"
        : ["activity", "performance"].includes(role)
          ? "activity"
          : ["goal", "summary", "homework", "practice", "lyric"].includes(role)
            ? "text"
            : "image"
  return { role, density, visualKind, showMedia: hasBoundMedia || expectsMedia }
}

export function resolveAiPptLayout(page: AiCoursewarePage, index: number): string {
  const role = pageRole(page, index)
  if (role === "cover") return "cover_scene"
  if (isScorePage(page)) return "diagram_focus"
  if (role === "practice") return "text_focus"
  const requested = resolveTemplatePageLayout(page.visualPlan?.layout || page.visual?.layout)
  // 历史大纲可能已被服务端统一改为 split，优先恢复教学页型；配图由槽位适配处理。
  if (role === "rhythm") return hasImage(page) ? "activity" : "diagram_focus"
  if (requested && requested !== "split" && requested !== "cover") return requested
  const layouts: Partial<Record<PageRole, string>> = {
    intro: "hero_focus", story: "hero_focus", goal: "objectives", knowledge: "objectives",
    listen: "media_focus", compare: "compare", activity: "activity", performance: "activity",
    summary: "summary", homework: "activity", practice: "text_focus", interaction: "text_focus", lyric: "text_focus"
  }
  return layouts[role] || "split_content"
}

function fitVisualSlots(page: TemplateMasterPage, hasVisual: boolean, nativeVisual: boolean): TemplateMasterPage {
  if (nativeVisual) return page
  const image = slotOf(page, "image")
  const body = slotOf(page, "body")
  if (!hasVisual) {
    if (!image || !body) return page
    // 只合并并排区域，不能跨过标题或侵入模板保留区域。
    if (Math.abs(image.top - body.top) > 40) return page
    const left = Math.min(image.left, body.left)
    const right = Math.max(image.left + image.width, body.left + body.width)
    return { ...page, slots: page.slots.filter(s => s.kind !== "image").map(s => s.id === body.id ? { ...s, left, width: right - left } : s) }
  }
  if (image) return page
  // 在既有安全内容区内给教学图片分配位置，保留对比、步骤、总结的语义结构。
  const content = page.slots.filter(s => s.enabled !== false && ["body", "steps", "left", "right"].includes(s.kind))
  if (!content.length) return page // 自带封面主视觉的母版保持原有背景契约。
  const left = Math.min(...content.map(s => s.left)), top = Math.min(...content.map(s => s.top))
  const width = Math.max(...content.map(s => s.left + s.width)) - left
  const height = Math.max(...content.map(s => s.top + s.height)) - top
  // 对比图片置于两栏上方，左右内容保持同等面积，避免暗示一侧更重要。
  if (content.length > 1) {
    const imageHeight = Math.min(...content.map(s => s.height)) * 0.42
    const imageWidth = Math.min(width, imageHeight * 2)
    return { ...page, slots: [...page.slots.map(s => content.some(c => c.id === s.id)
      ? { ...s, top: s.top + imageHeight + 20, height: s.height - imageHeight - 20 } : s),
      { id: "image", kind: "image", left: left + (width - imageWidth) / 2, top, width: imageWidth, height: imageHeight }] }
  }
  const imageWidth = width * 0.4
  return { ...page, slots: [...page.slots.map(s => s.id === content[0].id ? { ...s, left: left + imageWidth + 28, width: width - imageWidth - 28 } : s),
    { id: "image", kind: "image", left, top, width: imageWidth, height }] }
}

function adaptMasterPage(page: TemplateMasterPage, intent: PageRenderIntent): TemplateMasterPage {
  if (intent.showMedia) return page
  const media = page.slots.find(slot => slot.kind === "media" && slot.enabled !== false)
  if (!media) return page
  const availableBottom = media.top + media.height
  const expandable = new Set(["body", "image", "steps", "left", "right"])
  return {
    ...page,
    slots: page.slots
      .filter(slot => slot.kind !== "media")
      .map(slot => {
        if (!expandable.has(slot.kind) || slot.top + slot.height > media.top + 24) return { ...slot }
        return { ...slot, height: Math.max(slot.height, availableBottom - slot.top) }
      })
  }
}

function assertContentContract(master: TemplateMaster, page: TemplateMasterPage, elements: PPTElement[]) {
  if (!page.safeArea || !page.reservedZones) return
  type ElementBounds = { left: number; top: number; width: number; height: number }
  const boundedElements = elements.filter((element): element is PPTElement & ElementBounds =>
    "height" in element && typeof element.height === "number"
  )
  const overlaps = (left: ElementBounds, right: ElementBounds) =>
    left.left < right.left + right.width && left.left + left.width > right.left && left.top < right.top + right.height && left.top + left.height > right.top
  const outsideSafeArea = boundedElements.find(element =>
    element.left < page.safeArea!.left ||
    element.top < page.safeArea!.top ||
    element.left + element.width > page.safeArea!.left + page.safeArea!.width ||
    element.top + element.height > page.safeArea!.top + page.safeArea!.height
  )
  if (outsideSafeArea) throw new Error(`模板 ${master.id}/${page.id} 生成内容超出投屏安全区，请调整该页面内容槽。`)
  const collision = page.reservedZones.find(zone => boundedElements.some(element => overlaps(element, zone)))
  if (collision) throw new Error(`模板 ${master.id}/${page.id} 生成内容侵入“${collision.purpose}”保留区，请更换版式或缩减内容。`)
}

function addSlotText(elements: PPTElement[], slot: TemplateSlot | undefined, content: string, color: string, bold = false) {
  if (!slot || !cleanText(content)) return
  elements.push(textElement({
    left: slot.left,
    top: slot.top,
    width: slot.width,
    height: slot.height,
    content,
    fontSize: fitFont(content, slot.width, slot.height, slot.preferredFontSize || 30, slot.minimumFontSize || 22),
    minimumFontSize: slot.minimumFontSize,
    color,
    bold
  }))
}

function addSlotList(
  elements: PPTElement[],
  slot: TemplateSlot | undefined,
  sourceItems: string[],
  master: TemplateMaster,
  palette: Palette,
  cards = true,
  textColor = master.textColor
) {
  if (!slot) return
  const items = uniqueVisibleTexts(sourceItems.map(cleanText).filter(Boolean))
  if (!items.length) return
  const gap = collectionGap(slot.height, items.length, 16)
  const rowHeight = (slot.height - gap * (items.length - 1)) / items.length
  items.forEach((item, index) => {
    const top = slot.top + index * (rowHeight + gap)
    const inset = cards ? Math.min(34, Math.max(12, rowHeight * 0.22)) : 0
    const textTopInset = Math.min(6, Math.max(1, rowHeight * 0.08))
    const textHeight = Math.max(12, rowHeight - textTopInset * 2)
    const textWidth = Math.max(40, slot.width - (cards ? inset + 24 : 0))
    const minimumFontSize = adaptiveMinimumFont(slot, textHeight)
    if (cards) {
      addCardFrame(elements, slot.left, top, slot.width, rowHeight, index, master, palette)
    }
    elements.push(
      textElement({
        left: slot.left + inset,
        top: top + textTopInset,
        width: textWidth,
        height: textHeight,
        content: item,
        fontSize: fitFont(item, textWidth, textHeight, slot.preferredFontSize || 30, minimumFontSize),
        minimumFontSize,
        color: textColor,
        bold: index === 0 && items.length === 1
      })
    )
  })
}

function collectionGap(height: number, count: number, preferred: number) {
  if (count <= 1) return 0
  return Math.max(1, Math.min(preferred, height / Math.max(8, count * 8)))
}

function adaptiveMinimumFont(slot: TemplateSlot, availableHeight: number) {
  // 内容过多时交给质量门禁提示拆页，不能靠无限缩小正文隐藏问题。
  return Math.max(24, slot.minimumFontSize || 24)
}

function addCardFrame(elements: PPTElement[], left: number, top: number, width: number, height: number, index: number, master: TemplateMaster, palette: Palette) {
  const accent = index % 2 ? palette.secondary : palette.primary
  if (master.cardStyle === "ink") {
    elements.push(shapeElement({ left, top: top + height - 3, width, height: 3, fill: master.borderColor, opacity: 0.52 }))
    elements.push(shapeElement({ left, top: top + 12, width: 14, height: 14, fill: accent, radius: 7 }))
    return
  }
  if (master.cardStyle === "sticker") {
    const fills = [palette.warm, palette.soft, master.surfaceColor]
    elements.push(shapeElement({ left, top, width, height, fill: fills[index % fills.length], radius: 22, shadow: lightShadow() }))
    elements.push(shapeElement({ left: left + 12, top: top + 12, width: 38, height: 38, fill: accent, radius: 19 }))
    return
  }
  if (master.cardStyle === "bubble") {
    elements.push(shapeElement({ left, top, width, height, fill: index % 2 ? palette.soft : master.surfaceColor, radius: Math.min(28, height / 2), shadow: lightShadow() }))
    elements.push(shapeElement({ left: left + 14, top: top + height / 2 - 8, width: 16, height: 16, fill: accent, radius: 8 }))
    return
  }
  if (master.cardStyle === "grid") {
    elements.push(shapeElement({ left, top, width, height, fill: master.surfaceColor, radius: 4 }))
    elements.push(shapeElement({ left, top, width: 14, height: 14, fill: accent, radius: 0 }))
    elements.push(shapeElement({ left: left + width - 26, top: top + height - 10, width: 26, height: 10, fill: accent, opacity: 0.5 }))
    return
  }
  if (master.cardStyle === "cinematic") {
    elements.push(shapeElement({ left, top, width, height, fill: master.surfaceColor, radius: 6, shadow: lightShadow() }))
    elements.push(shapeElement({ left, top, width: 8, height, fill: accent }))
    return
  }
  elements.push(shapeElement({ left, top, width, height, fill: master.surfaceColor, radius: 14, shadow: lightShadow() }))
  elements.push(shapeElement({ left, top, width: 10, height, fill: accent }))
}

function addCardGrid(elements: PPTElement[], slot: TemplateSlot | undefined, sourceItems: string[], master: TemplateMaster, palette: Palette, preferredColumns?: number) {
  if (!slot) return
  const items = uniqueVisibleTexts(sourceItems.map(cleanText).filter(Boolean))
  if (!items.length) return
  const columns = items.length === 1 ? 1 : Math.max(1, Math.min(preferredColumns || 3, items.length, (slot.minimumFontSize || 0) >= 28 ? Math.floor(slot.width / 300) : 3))
  const rows = Math.ceil(items.length / columns)
  const gap = collectionGap(slot.height, rows, 22)
  const width = (slot.width - gap * (columns - 1)) / columns
  const height = (slot.height - gap * (rows - 1)) / rows
  items.forEach((item, index) => {
    const left = slot.left + (index % columns) * (width + gap)
    const top = slot.top + Math.floor(index / columns) * (height + gap)
    const inset = Math.min(34, Math.max(10, Math.min(width, height) * 0.1))
    const textWidth = Math.max(36, width - inset * 2)
    const textHeight = Math.max(12, height - inset * 2)
    const minimumFontSize = adaptiveMinimumFont(slot, textHeight)
    addCardFrame(elements, left, top, width, height, index, master, palette)
    elements.push(
      textElement({
        left: left + inset,
        top: top + inset,
        width: textWidth,
        height: textHeight,
        content: item,
        fontSize: fitFont(item, textWidth, textHeight, slot.preferredFontSize || 32, minimumFontSize),
        minimumFontSize,
        color: master.textColor,
        bold: true
      })
    )
  })
}

function addLyricLines(elements: PPTElement[], slot: TemplateSlot | undefined, sourceItems: string[], master: TemplateMaster, palette: Palette) {
  if (!slot) return
  const items = uniqueVisibleTexts(sourceItems.map(cleanText).filter(Boolean))
  const gap = collectionGap(slot.height, items.length, 12)
  const height = (slot.height - gap * Math.max(0, items.length - 1)) / Math.max(1, items.length)
  items.forEach((item, index) => {
    const top = slot.top + index * (height + gap)
    const inset = Math.min(8, Math.max(1, height * 0.08))
    const textHeight = Math.max(12, height - inset * 2)
    const minimumFontSize = adaptiveMinimumFont(slot, textHeight)
    if (index % 2 === 0)
      elements.push(shapeElement({ left: slot.left, top, width: slot.width, height, fill: palette.soft, opacity: 0.55, radius: 18 }))
    elements.push(
      textElement({
        left: slot.left + 45,
        top: top + inset,
        width: slot.width - 90,
        height: textHeight,
        content: `♪  ${item}`,
        fontSize: fitFont(item, slot.width - 90, textHeight, slot.preferredFontSize || 38, minimumFontSize),
        minimumFontSize,
        color: master.textColor,
        bold: index === 0
      })
    )
  })
}

function addNotationVisual(elements: PPTElement[], slot: TemplateSlot | undefined, page: AiCoursewarePage, master: TemplateMaster, palette: Palette, backgroundVisual = false) {
  if (!slot) return
  const binding = scoreBinding(page)
  if (!binding) return // 缺谱在教师质量面板中提示，绝不绘制虚构谱例。
  if (usableResourceUrl(binding.scoreImageUrl)) {
    // 保持整张曲谱，不使用 cover 裁切，防止丢失谱号、小节或歌词。
    elements.push({ id: nanoid(10), type: "image", src: binding.scoreImageUrl!, left: slot.left, top: slot.top,
      width: slot.width, height: slot.height, fixedRatio: true, rotate: 0 } as PPTImageElement)
  } else {
    elements.push({ id: nanoid(10), type: "elf", subtype: "elf-sing-play", sid: binding.resourceId,
      title: binding.name || page.title, left: slot.left, top: slot.top, width: slot.width, height: slot.height, rotate: 0 } as PPTCloudCoachElement)
  }
}

function addDurationDiagram(elements: PPTElement[], slot: TemplateSlot | undefined, pattern: string[], master: TemplateMaster, palette: Palette) {
  if (!slot) return
  // 只可视化正文明确给出的长短顺序，不猜拍号、音符时值或教材谱例。
  const gap = 24, unit = (slot.width - gap * (pattern.length - 1)) / pattern.reduce((sum, item) => sum + (item === "长" ? 2 : 1), 0)
  let left = slot.left
  const barHeight = Math.min(80, slot.height * 0.22), top = slot.top + slot.height * 0.36
  pattern.forEach(item => {
    const width = unit * (item === "长" ? 2 : 1)
    elements.push(shapeElement({ left, top, width, height: barHeight, fill: item === "长" ? palette.secondary : palette.primary, radius: 12 }))
    addSlotText(elements, { id: "duration-label", kind: "body", left, top: top + barHeight + 22, width, height: 70, preferredFontSize: 40, minimumFontSize: 24 }, item, master.textColor, true)
    left += width + gap
  })
}

function addStepGrid(elements: PPTElement[], slot: TemplateSlot | undefined, sourceItems: string[], master: TemplateMaster, palette: Palette) {
  if (!slot) return
  const items = uniqueVisibleTexts(sourceItems.map(cleanText).filter(Boolean))
  if (!items.length) return
  const columns = Math.max(1, Math.min(4, items.length, (slot.minimumFontSize || 0) >= 28 ? Math.floor(slot.width / 300) : 4))
  const rows = Math.ceil(items.length / columns)
  const gap = collectionGap(slot.height, rows, 22)
  const width = (slot.width - gap * (columns - 1)) / columns
  const height = (slot.height - gap * (rows - 1)) / rows
  items.forEach((item, index) => {
    const left = slot.left + (index % columns) * (width + gap)
    const top = slot.top + Math.floor(index / columns) * (height + gap)
    const badgeSize = Math.min(72, Math.max((slot.minimumFontSize || 0) >= 28 ? 52 : 24, height * 0.2))
    const cardTop = top + badgeSize * 0.55
    const cardHeight = Math.max(12, height - badgeSize * 0.55)
    const textInset = Math.min(30, Math.max(8, width * 0.08))
    const textTop = cardTop + Math.min(70, Math.max(18, cardHeight * 0.22))
    const textHeight = Math.max(12, top + height - textTop - 8)
    const minimumFontSize = adaptiveMinimumFont(slot, textHeight)
    addCardFrame(elements, left, cardTop, width, cardHeight, index, master, palette)
    elements.push(
      shapeElement({
        left: left + textInset,
        top,
        width: badgeSize,
        height: badgeSize,
        fill: index % 2 ? palette.secondary : palette.primary,
        radius: badgeSize / 2
      })
    )
    elements.push(
      textElement({
        left: left + textInset,
        top,
        width: badgeSize,
        height: badgeSize,
        content: String(index + 1),
        fontSize: Math.min(28, Math.max(14, badgeSize * 0.4)),
        minimumFontSize: 12,
        color: "#FFFFFF",
        bold: true
      })
    )
    elements.push(
      textElement({
        left: left + textInset,
        top: textTop,
        width: Math.max(36, width - textInset * 2),
        height: textHeight,
        content: item,
        fontSize: fitFont(item, width - textInset * 2, textHeight, (slot.minimumFontSize || 0) >= 28 ? 40 : 29, minimumFontSize),
        minimumFontSize,
        color: master.textColor,
        bold: true
      })
    )
  })
}

function addChecklist(elements: PPTElement[], slot: TemplateSlot | undefined, sourceItems: string[], master: TemplateMaster, palette: Palette) {
  if (!slot) return
  const items = uniqueVisibleTexts(sourceItems.map(cleanText).filter(Boolean))
  const gap = collectionGap(slot.height, items.length, 16)
  const height = (slot.height - gap * Math.max(0, items.length - 1)) / Math.max(1, items.length)
  items.forEach((item, index) => {
    const top = slot.top + index * (height + gap)
    const iconSize = Math.min(42, Math.max(16, height * 0.58))
    const iconTop = top + Math.max(0, (height - iconSize) / 2)
    const textLeft = slot.left + iconSize + Math.min(30, Math.max(8, iconSize * 0.7))
    const textWidth = Math.max(40, slot.left + slot.width - textLeft)
    const minimumFontSize = adaptiveMinimumFont(slot, height)
    elements.push(
      shapeElement({
        left: slot.left,
        top: iconTop,
        width: iconSize,
        height: iconSize,
        fill: index % 2 ? palette.secondary : palette.primary,
        radius: iconSize / 2
      })
    )
    elements.push(
      textElement({
        left: slot.left + iconSize * 0.2,
        top: iconTop + iconSize * 0.12,
        width: iconSize * 0.6,
        height: iconSize * 0.7,
        content: "✓",
        fontSize: Math.min(24, Math.max(10, iconSize * 0.55)),
        minimumFontSize: 10,
        color: "#FFFFFF",
        bold: true
      })
    )
    elements.push(
      textElement({
        left: textLeft,
        top,
        width: textWidth,
        height,
        content: item,
        fontSize: fitFont(item, textWidth, height, slot.preferredFontSize || 32, minimumFontSize),
        minimumFontSize,
        color: master.textColor,
        bold: index === 0
      })
    )
  })
}

function addVisualOrResource(elements: PPTElement[], slot: TemplateSlot | undefined, page: AiCoursewarePage, master: TemplateMaster, palette: Palette, allowPlaceholder = true) {
  if (!slot) return
  const dedicated = (page.resourceBindings || []).find(item => item.verified !== false && item.dedicatedPage)
  if (dedicated?.resourceType === "MUSIC") {
    elements.push({ id: nanoid(10), type: "elf", subtype: "elf-sing-play", sid: dedicated.resourceId, title: dedicated.name || page.title, left: slot.left, top: slot.top, width: slot.width, height: slot.height, rotate: 0 } as PPTCloudCoachElement)
    return
  }
  const video = videoBinding(page)
  if (video) {
    elements.push({ id: nanoid(10), type: "elf", subtype: "elf-video", left: slot.left, top: slot.top, width: slot.width, height: slot.height, rotate: 0, src: video.contentUrl || "", poster: video.coverUrl, autoplay: false } as PPTVideoElement)
    return
  }
  if (hasImage(page)) {
    elements.push(imageElement(page, { left: slot.left, top: slot.top, width: slot.width, height: slot.height, radius: 18 }))
    return
  }
  // 无教学图片时留给文字排版；通用装饰不能充当观察对象。
}

function addSemanticVisual(elements: PPTElement[], slot: TemplateSlot, page: AiCoursewarePage, master: TemplateMaster, palette: Palette) {
  elements.push(shapeElement({ left: slot.left, top: slot.top, width: slot.width, height: slot.height, fill: master.surfaceColor, opacity: 0.86, radius: 18, shadow: lightShadow() }))
  const landscapeTop = slot.top + slot.height * 0.48
  elements.push(shapeElement({ left: slot.left + slot.width * 0.08, top: landscapeTop, width: slot.width * 0.84, height: slot.height * 0.35, fill: palette.soft, opacity: 0.9, radius: 28 }))
  elements.push(shapeElement({ left: slot.left + slot.width * 0.68, top: slot.top + slot.height * 0.12, width: Math.min(84, slot.width * 0.16), height: Math.min(84, slot.width * 0.16), fill: palette.warm, opacity: 0.85, radius: 42 }))
  elements.push(shapeElement({ left: slot.left + slot.width * 0.12, top: landscapeTop + slot.height * 0.12, width: slot.width * 0.46, height: slot.height * 0.2, fill: palette.secondary, opacity: 0.55, radius: 40 }))
  elements.push(shapeElement({ left: slot.left + slot.width * 0.42, top: landscapeTop + slot.height * 0.08, width: slot.width * 0.42, height: slot.height * 0.24, fill: palette.primary, opacity: 0.45, radius: 44 }))
  const requestedCue = cleanText(page.visualPlan?.focalContent || page.visualPlan?.mainVisual || page.visual?.mainVisual || page.imageKeywords?.[0])
  const cue = !requestedCue || sameVisibleText(requestedCue, page.title)
    ? `画面线索：${cleanText(page.title) || "观察音乐变化"}`
    : requestedCue
  elements.push(textElement({
    left: slot.left + slot.width * 0.1,
    top: slot.top + slot.height * 0.13,
    width: slot.width * 0.54,
    height: slot.height * 0.25,
    content: cue,
    fontSize: fitFont(cue, slot.width * 0.54, slot.height * 0.25, 30, 22),
    minimumFontSize: 22,
    color: master.titleColor,
    bold: true
  }))
}

function addInlineMedia(elements: PPTElement[], slot: TemplateSlot | undefined, page: AiCoursewarePage, master: TemplateMaster, palette: Palette, showMedia: boolean) {
  if (!slot || !showMedia) return
  const bindings = audioBindings(page)
  const width = slot.width / Math.max(1, bindings.length)
  bindings.forEach((binding, index) => {
    elements.push({ id: nanoid(10), type: "elf", subtype: "elf-audio", left: slot.left + index * width,
      top: slot.top + (slot.height - 60) / 2, width: 60, height: 60, rotate: 0, fixedRatio: true,
      color: palette.primary, autoplay: false, loop: false, src: binding.contentUrl! } as PPTAudioElement)
    addSlotText(elements, { ...slot, left: slot.left + index * width + 76, width: width - 92 },
      `${bindings.length > 1 ? String.fromCharCode(65 + index) + " · " : ""}${binding.name || "课堂音频"}`, master.textColor)
  })
}

function renderTemplateMasterElements(elements: TemplateMasterElement[]): PPTElement[] {
  return elements.map(element =>
    element.type === "text"
      ? textElement({
          left: element.left,
          top: element.top,
          width: element.width,
          height: element.height,
          content: element.content || "",
          fontSize: element.fontSize || 14,
          color: element.color || "#20313A",
          bold: element.bold
        })
      : shapeElement({
          left: element.left,
          top: element.top,
          width: element.width,
          height: element.height,
          fill: element.fill || "#FFFFFF",
          opacity: element.opacity,
          radius: element.radius
        })
  )
}

function entranceAnimations(elements: PPTElement[]): PPTAnimation[] {
  return elements
    .filter(
       element => element.type === "text" && element.width >= 120 && element.height >= 45
    )
    .slice(0, 6)
    .map((element, index) => ({
      id: nanoid(10),
      elId: element.id,
      effect: index === 0 ? "fadeIn" : "fadeInUp",
      type: "in",
      duration: 500,
       trigger: index === 0 ? "auto" : "click"
    }))
}

function videoBinding(page: AiCoursewarePage) {
  return (page.resourceBindings || []).find(item => item.verified === true && item.resourceType === "VIDEO" && usableResourceUrl(item.contentUrl))
}

function normalizeOutline(outline: AiCoursewareOutline): AiCoursewareOutline {
  const chapter = cleanText(outline.chapterName || outline.title || "音乐课件")
  return {
    ...outline,
    title: GENERIC_PAGE_TITLES.has(cleanText(outline.title).toLowerCase()) ? chapter : cleanText(outline.title || chapter),
    pages: (outline.pages || []).map((page, index) => ({
      ...page,
      pageNo: index + 1,
      title: index === 0 && GENERIC_PAGE_TITLES.has(cleanText(page.title).toLowerCase()) ? chapter : cleanText(page.title || chapter),
      bullets: (page.bullets || []).map(cleanText).filter(Boolean),
      imageKeywords: (page.imageKeywords || []).map(cleanText).filter(Boolean)
    }))
  }
}

function pageRole(page: AiCoursewarePage, index: number): PageRole {
  if (index === 0) return "cover"
  const kind = `${page.type || ""} ${page.visualPlan?.layout || ""} ${page.visual?.layout || ""}`.toLowerCase()
  if (kind.includes("objective") || kind.includes("goal")) return "goal"
  if (kind.includes("practice_check") || kind.includes("assessment")) return "practice"
  if (kind.includes("compare")) return "compare"
  if (kind.includes("instrument")) return "instrument"
  if (kind.includes("melody") || kind.includes("score") || kind.includes("notation")) return "notation"
  if (kind.includes("performance") || kind.includes("expressive") || kind.includes("creative")) return "performance"
  if (kind.includes("listen")) return "listen"
  if (kind.includes("lyric") || kind.includes("phrase_sing") || kind.includes("sing_focus")) return "lyric"
  if (kind.includes("rhythm") || kind.includes("skill")) return "rhythm"
  if (kind.includes("knowledge")) return "knowledge"
  if (kind.includes("interaction")) return "interaction"
  if (kind.includes("activity")) return "activity"
  if (kind.includes("summary")) return "summary"
  if (kind.includes("homework") || kind.includes("extension")) return "homework"
  if (kind.includes("intro") || kind.includes("scene")) return "intro"
  if (kind.includes("context") || kind.includes("background") || kind.includes("story")) return "story"
  return "content"
}

function displayPageTitle(page: AiCoursewarePage, outline: AiCoursewareOutline) {
  const title = cleanText(page.title)
  return !title || GENERIC_PAGE_TITLES.has(title.toLowerCase()) ? chapterTitle(outline, page) : title
}

function chapterTitle(outline: AiCoursewareOutline, page: AiCoursewarePage) {
  return cleanText(page.title || outline.title || outline.chapterName || "音乐课件")
}

function conciseTextbook(value?: string) {
  return cleanText(value).replace(/^.*?·/, "")
}

function hasImage(page: AiCoursewarePage) {
  return Boolean(page.image?.url)
}

function studentHeadline(page: AiCoursewarePage) {
  const headline = cleanText(page.studentContent?.headline || page.subtitle || "")
  return sameVisibleText(headline, page.title) || isTeacherFacingText(headline) ? "" : headline
}

function studentPoints(page: AiCoursewarePage) {
  const structured = (page.studentContent?.points || []).map(cleanText).filter(Boolean)
  const legacy = (page.bullets || []).map(cleanText).filter(Boolean)
  const points = [...(structured.length ? structured : legacy), studentHeadline(page)].filter(Boolean)
  const excluded = [page.title].map(normalizeVisibleText).filter(Boolean)
  return uniqueVisibleTexts(points).filter(item => !excluded.includes(normalizeVisibleText(item)) && !isTeacherFacingText(item))
}

function activityTask(page: AiCoursewarePage) {
  // activity 属于教师组织信息，不能回退到学生投屏画面。
  const task = cleanText(page.classroomAction?.studentTask || studentHeadline(page) || "")
  return sameVisibleText(task, page.title) || isTeacherFacingText(task) ? "" : task
}

function slideRemark(page: AiCoursewarePage) {
  const lessonMeta = page.teachingStage || ""
  const evidence = page.learningEvidence ? `学习表现：${page.learningEvidence}` : ""
  const activity = [page.activity?.task, ...(page.activity?.steps || [])].map(cleanText).filter(Boolean).join("\n")
  const fallbackInstruction = cleanText(page.classroomAction?.teacherInstruction || page.teacherTips || page.speakerNotes)
    || `引导学生完成“${activityTask(page) || page.title}”，观察学生是否能用语言、动作或声音表达本页学习结果。`
  const answer = page.interaction?.answer ? `参考答案：${page.interaction.answer}` : ""
  const explanation = page.interaction?.explanation ? `解析：${page.interaction.explanation}` : ""
  const resources = (page.resourceBindings || []).map(item => `${item.name || item.resourceType}：${item.purpose || "课堂资源"}`).join("\n")
  const mediaReminder = /listen|sing/.test(page.type) && audioBindings(page).length === 0 ? "资源准备：请为本页听唱任务补充对应音频。" : ""
  return [lessonMeta, page.teachingPurpose, ...teacherFacingTexts(page), activity, fallbackInstruction, page.speakerNotes, page.teacherTips, evidence, answer, explanation, resources, mediaReminder, page.imageReview]
    .map(cleanText)
    .filter(Boolean)
    .filter((item, index, all) => all.indexOf(item) === index)
    .join("\n")
}

function buildPalette(outline: AiCoursewareOutline, variant: number, templateId?: AiCoursewareTemplateId): Palette {
  const resolvedTemplateId = templateId || DEFAULT_AI_COURSEWARE_TEMPLATE_ID
  return { ...getAiCoursewarePalette(resolvedTemplateId, variant), ...(resolvedTemplateId === "dark-lute" ? { soft: "#16485C" } : {}) }
}

function backgroundConfig(masterPage: TemplateMasterPage, options: AiPptOptions): SlideBackground {
  if (options.backgroundImage) return { type: "image", image: options.backgroundImage, imageSize: "cover" }
  if (masterPage.backgroundImage) return { type: "image", image: masterPage.backgroundImage, imageSize: "cover" }
  return { type: "solid", color: masterPage.background }
}

function fitFont(content: string, width: number, height: number, preferred: number, minimum: number) {
  const text = cleanText(content)
  if (!text) return preferred
  let size = preferred
  while (size > minimum) {
    const estimated = minimum >= 28 ? measureAiPptText(text, width, size)
      : Math.ceil(text.length / Math.max(1, Math.floor(width / size))) * size * 1.35
    if (estimated <= height) break
    size = Math.max(minimum, size - 2)
  }
  return size
}

function textElement(params: {
  left: number
  top: number
  width: number
  height: number
  content: string
  fontSize: number
  minimumFontSize?: number
  color: string
  bold?: boolean
  lineHeight?: number
}): PPTTextElement {
  const lineHeight = params.lineHeight || 1.25
  const minimum = Math.min(params.fontSize, params.minimumFontSize ?? (params.fontSize >= 30 ? 22 : 18))
  const resolvedFontSize = fitFont(params.content, params.width, params.height, params.fontSize, minimum)
  return {
    id: nanoid(10),
    type: "text",
    left: params.left,
    top: params.top,
    width: params.width,
    height: params.height,
    rotate: 0,
    // 永远保留完整文本。若最小字号仍放不下，由质量门禁阻止应用，而不是静默截断。
    content: `<div style="box-sizing:border-box;width:calc(100% - 20px);font-family:${FONT_NAME};font-size:${resolvedFontSize}px;${params.bold ? "font-weight:700;" : ""}">${escapeHtml(cleanText(params.content))}</div>`,
    defaultFontName: FONT_NAME,
    defaultColor: params.color,
    lineHeight,
    paragraphSpace: 0,
    wordSpace: 0,
    opacity: 1
  }
}

function imageElement(page: AiCoursewarePage, rect: ImageRect): PPTImageElement {
  const width = page.image?.width || 0
  const height = page.image?.height || 0
  const contain = page.requiredVisual || page.visualPlan?.imagePurpose !== "decoration" || page.visualPlan?.imageFit !== "cover"
  const scale = width > 0 && height > 0 ? Math.min(rect.width / width, rect.height / height) : 0
  const fittedWidth = contain && scale ? width * scale : rect.width
  const fittedHeight = contain && scale ? height * scale : rect.height
  return {
    id: nanoid(10),
    type: "image",
    left: rect.left + (rect.width - fittedWidth) / 2,
    top: rect.top + (rect.height - fittedHeight) / 2,
    width: fittedWidth,
    height: fittedHeight,
    rotate: 0,
    src: page.image?.url || "",
    fixedRatio: Boolean(contain),
    radius: rect.radius || 0,
    shadow: rect.radius ? softShadow() : undefined,
    clip: !contain && width > 0 && height > 0 ? { shape: "rect", range: coverRange(width, height, rect.width, rect.height) } : undefined
  }
}

function coverRange(sourceWidth: number, sourceHeight: number, targetWidth: number, targetHeight: number): [[number, number], [number, number]] {
  const sourceRatio = sourceWidth / sourceHeight
  const targetRatio = targetWidth / targetHeight
  if (sourceRatio > targetRatio) {
    const visible = (targetRatio / sourceRatio) * 100
    const start = (100 - visible) / 2
    return [
      [start, 0],
      [100 - start, 100]
    ]
  }
  const visible = (sourceRatio / targetRatio) * 100
  const start = (100 - visible) / 2
  return [
    [0, start],
    [100, 100 - start]
  ]
}

function shapeElement(params: {
  left: number
  top: number
  width: number
  height: number
  fill: string
  opacity?: number
  radius?: number
  shadow?: PPTElementShadow
  gradient?: Gradient
  text?: PPTShapeElement["text"]
}): PPTShapeElement {
  return {
    id: nanoid(10),
    type: "shape",
    left: params.left,
    top: params.top,
    width: params.width,
    height: params.height,
    rotate: 0,
    viewBox: [200, 200],
    path: roundedRectPath(params.radius || 0),
    fixedRatio: false,
    fill: params.fill,
    opacity: params.opacity ?? 1,
    shadow: params.shadow,
    gradient: params.gradient,
    text: params.text
  }
}

function lineElement(x1: number, y1: number, x2: number, y2: number, color: string, width = 2): PPTLineElement {
  const left = Math.min(x1, x2)
  const top = Math.min(y1, y2)
  const lineWidth = Math.abs(x2 - x1)
  const lineHeight = Math.abs(y2 - y1)
  return {
    id: nanoid(10),
    type: "line",
    left,
    top,
    width,
    start: [x1 === left ? 0 : lineWidth, y1 === top ? 0 : lineHeight],
    end: [x2 === left ? 0 : lineWidth, y2 === top ? 0 : lineHeight],
    style: "solid",
    color,
    points: ["", ""]
  }
}

function keepInCanvas(elements: PPTElement[]) {
  return elements.map(element => {
    const left = Math.max(0, Math.min(element.left, SLIDE_WIDTH - 1))
    const top = Math.max(0, Math.min(element.top, SLIDE_HEIGHT - 1))
    if (element.type === "line") return { ...element, left, top, width: Math.max(1, Math.min(element.width, 20)) }
    return {
      ...element,
      left,
      top,
      width: Math.max(1, Math.min(element.width, SLIDE_WIDTH - left)),
      height: Math.max(1, Math.min(element.height, SLIDE_HEIGHT - top))
    }
  }) as PPTElement[]
}

function scaleElementsToViewport(elements: PPTElement[]): PPTElement[] {
  return elements.map(element => {
    if (element.type === "line") {
      return {
        ...element,
        left: element.left * VIEWPORT_SCALE,
        top: element.top * VIEWPORT_SCALE,
        width: element.width * VIEWPORT_SCALE,
        start: [element.start[0] * VIEWPORT_SCALE, element.start[1] * VIEWPORT_SCALE],
        end: [element.end[0] * VIEWPORT_SCALE, element.end[1] * VIEWPORT_SCALE]
      }
    }

    const scaled = {
      ...element,
      left: element.left * VIEWPORT_SCALE,
      top: element.top * VIEWPORT_SCALE,
      width: element.width * VIEWPORT_SCALE,
      height: element.height * VIEWPORT_SCALE
    } as PPTElement
    if (scaled.type === "text") {
      scaled.content = scaleInlineFontSizes(scaled.content)
    }
    if (scaled.type === "shape" && scaled.text) {
      scaled.text = { ...scaled.text, content: scaleInlineFontSizes(scaled.text.content) }
    }
    if ("radius" in scaled && typeof scaled.radius === "number") {
      scaled.radius *= VIEWPORT_SCALE
    }
    if ("shadow" in scaled && scaled.shadow) {
      scaled.shadow = {
        ...scaled.shadow,
        h: scaled.shadow.h * VIEWPORT_SCALE,
        v: scaled.shadow.v * VIEWPORT_SCALE,
        blur: scaled.shadow.blur * VIEWPORT_SCALE
      }
    }
    return scaled
  })
}

function scaleInlineFontSizes(content: string) {
  return content.replace(/font-size:\s*([\d.]+)px/g, (_match, size) => `font-size:${Number(size) * VIEWPORT_SCALE}px`)
}

function runPreflight(slides: Slide[]) {
  slides.forEach((slide, index) => {
    const invalid = slide.elements.filter(
      element =>
        element.left < 0 ||
        element.top < 0 ||
        element.left + element.width > VIEWPORT_WIDTH + 1 ||
        (element.type !== "line" && element.top + element.height > VIEWPORT_HEIGHT + 1)
    )
    const emptyText = slide.elements.filter(element => element.type === "text" && !stripHtml(element.content))
    if (invalid.length || emptyText.length)
      console.warn("AI PPT preflight issue", { pageNo: index + 1, invalid: invalid.length, emptyText: emptyText.length })
  })
}

function roundedRectPath(radius: number) {
  const r = Math.max(0, Math.min(radius, 100))
  return `M ${r} 0 L ${200 - r} 0 Q 200 0 200 ${r} L 200 ${200 - r} Q 200 200 ${200 - r} 200 L ${r} 200 Q 0 200 0 ${200 - r} L 0 ${r} Q 0 0 ${r} 0 Z`
}

function softShadow(): PPTElementShadow {
  return { h: 0, v: 8, blur: 22, color: "rgba(23, 34, 46, 0.14)" }
}

function lightShadow(): PPTElementShadow {
  return { h: 0, v: 4, blur: 14, color: "rgba(23, 34, 46, 0.1)" }
}

function cleanText(value?: string) {
  return String(value || "")
    .replace(/\s+/g, " ")
    .trim()
}

function escapeHtml(value: string) {
  return cleanText(value).replace(/&/g, "&amp;").replace(/</g, "&lt;").replace(/>/g, "&gt;")
}

function stripHtml(value: string) {
  return value.replace(/<[^>]+>/g, "").trim()
}

function normalizeVisibleText(value?: string) {
  return cleanText(value)
    .replace(/[，。！？、；：,.!?;:\s]+/g, "")
    .toLowerCase()
}

function sameVisibleText(left?: string, right?: string) {
  const normalizedLeft = normalizeVisibleText(left)
  return Boolean(normalizedLeft) && normalizedLeft === normalizeVisibleText(right)
}

function uniqueVisibleTexts(values: string[]) {
  const seen = new Set<string>()
  return values.filter(value => {
    const key = normalizeVisibleText(value)
    if (!key || seen.has(key)) return false
    seen.add(key)
    return true
  })
}