<template>
  <div class="chapter-view" v-if="chapter">
    <header class="chapter-header">
      <div class="chapter-icon">{{ chapter.icon }}</div>
      <div>
        <h1 class="chapter-title">{{ chapter.title }}</h1>
        <p class="chapter-subtitle">{{ chapter.subtitle }}</p>
        <p class="chapter-desc">{{ chapter.description }}</p>
      </div>
    </header>

    <section class="topics-section">
      <h2 class="section-label">📌 本章知识点</h2>
      <div class="topics-list">
        <span v-for="topic in chapter.topics" :key="topic" class="topic-pill">
          {{ topic }}
        </span>
      </div>
    </section>

    <!-- 子文件夹分组显示 -->
    <section v-for="folder in chapter.subfolders" :key="folder.name" class="folder-section">
      <h2 class="folder-title">📂 {{ folder.label }}</h2>
      <p class="folder-hint" v-if="getFolderDescription(folder.name)">{{ getFolderDescription(folder.name) }}</p>
      <!-- 动态演示入口 -->
      <div v-if="folder.demo" class="demo-entry">
        <router-link :to="folder.demo.path" class="demo-link">
          <span class="demo-link-icon">{{ folder.demo.label.split(' ')[0] }}</span>
          <span class="demo-link-text">{{ folder.demo.label }}</span>
          <span class="demo-link-desc">{{ folder.demo.description }}</span>
          <span class="demo-link-arrow">→</span>
        </router-link>
      </div>
      <div class="file-list">
        <div
          v-for="file in folder.files"
          :key="file.path"
          class="file-item"
          :class="{ active: currentFile?.path === file.path }"
          @click="selectFile(file)"
        >
          <div class="file-item-header">
            <span class="file-item-icon">📄</span>
            <span class="file-item-name">{{ file.name }}</span>
            <span class="file-item-label">{{ file.label }}</span>
          </div>
          <p class="file-item-desc">{{ file.description }}</p>
        </div>
      </div>
    </section>

    <!-- 根级文件（没有子文件夹的文件） -->
    <section v-if="chapter.files && chapter.files.length" class="folder-section">
      <h2 class="folder-title">📂 其他示例</h2>
      <div class="file-list">
        <div
          v-for="file in chapter.files"
          :key="file.path"
          class="file-item"
          :class="{ active: currentFile?.path === file.path }"
          @click="selectFile(file)"
        >
          <div class="file-item-header">
            <span class="file-item-icon">📄</span>
            <span class="file-item-name">{{ file.name }}</span>
            <span class="file-item-label">{{ file.label }}</span>
          </div>
          <p class="file-item-desc">{{ file.description }}</p>
        </div>
      </div>
    </section>

    <!-- 代码查看 Drawer -->
    <Teleport to="body">
      <Transition name="drawer">
        <div v-if="currentFile" class="drawer-overlay" @click.self="closeDrawer">
          <div class="drawer-panel">
            <div class="drawer-header">
              <span class="drawer-title">💻 代码查看</span>
              <div class="drawer-lang-tabs">
                <button
                  class="lang-tab"
                  :class="{ active: language === 'c' }"
                  @click="switchLanguage('c')"
                >C</button>
                <button
                  class="lang-tab"
                  :class="{ active: language === 'python' }"
                  @click="switchLanguage('python')"
                >Python</button>
              </div>
              <button class="drawer-close-btn" @click="closeDrawer">✕</button>
            </div>
            <div class="drawer-body">
              <CodeViewer
                :key="currentFilePath"
                :filePath="currentFilePath"
                :fileName="currentFileName"
                :fileLabel="currentFile.label"
                :description="currentFile.description"
                :language="language"
              />
            </div>
          </div>
        </div>
      </Transition>
    </Teleport>
  </div>

  <div v-else class="not-found">
    <h2>章节未找到</h2>
    <p>请返回首页重新选择。</p>
    <router-link to="/" class="back-link">← 返回首页</router-link>
  </div>
</template>

<script setup>
import { ref, computed, watch } from 'vue'
import { useRoute } from 'vue-router'
import { getChapterById } from '../data/chapters.js'
import CodeViewer from '../components/CodeViewer.vue'

const props = defineProps({
  id: String
})

const route = useRoute()
const chapterId = computed(() => props.id || route.params.id)
const currentFile = ref(null)
const language = ref('c')

// 根据语言生成文件路径
const currentFilePath = computed(() => {
  if (!currentFile.value) return null
  if (language.value === 'python') {
    return currentFile.value.pyPath || currentFile.value.path.replace(/^c\//, 'py/').replace(/\.c$/, '.py')
  }
  return currentFile.value.path
})

const currentFileName = computed(() => {
  if (!currentFile.value) return ''
  if (language.value === 'python') {
    return currentFile.value.pyPath
      ? currentFile.value.pyPath.split('/').pop()
      : currentFile.value.name.replace(/\.c$/, '.py')
  }
  return currentFile.value.name
})

function switchLanguage(lang) {
  language.value = lang
}

const chapter = computed(() => getChapterById(chapterId.value))

// Reset current file when switching chapters
watch(chapterId, () => {
  currentFile.value = null
})

function selectFile(file) {
  currentFile.value = file
}

function closeDrawer() {
  currentFile.value = null
  language.value = 'c'
}

function getFolderDescription(folderName) {
  const descriptions = {
    mergesort: '归并排序是分治法的经典应用：将数组一分为二，分别排序后合并。时间复杂度 O(n log n)。',
    quicksort: '快速排序通过选择一个基准元素，将数组分为左右两部分，递归排序。平均时间复杂度 O(n log n)。',
    halfsearch: '二分查找在有序数组中通过每次将搜索范围缩小一半来查找目标值，时间复杂度 O(log n)。',
    bigcheng: '大整数乘法通过分治策略将 n 位数乘法分解为更小规模的计算，降低时间复杂度。',
    matrix: '矩阵乘法有多种实现方式：朴素算法 O(n³)，Strassen 分治算法可优化至 O(n^2.81)。',
    digui: '递归是分治法的基石，通过这些示例理解递归的基本结构与调用栈。',
    maopao: '冒泡排序通过相邻元素比较交换将最大元素"冒泡"到末尾，时间复杂度 O(n²)。',
    allpai: '全排列生成所有 n! 种排列方式，是回溯思想和分治策略的典型应用。',
    richeng: '循环赛日程表使用分治策略为 2^k 个选手安排比赛日程。',
    bag01: '0/1背包问题是动态规划的经典问题：给定容量和物品，求最大价值。',
    lcs: '最长公共子序列(LCS)问题是比较两个序列相似度的经典DP问题。',
    image: '图像压缩问题使用动态规划确定最优的像素段划分，平衡压缩比与存储空间。',
    homework: '课后练习中的算法实现示例。',
    huodong: '活动选择问题是贪心算法的经典案例：选择最多的不重叠活动。',
    huffman: 'Huffman编码是数据压缩经典算法，通过构造最优前缀码实现无损压缩。',
    bag: '贪心背包(部分背包)问题允许取物品的一部分，按单位价值贪心选择。',
    bestload: '最优装载问题：在载重限制下尽可能多地装载物品。',
    money: '找零问题：使用最少硬币凑出指定金额。',
    shortest: '最短路径问题：寻找图中两点之间的最短路径。',
    hui01bag: '0/1背包的回溯解法：通过深度优先搜索和剪枝寻找最优解。',
    loading: '装载问题的回溯解法：搜索最优的装载方案。',
    queue: 'N皇后问题的回溯解法：在 N×N 棋盘上放置 N 个皇后使其互不攻击。',
    xianbag01: '0/1背包的分支限界解法：使用队列或优先队列进行广度优先搜索。',
    tsp: '旅行商问题(TSP)：寻找最短的环游所有城市的路径。',
    graph: '图的两种基本遍历方式：广度优先(BFS)和深度优先(DFS)。'
  }
  return descriptions[folderName] || ''
}
</script>

<style scoped>
.chapter-view {
  max-width: 1000px;
  margin: 0 auto;
  padding: 0 24px;
}

.chapter-header {
  display: flex;
  gap: 16px;
  align-items: flex-start;
  padding: 32px 0 20px;
  border-bottom: 1px solid var(--border-color);
  margin-bottom: 24px;
}

.chapter-icon {
  font-size: 48px;
  flex-shrink: 0;
}

.chapter-title {
  font-size: 26px;
  font-weight: 800;
  color: var(--text-primary);
  margin-bottom: 4px;
}

.chapter-subtitle {
  font-size: 15px;
  color: var(--primary-color);
  font-weight: 500;
  margin-bottom: 6px;
}

.chapter-desc {
  font-size: 14px;
  color: var(--text-secondary);
  line-height: 1.6;
}

.section-label {
  font-size: 18px;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: 12px;
}

.topics-section {
  margin-bottom: 28px;
}

.topics-list {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.topic-pill {
  font-size: 13px;
  background: var(--active-bg);
  color: var(--primary-color);
  padding: 6px 16px;
  border-radius: 20px;
  font-weight: 500;
  border: 1px solid var(--border-color);
}

.folder-section {
  margin-bottom: 28px;
}

.folder-title {
  font-size: 17px;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: 6px;
  padding-bottom: 8px;
  border-bottom: 2px solid var(--border-color);
}

.folder-hint {
  font-size: 13px;
  color: var(--text-tertiary);
  margin-bottom: 12px;
  line-height: 1.5;
}

/* 动态演示入口 */
.demo-entry {
  margin-bottom: 12px;
}

.demo-link {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 12px 16px;
  background: linear-gradient(135deg, rgba(59, 130, 246, 0.08), rgba(139, 92, 246, 0.08));
  border: 1px solid rgba(59, 130, 246, 0.25);
  border-radius: 10px;
  text-decoration: none;
  transition: all 0.2s ease;
}

.demo-link:hover {
  background: linear-gradient(135deg, rgba(59, 130, 246, 0.15), rgba(139, 92, 246, 0.15));
  border-color: var(--primary-color);
  transform: translateY(-1px);
  box-shadow: 0 4px 12px rgba(59, 130, 246, 0.15);
  text-decoration: none;
}

.demo-link-icon {
  font-size: 24px;
  flex-shrink: 0;
}

.demo-link-text {
  font-size: 15px;
  font-weight: 700;
  color: var(--primary-color);
  white-space: nowrap;
}

.demo-link-desc {
  font-size: 13px;
  color: var(--text-secondary);
  flex: 1;
}

.demo-link-arrow {
  font-size: 18px;
  color: var(--primary-color);
  font-weight: 700;
  flex-shrink: 0;
}

.file-list {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 10px;
}

.file-item {
  background: var(--card-bg);
  border: 1px solid var(--border-color);
  border-radius: 10px;
  padding: 14px;
  cursor: pointer;
  transition: all 0.2s ease;
}

.file-item:hover {
  border-color: var(--primary-color);
  box-shadow: 0 2px 8px rgba(0,0,0,0.06);
}

.file-item.active {
  border-color: var(--primary-color);
  background: var(--active-bg);
  box-shadow: 0 0 0 2px rgba(59, 130, 246, 0.15);
}

.file-item-header {
  display: flex;
  align-items: center;
  gap: 6px;
  margin-bottom: 4px;
}

.file-item-icon {
  font-size: 14px;
}

.file-item-name {
  font-family: 'Fira Code', 'Consolas', monospace;
  font-size: 13px;
  font-weight: 600;
  color: var(--primary-color);
}

.file-item-label {
  font-size: 11px;
  color: var(--text-tertiary);
  background: var(--tag-bg);
  padding: 1px 6px;
  border-radius: 4px;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.file-item-desc {
  font-size: 12px;
  color: var(--text-tertiary);
  line-height: 1.4;
  margin-left: 20px;
}

/* ========== Drawer ========== */
.drawer-overlay {
  position: fixed;
  inset: 0;
  z-index: 1000;
  background: rgba(0, 0, 0, 0.45);
  display: flex;
  justify-content: flex-end;
}

.drawer-panel {
  width: min(720px, 90vw);
  height: 100%;
  background: var(--bg);
  display: flex;
  flex-direction: column;
  box-shadow: -4px 0 24px rgba(0, 0, 0, 0.15);
}

.drawer-header {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 16px 20px;
  border-bottom: 1px solid var(--border-color);
  flex-shrink: 0;
}

.drawer-title {
  font-size: 17px;
  font-weight: 700;
  color: var(--text-primary);
  margin-right: auto;
}

.drawer-lang-tabs {
  display: flex;
  gap: 4px;
  background: var(--hover-bg);
  padding: 3px;
  border-radius: 8px;
}

.lang-tab {
  background: none;
  border: none;
  padding: 6px 16px;
  border-radius: 6px;
  font-size: 13px;
  font-weight: 600;
  cursor: pointer;
  color: var(--text-secondary);
  transition: all 0.15s;
  font-family: var(--mono);
}

.lang-tab:hover {
  color: var(--text-primary);
}

.lang-tab.active {
  background: var(--bg);
  color: var(--primary-color);
  box-shadow: 0 1px 3px rgba(0,0,0,0.1);
}

.drawer-close-btn {
  background: none;
  border: none;
  font-size: 20px;
  cursor: pointer;
  color: var(--text-secondary);
  padding: 4px 10px;
  border-radius: 6px;
  transition: all 0.15s;
}

.drawer-close-btn:hover {
  background: var(--hover-bg);
  color: var(--text-primary);
}

.drawer-body {
  flex: 1;
  overflow-y: auto;
  padding: 0;
}

.drawer-body .code-viewer {
  border-radius: 0;
  border: none;
  min-height: 100%;
}

/* 抽屉过渡动画 */
.drawer-enter-active,
.drawer-leave-active {
  transition: opacity 0.25s ease;
}

.drawer-enter-active .drawer-panel,
.drawer-leave-active .drawer-panel {
  transition: transform 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

.drawer-enter-from,
.drawer-leave-to {
  opacity: 0;
}

.drawer-enter-from .drawer-panel,
.drawer-leave-to .drawer-panel {
  transform: translateX(100%);
}

.not-found {
  text-align: center;
  padding: 80px 20px;
}

.not-found h2 {
  font-size: 24px;
  margin-bottom: 8px;
  color: var(--text-primary);
}

.back-link {
  display: inline-block;
  margin-top: 16px;
  color: var(--primary-color);
  text-decoration: none;
  font-weight: 600;
}

.back-link:hover {
  text-decoration: underline;
}
</style>
