const cloud = require('wx-server-sdk');

cloud.init({ env: cloud.DYNAMIC_CURRENT_ENV });

const CONFIG_PATH = 'content/page-config.json';

const DIFFICULTY_LABELS = {
    1: '入门',
    2: '基础',
    3: '进阶',
    4: '挑战',
};

function ageBand(min, max) {
    return `${min}-${max}岁`;
}

function toDisplayItem(ws) {
    return {
        id: ws._id,
        title: ws.title || '',
        subtitle: ws.subtitle || '',
        previewImg: ws.previewImg || '',
        ageBand: ageBand(ws.ageMin || 0, ws.ageMax || 0),
        ageMin: ws.ageMin || 0,
        ageMax: ws.ageMax || 0,
        difficulty: ws.difficulty || 2,
        difficultyLabel: DIFFICULTY_LABELS[ws.difficulty] || '基础',
        path: ws.path || '',
        available: true,
        likes: (ws.likes || 0) + (ws.likes_seed || 0),
        downloads: (ws.downloads || 0) + (ws.downloads_seed || 0),
        date: ws.updatedAt
            ? new Date(ws.updatedAt).toISOString().slice(0, 10)
            : new Date().toISOString().slice(0, 10),
    };
}

function toHomeDisplayItem(ws) {
    return {
        id: ws._id,
        title: ws.title || '',
        subtitle: ws.subtitle || '',
        category: ws.category || '',
        ageBand: ageBand(ws.ageMin || 0, ws.ageMax || 0),
        difficulty: DIFFICULTY_LABELS[ws.difficulty] || '基础',
        icon: '',
        previewImg: ws.previewImg || '',
        badge: ws.isNew ? 'NEW' : ws.isHot ? 'HOT' : '',
        path: ws.path || '',
        available: true,
    };
}

const HOME_AGE_BANDS = [
    { key: '3-4', label: '3-4 岁', desc: '启蒙认知', path: '/pages/age/age' },
    { key: '4-5', label: '4-5 岁', desc: '基础练习', path: '/pages/age/age' },
    { key: '5-6', label: '5-6 岁', desc: '能力提升', path: '/pages/age/age' },
    { key: '6-7', label: '6-7 岁', desc: '幼小衔接', path: '/pages/age/age' },
    { key: '7-8', label: '7-8 岁', desc: '知识拓展', path: '/pages/age/age' },
];

async function readCurrentConfig() {
    const db = cloud.database();
    try {
        const { data } = await db
            .collection('page_configs')
            .doc('current')
            .get();
        return data;
    } catch {
        return { home: null, category: null, age: null, version: 0 };
    }
}

async function saveConfig(config) {
    const db = cloud.database();

    // 1. Save to database (source of truth)
    const toSave = { ...config };
    delete toSave._id; // _id can't be in update data
    try {
        await db.collection('page_configs').doc('current').get();
        await db.collection('page_configs').doc('current').update({
            data: toSave,
        });
    } catch {
        await db.collection('page_configs').doc('current').set({
            data: toSave,
        });
    }

    // 2. Upload to cloud storage (for mini-program pre-fetch)
    const buffer = Buffer.from(JSON.stringify(config), 'utf-8');
    await cloud.uploadFile({
        cloudPath: CONFIG_PATH,
        fileContent: buffer,
    });
}

async function buildCategoryData(db) {
    // Get all categories
    const { data: categories } = await db
        .collection('categories')
        .orderBy('sortOrder', 'asc')
        .get();

    // Get all active worksheets
    const { data: worksheets } = await db
        .collection('worksheets')
        .where({ status: 'active' })
        .orderBy('sortOrder', 'asc')
        .orderBy('updatedAt', 'desc')
        .limit(100)
        .get();

    // Group by category
    const grouped = {};
    for (const ws of worksheets) {
        const cat = ws.category || 'unknown';
        if (!grouped[cat]) grouped[cat] = [];
        grouped[cat].push(toDisplayItem(ws));
    }

    const categoryData = {
        searchPlaceholder: '搜索练习纸...',
        categories: categories.map((cat) => ({
            id: cat._id,
            name: cat.name || '',
            icon: cat.icon || '',
            items: grouped[cat._id] || [],
        })),
    };

    const stats = {};
    for (const cat of categoryData.categories) {
        stats[cat.id] = cat.items.length;
    }

    return { categoryData, stats };
}

async function buildHomeData(db, event) {
    const featuredIds = Array.isArray(event.featuredIds)
        ? event.featuredIds
        : [];
    const hotIds = Array.isArray(event.hotIds) ? event.hotIds : [];
    const sectionConfigs = Array.isArray(event.sections) ? event.sections : [];

    // Collect all referenced worksheet ids
    const allIds = new Set([
        ...featuredIds,
        ...hotIds,
        ...sectionConfigs.flatMap((s) => s.worksheetIds || []),
    ]);

    // Batch query all referenced worksheets
    const wsMap = {};
    if (allIds.size > 0) {
        const _ = db.command;
        const { data } = await db
            .collection('worksheets')
            .where({ _id: _.in([...allIds]) })
            .limit(100)
            .get();
        for (const ws of data) {
            wsMap[ws._id] = ws;
        }
    }

    // Build categoryTabs from categories collection
    const { data: categories } = await db
        .collection('categories')
        .orderBy('sortOrder', 'asc')
        .get();
    const categoryTabs = [
        { id: 'all', name: '全部' },
        ...categories.map((c) => ({ id: c._id, name: c.name || '' })),
    ];

    // Build featured / hot arrays
    const featured = featuredIds
        .filter((id) => wsMap[id])
        .map((id) => toHomeDisplayItem(wsMap[id]));
    const hot = hotIds
        .filter((id) => wsMap[id])
        .map((id) => toHomeDisplayItem(wsMap[id]));

    // Build sections
    const sections = sectionConfigs
        .filter((s) => s.id && Array.isArray(s.worksheetIds))
        .map((s) => {
            const cat = categories.find((c) => c._id === s.id);
            return {
                id: s.id,
                title: cat ? cat.name : s.id,
                subtitle: s.subtitle || '',
                morePath: s.morePath || '',
                items: (s.worksheetIds || [])
                    .filter((id) => wsMap[id])
                    .map((id) => toHomeDisplayItem(wsMap[id])),
            };
        });

    const homeData = {
        searchPlaceholder: '搜索你喜欢的练习册...',
        categoryTabs,
        ageBands: HOME_AGE_BANDS,
        featured,
        hot,
        sections,
    };

    return { homeData };
}

function normalizeIdArray(value) {
    if (!Array.isArray(value)) return [];
    return value.map((x) => String(x || '').trim()).filter(Boolean);
}

function extractHomeSeedFromCurrentConfig(home) {
    const featuredIds = normalizeIdArray(home?.featured?.map((x) => x?.id));
    const hotIds = normalizeIdArray(home?.hot?.map((x) => x?.id));
    const sections = Array.isArray(home?.sections)
        ? home.sections
              .map((s) => ({
                  id: String(s?.id || '').trim(),
                  subtitle: String(s?.subtitle || '').trim(),
                  morePath: String(s?.morePath || '').trim(),
                  worksheetIds: normalizeIdArray(s?.items?.map((it) => it?.id)),
              }))
              .filter((s) => s.id && Array.isArray(s.worksheetIds))
        : [];

    return { featuredIds, hotIds, sections };
}

exports.main = async (event) => {
    try {
        const db = cloud.database();
        const page = String(event.page || '').trim();

        if (page !== 'category' && page !== 'home' && page !== 'all') {
            throw new Error('page 参数不合法，支持 category / home / all');
        }

        const config = await readCurrentConfig();

        // 当未提供 featuredIds/hotIds/sections 时，默认从现有 home 配置反推出 worksheetIds
        // 用于“只想重建展示数据（比如 ageBand/previewImg/difficultyLabel），但不想手工维护 id 列表”的场景。
        const homeSeed = extractHomeSeedFromCurrentConfig(config.home || {});
        const homeEvent = {
            ...event,
            featuredIds:
                Array.isArray(event.featuredIds) && event.featuredIds.length > 0
                    ? event.featuredIds
                    : homeSeed.featuredIds,
            hotIds:
                Array.isArray(event.hotIds) && event.hotIds.length > 0
                    ? event.hotIds
                    : homeSeed.hotIds,
            sections:
                Array.isArray(event.sections) && event.sections.length > 0
                    ? event.sections
                    : homeSeed.sections,
        };

        if (page === 'category') {
            const { categoryData, stats } = await buildCategoryData(db);
            config.category = categoryData;
            config.version = (config.version || 0) + 1;
            config.updatedAt = new Date().toISOString();

            await saveConfig(config);

            return {
                success: true,
                data: {
                    version: config.version,
                    updatedAt: config.updatedAt,
                    stats,
                },
            };
        }

        if (page === 'home') {
            const { homeData } = await buildHomeData(db, homeEvent);
            config.home = homeData;
            // [v3.0] 清空 category/age 字段，分类页已改为实时接口查询
            // 如需恢复静态配置，注释掉以下两行即可
            config.category = null;
            config.age = null;
            config.version = (config.version || 0) + 1;
            config.updatedAt = new Date().toISOString();

            await saveConfig(config);

            return {
                success: true,
                data: {
                    version: config.version,
                    updatedAt: config.updatedAt,
                    featured: homeData.featured.length,
                    hot: homeData.hot.length,
                    sections: homeData.sections.length,
                },
            };
        }

        if (page === 'all') {
            const { categoryData, stats } = await buildCategoryData(db);
            const { homeData } = await buildHomeData(db, homeEvent);
            // [v3.0] 清空 category/age 字段，分类页已改为实时接口查询
            // 如需恢复静态配置，将下面 null 改回 categoryData 即可
            config.category = null;
            config.age = null;
            config.home = homeData;
            config.version = (config.version || 0) + 1;
            config.updatedAt = new Date().toISOString();

            await saveConfig(config);

            return {
                success: true,
                data: {
                    version: config.version,
                    updatedAt: config.updatedAt,
                    stats,
                    featured: homeData.featured.length,
                    hot: homeData.hot.length,
                    sections: homeData.sections.length,
                },
            };
        }
    } catch (error) {
        return {
            success: false,
            message:
                error instanceof Error ? error.message : '生成分类页数据失败',
        };
    }
};