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,
        downloads: ws.downloads || 0,
        date: ws.updatedAt
            ? new Date(ws.updatedAt).toISOString().slice(0, 10)
            : new Date().toISOString().slice(0, 10),
    };
}

async function readCurrentConfig() {
    try {
        const res = await cloud.downloadFile({ fileID: CONFIG_PATH });
        return JSON.parse(res.fileContent.toString('utf-8'));
    } catch {
        return { home: null, category: null, age: null, version: 0 };
    }
}

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 };
}

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

        if (page !== 'category') {
            throw new Error('当前仅支持 page=category');
        }

        const { categoryData, stats } = await buildCategoryData(db);

        // Read current config, merge, bump version
        const config = await readCurrentConfig();
        config.category = categoryData;
        config.version = (config.version || 0) + 1;
        config.updatedAt = new Date().toISOString();

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

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