const cloud = require('wx-server-sdk');
cloud.init({ env: cloud.DYNAMIC_CURRENT_ENV });

const db = cloud.database();
const command = db.command;

exports.main = async (event) => {
    const wxContext = cloud.getWXContext();
    const openid = wxContext.OPENID;

    // 获取 userId
    const { data: users } = await db
        .collection('users')
        .where({ openid })
        .limit(1)
        .get();

    if (users.length === 0) {
        return { code: -1, message: '用户未登录' };
    }

    const userId = users[0]._id;
    const { action } = event;

    switch (action) {
        case 'add':
            return await handleAdd(userId, event);
        case 'list':
            return await handleList(userId, event);
        case 'count':
            return await handleCount(userId);
        default:
            return { code: -1, message: '未知操作' };
    }
};

async function handleAdd(userId, event) {
    const { worksheetId } = event;
    if (!worksheetId) return { code: -1, message: 'worksheetId 不能为空' };

    const collection = db.collection('download_logs');

    const record = {
        userId,
        worksheetId,
        createdAt: db.serverDate(),
    };
    const { _id } = await collection.add({ data: record });

    // worksheets.downloads +1
    try {
        await db.collection('worksheets').doc(worksheetId).update({
            data: {
                downloads: command.inc(1),
                updatedAt: db.serverDate(),
            },
        });
    } catch (e) {
        console.warn('更新 worksheets.downloads 失败', e);
    }

    return { code: 0, data: { _id, ...record } };
}

const MAX_LIST_PAGE_SIZE = 30;

async function handleList(userId, event) {
    const { page = 1, pageSize = MAX_LIST_PAGE_SIZE } = event;
    const limit = Math.min(Math.max(1, Number(pageSize) || 1), MAX_LIST_PAGE_SIZE);
    const skip = (page - 1) * limit;

    const collection = db.collection('download_logs');

    const { data: logs } = await collection
        .where({ userId })
        .orderBy('createdAt', 'desc')
        .skip(skip)
        .limit(limit)
        .get();

    if (logs.length === 0) {
        return { code: 0, data: [] };
    }

    // 关联查询 worksheets 信息
    const worksheetIds = [...new Set(logs.map((l) => l.worksheetId))];
    const { data: worksheets } = await db
        .collection('worksheets')
        .where({ _id: command.in(worksheetIds) })
        .get();

    const worksheetMap = {};
    worksheets.forEach((w) => {
        worksheetMap[w._id] = w;
    });

    const result = logs.map((l) => ({
        ...l,
        worksheet: worksheetMap[l.worksheetId] || null,
    }));

    return { code: 0, data: result };
}

async function handleCount(userId) {
    const collection = db.collection('download_logs');
    const res = await collection.where({ userId }).count();
    return { code: 0, data: { count: res.total || 0 } };
}