const cloud = require('wx-server-sdk')
cloud.init({ env: cloud.DYNAMIC_CURRENT_ENV })
const db = cloud.database()
const _ = db.command

exports.main = async (event, context) => {
  const { OPENID } = cloud.getWXContext()
  const { postId } = event

  if (!postId) return { code: -1, message: '缺少 postId' }

  try {
    // 检查是否已点赞
    const existRes = await db.collection('likes')
      .where({ userId: OPENID, postId })
      .get()

    let liked
    let delta

    if (existRes.data.length > 0) {
      // 取消点赞
      await db.collection('likes').doc(existRes.data[0]._id).remove()
      delta = -1
      liked = false
    } else {
      // 点赞
      await db.collection('likes').add({
        data: {
          userId: OPENID,
          postId,
          createdAt: db.serverDate(),
        },
      })
      delta = 1
      liked = true
    }

    // 原子更新帖子点赞数
    await db.collection('posts').doc(postId).update({
      data: { likeCount: _.inc(delta) },
    })

    // 获取最新计数
    const postRes = await db.collection('posts').doc(postId).field({ likeCount: true }).get()

    return {
      code: 0,
      data: { liked, count: postRes.data.likeCount },
    }
  } catch (e) {
    return { code: -1, message: e.message }
  }
}