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

cloud.init({ env: cloud.DYNAMIC_CURRENT_ENV })
const db = cloud.database()
const _ = db.command

function timeText(ts) {
  if (!ts) return ''
  const d = new Date(ts)
  const hh = String(d.getHours()).padStart(2, '0')
  const mm = String(d.getMinutes()).padStart(2, '0')
  const sameDay = new Date().toDateString() === d.toDateString()
  if (sameDay) return `${hh}:${mm}`
  return `${d.getMonth() + 1}/${d.getDate()} ${hh}:${mm}`
}

async function userToPeer(u) {
  return { id: u._id, name: u.nickname || '用户', avatarKey: u.avatarKey || 'gradient-avatar-1', avatarUrl: u.avatarUrl || '' }
}

exports.main = async event => {
  const { OPENID } = cloud.getWXContext()
  if (!OPENID) throw new Error('no openid in wx context')

  let convId = event.conversationId || ''
  let peer = null

  // Open by target user — resolve peer and find an existing conversation.
  if (!convId && event.targetUserId) {
    const tRes = await db.collection('users').doc(event.targetUserId).get().catch(() => null)
    const t = tRes && tRes.data
    if (t) {
      peer = await userToPeer(t)
      const ex = await db.collection('conversations')
        .where({ type: 'single', memberOpenids: _.all([OPENID, t.openid]) })
        .limit(1)
        .get()
        .catch(() => ({ data: [] }))
      if (ex.data.length) convId = ex.data[0]._id
    }
  }

  // Open by conversation — resolve the other member as peer.
  if (convId && !peer) {
    const c = await db.collection('conversations').doc(convId).get().catch(() => null)
    if (c && c.data) {
      const otherOpenid = (c.data.memberOpenids || []).find(o => o !== OPENID)
      if (otherOpenid) {
        const oRes = await db.collection('users').where({ openid: otherOpenid }).limit(1).get()
        if (oRes.data[0]) peer = await userToPeer(oRes.data[0])
      }
      if (!peer) {
        peer = { id: '', name: c.data.title || '对话', avatarKey: c.data.avatarKey || 'gradient-avatar-1', avatarUrl: '' }
      }
    }
  }

  let messages = []
  if (convId) {
    const res = await db.collection('messages')
      .where({ conversationId: convId })
      .orderBy('createdAt', 'desc')
      .limit(50)
      .get()
      .catch(() => ({ data: [] }))
    messages = res.data.reverse().map(m => ({
      _id: m._id,
      fromMe: m.fromOpenid === OPENID,
      content: m.content,
      type: m.type || 'text',
      createdAt: m.createdAt,
      timeText: timeText(m.createdAt)
    }))

    // Mark this conversation read for me.
    await db.collection('conversations').doc(convId).update({
      data: { unreadOpenids: _.pull(OPENID), [`unreadCounts.${OPENID}`]: 0 }
    }).catch(() => {})
  }

  return { conversationId: convId, peer, messages }
}