/**
 * 同步管理：失败入队，启动时重试
 * Why：自建后端、HTTPS 链路、定时任务任一环节抖动都会导致单次写入丢失。本地队列兜底，保证最终一致。
 */

const api = require('./api')

const QUEUE_KEY = 'pending_sync_queue'

function loadQueue() {
  try { return wx.getStorageSync(QUEUE_KEY) || [] } catch (e) { return [] }
}

function saveQueue(q) {
  try { wx.setStorageSync(QUEUE_KEY, q) } catch (e) {}
}

function enqueue(item) {
  const q = loadQueue()
  q.push({ ...item, ts: Date.now() })
  saveQueue(q)
}

async function dispatch(item) {
  if (item.kind === 'person')      return api.person(item.action, item.data)
  if (item.kind === 'anniversary') return api.anniversary(item.action, item.data)
  throw new Error('unknown sync kind: ' + item.kind)
}

// 立即尝试同步；失败入队
async function syncOrEnqueue(item) {
  try {
    const res = await dispatch(item)
    if (res && res.success === false) throw new Error(res.error || 'server returned failure')
    return true
  } catch (err) {
    console.warn('[sync] 失败已入队:', item.kind, item.action, err.message || err)
    enqueue(item)
    return false
  }
}

// 尝试 flush 整个队列，失败的留下下次再试
async function flush() {
  const q = loadQueue()
  if (q.length === 0) return { flushed: 0, remaining: 0 }
  const remaining = []
  let flushed = 0
  for (const item of q) {
    try {
      const res = await dispatch(item)
      if (res && res.success === false) throw new Error(res.error || 'server returned failure')
      flushed++
    } catch (err) {
      remaining.push(item)
    }
  }
  saveQueue(remaining)
  if (flushed > 0) console.log(`[sync] 队列 flush 完成：成功 ${flushed}，剩余 ${remaining.length}`)
  return { flushed, remaining: remaining.length }
}

function getPendingCount() {
  return loadQueue().length
}

module.exports = { syncOrEnqueue, flush, getPendingCount }