const { formatDate } = require('./util')
const cloud = require('./cloud')

const RECORDS_KEY = 'training_records'
const SETTINGS_KEY = 'user_settings'
const STREAK_KEY = 'current_streak'
const CUSTOM_PLANS_KEY = 'custom_plans'

/**
 * Backfill an `id` for any record that doesn't have one.
 * Older records (e.g. data restored from cloud or migrated from a build
 * that didn't yet write the id field) come in without an id, which makes
 * delete-by-id fail with "记录数据异常". Assign a stable, deterministic id
 * derived from the record's position + payload so the user can still
 * delete them.
 *
 * Returns true if any record was patched.
 */
const _ensureRecordIds = (records) => {
  if (!records || typeof records !== 'object') return false
  let changed = false
  Object.keys(records).forEach((month) => {
    const list = records[month]
    if (!Array.isArray(list)) return
    list.forEach((r, i) => {
      if (r && (r.id == null || r.id === '')) {
        // month is YYYY-MM; strip the dash so the id stays a safe token
        const m = String(month).replace(/[^0-9]/g, '')
        r.id = `legacy-${m}-${i}-${r.duration || 0}`
        changed = true
      }
    })
  })
  return changed
}

const getRecords = () => {
  const records = wx.getStorageSync(RECORDS_KEY) || {}
  if (_ensureRecordIds(records)) {
    // Persist the backfill so subsequent calls don't re-mutate; the cloud
    // will resync on the next saveRecord/deleteRecord.
    try { wx.setStorageSync(RECORDS_KEY, records) } catch (e) {}
  }
  return records
}

const saveRecord = (record) => {
  record.id = String(Date.now())
  const records = getRecords()
  const month = record.date.substring(0, 7)
  if (!records[month]) records[month] = []
  records[month].push(record)
  records[month].sort((a, b) => b.date.localeCompare(a.date))
  wx.setStorageSync(RECORDS_KEY, records)
  cloud.pushAll()
}

const deleteRecord = (recordId) => {
  if (!recordId && recordId !== 0) return  // guard against undefined/null
  const id = String(recordId)
  if (!id || id === 'undefined' || id === 'null') return
  const records = getRecords()
  let found = false
  Object.keys(records).forEach((month) => {
    const before = records[month].length
    records[month] = records[month].filter((r) => String(r.id) !== id)
    if (records[month].length < before) found = true
    if (records[month].length === 0) delete records[month]
  })
  if (!found) return  // id not found, don't overwrite storage
  wx.setStorageSync(RECORDS_KEY, records)
  // Re-validate streak: deleting the last record for a day should break the streak
  validateStreak()
  cloud.pushAll()
}

const getRecordsByMonth = (month) => {
  const records = getRecords()
  return records[month] || []
}

const getTotalStats = () => {
  const records = getRecords()
  let totalDuration = 0
  let totalSessions = 0
  let maxDuration = 0
  Object.keys(records).forEach((key) => {
    records[key].forEach((r) => {
      totalDuration += r.duration
      totalSessions++
      if (r.duration > maxDuration) maxDuration = r.duration
    })
  })
  return { totalDuration, totalSessions, maxDuration }
}

const getSettings = () => wx.getStorageSync(SETTINGS_KEY) || {
  planId: 'beginner',
  voiceGuide: true,
  vibrate: true
}

const saveSettings = (settings) => {
  wx.setStorageSync(SETTINGS_KEY, settings)
  cloud.pushAll()
}

const getStreak = () => wx.getStorageSync(STREAK_KEY) || { count: 0, lastDate: '' }

/**
 * User-customized training plans, keyed by planId (e.g. 'beginner').
 * Each value is a full plan object built by `utils/plan.generatePlanDays`
 * plus the editor's formula fields (startTarget / increment / cycleDays).
 *
 * Storage shape mirrors `getRecords()`: an object map so partial writes
 * don't have to read+modify+write the whole collection.
 */
const getCustomPlans = () => {
  const raw = wx.getStorageSync(CUSTOM_PLANS_KEY)
  if (raw && typeof raw === 'object' && !Array.isArray(raw)) return raw
  return {}
}

const saveCustomPlan = (planId, planData) => {
  if (!planId) return
  const plans = getCustomPlans()
  plans[planId] = planData
  wx.setStorageSync(CUSTOM_PLANS_KEY, plans)
  cloud.pushAll()
}

const resetCustomPlan = (planId) => {
  if (!planId) return
  const plans = getCustomPlans()
  if (!(planId in plans)) return
  delete plans[planId]
  wx.setStorageSync(CUSTOM_PLANS_KEY, plans)
  cloud.pushAll()
}

/**
 * Validate streak against actual training records.
 * Call on app launch to correct any inconsistencies
 * (e.g. after deleting the only record for a day).
 */
const validateStreak = () => {
  const streak = getStreak()
  if (!streak.lastDate) return streak

  const today = getToday()
  const yesterday = getDateOffset(today, -1)
  const records = getRecords()
  const allDates = new Set()
  Object.values(records).forEach(monthRecs => {
    monthRecs.forEach(r => allDates.add(r.date))
  })

  // If lastDate is today, check today still has records
  if (streak.lastDate === today) {
    if (!allDates.has(today)) {
      // Today's records were deleted
      if (allDates.has(yesterday)) {
        streak.lastDate = yesterday
        streak.count = Math.max(1, streak.count - 1)
      } else {
        streak.count = 0
        streak.lastDate = ''
      }
      wx.setStorageSync(STREAK_KEY, streak)
    }
    return streak
  }

  // If lastDate is not today and not yesterday, streak is already broken
  // (updateStreak handles reset on next training), no action needed here
  return streak
}

const updateStreak = (date) => {
  const streak = getStreak()
  const today = date || getToday()
  const yesterday = getDateOffset(today, -1)

  if (streak.lastDate === today) return streak

  if (streak.lastDate === yesterday) {
    streak.count += 1
  } else {
    streak.count = 1
  }
  streak.lastDate = today
  wx.setStorageSync(STREAK_KEY, streak)
  cloud.pushAll()
  return streak
}

const getToday = () => formatDate(new Date())

const getDateOffset = (dateStr, offset) => {
  // Use YYYY/MM/DD for iOS compatibility (YYYY-MM-DD may fail on some iOS)
  const d = new Date(dateStr.replace(/-/g, '/'))
  d.setDate(d.getDate() + offset)
  return formatDate(d)
}

const getTodayRecord = () => {
  const today = getToday()
  const records = getRecords()
  let totalDuration = 0
  let hasRecord = false
  Object.keys(records).forEach((month) => {
    records[month].forEach((r) => {
      if (r.date === today) {
        totalDuration += r.duration
        hasRecord = true
      }
    })
  })
  return hasRecord ? { date: today, duration: totalDuration } : null
}

module.exports = {
  getRecords,
  saveRecord,
  deleteRecord,
  getRecordsByMonth,
  getTotalStats,
  getSettings,
  saveSettings,
  getCustomPlans,
  saveCustomPlan,
  resetCustomPlan,
  getStreak,
  validateStreak,
  updateStreak,
  getToday,
  getDateOffset,
  getTodayRecord
}