package service

import (
	"errors"
	"fmt"
	"strconv"
	"strings"
	"time"

	"gorm.io/gorm"
	"gorm.io/gorm/clause"

	"laic-backend/cache"
	"laic-backend/common"
	"laic-backend/logger"
	"laic-backend/model"
	"laic-backend/tool"
	"laic-backend/vo"
)

const (
	gbBytes                 = 1024 * 1024 * 1024 // 1 GB 字节数
	defaultTrafficUnitPrice = 10.0               // 云媒体流量单价（元/GB）
)

// trafficDeductLua 原子扣减：key 不存在时用 MySQL 快照兜底初始化，再判断并扣减。
// 返回 {status, before, after}：status=1 成功，0 余额不足。
const trafficDeductLua = `
local key = KEYS[1]
local delta = tonumber(ARGV[1])
local fallback = tonumber(ARGV[2])
local before = 0
if redis.call('EXISTS', key) == 0 then
  redis.call('SET', key, fallback)
  before = fallback
else
  before = tonumber(redis.call('GET', key))
end
if before < delta then
  return {0, before, before}
end
local after = redis.call('DECRBY', key, delta)
return {1, before, after}
`

type BillingService struct{}

var DefaultBillingService = &BillingService{}

// CarrierAPI 运营商接口抽象（查询用量 / 充值）
type CarrierAPI interface {
	QueryUsage(iccid string) (usedGb float64, carrierStatus string, err error)
	Recharge(iccid string, amountGb int) (orderNo string, err error)
}

// MockCarrierAPI 运营商 Mock（仅供开发注入，不作为默认生产通道）
type MockCarrierAPI struct{}

func (m *MockCarrierAPI) QueryUsage(iccid string) (float64, string, error) {
	return 0.0, "normal", nil
}

func (m *MockCarrierAPI) Recharge(iccid string, amountGb int) (string, error) {
	return fmt.Sprintf("MOCK-%d", time.Now().UnixNano()), nil
}

// carrier 默认禁用，未接入真实运营商前不产生虚假用量或充值成功。
var carrier CarrierAPI

// mysqlBalance 读取用户 MySQL 流量快照
func (b *BillingService) mysqlBalance(userID int64) (int64, error) {
	var u model.User
	if err := common.DB.Select("traffic_balance").First(&u, userID).Error; err != nil {
		return 0, err
	}
	return u.TrafficBalance, nil
}

// GetBalance 查询流量余额（Redis 权威，缺 key 时用 MySQL 快照兜底）
func (b *BillingService) GetBalance(userID int64) (*vo.TrafficBalanceVO, *common.BusiError) {
	balance, err := b.currentBalance(userID)
	if err != nil {
		logger.ERROR("查询流量余额失败", err)
		return nil, common.ErrInternal
	}
	return &vo.TrafficBalanceVO{
		BalanceBytes: balance,
		BalanceGb:    float64(balance) / float64(gbBytes),
	}, nil
}

// currentBalance 返回 Redis 权威余额；缺 key 时先用 MySQL 快照 SetNX 初始化
func (b *BillingService) currentBalance(userID int64) (int64, error) {
	key := cache.TrafficKeyOf(userID)
	bal, err := common.GetInt64(key)
	if err == nil {
		return bal, nil
	}
	fallback, err := b.mysqlBalance(userID)
	if err != nil {
		return 0, err
	}
	if _, err := common.SetNX(key, fallback); err != nil {
		return 0, err
	}
	// SetNX 失败说明并发下已有值，重读一次
	bal, err = common.GetInt64(key)
	if err != nil {
		return fallback, nil
	}
	return bal, nil
}

// Deduct 扣减流量（直播/回放/下载计费），原子 Lua + 账本落库
func (b *BillingService) Deduct(userID int64, bytes int64, sourceType string, sourceID int64) (bool, *common.BusiError) {
	if bytes <= 0 {
		return true, nil
	}
	fallback, err := b.mysqlBalance(userID)
	if err != nil {
		logger.ERROR("读取流量快照失败", err)
		return false, common.ErrInternal
	}
	key := cache.TrafficKeyOf(userID)
	res, err := common.GetLuaInt64s(trafficDeductLua, []string{key}, bytes, fallback)
	if err != nil {
		logger.ERROR("流量扣减 Lua 执行失败", err)
		return false, common.ErrInternal
	}
	if len(res) < 3 {
		return false, common.ErrInternal
	}
	status, before, after := res[0], res[1], res[2]
	if status == 0 {
		return false, common.ErrTrafficNotEnough
	}

	log := &model.TrafficUsageLog{
		ID:            mustID(),
		UserID:        userID,
		SourceType:    sourceType,
		SourceID:      sourceID,
		BytesUsed:     bytes,
		BalanceBefore: before,
		BalanceAfter:  after,
		CreatedAt:     time.Now(),
	}
	if err := common.DB.Create(log).Error; err != nil {
		logger.ERROR("流量账本落库失败", err)
		return false, common.ErrInternal
	}
	return true, nil
}

// credit 充值入账：Redis 权威自增 + MySQL 快照同步
func (b *BillingService) credit(userID int64, bytes int64) error {
	key := cache.TrafficKeyOf(userID)
	if _, err := b.currentBalance(userID); err != nil {
		return err
	}
	_, err := common.IncrBy(key, bytes)
	return err
}

// GetUsagePage 流量消费流水分页
func (b *BillingService) GetUsagePage(userID int64, req *vo.UsagePageReq) (*common.PageResponse[model.TrafficUsageLog], *common.BusiError) {
	db := common.DB.Model(&model.TrafficUsageLog{}).Where("user_id = ?", userID)
	if req.SourceType != "" {
		db = db.Where("source_type = ?", req.SourceType)
	}
	var total int64
	if err := db.Count(&total).Error; err != nil {
		return nil, common.ErrInternal
	}
	var list []model.TrafficUsageLog
	if err := db.Scopes(req.Paginate).Order("id DESC").Find(&list).Error; err != nil {
		return nil, common.ErrInternal
	}
	return common.Page(req.Pagination, total, list), nil
}

// GetOrderPage 流量订单分页
func (b *BillingService) GetOrderPage(userID int64, req *vo.OrderPageReq) (*common.PageResponse[model.TrafficOrder], *common.BusiError) {
	db := common.DB.Model(&model.TrafficOrder{}).Where("user_id = ?", userID)
	if req.PayStatus != "" {
		db = db.Where("pay_status = ?", req.PayStatus)
	}
	var total int64
	if err := db.Count(&total).Error; err != nil {
		return nil, common.ErrInternal
	}
	var list []model.TrafficOrder
	if err := db.Scopes(req.Paginate).Order("id DESC").Find(&list).Error; err != nil {
		return nil, common.ErrInternal
	}
	return common.Page(req.Pagination, total, list), nil
}

// CreateOrder 创建流量充值订单（待支付）
func (b *BillingService) CreateOrder(userID int64, amountGb int) (*model.TrafficOrder, *common.BusiError) {
	order := &model.TrafficOrder{
		ID:         mustID(),
		UserID:     userID,
		AmountGb:   amountGb,
		UnitPrice:  defaultTrafficUnitPrice,
		TotalPrice: float64(amountGb) * defaultTrafficUnitPrice,
		PayStatus:  "unpaid",
		CreatedAt:  time.Now(),
	}
	if err := common.DB.Create(order).Error; err != nil {
		logger.ERROR("创建流量订单失败", err)
		return nil, common.ErrInternal
	}
	return order, nil
}

// PayOrder 订单支付入账（admin 确认支付）
func (b *BillingService) PayOrder(orderID int64) (*model.TrafficOrder, *common.BusiError) {
	var order model.TrafficOrder
	now := time.Now()
	if err := common.DB.Transaction(func(tx *gorm.DB) error {
		if err := tx.Clauses(clause.Locking{Strength: "UPDATE"}).First(&order, orderID).Error; err != nil {
			return err
		}
		if order.PayStatus == "paid" {
			return common.ErrOrderPaid
		}
		bytes := int64(order.AmountGb) * gbBytes
		if err := tx.Model(&order).Updates(map[string]any{"pay_status": "paid", "paid_at": now}).Error; err != nil {
			return err
		}
		return tx.Model(&model.User{}).Where("id = ?", order.UserID).
			UpdateColumn("traffic_balance", gorm.Expr("traffic_balance + ?", bytes)).Error
	}); err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, common.ErrOrderNotFound
		}
		if busiErr, ok := err.(*common.BusiError); ok {
			return nil, busiErr
		}
		logger.ERROR("订单支付失败", err)
		return nil, common.ErrInternal
	}

	bytes := int64(order.AmountGb) * gbBytes
	if err := b.credit(order.UserID, bytes); err != nil {
		logger.ERROR("订单支付 Redis 入账失败", err)
		return nil, common.ErrInternal
	}
	order.PayStatus = "paid"
	order.PaidAt = &now
	return &order, nil
}

// ListSimCards SIM 卡列表
func (b *BillingService) ListSimCards(userID int64, req *vo.SimCardPageReq) (*common.PageResponse[model.SimCard], *common.BusiError) {
	db := common.DB.Model(&model.SimCard{}).Where("user_id = ?", userID)
	if req.Status != "" {
		db = db.Where("status = ?", req.Status)
	}
	var total int64
	if err := db.Count(&total).Error; err != nil {
		return nil, common.ErrInternal
	}
	var list []model.SimCard
	if err := db.Scopes(req.Paginate).Order("id DESC").Find(&list).Error; err != nil {
		return nil, common.ErrInternal
	}
	return common.Page(req.Pagination, total, list), nil
}

// GetSimRechargeLogPage SIM 卡充值记录分页
func (b *BillingService) GetSimRechargeLogPage(userID int64, req *vo.SimRechargeLogPageReq) (*common.PageResponse[model.SimRechargeLog], *common.BusiError) {
	db := common.DB.Model(&model.SimRechargeLog{}).Where("user_id = ?", userID)
	if req.SimCardID > 0 {
		db = db.Where("sim_card_id = ?", req.SimCardID)
	}
	if req.RechargeStatus != "" {
		db = db.Where("recharge_status = ?", req.RechargeStatus)
	}
	var total int64
	if err := db.Count(&total).Error; err != nil {
		return nil, common.ErrInternal
	}
	var list []model.SimRechargeLog
	if err := db.Scopes(req.Paginate).Order("id DESC").Find(&list).Error; err != nil {
		return nil, common.ErrInternal
	}
	return common.Page(req.Pagination, total, list), nil
}

// RechargeSimCard 当前未接入支付确认流程，不向运营商提交充值订单。
func (b *BillingService) RechargeSimCard(userID, simCardID int64, amountGb int) (*model.SimRechargeLog, *common.BusiError) {
	return nil, common.ErrCarrierUnavailable
}

// mustID 生成雪花 ID（失败返回 0，由 DB 约束兜底）
func mustID() int64 {
	id, err := tool.NextID()
	if err != nil {
		logger.ERROR("生成雪花 ID 失败", err)
		return 0
	}
	return id
}

// chargeLiveSessions 直播计费（定时任务，每 60s）：扫描进行中的会话按码率估算扣减
func (b *BillingService) chargeLiveSessions() {
	var sessions []model.LiveSession
	if err := common.DB.Where("phase IN ('starting','streaming')").Find(&sessions).Error; err != nil {
		logger.ERROR("扫描直播会话失败", err)
		return
	}
	now := time.Now()
	for i := range sessions {
		b.chargeLiveSession(&sessions[i], now)
	}
}

// chargeLiveSession 对单个直播会话按时长增量扣减；余额耗尽则停止推流
func (b *BillingService) chargeLiveSession(session *model.LiveSession, now time.Time) {
	var dock model.Dock
	if err := common.DB.Select("user_id").Where("dock_id = ?", session.DockID).First(&dock).Error; err != nil {
		return
	}

	lastKey := cache.LiveBilledKeyOf(session.ID)
	lastTs := int64(0)
	if v, err := common.GetInt64(lastKey); err == nil {
		lastTs = v
	} else if session.StartedAt != nil {
		lastTs = session.StartedAt.Unix()
	} else {
		lastTs = session.CreatedAt.Unix()
	}

	nowTs := now.Unix()
	if nowTs <= lastTs {
		return
	}
	bytes := (nowTs - lastTs) * session.MaxBitrateBps / 8
	sourceID, _ := strconv.ParseInt(session.ID, 10, 64)

	if bytes > 0 {
		ok, _ := b.Deduct(dock.UserID, bytes, "live", sourceID)
		if !ok {
			if _, busiErr := DefaultLiveService.stopForBilling(session.DockID, session.ID); busiErr != nil {
				logger.ERROR("直播余额不足停止推流失败", busiErr)
			}
			logger.WARN("直播余额耗尽，停止推流:", session.DockID)
		}
	}
	_ = common.SetValue(lastKey, nowTs)
}

// flushBalanceSnapshot 余额快照刷新（定时任务，每 30min）：Redis 权威余额回写 MySQL
func (b *BillingService) flushBalanceSnapshot() {
	keys, err := common.GetKeysWithPrefix(cache.TrafficKeyPrefix)
	if err != nil {
		logger.ERROR("扫描流量余额 key 失败", err)
		return
	}
	for _, key := range keys {
		idStr := strings.TrimPrefix(key, cache.TrafficKeyPrefix)
		userID, err := strconv.ParseInt(idStr, 10, 64)
		if err != nil {
			continue
		}
		bal, err := common.GetInt64(key)
		if err != nil {
			continue
		}
		if err := common.DB.Model(&model.User{}).Where("id = ?", userID).
			UpdateColumn("traffic_balance", bal).Error; err != nil {
			logger.ERROR("回写余额快照失败", err)
		}
	}
}

// syncSimUsage SIM 卡用量同步（定时任务，每 1h）：运营商查询回填 + 用量快照 + 阈值告警
func (b *BillingService) syncSimUsage() {
	var cards []model.SimCard
	if err := common.DB.Where("status = ?", "active").Find(&cards).Error; err != nil {
		logger.ERROR("扫描 SIM 卡失败", err)
		return
	}
	now := time.Now()
	for i := range cards {
		b.syncSimCard(&cards[i], now)
	}
}

func (b *BillingService) syncSimCard(card *model.SimCard, now time.Time) {
	if carrier == nil {
		logger.INFO("SIM 运营商通道未接入:", card.Iccid)
		return
	}
	usedGb, carrierStatus, err := carrier.QueryUsage(card.Iccid)
	if err != nil {
		logger.WARN("查询 SIM 用量失败:", card.Iccid, err)
		return
	}

	updates := map[string]any{
		"used_gb":        usedGb,
		"carrier_status": carrierStatus,
		"last_sync_at":   now,
	}
	if carrierStatus == "cancelled" {
		updates["status"] = "expired"
	}
	if err := common.DB.Model(&model.SimCard{}).Where("id = ?", card.ID).Updates(updates).Error; err != nil {
		logger.ERROR("回填 SIM 用量失败", err)
	}

	remainGb := float64(card.PlanGb) - usedGb
	record := &model.SimUsageRecord{
		ID:            mustID(),
		SimCardID:     card.ID,
		PlanGb:        card.PlanGb,
		UsedGb:        usedGb,
		RemainGb:      remainGb,
		CarrierStatus: carrierStatus,
		SyncedAt:      now,
	}
	if err := common.DB.Create(record).Error; err != nil {
		logger.ERROR("写入 SIM 用量快照失败", err)
	}

	if remainGb < float64(card.PlanGb)*0.1 {
		logger.WARN("SIM 卡流量即将耗尽:", card.Iccid, "剩余", remainGb, "GB")
	}
	if carrierStatus == "suspended" || carrierStatus == "arrears" {
		logger.WARN("SIM 卡运营商状态异常:", card.Iccid, carrierStatus)
	}
}