package server

import (
	"encoding/json"
	"fmt"
	"strings"
	"time"

	"github.com/gin-gonic/gin"
	"github.com/perfect-panel/server/internal/model/group"
	"github.com/perfect-panel/server/internal/model/node"
	"github.com/perfect-panel/server/internal/model/subscribe"
	"github.com/perfect-panel/server/internal/model/user"

	"github.com/perfect-panel/server/internal/svc"
	"github.com/perfect-panel/server/internal/types"
	"github.com/perfect-panel/server/pkg/logger"
	"github.com/perfect-panel/server/pkg/speedlimit"
	"github.com/perfect-panel/server/pkg/tool"
	"github.com/perfect-panel/server/pkg/uuidx"
	"github.com/perfect-panel/server/pkg/xerr"
	"github.com/redis/go-redis/v9"
)

type GetServerUserListLogic struct {
	logger.Logger
	ctx    *gin.Context
	svcCtx *svc.ServiceContext
}

type serverUserListPerfStats struct {
	serverID                int64
	protocol                string
	cacheHit                bool
	nodesCount              int
	subsCount               int
	usersCount              int
	speedLimitZeroCount     int
	speedLimitPositiveCount int
	trafficCalcMS           int64
	startedAt               time.Time
}

type serverUserSpeedLimitCandidate struct {
	userID          int64
	userSubscribeID int64
	baseSpeed       int64
	trafficLimit    string
}

type serverUserTrafficWindow struct {
	statType  string
	statValue int64
	start     time.Time
	end       time.Time
}

type serverUserTrafficUsageKey struct {
	userID          int64
	userSubscribeID int64
	statType        string
	statValue       int64
}

type serverUserTrafficUsage struct {
	userID          int64
	userSubscribeID int64
	usedGB          float64
}

// NewGetServerUserListLogic Get user list
func NewGetServerUserListLogic(ctx *gin.Context, svcCtx *svc.ServiceContext) *GetServerUserListLogic {
	return &GetServerUserListLogic{
		Logger: logger.WithContext(ctx.Request.Context()),
		ctx:    ctx,
		svcCtx: svcCtx,
	}
}

func (l *GetServerUserListLogic) GetServerUserList(req *types.GetServerUserListRequest) (resp *types.GetServerUserListResponse, err error) {
	startedAt := time.Now()
	protocolRequest := normalizeServerUserListProtocol(req.Protocol)
	stats := serverUserListPerfStats{
		serverID:  req.ServerId,
		protocol:  protocolRequest,
		startedAt: startedAt,
		cacheHit:  false,
	}

	cacheKey := fmt.Sprintf("%s%d:%s", node.ServerUserListCacheKey, req.ServerId, protocolRequest)
	cache, err := l.svcCtx.Redis.Get(l.ctx, cacheKey).Result()
	if err != nil && err != redis.Nil {
		l.Errorw("[ServerUserListCacheKey] redis get error", logger.Field("error", err.Error()))
	}
	if cache != "" {
		stats.cacheHit = true
		etag := tool.GenerateETag([]byte(cache))
		resp = &types.GetServerUserListResponse{}
		//  Check If-None-Match header
		if match := l.ctx.GetHeader("If-None-Match"); match == etag {
			l.logServerUserListPerf(stats)
			return nil, xerr.StatusNotModified
		}
		l.ctx.Header("ETag", etag)
		err = json.Unmarshal([]byte(cache), resp)
		if err != nil {
			l.Errorw("[ServerUserListCacheKey] json unmarshal error", logger.Field("error", err.Error()))
			return nil, err
		}
		stats.usersCount = len(resp.Users)
		stats.recordSpeedLimits(resp.Users)
		l.logServerUserListPerf(stats)
		return resp, nil
	}
	server, err := l.svcCtx.NodeModel.FindOneServer(l.ctx, req.ServerId)
	if err != nil {
		return nil, err
	}

	// 查询该服务器上该协议的所有节点（包括属于节点组的节点）
	_, nodes, err := l.svcCtx.NodeModel.FilterNodeList(l.ctx, &node.FilterNodeParams{
		Page:     1,
		Size:     1000,
		ServerId: []int64{server.Id},
		Protocol: protocolRequest,
	})
	if err != nil {
		l.Errorw("FilterNodeList error", logger.Field("error", err.Error()))
		return nil, err
	}
	stats.nodesCount = len(nodes)

	if len(nodes) == 0 {
		l.Errorw("[ServerUserList] fallback: no nodes matched server+protocol, returning placeholder without cache",
			logger.Field("server_id", req.ServerId),
			logger.Field("protocol", req.Protocol),
		)
		stats.usersCount = 1
		stats.speedLimitZeroCount = 1
		l.logServerUserListPerf(stats)
		return &types.GetServerUserListResponse{
			Users: []types.ServerUser{
				{
					Id:   1,
					UUID: uuidx.NewUUID().String(),
				},
			},
		}, nil
	}

	// 收集所有唯一的节点组 ID
	nodeGroupMap := make(map[int64]bool) // nodeGroupId -> true
	var nodeIds []int64
	var nodeTags []string

	for _, n := range nodes {
		nodeIds = append(nodeIds, n.Id)
		if n.Tags != "" {
			nodeTags = append(nodeTags, strings.Split(n.Tags, ",")...)
		}
		// 收集节点组 ID
		if len(n.NodeGroupIds) > 0 {
			for _, gid := range n.NodeGroupIds {
				if gid > 0 {
					nodeGroupMap[gid] = true
				}
			}
		}
	}

	// 获取所有节点组 ID
	nodeGroupIds := make([]int64, 0, len(nodeGroupMap))
	for gid := range nodeGroupMap {
		nodeGroupIds = append(nodeGroupIds, gid)
	}

	// 查询订阅：
	// 1. 如果有节点组，查询匹配这些节点组的订阅
	// 2. 如果没有节点组，查询使用节点 ID 或 tags 的订阅
	var subs []*subscribe.Subscribe
	if len(nodeGroupIds) > 0 {
		// 节点组模式：查询 node_group_id 或 node_group_ids 匹配的订阅
		_, subs, err = l.svcCtx.SubscribeModel.FilterListByNodeGroups(l.ctx, &subscribe.FilterByNodeGroupsParams{
			Page:         1,
			Size:         9999,
			NodeGroupIds: nodeGroupIds,
		})
		if err != nil {
			l.Errorw("FilterListByNodeGroups error", logger.Field("error", err.Error()))
			return nil, err
		}
	} else {
		// 传统模式：查询匹配节点 ID 或 tags 的订阅
		nodeTags = tool.RemoveDuplicateElements(nodeTags...)
		_, subs, err = l.svcCtx.SubscribeModel.FilterList(l.ctx, &subscribe.FilterParams{
			Page: 1,
			Size: 9999,
			Node: nodeIds,
			Tags: nodeTags,
		})
		if err != nil {
			l.Errorw("FilterList error", logger.Field("error", err.Error()))
			return nil, err
		}
	}

	if len(subs) == 0 {
		l.Errorw("[ServerUserList] fallback: no subscriptions matched node group/tags, returning placeholder without cache",
			logger.Field("server_id", req.ServerId),
			logger.Field("protocol", req.Protocol),
		)
		stats.usersCount = 1
		stats.speedLimitZeroCount = 1
		l.logServerUserListPerf(stats)
		return &types.GetServerUserListResponse{
			Users: []types.ServerUser{
				{
					Id:   1,
					UUID: uuidx.NewUUID().String(),
				},
			},
		}, nil
	}
	stats.subsCount = len(subs)
	users := make([]types.ServerUser, 0)
	speedCandidates := make(map[int64]serverUserSpeedLimitCandidate)
	for _, sub := range subs {
		data, err := l.svcCtx.UserModel.FindUsersSubscribeBySubscribeId(l.ctx, sub.Id)
		if err != nil {
			return nil, err
		}
		for _, datum := range data {
			if !l.shouldIncludeServerUser(datum, nodeGroupIds) {
				continue
			}

			baseSpeed, trafficLimit := serverUserSpeedLimitInputs(sub, datum)
			speedCandidates[datum.Id] = serverUserSpeedLimitCandidate{
				userID:          datum.UserId,
				userSubscribeID: datum.Id,
				baseSpeed:       baseSpeed,
				trafficLimit:    trafficLimit,
			}
			users = append(users, types.ServerUser{
				Id:          datum.Id,
				UUID:        datum.UUID,
				SpeedLimit:  baseSpeed,
				DeviceLimit: sub.DeviceLimit,
			})
		}
	}
	trafficCalcStartedAt := time.Now()
	speedLimits := l.calculateServerUserSpeedLimits(speedCandidates)
	stats.trafficCalcMS = time.Since(trafficCalcStartedAt).Milliseconds()
	for i := range users {
		if speedLimit, ok := speedLimits[users[i].Id]; ok {
			users[i].SpeedLimit = speedLimit
		}
	}

	// 处理过期订阅用户：如果当前节点属于过期节点组，添加符合条件的过期用户
	if len(nodeGroupIds) > 0 {
		expiredUsers, expiredSpeedLimit := l.getExpiredUsers(nodeGroupIds)
		for i := range expiredUsers {
			if expiredSpeedLimit > 0 {
				expiredUsers[i].SpeedLimit = expiredSpeedLimit
			}
		}
		users = append(users, expiredUsers...)
	}

	if len(users) == 0 {
		l.Errorw("[ServerUserList] fallback: matched subs returned zero eligible users, returning placeholder without cache",
			logger.Field("server_id", req.ServerId),
			logger.Field("protocol", req.Protocol),
		)
		stats.usersCount = 1
		stats.speedLimitZeroCount = 1
		l.logServerUserListPerf(stats)
		return &types.GetServerUserListResponse{
			Users: []types.ServerUser{
				{
					Id:   1,
					UUID: uuidx.NewUUID().String(),
				},
			},
		}, nil
	}
	resp = &types.GetServerUserListResponse{
		Users: users,
	}
	stats.usersCount = len(users)
	stats.recordSpeedLimits(users)
	val, _ := json.Marshal(resp)
	etag := tool.GenerateETag(val)
	l.ctx.Header("ETag", etag)
	err = l.svcCtx.Redis.Set(l.ctx, cacheKey, string(val), l.serverUserListCacheTTL()).Err()
	if err != nil {
		l.Errorw("[ServerUserListCacheKey] redis set error", logger.Field("error", err.Error()))
	}
	//  Check If-None-Match header
	if match := l.ctx.GetHeader("If-None-Match"); match == etag {
		l.logServerUserListPerf(stats)
		return nil, xerr.StatusNotModified
	}
	l.logServerUserListPerf(stats)
	return resp, nil
}

// normalizeServerUserListProtocol 将客户端可能携带的 hysteria2 兼容字段映射回
// DB 中存储的规范名 "hysteria"。其它协议原样返回。
// 缓存 key 与 FilterNodeList 查询都必须用归一化后的值，
// 否则 hysteria2 永远查不到节点，永远走兜底。
func normalizeServerUserListProtocol(protocol string) string {
	if protocol == Hysteria2 {
		return Hysteria
	}
	return protocol
}

func (l *GetServerUserListLogic) serverUserListCacheTTL() time.Duration {
	pullInterval := l.svcCtx.Config.Node.NodePullInterval
	if pullInterval <= 0 {
		pullInterval = 60
	}
	ttl := time.Duration(pullInterval*2) * time.Second
	if ttl < time.Minute {
		return time.Minute
	}
	return ttl
}

func (l *GetServerUserListLogic) shouldIncludeServerUser(userSub *user.Subscribe, serverNodeGroupIds []int64) bool {
	if userSub == nil {
		return false
	}

	if userSub.ExpireTime.Unix() == 0 || userSub.ExpireTime.After(time.Now()) {
		return true
	}

	return l.canUseExpiredNodeGroup(userSub, serverNodeGroupIds)
}

func (l *GetServerUserListLogic) getExpiredUsers(serverNodeGroupIds []int64) ([]types.ServerUser, int64) {
	var expiredGroup group.NodeGroup
	if err := l.svcCtx.DB.Where("is_expired_group = ?", true).First(&expiredGroup).Error; err != nil {
		return nil, 0
	}

	if !tool.Contains(serverNodeGroupIds, expiredGroup.Id) {
		return nil, 0
	}

	var expiredSubs []*user.Subscribe
	if err := l.svcCtx.DB.Where("status = ?", 3).Find(&expiredSubs).Error; err != nil {
		l.Errorw("query expired subscriptions failed", logger.Field("error", err.Error()))
		return nil, 0
	}

	users := make([]types.ServerUser, 0)
	seen := make(map[int64]bool)
	for _, userSub := range expiredSubs {
		if !l.checkExpiredUserEligibility(userSub, &expiredGroup) {
			continue
		}
		if seen[userSub.Id] {
			continue
		}
		seen[userSub.Id] = true
		users = append(users, types.ServerUser{
			Id:   userSub.Id,
			UUID: userSub.UUID,
		})
	}

	return users, int64(expiredGroup.SpeedLimit)
}

func (l *GetServerUserListLogic) checkExpiredUserEligibility(userSub *user.Subscribe, expiredGroup *group.NodeGroup) bool {
	expiredDays := int(time.Since(userSub.ExpireTime).Hours() / 24)
	if expiredDays > expiredGroup.ExpiredDaysLimit {
		return false
	}

	if expiredGroup.MaxTrafficGBExpired != nil && *expiredGroup.MaxTrafficGBExpired > 0 {
		usedTrafficGB := (userSub.ExpiredDownload + userSub.ExpiredUpload) / (1024 * 1024 * 1024)
		if usedTrafficGB >= *expiredGroup.MaxTrafficGBExpired {
			return false
		}
	}

	return true
}

func (l *GetServerUserListLogic) canUseExpiredNodeGroup(userSub *user.Subscribe, serverNodeGroupIds []int64) bool {
	var expiredGroup group.NodeGroup
	if err := l.svcCtx.DB.Where("is_expired_group = ?", true).First(&expiredGroup).Error; err != nil {
		return false
	}

	if !tool.Contains(serverNodeGroupIds, expiredGroup.Id) {
		return false
	}

	expiredDays := int(time.Since(userSub.ExpireTime).Hours() / 24)
	if expiredDays > expiredGroup.ExpiredDaysLimit {
		return false
	}

	if expiredGroup.MaxTrafficGBExpired != nil && *expiredGroup.MaxTrafficGBExpired > 0 {
		usedTrafficGB := (userSub.ExpiredDownload + userSub.ExpiredUpload) / (1024 * 1024 * 1024)
		if usedTrafficGB >= *expiredGroup.MaxTrafficGBExpired {
			return false
		}
	}

	return true
}

func serverUserSpeedLimitInputs(sub *subscribe.Subscribe, userSub *user.Subscribe) (int64, string) {
	baseSpeed := sub.SpeedLimit
	if userSub.SpeedLimit > 0 {
		baseSpeed = userSub.SpeedLimit
	}

	trafficLimit := sub.TrafficLimit
	if userSub.TrafficLimit != nil && *userSub.TrafficLimit != "" {
		trafficLimit = *userSub.TrafficLimit
	}

	return baseSpeed, trafficLimit
}

func (l *GetServerUserListLogic) calculateServerUserSpeedLimits(candidates map[int64]serverUserSpeedLimitCandidate) map[int64]int64 {
	speedLimits := make(map[int64]int64, len(candidates))
	rulesByUserSubscribeID := make(map[int64][]speedlimit.TrafficLimitRule)
	windowByKey := make(map[string]serverUserTrafficWindow)
	now := time.Now()

	for userSubscribeID, candidate := range candidates {
		speedLimits[userSubscribeID] = candidate.baseSpeed
		if candidate.trafficLimit == "" {
			continue
		}

		var rules []speedlimit.TrafficLimitRule
		if err := json.Unmarshal([]byte(candidate.trafficLimit), &rules); err != nil || len(rules) == 0 {
			continue
		}
		rulesByUserSubscribeID[userSubscribeID] = rules
		for _, rule := range rules {
			window, ok := serverUserTrafficRuleWindow(rule, now)
			if !ok {
				continue
			}
			windowByKey[serverUserTrafficWindowKey(rule.StatType, rule.StatValue)] = window
		}
	}

	if len(rulesByUserSubscribeID) == 0 || len(windowByKey) == 0 {
		return speedLimits
	}

	usageByKey := make(map[serverUserTrafficUsageKey]float64)
	for _, window := range windowByKey {
		trafficUsage, err := l.queryServerUserTrafficUsage(candidates, window)
		if err != nil {
			l.Errorw("[ServerUserList] batch traffic usage query failed",
				logger.Field("error", err.Error()),
				logger.Field("stat_type", window.statType),
				logger.Field("stat_value", window.statValue),
			)
			continue
		}
		for _, usage := range trafficUsage {
			usageByKey[serverUserTrafficUsageKey{
				userID:          usage.userID,
				userSubscribeID: usage.userSubscribeID,
				statType:        window.statType,
				statValue:       window.statValue,
			}] = usage.usedGB
		}
	}

	for userSubscribeID, rules := range rulesByUserSubscribeID {
		candidate := candidates[userSubscribeID]
		for _, rule := range rules {
			if rule.SpeedLimit <= 0 {
				continue
			}
			if _, ok := serverUserTrafficRuleWindow(rule, now); !ok {
				continue
			}
			usedGB := usageByKey[serverUserTrafficUsageKey{
				userID:          candidate.userID,
				userSubscribeID: candidate.userSubscribeID,
				statType:        rule.StatType,
				statValue:       rule.StatValue,
			}]
			if usedGB < float64(rule.TrafficUsage) {
				continue
			}
			current := speedLimits[userSubscribeID]
			if current == 0 || rule.SpeedLimit < current {
				speedLimits[userSubscribeID] = rule.SpeedLimit
			}
		}
	}

	return speedLimits
}

func (l *GetServerUserListLogic) queryServerUserTrafficUsage(
	candidates map[int64]serverUserSpeedLimitCandidate,
	window serverUserTrafficWindow,
) ([]serverUserTrafficUsage, error) {
	userSubscribeIDs := make([]int64, 0, len(candidates))
	for userSubscribeID := range candidates {
		userSubscribeIDs = append(userSubscribeIDs, userSubscribeID)
	}

	var rows []struct {
		UserID          int64
		UserSubscribeID int64
		Upload          int64
		Download        int64
	}
	err := l.svcCtx.DB.WithContext(l.ctx.Request.Context()).
		Table("traffic_log").
		Select("user_id, subscribe_id AS user_subscribe_id, COALESCE(SUM(upload), 0) AS upload, COALESCE(SUM(download), 0) AS download").
		Where("subscribe_id IN ? AND timestamp >= ? AND timestamp < ?", userSubscribeIDs, window.start, window.end).
		Group("user_id, subscribe_id").
		Scan(&rows).Error
	if err != nil {
		return nil, err
	}

	trafficUsage := make([]serverUserTrafficUsage, 0, len(rows))
	for _, row := range rows {
		trafficUsage = append(trafficUsage, serverUserTrafficUsage{
			userID:          row.UserID,
			userSubscribeID: row.UserSubscribeID,
			usedGB:          float64(row.Upload+row.Download) / (1024 * 1024 * 1024),
		})
	}
	return trafficUsage, nil
}

func serverUserTrafficRuleWindow(rule speedlimit.TrafficLimitRule, now time.Time) (serverUserTrafficWindow, bool) {
	if rule.StatValue <= 0 {
		return serverUserTrafficWindow{}, false
	}

	window := serverUserTrafficWindow{
		statType:  rule.StatType,
		statValue: rule.StatValue,
		end:       now,
	}
	switch rule.StatType {
	case "hour":
		window.start = now.Add(-time.Duration(rule.StatValue) * time.Hour)
	case "day":
		window.start = now.AddDate(0, 0, -int(rule.StatValue))
	default:
		return serverUserTrafficWindow{}, false
	}
	return window, true
}

func serverUserTrafficWindowKey(statType string, statValue int64) string {
	return fmt.Sprintf("%s:%d", statType, statValue)
}

func (s *serverUserListPerfStats) recordSpeedLimits(users []types.ServerUser) {
	for _, user := range users {
		if user.SpeedLimit > 0 {
			s.speedLimitPositiveCount++
			continue
		}
		s.speedLimitZeroCount++
	}
}

func (l *GetServerUserListLogic) logServerUserListPerf(stats serverUserListPerfStats) {
	l.Infow("[ServerUserList] performance",
		logger.Field("server_id", stats.serverID),
		logger.Field("protocol", stats.protocol),
		logger.Field("cache_hit", stats.cacheHit),
		logger.Field("nodes_count", stats.nodesCount),
		logger.Field("subs_count", stats.subsCount),
		logger.Field("users_count", stats.usersCount),
		logger.Field("speed_limit_0_count", stats.speedLimitZeroCount),
		logger.Field("speed_limit_positive_count", stats.speedLimitPositiveCount),
		logger.Field("traffic_calc_ms", stats.trafficCalcMS),
		logger.Field("total_ms", time.Since(stats.startedAt).Milliseconds()),
	)
}