// Filename: internal/service/analytics_service.go

package service

import (
	"encoding/json"
	"fmt"
	"gemini-balancer/internal/db/dialect"
	"gemini-balancer/internal/models"
	"gemini-balancer/internal/store"
	"strconv"
	"strings"
	"sync"
	"time"

	"github.com/sirupsen/logrus"
	"gorm.io/gorm"
)

const (
	flushLoopInterval = 1 * time.Minute
)

type AnalyticsServiceLogger struct{ *logrus.Entry }

type AnalyticsService struct {
	db       *gorm.DB
	store    store.Store
	logger   *logrus.Entry
	stopChan chan struct{}
	wg       sync.WaitGroup
	dialect  dialect.DialectAdapter
}

func NewAnalyticsService(db *gorm.DB, s store.Store, logger *logrus.Logger, d dialect.DialectAdapter) *AnalyticsService {
	return &AnalyticsService{
		db:       db,
		store:    s,
		logger:   logger.WithField("component", "Analytics📊"),
		stopChan: make(chan struct{}),
		dialect:  d,
	}
}

func (s *AnalyticsService) Start() {
	s.wg.Add(2) // 2 (flushLoop, eventListener)
	go s.flushLoop()
	go s.eventListener()
	s.logger.Info("AnalyticsService (Command Side) started.")
}

func (s *AnalyticsService) Stop() {
	close(s.stopChan)
	s.wg.Wait()
	s.logger.Info("AnalyticsService stopped. Performing final data flush...")
	s.flushToDB() // 停止前刷盘
	s.logger.Info("AnalyticsService final data flush completed.")
}

func (s *AnalyticsService) eventListener() {
	defer s.wg.Done()
	sub, err := s.store.Subscribe(models.TopicRequestFinished)
	if err != nil {
		s.logger.Fatalf("Failed to subscribe to topic %s: %v", models.TopicRequestFinished, err)
		return
	}
	defer sub.Close()
	s.logger.Info("AnalyticsService subscribed to request events.")

	for {
		select {
		case msg := <-sub.Channel():
			var event models.RequestFinishedEvent
			if err := json.Unmarshal(msg.Payload, &event); err != nil {
				s.logger.Errorf("Failed to unmarshal analytics event: %v", err)
				continue
			}
			s.handleAnalyticsEvent(&event)
		case <-s.stopChan:
			s.logger.Info("AnalyticsService stopping event listener.")
			return
		}
	}
}

func (s *AnalyticsService) handleAnalyticsEvent(event *models.RequestFinishedEvent) {
	if event.RequestLog.GroupID == nil {
		return
	}
	key := fmt.Sprintf("analytics:hourly:%s", time.Now().UTC().Format("2006-01-02T15"))
	fieldPrefix := fmt.Sprintf("%d:%s", *event.RequestLog.GroupID, event.RequestLog.ModelName)
	pipe := s.store.Pipeline()
	pipe.HIncrBy(key, fieldPrefix+":requests", 1)
	if event.RequestLog.IsSuccess {
		pipe.HIncrBy(key, fieldPrefix+":success", 1)
	}
	if event.RequestLog.PromptTokens > 0 {
		pipe.HIncrBy(key, fieldPrefix+":prompt", int64(event.RequestLog.PromptTokens))
	}
	if event.RequestLog.CompletionTokens > 0 {
		pipe.HIncrBy(key, fieldPrefix+":completion", int64(event.RequestLog.CompletionTokens))
	}
	if err := pipe.Exec(); err != nil {
		s.logger.Warnf("[%s] Failed to record analytics event to store for group %d: %v", event.CorrelationID, *event.RequestLog.GroupID, err)
	}
}

func (s *AnalyticsService) flushLoop() {
	defer s.wg.Done()
	ticker := time.NewTicker(flushLoopInterval)
	defer ticker.Stop()
	for {
		select {
		case <-ticker.C:
			s.flushToDB()
		case <-s.stopChan:
			return
		}
	}
}

func (s *AnalyticsService) flushToDB() {
	now := time.Now().UTC()
	keysToFlush := []string{
		fmt.Sprintf("analytics:hourly:%s", now.Add(-1*time.Hour).Format("2006-01-02T15")),
		fmt.Sprintf("analytics:hourly:%s", now.Format("2006-01-02T15")),
	}

	for _, key := range keysToFlush {
		data, err := s.store.HGetAll(key)
		if err != nil || len(data) == 0 {
			continue
		}

		statsToFlush, parsedFields := s.parseStatsFromHash(now.Truncate(time.Hour), data)

		if len(statsToFlush) > 0 {
			upsertClause := s.dialect.OnConflictUpdateAll(
				[]string{"time", "group_id", "model_name"},                                       // conflict columns
				[]string{"request_count", "success_count", "prompt_tokens", "completion_tokens"}, // update columns
			)
			err := s.db.Clauses(upsertClause).Create(&statsToFlush).Error
			if err != nil {
				s.logger.Errorf("Failed to flush analytics data for key %s: %v", key, err)
			} else {
				s.logger.Infof("Successfully flushed %d records from key %s.", len(statsToFlush), key)
				_ = s.store.HDel(key, parsedFields...)
			}
		}
	}
}

func (s *AnalyticsService) parseStatsFromHash(t time.Time, data map[string]string) ([]models.StatsHourly, []string) {
	tempAggregator := make(map[string]*models.StatsHourly)
	var parsedFields []string
	for field, valueStr := range data {
		parts := strings.Split(field, ":")
		if len(parts) != 3 {
			continue
		}
		groupIDStr, modelName, counterType := parts[0], parts[1], parts[2]

		aggKey := groupIDStr + ":" + modelName
		if _, ok := tempAggregator[aggKey]; !ok {
			gid, err := strconv.Atoi(groupIDStr)
			if err != nil {
				continue
			}
			tempAggregator[aggKey] = &models.StatsHourly{
				Time:      t,
				GroupID:   uint(gid),
				ModelName: modelName,
			}
		}
		val, _ := strconv.ParseInt(valueStr, 10, 64)
		switch counterType {
		case "requests":
			tempAggregator[aggKey].RequestCount = val
		case "success":
			tempAggregator[aggKey].SuccessCount = val
		case "prompt":
			tempAggregator[aggKey].PromptTokens = val
		case "completion":
			tempAggregator[aggKey].CompletionTokens = val
		}
		parsedFields = append(parsedFields, field)
	}
	var result []models.StatsHourly
	for _, stats := range tempAggregator {
		if stats.RequestCount > 0 {
			result = append(result, *stats)
		}
	}
	return result, parsedFields
}