package service

import (
	"strings"
	"sync"
	"sync/atomic"
	"time"

	"go.uber.org/zap"

	"nex/backend/internal/repository"
)

type StatsBuffer struct {
	counters sync.Map

	flushInterval  time.Duration
	flushThreshold int
	totalCount     atomic.Int64

	statsRepo repository.StatsRepository
	logger    *zap.Logger

	stopCh chan struct{}
	doneCh chan struct{}
}

type StatsBufferOption func(*StatsBuffer)

func WithFlushInterval(d time.Duration) StatsBufferOption {
	return func(b *StatsBuffer) {
		b.flushInterval = d
	}
}

func WithFlushThreshold(threshold int) StatsBufferOption {
	return func(b *StatsBuffer) {
		b.flushThreshold = threshold
	}
}

func NewStatsBuffer(
	statsRepo repository.StatsRepository,
	logger *zap.Logger,
	opts ...StatsBufferOption,
) *StatsBuffer {
	b := &StatsBuffer{
		statsRepo:      statsRepo,
		logger:         logger,
		flushInterval:  5 * time.Second,
		flushThreshold: 100,
		stopCh:         make(chan struct{}),
		doneCh:         make(chan struct{}),
	}

	for _, opt := range opts {
		opt(b)
	}

	return b
}

func (b *StatsBuffer) Increment(providerID, modelName string) {
	today := time.Now().Format("2006-01-02")
	key := providerID + "/" + modelName + "/" + today

	var counter *int64
	if v, ok := b.counters.Load(key); ok {
		counter = v.(*int64)
	} else {
		val := int64(0)
		counter = &val
		actual, loaded := b.counters.LoadOrStore(key, counter)
		if loaded {
			counter = actual.(*int64)
		}
	}

	atomic.AddInt64(counter, 1)

	if b.totalCount.Add(1) >= int64(b.flushThreshold) {
		go b.flush()
	}
}

func (b *StatsBuffer) Start() {
	go func() {
		ticker := time.NewTicker(b.flushInterval)
		defer ticker.Stop()

		for {
			select {
			case <-ticker.C:
				b.flush()
			case <-b.stopCh:
				b.flush()
				close(b.doneCh)
				return
			}
		}
	}()
}

func (b *StatsBuffer) Stop() {
	close(b.stopCh)
	<-b.doneCh
}

func (b *StatsBuffer) flush() {
	type statEntry struct {
		providerID string
		modelName  string
		date       string
		count      int64
	}

	var entries []statEntry
	b.counters.Range(func(key, value interface{}) bool {
		keyStr := key.(string)
		parts := strings.Split(keyStr, "/")
		if len(parts) != 3 {
			return true
		}

		counter := value.(*int64)
		count := atomic.SwapInt64(counter, 0)

		if count > 0 {
			entries = append(entries, statEntry{
				providerID: parts[0],
				modelName:  parts[1],
				date:       parts[2],
				count:      count,
			})
		}
		return true
	})

	if len(entries) == 0 {
		return
	}

	success := 0
	for _, entry := range entries {
		date, _ := time.Parse("2006-01-02", entry.date)
		err := b.statsRepo.BatchUpdate(entry.providerID, entry.modelName, date, int(entry.count))
		if err != nil {
			b.logger.Error("批量更新统计失败",
				zap.String("provider_id", entry.providerID),
				zap.String("model_name", entry.modelName),
				zap.Int64("count", entry.count),
				zap.Error(err))

			key := entry.providerID + "/" + entry.modelName + "/" + entry.date
			if v, ok := b.counters.Load(key); ok {
				counter := v.(*int64)
				atomic.AddInt64(counter, entry.count)
			}
		} else {
			success++
		}
	}

	b.totalCount.Store(0)
	b.logger.Debug("统计刷新完成",
		zap.Int("total", len(entries)),
		zap.Int("success", success),
		zap.Int("failed", len(entries)-success))
}