package service

import (
	"errors"
	"sync"
	"sync/atomic"
	"testing"
	"time"

	"github.com/stretchr/testify/assert"
	"go.uber.org/zap"

	"nex/backend/internal/domain"
)

type mockStatsRepo struct {
	records []struct {
		providerID string
		modelName  string
		date       time.Time
		delta      int
	}
	fail bool
	mu   sync.Mutex
}

func (m *mockStatsRepo) Record(providerID, modelName string) error {
	return nil
}

func (m *mockStatsRepo) BatchUpdate(providerID, modelName string, date time.Time, delta int) error {
	m.mu.Lock()
	defer m.mu.Unlock()
	if m.fail {
		return errors.New("db error")
	}
	m.records = append(m.records, struct {
		providerID string
		modelName  string
		date       time.Time
		delta      int
	}{providerID, modelName, date, delta})
	return nil
}

func (m *mockStatsRepo) Query(providerID, modelName string, startDate, endDate *time.Time) ([]domain.UsageStats, error) {
	return nil, nil
}

func TestStatsBuffer_Increment(t *testing.T) {
	logger := zap.NewNop()
	statsRepo := &mockStatsRepo{}
	buffer := NewStatsBuffer(statsRepo, logger)

	buffer.Increment("openai", "gpt-4")
	buffer.Increment("openai", "gpt-4")
	buffer.Increment("openai", "gpt-3.5")

	var count int64
	buffer.counters.Range(func(key, value interface{}) bool {
		counter := value.(*int64)
		count += atomic.LoadInt64(counter)
		return true
	})
	assert.Equal(t, int64(3), count)
}

func TestStatsBuffer_ConcurrentIncrement(t *testing.T) {
	logger := zap.NewNop()
	statsRepo := &mockStatsRepo{}
	buffer := NewStatsBuffer(statsRepo, logger)

	var wg sync.WaitGroup
	for i := 0; i < 100; i++ {
		wg.Add(1)
		go func() {
			defer wg.Done()
			buffer.Increment("openai", "gpt-4")
		}()
	}
	wg.Wait()

	var count int64
	buffer.counters.Range(func(key, value interface{}) bool {
		counter := value.(*int64)
		count = atomic.LoadInt64(counter)
		return true
	})
	assert.Equal(t, int64(100), count)
}

func TestStatsBuffer_LoadOrStore(t *testing.T) {
	logger := zap.NewNop()
	statsRepo := &mockStatsRepo{}
	buffer := NewStatsBuffer(statsRepo, logger)

	var wg sync.WaitGroup
	for i := 0; i < 10; i++ {
		wg.Add(1)
		go func() {
			defer wg.Done()
			buffer.Increment("openai", "gpt-4")
		}()
	}
	wg.Wait()

	var counterCount int
	buffer.counters.Range(func(key, value interface{}) bool {
		counterCount++
		return true
	})
	assert.Equal(t, 1, counterCount)
}

func TestStatsBuffer_FlushByInterval(t *testing.T) {
	logger := zap.NewNop()
	statsRepo := &mockStatsRepo{}
	buffer := NewStatsBuffer(statsRepo, logger,
		WithFlushInterval(100*time.Millisecond))

	buffer.Start()
	defer buffer.Stop()

	buffer.Increment("openai", "gpt-4")
	buffer.Increment("openai", "gpt-4")

	time.Sleep(200 * time.Millisecond)

	statsRepo.mu.Lock()
	assert.GreaterOrEqual(t, len(statsRepo.records), 1)
	statsRepo.mu.Unlock()
}

func TestStatsBuffer_FlushByThreshold(t *testing.T) {
	logger := zap.NewNop()
	statsRepo := &mockStatsRepo{}
	buffer := NewStatsBuffer(statsRepo, logger,
		WithFlushThreshold(10))

	buffer.Start()
	defer buffer.Stop()

	for i := 0; i < 10; i++ {
		buffer.Increment("openai", "gpt-4")
	}

	time.Sleep(50 * time.Millisecond)

	statsRepo.mu.Lock()
	assert.GreaterOrEqual(t, len(statsRepo.records), 1)
	statsRepo.mu.Unlock()
}

func TestStatsBuffer_SwapInt64(t *testing.T) {
	logger := zap.NewNop()
	statsRepo := &mockStatsRepo{}
	buffer := NewStatsBuffer(statsRepo, logger)

	buffer.Increment("openai", "gpt-4")
	buffer.Increment("openai", "gpt-4")

	var beforeCount int64
	buffer.counters.Range(func(key, value interface{}) bool {
		counter := value.(*int64)
		beforeCount = atomic.LoadInt64(counter)
		return true
	})
	assert.Equal(t, int64(2), beforeCount)

	buffer.flush()

	var afterCount int64
	buffer.counters.Range(func(key, value interface{}) bool {
		counter := value.(*int64)
		afterCount = atomic.LoadInt64(counter)
		return true
	})
	assert.Equal(t, int64(0), afterCount)
}

func TestStatsBuffer_FailRetry(t *testing.T) {
	logger := zap.NewNop()
	statsRepo := &mockStatsRepo{fail: true}
	buffer := NewStatsBuffer(statsRepo, logger)

	buffer.Increment("openai", "gpt-4")
	buffer.Increment("openai", "gpt-4")

	buffer.flush()

	var count int64
	buffer.counters.Range(func(key, value interface{}) bool {
		counter := value.(*int64)
		count = atomic.LoadInt64(counter)
		return true
	})
	assert.Equal(t, int64(2), count)
}

func TestStatsBuffer_Stop(t *testing.T) {
	logger := zap.NewNop()
	statsRepo := &mockStatsRepo{}
	buffer := NewStatsBuffer(statsRepo, logger,
		WithFlushInterval(10*time.Second))

	buffer.Start()

	buffer.Increment("openai", "gpt-4")
	buffer.Increment("openai", "gpt-4")

	start := time.Now()
	buffer.Stop()
	elapsed := time.Since(start)

	assert.Less(t, elapsed, 1*time.Second)

	statsRepo.mu.Lock()
	assert.GreaterOrEqual(t, len(statsRepo.records), 1)
	statsRepo.mu.Unlock()
}

func TestStatsBuffer_ConcurrentIncrementAndFlush(t *testing.T) {
	logger := zap.NewNop()
	statsRepo := &mockStatsRepo{}
	buffer := NewStatsBuffer(statsRepo, logger,
		WithFlushInterval(50*time.Millisecond))

	buffer.Start()
	defer buffer.Stop()

	var wg sync.WaitGroup
	for i := 0; i < 100; i++ {
		wg.Add(1)
		go func() {
			defer wg.Done()
			buffer.Increment("openai", "gpt-4")
		}()
	}
	wg.Wait()

	time.Sleep(100 * time.Millisecond)

	statsRepo.mu.Lock()
	totalDelta := 0
	for _, r := range statsRepo.records {
		totalDelta += r.delta
	}
	statsRepo.mu.Unlock()

	assert.Equal(t, 100, totalDelta)
}