// internal/retry/retry_test.go
package retry

import (
	"context"
	"errors"
	"testing"
	"time"
)

func TestDo_Success(t *testing.T) {
	strategy := DefaultStrategy()
	callCount := 0
	
	err := Do(context.Background(), strategy, func() error {
		callCount++
		return nil
	})
	
	if err != nil {
		t.Fatalf("expected no error, got %v", err)
	}
	if callCount != 1 {
		t.Errorf("expected 1 call, got %d", callCount)
	}
}

func TestDo_RetryThenSuccess(t *testing.T) {
	strategy := Strategy{
		MaxRetries: 3,
		BaseDelay:  10 * time.Millisecond,
		MaxDelay:   100 * time.Millisecond,
		Multiplier: 2.0,
		Jitter:     false,
		Retryable:  IsRetryable,
	}
	callCount := 0
	
	err := Do(context.Background(), strategy, func() error {
		callCount++
		if callCount < 3 {
			return errors.New("temporary error")
		}
		return nil
	})
	
	if err != nil {
		t.Fatalf("expected no error, got %v", err)
	}
	if callCount != 3 {
		t.Errorf("expected 3 calls, got %d", callCount)
	}
}

func TestDo_MaxRetriesExceeded(t *testing.T) {
	strategy := Strategy{
		MaxRetries: 2,
		BaseDelay:  5 * time.Millisecond,
		MaxDelay:   50 * time.Millisecond,
		Multiplier: 2.0,
		Jitter:     false,
		Retryable:  IsRetryable,
	}
	callCount := 0
	expectedErr := errors.New("persistent error")
	
	err := Do(context.Background(), strategy, func() error {
		callCount++
		return expectedErr
	})
	
	if err == nil {
		t.Fatal("expected error, got nil")
	}
	if callCount != 3 { // initial + 2 retries
		t.Errorf("expected 3 calls, got %d", callCount)
	}
}

func TestDo_NonRetryableError(t *testing.T) {
	strategy := Strategy{
		MaxRetries: 3,
		BaseDelay:  10 * time.Millisecond,
		MaxDelay:   100 * time.Millisecond,
		Multiplier: 2.0,
		Jitter:     false,
		Retryable:  func(err error) bool { return false }, // 任何错误都不重试
	}
	callCount := 0
	
	err := Do(context.Background(), strategy, func() error {
		callCount++
		return errors.New("non-retryable")
	})
	
	if err == nil {
		t.Fatal("expected error, got nil")
	}
	if callCount != 1 {
		t.Errorf("expected 1 call (no retry), got %d", callCount)
	}
}

func TestDo_ContextCancellation(t *testing.T) {
	strategy := Strategy{
		MaxRetries: 3,
		BaseDelay:  1 * time.Second, // 长延迟确保上下文取消优先
		MaxDelay:   5 * time.Second,
		Multiplier: 2.0,
		Jitter:     false,
		Retryable:  IsRetryable,
	}
	
	ctx, cancel := context.WithTimeout(context.Background(), 50*time.Millisecond)
	defer cancel()
	
	callCount := 0
	err := Do(ctx, strategy, func() error {
		callCount++
		return errors.New("error")
	})
	
	if err == nil {
		t.Fatal("expected error, got nil")
	}
	if callCount < 1 {
		t.Error("expected at least 1 call")
	}
	if !errors.Is(err, context.DeadlineExceeded) && !errors.Is(err, context.Canceled) {
		t.Errorf("expected context error, got %v", err)
	}
}

func TestDoWithResult(t *testing.T) {
	strategy := Strategy{
		MaxRetries: 2,
		BaseDelay:  5 * time.Millisecond,
		MaxDelay:   50 * time.Millisecond,
		Multiplier: 2.0,
		Jitter:     false,
		Retryable:  IsRetryable,
	}
	callCount := 0
	
	result, err := DoWithResult(context.Background(), strategy, func() (string, error) {
		callCount++
		if callCount < 2 {
			return "", errors.New("temp error")
		}
		return "success", nil
	})
	
	if err != nil {
		t.Fatalf("expected no error, got %v", err)
	}
	if result != "success" {
		t.Errorf("expected 'success', got %q", result)
	}
	if callCount != 2 {
		t.Errorf("expected 2 calls, got %d", callCount)
	}
}

func TestDoWithMetrics(t *testing.T) {
	strategy := Strategy{
		MaxRetries: 2,
		BaseDelay:  10 * time.Millisecond,
		MaxDelay:   100 * time.Millisecond,
		Multiplier: 2.0,
		Jitter:     false,
		Retryable:  IsRetryable,
	}
	
	// 成功场景
	m, err := DoWithMetrics(context.Background(), strategy, func() error {
		return nil
	})
	if err != nil {
		t.Fatalf("expected no error, got %v", err)
	}
	if !m.Success {
		t.Error("expected Success=true")
	}
	if m.Attempts != 1 {
		t.Errorf("expected 1 attempt, got %d", m.Attempts)
	}
	
	// 失败场景
	m2, err := DoWithMetrics(context.Background(), strategy, func() error {
		return errors.New("always fails")
	})
	if err == nil {
		t.Fatal("expected error, got nil")
	}
	if m2.Success {
		t.Error("expected Success=false")
	}
	if m2.Attempts != 3 {
		t.Errorf("expected 3 attempts, got %d", m2.Attempts)
	}
}

func TestCalculateDelay(t *testing.T) {
	strategy := Strategy{
		BaseDelay:  1 * time.Second,
		MaxDelay:   10 * time.Second,
		Multiplier: 2.0,
		Jitter:     false,
	}
	
	tests := []struct {
		attempt int
		min     time.Duration
		max     time.Duration
	}{
		{0, 1 * time.Second, 1 * time.Second},
		{1, 2 * time.Second, 2 * time.Second},
		{2, 4 * time.Second, 4 * time.Second},
		{3, 8 * time.Second, 8 * time.Second},
		{4, 10 * time.Second, 10 * time.Second}, // 达到上限
	}
	
	for _, tt := range tests {
		delay := calculateDelay(strategy, tt.attempt)
		if delay < tt.min || delay > tt.max {
			t.Errorf("attempt %d: delay=%v, want [%v, %v]", tt.attempt, delay, tt.min, tt.max)
		}
	}
}

func BenchmarkDo(b *testing.B) {
	strategy := Strategy{
		MaxRetries: 0,
		BaseDelay:  0,
		MaxDelay:   0,
		Multiplier: 0,
		Jitter:     false,
	}
	
	for i := 0; i < b.N; i++ {
		_ = Do(context.Background(), strategy, func() error {
			return nil
		})
	}
}