package llm

import (
	"context"
	"errors"
	"log/slog"
	"sync"
	"sync/atomic"
	"testing"
	"time"

	"gitea.stevedudenhoeffer.com/steve/go-llm/v2/provider"
)

func TestWithRetry_Success(t *testing.T) {
	mp := newMockProvider(provider.Response{Text: "ok"})
	model := newMockModel(mp).WithMiddleware(
		WithRetry(3, func(attempt int) time.Duration { return time.Millisecond }),
	)

	resp, err := model.Complete(context.Background(), []Message{UserMessage("test")})
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	if resp.Text != "ok" {
		t.Errorf("expected 'ok', got %q", resp.Text)
	}
	if len(mp.Requests) != 1 {
		t.Errorf("expected 1 request (no retries needed), got %d", len(mp.Requests))
	}
}

func TestWithRetry_EventualSuccess(t *testing.T) {
	var callCount int32
	mp := newMockProviderFunc(func(ctx context.Context, req provider.Request) (provider.Response, error) {
		n := atomic.AddInt32(&callCount, 1)
		if n <= 2 {
			return provider.Response{}, errors.New("transient error")
		}
		return provider.Response{Text: "success"}, nil
	})
	model := newMockModel(mp).WithMiddleware(
		WithRetry(3, func(attempt int) time.Duration { return time.Millisecond }),
	)

	resp, err := model.Complete(context.Background(), []Message{UserMessage("test")})
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	if resp.Text != "success" {
		t.Errorf("expected 'success', got %q", resp.Text)
	}
	if atomic.LoadInt32(&callCount) != 3 {
		t.Errorf("expected 3 calls, got %d", callCount)
	}
}

func TestWithRetry_AllFail(t *testing.T) {
	providerErr := errors.New("persistent error")
	mp := newMockProviderFunc(func(ctx context.Context, req provider.Request) (provider.Response, error) {
		return provider.Response{}, providerErr
	})
	model := newMockModel(mp).WithMiddleware(
		WithRetry(2, func(attempt int) time.Duration { return time.Millisecond }),
	)

	_, err := model.Complete(context.Background(), []Message{UserMessage("test")})
	if err == nil {
		t.Fatal("expected error, got nil")
	}
	if !errors.Is(err, providerErr) {
		t.Errorf("expected wrapped persistent error, got %v", err)
	}
	if len(mp.Requests) != 3 {
		t.Errorf("expected 3 requests (1 initial + 2 retries), got %d", len(mp.Requests))
	}
}

func TestWithRetry_ContextCancelled(t *testing.T) {
	mp := newMockProviderFunc(func(ctx context.Context, req provider.Request) (provider.Response, error) {
		return provider.Response{}, errors.New("fail")
	})
	model := newMockModel(mp).WithMiddleware(
		WithRetry(10, func(attempt int) time.Duration { return 5 * time.Second }),
	)

	ctx, cancel := context.WithCancel(context.Background())
	// Cancel after a short delay
	go func() {
		time.Sleep(50 * time.Millisecond)
		cancel()
	}()

	_, err := model.Complete(ctx, []Message{UserMessage("test")})
	if err == nil {
		t.Fatal("expected error, got nil")
	}
	if !errors.Is(err, context.Canceled) {
		t.Errorf("expected context.Canceled, got %v", err)
	}
}

func TestWithTimeout(t *testing.T) {
	mp := newMockProvider(provider.Response{Text: "fast"})
	model := newMockModel(mp).WithMiddleware(WithTimeout(5 * time.Second))

	resp, err := model.Complete(context.Background(), []Message{UserMessage("test")})
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	if resp.Text != "fast" {
		t.Errorf("expected 'fast', got %q", resp.Text)
	}
}

func TestWithTimeout_Exceeded(t *testing.T) {
	mp := newMockProviderFunc(func(ctx context.Context, req provider.Request) (provider.Response, error) {
		select {
		case <-ctx.Done():
			return provider.Response{}, ctx.Err()
		case <-time.After(5 * time.Second):
			return provider.Response{Text: "slow"}, nil
		}
	})
	model := newMockModel(mp).WithMiddleware(WithTimeout(50 * time.Millisecond))

	_, err := model.Complete(context.Background(), []Message{UserMessage("test")})
	if err == nil {
		t.Fatal("expected error, got nil")
	}
	if !errors.Is(err, context.DeadlineExceeded) {
		t.Errorf("expected DeadlineExceeded, got %v", err)
	}
}

func TestWithUsageTracking(t *testing.T) {
	mp := newMockProvider(provider.Response{
		Text: "ok",
		Usage: &provider.Usage{
			InputTokens:  10,
			OutputTokens: 5,
			TotalTokens:  15,
		},
	})
	tracker := &UsageTracker{}
	model := newMockModel(mp).WithMiddleware(WithUsageTracking(tracker))

	// Make two requests
	for i := 0; i < 2; i++ {
		_, err := model.Complete(context.Background(), []Message{UserMessage("test")})
		if err != nil {
			t.Fatalf("unexpected error on call %d: %v", i, err)
		}
	}

	input, output, requests := tracker.Summary()
	if input != 20 {
		t.Errorf("expected total input 20, got %d", input)
	}
	if output != 10 {
		t.Errorf("expected total output 10, got %d", output)
	}
	if requests != 2 {
		t.Errorf("expected 2 requests, got %d", requests)
	}
}

func TestWithUsageTracking_NilUsage(t *testing.T) {
	mp := newMockProvider(provider.Response{Text: "no usage"})
	tracker := &UsageTracker{}
	model := newMockModel(mp).WithMiddleware(WithUsageTracking(tracker))

	_, err := model.Complete(context.Background(), []Message{UserMessage("test")})
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}

	input, output, requests := tracker.Summary()
	if input != 0 || output != 0 {
		t.Errorf("expected 0 tokens with nil usage, got input=%d output=%d", input, output)
	}
	// Add(nil) returns early without incrementing TotalRequests
	if requests != 0 {
		t.Errorf("expected 0 requests (nil usage skips Add), got %d", requests)
	}
}

func TestUsageTracker_Concurrent(t *testing.T) {
	tracker := &UsageTracker{}
	var wg sync.WaitGroup

	for i := 0; i < 100; i++ {
		wg.Add(1)
		go func() {
			defer wg.Done()
			tracker.Add(&Usage{
				InputTokens:  10,
				OutputTokens: 5,
				TotalTokens:  15,
			})
		}()
	}

	wg.Wait()

	input, output, requests := tracker.Summary()
	if input != 1000 {
		t.Errorf("expected total input 1000, got %d", input)
	}
	if output != 500 {
		t.Errorf("expected total output 500, got %d", output)
	}
	if requests != 100 {
		t.Errorf("expected 100 requests, got %d", requests)
	}
}

func TestMiddleware_Chaining(t *testing.T) {
	var order []string
	mw1 := func(next CompletionFunc) CompletionFunc {
		return func(ctx context.Context, model string, messages []Message, cfg *requestConfig) (Response, error) {
			order = append(order, "mw1-before")
			resp, err := next(ctx, model, messages, cfg)
			order = append(order, "mw1-after")
			return resp, err
		}
	}
	mw2 := func(next CompletionFunc) CompletionFunc {
		return func(ctx context.Context, model string, messages []Message, cfg *requestConfig) (Response, error) {
			order = append(order, "mw2-before")
			resp, err := next(ctx, model, messages, cfg)
			order = append(order, "mw2-after")
			return resp, err
		}
	}

	mp := newMockProvider(provider.Response{Text: "ok"})
	model := newMockModel(mp).WithMiddleware(mw1, mw2)

	_, err := model.Complete(context.Background(), []Message{UserMessage("test")})
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}

	expected := []string{"mw1-before", "mw2-before", "mw2-after", "mw1-after"}
	if len(order) != len(expected) {
		t.Fatalf("expected %d middleware calls, got %d: %v", len(expected), len(order), order)
	}
	for i, v := range expected {
		if order[i] != v {
			t.Errorf("order[%d]: expected %q, got %q", i, v, order[i])
		}
	}
}

func TestWithLogging(t *testing.T) {
	mp := newMockProvider(provider.Response{Text: "logged"})
	logger := slog.Default()
	model := newMockModel(mp).WithMiddleware(WithLogging(logger))

	resp, err := model.Complete(context.Background(), []Message{UserMessage("test")})
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	if resp.Text != "logged" {
		t.Errorf("expected 'logged', got %q", resp.Text)
	}
}

func TestWithLogging_Error(t *testing.T) {
	providerErr := errors.New("log this error")
	mp := newMockProviderFunc(func(ctx context.Context, req provider.Request) (provider.Response, error) {
		return provider.Response{}, providerErr
	})
	logger := slog.Default()
	model := newMockModel(mp).WithMiddleware(WithLogging(logger))

	_, err := model.Complete(context.Background(), []Message{UserMessage("test")})
	if !errors.Is(err, providerErr) {
		t.Errorf("expected provider error, got %v", err)
	}
}