package llm

import (
	"context"
	"errors"
	"io"
	"testing"

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

func TestStreamReader_TextEvents(t *testing.T) {
	events := []provider.StreamEvent{
		{Type: provider.StreamEventText, Text: "Hello"},
		{Type: provider.StreamEventText, Text: " world"},
		{Type: provider.StreamEventDone, Response: &provider.Response{
			Text: "Hello world",
			Usage: &provider.Usage{
				InputTokens:  5,
				OutputTokens: 2,
				TotalTokens:  7,
			},
		}},
	}
	mp := newMockStreamProvider(events)
	model := newMockModel(mp)

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

	// Read text events
	ev, err := reader.Next()
	if err != nil {
		t.Fatalf("unexpected error on first event: %v", err)
	}
	if ev.Type != StreamEventText || ev.Text != "Hello" {
		t.Errorf("expected text event 'Hello', got type=%d text=%q", ev.Type, ev.Text)
	}

	ev, err = reader.Next()
	if err != nil {
		t.Fatalf("unexpected error on second event: %v", err)
	}
	if ev.Type != StreamEventText || ev.Text != " world" {
		t.Errorf("expected text event ' world', got type=%d text=%q", ev.Type, ev.Text)
	}

	// Read done event
	ev, err = reader.Next()
	if err != nil {
		t.Fatalf("unexpected error on done event: %v", err)
	}
	if ev.Type != StreamEventDone {
		t.Errorf("expected done event, got type=%d", ev.Type)
	}
	if ev.Response == nil {
		t.Fatal("expected response in done event")
	}
	if ev.Response.Text != "Hello world" {
		t.Errorf("expected final text 'Hello world', got %q", ev.Response.Text)
	}

	// Subsequent reads should return EOF
	_, err = reader.Next()
	if !errors.Is(err, io.EOF) {
		t.Errorf("expected io.EOF after done, got %v", err)
	}
}

func TestStreamReader_ToolCallEvents(t *testing.T) {
	events := []provider.StreamEvent{
		{
			Type:      provider.StreamEventToolStart,
			ToolIndex: 0,
			ToolCall:  &provider.ToolCall{ID: "tc1", Name: "search"},
		},
		{
			Type:      provider.StreamEventToolDelta,
			ToolIndex: 0,
			ToolCall:  &provider.ToolCall{Arguments: `{"query":`},
		},
		{
			Type:      provider.StreamEventToolDelta,
			ToolIndex: 0,
			ToolCall:  &provider.ToolCall{Arguments: `"test"}`},
		},
		{
			Type:      provider.StreamEventToolEnd,
			ToolIndex: 0,
			ToolCall:  &provider.ToolCall{ID: "tc1", Name: "search", Arguments: `{"query":"test"}`},
		},
		{
			Type: provider.StreamEventDone,
			Response: &provider.Response{
				ToolCalls: []provider.ToolCall{
					{ID: "tc1", Name: "search", Arguments: `{"query":"test"}`},
				},
			},
		},
	}
	mp := newMockStreamProvider(events)
	model := newMockModel(mp)

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

	// Read tool start
	ev, err := reader.Next()
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	if ev.Type != StreamEventToolStart {
		t.Errorf("expected tool start, got type=%d", ev.Type)
	}
	if ev.ToolCall == nil || ev.ToolCall.Name != "search" {
		t.Errorf("expected tool call 'search', got %+v", ev.ToolCall)
	}

	// Read tool deltas
	ev, _ = reader.Next()
	if ev.Type != StreamEventToolDelta {
		t.Errorf("expected tool delta, got type=%d", ev.Type)
	}

	ev, _ = reader.Next()
	if ev.Type != StreamEventToolDelta {
		t.Errorf("expected tool delta, got type=%d", ev.Type)
	}

	// Read tool end
	ev, _ = reader.Next()
	if ev.Type != StreamEventToolEnd {
		t.Errorf("expected tool end, got type=%d", ev.Type)
	}
	if ev.ToolCall == nil || ev.ToolCall.Arguments != `{"query":"test"}` {
		t.Errorf("expected complete arguments, got %+v", ev.ToolCall)
	}

	// Read done
	ev, _ = reader.Next()
	if ev.Type != StreamEventDone {
		t.Errorf("expected done, got type=%d", ev.Type)
	}
	if ev.Response == nil || len(ev.Response.ToolCalls) != 1 {
		t.Error("expected response with 1 tool call")
	}
}

func TestStreamReader_Error(t *testing.T) {
	streamErr := errors.New("stream failed")
	mp := &mockProvider{
		CompleteFunc: func(ctx context.Context, req provider.Request) (provider.Response, error) {
			return provider.Response{}, nil
		},
		StreamFunc: func(ctx context.Context, req provider.Request, ch chan<- provider.StreamEvent) error {
			ch <- provider.StreamEvent{Type: provider.StreamEventText, Text: "partial"}
			ch <- provider.StreamEvent{Type: provider.StreamEventError, Error: streamErr}
			return nil
		},
	}
	model := newMockModel(mp)

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

	// Read partial text
	ev, err := reader.Next()
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	if ev.Text != "partial" {
		t.Errorf("expected 'partial', got %q", ev.Text)
	}

	// Read error
	_, err = reader.Next()
	if err == nil {
		t.Fatal("expected error, got nil")
	}
	if !errors.Is(err, streamErr) {
		t.Errorf("expected stream error, got %v", err)
	}
}

func TestStreamReader_Close(t *testing.T) {
	// Create a stream that sends one event then blocks until context is cancelled
	mp := &mockProvider{
		CompleteFunc: func(ctx context.Context, req provider.Request) (provider.Response, error) {
			return provider.Response{}, nil
		},
		StreamFunc: func(ctx context.Context, req provider.Request, ch chan<- provider.StreamEvent) error {
			ch <- provider.StreamEvent{Type: provider.StreamEventText, Text: "start"}
			<-ctx.Done()
			return ctx.Err()
		},
	}
	model := newMockModel(mp)

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

	// Read the first event
	ev, err := reader.Next()
	if err != nil {
		t.Fatalf("unexpected error on first event: %v", err)
	}
	if ev.Text != "start" {
		t.Errorf("expected 'start', got %q", ev.Text)
	}

	// Close should cancel context
	if err := reader.Close(); err != nil {
		t.Fatalf("close error: %v", err)
	}

	// After close, Next should eventually terminate with either EOF or context error.
	// The exact behavior depends on goroutine scheduling: the channel may close (EOF)
	// or the error event from the cancelled context may arrive first.
	_, err = reader.Next()
	if err == nil {
		t.Error("expected error after close, got nil")
	}
}

func TestStreamReader_Collect(t *testing.T) {
	events := []provider.StreamEvent{
		{Type: provider.StreamEventText, Text: "Hello"},
		{Type: provider.StreamEventText, Text: " world"},
		{Type: provider.StreamEventDone, Response: &provider.Response{
			Text: "Hello world",
			Usage: &provider.Usage{
				InputTokens:  10,
				OutputTokens: 2,
				TotalTokens:  12,
			},
		}},
	}
	mp := newMockStreamProvider(events)
	model := newMockModel(mp)

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

	resp, err := reader.Collect()
	if err != nil {
		t.Fatalf("collect error: %v", err)
	}
	if resp.Text != "Hello world" {
		t.Errorf("expected 'Hello world', got %q", resp.Text)
	}
	if resp.Usage == nil {
		t.Fatal("expected usage")
	}
	if resp.Usage.InputTokens != 10 {
		t.Errorf("expected 10 input tokens, got %d", resp.Usage.InputTokens)
	}
}

func TestStreamReader_Text(t *testing.T) {
	events := []provider.StreamEvent{
		{Type: provider.StreamEventText, Text: "result"},
		{Type: provider.StreamEventDone, Response: &provider.Response{Text: "result"}},
	}
	mp := newMockStreamProvider(events)
	model := newMockModel(mp)

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

	text, err := reader.Text()
	if err != nil {
		t.Fatalf("text error: %v", err)
	}
	if text != "result" {
		t.Errorf("expected 'result', got %q", text)
	}
}

func TestStreamReader_EmptyStream(t *testing.T) {
	// Stream that completes without a done event (no response)
	mp := newMockStreamProvider([]provider.StreamEvent{
		{Type: provider.StreamEventText, Text: "hi"},
	})
	model := newMockModel(mp)

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

	_, err = reader.Collect()
	if err == nil {
		t.Fatal("expected error for stream without done event")
	}
}

func TestStreamReader_StreamFuncError(t *testing.T) {
	// Stream function returns error directly
	mp := &mockProvider{
		CompleteFunc: func(ctx context.Context, req provider.Request) (provider.Response, error) {
			return provider.Response{}, nil
		},
		StreamFunc: func(ctx context.Context, req provider.Request, ch chan<- provider.StreamEvent) error {
			return errors.New("stream init failed")
		},
	}
	model := newMockModel(mp)

	reader, err := model.Stream(context.Background(), []Message{UserMessage("test")})
	if err != nil {
		t.Fatalf("unexpected error creating reader: %v", err)
	}
	defer reader.Close()

	// The error should come through as an error event
	_, err = reader.Collect()
	if err == nil {
		t.Fatal("expected error from stream function")
	}
}