package utils

import (
	"context"
	"testing"
	"time"

	schemas "github.com/maximhq/bifrost/core/schemas"
)

func TestCheckFirstStreamChunk_ErrorInFirstChunk(t *testing.T) {
	stream := make(chan *schemas.BifrostStreamChunk, 2)
	stream <- &schemas.BifrostStreamChunk{
		BifrostError: &schemas.BifrostError{
			Error: &schemas.ErrorField{
				Code:    schemas.Ptr("limit_burst_rate"),
				Message: "Request rate increased too quickly",
			},
		},
	}
	close(stream)

	_, drainDone, err := CheckFirstStreamChunkForError(context.Background(), stream)
	if err == nil {
		t.Fatal("expected error, got nil")
	}
	<-drainDone
	if err.Error.Message != "Request rate increased too quickly" {
		t.Errorf("unexpected error message: %s", err.Error.Message)
	}
	if err.Error.Code == nil || *err.Error.Code != "limit_burst_rate" {
		t.Errorf("unexpected error code: %v", err.Error.Code)
	}
}

func TestCheckFirstStreamChunk_ValidFirstChunk(t *testing.T) {
	stream := make(chan *schemas.BifrostStreamChunk, 3)
	chunk1 := &schemas.BifrostStreamChunk{
		BifrostChatResponse: &schemas.BifrostChatResponse{
			ID: "chatcmpl-123",
		},
	}
	chunk2 := &schemas.BifrostStreamChunk{
		BifrostChatResponse: &schemas.BifrostChatResponse{
			ID: "chatcmpl-123",
		},
	}
	stream <- chunk1
	stream <- chunk2
	close(stream)

	wrapped, _, err := CheckFirstStreamChunkForError(context.Background(), stream)
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}

	// First chunk should be re-injected
	got1 := <-wrapped
	if got1.BifrostChatResponse == nil || got1.BifrostChatResponse.ID != "chatcmpl-123" {
		t.Error("first chunk not re-injected correctly")
	}

	// Second chunk should follow
	got2 := <-wrapped
	if got2.BifrostChatResponse == nil || got2.BifrostChatResponse.ID != "chatcmpl-123" {
		t.Error("second chunk not forwarded correctly")
	}

	// Channel should be closed
	_, ok := <-wrapped
	if ok {
		t.Error("expected wrapped channel to be closed")
	}
}

func TestCheckFirstStreamChunk_EmptyStream(t *testing.T) {
	stream := make(chan *schemas.BifrostStreamChunk)
	close(stream)

	wrapped, drainDone, err := CheckFirstStreamChunkForError(context.Background(), stream)
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}

	// Empty stream should return nil channel
	if wrapped != nil {
		t.Error("expected nil channel for empty stream")
	}

	// drainDone should be already closed
	select {
	case <-drainDone:
	default:
		t.Error("expected drainDone to be closed for empty stream")
	}
}

func TestCheckFirstStreamChunk_ErrorInSecondChunk(t *testing.T) {
	stream := make(chan *schemas.BifrostStreamChunk, 3)
	stream <- &schemas.BifrostStreamChunk{
		BifrostChatResponse: &schemas.BifrostChatResponse{
			ID: "chatcmpl-123",
		},
	}
	stream <- &schemas.BifrostStreamChunk{
		BifrostError: &schemas.BifrostError{
			Error: &schemas.ErrorField{
				Message: "some error in second chunk",
			},
		},
	}
	close(stream)

	// Should NOT return error — only first chunk matters for retry
	wrapped, _, err := CheckFirstStreamChunkForError(context.Background(), stream)
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}

	// Read all chunks
	got1 := <-wrapped
	if got1.BifrostChatResponse == nil {
		t.Error("first chunk should be valid data")
	}
	got2 := <-wrapped
	if got2.BifrostError == nil {
		t.Error("second chunk should be the error")
	}

	_, ok := <-wrapped
	if ok {
		t.Error("expected wrapped channel to be closed")
	}
}

func TestCheckFirstStreamChunk_ErrorDrainsSource(t *testing.T) {
	stream := make(chan *schemas.BifrostStreamChunk, 5)
	stream <- &schemas.BifrostStreamChunk{
		BifrostError: &schemas.BifrostError{
			Error: &schemas.ErrorField{
				Message: "rate limit error",
			},
		},
	}
	// Add more chunks that should be drained
	stream <- &schemas.BifrostStreamChunk{
		BifrostChatResponse: &schemas.BifrostChatResponse{ID: "1"},
	}
	stream <- &schemas.BifrostStreamChunk{
		BifrostChatResponse: &schemas.BifrostChatResponse{ID: "2"},
	}
	close(stream)

	_, drainDone, err := CheckFirstStreamChunkForError(context.Background(), stream)
	if err == nil {
		t.Fatal("expected error, got nil")
	}
	<-drainDone
	if err.Error.Message != "rate limit error" {
		t.Errorf("unexpected error message: %s", err.Error.Message)
	}
	if drainDone == nil {
		t.Fatal("expected drainDone channel, got nil")
	}
	// Wait for drain to complete — verifies the channel signals properly
	<-drainDone
}

func TestCheckFirstStreamChunk_ErrorWithEmptyMessage(t *testing.T) {
	// Error with empty message and no code/type should NOT be treated as an error
	stream := make(chan *schemas.BifrostStreamChunk, 2)
	stream <- &schemas.BifrostStreamChunk{
		BifrostError: &schemas.BifrostError{
			Error: &schemas.ErrorField{
				Message: "",
			},
		},
	}
	close(stream)

	wrapped, _, err := CheckFirstStreamChunkForError(context.Background(), stream)
	if err != nil {
		t.Fatalf("unexpected error for empty message: %v", err)
	}
	// Should be treated as valid chunk
	<-wrapped
}

func TestCheckFirstStreamChunk_CtxCancelUnblocksWrapper(t *testing.T) {
	// Source with cap=1 so wrapped also has cap=1. wrapped is left full by
	// the re-injected first chunk, which makes the forwarder goroutine block
	// on its next send — the exact leak condition this test guards against.
	src := make(chan *schemas.BifrostStreamChunk, 1)
	src <- &schemas.BifrostStreamChunk{
		BifrostChatResponse: &schemas.BifrostChatResponse{ID: "1"},
	}

	ctx, cancel := context.WithCancel(context.Background())

	wrapped, drainDone, err := CheckFirstStreamChunkForError(ctx, src)
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	if wrapped == nil {
		t.Fatal("expected wrapped channel, got nil")
	}

	// Push a second chunk; forwarder will read it from src and then block
	// trying to send into the full wrapped channel (we intentionally never
	// read from wrapped).
	src <- &schemas.BifrostStreamChunk{
		BifrostChatResponse: &schemas.BifrostChatResponse{ID: "2"},
	}

	// Cancel — forwarder must stop trying to send to wrapped and drain src.
	cancel()

	// Simulate the upstream producer still emitting, then closing. The
	// drain loop should consume these and terminate.
	src <- &schemas.BifrostStreamChunk{
		BifrostChatResponse: &schemas.BifrostChatResponse{ID: "3"},
	}
	close(src)

	select {
	case <-drainDone:
	case <-time.After(time.Second):
		t.Fatal("drainDone did not close after ctx cancel; forwarder goroutine leaked")
	}
}

func TestCheckFirstStreamChunk_CodeOnlyError(t *testing.T) {
	// Error with code but no message should be treated as an error
	stream := make(chan *schemas.BifrostStreamChunk, 2)
	stream <- &schemas.BifrostStreamChunk{
		BifrostError: &schemas.BifrostError{
			Error: &schemas.ErrorField{
				Code: schemas.Ptr("limit_burst_rate"),
			},
		},
	}
	close(stream)

	_, drainDone, err := CheckFirstStreamChunkForError(context.Background(), stream)
	if err == nil {
		t.Fatal("expected error for code-only error, got nil")
	}
	<-drainDone
	if err.Error.Code == nil || *err.Error.Code != "limit_burst_rate" {
		t.Errorf("unexpected error code: %v", err.Error.Code)
	}
}