package promptkit_test

import (
	"context"
	"errors"
	"strings"
	"testing"

	"go.maximumdirect.net/promptkit"
)

func TestNestedErrorsRetainEachCauseWithoutDuplicatingDiagnostics(t *testing.T) {
	cause := errors.New("independent-leaf-diagnostic")
	for range 10 {
		parent := newSimpleEngine(t, "parent", promptkit.WithLLMClient(&fakeLLMClient{err: cause}))
		_, err := parent.Run(context.Background(), promptkit.RunRequest{PromptID: "prompt"})
		if !errors.Is(err, cause) || !errors.Is(err, promptkit.ErrLLMGenerate) {
			t.Fatalf("lost owner or cause: %v", err)
		}
		if strings.Count(err.Error(), "independent-leaf-diagnostic") != 1 {
			t.Fatalf("duplicated leaf: %v", err)
		}
		cause = err
	}
}

type nestedErrorReader struct{ cause error }

func (r nestedErrorReader) Read(context.Context, promptkit.ArtifactRef) (*promptkit.Artifact, error) {
	return nil, r.cause
}

func TestNestedEngineErrorKeepsOwningOperation(t *testing.T) {
	child := newSimpleEngine(t, "child")
	_, childErr := child.Run(context.Background(), promptkit.RunRequest{PromptID: "missing"})
	if !errors.Is(childErr, promptkit.ErrPromptNotFound) {
		t.Fatalf("child error = %v", childErr)
	}
	client := &fakeLLMClient{err: childErr}
	parent := newSimpleEngine(t, "hello", promptkit.WithLLMClient(client))
	_, err := parent.Run(context.Background(), promptkit.RunRequest{PromptID: "prompt"})
	if !errors.Is(err, promptkit.ErrLLMGenerate) || !errors.Is(err, childErr) || !errors.Is(err, promptkit.ErrPromptNotFound) {
		t.Fatalf("generation error = %v", err)
	}

	readerParent := newSimpleEngine(t, "hello", promptkit.WithArtifactReader(nestedErrorReader{cause: childErr}))
	_, err = readerParent.Prepare(context.Background(), promptkit.RunRequest{PromptID: "prompt", Inputs: map[string]promptkit.ArtifactRef{"extra": promptkit.Inline("data")}})
	if !errors.Is(err, promptkit.ErrArtifactLoad) || !errors.Is(err, childErr) || !errors.Is(err, promptkit.ErrPromptNotFound) {
		t.Fatalf("artifact error = %v", err)
	}
}