Add artifact reading and output validation

internal/artifact/reader.go

@@ -0,0 +1,122 @@
+package artifact
+
+import (
+	"context"
+	"crypto/sha256"
+	"errors"
+	"fmt"
+	"io"
+	"mime"
+	"os"
+	"path/filepath"
+
+	"gitea.maximumdirect.net/eric/promptkit/internal/defaults"
+	"gitea.maximumdirect.net/eric/promptkit/internal/domain"
+)
+
+var (
+	ErrUnsupportedRefType = errors.New("unsupported artifact reference type")
+	ErrMissingInlineBody  = errors.New("missing body for inline artifact")
+	ErrMissingFilePath    = errors.New("missing file path for file artifact")
+)
+
+// Reader resolves artifact references into actual artifacts.
+type Reader interface {
+	Read(ctx context.Context, ref domain.ArtifactRef) (*domain.Artifact, error)
+}
+
+// CompositeReader routes artifact resolution based on the reference type.
+type CompositeReader struct {
+	inlineReader *inlineReader
+	fileReader   Reader
+}
+
+func NewCompositeReader() Reader {
+	return &CompositeReader{
+		inlineReader: &inlineReader{},
+		fileReader:   &fileReader{},
+	}
+}
+
+func (c *CompositeReader) Read(ctx context.Context, ref domain.ArtifactRef) (*domain.Artifact, error) {
+	select {
+	case <-ctx.Done():
+		return nil, ctx.Err()
+	default:
+	}
+
+	switch ref.Type {
+	case domain.ArtifactRefInline:
+		return c.inlineReader.Read(ctx, ref)
+	case domain.ArtifactRefFile:
+		return c.fileReader.Read(ctx, ref)
+	default:
+		return nil, fmt.Errorf("%w: %s", ErrUnsupportedRefType, ref.Type)
+	}
+}
+
+type inlineReader struct{}
+
+func (r *inlineReader) Read(ctx context.Context, ref domain.ArtifactRef) (*domain.Artifact, error) {
+	select {
+	case <-ctx.Done():
+		return nil, ctx.Err()
+	default:
+	}
+
+	if ref.Body == "" {
+		return nil, ErrMissingInlineBody
+	}
+
+	body := []byte(ref.Body)
+	return &domain.Artifact{
+		ContentType: defaults.ContentTypeTextPlain,
+		Body:        body,
+		Size:        int64(len(body)),
+		Hash:        fmt.Sprintf("%x", sha256.Sum256(body)),
+		URI:         ref.URI,
+	}, nil
+}
+
+type fileReader struct{}
+
+func (r *fileReader) Read(ctx context.Context, ref domain.ArtifactRef) (*domain.Artifact, error) {
+	select {
+	case <-ctx.Done():
+		return nil, ctx.Err()
+	default:
+	}
+
+	if ref.URI == "" {
+		return nil, ErrMissingFilePath
+	}
+
+	return readFileArtifact(ref.URI)
+}
+
+func readFileArtifact(path string) (*domain.Artifact, error) {
+	file, err := os.Open(path)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read file %s: %w", path, err)
+	}
+	defer file.Close()
+
+	data, err := io.ReadAll(file)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read file %s: %w", path, err)
+	}
+
+	contentType := mime.TypeByExtension(filepath.Ext(path))
+	if contentType == "" {
+		contentType = defaults.ContentTypeTextPlain
+	}
+
+	return &domain.Artifact{
+		Name:        filepath.Base(path),
+		ContentType: contentType,
+		Body:        data,
+		URI:         path,
+		Size:        int64(len(data)),
+		Hash:        fmt.Sprintf("%x", sha256.Sum256(data)),
+	}, nil
+}