Add public prepare engine API

engine.go

@@ -0,0 +1,99 @@
+package scriptorium
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"net/http"
+	"strings"
+	"time"
+
+	artifactadapter "gitea.maximumdirect.net/eric/scriptorium/internal/artifact"
+	"gitea.maximumdirect.net/eric/scriptorium/internal/defaults"
+	"gitea.maximumdirect.net/eric/scriptorium/internal/llm"
+	"gitea.maximumdirect.net/eric/scriptorium/internal/profile"
+	"gitea.maximumdirect.net/eric/scriptorium/internal/prompt"
+	"gitea.maximumdirect.net/eric/scriptorium/internal/promptdef"
+	"gitea.maximumdirect.net/eric/scriptorium/internal/usecase"
+	"gitea.maximumdirect.net/eric/scriptorium/internal/validate"
+)
+
+// ErrInvalidConfig indicates invalid public engine configuration.
+var ErrInvalidConfig = errors.New("invalid engine configuration")
+
+// Engine prepares Scriptorium prompt requests.
+type Engine struct {
+	runner *usecase.Runner
+}
+
+// Config configures a public Scriptorium engine.
+type Config struct {
+	PromptDir  string
+	ProfileDir string
+	SchemaDir  string
+	Timeout    time.Duration
+	HTTPClient *http.Client
+}
+
+// Option customizes engine construction.
+type Option func(*engineOptions) error
+
+type engineOptions struct{}
+
+// NewEngine constructs an Engine using the same default internal components as
+// the CLI and HTTP adapters.
+func NewEngine(cfg Config, opts ...Option) (*Engine, error) {
+	if strings.TrimSpace(cfg.PromptDir) == "" {
+		return nil, fmt.Errorf("%w: prompt directory is required", ErrInvalidConfig)
+	}
+	if strings.TrimSpace(cfg.ProfileDir) == "" {
+		return nil, fmt.Errorf("%w: profile directory is required", ErrInvalidConfig)
+	}
+
+	var options engineOptions
+	for _, opt := range opts {
+		if opt == nil {
+			continue
+		}
+		if err := opt(&options); err != nil {
+			return nil, fmt.Errorf("%w: %v", ErrInvalidConfig, err)
+		}
+	}
+
+	schemaDir := cfg.SchemaDir
+	if strings.TrimSpace(schemaDir) == "" {
+		schemaDir = defaults.SchemaDirDefault
+	}
+
+	llmClient, err := llm.NewOpenAICompatibleClient(llm.OpenAICompatibleConfig{
+		Timeout:    cfg.Timeout,
+		HTTPClient: cfg.HTTPClient,
+	})
+	if err != nil {
+		return nil, fmt.Errorf("%w: %v", ErrInvalidConfig, err)
+	}
+
+	return &Engine{
+		runner: usecase.NewRunner(
+			promptdef.NewFilesystemRepository(cfg.PromptDir),
+			profile.NewFilesystemRepository(cfg.ProfileDir),
+			artifactadapter.NewCompositeReader(),
+			prompt.NewGoRenderer(),
+			llmClient,
+			validate.NewStandardValidator(schemaDir),
+		),
+	}, nil
+}
+
+// Prepare resolves a prompt request without calling an LLM.
+func (e *Engine) Prepare(ctx context.Context, req RunRequest) (*PreparedRun, error) {
+	if e == nil || e.runner == nil {
+		return nil, fmt.Errorf("%w: engine is nil", ErrInvalidConfig)
+	}
+
+	prepared, err := e.runner.Prepare(ctx, toDomainRunRequest(req))
+	if err != nil {
+		return nil, err
+	}
+	return fromDomainPreparedRun(prepared), nil
+}