Extract prompt sources and rendering internals

internal/prompt/go_renderer.go

@@ -0,0 +1,125 @@
+package prompt
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"fmt"
+	"gitea.maximumdirect.net/eric/promptkit/internal/domain"
+	"strings"
+	"text/template"
+	"unicode/utf8"
+)
+
+var (
+	ErrMissingRequiredInput = errors.New("missing required input artifact")
+	ErrUnknownInput         = errors.New("referenced unknown input artifact")
+	ErrInvalidTemplate      = errors.New("invalid prompt template")
+	ErrRenderFailure        = errors.New("prompt render failure")
+	ErrInvalidMessageRole   = errors.New("invalid or empty message role")
+)
+
+type goRenderer struct{}
+
+func NewGoRenderer() Renderer {
+	return &goRenderer{}
+}
+
+func (r *goRenderer) Render(ctx context.Context, definition *domain.PromptDefinition, inputs map[string]*domain.Artifact, vars map[string]string) (*domain.RenderedPrompt, error) {
+	if definition == nil {
+		return nil, fmt.Errorf("%w: nil prompt definition", ErrRenderFailure)
+	}
+
+	// 1. Verify required inputs
+	for _, in := range definition.Inputs {
+		if !in.Required {
+			continue
+		}
+		art, ok := inputs[in.Name]
+		if !ok || art == nil {
+			return nil, fmt.Errorf("%w: %s", ErrMissingRequiredInput, in.Name)
+		}
+	}
+
+	// 2. Setup template functions
+	funcs := template.FuncMap{
+		"input": func(name string) (string, error) {
+			art, ok := inputs[name]
+			if !ok || art == nil {
+				return "", fmt.Errorf("%w: %s", ErrUnknownInput, name)
+			}
+			return string(art.Body), nil
+		},
+	}
+
+	sessionID, err := renderSessionID(definition.SessionID, funcs, vars)
+	if err != nil {
+		return nil, err
+	}
+
+	var renderedMessages []domain.RenderedMessage
+
+	for i, tmplMsg := range definition.Templates {
+		select {
+		case <-ctx.Done():
+			return nil, ctx.Err()
+		default:
+		}
+
+		if tmplMsg.Role == "" {
+			return nil, fmt.Errorf("%w: message %d", ErrInvalidMessageRole, i)
+		}
+
+		// Parse and execute template
+		tmpl, err := template.New(fmt.Sprintf("msg_%d", i)).Funcs(funcs).Option("missingkey=error").Parse(tmplMsg.Content)
+		if err != nil {
+			return nil, fmt.Errorf("%w: message %d: %v", ErrInvalidTemplate, i, err)
+		}
+
+		var buf bytes.Buffer
+		if err := tmpl.Execute(&buf, vars); err != nil {
+			return nil, fmt.Errorf("%w: message %d: %w", ErrRenderFailure, i, err)
+		}
+
+		renderedMessages = append(renderedMessages, domain.RenderedMessage{
+			Role:         tmplMsg.Role,
+			Content:      buf.String(),
+			CacheControl: cloneCacheControl(tmplMsg.CacheControl),
+		})
+	}
+
+	return &domain.RenderedPrompt{
+		SessionID: sessionID,
+		Messages:  renderedMessages,
+	}, nil
+}
+
+func renderSessionID(raw string, funcs template.FuncMap, vars map[string]string) (string, error) {
+	if strings.TrimSpace(raw) == "" {
+		return "", nil
+	}
+
+	tmpl, err := template.New("session_id").Funcs(funcs).Option("missingkey=error").Parse(raw)
+	if err != nil {
+		return "", fmt.Errorf("%w: session_id: %v", ErrInvalidTemplate, err)
+	}
+
+	var buf bytes.Buffer
+	if err := tmpl.Execute(&buf, vars); err != nil {
+		return "", fmt.Errorf("%w: session_id: %w", ErrRenderFailure, err)
+	}
+
+	sessionID := strings.TrimSpace(buf.String())
+	if n := utf8.RuneCountInString(sessionID); n > domain.SessionIDMaxLength {
+		return "", fmt.Errorf("%w: session_id length %d exceeds maximum %d", ErrRenderFailure, n, domain.SessionIDMaxLength)
+	}
+	return sessionID, nil
+}
+
+func cloneCacheControl(in *domain.CacheControl) *domain.CacheControl {
+	if in == nil {
+		return nil
+	}
+	out := *in
+	return &out
+}

internal/prompt/renderer.go

@@ -0,0 +1,11 @@
+package prompt
+
+import (
+	"context"
+	"gitea.maximumdirect.net/eric/promptkit/internal/domain"
+)
+
+// Renderer renders prompt templates using named artifacts and variables.
+type Renderer interface {
+	Render(ctx context.Context, definition *domain.PromptDefinition, inputs map[string]*domain.Artifact, vars map[string]string) (*domain.RenderedPrompt, error)
+}

internal/prompt/renderer_test.go

@@ -0,0 +1,345 @@
+package prompt
+
+import (
+	"context"
+	"errors"
+	"strings"
+	"testing"
+
+	"gitea.maximumdirect.net/eric/promptkit/internal/domain"
+)
+
+func TestGoRenderer_Render(t *testing.T) {
+	renderer := NewGoRenderer()
+	ctx := context.Background()
+
+	inputs := map[string]*domain.Artifact{
+		"transcript": {Body: []byte("The quick brown fox.")},
+	}
+	vars := map[string]string{
+		"role": "helpful assistant",
+		"tone": "concise",
+	}
+
+	t.Run("rendering inline message content", func(t *testing.T) {
+		def := &domain.PromptDefinition{
+			Inputs: []domain.PromptInput{{Name: "transcript", Required: true}},
+			Templates: []domain.PromptMessageTemplate{
+				{Role: "user", Content: "Analyze this: {{input \"transcript\"}}"},
+			},
+		}
+
+		res, err := renderer.Render(ctx, def, inputs, vars)
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+		if len(res.Messages) != 1 {
+			t.Fatalf("expected 1 message, got %d", len(res.Messages))
+		}
+		if res.Messages[0].Content != "Analyze this: The quick brown fox." {
+			t.Fatalf("unexpected rendered content: %q", res.Messages[0].Content)
+		}
+	})
+
+	t.Run("rendering file-backed message content loaded into prompt definition", func(t *testing.T) {
+		def := &domain.PromptDefinition{
+			Inputs: []domain.PromptInput{{Name: "transcript", Required: true}},
+			Templates: []domain.PromptMessageTemplate{
+				{Role: "user", Content: "From file: {{input \"transcript\"}}", ContentFile: "/tmp/user.tmpl"},
+			},
+		}
+
+		res, err := renderer.Render(ctx, def, inputs, vars)
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+		if got := res.Messages[0].Content; got != "From file: The quick brown fox." {
+			t.Fatalf("unexpected file-backed render result: %q", got)
+		}
+	})
+
+	t.Run("rendering system and user messages", func(t *testing.T) {
+		def := &domain.PromptDefinition{
+			Inputs: []domain.PromptInput{{Name: "transcript", Required: true}},
+			Templates: []domain.PromptMessageTemplate{
+				{Role: "system", Content: "You are a {{.role}}."},
+				{Role: "user", Content: "Analyze this: {{input \"transcript\"}}"},
+			},
+		}
+
+		res, err := renderer.Render(ctx, def, inputs, vars)
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+		if len(res.Messages) != 2 {
+			t.Fatalf("expected 2 messages, got %d", len(res.Messages))
+		}
+		if res.Messages[0].Role != "system" || res.Messages[1].Role != "user" {
+			t.Fatalf("unexpected roles: %#v", res.Messages)
+		}
+	})
+
+	t.Run("copying cache control to rendered messages", func(t *testing.T) {
+		def := &domain.PromptDefinition{
+			Inputs: []domain.PromptInput{{Name: "transcript", Required: true}},
+			Templates: []domain.PromptMessageTemplate{
+				{
+					Role:    "system",
+					Content: "You are concise.",
+					CacheControl: &domain.CacheControl{
+						Type: domain.CacheControlEphemeral,
+						TTL:  "1h",
+					},
+				},
+				{Role: "user", Content: "Analyze this: {{input \"transcript\"}}"},
+			},
+		}
+
+		res, err := renderer.Render(ctx, def, inputs, vars)
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+		if len(res.Messages) != 2 {
+			t.Fatalf("expected 2 messages, got %d", len(res.Messages))
+		}
+		if res.Messages[0].CacheControl == nil {
+			t.Fatal("expected rendered cache control")
+		}
+		if res.Messages[0].CacheControl.Type != domain.CacheControlEphemeral {
+			t.Fatalf("unexpected cache control type: %q", res.Messages[0].CacheControl.Type)
+		}
+		if res.Messages[0].CacheControl.TTL != "1h" {
+			t.Fatalf("unexpected cache control ttl: %q", res.Messages[0].CacheControl.TTL)
+		}
+		if res.Messages[1].CacheControl != nil {
+			t.Fatalf("expected no cache control on second message, got %#v", res.Messages[1].CacheControl)
+		}
+	})
+
+	t.Run("rendered cache control does not alias source template", func(t *testing.T) {
+		source := &domain.CacheControl{Type: domain.CacheControlEphemeral, TTL: "1h"}
+		def := &domain.PromptDefinition{
+			Inputs: []domain.PromptInput{{Name: "transcript", Required: true}},
+			Templates: []domain.PromptMessageTemplate{
+				{Role: "system", Content: "You are concise.", CacheControl: source},
+			},
+		}
+
+		res, err := renderer.Render(ctx, def, inputs, vars)
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+		if res.Messages[0].CacheControl == source {
+			t.Fatal("expected rendered cache control to be cloned")
+		}
+
+		res.Messages[0].CacheControl.TTL = ""
+		if source.TTL != "1h" {
+			t.Fatalf("source cache control was mutated, ttl=%q", source.TTL)
+		}
+	})
+
+	t.Run("accessing vars", func(t *testing.T) {
+		def := &domain.PromptDefinition{
+			Inputs: []domain.PromptInput{{Name: "transcript", Required: true}},
+			Templates: []domain.PromptMessageTemplate{
+				{Role: "system", Content: "Speak in a {{.tone}} tone."},
+			},
+		}
+
+		res, err := renderer.Render(ctx, def, inputs, vars)
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+		if res.Messages[0].Content != "Speak in a concise tone." {
+			t.Fatalf("unexpected vars rendering: %q", res.Messages[0].Content)
+		}
+	})
+
+	t.Run("rendering session id from vars", func(t *testing.T) {
+		def := &domain.PromptDefinition{
+			SessionID: "  {{ .session_id }}  ",
+			Inputs:    []domain.PromptInput{{Name: "transcript", Required: true}},
+			Templates: []domain.PromptMessageTemplate{
+				{Role: "system", Content: "Speak in a {{.tone}} tone."},
+			},
+		}
+
+		res, err := renderer.Render(ctx, def, inputs, map[string]string{
+			"tone":       "concise",
+			"session_id": "agent-session-123",
+		})
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+		if res.SessionID != "agent-session-123" {
+			t.Fatalf("unexpected session id: %q", res.SessionID)
+		}
+	})
+
+	t.Run("empty rendered session id is omitted", func(t *testing.T) {
+		def := &domain.PromptDefinition{
+			SessionID: "   ",
+			Inputs:    []domain.PromptInput{{Name: "transcript", Required: true}},
+			Templates: []domain.PromptMessageTemplate{
+				{Role: "system", Content: "Speak in a {{.tone}} tone."},
+			},
+		}
+
+		res, err := renderer.Render(ctx, def, inputs, vars)
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+		if res.SessionID != "" {
+			t.Fatalf("expected empty session id, got %q", res.SessionID)
+		}
+	})
+
+	t.Run("missing session id var fails rendering", func(t *testing.T) {
+		def := &domain.PromptDefinition{
+			SessionID: "{{ .session_id }}",
+			Inputs:    []domain.PromptInput{{Name: "transcript", Required: true}},
+			Templates: []domain.PromptMessageTemplate{
+				{Role: "system", Content: "Speak in a {{.tone}} tone."},
+			},
+		}
+
+		_, err := renderer.Render(ctx, def, inputs, vars)
+		if !errors.Is(err, ErrRenderFailure) {
+			t.Fatalf("expected ErrRenderFailure, got %v", err)
+		}
+	})
+
+	t.Run("too long rendered session id fails rendering", func(t *testing.T) {
+		def := &domain.PromptDefinition{
+			SessionID: "{{ .session_id }}",
+			Inputs:    []domain.PromptInput{{Name: "transcript", Required: true}},
+			Templates: []domain.PromptMessageTemplate{
+				{Role: "system", Content: "Speak in a {{.tone}} tone."},
+			},
+		}
+
+		_, err := renderer.Render(ctx, def, inputs, map[string]string{
+			"tone":       "concise",
+			"session_id": strings.Repeat("x", domain.SessionIDMaxLength+1),
+		})
+		if !errors.Is(err, ErrRenderFailure) {
+			t.Fatalf("expected ErrRenderFailure, got %v", err)
+		}
+	})
+
+	t.Run("inserting required input artifact", func(t *testing.T) {
+		def := &domain.PromptDefinition{
+			Inputs: []domain.PromptInput{{Name: "transcript", Required: true}},
+			Templates: []domain.PromptMessageTemplate{
+				{Role: "user", Content: "{{input \"transcript\"}}"},
+			},
+		}
+
+		res, err := renderer.Render(ctx, def, inputs, vars)
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+		if res.Messages[0].Content != "The quick brown fox." {
+			t.Fatalf("unexpected required input rendering: %q", res.Messages[0].Content)
+		}
+	})
+
+	t.Run("optional input absent and not referenced", func(t *testing.T) {
+		def := &domain.PromptDefinition{
+			Inputs: []domain.PromptInput{
+				{Name: "transcript", Required: true},
+				{Name: "glossary", Required: false},
+			},
+			Templates: []domain.PromptMessageTemplate{
+				{Role: "user", Content: "Transcript: {{input \"transcript\"}}"},
+			},
+		}
+
+		res, err := renderer.Render(ctx, def, inputs, vars)
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+		if len(res.Messages) != 1 {
+			t.Fatalf("expected one rendered message, got %d", len(res.Messages))
+		}
+	})
+
+	t.Run("optional input absent but referenced, expecting failure", func(t *testing.T) {
+		def := &domain.PromptDefinition{
+			Inputs: []domain.PromptInput{
+				{Name: "transcript", Required: true},
+				{Name: "glossary", Required: false},
+			},
+			Templates: []domain.PromptMessageTemplate{
+				{Role: "user", Content: "Glossary: {{input \"glossary\"}}"},
+			},
+		}
+
+		_, err := renderer.Render(ctx, def, inputs, vars)
+		if !errors.Is(err, ErrRenderFailure) {
+			t.Fatalf("expected ErrRenderFailure, got %v", err)
+		}
+		if !errors.Is(err, ErrUnknownInput) {
+			t.Fatalf("expected ErrUnknownInput, got %v", err)
+		}
+	})
+
+	t.Run("required input missing, expecting failure", func(t *testing.T) {
+		def := &domain.PromptDefinition{
+			Inputs: []domain.PromptInput{{Name: "transcript", Required: true}},
+			Templates: []domain.PromptMessageTemplate{
+				{Role: "user", Content: "Analyze this: {{input \"transcript\"}}"},
+			},
+		}
+
+		_, err := renderer.Render(ctx, def, map[string]*domain.Artifact{}, vars)
+		if !errors.Is(err, ErrMissingRequiredInput) {
+			t.Fatalf("expected ErrMissingRequiredInput, got %v", err)
+		}
+	})
+
+	t.Run("invalid template syntax", func(t *testing.T) {
+		def := &domain.PromptDefinition{
+			Inputs: []domain.PromptInput{{Name: "transcript", Required: true}},
+			Templates: []domain.PromptMessageTemplate{
+				{Role: "user", Content: "Hello {{.unclosed"},
+			},
+		}
+
+		_, err := renderer.Render(ctx, def, inputs, vars)
+		if !errors.Is(err, ErrInvalidTemplate) {
+			t.Fatalf("expected ErrInvalidTemplate, got %v", err)
+		}
+	})
+
+	t.Run("unknown input reference", func(t *testing.T) {
+		def := &domain.PromptDefinition{
+			Inputs: []domain.PromptInput{{Name: "transcript", Required: true}},
+			Templates: []domain.PromptMessageTemplate{
+				{Role: "user", Content: "Hello {{input \"ghost\"}}"},
+			},
+		}
+
+		_, err := renderer.Render(ctx, def, inputs, vars)
+		if !errors.Is(err, ErrRenderFailure) {
+			t.Fatalf("expected ErrRenderFailure, got %v", err)
+		}
+		if !errors.Is(err, ErrUnknownInput) {
+			t.Fatalf("expected ErrUnknownInput, got %v", err)
+		}
+	})
+
+	t.Run("empty message role", func(t *testing.T) {
+		def := &domain.PromptDefinition{
+			Inputs: []domain.PromptInput{{Name: "transcript", Required: true}},
+			Templates: []domain.PromptMessageTemplate{
+				{Role: "", Content: "Hello"},
+			},
+		}
+		_, err := renderer.Render(ctx, def, inputs, vars)
+		if !errors.Is(err, ErrInvalidMessageRole) {
+			t.Fatalf("expected ErrInvalidMessageRole, got %v", err)
+		}
+	})
+}