Implement manifest model and local store

internal/manifest/store.go

@@ -2,26 +2,173 @@ package manifest
 
 import (
 	"context"
+	"encoding/json"
 	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+	"time"
 )
 
-// Store is a placeholder interface for manifest persistence.
+// Store persists manifests to and from durable storage.
 type Store interface {
-	Load(ctx context.Context, sessionID string) (*Manifest, error)
-	Save(ctx context.Context, m *Manifest) error
+	Create(ctx context.Context, sessionID string) (*Manifest, error)
+	Load(ctx context.Context, path string) (*Manifest, error)
+	Save(ctx context.Context, path string, m *Manifest) error
 }
 
-// LocalStore is a placeholder local-filesystem manifest store.
-type LocalStore struct {
-	RootDir string
+// LocalStore stores manifests as JSON on the local filesystem.
+type LocalStore struct{}
+
+// Create returns a new in-memory manifest for a session.
+func (s *LocalStore) Create(ctx context.Context, sessionID string) (*Manifest, error) {
+	if err := checkContext(ctx); err != nil {
+		return nil, err
+	}
+	if strings.TrimSpace(sessionID) == "" {
+		return nil, fmt.Errorf("create manifest: sessionID is required")
+	}
+
+	now := time.Now().UTC()
+	return New(sessionID, now), nil
 }
 
-// Load returns a not-yet-implemented error in the scaffold.
-func (s *LocalStore) Load(_ context.Context, _ string) (*Manifest, error) {
-	return nil, fmt.Errorf("manifest local load: not yet implemented")
+// Load reads and validates a local JSON manifest from path.
+func (s *LocalStore) Load(ctx context.Context, path string) (*Manifest, error) {
+	if err := checkContext(ctx); err != nil {
+		return nil, err
+	}
+	if strings.TrimSpace(path) == "" {
+		return nil, fmt.Errorf("load manifest: path is required")
+	}
+
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return nil, fmt.Errorf("load manifest %q: %w", path, err)
+	}
+
+	var m Manifest
+	if err := json.Unmarshal(data, &m); err != nil {
+		return nil, fmt.Errorf("decode manifest %q: %w", path, err)
+	}
+
+	if err := validateLoadedManifest(&m); err != nil {
+		return nil, fmt.Errorf("manifest %q invalid: %w", path, err)
+	}
+	normalizeManifest(&m)
+
+	return &m, nil
 }
 
-// Save returns a not-yet-implemented error in the scaffold.
-func (s *LocalStore) Save(_ context.Context, _ *Manifest) error {
-	return fmt.Errorf("manifest local save: not yet implemented")
+// Save writes the manifest to path atomically via temp file + rename.
+func (s *LocalStore) Save(ctx context.Context, path string, m *Manifest) error {
+	if err := checkContext(ctx); err != nil {
+		return err
+	}
+	if strings.TrimSpace(path) == "" {
+		return fmt.Errorf("save manifest: path is required")
+	}
+	if m == nil {
+		return fmt.Errorf("save manifest: manifest is nil")
+	}
+	if strings.TrimSpace(m.SessionID) == "" {
+		return fmt.Errorf("save manifest: session_id is required")
+	}
+	if m.CreatedAt.IsZero() {
+		return fmt.Errorf("save manifest: created_at is required")
+	}
+
+	m.UpdatedAt = time.Now().UTC()
+	if m.Stages == nil {
+		m.Stages = map[string]*StageRecord{}
+	}
+
+	data, err := json.MarshalIndent(m, "", "  ")
+	if err != nil {
+		return fmt.Errorf("save manifest: marshal: %w", err)
+	}
+	data = append(data, '\n')
+
+	dir := filepath.Dir(path)
+	if err := os.MkdirAll(dir, 0o755); err != nil {
+		return fmt.Errorf("save manifest: create directory %q: %w", dir, err)
+	}
+
+	tmp, err := os.CreateTemp(dir, ".manifest.json.tmp-*")
+	if err != nil {
+		return fmt.Errorf("save manifest: create temp file: %w", err)
+	}
+	tmpName := tmp.Name()
+	removeTmp := true
+	defer func() {
+		if removeTmp {
+			_ = os.Remove(tmpName)
+		}
+	}()
+
+	if _, err := tmp.Write(data); err != nil {
+		_ = tmp.Close()
+		return fmt.Errorf("save manifest: write temp file: %w", err)
+	}
+	if err := tmp.Sync(); err != nil {
+		_ = tmp.Close()
+		return fmt.Errorf("save manifest: sync temp file: %w", err)
+	}
+	if err := tmp.Close(); err != nil {
+		return fmt.Errorf("save manifest: close temp file: %w", err)
+	}
+	if err := checkContext(ctx); err != nil {
+		return err
+	}
+
+	if err := os.Rename(tmpName, path); err != nil {
+		return fmt.Errorf("save manifest: rename temp file: %w", err)
+	}
+	removeTmp = false
+
+	return nil
+}
+
+func validateLoadedManifest(m *Manifest) error {
+	if m == nil {
+		return fmt.Errorf("manifest is nil")
+	}
+	if strings.TrimSpace(m.SessionID) == "" {
+		return fmt.Errorf("session_id is required")
+	}
+	if m.CreatedAt.IsZero() {
+		return fmt.Errorf("created_at is required")
+	}
+	if m.UpdatedAt.IsZero() {
+		return fmt.Errorf("updated_at is required")
+	}
+
+	return nil
+}
+
+func normalizeManifest(m *Manifest) {
+	if m.Stages == nil {
+		m.Stages = map[string]*StageRecord{}
+	}
+	for name, stage := range m.Stages {
+		if stage == nil {
+			stage = &StageRecord{Name: name, Status: StatusPending, CreatedAt: m.CreatedAt, UpdatedAt: m.UpdatedAt}
+			m.Stages[name] = stage
+		}
+		if stage.Name == "" {
+			stage.Name = name
+		}
+	}
+}
+
+func checkContext(ctx context.Context) error {
+	if ctx == nil {
+		return nil
+	}
+	select {
+	case <-ctx.Done():
+		return ctx.Err()
+	default:
+		return nil
+	}
 }