Implement resume, skip, and stage selection

internal/app/resume.go

@@ -2,10 +2,90 @@ package app
 
 import (
 	"context"
+	"flag"
+	"fmt"
 	"io"
+
+	"gitea.maximumdirect.net/eric/narratio/internal/config"
+	"gitea.maximumdirect.net/eric/narratio/internal/manifest"
 )
 
-// Resume is a placeholder for future resume-from-manifest behavior.
-func Resume(_ context.Context, _ []string, out io.Writer) error {
-	return placeholder(out, "resume")
+// Resume continues execution from the first non-succeeded stage in the manifest.
+func Resume(ctx context.Context, args []string, out io.Writer) error {
+	fs := flag.NewFlagSet("resume", flag.ContinueOnError)
+	fs.SetOutput(io.Discard)
+
+	var pipelinePath string
+	var sessionPath string
+	var force bool
+	fs.StringVar(&pipelinePath, "config", "", "path to pipeline.yml")
+	fs.StringVar(&sessionPath, "session", "", "path to session.yml")
+	fs.BoolVar(&force, "force", false, "force stage execution")
+
+	if err := fs.Parse(args); err != nil {
+		return fmt.Errorf("resume: invalid flags: %w", err)
+	}
+	if fs.NArg() != 0 {
+		return fmt.Errorf("resume: unexpected positional arguments")
+	}
+	if pipelinePath == "" || sessionPath == "" {
+		return fmt.Errorf("resume: --config and --session are required")
+	}
+
+	cfg, err := config.Load(pipelinePath, sessionPath)
+	if err != nil {
+		return fmt.Errorf("resume: %w", err)
+	}
+	if err := config.Validate(cfg); err != nil {
+		return fmt.Errorf("resume: %w", err)
+	}
+
+	full := BuildFullPlan()
+	selected := full
+	if !force {
+		m, err := loadManifestIfPresent(ctx, cfg)
+		if err != nil {
+			return fmt.Errorf("resume: %w", err)
+		}
+		if m != nil {
+			start := firstNonSucceededIndex(full, m)
+			if start >= len(full) {
+				_, err := fmt.Fprintf(out, "narratio resume: session %s has no remaining stages\n", cfg.Session.SessionID)
+				return err
+			}
+			selected = full[start:]
+		}
+	}
+
+	summary, err := executeStages(ctx, cfg, selected, RunOptions{Force: force})
+	if err != nil {
+		return fmt.Errorf("resume: %w", err)
+	}
+
+	_, err = fmt.Fprintf(
+		out,
+		"narratio resume: session %s; executed=%d skipped=%d; manifest=%s\n",
+		summary.SessionID,
+		len(summary.Executed),
+		len(summary.Skipped),
+		summary.ManifestPath,
+	)
+	return err
+}
+
+func loadManifestIfPresent(ctx context.Context, cfg *config.Config) (*manifest.Manifest, error) {
+	path := manifestPathFor(cfg)
+	exists, err := fileExists(path)
+	if err != nil {
+		return nil, fmt.Errorf("check manifest %q: %w", path, err)
+	}
+	if !exists {
+		return nil, nil
+	}
+	store := &manifest.LocalStore{}
+	m, err := store.Load(ctx, path)
+	if err != nil {
+		return nil, fmt.Errorf("load manifest %q: %w", path, err)
+	}
+	return m, nil
 }