Add configurable sequence numbering command

internal/sequence/traversal.go

@@ -0,0 +1,92 @@
+package sequence
+
+import (
+	"context"
+	"errors"
+	"io/fs"
+	"path/filepath"
+	"strings"
+
+	"github.com/rogeecn/renamer/internal/traversal"
+)
+
+type traversalCandidate struct {
+	RelativePath string
+	AbsolutePath string
+	Stem         string
+	Extension    string
+	IsDir        bool
+	Depth        int
+}
+
+func collectTraversalCandidates(ctx context.Context, opts Options) ([]traversalCandidate, error) {
+	if opts.WorkingDir == "" {
+		return nil, errors.New("working directory must be provided")
+	}
+
+	absRoot, err := filepath.Abs(opts.WorkingDir)
+	if err != nil {
+		return nil, err
+	}
+
+	walker := traversal.NewWalker()
+
+	allowedExts := make(map[string]struct{}, len(opts.Extensions))
+	for _, ext := range opts.Extensions {
+		lower := strings.ToLower(ext)
+		allowedExts[lower] = struct{}{}
+	}
+
+	candidates := make([]traversalCandidate, 0)
+
+	emit := func(relPath string, entry fs.DirEntry, depth int) error {
+		select {
+		case <-ctx.Done():
+			return ctx.Err()
+		default:
+		}
+
+		// Skip the root placeholder emitted by the walker when include dirs is true.
+		if relPath == "." {
+			return nil
+		}
+
+		relSlash := filepath.ToSlash(relPath)
+		absolute := filepath.Join(absRoot, relPath)
+		candidate := traversalCandidate{
+			RelativePath: relSlash,
+			AbsolutePath: absolute,
+			IsDir:        entry.IsDir(),
+			Depth:        depth,
+		}
+
+		if !entry.IsDir() {
+			rawExt := filepath.Ext(entry.Name())
+			lowerExt := strings.ToLower(rawExt)
+			if len(allowedExts) > 0 {
+				if _, ok := allowedExts[lowerExt]; !ok {
+					return nil
+				}
+			}
+
+			candidate.Extension = rawExt
+			stem := entry.Name()
+			if rawExt != "" {
+				stem = strings.TrimSuffix(stem, rawExt)
+			}
+			candidate.Stem = stem
+		} else {
+			candidate.Stem = entry.Name()
+		}
+
+		candidates = append(candidates, candidate)
+		return nil
+	}
+
+	err = walker.Walk(absRoot, opts.Recursive, opts.IncludeDirectories, opts.IncludeHidden, 0, emit)
+	if err != nil {
+		return nil, err
+	}
+
+	return candidates, nil
+}