feat: add replace subcommand with multi-pattern support

internal/replace/traversal.go

@@ -0,0 +1,73 @@
+package replace
+
+import (
+	"context"
+	"io/fs"
+	"path/filepath"
+	"strings"
+
+	"github.com/rogeecn/renamer/internal/traversal"
+)
+
+// Candidate represents a file or directory that may be renamed.
+type Candidate struct {
+	RelativePath string
+	OriginalPath string
+	BaseName     string
+	IsDir        bool
+	Depth        int
+}
+
+// TraverseCandidates walks the working directory according to the request scope and invokes fn for
+// every eligible candidate (files by default, directories when IncludeDirectories is true).
+func TraverseCandidates(ctx context.Context, req *ReplaceRequest, fn func(Candidate) error) error {
+	if err := req.Validate(); err != nil {
+		return err
+	}
+
+	extensions := make(map[string]struct{}, len(req.Extensions))
+	for _, ext := range req.Extensions {
+		lower := strings.ToLower(ext)
+		extensions[lower] = struct{}{}
+	}
+
+	walker := traversal.NewWalker()
+
+	return walker.Walk(
+		req.WorkingDir,
+		req.Recursive,
+		req.IncludeDirectories,
+		req.IncludeHidden,
+		0,
+		func(relPath string, entry fs.DirEntry, depth int) error {
+			select {
+			case <-ctx.Done():
+				return ctx.Err()
+			default:
+			}
+
+			isDir := entry.IsDir()
+			ext := strings.ToLower(filepath.Ext(entry.Name()))
+
+			if !isDir && len(extensions) > 0 {
+				if _, ok := extensions[ext]; !ok {
+					return nil
+				}
+			}
+
+			candidate := Candidate{
+				RelativePath: filepath.ToSlash(relPath),
+				OriginalPath: filepath.Join(req.WorkingDir, relPath),
+				BaseName:     entry.Name(),
+				IsDir:        isDir,
+				Depth:        depth,
+			}
+
+			if candidate.RelativePath == "." {
+				return nil
+			}
+
+			return fn(candidate)
+		},
+	)
+}