Add regex command implementation

internal/regex/traversal.go

@@ -0,0 +1,86 @@
+package regex
+
+import (
+	"context"
+	"io/fs"
+	"path/filepath"
+	"strings"
+
+	"github.com/rogeecn/renamer/internal/traversal"
+)
+
+// Candidate represents a file or directory subject to regex evaluation.
+type Candidate struct {
+	RelativePath string
+	OriginalPath string
+	BaseName     string
+	Stem         string
+	Extension    string
+	IsDir        bool
+	Depth        int
+}
+
+// TraverseCandidates walks the working directory and invokes fn for each eligible candidate.
+func TraverseCandidates(ctx context.Context, req *Request, 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()
+			name := entry.Name()
+			stem := name
+			ext := ""
+			if !isDir {
+				if dot := strings.IndexRune(name, '.'); dot > 0 {
+					ext = name[dot:]
+					stem = name[:dot]
+				}
+
+				if len(extensions) > 0 {
+					lower := strings.ToLower(ext)
+					if _, ok := extensions[lower]; !ok {
+						return nil
+					}
+				}
+			}
+
+			rel := filepath.ToSlash(relPath)
+			if rel == "." {
+				return nil
+			}
+
+			candidate := Candidate{
+				RelativePath: rel,
+				OriginalPath: filepath.Join(req.WorkingDir, relPath),
+				BaseName:     name,
+				Stem:         stem,
+				Extension:    ext,
+				IsDir:        isDir,
+				Depth:        depth,
+			}
+
+			return fn(candidate)
+		},
+	)
+}