Add regex command implementation

tests/integration/regex_flow_test.go

@@ -0,0 +1,74 @@
+package integration
+
+import (
+	"bytes"
+	"io/fs"
+	"os"
+	"path/filepath"
+	"testing"
+
+	renamercmd "github.com/rogeecn/renamer/cmd"
+)
+
+func TestRegexPreviewCommand(t *testing.T) {
+	t.Parallel()
+
+	tmp := t.TempDir()
+	copyRegexFixtureIntegration(t, "baseline", tmp)
+
+	var out bytes.Buffer
+	cmd := renamercmd.NewRootCommand()
+	cmd.SetOut(&out)
+	cmd.SetErr(&out)
+	cmd.SetArgs([]string{"regex", "^(\\w+)-(\\d+)", "@2_@1", "--dry-run", "--path", tmp})
+
+	if err := cmd.Execute(); err != nil {
+		t.Fatalf("regex preview command failed: %v\noutput: %s", err, out.String())
+	}
+
+	expected := []string{
+		"alpha-123.log -> 123_alpha.log",
+		"beta-456.log -> 456_beta.log",
+		"gamma-789.log -> 789_gamma.log",
+		"Preview complete: 3 matched, 3 changed, 0 skipped.",
+		"Preview complete. Re-run with --yes to apply.",
+	}
+
+	for _, token := range expected {
+		if !bytes.Contains(out.Bytes(), []byte(token)) {
+			t.Fatalf("expected output to contain %q, got: %s", token, out.String())
+		}
+	}
+}
+
+func copyRegexFixtureIntegration(t *testing.T, name, dest string) {
+	t.Helper()
+	src := filepath.Join("..", "fixtures", "regex", name)
+	if err := filepath.WalkDir(src, func(path string, d fs.DirEntry, err error) error {
+		if err != nil {
+			return err
+		}
+		if d.IsDir() {
+			return nil
+		}
+
+		rel, err := filepath.Rel(src, path)
+		if err != nil {
+			return err
+		}
+
+		targetPath := filepath.Join(dest, rel)
+		if err := os.MkdirAll(filepath.Dir(targetPath), 0o755); err != nil {
+			return err
+		}
+
+		content, err := os.ReadFile(path)
+		if err != nil {
+			return err
+		}
+
+		return os.WriteFile(targetPath, content, 0o644)
+	}); err != nil {
+		t.Fatalf("copy regex fixture: %v", err)
+	}
+}