Add regex command implementation

internal/regex/request.go

@@ -0,0 +1,69 @@
+package regex
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+	"time"
+)
+
+// Request captures the inputs required to evaluate regex-based rename operations.
+type Request struct {
+	WorkingDir         string
+	Pattern            string
+	Template           string
+	IncludeDirectories bool
+	Recursive          bool
+	IncludeHidden      bool
+	Extensions         []string
+	DryRun             bool
+	AutoConfirm        bool
+	Timestamp          time.Time
+}
+
+// NewRequest constructs a Request with the supplied working directory and defaults the
+// timestamp to the current UTC time. Additional fields should be set by the caller.
+func NewRequest(workingDir string) Request {
+	return Request{
+		WorkingDir: workingDir,
+		Timestamp:  time.Now().UTC(),
+	}
+}
+
+// Validate ensures the request has usable defaults and a resolvable working directory.
+func (r *Request) Validate() error {
+	if r == nil {
+		return errors.New("regex request cannot be nil")
+	}
+
+	if r.Pattern == "" {
+		return errors.New("regex pattern is required")
+	}
+
+	if r.WorkingDir == "" {
+		cwd, err := os.Getwd()
+		if err != nil {
+			return fmt.Errorf("determine working directory: %w", err)
+		}
+		r.WorkingDir = cwd
+	}
+
+	if !filepath.IsAbs(r.WorkingDir) {
+		abs, err := filepath.Abs(r.WorkingDir)
+		if err != nil {
+			return fmt.Errorf("resolve working directory: %w", err)
+		}
+		r.WorkingDir = abs
+	}
+
+	info, err := os.Stat(r.WorkingDir)
+	if err != nil {
+		return fmt.Errorf("stat working directory: %w", err)
+	}
+	if !info.IsDir() {
+		return fmt.Errorf("working directory %q is not a directory", r.WorkingDir)
+	}
+
+	return nil
+}