introduce a persistent config

config/paths.go

@@ -0,0 +1,72 @@
+package config
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+)
+
+// This file centralizes all path-related helpers for the config package.
+// It standardizes where PMG stores configuration and related artifacts,
+// so other packages (e.g., internal/alias) can rely on a single source of truth.
+
+const (
+	pmgConfigName = "config"
+	pmgConfigType = "yml"
+	pmgConfigPath = "safedep/pmg"
+)
+
+// defaultRcFileName is the default name for the shell RC file that contains PMG aliases.
+const defaultRcFileName = ".pmg.rc"
+
+// PmgConfigDir returns the base application config directory.
+// By default, this is:
+// - macOS:   ~/Library/Application Support/safedep/pmg
+// - Linux:   ~/.config/safedep/pmg
+// - Windows: %AppData%\safedep\pmg
+func PmgConfigDir() (string, error) {
+	userConfigDir, err := os.UserConfigDir()
+	if err != nil {
+		return "", fmt.Errorf("failed to retrieve user config directory: %w", err)
+	}
+
+	return filepath.Join(userConfigDir, pmgConfigPath), nil
+}
+
+// CreatePmgConfigDir ensures the application config directory exists and returns its path.
+func CreatePmgConfigDir() (string, error) {
+	dir, err := PmgConfigDir()
+	if err != nil {
+		return "", err
+	}
+
+	if err := os.MkdirAll(dir, 0o755); err != nil {
+		return "", fmt.Errorf("failed to create config directory %s: %w", dir, err)
+	}
+	return dir, nil
+}
+
+// ConfigFilePath returns the absolute path to the main PMG config file (e.g., config.yml),
+// without creating any directories.
+func ConfigFilePath() (string, error) {
+	dir, err := PmgConfigDir()
+	if err != nil {
+		return "", err
+	}
+	return filepath.Join(dir, fmt.Sprintf("%s.%s", pmgConfigName, pmgConfigType)), nil
+}
+
+// RcFileName returns the default RC file name used for PMG aliases.
+func RcFileName() string {
+	return defaultRcFileName
+}
+
+// RcFilePath returns the absolute path to the PMG RC file under the app config directory,
+// without creating any directories.
+func RcFilePath() (string, error) {
+	dir, err := PmgConfigDir()
+	if err != nil {
+		return "", err
+	}
+	return filepath.Join(dir, defaultRcFileName), nil
+}