package platform

import (
	"os"
	"path/filepath"
	"runtime"
)

// DefaultDataDir returns the OS-appropriate default data directory when the
// user has not configured one. It never returns an empty path; on failure it
// falls back to a relative "./data" directory.
func DefaultDataDir() string {
	home, err := os.UserHomeDir()
	if err != nil {
		return filepath.Join(".", "data")
	}

	switch runtime.GOOS {
	case "windows":
		if appdata := os.Getenv("APPDATA"); appdata != "" {
			return filepath.Join(appdata, "Cyrene")
		}
		return filepath.Join(home, "AppData", "Roaming", "Cyrene")
	case "darwin":
		return filepath.Join(home, "Library", "Application Support", "Cyrene")
	default:
		if xdg := os.Getenv("XDG_DATA_HOME"); xdg != "" {
			return filepath.Join(xdg, "cyrene")
		}
		return filepath.Join(home, ".local", "share", "cyrene")
	}
}