package secret

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

// DetermineStateDir determines the state directory based on environment
// variables and OS.
// It returns an error if no usable directory can be determined.
func DetermineStateDir(customConfigDir string) (string, error) {
	// Check for environment variable first
	if envStateDir := os.Getenv(EnvStateDir); envStateDir != "" {
		return envStateDir, nil
	}

	// Use custom config dir if provided
	if customConfigDir != "" {
		return filepath.Join(customConfigDir, AppID), nil
	}

	// Use os.UserConfigDir() which handles platform-specific directories:
	// - On Unix systems, it returns $XDG_CONFIG_HOME or $HOME/.config
	// - On Darwin, it returns $HOME/Library/Application Support
	// - On Windows, it returns %AppData%
	configDir, err := os.UserConfigDir()
	if err != nil {
		// Fallback to a reasonable default if we can't determine user config dir
		homeDir, homeErr := os.UserHomeDir()
		if homeErr != nil {
			return "", fmt.Errorf(
				"unable to determine state directory: config dir: %w, home dir: %w",
				err, homeErr)
		}

		fallbackDir := filepath.Join(homeDir, ".config", AppID)
		Warn("Could not determine user config directory, falling back to default",
			"fallback", fallbackDir, "error", err)

		return fallbackDir, nil
	}

	return filepath.Join(configDir, AppID), nil
}