package core

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

// ConfigManager handles saving/loading VPN configs to disk.
type ConfigManager struct {
	configFilePath string
}

// NewConfigManager creates a new ConfigManager with config file under %APPDATA%/kettuRay.
func NewConfigManager() (*ConfigManager, error) {
	appData, err := os.UserConfigDir()
	if err != nil {
		return nil, fmt.Errorf("failed to get app data dir: %w", err)
	}

	appDir := filepath.Join(appData, "kettuRay")
	if err := os.MkdirAll(appDir, 0o755); err != nil {
		return nil, fmt.Errorf("failed to create app dir: %w", err)
	}

	return &ConfigManager{
		configFilePath: filepath.Join(appDir, "configs.json"),
	}, nil
}

// LoadConfigs loads saved VPN configs from disk.
func (m *ConfigManager) LoadConfigs() ([]VpnConfig, error) {
	data, err := os.ReadFile(m.configFilePath)
	if err != nil {
		if os.IsNotExist(err) {
			return make([]VpnConfig, 0), nil
		}
		return nil, err
	}

	var configs []VpnConfig
	if len(data) == 0 {
		return make([]VpnConfig, 0), nil
	}
	if err := json.Unmarshal(data, &configs); err != nil {
		fmt.Printf("Error parsing configs.json: %v\n", err)
		// return empty slice but still error so app knows it failed
		return make([]VpnConfig, 0), err
	}
	return configs, nil
}

// SaveConfigs writes VPN configs to disk.
func (m *ConfigManager) SaveConfigs(configs []VpnConfig) error {
	data, err := json.MarshalIndent(configs, "", "  ")
	if err != nil {
		return fmt.Errorf("failed to marshal configs: %w", err)
	}
	return os.WriteFile(m.configFilePath, data, 0o644)
}