/**
 * Storage Library for Financial Insight System
 * Provides a unified interface for data storage with potential for external storage integration
 */

// Define storage keys for better type safety and avoid string duplication
export const STORAGE_KEYS = {
  CHATS: 'fis-chats',
  SETTINGS: 'fis-settings',
  API_ENDPOINT: 'apiEndpoint',
  THEME: 'fis-theme',
  SOURCES: 'fis-sources',
  PROFILE_STORAGE_KEY: 'fis-profile'
} as const;

// Types for our storage
export interface StorageOptions {
  ttl?: number; // Time to live in milliseconds
}

export type StorageValue = string | object | number | boolean | null | undefined;

/**
 * Storage service that provides unified interface for storing and retrieving data
 * Currently uses localStorage, but can be extended to use external storage in the future
 */
class StorageService {
  private defaults: Partial<Record<string, StorageValue>> = {};

  // Set default values for storage keys
  setDefaults(defaults: Partial<Record<string, StorageValue>>) {
    this.defaults = defaults;
  }

  // Get item from storage with automatic parsing and default fallback
  get<T = any>(key: string): T | null {
    try {
      const item = localStorage.getItem(key);
      if (!item) {
        // Return default if available
        if (key in this.defaults) {
          return this.defaults[key] as T;
        }
        return null;
      }
      const { value, expires } = JSON.parse(item);
      if (expires && expires < Date.now()) {
        this.remove(key);
        // Return default if available
        if (key in this.defaults) {
          return this.defaults[key] as T;
        }
        return null;
      }
      return value as T;
    } catch (error) {
      console.error(`Error getting item from storage: ${key}`, error);
      // Return default if available
      if (key in this.defaults) {
        return this.defaults[key] as T;
      }
      return null;
    }
  }

  // Set item in storage with optional TTL
  set(key: string, value: StorageValue, options: StorageOptions = {}): boolean {
    try {
      const storageItem = {
        value,
        expires: options.ttl ? Date.now() + options.ttl : null
      };
      
      localStorage.setItem(key, JSON.stringify(storageItem));
      return true;
    } catch (error) {
      console.error(`Error setting item in storage: ${key}`, error);
      return false;
    }
  }

  // Remove item from storage
  remove(key: string): boolean {
    try {
      localStorage.removeItem(key);
      return true;
    } catch (error) {
      console.error(`Error removing item from storage: ${key}`, error);
      return false;
    }
  }

  // Check if key exists in storage
  has(key: string): boolean {
    return localStorage.getItem(key) !== null;
  }

  // Clear all storage for the application
  clear(): boolean {
    try {
      // Only clear keys that start with our application prefix (fis-)
      Object.keys(localStorage).forEach(key => {
        if (key.startsWith('fis-')) {
          localStorage.removeItem(key);
        }
      });
      return true;
    } catch (error) {
      console.error('Error clearing storage', error);
      return false;
    }
  }

  /**
   * Export all application data for keys defined in STORAGE_KEYS as a JSON object.
   * Returns an object with key-value pairs.
   */
  export(): Record<string, any> {
    const exported: Record<string, any> = {};
    Object.values(STORAGE_KEYS).forEach(key => {
      try {
        const item = localStorage.getItem(key);
        if (item) {
          exported[key] = JSON.parse(item);
        }
      } catch (error) {
        console.error(`Error exporting key: ${key}`, error);
      }
    });
    return exported;
  }

  /**
   * Import data from an external source into local storage.
   * Accepts an object with key-value pairs (as produced by export()).
   * Overwrites existing keys, but only those defined in STORAGE_KEYS.
   */
  import(data: Record<string, any>): boolean {
    try {
      Object.entries(data).forEach(([key, value]) => {
        if (Object.values(STORAGE_KEYS).includes(key as any)) {
          localStorage.setItem(key, JSON.stringify(value));
        }
      });
      return true;
    } catch (error) {
      console.error('Error importing data into storage', error);
      return false;
    }
  }

  // Reset all keys to their default values
  resetToDefaults(): boolean {
    try {
      Object.entries(this.defaults).forEach(([key, value]) => {
        this.set(key, value);
      });
      return true;
    } catch (error) {
      console.error('Error resetting storage to defaults', error);
      return false;
    }
  }
}

// Create and export a singleton instance
export const storage = new StorageService();
storage.setDefaults({
  [STORAGE_KEYS.CHATS]: [],
  [STORAGE_KEYS.SETTINGS]: {},
  [STORAGE_KEYS.API_ENDPOINT]: "https://insight-ai-api.hf.space",
  [STORAGE_KEYS.THEME]: "dark",
  [STORAGE_KEYS.SOURCES]: [],
});