/**
 * Cache utilities for Pages application
 * Provides centralized cache management with proper invalidation
 */

interface CacheEntry<T> {
  data: T;
  timestamp: number;
}

interface CacheConfig {
  ttl: number; // Time to live in milliseconds
  keyPrefix: string;
}

class CacheManager {
  private memoryCache: Map<string, CacheEntry<any>> = new Map();
  private config: CacheConfig;

  constructor(config: CacheConfig) {
    this.config = config;
  }

  /**
   * Get data from cache (memory first, then localStorage)
   */
  get<T>(key: string): T | null {
    const fullKey = `${this.config.keyPrefix}${key}`;
    
    // Check memory cache first
    const memoryEntry = this.memoryCache.get(fullKey);
    if (memoryEntry && this.isValid(memoryEntry.timestamp)) {
      return memoryEntry.data as T;
    }

    // Check localStorage
    try {
      const stored = localStorage.getItem(fullKey);
      if (stored) {
        const entry: CacheEntry<T> = JSON.parse(stored);
        if (this.isValid(entry.timestamp)) {
          // Update memory cache
          this.memoryCache.set(fullKey, entry);
          return entry.data;
        } else {
          // Expired, remove it
          localStorage.removeItem(fullKey);
        }
      }
    } catch (error) {
      console.error('Error reading from localStorage cache:', error);
    }

    return null;
  }

  /**
   * Set data in cache (both memory and localStorage)
   */
  set<T>(key: string, data: T): void {
    const fullKey = `${this.config.keyPrefix}${key}`;
    const entry: CacheEntry<T> = {
      data,
      timestamp: Date.now()
    };

    // Update memory cache
    this.memoryCache.set(fullKey, entry);

    // Update localStorage
    try {
      localStorage.setItem(fullKey, JSON.stringify(entry));
    } catch (error) {
      console.error('Error writing to localStorage cache:', error);
      // If localStorage is full, try to clear old entries
      this.clearExpired();
    }
  }

  /**
   * Remove specific cache entry
   */
  remove(key: string): void {
    const fullKey = `${this.config.keyPrefix}${key}`;
    
    // Remove from memory
    this.memoryCache.delete(fullKey);

    // Remove from localStorage
    try {
      localStorage.removeItem(fullKey);
    } catch (error) {
      console.error('Error removing from localStorage cache:', error);
    }
  }

  /**
   * Clear all cache entries matching a pattern
   */
  clearPattern(pattern: string): void {
    const fullPattern = `${this.config.keyPrefix}${pattern}`;
    
    // Clear from memory
    for (const key of this.memoryCache.keys()) {
      if (key.includes(fullPattern)) {
        this.memoryCache.delete(key);
      }
    }

    // Clear from localStorage
    try {
      const keysToRemove: string[] = [];
      for (let i = 0; i < localStorage.length; i++) {
        const key = localStorage.key(i);
        if (key && key.includes(fullPattern)) {
          keysToRemove.push(key);
        }
      }
      keysToRemove.forEach(key => localStorage.removeItem(key));
    } catch (error) {
      console.error('Error clearing pattern from localStorage cache:', error);
    }
  }

  /**
   * Clear all expired entries
   */
  clearExpired(): void {
    const now = Date.now();
    
    // Clear from memory
    for (const [key, entry] of this.memoryCache.entries()) {
      if (!this.isValid(entry.timestamp)) {
        this.memoryCache.delete(key);
      }
    }

    // Clear from localStorage
    try {
      const keysToRemove: string[] = [];
      for (let i = 0; i < localStorage.length; i++) {
        const key = localStorage.key(i);
        if (key && key.startsWith(this.config.keyPrefix)) {
          try {
            const entry: CacheEntry<any> = JSON.parse(localStorage.getItem(key) || '{}');
            if (!this.isValid(entry.timestamp)) {
              keysToRemove.push(key);
            }
          } catch {
            // Invalid entry, remove it
            keysToRemove.push(key);
          }
        }
      }
      keysToRemove.forEach(key => localStorage.removeItem(key));
    } catch (error) {
      console.error('Error clearing expired entries from localStorage:', error);
    }
  }

  /**
   * Clear all cache
   */
  clearAll(): void {
    this.memoryCache.clear();
    
    try {
      const keysToRemove: string[] = [];
      for (let i = 0; i < localStorage.length; i++) {
        const key = localStorage.key(i);
        if (key && key.startsWith(this.config.keyPrefix)) {
          keysToRemove.push(key);
        }
      }
      keysToRemove.forEach(key => localStorage.removeItem(key));
    } catch (error) {
      console.error('Error clearing all from localStorage cache:', error);
    }
  }

  /**
   * Check if cache entry is still valid
   */
  private isValid(timestamp: number): boolean {
    return (Date.now() - timestamp) < this.config.ttl;
  }
}

// Export cache managers for different use cases
export const notesCache = new CacheManager({
  ttl: 2 * 60 * 1000, // 2 minutes (reduced from 5 to ensure fresh data)
  keyPrefix: 'notes-cache-'
});

export const noteContentCache = new CacheManager({
  ttl: 15 * 60 * 1000, // 15 minutes
  keyPrefix: 'note-content-'
});

export const foldersCache = new CacheManager({
  ttl: 2 * 60 * 1000, // 2 minutes
  keyPrefix: 'nextcloud_folders'
});

/**
 * Invalidate cache for a specific folder
 */
export function invalidateFolderCache(userId: string, folder: string): void {
  const folderLowercase = folder.toLowerCase();
  const cacheKey = `${userId}-${folderLowercase}`;
  
  // Clear notes list cache
  const hadCache = notesCache.get(cacheKey) !== null;
  notesCache.remove(cacheKey);
  
  // Clear all note content caches for this folder (pattern match)
  noteContentCache.clearPattern(`user-${userId}/${folderLowercase}/`);
  
  console.log(`[invalidateFolderCache] Cache invalidated for folder: ${folderLowercase} (had cache: ${hadCache})`);
  
  // Double-check that cache is cleared
  const stillCached = notesCache.get(cacheKey);
  if (stillCached) {
    console.warn(`[invalidateFolderCache] WARNING: Cache still exists after removal for ${cacheKey}`);
    // Force clear all matching keys
    notesCache.clearPattern(cacheKey);
  }
}

/**
 * Invalidate cache for a specific note
 */
export function invalidateNoteCache(noteId: string): void {
  noteContentCache.remove(noteId);
  console.log(`Cache invalidated for note: ${noteId}`);
}

/**
 * Clear all caches for a user
 */
export function clearUserCache(userId: string): void {
  notesCache.clearPattern(userId);
  noteContentCache.clearPattern(`user-${userId}/`);
  foldersCache.clearAll();
  console.log(`All caches cleared for user: ${userId}`);
}