// Local user authentication and storage system
interface UserProfile {
  id: string;
  name: string;
  phone: string;
  organization?: string;
  role: 'engineer' | 'student' | 'researcher' | 'government' | 'farmer' | 'consultant';
  lastLogin: Date;
  createdAt: Date;
}

interface UserSession {
  user: UserProfile;
  loginTime: Date;
  isActive: boolean;
}

class UserStorageManager {
  private storageKey = 'prithvi_users';
  private sessionKey = 'prithvi_session';
  private currentSession: UserSession | null = null;

  // Get all users from localStorage
  private getUsers(): UserProfile[] {
    try {
      const stored = localStorage.getItem(this.storageKey);
      return stored ? JSON.parse(stored) : [];
    } catch (error) {
      console.warn('Could not load users from storage:', error);
      return [];
    }
  }

  // Save users to localStorage
  private saveUsers(users: UserProfile[]): void {
    try {
      localStorage.setItem(this.storageKey, JSON.stringify(users));
    } catch (error) {
      console.error('Could not save users to storage:', error);
    }
  }

  // Create new user
  async createUser(userData: Omit<UserProfile, 'id' | 'createdAt' | 'lastLogin'>): Promise<UserProfile> {
    const users = this.getUsers();
    
    // Check if phone number already exists
    const existingUser = users.find(user => user.phone === userData.phone);
    if (existingUser) {
      throw new Error('Phone number already registered');
    }

    const newUser: UserProfile = {
      ...userData,
      id: `user_${Date.now()}_${Math.random().toString(36).substr(2, 9)}`,
      createdAt: new Date(),
      lastLogin: new Date()
    };

    users.push(newUser);
    this.saveUsers(users);
    
    return newUser;
  }

  // Get user by phone number
  async getUserByPhone(phone: string): Promise<UserProfile | null> {
    const users = this.getUsers();
    return users.find(user => user.phone === phone) || null;
  }

  // Update user information
  async updateUser(updatedUser: UserProfile): Promise<UserProfile> {
    const users = this.getUsers();
    const userIndex = users.findIndex(user => user.id === updatedUser.id);
    
    if (userIndex === -1) {
      throw new Error('User not found');
    }

    users[userIndex] = updatedUser;
    this.saveUsers(users);
    
    return updatedUser;
  }

  // Get recent users (for quick login)
  async getRecentUsers(limit: number = 5): Promise<UserProfile[]> {
    const users = this.getUsers();
    return users
      .sort((a, b) => new Date(b.lastLogin).getTime() - new Date(a.lastLogin).getTime())
      .slice(0, limit);
  }

  // Create user session
  createSession(user: UserProfile): UserSession {
    const session: UserSession = {
      user: { ...user, lastLogin: new Date() },
      loginTime: new Date(),
      isActive: true
    };

    this.currentSession = session;
    
    try {
      localStorage.setItem(this.sessionKey, JSON.stringify(session));
      // Update user's last login time
      this.updateUser(session.user);
    } catch (error) {
      console.warn('Could not save session to storage:', error);
    }

    return session;
  }

  // Get current session
  getCurrentSession(): UserSession | null {
    if (this.currentSession && this.currentSession.isActive) {
      return this.currentSession;
    }

    try {
      const stored = localStorage.getItem(this.sessionKey);
      if (stored) {
        const session = JSON.parse(stored) as UserSession;
        session.user.lastLogin = new Date(session.user.lastLogin);
        session.user.createdAt = new Date(session.user.createdAt);
        session.loginTime = new Date(session.loginTime);
        
        // Check if session is still valid (24 hours)
        const sessionAge = Date.now() - session.loginTime.getTime();
        const maxAge = 24 * 60 * 60 * 1000; // 24 hours
        
        if (sessionAge < maxAge && session.isActive) {
          this.currentSession = session;
          return session;
        } else {
          this.clearSession();
        }
      }
    } catch (error) {
      console.warn('Could not load session from storage:', error);
      this.clearSession();
    }

    return null;
  }

  // Clear current session (logout)
  clearSession(): void {
    this.currentSession = null;
    try {
      localStorage.removeItem(this.sessionKey);
    } catch (error) {
      console.warn('Could not clear session from storage:', error);
    }
  }

  // Check if user is logged in
  isLoggedIn(): boolean {
    const session = this.getCurrentSession();
    return session !== null && session.isActive;
  }

  // Get current user
  getCurrentUser(): UserProfile | null {
    const session = this.getCurrentSession();
    return session ? session.user : null;
  }

  // Export user data for backup
  exportUserData(): string {
    const users = this.getUsers();
    const currentSession = this.getCurrentSession();
    
    const exportData = {
      users,
      currentSession,
      exportDate: new Date().toISOString(),
      version: '1.0'
    };

    return JSON.stringify(exportData, null, 2);
  }

  // Import user data from backup
  importUserData(jsonData: string): boolean {
    try {
      const importData = JSON.parse(jsonData);
      
      if (importData.users && Array.isArray(importData.users)) {
        this.saveUsers(importData.users);
        
        if (importData.currentSession) {
          localStorage.setItem(this.sessionKey, JSON.stringify(importData.currentSession));
        }
        
        return true;
      }
    } catch (error) {
      console.error('Could not import user data:', error);
    }
    
    return false;
  }

  // Get user statistics
  getUserStats(): {
    totalUsers: number;
    activeUsers: number;
    usersByRole: Record<string, number>;
    recentActivity: number;
  } {
    const users = this.getUsers();
    const now = Date.now();
    const weekAgo = now - (7 * 24 * 60 * 60 * 1000);

    const usersByRole = users.reduce((acc, user) => {
      acc[user.role] = (acc[user.role] || 0) + 1;
      return acc;
    }, {} as Record<string, number>);

    const recentActivity = users.filter(user => 
      new Date(user.lastLogin).getTime() > weekAgo
    ).length;

    return {
      totalUsers: users.length,
      activeUsers: this.isLoggedIn() ? 1 : 0,
      usersByRole,
      recentActivity
    };
  }

  // Validate phone number format
  validatePhoneNumber(phone: string): boolean {
    // Indian phone number validation (10 digits starting with 6-9)
    const phoneRegex = /^[6-9]\d{9}$/;
    const cleanPhone = phone.replace(/[\s\-\(\)]/g, '');
    return phoneRegex.test(cleanPhone);
  }

  // Clean up old data (remove users not active for 90 days)
  cleanupOldData(): number {
    const users = this.getUsers();
    const cutoffDate = Date.now() - (90 * 24 * 60 * 60 * 1000); // 90 days ago
    
    const activeUsers = users.filter(user => 
      new Date(user.lastLogin).getTime() > cutoffDate
    );

    const removedCount = users.length - activeUsers.length;
    
    if (removedCount > 0) {
      this.saveUsers(activeUsers);
    }

    return removedCount;
  }
}

// Export singleton instance
export const userStorage = new UserStorageManager();

// Export types
export type { UserProfile, UserSession };