import { useState, useEffect } from 'react';
import { useRouter } from 'next/router';
import Layout from '../components/Layout';

export default function Settings() {
  const router = useRouter();
  
  // User state
  const [user, setUser] = useState(null);
  
  // Settings state
  const [settings, setSettings] = useState({
    // Account Settings
    notifications_email: true,
    notifications_marketing: false,
    collection_visibility: 'private',
    preferred_currency: 'USD',
    cards_per_page: 50,
    default_view: 'grid',
    
    // Security Settings
    two_factor_enabled: false,
    
    // Display Settings
    theme: 'system', // light, dark, system
    language: 'en'
  });
  
  // Password change state
  const [passwordForm, setPasswordForm] = useState({
    current_password: '',
    new_password: '',
    confirm_password: ''
  });
  
  // UI state
  const [loading, setLoading] = useState(true);
  const [saving, setSaving] = useState(false);
  const [changingPassword, setChangingPassword] = useState(false);
  const [message, setMessage] = useState({ type: '', text: '' });
  const [activeSection, setActiveSection] = useState('account');

  useEffect(() => {
    loadSettings();
  }, []);

  const loadSettings = async () => {
    try {
      const token = localStorage.getItem('auth_token');
      if (!token) {
        router.push('/login');
        return;
      }

      const response = await fetch('/api/user/settings', {
        headers: {
          'Authorization': `Bearer ${token}`
        }
      });

      if (response.ok) {
        const data = await response.json();
        setUser(data.user);
        setSettings(data.settings);
      } else if (response.status === 401) {
        router.push('/login');
      }
    } catch (error) {
      console.error('Error loading settings:', error);
      setMessage({ type: 'error', text: 'Failed to load settings' });
    } finally {
      setLoading(false);
    }
  };

  const handleSettingChange = (key, value) => {
    setSettings(prev => ({
      ...prev,
      [key]: value
    }));
  };

  const saveSettings = async () => {
    setSaving(true);
    setMessage({ type: '', text: '' });

    try {
      const token = localStorage.getItem('auth_token');
      const response = await fetch('/api/user/settings', {
        method: 'PUT',
        headers: {
          'Content-Type': 'application/json',
          'Authorization': `Bearer ${token}`
        },
        body: JSON.stringify(settings)
      });

      if (response.ok) {
        setMessage({ type: 'success', text: 'Settings saved successfully!' });
      } else {
        const error = await response.json();
        setMessage({ type: 'error', text: error.message || 'Failed to save settings' });
      }
    } catch (error) {
      console.error('Error saving settings:', error);
      setMessage({ type: 'error', text: 'Failed to save settings' });
    } finally {
      setSaving(false);
    }
  };

  const handlePasswordChange = async (e) => {
    e.preventDefault();
    
    if (passwordForm.new_password !== passwordForm.confirm_password) {
      setMessage({ type: 'error', text: 'New passwords do not match' });
      return;
    }

    if (passwordForm.new_password.length < 8) {
      setMessage({ type: 'error', text: 'Password must be at least 8 characters long' });
      return;
    }

    setChangingPassword(true);
    setMessage({ type: '', text: '' });

    try {
      const token = localStorage.getItem('auth_token');
      const response = await fetch('/api/user/password', {
        method: 'PUT',
        headers: {
          'Content-Type': 'application/json',
          'Authorization': `Bearer ${token}`
        },
        body: JSON.stringify({
          current_password: passwordForm.current_password,
          new_password: passwordForm.new_password
        })
      });

      if (response.ok) {
        setPasswordForm({ current_password: '', new_password: '', confirm_password: '' });
        setMessage({ type: 'success', text: 'Password changed successfully!' });
      } else {
        const error = await response.json();
        setMessage({ type: 'error', text: error.message || 'Failed to change password' });
      }
    } catch (error) {
      console.error('Error changing password:', error);
      setMessage({ type: 'error', text: 'Failed to change password' });
    } finally {
      setChangingPassword(false);
    }
  };

  const handleDeleteAccount = async () => {
    const confirmed = window.confirm(
      'Are you sure you want to delete your account? This action cannot be undone and will permanently delete all your cards, collections, and decks.'
    );

    if (!confirmed) return;

    const doubleConfirmed = window.confirm(
      'This is your final warning. Deleting your account will permanently remove all your data. Type "DELETE" to confirm.'
    );

    if (!doubleConfirmed) return;

    try {
      const token = localStorage.getItem('auth_token');
      const response = await fetch('/api/user/delete', {
        method: 'DELETE',
        headers: {
          'Authorization': `Bearer ${token}`
        }
      });

      if (response.ok) {
        localStorage.removeItem('auth_token');
        router.push('/login?message=Account deleted successfully');
      } else {
        const error = await response.json();
        setMessage({ type: 'error', text: error.message || 'Failed to delete account' });
      }
    } catch (error) {
      console.error('Error deleting account:', error);
      setMessage({ type: 'error', text: 'Failed to delete account' });
    }
  };

  const sections = [
    { id: 'account', name: 'Account', icon: '👤' },
    { id: 'security', name: 'Security', icon: '🔒' },
    { id: 'preferences', name: 'Preferences', icon: '⚙️' },
    { id: 'notifications', name: 'Notifications', icon: '🔔' },
    { id: 'display', name: 'Display', icon: '🎨' }
  ];

  const currencyOptions = [
    { value: 'USD', label: 'US Dollar ($)' },
    { value: 'EUR', label: 'Euro (€)' },
    { value: 'GBP', label: 'British Pound (£)' },
    { value: 'CAD', label: 'Canadian Dollar (C$)' },
    { value: 'JPY', label: 'Japanese Yen (¥)' }
  ];

  const cardsPerPageOptions = [
    { value: 25, label: '25 cards' },
    { value: 50, label: '50 cards' },
    { value: 100, label: '100 cards' }
  ];

  const viewOptions = [
    { value: 'grid', label: 'Grid View' },
    { value: 'list', label: 'List View' }
  ];

  const themeOptions = [
    { value: 'light', label: 'Light' },
    { value: 'dark', label: 'Dark' },
    { value: 'system', label: 'System' }
  ];

  if (loading) {
    return (
      <Layout user={user}>
        <div className="flex items-center justify-center min-h-screen">
          <div className="animate-spin rounded-full h-32 w-32 border-b-2" style={{ borderColor: 'var(--accent-ember)' }}></div>
        </div>
      </Layout>
    );
  }

  return (
    <Layout user={user}>
      <div className="max-w-6xl mx-auto p-6">
        {/* Header */}
        <div className="mb-8">
          <h1 className="text-3xl font-bold mb-2" style={{ color: 'var(--text-primary)' }}>
            Settings
          </h1>
          <p className="text-lg" style={{ color: 'var(--text-secondary)' }}>
            Manage your account preferences and security settings
          </p>
        </div>

        {/* Message */}
        {message.text && (
          <div className={`mb-6 p-4 rounded-xl ${
            message.type === 'success' 
              ? 'bg-green-50 dark:bg-green-900/20 text-green-800 dark:text-green-200 border border-green-200 dark:border-green-800'
              : 'bg-red-50 dark:bg-red-900/20 text-red-800 dark:text-red-200 border border-red-200 dark:border-red-800'
          }`}>
            {message.text}
          </div>
        )}

        <div className="grid grid-cols-1 lg:grid-cols-4 gap-8">
          {/* Sidebar Navigation */}
          <div className="lg:col-span-1">
            <div className="card p-4">
              <nav className="space-y-2">
                {sections.map(section => (
                  <button
                    key={section.id}
                    onClick={() => setActiveSection(section.id)}
                    className={`w-full flex items-center gap-3 px-4 py-3 rounded-xl font-medium transition-all duration-200 text-left ${
                      activeSection === section.id ? 'shadow-lg' : 'hover:shadow-md'
                    }`}
                    style={{
                      backgroundColor: activeSection === section.id ? 'var(--accent-ember)' : 'transparent',
                      color: activeSection === section.id ? 'white' : 'var(--text-primary)'
                    }}
                  >
                    <span>{section.icon}</span>
                    {section.name}
                  </button>
                ))}
              </nav>
            </div>
          </div>

          {/* Settings Content */}
          <div className="lg:col-span-3">
            <div className="card p-6">
              {/* Account Settings */}
              {activeSection === 'account' && (
                <div>
                  <h2 className="text-2xl font-bold mb-6" style={{ color: 'var(--text-primary)' }}>
                    Account Settings
                  </h2>
                  
                  <div className="space-y-6">
                    {/* Email */}
                    <div>
                      <label className="block text-sm font-medium mb-2" style={{ color: 'var(--text-primary)' }}>
                        Email Address
                      </label>
                      <div className="flex items-center gap-3">
                        <input
                          type="email"
                          value={user?.email || ''}
                          disabled
                          className="input-field flex-1 opacity-50 cursor-not-allowed"
                        />
                        <span className="px-3 py-1 text-xs rounded-full bg-green-100 dark:bg-green-900/20 text-green-800 dark:text-green-200">
                          Verified
                        </span>
                      </div>
                      <p className="text-xs mt-1" style={{ color: 'var(--text-secondary)' }}>
                        Contact support to change your email address
                      </p>
                    </div>

                    {/* Collection Visibility */}
                    <div>
                      <label className="block text-sm font-medium mb-2" style={{ color: 'var(--text-primary)' }}>
                        Default Collection Visibility
                      </label>
                      <select
                        value={settings.collection_visibility}
                        onChange={(e) => handleSettingChange('collection_visibility', e.target.value)}
                        className="input-field w-full"
                      >
                        <option value="private">Private</option>
                        <option value="public">Public</option>
                        <option value="unlisted">Unlisted</option>
                      </select>
                      <p className="text-xs mt-1" style={{ color: 'var(--text-secondary)' }}>
                        Controls who can see your new collections by default
                      </p>
                    </div>

                    {/* Preferred Currency */}
                    <div>
                      <label className="block text-sm font-medium mb-2" style={{ color: 'var(--text-primary)' }}>
                        Preferred Currency
                      </label>
                      <select
                        value={settings.preferred_currency}
                        onChange={(e) => handleSettingChange('preferred_currency', e.target.value)}
                        className="input-field w-full"
                      >
                        {currencyOptions.map(option => (
                          <option key={option.value} value={option.value}>
                            {option.label}
                          </option>
                        ))}
                      </select>
                      <p className="text-xs mt-1" style={{ color: 'var(--text-secondary)' }}>
                        Currency used for displaying card values
                      </p>
                    </div>
                  </div>
                </div>
              )}

              {/* Security Settings */}
              {activeSection === 'security' && (
                <div>
                  <h2 className="text-2xl font-bold mb-6" style={{ color: 'var(--text-primary)' }}>
                    Security Settings
                  </h2>
                  
                  <div className="space-y-8">
                    {/* Change Password */}
                    <div>
                      <h3 className="text-lg font-semibold mb-4" style={{ color: 'var(--text-primary)' }}>
                        Change Password
                      </h3>
                      <form onSubmit={handlePasswordChange} className="space-y-4">
                        <div>
                          <label className="block text-sm font-medium mb-2" style={{ color: 'var(--text-primary)' }}>
                            Current Password
                          </label>
                          <input
                            type="password"
                            value={passwordForm.current_password}
                            onChange={(e) => setPasswordForm(prev => ({ ...prev, current_password: e.target.value }))}
                            className="input-field w-full"
                            required
                          />
                        </div>
                        <div>
                          <label className="block text-sm font-medium mb-2" style={{ color: 'var(--text-primary)' }}>
                            New Password
                          </label>
                          <input
                            type="password"
                            value={passwordForm.new_password}
                            onChange={(e) => setPasswordForm(prev => ({ ...prev, new_password: e.target.value }))}
                            className="input-field w-full"
                            minLength={8}
                            required
                          />
                        </div>
                        <div>
                          <label className="block text-sm font-medium mb-2" style={{ color: 'var(--text-primary)' }}>
                            Confirm New Password
                          </label>
                          <input
                            type="password"
                            value={passwordForm.confirm_password}
                            onChange={(e) => setPasswordForm(prev => ({ ...prev, confirm_password: e.target.value }))}
                            className="input-field w-full"
                            minLength={8}
                            required
                          />
                        </div>
                        <button
                          type="submit"
                          disabled={changingPassword}
                          className="px-6 py-2 rounded-xl font-medium transition-all duration-200 hover:shadow-md"
                          style={{ 
                            backgroundColor: 'var(--accent-ember)',
                            color: 'white'
                          }}
                        >
                          {changingPassword ? 'Changing Password...' : 'Change Password'}
                        </button>
                      </form>
                    </div>

                    {/* Two-Factor Authentication */}
                    <div>
                      <h3 className="text-lg font-semibold mb-4" style={{ color: 'var(--text-primary)' }}>
                        Two-Factor Authentication
                      </h3>
                      <div className="flex items-center justify-between p-4 rounded-xl" style={{ backgroundColor: 'var(--bg-secondary)' }}>
                        <div>
                          <p className="font-medium" style={{ color: 'var(--text-primary)' }}>
                            Enable 2FA
                          </p>
                          <p className="text-sm" style={{ color: 'var(--text-secondary)' }}>
                            Add an extra layer of security to your account
                          </p>
                        </div>
                        <button
                          onClick={() => handleSettingChange('two_factor_enabled', !settings.two_factor_enabled)}
                          className={`relative inline-flex h-6 w-11 items-center rounded-full transition-colors ${
                            settings.two_factor_enabled ? 'bg-green-600' : 'bg-gray-300 dark:bg-gray-600'
                          }`}
                        >
                          <span
                            className={`inline-block h-4 w-4 transform rounded-full bg-white transition-transform ${
                              settings.two_factor_enabled ? 'translate-x-6' : 'translate-x-1'
                            }`}
                          />
                        </button>
                      </div>
                      {settings.two_factor_enabled && (
                        <p className="text-sm mt-2 p-3 rounded-lg bg-blue-50 dark:bg-blue-900/20 text-blue-800 dark:text-blue-200">
                          Two-factor authentication is enabled. Use your authenticator app to log in.
                        </p>
                      )}
                    </div>

                    {/* Danger Zone */}
                    <div className="border-t pt-8" style={{ borderColor: 'var(--border)' }}>
                      <h3 className="text-lg font-semibold mb-4 text-red-600 dark:text-red-400">
                        Danger Zone
                      </h3>
                      <div className="p-4 rounded-xl border border-red-200 dark:border-red-800 bg-red-50 dark:bg-red-900/20">
                        <div className="flex items-center justify-between">
                          <div>
                            <p className="font-medium text-red-800 dark:text-red-200">
                              Delete Account
                            </p>
                            <p className="text-sm text-red-600 dark:text-red-300">
                              Permanently delete your account and all associated data
                            </p>
                          </div>
                          <button
                            onClick={handleDeleteAccount}
                            className="px-4 py-2 bg-red-600 hover:bg-red-700 text-white rounded-xl font-medium transition-colors"
                          >
                            Delete Account
                          </button>
                        </div>
                      </div>
                    </div>
                  </div>
                </div>
              )}

              {/* Preferences */}
              {activeSection === 'preferences' && (
                <div>
                  <h2 className="text-2xl font-bold mb-6" style={{ color: 'var(--text-primary)' }}>
                    Preferences
                  </h2>
                  
                  <div className="space-y-6">
                    {/* Cards Per Page */}
                    <div>
                      <label className="block text-sm font-medium mb-2" style={{ color: 'var(--text-primary)' }}>
                        Cards Per Page
                      </label>
                      <select
                        value={settings.cards_per_page}
                        onChange={(e) => handleSettingChange('cards_per_page', parseInt(e.target.value))}
                        className="input-field w-full"
                      >
                        {cardsPerPageOptions.map(option => (
                          <option key={option.value} value={option.value}>
                            {option.label}
                          </option>
                        ))}
                      </select>
                    </div>

                    {/* Default View */}
                    <div>
                      <label className="block text-sm font-medium mb-2" style={{ color: 'var(--text-primary)' }}>
                        Default View Mode
                      </label>
                      <select
                        value={settings.default_view}
                        onChange={(e) => handleSettingChange('default_view', e.target.value)}
                        className="input-field w-full"
                      >
                        {viewOptions.map(option => (
                          <option key={option.value} value={option.value}>
                            {option.label}
                          </option>
                        ))}
                      </select>
                    </div>
                  </div>
                </div>
              )}

              {/* Notifications */}
              {activeSection === 'notifications' && (
                <div>
                  <h2 className="text-2xl font-bold mb-6" style={{ color: 'var(--text-primary)' }}>
                    Notification Settings
                  </h2>
                  
                  <div className="space-y-6">
                    {/* Email Notifications */}
                    <div className="flex items-center justify-between p-4 rounded-xl" style={{ backgroundColor: 'var(--bg-secondary)' }}>
                      <div>
                        <p className="font-medium" style={{ color: 'var(--text-primary)' }}>
                          Email Notifications
                        </p>
                        <p className="text-sm" style={{ color: 'var(--text-secondary)' }}>
                          Receive notifications about your collections and cards
                        </p>
                      </div>
                      <button
                        onClick={() => handleSettingChange('notifications_email', !settings.notifications_email)}
                        className={`relative inline-flex h-6 w-11 items-center rounded-full transition-colors ${
                          settings.notifications_email ? 'bg-green-600' : 'bg-gray-300 dark:bg-gray-600'
                        }`}
                      >
                        <span
                          className={`inline-block h-4 w-4 transform rounded-full bg-white transition-transform ${
                            settings.notifications_email ? 'translate-x-6' : 'translate-x-1'
                          }`}
                        />
                      </button>
                    </div>

                    {/* Marketing Emails */}
                    <div className="flex items-center justify-between p-4 rounded-xl" style={{ backgroundColor: 'var(--bg-secondary)' }}>
                      <div>
                        <p className="font-medium" style={{ color: 'var(--text-primary)' }}>
                          Marketing Emails
                        </p>
                        <p className="text-sm" style={{ color: 'var(--text-secondary)' }}>
                          Receive updates about new features and promotions
                        </p>
                      </div>
                      <button
                        onClick={() => handleSettingChange('notifications_marketing', !settings.notifications_marketing)}
                        className={`relative inline-flex h-6 w-11 items-center rounded-full transition-colors ${
                          settings.notifications_marketing ? 'bg-green-600' : 'bg-gray-300 dark:bg-gray-600'
                        }`}
                      >
                        <span
                          className={`inline-block h-4 w-4 transform rounded-full bg-white transition-transform ${
                            settings.notifications_marketing ? 'translate-x-6' : 'translate-x-1'
                          }`}
                        />
                      </button>
                    </div>
                  </div>
                </div>
              )}

              {/* Display Settings */}
              {activeSection === 'display' && (
                <div>
                  <h2 className="text-2xl font-bold mb-6" style={{ color: 'var(--text-primary)' }}>
                    Display Settings
                  </h2>
                  
                  <div className="space-y-6">
                    {/* Theme */}
                    <div>
                      <label className="block text-sm font-medium mb-2" style={{ color: 'var(--text-primary)' }}>
                        Theme
                      </label>
                      <select
                        value={settings.theme}
                        onChange={(e) => handleSettingChange('theme', e.target.value)}
                        className="input-field w-full"
                      >
                        {themeOptions.map(option => (
                          <option key={option.value} value={option.value}>
                            {option.label}
                          </option>
                        ))}
                      </select>
                      <p className="text-xs mt-1" style={{ color: 'var(--text-secondary)' }}>
                        System will follow your device's theme preference
                      </p>
                    </div>

                    {/* Language */}
                    <div>
                      <label className="block text-sm font-medium mb-2" style={{ color: 'var(--text-primary)' }}>
                        Language
                      </label>
                      <select
                        value={settings.language}
                        onChange={(e) => handleSettingChange('language', e.target.value)}
                        className="input-field w-full"
                      >
                        <option value="en">English</option>
                        <option value="es">Español</option>
                        <option value="fr">Français</option>
                        <option value="de">Deutsch</option>
                        <option value="ja">日本語</option>
                      </select>
                      <p className="text-xs mt-1" style={{ color: 'var(--text-secondary)' }}>
                        Interface language (coming soon)
                      </p>
                    </div>
                  </div>
                </div>
              )}

              {/* Save Button */}
              <div className="flex justify-end pt-8 border-t" style={{ borderColor: 'var(--border)' }}>
                <button
                  onClick={saveSettings}
                  disabled={saving}
                  className="px-6 py-3 rounded-xl font-medium transition-all duration-200 hover:shadow-md"
                  style={{ 
                    backgroundColor: 'var(--accent-ember)',
                    color: 'white'
                  }}
                >
                  {saving ? 'Saving...' : 'Save Settings'}
                </button>
              </div>
            </div>
          </div>
        </div>
      </div>
    </Layout>
  );
}