import React, { useState, useEffect } from 'react';
import { useDispatch, useSelector } from 'react-redux';
import { useNavigate, useSearchParams } from 'react-router-dom';
import { clearError } from '../store/reducers/authSlice';
// Import the Supabase client
import { supabase } from '../services/supabaseClient';

const ResetPassword = () => {
  const dispatch = useDispatch();
  const navigate = useNavigate();
  const [searchParams] = useSearchParams();
  const { loading, error } = useSelector(state => state.auth);
  
  const [formData, setFormData] = useState({
    token: '', // This is likely unused in the v2 flow, but kept for structure
    password: '',
    confirmPassword: ''
  });
  
  const [showPassword, setShowPassword] = useState(false);
  const [showConfirmPassword, setShowConfirmPassword] = useState(false);
  const [passwordStrength, setPasswordStrength] = useState(0);
  const [isFocused, setIsFocused] = useState({
    password: false,
    confirmPassword: false
  });
  const [authState, setAuthState] = useState({ event: null, session: null });

  // --- Listen for auth state changes specifically on this page ---
  // This helps confirm if PASSWORD_RECOVERY was detected
  useEffect(() => {
    console.log("ResetPassword component mounted. Setting up auth listener.");
    const { data: authListener } = supabase.auth.onAuthStateChange((event, session) => {
      console.log('Auth state changed within ResetPassword component:', event, session ? `User: ${session.user?.id || 'N/A'}` : 'No session');
      setAuthState({ event, session });
      
      if (event === 'PASSWORD_RECOVERY') {
        console.log('*** PASSWORD_RECOVERY event confirmed in ResetPassword component. ***');
        // Optional: You could set some state here to indicate the recovery flow is active
      }
    });

    // Cleanup listener on unmount
    return () => {
      console.log("ResetPassword component unmounting. Removing auth listener.");
      authListener?.subscription.unsubscribe();
    };
  }, []);

  // Get token from URL params (old v1 flow, kept for reference but likely not used)
  useEffect(() => {
    const token = searchParams.get('token');
    if (token) {
      console.warn("Token found in search params (v1 flow?). This might be unexpected in v2 flow:", token);
      setFormData(prev => ({ ...prev, token }));
    }
  }, [searchParams]);
  
  const calculatePasswordStrength = (password) => {
    let strength = 0;
    
    // Length check
    if (password.length >= 8) strength += 1;
    if (password.length >= 12) strength += 1;
    
    // Character variety checks
    if (/[a-z]/.test(password)) strength += 1;
    if (/[A-Z]/.test(password)) strength += 1;
    if (/[0-9]/.test(password)) strength += 1;
    if (/[^A-Za-z0-9]/.test(password)) strength += 1;
    
    setPasswordStrength(Math.min(strength, 6));
  };
  
  const handleChange = (e) => {
    const { name, value } = e.target;
    setFormData({
      ...formData,
      [name]: value
    });
    
    // Calculate password strength
    if (name === 'password') {
      calculatePasswordStrength(value);
    }
  };
  
  const handleFocus = (field) => {
    setIsFocused({
      ...isFocused,
      [field]: true
    });
  };
  
  const handleBlur = (field) => {
    setIsFocused({
      ...isFocused,
      [field]: false
    });
  };
  
  const togglePasswordVisibility = () => {
    setShowPassword(!showPassword);
  };
  
  const toggleConfirmPasswordVisibility = () => {
    setShowConfirmPassword(!showConfirmPassword);
  };
  
  const handleSubmit = async (e) => {
    e.preventDefault();

    // Basic validation
    if (formData.password !== formData.confirmPassword) {
      alert('Passwords do not match');
      return;
    }
    if (formData.password.length < 8) {
      alert('Password must be at least 8 characters long');
      return;
    }

    try {
      console.log("Attempting to get current session before password update...");
      
      // --- Check for existing session (recovery session) ---
      // It's crucial to verify the session was established by the Supabase client
      // when it processed the URL fragments on app load.
      const { data: { session: currentSession }, error: sessionError } = await supabase.auth.getSession();
      console.log("Current session check result:", currentSession ? `Session for user: ${currentSession.user?.id || 'N/A'}` : 'No session', sessionError);
      
      if (sessionError) {
        console.error('Error getting current session:', sessionError);
        alert('Failed to get session. Please try resetting your password again.');
        return;
      }

      if (!currentSession || !currentSession.user) {
        // This is the likely cause of AuthSessionMissingError
        console.warn('No active session found in handleSubmit. The URL might not have been processed correctly or the session expired.');
        console.log("Auth state at time of submission:", authState);
        alert('Password reset link may be invalid or expired. Please request a new one.');
        // Optionally, redirect to /forgot-password
        // navigate('/forgot-password');
        return;
      }

      console.log('Resetting password with Supabase client for user:', currentSession.user?.email);

      const { data, error } = await supabase.auth.updateUser({
        password: formData.password
      });
      console.log("supabase.auth.updateUser result:", data, error);

      if (error) {
        console.error('Supabase password reset error:', error);
        let message = 'Failed to reset password.';
        if (error.message.toLowerCase().includes('password')) {
           message = 'Password does not meet requirements. Please use at least 8 characters.';
        } else if (error.message.toLowerCase().includes('session') || error.message.includes("Auth session missing")) {
           message = 'Password reset session expired. Please request a new reset link.';
        } else {
          message = error.message;
        }
        alert(message);
        return;
      }

      console.log('Password updated successfully:', data);
      alert('Password reset successfully! You can now log in with your new password.');
      // After successful reset, sign the user out of the temporary recovery session.
      await supabase.auth.signOut(); 
      navigate('/login');

    } catch (err) {
      console.error('Unexpected error during password reset:', err);
      alert('An unexpected error occurred. Please try again.');
    }
  };
  
  const handleBackToLogin = () => {
    dispatch(clearError());
    navigate('/login');
  };
  
  return (
    <div className="min-h-screen bg-gradient-to-br from-primary-50 via-white to-accent-50 flex items-center justify-center p-3 sm:p-4 animate-fade-in">
      <div className="w-full max-w-sm sm:max-w-md">
        {/* Logo and Brand */}
        <div className="text-center mb-6 sm:mb-8 animate-slide-up">
          <div className="inline-flex items-center justify-center w-14 h-14 sm:w-16 sm:h-16 bg-gradient-to-br from-primary-600 to-primary-800 rounded-2xl shadow-lg mb-3 sm:mb-4">
            <span className="text-xl sm:text-2xl font-bold text-white">Lin</span>
          </div>
          <h1 className="text-2xl sm:text-3xl font-bold text-gray-900 mb-1 sm:mb-2">Reset Password</h1>
          <p className="text-sm sm:text-base text-gray-600">Enter your new password below</p>
        </div>
        
        {/* Auth Card */}
        <div className="bg-white rounded-2xl shadow-xl p-4 sm:p-8 space-y-4 sm:space-y-6 animate-slide-up animate-delay-100">
          {/* --- Debug Info Display (Remove in production) --- */}
          <div className="bg-yellow-50 border border-yellow-200 rounded-lg p-2 text-xs">
            <strong>Debug Info:</strong>
            <p>Auth Event: {authState.event || 'None'}</p>
            <p>Auth Session User ID: {authState.session?.user?.id || 'None'}</p>
          </div>
          {/* --- End Debug Info --- */}

          {/* Error Message */}
          {error && (
            <div className="bg-red-50 border border-red-200 rounded-lg p-3 sm:p-4 animate-slide-up animate-delay-200">
              <div className="flex items-start space-x-2">
                <svg className="w-4 h-4 sm:w-5 sm:h-5 text-red-500 flex-shrink-0 mt-0.5" fill="currentColor" viewBox="0 0 20 20">
                  <path fillRule="evenodd" d="M10 18a8 8 0 100-16 8 8 0 000 16zM8.707 7.293a1 1 0 00-1.414 1.414L8.586 10l-1.293 1.293a1 1 0 101.414 1.414L10 11.414l1.293 1.293a1 1 0 001.414-1.414L11.414 10l1.293-1.293a1 1 0 00-1.414-1.414L10 8.586 8.707 7.293z" clipRule="evenodd" />
                </svg>
                <span className="text-red-700 text-xs sm:text-sm font-medium">{error}</span>
              </div>
            </div>
          )}
          
          <form onSubmit={handleSubmit} className="space-y-4 sm:space-y-5">
            {/* Password Field */}
            <div className="space-y-2">
              <label htmlFor="password" className="block text-xs sm:text-sm font-semibold text-gray-700">
                New Password
              </label>
              <div className="relative">
                <input
                  type={showPassword ? "text" : "password"}
                  id="password"
                  name="password"
                  value={formData.password}
                  onChange={handleChange}
                  onFocus={() => handleFocus('password')}
                  onBlur={() => handleBlur('password')}
                  className={`w-full px-3 sm:px-4 py-2 sm:py-3 rounded-xl border-2 transition-all duration-200 ${
                    isFocused.password
                      ? 'border-primary-500 shadow-md'
                      : 'border-gray-200 hover:border-gray-300'
                  } ${formData.password ? 'text-gray-900' : 'text-gray-500'} focus:outline-none focus:ring-2 focus:ring-primary-500 focus:ring-offset-2 touch-manipulation`}
                  placeholder="Create a new password"
                  required
                  aria-required="true"
                  aria-label="New password"
                />
                <button
                  type="button"
                  onClick={togglePasswordVisibility}
                  className="absolute inset-y-0 right-0 flex items-center pr-3 text-gray-400 hover:text-gray-600 transition-colors touch-manipulation"
                  aria-label={showPassword ? "Hide password" : "Show password"}
                >
                  {showPassword ? (
                    <svg className="w-4 h-4 sm:w-5 sm:h-5" fill="currentColor" viewBox="0 0 20 20">
                      <path d="M10 12a2 2 0 100-4 2 2 0 000 4z" />
                      <path fillRule="evenodd" d="M.458 10C1.732 5.943 5.522 3 10 3s8.268 2.943 9.542 7c-1.274 4.057-5.064 7-9.542 7S1.732 14.057.458 10zM14 10a4 4 0 11-8 0 4 4 0 018 0z" clipRule="evenodd" />
                    </svg>
                  ) : (
                    <svg className="w-4 h-4 sm:w-5 sm:h-5" fill="currentColor" viewBox="0 0 20 20">
                      <path fillRule="evenodd" d="M3.707 2.293a1 1 0 00-1.414 1.414l14 14a1 1 0 001.414-1.414l-1.473-1.473A10.014 10.014 0 0019.542 10C18.268 5.943 14.478 3 10 3a9.958 9.958 0 00-4.512 1.074l-1.78-1.781zm4.261 4.26l1.514 1.515a2.003 2.003 0 012.45 2.45l1.514 1.514a4 4 0 00-5.478-5.478z" clipRule="evenodd" />
                      <path d="M12.454 16.697L9.75 13.992a4 4 0 01-3.742-3.741L2.335 6.578A9.98 9.98 0 00.458 10c1.274 4.057 5.065 7 9.542 7 .847 0 1.669-.105 2.454-.303z" />
                    </svg>
                  )}
                </button>
              </div>
              
              {/* Password Strength Indicator */}
              {formData.password && (
                <div className="space-y-1">
                  <div className="flex justify-between text-xs">
                    <span className="text-gray-600">Password strength</span>
                    <span className={`font-medium ${
                      passwordStrength <= 2 ? 'text-red-600' :
                      passwordStrength <= 4 ? 'text-yellow-600' :
                      'text-green-600'
                    }`}>
                      {passwordStrength <= 2 ? 'Weak' :
                       passwordStrength <= 4 ? 'Fair' :
                       passwordStrength === 5 ? 'Good' :
                       'Strong'}
                    </span>
                  </div>
                  <div className="w-full bg-gray-200 rounded-full h-1.5 sm:h-2">
                    <div
                      className={`h-1.5 sm:h-2 rounded-full transition-all duration-300 ${
                        passwordStrength <= 2 ? 'bg-red-500 w-1/3' :
                        passwordStrength <= 4 ? 'bg-yellow-500 w-2/3' :
                        passwordStrength === 5 ? 'bg-green-500 w-4/5' :
                        'bg-green-600 w-full'
                      }`}
                    ></div>
                  </div>
                  <div className="text-xs text-gray-500">
                    Use 8+ characters with uppercase, lowercase, numbers, and symbols
                  </div>
                </div>
              )}
            </div>
            
            {/* Confirm Password Field */}
            <div className="space-y-2">
              <label htmlFor="confirmPassword" className="block text-xs sm:text-sm font-semibold text-gray-700">
                Confirm New Password
              </label>
              <div className="relative">
                <input
                  type={showConfirmPassword ? "text" : "password"}
                  id="confirmPassword"
                  name="confirmPassword"
                  value={formData.confirmPassword}
                  onChange={handleChange}
                  onFocus={() => handleFocus('confirmPassword')}
                  onBlur={() => handleBlur('confirmPassword')}
                  className={`w-full px-3 sm:px-4 py-2 sm:py-3 rounded-xl border-2 transition-all duration-200 ${
                    isFocused.confirmPassword
                      ? 'border-primary-500 shadow-md'
                      : 'border-gray-200 hover:border-gray-300'
                  } ${formData.confirmPassword ? 'text-gray-900' : 'text-gray-500'} focus:outline-none focus:ring-2 focus:ring-primary-500 focus:ring-offset-2 touch-manipulation`}
                  placeholder="Confirm your new password"
                  required
                  aria-required="true"
                  aria-label="Confirm new password"
                />
                <button
                  type="button"
                  onClick={toggleConfirmPasswordVisibility}
                  className="absolute inset-y-0 right-0 flex items-center pr-3 text-gray-400 hover:text-gray-600 transition-colors touch-manipulation"
                  aria-label={showConfirmPassword ? "Hide confirm password" : "Show confirm password"}
                >
                  {showConfirmPassword ? (
                    <svg className="w-4 h-4 sm:w-5 sm:h-5" fill="currentColor" viewBox="0 0 20 20">
                      <path d="M10 12a2 2 0 100-4 2 2 0 000 4z" />
                      <path fillRule="evenodd" d="M.458 10C1.732 5.943 5.522 3 10 3s8.268 2.943 9.542 7c-1.274 4.057-5.064 7-9.542 7S1.732 14.057.458 10zM14 10a4 4 0 11-8 0 4 4 0 018 0z" clipRule="evenodd" />
                    </svg>
                  ) : (
                    <svg className="w-4 h-4 sm:w-5 sm:h-5" fill="currentColor" viewBox="0 0 20 20">
                      <path fillRule="evenodd" d="M3.707 2.293a1 1 0 00-1.414 1.414l14 14a1 1 0 001.414-1.414l-1.473-1.473A10.014 10.014 0 0019.542 10C18.268 5.943 14.478 3 10 3a9.958 9.958 0 00-4.512 1.074l-1.78-1.781zm4.261 4.26l1.514 1.515a2.003 2.003 0 012.45 2.45l1.514 1.514a4 4 0 00-5.478-5.478z" clipRule="evenodd" />
                      <path d="M12.454 16.697L9.75 13.992a4 4 0 01-3.742-3.741L2.335 6.578A9.98 9.98 0 00.458 10c1.274 4.057 5.065 7 9.542 7 .847 0 1.669-.105 2.454-.303z" />
                    </svg>
                  )}
                </button>
              </div>
              {formData.confirmPassword && formData.password !== formData.confirmPassword && (
                <p className="text-red-600 text-xs">Passwords do not match</p>
              )}
            </div>
            
            {/* Submit Button */}
            <button
              type="submit"
              disabled={loading === 'pending'}
              className="w-full bg-gradient-to-r from-primary-600 to-primary-800 text-white font-semibold py-2.5 sm:py-3 px-4 rounded-xl hover:from-primary-700 hover:to-primary-900 focus:outline-none focus:ring-2 focus:ring-primary-500 focus:ring-offset-2 transition-all duration-200 transform hover:scale-[1.02] active:scale-[0.98] disabled:opacity-50 disabled:cursor-not-allowed disabled:transform-none touch-manipulation"
              aria-busy={loading === 'pending'}
            >
              {loading === 'pending' ? (
                <div className="flex items-center justify-center">
                  <svg className="animate-spin -ml-1 mr-2 sm:mr-3 h-4 w-4 sm:h-5 sm:w-5 text-white" xmlns="http://www.w3.org/2000/svg" fill="none" viewBox="0 0 24 24">
                    <circle className="opacity-25" cx="12" cy="12" r="10" stroke="currentColor" strokeWidth="4"></circle>
                    <path className="opacity-75" fill="currentColor" d="M4 12a8 8 0 018-8V0C5.373 0 0 5.373 0 12h4zm2 5.291A7.962 7.962 0 014 12H0c0 3.042 1.135 5.824 3 7.938l3-2.647z"></path>
                  </svg>
                  <span className="text-xs sm:text-sm">Resetting password...</span>
                </div>
              ) : (
                <span className="text-xs sm:text-sm">Reset Password</span>
              )}
            </button>
          </form>
          
          {/* Back to Login Link */}
          <div className="text-center">
            <button
              type="button"
              onClick={handleBackToLogin}
              className="font-semibold text-primary-600 hover:text-primary-500 transition-colors focus:outline-none focus:underline text-xs sm:text-sm"
              aria-label="Back to login"
            >
              Back to Sign In
            </button>
          </div>
        </div>
        
        {/* Footer */}
        <div className="text-center mt-6 sm:mt-8 text-xs text-gray-500">
          <p>&copy; 2024 Lin. All rights reserved.</p>
        </div>
      </div>
    </div>
  );
};

export default ResetPassword;