import { useEffect, useState } from 'react';
import { Pressable, StyleSheet, Text, TextInput, View } from 'react-native';
import { router } from 'expo-router';
import { useAuthStore, type AuthState } from '../store/auth-store';
import { colors } from '../theme';

export default function AuthScreen() {
  const [mode, setMode] = useState<'signin' | 'register'>('signin');
  const [displayName, setDisplayName] = useState('');
  const [email, setEmail] = useState('');
  const [password, setPassword] = useState('');
  const [errorMessage, setErrorMessage] = useState<string | null>(null);
  const isAuthenticated = useAuthStore((state: AuthState) => state.isAuthenticated);
  const signIn = useAuthStore((state: AuthState) => state.signIn);
  const register = useAuthStore((state: AuthState) => state.register);
  const isLoading = useAuthStore((state: AuthState) => state.isLoading);

  useEffect(() => {
    if (isAuthenticated) {
      router.replace('/(tabs)');
    }
  }, [isAuthenticated]);

  return (
    <View style={styles.container}>
      <Text style={styles.title}>NoteLett</Text>
      <Text style={styles.subtitle}>{mode === 'signin' ? 'Sign in to continue' : 'Create your account'}</Text>
      {mode === 'register' ? (
        <TextInput
          autoCapitalize="words"
          onChangeText={(value: string) => {
            setErrorMessage(null);
            setDisplayName(value);
          }}
          placeholder="Display name"
          placeholderTextColor={colors.textTertiary}
          style={styles.input}
          value={displayName}
        />
      ) : null}
      <TextInput
        autoCapitalize="none"
        keyboardType="email-address"
        onChangeText={(value: string) => {
          setErrorMessage(null);
          setEmail(value);
        }}
        placeholder="Email"
        placeholderTextColor={colors.textTertiary}
        style={styles.input}
        value={email}
      />
      <TextInput
        onChangeText={(value: string) => {
          setErrorMessage(null);
          setPassword(value);
        }}
        placeholder="Password"
        placeholderTextColor={colors.textTertiary}
        secureTextEntry
        style={styles.input}
        value={password}
      />
      {errorMessage ? <Text style={styles.errorText}>{errorMessage}</Text> : null}
      <Pressable
        accessibilityLabel={mode === 'signin' ? 'Sign in' : 'Register account'}
        onPress={async () => {
          const didAuthenticate =
            mode === 'signin'
              ? await signIn(email.trim(), password)
              : await register(email.trim(), password, displayName.trim());

          if (didAuthenticate) {
            router.replace('/(tabs)');
            return;
          }

          setErrorMessage(
            mode === 'signin'
              ? 'Sign-in failed. Check your credentials or connection and try again.'
              : 'Registration failed. Check your details or connection and try again.',
          );
        }}
        style={styles.button}
      >
        <Text style={styles.buttonText}>
          {isLoading ? (mode === 'signin' ? 'Signing in…' : 'Creating account…') : mode === 'signin' ? 'Sign in' : 'Register'}
        </Text>
      </Pressable>
      <Pressable
        accessibilityLabel={mode === 'signin' ? 'Switch to register mode' : 'Switch to sign in mode'}
        onPress={() => {
          setErrorMessage(null);
          setMode((current) => (current === 'signin' ? 'register' : 'signin'));
        }}
        style={styles.modeSwitch}
      >
        <Text style={styles.modeSwitchText}>
          {mode === 'signin' ? 'Need an account? Register' : 'Already have an account? Sign in'}
        </Text>
      </Pressable>
    </View>
  );
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    justifyContent: 'center',
    padding: 24,
    backgroundColor: colors.bgCanvas,
    gap: 12,
  },
  title: {
    fontSize: 28,
    fontWeight: '700',
    color: colors.textPrimary,
  },
  subtitle: {
    fontSize: 16,
    color: colors.textSecondary,
    marginBottom: 12,
  },
  input: {
    borderWidth: 1,
    borderColor: colors.borderDefault,
    borderRadius: 12,
    paddingHorizontal: 14,
    paddingVertical: 12,
    color: colors.textPrimary,
    backgroundColor: colors.surfaceCard,
  },
  button: {
    marginTop: 8,
    backgroundColor: colors.accentPrimary,
    borderRadius: 12,
    paddingVertical: 14,
    alignItems: 'center',
  },
  buttonText: {
    color: colors.textPrimary,
    fontWeight: '700',
  },
  errorText: {
    color: colors.danger,
    fontSize: 14,
  },
  modeSwitch: {
    alignItems: 'center',
    paddingVertical: 4,
  },
  modeSwitchText: {
    color: colors.accentSecondary,
    fontSize: 14,
    fontWeight: '600',
  },
});