import React, { useEffect, useState } from 'react';
import {
  ActivityIndicator,
  ImageBackground,
  KeyboardAvoidingView,
  Platform,
  ScrollView,
  StyleSheet,
  Text,
  TextInput,
  TouchableOpacity,
  View,
  useWindowDimensions,
} from 'react-native';
import AsyncStorage from '@react-native-async-storage/async-storage';
import { Ionicons } from '@expo/vector-icons';
import { router, useLocalSearchParams } from 'expo-router';
import * as AppleAuthentication from 'expo-apple-authentication';
import Constants from 'expo-constants';
import { useApp } from '../../context/AppContext';
import { useColors } from '../../constants/Colors';
import { AuthService } from '../../services/authService';
import { useSafeAnalytics } from '../../services/analytics';
import { PreAuthOnboardingService } from '../../services/preAuthOnboardingService';
import { Language } from '../../types';

const HERO_IMAGE = require('../../assets/welcome_hero_vertical.png');

const getCopy = (language: Language) => {
  if (language === 'de') {
    return {
      headline: "Let's finish your setup!",
      subline: 'Erstelle einen Account, speichere deine Pflanzen und sichere dir 3 Gratis-Scans pro Monat.',
      emailCta: 'Mit E-Mail fortfahren',
      createCta: 'Account erstellen',
      already: 'Schon einen Account?',
      login: 'Anmelden',
      legal: 'Mit dem Fortfahren akzeptierst du Datenschutz und Nutzungsbedingungen.',
      nameLabel: 'Name',
      emailLabel: 'E-Mail',
      savePlantPrefix: 'Dein Scan wird nach der Registrierung gespeichert:',
    };
  }
  if (language === 'es') {
    return {
      headline: "Let's finish your setup!",
      subline: 'Crea una cuenta para guardar tus plantas y recibir 3 escaneos gratis al mes.',
      emailCta: 'Continuar con email',
      createCta: 'Crear cuenta',
      already: 'Ya tienes cuenta?',
      login: 'Iniciar sesion',
      legal: 'Al continuar aceptas la Politica de privacidad y los Terminos.',
      nameLabel: 'Nombre',
      emailLabel: 'Email',
      savePlantPrefix: 'Guardaremos tu escaneo despues del registro:',
    };
  }
  return {
    headline: "Let's finish your setup!",
    subline: 'Create an account to save your plants and 3 free scans per month.',
    emailCta: 'Continue with Email',
    createCta: 'Create Account',
    already: 'Already have an account?',
    login: 'Log in',
    legal: 'By continuing you agree to our Privacy Policy and Terms.',
    nameLabel: 'Name',
    emailLabel: 'Email',
    savePlantPrefix: 'Your scan will be saved after signup:',
  };
};

export default function SignupScreen() {
  const { isDarkMode, colorPalette, hydrateSession, getPendingPlant, language, t } = useApp();
  const colors = useColors(isDarkMode, colorPalette);
  const copy = getCopy(language);
  const posthog = useSafeAnalytics();
  const pendingPlant = getPendingPlant();
  const params = useLocalSearchParams<{ returnTo?: string; topup?: string }>();
  const isExpoGo = Constants.appOwnership === 'expo';
  const { height } = useWindowDimensions();
  const compact = height < 700;

  const [name, setName] = useState('');
  const [email, setEmail] = useState('');
  const [password, setPassword] = useState('');
  const [passwordConfirm, setPasswordConfirm] = useState('');
  const [showPassword, setShowPassword] = useState(false);
  const [showPasswordConfirm, setShowPasswordConfirm] = useState(false);
  const [emailExpanded, setEmailExpanded] = useState(false);
  const [appleAvailable, setAppleAvailable] = useState(false);
  const [loading, setLoading] = useState(false);
  const [error, setError] = useState<string | null>(null);

  const heroHeight = emailExpanded ? (compact ? 200 : 240) : (compact ? 320 : 400);
  const appleButtonHeight = emailExpanded ? 44 : 56;
  const inputHeight = emailExpanded && compact ? 46 : 52;

  useEffect(() => {
    posthog.capture('signup_screen_viewed', { context: 'onboarding' });
  }, [posthog]);

  useEffect(() => {
    if (isExpoGo) {
      setAppleAvailable(false);
      return;
    }
    let mounted = true;
    AppleAuthentication.isAvailableAsync()
      .then((available) => {
        if (mounted) setAppleAvailable(available);
      })
      .catch(() => {
        if (mounted) setAppleAvailable(false);
      });
    return () => {
      mounted = false;
    };
  }, [isExpoGo]);

  const finishAuth = async (session: Awaited<ReturnType<typeof AuthService.signUp>>) => {
    await hydrateSession(session);
    if (session?.userId) {
      await PreAuthOnboardingService.flushToProfile(session.userId).catch(() => {});
    }
    await AsyncStorage.setItem('greenlens_show_tour', 'true');
    const returnTo = Array.isArray(params.returnTo) ? params.returnTo[0] : params.returnTo;
    const topup = Array.isArray(params.topup) ? params.topup[0] : params.topup;
    if (returnTo === 'billing') {
      router.replace({ pathname: '/profile/billing', params: topup ? { topup } : undefined });
      return;
    }
    if (returnTo === 'paywall') {
      router.replace('/profile/billing?view=paywall&context=out_of_credits');
      return;
    }
    router.replace('/(tabs)');
  };

  const validate = (): string | null => {
    if (!name.trim()) return t.errNameRequired;
    if (!email.trim() || !email.includes('@')) return t.errEmailInvalid;
    if (password.length < 6) return t.errPasswordShort;
    if (password !== passwordConfirm) return t.errPasswordMismatch;
    return null;
  };

  const handleSignup = async () => {
    const validationError = validate();
    if (validationError) {
      setError(validationError);
      setEmailExpanded(true);
      return;
    }
    setLoading(true);
    setError(null);
    try {
      const session = await AuthService.signUp(email, name, password);
      await finishAuth(session);
    } catch (e: any) {
      if (e.message === 'EMAIL_TAKEN') {
        setError(t.errEmailTaken);
      } else if (e.message === 'BACKEND_URL_MISSING' || e.message === 'NETWORK_ERROR') {
        setError(t.errNetworkError);
      } else if (e.message === 'SERVER_ERROR') {
        setError(t.errServerError);
      } else {
        setError(t.errAuthError);
      }
    } finally {
      setLoading(false);
    }
  };

  const handleAppleSignIn = async () => {
    setLoading(true);
    setError(null);
    posthog.capture('apple_login_started', { surface: 'signup' });
    try {
      const credential = await AppleAuthentication.signInAsync({
        requestedScopes: [
          AppleAuthentication.AppleAuthenticationScope.FULL_NAME,
          AppleAuthentication.AppleAuthenticationScope.EMAIL,
        ],
      });

      if (!credential.identityToken) {
        throw new Error('APPLE_AUTH_INVALID');
      }

      const fullName = [
        credential.fullName?.givenName,
        credential.fullName?.familyName,
      ].filter(Boolean).join(' ');
      const session = await AuthService.signInWithApple({
        identityToken: credential.identityToken,
        appleUser: credential.user,
        email: credential.email,
        name: fullName || undefined,
      });
      posthog.capture('apple_login_succeeded', { surface: 'signup' });
      await finishAuth(session);
    } catch (e: any) {
      if (e?.code === 'ERR_REQUEST_CANCELED') return;
      posthog.capture('apple_login_failed', {
        surface: 'signup',
        error: e instanceof Error ? e.message : String(e),
      });
      setError(e?.message === 'APPLE_BACKEND_UNAVAILABLE'
        ? 'Apple Login ist auf dem Backend noch nicht aktiviert. Bitte Backend neu starten oder deployen.'
        : t.errAuthError);
    } finally {
      setLoading(false);
    }
  };

  return (
    <KeyboardAvoidingView
      style={[styles.flex, { backgroundColor: isDarkMode ? '#0a110b' : '#fbfaf3' }]}
      behavior={Platform.OS === 'ios' ? 'padding' : undefined}
    >
      <TouchableOpacity style={styles.backBtn} onPress={() => router.back()} activeOpacity={0.8}>
        <Ionicons name="arrow-back" size={20} color="#ffffff" />
      </TouchableOpacity>

      <ScrollView contentContainerStyle={styles.scroll} keyboardShouldPersistTaps="handled" showsVerticalScrollIndicator={false}>
        <ImageBackground
          source={HERO_IMAGE}
          style={[styles.hero, { height: heroHeight, minHeight: heroHeight }]}
          imageStyle={styles.heroImage}
        >
          <View style={styles.heroOverlay} />
          <View style={styles.heroCopy}>
            <Text style={styles.heroTitle}>{copy.headline}</Text>
            <Text style={styles.heroSubline}>{copy.subline}</Text>
          </View>
        </ImageBackground>

        <View style={[styles.sheet, { backgroundColor: isDarkMode ? '#101a12' : '#fbfaf3' }]}>
          <View style={{ gap: emailExpanded ? 8 : 14 }}>
            {pendingPlant ? (
              <View style={[styles.pendingHint, { backgroundColor: colors.primarySoft, borderColor: colors.border }]}>
                <Ionicons name="sparkles" size={18} color={colors.primary} />
                <Text style={[styles.pendingHintText, { color: colors.text }]}>
                  {copy.savePlantPrefix} {pendingPlant.result.name}
                </Text>
              </View>
            ) : null}

            {appleAvailable ? (
              <AppleAuthentication.AppleAuthenticationButton
                buttonType={AppleAuthentication.AppleAuthenticationButtonType.CONTINUE}
                buttonStyle={isDarkMode
                  ? AppleAuthentication.AppleAuthenticationButtonStyle.WHITE
                  : AppleAuthentication.AppleAuthenticationButtonStyle.BLACK}
                cornerRadius={14}
                style={[styles.appleButton, { height: appleButtonHeight }]}
                onPress={handleAppleSignIn}
              />
            ) : null}

            {appleAvailable ? (
              <View style={[styles.dividerRow, { marginVertical: emailExpanded ? 2 : 6 }]}>
                <View style={[styles.dividerLine, { backgroundColor: colors.border }]} />
                <Text style={[styles.dividerText, { color: colors.textMuted }]}>{t.orDivider}</Text>
                <View style={[styles.dividerLine, { backgroundColor: colors.border }]} />
              </View>
            ) : null}

            {!emailExpanded ? (
              <TouchableOpacity
                style={[styles.emailChoiceBtn, { backgroundColor: colors.surface, borderColor: colors.borderStrong }]}
                onPress={() => setEmailExpanded(true)}
                activeOpacity={0.84}
              >
                <Ionicons name="mail-outline" size={19} color={colors.primary} />
                <Text style={[styles.emailChoiceText, { color: colors.text }]}>{copy.emailCta}</Text>
              </TouchableOpacity>
            ) : (
              <View style={[styles.form, { gap: emailExpanded && compact ? 8 : 12 }]}>
                <View style={[styles.fieldGroup, { gap: emailExpanded && compact ? 4 : 6 }]}>
                  <Text style={[styles.label, { color: colors.textSecondary }]}>{copy.nameLabel}</Text>
                  <View style={[styles.inputRow, { backgroundColor: colors.surface, borderColor: colors.border, height: inputHeight }]}>
                    <Ionicons name="person-outline" size={18} color={colors.textMuted} style={styles.inputIcon} />
                    <TextInput
                      style={[styles.input, { color: colors.text, height: inputHeight }]}
                      placeholder={t.namePlaceholder}
                      placeholderTextColor={colors.textMuted}
                      value={name}
                      onChangeText={setName}
                      autoCapitalize="words"
                      autoComplete="name"
                      returnKeyType="next"
                    />
                  </View>
                </View>

                <View style={[styles.fieldGroup, { gap: emailExpanded && compact ? 4 : 6 }]}>
                  <Text style={[styles.label, { color: colors.textSecondary }]}>{copy.emailLabel}</Text>
                  <View style={[styles.inputRow, { backgroundColor: colors.surface, borderColor: colors.border, height: inputHeight }]}>
                    <Ionicons name="mail-outline" size={18} color={colors.textMuted} style={styles.inputIcon} />
                    <TextInput
                      style={[styles.input, { color: colors.text, height: inputHeight }]}
                      placeholder={t.emailPlaceholder}
                      placeholderTextColor={colors.textMuted}
                      value={email}
                      onChangeText={setEmail}
                      autoCapitalize="none"
                      keyboardType="email-address"
                      autoComplete="email"
                      returnKeyType="next"
                    />
                  </View>
                </View>

                <View style={[styles.fieldGroup, { gap: emailExpanded && compact ? 4 : 6 }]}>
                  <Text style={[styles.label, { color: colors.textSecondary }]}>{t.passwordLabel}</Text>
                  <View style={[styles.inputRow, { backgroundColor: colors.surface, borderColor: colors.border, height: inputHeight }]}>
                    <Ionicons name="lock-closed-outline" size={18} color={colors.textMuted} style={styles.inputIcon} />
                    <TextInput
                      style={[styles.input, { color: colors.text, height: inputHeight }]}
                      placeholder={t.passwordPlaceholder}
                      placeholderTextColor={colors.textMuted}
                      value={password}
                      onChangeText={setPassword}
                      secureTextEntry={!showPassword}
                      autoComplete="new-password"
                      returnKeyType="next"
                    />
                    <TouchableOpacity onPress={() => setShowPassword((v) => !v)} style={styles.eyeBtn}>
                      <Ionicons name={showPassword ? 'eye-off-outline' : 'eye-outline'} size={18} color={colors.textMuted} />
                    </TouchableOpacity>
                  </View>
                </View>

                <View style={[styles.fieldGroup, { gap: emailExpanded && compact ? 4 : 6 }]}>
                  <Text style={[styles.label, { color: colors.textSecondary }]}>{t.confirmPasswordLabel}</Text>
                  <View style={[
                    styles.inputRow,
                    {
                      backgroundColor: colors.surface,
                      borderColor: passwordConfirm && password !== passwordConfirm ? colors.danger : colors.border,
                      height: inputHeight,
                    },
                  ]}>
                    <Ionicons name="lock-closed-outline" size={18} color={colors.textMuted} style={styles.inputIcon} />
                    <TextInput
                      style={[styles.input, { color: colors.text, height: inputHeight }]}
                      placeholder={t.confirmPasswordPlaceholder}
                      placeholderTextColor={colors.textMuted}
                      value={passwordConfirm}
                      onChangeText={setPasswordConfirm}
                      secureTextEntry={!showPasswordConfirm}
                      autoComplete="new-password"
                      returnKeyType="done"
                      onSubmitEditing={handleSignup}
                    />
                    <TouchableOpacity onPress={() => setShowPasswordConfirm((v) => !v)} style={styles.eyeBtn}>
                      <Ionicons name={showPasswordConfirm ? 'eye-off-outline' : 'eye-outline'} size={18} color={colors.textMuted} />
                    </TouchableOpacity>
                  </View>
                </View>
              </View>
            )}
          </View>

          <View style={{ gap: 12, marginTop: 16 }}>
            {error ? (
              <View style={[styles.errorBox, { backgroundColor: colors.dangerSoft }]}>
                <Ionicons name="alert-circle-outline" size={15} color={colors.danger} />
                <Text style={[styles.errorText, { color: colors.danger }]} selectable>{error}</Text>
              </View>
            ) : null}

            {emailExpanded ? (
              <TouchableOpacity
                style={[styles.primaryBtn, { backgroundColor: colors.primary, opacity: loading ? 0.72 : 1 }]}
                onPress={handleSignup}
                activeOpacity={0.84}
                disabled={loading}
              >
                {loading ? (
                  <ActivityIndicator color={colors.onPrimary} size="small" />
                ) : (
                  <Text style={[styles.primaryBtnText, { color: colors.onPrimary }]}>{copy.createCta}</Text>
                )}
              </TouchableOpacity>
            ) : null}

            <TouchableOpacity style={styles.loginLink} onPress={() => router.replace({ pathname: '/auth/login', params: { returnTo: params.returnTo, topup: params.topup } })} activeOpacity={0.78}>
              <Text style={[styles.loginLinkText, { color: colors.textSecondary }]}>
                {copy.already}{' '}
                <Text style={{ color: colors.primary, fontWeight: '800' }}>{copy.login}</Text>
              </Text>
            </TouchableOpacity>

            <Text style={[styles.legal, { color: colors.textMuted }]}>{copy.legal}</Text>
          </View>
        </View>
      </ScrollView>
    </KeyboardAvoidingView>
  );
}

const styles = StyleSheet.create({
  flex: { flex: 1 },
  scroll: { flexGrow: 1 },
  hero: {
    minHeight: 330,
    justifyContent: 'flex-end',
    paddingHorizontal: 24,
    paddingTop: 56,
    paddingBottom: 34,
  },
  heroImage: { resizeMode: 'cover' },
  heroOverlay: {
    ...StyleSheet.absoluteFillObject,
    backgroundColor: 'rgba(5, 12, 7, 0.46)',
  },
  backBtn: {
    position: 'absolute',
    top: 54,
    left: 22,
    width: 42,
    height: 42,
    borderRadius: 21,
    alignItems: 'center',
    justifyContent: 'center',
    backgroundColor: 'rgba(0, 0, 0, 0.28)',
    zIndex: 10,
    elevation: 10,
  },
  heroCopy: { gap: 10 },
  heroTitle: {
    color: '#ffffff',
    fontSize: 34,
    lineHeight: 39,
    fontWeight: '900',
  },
  heroSubline: {
    color: 'rgba(255, 255, 255, 0.88)',
    fontSize: 16,
    lineHeight: 22,
    fontWeight: '700',
  },
  sheet: {
    flex: 1,
    marginTop: -24,
    borderTopLeftRadius: 28,
    borderTopRightRadius: 28,
    paddingHorizontal: 22,
    paddingTop: 28,
    paddingBottom: 40,
    justifyContent: 'space-between',
  },
  pendingHint: {
    flexDirection: 'row',
    alignItems: 'center',
    gap: 10,
    borderRadius: 16,
    borderWidth: 1,
    paddingHorizontal: 14,
    paddingVertical: 12,
  },
  pendingHintText: { flex: 1, fontSize: 13, lineHeight: 18, fontWeight: '700' },
  appleButton: { width: '100%', height: 56 },
  dividerRow: { flexDirection: 'row', alignItems: 'center', gap: 12 },
  dividerLine: { flex: 1, height: 1 },
  dividerText: { fontSize: 12, fontWeight: '800' },
  emailChoiceBtn: {
    minHeight: 56,
    paddingVertical: 14,
    borderRadius: 14,
    borderWidth: 1.5,
    flexDirection: 'row',
    alignItems: 'center',
    justifyContent: 'center',
    gap: 10,
  },
  emailChoiceText: { fontSize: 16, fontWeight: '800' },
  form: { gap: 12 },
  fieldGroup: { gap: 6 },
  label: { fontSize: 13, fontWeight: '800', marginLeft: 2 },
  inputRow: {
    minHeight: 52,
    borderWidth: 1,
    borderRadius: 14,
    flexDirection: 'row',
    alignItems: 'center',
    paddingHorizontal: 14,
  },
  inputIcon: { marginRight: 10 },
  input: { flex: 1, minHeight: 52, fontSize: 15 },
  eyeBtn: { padding: 5, marginLeft: 6 },
  errorBox: {
    flexDirection: 'row',
    alignItems: 'center',
    gap: 7,
    borderRadius: 12,
    paddingHorizontal: 12,
    paddingVertical: 10,
  },
  errorText: { flex: 1, fontSize: 13, lineHeight: 18, fontWeight: '700' },
  primaryBtn: {
    minHeight: 56,
    paddingVertical: 14,
    borderRadius: 14,
    alignItems: 'center',
    justifyContent: 'center',
  },
  primaryBtnText: { fontSize: 17, fontWeight: '900' },
  loginLink: { alignItems: 'center', paddingTop: 4, paddingBottom: 2 },
  loginLinkText: { fontSize: 15, fontWeight: '700' },
  legal: { textAlign: 'center', fontSize: 11.5, lineHeight: 16, paddingHorizontal: 12 },
});