import React, { useEffect } from 'react';
import { ActivityIndicator, Image, StyleSheet, Text, TouchableOpacity, View } from 'react-native';
import { useRouter } from 'expo-router';
import { parseShareIntent, ShareIntentModule } from 'expo-share-intent';
import * as ExpoLinking from 'expo-linking';
import { SHARE_INTENT_KEY, storeSharedImageUri } from '../utils/shareHandoff';
import { resolveSharedImageUri, summarizeShareIntent } from '../utils/shareIntent';

const SHARE_INTENT_SCHEME = 'greenlens';
const SHARE_INTENT_OPTIONS = {
  scheme: SHARE_INTENT_SCHEME,
};
const isShareIntentUrl = (url: string | null | undefined) => Boolean(url?.includes(`${SHARE_INTENT_SCHEME}://dataUrl=`));

export default function ShareIntentCallbackScreen() {
  const router = useRouter();
  const [isWaiting, setIsWaiting] = React.useState(true);
  const [failureDetails, setFailureDetails] = React.useState<string | null>(null);
  const [previewUri, setPreviewUri] = React.useState<string | null>(null);
  const pendingKeyRef = React.useRef<string | null>(null);
  const getIntentCalledRef = React.useRef(false);
  const settledRef = React.useRef(false);
  const linkingUrl = ExpoLinking.useLinkingURL();

  useEffect(() => {
    const fallback = setTimeout(() => {
      if (settledRef.current) return;
      setIsWaiting(false);
      setFailureDetails((current) => current || 'Keine Antwort von der Share Extension.');
    }, 15000);

    return () => clearTimeout(fallback);
  }, []);

  useEffect(() => {
    const showFailure = (message: string) => {
      settledRef.current = true;
      ShareIntentModule?.clearShareIntent(SHARE_INTENT_KEY);
      setPreviewUri(null);
      setIsWaiting(false);
      setFailureDetails(message);
    };

    const changeSubscription = ShareIntentModule?.addListener('onChange', async (event) => {
      try {
        setIsWaiting(true);
        setFailureDetails(null);
        const shareIntent = parseShareIntent(event.value, SHARE_INTENT_OPTIONS);
        if (__DEV__) {
          console.debug('[ShareIntentCallback]', summarizeShareIntent(shareIntent));
        }
        const resolved = await resolveSharedImageUri(shareIntent);
        if (!resolved) {
          showFailure('Die Quelle hat keinen nutzbaren Bildanhang oder Bild-Link geliefert.');
          return;
        }
        settledRef.current = true;
        const sharedImageKey = storeSharedImageUri(resolved.uri);
        ShareIntentModule?.clearShareIntent(SHARE_INTENT_KEY);
        if (resolved.requiresConfirmation) {
          pendingKeyRef.current = sharedImageKey;
          setIsWaiting(false);
          setPreviewUri(resolved.uri);
          return;
        }
        router.replace({
          pathname: '/scanner',
          params: { sharedImageKey },
        });
      } catch (error) {
        console.error('[ShareIntentCallback] failed to parse share intent', error);
        showFailure('Die Share-Daten konnten nicht gelesen werden.');
      }
    });

    const errorSubscription = ShareIntentModule?.addListener('onError', (event) => {
      console.error('[ShareIntentCallback] native error', event.value);
      showFailure(event.value || 'Die Share Extension hat einen Fehler gemeldet.');
    });

    const url = linkingUrl || ExpoLinking.getLinkingURL();
    if (url && isShareIntentUrl(url) && !getIntentCalledRef.current) {
      getIntentCalledRef.current = true;
      ShareIntentModule?.getShareIntent(url);
    }

    return () => {
      changeSubscription?.remove();
      errorSubscription?.remove();
    };
  }, [linkingUrl, router]);

  return (
    <View style={styles.container}>
      {isWaiting ? (
        <ActivityIndicator color="#F4F7F1" size="large" />
      ) : previewUri ? (
        <View style={styles.messageBox}>
          <Text style={styles.title}>Pflanze gefunden</Text>
          <Text style={styles.body}>Ist das die Pflanze, die du scannen möchtest?</Text>
          <Image source={{ uri: previewUri }} style={styles.previewImage} resizeMode="cover" />
          <Text style={styles.hint}>
            Wenn das nicht die Pflanze ist, tippe „Scanner öffnen" und teile das Bild direkt in Safari.
          </Text>
          <TouchableOpacity
            style={styles.button}
            onPress={() => {
              if (pendingKeyRef.current) {
                router.replace({ pathname: '/scanner', params: { sharedImageKey: pendingKeyRef.current } });
              }
            }}
          >
            <Text style={styles.buttonText}>Diese Pflanze scannen</Text>
          </TouchableOpacity>
          <TouchableOpacity style={styles.buttonSecondary} onPress={() => router.replace('/scanner')}>
            <Text style={styles.buttonSecondaryText}>Scanner öffnen</Text>
          </TouchableOpacity>
        </View>
      ) : (
        <View style={styles.messageBox}>
          <Text style={styles.title}>Bild konnte nicht geladen werden.</Text>
          <Text style={styles.body}>
            Tippe und halte das Bild in Safari oder Instagram, wähle „Bild teilen" und teile es direkt mit GreenLens.
          </Text>
          {failureDetails ? (
            <Text style={styles.detail}>{failureDetails}</Text>
          ) : null}
          <TouchableOpacity style={styles.button} onPress={() => router.replace('/scanner')}>
            <Text style={styles.buttonText}>Scanner öffnen</Text>
          </TouchableOpacity>
        </View>
      )}
    </View>
  );
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    alignItems: 'center',
    justifyContent: 'center',
    backgroundColor: '#111813',
    padding: 24,
  },
  messageBox: {
    alignItems: 'center',
    gap: 14,
  },
  title: {
    color: '#F4F7F1',
    fontSize: 18,
    fontWeight: '700',
    textAlign: 'center',
  },
  body: {
    color: '#CAD3CB',
    fontSize: 14,
    lineHeight: 20,
    textAlign: 'center',
  },
  detail: {
    color: '#8F9A91',
    fontSize: 12,
    lineHeight: 17,
    textAlign: 'center',
  },
  previewImage: {
    width: '100%',
    aspectRatio: 4 / 3,
    borderRadius: 16,
    backgroundColor: '#1E2820',
  },
  button: {
    marginTop: 8,
    borderRadius: 12,
    backgroundColor: '#D7F5A2',
    paddingHorizontal: 18,
    paddingVertical: 12,
  },
  buttonText: {
    color: '#111813',
    fontSize: 14,
    fontWeight: '800',
  },
  hint: {
    color: '#8F9A91',
    fontSize: 11,
    lineHeight: 16,
    textAlign: 'center',
    marginTop: -6,
  },
  buttonSecondary: {
    marginTop: 4,
    borderRadius: 12,
    paddingHorizontal: 18,
    paddingVertical: 12,
  },
  buttonSecondaryText: {
    color: '#8F9A91',
    fontSize: 14,
    fontWeight: '600',
    textAlign: 'center',
  },
});