import React, { useRef, useState, useEffect } from 'react';
import {
  View,
  Text,
  StyleSheet,
  FlatList,
  Image,
  Dimensions,
  ActivityIndicator,
  ScrollView,
} from 'react-native';
import { RouteProp, useRoute } from '@react-navigation/native';
import Pdf from 'react-native-pdf';
import { downloadAsync, documentDirectory, getInfoAsync } from 'expo-file-system/legacy';
import { useFile, useFileImage } from '../hooks/useFiles';
import { apiClient } from '../api/client';
import { TagChip } from '../components/TagChip';
import { FileThumbnail } from '../components/FileThumbnail';

const SCREEN_WIDTH = Dimensions.get('window').width;

type RootStackParamList = {
  FileDetail: { fileIds: string[]; initialIndex: number };
};

type FileDetailRouteProp = RouteProp<RootStackParamList, 'FileDetail'>;

function DetailItem({ fileId }: { fileId: string }) {
  const { data: imageData, isLoading: imageLoading } = useFileImage(fileId);
  const { data: fileData } = useFile(fileId);
  const uri = imageData?.data?.url;
  const file = fileData as any;
  const isPdf = file?.data?.mimeType === 'application/pdf';
  const [localPdfUri, setLocalPdfUri] = useState<string | null>(null);
  const [pdfLoading, setPdfLoading] = useState(false);

  useEffect(() => {
    if (!isPdf || !uri) return;
    let cancelled = false;

    async function downloadPdf() {
      if (!uri) return;
      setPdfLoading(true);
      const localUri = `${documentDirectory}pdf_${fileId}.pdf`;
      try {
        const info = await getInfoAsync(localUri);
        if (info.exists && info.size > 100) {
          if (!cancelled) setLocalPdfUri(localUri);
          return;
        }
        const headers: Record<string, string> = {};
        const token = apiClient.getAccessToken();
        if (token) headers['Authorization'] = `Bearer ${token}`;
        await downloadAsync(uri, localUri, { headers });
        if (!cancelled) setLocalPdfUri(localUri);
      } catch (e) {
        console.log('PDF download error:', e);
      } finally {
        if (!cancelled) setPdfLoading(false);
      }
    }

    downloadPdf();
    return () => { cancelled = true; };
  }, [isPdf, uri, fileId]);

  return (
    <ScrollView style={styles.page} contentContainerStyle={styles.pageContent}>
      <View style={styles.imageContainer}>
        {isPdf ? (
          pdfLoading || !localPdfUri ? (
            <ActivityIndicator size="large" color="#fff" />
          ) : (
            <Pdf
              source={{ uri: localPdfUri }}
              style={styles.pdf}
              onLoadComplete={(numberOfPages) => {
                console.log(`PDF loaded: ${numberOfPages} pages`);
              }}
              onError={(error) => {
                console.log('PDF error:', error);
              }}
            />
          )
        ) : uri ? (
          <Image source={{ uri }} style={styles.image} resizeMode="contain" />
        ) : file ? (
          <FileThumbnail
            mimeType={file.mimeType ?? 'application/pdf'}
            fileName={file.name ?? fileId}
            size={SCREEN_WIDTH * 0.6}
            isLoading={imageLoading}
          />
        ) : (
          <ActivityIndicator size="large" color="#1976D2" />
        )}
      </View>

      <View style={styles.details}>
        <Text style={styles.fileName}>{imageData?.data?.name ?? file?.name ?? fileId}</Text>

        {imageData?.data?.size != null && (
          <Text style={styles.meta}>
            Taille : {(imageData.data.size / 1024).toFixed(1)} Ko
          </Text>
        )}

        {file?.createdAt && (
          <Text style={styles.meta}>
            Ajouté le {new Date(file.createdAt).toLocaleDateString('fr-FR', {
              day: 'numeric', month: 'long', year: 'numeric',
            })}
          </Text>
        )}

        {file?.tags && file.tags.length > 0 && (
          <View style={styles.tagsSection}>
            <Text style={styles.sectionLabel}>Tags</Text>
            <View style={styles.tagsRow}>
              {file.tags.map((tag: any) => (
                <TagChip key={tag.id} name={tag.name} />
              ))}
            </View>
          </View>
        )}

        {file?.ocrText && (
          <View style={styles.ocrSection}>
            <Text style={styles.sectionLabel}>Texte OCR</Text>
            <Text style={styles.ocrText}>{file.ocrText}</Text>
          </View>
        )}
      </View>
    </ScrollView>
  );
}

export function FileDetailScreen() {
  const route = useRoute<FileDetailRouteProp>();
  const { fileIds, initialIndex } = route.params;

  const flatListRef = useRef<FlatList>(null);
  const [currentIndex, setCurrentIndex] = useState(initialIndex);

  return (
    <View style={styles.container}>
      <FlatList
        ref={flatListRef}
        data={fileIds}
        keyExtractor={(item) => item}
        horizontal
        pagingEnabled
        showsHorizontalScrollIndicator={false}
        initialScrollIndex={initialIndex}
        getItemLayout={(_, index) => ({
          length: SCREEN_WIDTH,
          offset: SCREEN_WIDTH * index,
          index,
        })}
        onMomentumScrollEnd={(e) => {
          const index = Math.round(e.nativeEvent.contentOffset.x / SCREEN_WIDTH);
          setCurrentIndex(index);
        }}
        renderItem={({ item }) => (
          <View style={styles.pageWrapper}>
            <DetailItem fileId={item} />
          </View>
        )}
      />

      <View style={styles.pagination}>
        <Text style={styles.paginationText}>
          {currentIndex + 1} / {fileIds.length}
        </Text>
      </View>
    </View>
  );
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: '#000',
  },
  pageWrapper: {
    width: SCREEN_WIDTH,
  },
  page: {
    flex: 1,
  },
  pageContent: {
    flexGrow: 1,
  },
  imageContainer: {
    flex: 1,
    justifyContent: 'center',
    alignItems: 'center',
    backgroundColor: '#000',
  },
  image: {
    width: SCREEN_WIDTH,
    height: SCREEN_WIDTH,
  },
  pdf: {
    width: SCREEN_WIDTH,
    height: SCREEN_WIDTH,
    backgroundColor: '#fff',
  },
  placeholder: {
    width: SCREEN_WIDTH,
    height: SCREEN_WIDTH,
    justifyContent: 'center',
    alignItems: 'center',
    backgroundColor: '#1a1a2e',
  },
  placeholderText: {
    fontSize: 48,
    color: '#1976D2',
    fontWeight: '700',
  },
  details: {
    backgroundColor: '#fff',
    borderTopLeftRadius: 16,
    borderTopRightRadius: 16,
    marginTop: -16,
    padding: 20,
  },
  fileName: {
    fontSize: 18,
    fontWeight: '700',
    color: '#333',
    marginBottom: 8,
  },
  meta: {
    fontSize: 14,
    color: '#666',
    marginBottom: 4,
  },
  tagsRow: {
    flexDirection: 'row',
    flexWrap: 'wrap',
    gap: 6,
    marginTop: 8,
  },
  tagsSection: {
    marginTop: 12,
  },
  sectionLabel: {
    fontSize: 14,
    fontWeight: '600',
    color: '#333',
    marginBottom: 4,
  },
  ocrSection: {
    marginTop: 16,
  },
  ocrText: {
    fontSize: 14,
    color: '#555',
    lineHeight: 20,
    marginTop: 4,
  },
  pagination: {
    position: 'absolute',
    bottom: 16,
    alignSelf: 'center',
    backgroundColor: 'rgba(0,0,0,0.5)',
    borderRadius: 12,
    paddingHorizontal: 12,
    paddingVertical: 4,
  },
  paginationText: {
    color: '#fff',
    fontSize: 13,
  },
});