import React, { useMemo, useState, useCallback, useEffect } from 'react';
import { View, FlatList, StyleSheet, TouchableOpacity, Text, Dimensions, Modal, TextInput } from 'react-native';
import { useRoute, useNavigation, RouteProp } from '@react-navigation/native';
import { NativeStackNavigationProp } from '@react-navigation/native-stack';
import { MaterialIcons } from '@expo/vector-icons';
import { useSafeAreaInsets } from 'react-native-safe-area-context';
import {
  useDeleteFile, useFiles, useFreeLocalSpace,
  useAddTags, useMoveResources, useFolders, useCreateFolder,
} from '../hooks/useFiles';
import { SelectionPanel } from '../components/SelectionPanel';
import { ConfirmModal, type ConfirmOption } from '../components/ConfirmModal';
import { UnifiedFileItem } from '../types';
import { isFolder } from '../types';
import { FileThumbnail } from '../components/FileThumbnail';
import { fileStore } from '../services/fileStore';
import { downloadRegistry } from '../services/downloadRegistry';
import { apiClient } from '../api/client';
import { ENDPOINTS } from '../constants/api';
import { useQueryClient } from '@tanstack/react-query';
import { deleteAsync } from 'expo-file-system/legacy';

const NUM_COLUMNS = 3;
const SCREEN_WIDTH = Dimensions.get('window').width;
const ITEM_SIZE = (SCREEN_WIDTH - 16 * 2 - (NUM_COLUMNS - 1) * 6) / NUM_COLUMNS;
const PAGE_SIZE = 100;

type RootStackParamList = {
  Folder: { folderId: string; folderName: string };
  FileDetail: { fileIds: string[]; initialIndex: number };
  FileEdit: { fileIds: string[] };
};

type NavigationProp = NativeStackNavigationProp<RootStackParamList>;

type FolderRouteProp = RouteProp<RootStackParamList, 'Folder'>;

function FolderGridItem({ file, onPress, onLongPress, selected, onFolderPress }: {
  file: UnifiedFileItem;
  onPress?: () => void;
  onLongPress?: () => void;
  selected?: boolean;
  onFolderPress?: () => void;
}) {
  const folder = isFolder(file);

  return (
    <TouchableOpacity
      style={[styles.gridItem, selected && styles.gridItemSelected]}
      onPress={folder ? onFolderPress : onPress}
      onLongPress={onLongPress}
      delayLongPress={400}
      activeOpacity={0.7}
    >
      <FileThumbnail
        uri={file.url ?? file.localUri}
        thumbnailUrl={file.thumbnailUrl}
        mimeType={file.mimeType}
        fileName={file.name}
        size={ITEM_SIZE}
        syncStatus={file.syncStatus}
        isFolder={file.isFolder}
      />
      {selected && (
        <View style={styles.selectedOverlay}>
          <View style={styles.checkCircle}>
            <MaterialIcons name="check" size={18} color="#fff" />
          </View>
        </View>
      )}
      <Text style={styles.fileName} numberOfLines={1}>{file.name}</Text>
    </TouchableOpacity>
  );
}

export function FolderScreen() {
  const route = useRoute<FolderRouteProp>();
  const navigation = useNavigation<NavigationProp>();
  const { folderId, folderName } = route.params;
  const [page, setPage] = useState(1);
  const { data, isLoading, isFetching } = useFiles(folderId, page, PAGE_SIZE);
  const deleteFile = useDeleteFile();
  const freeLocalSpace = useFreeLocalSpace();
  const queryClient = useQueryClient();
  const [selectedIds, setSelectedIds] = useState<Set<string>>(new Set());

  const addTags = useAddTags();
  const moveFiles = useMoveResources();
  const createFolder = useCreateFolder();
  const { data: foldersData } = useFolders();
  const insets = useSafeAreaInsets();

  const loadMore = useCallback(() => {
    if (isFetching) return;
    const total = data?.meta?.total ?? 0;
    const loaded = data?.data?.length ?? 0;
    if (loaded < total) {
      setPage((p) => p + 1);
    }
  }, [isFetching, data?.meta?.total, data?.data?.length]);

  const hasMore = (data?.data?.length ?? 0) > 0 && (data?.data?.length ?? 0) < (data?.meta?.total ?? 0);

  const [tagModalVisible, setTagModalVisible] = useState(false);
  const [tagModalMode, setTagModalMode] = useState<'tag' | 'folder'>('tag');
  const [tagInput, setTagInput] = useState('');
  const [moveModalVisible, setMoveModalVisible] = useState(false);
  const [confirmDeleteState, setConfirmDeleteState] = useState<{ message: string; options: ConfirmOption[] } | null>(null);

  const selectionMode = selectedIds.size > 0;

  useEffect(() => {
    navigation.setOptions({ title: folderName });
  }, [navigation, folderName]);

  const files = useMemo(() => {
    return data?.data ?? [];
  }, [data]);

  const fileIdToIndex = useMemo(() => {
    const map = new Map<string, number>();
    files.forEach((f, i) => map.set(f.id, i));
    return map;
  }, [files]);

  const toggleSelection = useCallback((id: string) => {
    setSelectedIds((prev) => {
      const next = new Set(prev);
      if (next.has(id)) next.delete(id);
      else next.add(id);
      return next;
    });
  }, []);

  const clearSelection = useCallback(() => {
    setSelectedIds(new Set());
  }, []);

  const handleDelete = useCallback(() => {
    const ids = Array.from(selectedIds);
    if (ids.length === 0) return;
    const hasSynced = ids.some((id) => {
      const f = files.find((fi) => fi.id === id);
      return f?.syncStatus === 'synced';
    });
    const label = ids.length === 1 ? 'ce fichier' : `ces ${ids.length} fichiers`;
    const options: ConfirmOption[] = [];
    if (hasSynced) {
      options.push({
        label: 'Du device uniquement',
        onPress: async () => {
          const syncedIds = ids.filter((id) => {
            const f = files.find((fi) => fi.id === id);
            return f?.syncStatus === 'synced';
          });
          if (syncedIds.length > 0) {
            await freeLocalSpace.mutateAsync(syncedIds);
          }
          setSelectedIds(new Set());
        },
      });
    }
    options.push({
      label: 'Du device + serveur',
      destructive: true,
      onPress: async () => {
        for (const id of ids) {
          const f = files.find((fi) => fi.id === id);
          if (f?.backendResourceId) {
            await apiClient.delete(`${ENDPOINTS.RESOURCES}/${f.backendResourceId}`);
            fileStore.deleteByBackendId(f.backendResourceId);
          } else {
            fileStore.deleteById(id);
          }
          if (f?.localUri) {
            try { await deleteAsync(f.localUri, { idempotent: true }); } catch {}
          }
          downloadRegistry.remove(id);
        }
        await queryClient.invalidateQueries({ queryKey: ['resources'] });
        setSelectedIds(new Set());
      },
    });
    options.push({ label: 'Annuler' });
    setConfirmDeleteState({ message: `Supprimer ${label} ?`, options });
  }, [selectedIds, files, deleteFile, freeLocalSpace, queryClient]);

  const handleEdit = useCallback(() => {
    const ids = Array.from(selectedIds);
    if (ids.length === 0) return;
    navigation.navigate('FileEdit', { fileIds: ids });
    setSelectedIds(new Set());
  }, [selectedIds, navigation]);

  const openTagModal = useCallback((mode: 'tag' | 'folder') => {
    setTagModalMode(mode);
    setTagInput('');
    setTagModalVisible(true);
  }, []);

  const handleAddTag = useCallback(async () => {
    const name = tagInput.trim();
    if (!name) return;
    const ids = Array.from(selectedIds);
    for (const id of ids) {
      await addTags.mutateAsync({ fileId: id, tags: [name] });
    }
    setTagModalVisible(false);
    setSelectedIds(new Set());
  }, [tagInput, selectedIds, addTags]);

  const handleCreateFolderFromModal = useCallback(async () => {
    const name = tagInput.trim();
    if (!name) return;
    const ids = Array.from(selectedIds);
    try {
      const newFolder = await createFolder.mutateAsync({ name, parentResourceId: folderId });
      await moveFiles.mutateAsync({ resourceIds: ids, parentResourceId: newFolder.id });
      setTagModalVisible(false);
      setSelectedIds(new Set());
      navigation.navigate('Folder', { folderId: newFolder.id, folderName: newFolder.name });
    } catch {}
  }, [tagInput, selectedIds, createFolder, moveFiles, navigation, folderId]);

  const handleMove = useCallback(async (folderId: string | null) => {
    const ids = Array.from(selectedIds);
    await moveFiles.mutateAsync({ resourceIds: ids, parentResourceId: folderId });
    setMoveModalVisible(false);
    setSelectedIds(new Set());
  }, [selectedIds, moveFiles]);

  const handleItemPress = useCallback((file: UnifiedFileItem) => {
    if (selectionMode) {
      toggleSelection(file.id);
    } else if (isFolder(file)) {
      navigation.push('Folder', { folderId: file.id, folderName: file.name });
    } else {
      navigation.navigate('FileDetail', {
        fileIds: files.map((f) => f.id),
        initialIndex: fileIdToIndex.get(file.id) ?? 0,
      });
    }
  }, [selectionMode, toggleSelection, navigation, files, fileIdToIndex]);

  const handleItemLongPress = useCallback((file: UnifiedFileItem) => {
    if (!selectionMode) toggleSelection(file.id);
  }, [selectionMode, toggleSelection]);

  if (isLoading) {
    return (
      <View style={styles.center}>
        <Text style={styles.infoText}>Chargement...</Text>
      </View>
    );
  }

  return (
    <View style={styles.container}>
      <FlatList
        data={files}
        keyExtractor={(item) => item.id}
        contentContainerStyle={styles.list}
        onEndReached={loadMore}
        onEndReachedThreshold={0.5}
        ListEmptyComponent={
          <View style={styles.empty}>
            <MaterialIcons name="folder-open" size={48} color="#ccc" />
            <Text style={styles.emptyText}>Dossier vide</Text>
          </View>
        }
        ListFooterComponent={
          isFetching ? (
            <View style={styles.footer}>
              <Text style={styles.footerText}>Chargement...</Text>
            </View>
          ) : hasMore ? (
            <TouchableOpacity style={styles.footer} onPress={loadMore}>
              <Text style={styles.footerLink}>Charger plus</Text>
            </TouchableOpacity>
          ) : null
        }
        renderItem={({ item: file }) => (
          <FolderGridItem
            file={file}
            selected={selectedIds.has(file.id)}
            onPress={() => handleItemPress(file)}
            onLongPress={() => handleItemLongPress(file)}
            onFolderPress={() => navigation.push('Folder', { folderId: file.id, folderName: file.name })}
          />
        )}
      />

      {selectionMode && (
        <SelectionPanel
          selectedCount={selectedIds.size}
          onClose={clearSelection}
          onDelete={handleDelete}
          onEdit={handleEdit}
          onTags={() => openTagModal('tag')}
          onFolder={() => openTagModal('folder')}
          onMove={() => setMoveModalVisible(true)}
          insetsBottom={insets.bottom}
        />
      )}

      <Modal visible={tagModalVisible} transparent animationType="fade" onRequestClose={() => setTagModalVisible(false)}>
        <TouchableOpacity style={styles.modalOverlay} activeOpacity={1} onPress={() => setTagModalVisible(false)}>
          <TouchableOpacity activeOpacity={1} style={styles.modalContent} onPress={() => {}}>
            <Text style={styles.modalTitle}>
              {tagModalMode === 'folder' ? 'Créer un dossier' : 'Ajouter un tag'}
            </Text>
            <TextInput
              style={styles.modalInput}
              placeholder={tagModalMode === 'folder' ? 'Nom du dossier...' : 'Nom du tag...'}
              placeholderTextColor="#999"
              value={tagInput}
              onChangeText={setTagInput}
              autoFocus
              returnKeyType="done"
              onSubmitEditing={tagModalMode === 'folder' ? handleCreateFolderFromModal : handleAddTag}
            />
            <View style={styles.modalActions}>
              <TouchableOpacity style={styles.modalCancelBtn} onPress={() => setTagModalVisible(false)}>
                <Text style={styles.modalCancelText}>Annuler</Text>
              </TouchableOpacity>
              <TouchableOpacity
                style={[styles.modalConfirmBtn, !tagInput.trim() && styles.modalConfirmDisabled]}
                onPress={tagModalMode === 'folder' ? handleCreateFolderFromModal : handleAddTag}
                disabled={!tagInput.trim()}
              >
                <Text style={styles.modalConfirmText}>{tagModalMode === 'folder' ? 'Créer' : 'Ajouter'}</Text>
              </TouchableOpacity>
            </View>
          </TouchableOpacity>
        </TouchableOpacity>
      </Modal>

      <Modal visible={moveModalVisible} transparent animationType="fade" onRequestClose={() => setMoveModalVisible(false)}>
        <TouchableOpacity style={styles.modalOverlay} activeOpacity={1} onPress={() => setMoveModalVisible(false)}>
          <TouchableOpacity activeOpacity={1} style={styles.modalContent} onPress={() => {}}>
            <Text style={styles.modalTitle}>Déplacer vers...</Text>
            <TouchableOpacity
              style={styles.folderOption}
              onPress={() => handleMove(null)}
            >
              <MaterialIcons name="home" size={20} color="#666" />
              <Text style={styles.folderOptionText}>Racine</Text>
            </TouchableOpacity>
            {(foldersData ?? []).map((folder) => (
              <TouchableOpacity
                key={folder.id}
                style={styles.folderOption}
                onPress={() => handleMove(folder.id)}
              >
                <MaterialIcons name="folder" size={20} color="#F57C00" />
                <Text style={styles.folderOptionText}>{folder.name}</Text>
              </TouchableOpacity>
            ))}
          </TouchableOpacity>
        </TouchableOpacity>
      </Modal>

      <ConfirmModal
        visible={confirmDeleteState !== null}
        title="Supprimer"
        message={confirmDeleteState?.message}
        options={confirmDeleteState?.options ?? []}
        onClose={() => setConfirmDeleteState(null)}
      />
    </View>
  );
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: '#f5f5f5',
  },
  center: {
    flex: 1,
    justifyContent: 'center',
    alignItems: 'center',
  },
  infoText: {
    fontSize: 16,
    color: '#666',
  },
  list: {
    padding: 15,
  },
  empty: {
    paddingVertical: 60,
    alignItems: 'center',
    gap: 12,
  },
  emptyText: {
    fontSize: 16,
    color: '#999',
  },
  gridItem: {
    width: ITEM_SIZE,
  },
  gridItemSelected: {
    opacity: 0.85,
  },
  selectedOverlay: {
    position: 'absolute',
    top: 0,
    left: 0,
    right: 0,
    bottom: 18,
    justifyContent: 'flex-start',
    alignItems: 'flex-end',
    padding: 4,
  },
  checkCircle: {
    width: 24,
    height: 24,
    borderRadius: 12,
    backgroundColor: '#1976D2',
    justifyContent: 'center',
    alignItems: 'center',
  },
  fileName: {
    fontSize: 11,
    color: '#666',
    marginTop: 4,
    textAlign: 'center',
  },
  selectionBar: {
    backgroundColor: '#fff',
    borderTopWidth: 1,
    borderTopColor: '#e0e0e0',
    paddingHorizontal: 16,
    paddingVertical: 12,
  },
  selectionHeader: {
    flexDirection: 'row',
    alignItems: 'center',
    justifyContent: 'space-between',
    marginBottom: 12,
  },
  cancelBtn: {
    padding: 4,
  },
  selectionCount: {
    fontSize: 16,
    fontWeight: '600',
    color: '#333',
  },
  deleteBtn: {
    flexDirection: 'row',
    alignItems: 'center',
    justifyContent: 'center',
    paddingVertical: 10,
    borderRadius: 8,
    borderWidth: 1.5,
    borderColor: '#F44336',
    gap: 6,
  },
  deleteText: {
    fontSize: 15,
    fontWeight: '600',
    color: '#F44336',
  },
  modalOverlay: {
    flex: 1,
    backgroundColor: 'rgba(0,0,0,0.4)',
    justifyContent: 'center',
    alignItems: 'center',
  },
  modalContent: {
    backgroundColor: '#fff',
    borderRadius: 12,
    padding: 20,
    width: '80%',
  },
  modalTitle: {
    fontSize: 18,
    fontWeight: '700',
    color: '#333',
    marginBottom: 16,
  },
  modalInput: {
    borderWidth: 1,
    borderColor: '#ddd',
    borderRadius: 8,
    paddingHorizontal: 12,
    paddingVertical: 10,
    fontSize: 16,
    color: '#333',
    marginBottom: 16,
  },
  modalActions: {
    flexDirection: 'row',
    justifyContent: 'flex-end',
    gap: 12,
  },
  modalCancelBtn: {
    paddingHorizontal: 16,
    paddingVertical: 8,
  },
  modalCancelText: {
    fontSize: 15,
    color: '#666',
  },
  modalConfirmBtn: {
    paddingHorizontal: 16,
    paddingVertical: 8,
    backgroundColor: '#1976D2',
    borderRadius: 8,
  },
  modalConfirmDisabled: {
    backgroundColor: '#ccc',
  },
  modalConfirmText: {
    fontSize: 15,
    color: '#fff',
    fontWeight: '600',
  },
  folderOption: {
    flexDirection: 'row',
    alignItems: 'center',
    paddingVertical: 12,
    paddingHorizontal: 8,
    gap: 10,
    borderBottomWidth: 1,
    borderBottomColor: '#f0f0f0',
  },
  folderOptionText: {
    fontSize: 16,
    color: '#333',
  },
  footer: {
    paddingVertical: 20,
    alignItems: 'center',
  },
  footerText: {
    fontSize: 14,
    color: '#999',
  },
  footerLink: {
    fontSize: 14,
    color: '#1976D2',
    fontWeight: '600',
  },
});