import React, { useState, useEffect, useCallback } from 'react';
import {
  View, Text, StyleSheet, FlatList, TouchableOpacity,
  TextInput, Alert, Modal, ActivityIndicator, BackHandler,
  Platform,
} from 'react-native';
import * as FileSystem from 'expo-file-system/legacy';
import * as DocumentPicker from 'expo-document-picker';
import * as Sharing from 'expo-sharing';
import { useSafeAreaInsets } from 'react-native-safe-area-context';
import { theme, isEditable, getLangColor } from '../theme';

const ROOT = FileSystem.documentDirectory || 'file:///data/user/0/com.chahuadev.codeeditor/files/';

function sortEntries(entries) {
  return [...entries].sort((a, b) => {
    if (a.isDirectory !== b.isDirectory) return a.isDirectory ? -1 : 1;
    return a.name.localeCompare(b.name);
  });
}

function FileIcon({ name, isDirectory, size = 16 }) {
  if (isDirectory) return <Text style={[styles.fileIcon, { color: theme.colors.accentYellow, fontSize: size }]}>📁</Text>;
  const ext = name.split('.').pop().toLowerCase();
  const color = getLangColor(name);
  const icons = { js: '󰌞', ts: '󰛦', py: '🐍', html: '', css: '🎨', json: '{}', md: '📝', sh: '>', txt: '📄', pdf: '📕', csv: '📊', xls: '📊', xlsx: '📊' };
  const icon = icons[ext] || '📄';
  return <Text style={[styles.fileIcon, { color, fontSize: size }]}>{icon}</Text>;
}

export default function FileExplorerScreen({ navigation }) {
  const insets = useSafeAreaInsets();
  const [currentPath, setCurrentPath] = useState(ROOT || '');
  const [pathStack, setPathStack] = useState([]);
  const [entries, setEntries] = useState([]);
  const [loading, setLoading] = useState(false);
  const [renameModal, setRenameModal] = useState(null);
  const [newNameInput, setNewNameInput] = useState('');
  const [newFileModal, setNewFileModal] = useState(false);
  const [newFileName, setNewFileName] = useState('');
  const [newFolderModal, setNewFolderModal] = useState(false);
  const [newFolderName, setNewFolderName] = useState('');
  const [searchQuery, setSearchQuery] = useState('');

  const loadDir = useCallback(async (path) => {
    setLoading(true);
    try {
      const items = await FileSystem.readDirectoryAsync(path);
      const detailed = await Promise.all(
        items.map(async (name) => {
          const uri = path + name;
          try {
            const info = await FileSystem.getInfoAsync(uri);
            return { name, uri, isDirectory: info.isDirectory, size: info.size || 0 };
          } catch {
            return { name, uri, isDirectory: false, size: 0 };
          }
        })
      );
      setEntries(sortEntries(detailed));
    } catch (e) {
      Alert.alert('Error', 'Could not read directory: ' + e.message);
    } finally {
      setLoading(false);
    }
  }, []);

  useEffect(() => { loadDir(currentPath); }, [currentPath, loadDir]);

  // Hardware back button
  useEffect(() => {
    const handler = BackHandler.addEventListener('hardwareBackPress', () => {
      if (pathStack.length > 0) {
        const prev = pathStack[pathStack.length - 1];
        setPathStack(s => s.slice(0, -1));
        setCurrentPath(prev);
        return true;
      }
      return false;
    });
    return () => handler.remove();
  }, [pathStack]);

  function openEntry(entry) {
    if (entry.isDirectory) {
      setPathStack(s => [...s, currentPath]);
      setCurrentPath(entry.uri + '/');
    } else if (isEditable(entry.name)) {
      navigation.navigate('Editor', { fileUri: entry.uri, fileName: entry.name });
    } else {
      Alert.alert('Cannot edit', `"${entry.name}" is not a text file.\n\nUse Share to open with another app.`, [
        { text: 'Share', onPress: () => Sharing.shareAsync(entry.uri) },
        { text: 'OK' },
      ]);
    }
  }

  function goUp() {
    if (pathStack.length > 0) {
      const prev = pathStack[pathStack.length - 1];
      setPathStack(s => s.slice(0, -1));
      setCurrentPath(prev);
    }
  }

  async function deleteEntry(entry) {
    Alert.alert('Delete', `Delete "${entry.name}"?`, [
      { text: 'Cancel', style: 'cancel' },
      {
        text: 'Delete', style: 'destructive',
        onPress: async () => {
          try {
            await FileSystem.deleteAsync(entry.uri, { idempotent: true });
            loadDir(currentPath);
          } catch (e) {
            Alert.alert('Error', e.message);
          }
        }
      }
    ]);
  }

  async function doRename() {
    if (!newNameInput.trim()) return;
    const oldUri = renameModal.uri;
    const newUri = currentPath + newNameInput.trim() + (renameModal.isDirectory ? '/' : '');
    try {
      await FileSystem.moveAsync({ from: oldUri, to: newUri });
      setRenameModal(null);
      loadDir(currentPath);
    } catch (e) {
      Alert.alert('Error', e.message);
    }
  }

  async function doCreateFile() {
    const name = newFileName.trim();
    if (!name) return;
    const uri = currentPath + name;
    try {
      await FileSystem.writeAsStringAsync(uri, '');
      setNewFileModal(false);
      setNewFileName('');
      loadDir(currentPath);
    } catch (e) {
      Alert.alert('Error', e.message);
    }
  }

  async function doCreateFolder() {
    const name = newFolderName.trim();
    if (!name) return;
    const uri = currentPath + name;
    try {
      await FileSystem.makeDirectoryAsync(uri, { intermediates: true });
      setNewFolderModal(false);
      setNewFolderName('');
      loadDir(currentPath);
    } catch (e) {
      Alert.alert('Error', e.message);
    }
  }

  async function importFile() {
    try {
      const result = await DocumentPicker.getDocumentAsync({ copyToCacheDirectory: false });
      if (!result.canceled && result.assets?.length > 0) {
        const asset = result.assets[0];
        const dest = currentPath + asset.name;
        await FileSystem.copyAsync({ from: asset.uri, to: dest });
        loadDir(currentPath);
      }
    } catch (e) {
      Alert.alert('Error', e.message);
    }
  }

  const breadcrumb = (() => {
    if (!currentPath || !ROOT) return '/';
    const relative = currentPath.replace(ROOT, '');
    return relative ? '/ ' + relative.replace(/\/$/, '') : '/';
  })();

  const filtered = searchQuery
    ? entries.filter(e => e.name.toLowerCase().includes(searchQuery.toLowerCase()))
    : entries;

  function formatSize(bytes) {
    if (!bytes) return '';
    if (bytes < 1024) return bytes + ' B';
    if (bytes < 1024 * 1024) return (bytes / 1024).toFixed(1) + ' KB';
    return (bytes / (1024 * 1024)).toFixed(1) + ' MB';
  }

  return (
    <View style={[styles.container, { paddingTop: insets.top }]}>
      {/* Header */}
      <View style={styles.header}>
        <View style={styles.headerTop}>
          <Text style={styles.title}>Files</Text>
          <View style={styles.headerActions}>
            <TouchableOpacity style={styles.actionBtn} onPress={importFile}>
              <Text style={styles.actionBtnText}>Import</Text>
            </TouchableOpacity>
            <TouchableOpacity style={styles.actionBtn} onPress={() => setNewFolderModal(true)}>
              <Text style={styles.actionBtnText}>+ Folder</Text>
            </TouchableOpacity>
            <TouchableOpacity style={[styles.actionBtn, styles.actionBtnAccent]} onPress={() => setNewFileModal(true)}>
              <Text style={[styles.actionBtnText, { color: theme.colors.bg }]}>+ File</Text>
            </TouchableOpacity>
          </View>
        </View>

        {/* Breadcrumb */}
        <View style={styles.breadcrumbRow}>
          {pathStack.length > 0 && (
            <TouchableOpacity onPress={goUp} style={styles.backBtn}>
              <Text style={styles.backBtnText}>‹</Text>
            </TouchableOpacity>
          )}
          <Text style={styles.breadcrumb} numberOfLines={1}>{breadcrumb}</Text>
        </View>

        {/* Search */}
        <TextInput
          style={styles.searchInput}
          placeholder="Search files…"
          placeholderTextColor={theme.colors.textMuted}
          value={searchQuery}
          onChangeText={setSearchQuery}
        />
      </View>

      {/* File List */}
      {loading ? (
        <View style={styles.loadingWrap}>
          <ActivityIndicator color={theme.colors.accent} size="large" />
        </View>
      ) : filtered.length === 0 ? (
        <View style={styles.emptyWrap}>
          <Text style={styles.emptyText}>{searchQuery ? 'No matches' : 'Empty folder'}</Text>
          <Text style={styles.emptyHint}>Tap "+ File" to create a new file</Text>
        </View>
      ) : (
        <FlatList
          data={filtered}
          keyExtractor={item => item.uri}
          contentContainerStyle={{ paddingBottom: insets.bottom + 16 }}
          renderItem={({ item }) => (
            <TouchableOpacity
              style={styles.entryRow}
              onPress={() => openEntry(item)}
              onLongPress={() => {
                Alert.alert(item.name, null, [
                  { text: 'Rename', onPress: () => { setNewNameInput(item.name); setRenameModal(item); } },
                  { text: 'Share', onPress: () => Sharing.shareAsync(item.uri) },
                  { text: 'Delete', style: 'destructive', onPress: () => deleteEntry(item) },
                  { text: 'Cancel', style: 'cancel' },
                ]);
              }}
            >
              <FileIcon name={item.name} isDirectory={item.isDirectory} size={18} />
              <View style={styles.entryInfo}>
                <Text style={styles.entryName} numberOfLines={1}>{item.name}</Text>
                {!item.isDirectory && item.size > 0 && (
                  <Text style={styles.entryMeta}>{formatSize(item.size)}</Text>
                )}
              </View>
              <Text style={styles.entryArrow}>{item.isDirectory ? '›' : isEditable(item.name) ? '✎' : '↗'}</Text>
            </TouchableOpacity>
          )}
        />
      )}

      {/* Rename Modal */}
      <Modal visible={!!renameModal} transparent animationType="fade">
        <View style={styles.modalOverlay}>
          <View style={styles.modalBox}>
            <Text style={styles.modalTitle}>Rename</Text>
            <TextInput
              style={styles.modalInput}
              value={newNameInput}
              onChangeText={setNewNameInput}
              autoFocus
              selectTextOnFocus
            />
            <View style={styles.modalRow}>
              <TouchableOpacity style={styles.modalBtn} onPress={() => setRenameModal(null)}>
                <Text style={styles.modalBtnText}>Cancel</Text>
              </TouchableOpacity>
              <TouchableOpacity style={[styles.modalBtn, styles.modalBtnAccent]} onPress={doRename}>
                <Text style={[styles.modalBtnText, { color: theme.colors.bg }]}>Rename</Text>
              </TouchableOpacity>
            </View>
          </View>
        </View>
      </Modal>

      {/* New File Modal */}
      <Modal visible={newFileModal} transparent animationType="fade">
        <View style={styles.modalOverlay}>
          <View style={styles.modalBox}>
            <Text style={styles.modalTitle}>New File</Text>
            <TextInput
              style={styles.modalInput}
              value={newFileName}
              onChangeText={setNewFileName}
              placeholder="filename.js"
              placeholderTextColor={theme.colors.textMuted}
              autoFocus
            />
            <View style={styles.modalRow}>
              <TouchableOpacity style={styles.modalBtn} onPress={() => { setNewFileModal(false); setNewFileName(''); }}>
                <Text style={styles.modalBtnText}>Cancel</Text>
              </TouchableOpacity>
              <TouchableOpacity style={[styles.modalBtn, styles.modalBtnAccent]} onPress={doCreateFile}>
                <Text style={[styles.modalBtnText, { color: theme.colors.bg }]}>Create</Text>
              </TouchableOpacity>
            </View>
          </View>
        </View>
      </Modal>

      {/* New Folder Modal */}
      <Modal visible={newFolderModal} transparent animationType="fade">
        <View style={styles.modalOverlay}>
          <View style={styles.modalBox}>
            <Text style={styles.modalTitle}>New Folder</Text>
            <TextInput
              style={styles.modalInput}
              value={newFolderName}
              onChangeText={setNewFolderName}
              placeholder="folder-name"
              placeholderTextColor={theme.colors.textMuted}
              autoFocus
            />
            <View style={styles.modalRow}>
              <TouchableOpacity style={styles.modalBtn} onPress={() => { setNewFolderModal(false); setNewFolderName(''); }}>
                <Text style={styles.modalBtnText}>Cancel</Text>
              </TouchableOpacity>
              <TouchableOpacity style={[styles.modalBtn, styles.modalBtnAccent]} onPress={doCreateFolder}>
                <Text style={[styles.modalBtnText, { color: theme.colors.bg }]}>Create</Text>
              </TouchableOpacity>
            </View>
          </View>
        </View>
      </Modal>
    </View>
  );
}

const styles = StyleSheet.create({
  container: { flex: 1, backgroundColor: theme.colors.bg },
  header: { backgroundColor: theme.colors.surface, paddingHorizontal: 16, paddingBottom: 10, borderBottomWidth: 1, borderBottomColor: theme.colors.border },
  headerTop: { flexDirection: 'row', alignItems: 'center', justifyContent: 'space-between', paddingTop: 12, paddingBottom: 6 },
  title: { color: theme.colors.text, fontSize: 20, fontWeight: '800' },
  headerActions: { flexDirection: 'row', gap: 8 },
  actionBtn: { paddingHorizontal: 10, paddingVertical: 6, borderRadius: 8, borderWidth: 1, borderColor: theme.colors.border },
  actionBtnAccent: { backgroundColor: theme.colors.accent, borderColor: theme.colors.accent },
  actionBtnText: { color: theme.colors.text, fontSize: 12, fontWeight: '700' },
  breadcrumbRow: { flexDirection: 'row', alignItems: 'center', gap: 8, marginBottom: 8 },
  backBtn: { padding: 4 },
  backBtnText: { color: theme.colors.accent, fontSize: 22, lineHeight: 24 },
  breadcrumb: { color: theme.colors.textMuted, fontSize: 12, flex: 1 },
  searchInput: { backgroundColor: theme.colors.surface2, color: theme.colors.text, borderRadius: 8, paddingHorizontal: 12, paddingVertical: 8, fontSize: 14 },
  loadingWrap: { flex: 1, alignItems: 'center', justifyContent: 'center' },
  emptyWrap: { flex: 1, alignItems: 'center', justifyContent: 'center', gap: 8 },
  emptyText: { color: theme.colors.textMuted, fontSize: 16 },
  emptyHint: { color: theme.colors.textMuted, fontSize: 12 },
  entryRow: { flexDirection: 'row', alignItems: 'center', paddingHorizontal: 16, paddingVertical: 13, borderBottomWidth: 1, borderBottomColor: theme.colors.border + '55', gap: 12 },
  fileIcon: { width: 24, textAlign: 'center' },
  entryInfo: { flex: 1 },
  entryName: { color: theme.colors.text, fontSize: 14, fontWeight: '600' },
  entryMeta: { color: theme.colors.textMuted, fontSize: 11, marginTop: 1 },
  entryArrow: { color: theme.colors.textMuted, fontSize: 16 },
  modalOverlay: { flex: 1, backgroundColor: '#000000aa', alignItems: 'center', justifyContent: 'center' },
  modalBox: { backgroundColor: theme.colors.surface, borderRadius: 14, padding: 20, width: 280, gap: 12, borderWidth: 1, borderColor: theme.colors.border },
  modalTitle: { color: theme.colors.text, fontSize: 16, fontWeight: '800' },
  modalInput: { backgroundColor: theme.colors.surface2, color: theme.colors.text, borderRadius: 8, paddingHorizontal: 12, paddingVertical: 10, fontSize: 14 },
  modalRow: { flexDirection: 'row', justifyContent: 'flex-end', gap: 10 },
  modalBtn: { paddingHorizontal: 14, paddingVertical: 8, borderRadius: 8, borderWidth: 1, borderColor: theme.colors.border },
  modalBtnAccent: { backgroundColor: theme.colors.accent, borderColor: theme.colors.accent },
  modalBtnText: { color: theme.colors.text, fontSize: 13, fontWeight: '700' },
});