import { useQuery, useQueryClient } from "@tanstack/react-query";
import { useLocalSearchParams, useRouter } from "expo-router";
import React, { useEffect, useMemo, useState } from "react";
import { Platform, ScrollView, Text, View } from "react-native";
import { useApp } from "../../src/app-context";
import { RealtimeClient, reconcileMessages } from "../../src/realtime";
import { dialogApi, profileApi, publicApi, uploadAttachment } from "../../src/services";
import type { Message } from "../../src/types";
import { Button, ErrorNotice, Field, Header, Loading, styles } from "../../src/ui";

const statusLabel: Record<string, string> = {
  open: "Открыт",
  waiting_for_company: "Ожидает ответа компании",
  waiting_for_client: "Ожидает вашего ответа",
  closed: "Закрыт",
  accepted: "Принято",
  delivered: "Доставлено",
  failed: "Ошибка доставки",
  rejected: "Отклонено",
};

export default function ChatScreen() {
  const { dialogId } = useLocalSearchParams<{ dialogId: string }>();
  const app = useApp();
  const client = useQueryClient();
  const router = useRouter();
  const [text, setText] = useState("");
  const [error, setError] = useState<unknown>();
  const [sending, setSending] = useState(false);
  const [creating, setCreating] = useState(false);
  const config = useQuery({ queryKey: ["public-config"], queryFn: publicApi.config });
  const dialog = useQuery({ queryKey: ["dialog", dialogId], queryFn: () => dialogApi.get(dialogId), enabled: Boolean(dialogId) && app.authStatus === "authenticated" });
  const messages = useQuery({ queryKey: ["messages", dialogId], queryFn: () => dialogApi.messages(dialogId), enabled: Boolean(dialogId) && app.authStatus === "authenticated" });

  const realtime = useMemo(() => new RealtimeClient(
    dialogId ? [dialogId] : [],
    (event) => {
      if (event.type === "message.new") merge([event.message]);
      if (event.type === "message.status") {
        client.setQueryData(["messages", dialogId], (old: typeof messages.data) => old && ({
          ...old,
          items: old.items.map((item) => item.message_id === event.message_id ? { ...item, safety_status: event.safety_status, delivery_status: event.delivery_status } : item),
        }));
      }
      if (event.type === "dialog.status") void dialog.refetch();
    },
    (_, incoming) => merge(incoming),
    app.setRealtimeState,
  ), [dialogId]);

  function merge(incoming: Message[]) {
    client.setQueryData(["messages", dialogId], (old: typeof messages.data) =>
      old ? { ...old, items: reconcileMessages(old.items, incoming) } : { items: incoming, next_cursor: null },
    );
  }

  useEffect(() => {
    if (app.authStatus === "authenticated") realtime.start();
    return () => realtime.stop();
  }, [realtime, app.authStatus]);

  const sendText = async () => {
    const normalized = text.trim();
    if (!normalized || !dialogId) return;
    setSending(true); setError(undefined);
    try {
      const message = await dialogApi.sendText(dialogId, normalized, crypto.randomUUID());
      merge([message]); setText("");
    } catch (reason) { setError(reason); }
    finally { setSending(false); }
  };

  const chooseFile = () => {
    if (Platform.OS !== "web") {
      setError(new Error("Выбор файла в этой тестовой сборке доступен в web."));
      return;
    }
    const input = document.createElement("input");
    input.type = "file";
    input.accept = "image/*,application/pdf";
    input.onchange = () => { const file = input.files?.[0]; if (file) void sendFile(file); };
    input.click();
  };

  const sendFile = async (file: File) => {
    const limits = config.data?.attachments;
    const max = (limits?.max_size_mb ?? 5) * 1024 * 1024;
    const allowed = limits?.allowed_mime_types ?? ["image/jpeg", "image/png", "image/webp", "application/pdf"];
    if (file.size > max || !allowed.includes(file.type)) {
      setError(new Error("Недопустимый тип файла или превышен допустимый размер."));
      return;
    }
    setSending(true); setError(undefined);
    try {
      const uploaded = await uploadAttachment(dialogId, file);
      const message = await dialogApi.sendFile(dialogId, uploaded.attachmentId, uploaded.checksum, crypto.randomUUID());
      merge([message]);
    } catch (reason) { setError(reason); }
    finally { setSending(false); }
  };

  const downloadAttachment = async (attachmentId: string) => {
    try {
      const result = await profileApi.attachmentUrl(dialogId, attachmentId);
      if (typeof window !== "undefined") window.location.assign(result.download_url);
    } catch (reason) { setError(reason); }
  };

  const createDialog = async () => {
    setCreating(true); setError(undefined);
    try {
      const created = await dialogApi.create(crypto.randomUUID());
      router.replace(`/dialogs/${created.dialog_id}`);
    } catch (reason) { setError(reason); }
    finally { setCreating(false); }
  };

  const closed = dialog.data?.status === "closed";
  return <ScrollView contentContainerStyle={styles.page}>
    <Header status={app.authStatus} realtime={app.realtimeState} onLogout={app.authStatus === "authenticated" ? () => void app.signOut() : undefined} />
    <Text accessibilityRole="header" style={styles.title}>Чат</Text>
    {app.authStatus !== "authenticated" && <Text style={styles.error}>Для просмотра чата требуется авторизация.</Text>}
    {(dialog.isLoading || messages.isLoading) && <Loading />}
    {(dialog.error || messages.error) && <ErrorNotice error={dialog.error ?? messages.error} retry={() => { void dialog.refetch(); void messages.refetch(); }} />}
    <Text style={styles.badge}>Статус: {statusLabel[dialog.data?.status ?? ""] ?? "—"}</Text>
    <View accessibilityLiveRegion="polite" style={{ gap: 10 }}>
      {(messages.data?.items ?? []).map((message) => <View key={message.message_id} style={message.sender_type === "client" ? styles.messageClient : styles.messageCompany}>
        <Text style={styles.text}>{message.content_kind === "file" ? `Файл: ${message.attachments[0]?.file_name ?? "вложение"}` : message.text}</Text>
        {message.attachments.map((attachment) =>
          <Button key={attachment.attachment_id} title="Скачать вложение" secondary onPress={() => void downloadAttachment(attachment.attachment_id)} />,
        )}
        <Text style={styles.muted}>{message.sender_type === "client" ? "Вы" : "Компания"} · {new Date(message.created_at).toLocaleString("ru-RU")} · {statusLabel[message.delivery_status] ?? message.delivery_status}</Text>
      </View>)}
      {!messages.isLoading && !messages.data?.items.length && <Text style={styles.muted}>Сообщений пока нет.</Text>}
    </View>
    {closed ? <View style={styles.card}>
      <Text style={styles.muted}>Диалог закрыт и доступен только для чтения.</Text>
      <Button title={creating ? "Создание…" : "Начать новый диалог"} disabled={creating} onPress={() => void createDialog()} />
      {error && <ErrorNotice error={error} retry={() => void createDialog()} />}
    </View> : <View style={styles.card}>
      <Field label="Новое сообщение" multiline value={text} onChangeText={setText} />
      <View style={styles.row}>
        <Button title={sending ? "Отправка…" : "Отправить"} disabled={sending || !text.trim()} onPress={() => void sendText()} />
        <Button title="Прикрепить изображение или PDF" secondary disabled={sending} onPress={chooseFile} />
      </View>
      {error && <ErrorNotice error={error} />}
    </View>}
  </ScrollView>;
}