import { useCallback, useEffect, useRef, useState } from 'react';
import { useQuery } from '@tanstack/react-query';
import { useTranslation } from 'react-i18next';

import { fileContentUrl, uploadChannelFile, type UploadedFile } from '@/api/files';
import { fetchMeta, metaQueryKey } from '@/api/meta';
import { MESSAGE_MAX_LENGTH, retryAfterMs, type Message } from '@/api/messages';
import type { Channel } from '@/api/types';
import type { AuthorDirectory } from '@/components/chat/useAuthorDirectory';
import { ErrorNotice } from '@/components/ui/ErrorNotice';
import { formatBytes, errorCode } from '@/lib/format';
import { useMessagesStore } from '@/stores/messages';

interface ComposerProps {
  channel: Channel;
  authors: AuthorDirectory;
  /** Личная беседа: подписи без «#» (имя собеседника вместо комнаты). */
  direct?: boolean;
  /** Сообщение, на которое отвечаем (плашка над полем ввода). */
  replyTo: Message | null;
  onCancelReply: () => void;
  /** Причина, по которой отправка запрещена (нет прав, комната только для чтения). */
  disabledReason: string | null;
  canAttach: boolean;
}

/** Максимальная высота автовысоты textarea (~8 строк). */
const MAX_TEXTAREA_HEIGHT_PX = 176;
const LINE_HEIGHT_PX = 22;

/**
 * Композер сообщения: автовысота, Enter/Shift+Enter, счётчик символов,
 * вложения (скрепка и drag&drop), плашка ответа и обработка ошибок отправки
 * (лимит частоты 429 с таймером, отсутствие прав).
 */
export function Composer({
  channel,
  authors,
  direct = false,
  replyTo,
  onCancelReply,
  disabledReason,
  canAttach,
}: ComposerProps) {
  const { t, i18n } = useTranslation();
  const [value, setValue] = useState('');
  const [files, setFiles] = useState<UploadedFile[]>([]);
  const [uploading, setUploading] = useState(false);
  const [uploadError, setUploadError] = useState<unknown>(null);
  const [notice, setNotice] = useState<string | null>(null);
  const [sendError, setSendError] = useState<unknown>(null);
  const [sending, setSending] = useState(false);
  const [denied, setDenied] = useState<string | null>(null);
  const [retryAt, setRetryAt] = useState<number | null>(null);
  /** Тикающее «сейчас»: по нему считается остаток лимита частоты. */
  const [now, setNow] = useState(() => Date.now());
  const [dragging, setDragging] = useState(false);

  const textareaRef = useRef<HTMLTextAreaElement | null>(null);
  const fileInputRef = useRef<HTMLInputElement | null>(null);

  // Предельный размер файла знает сервер (`GET /meta`); если он неизвестен,
  // ограничение проверяет сам сервер, а мы показываем его ошибку.
  const meta = useQuery({
    queryKey: metaQueryKey,
    queryFn: ({ signal }) => fetchMeta(signal),
    staleTime: 300_000,
    retry: 0,
  });
  const maxUploadSize = meta.data?.max_upload_size;

  // Автовысота: от одной строки до ~8.
  useEffect(() => {
    const element = textareaRef.current;
    if (element === null) {
      return;
    }
    element.style.height = 'auto';
    const max = Math.min(MAX_TEXTAREA_HEIGHT_PX, LINE_HEIGHT_PX * 8);
    element.style.height = `${String(Math.min(element.scrollHeight, max))}px`;
  }, [value]);

  // Таймер лимита частоты: пока он идёт, отправка заблокирована.
  // Когда пауза истекла, снимаем `retryAt` — иначе интервал тикал бы вечно.
  useEffect(() => {
    if (retryAt === null) {
      return;
    }
    const tick = (): void => {
      const current = Date.now();
      setNow(current);
      if (current >= retryAt) {
        setRetryAt(null);
      }
    };
    const timer = window.setInterval(tick, 500);
    return () => {
      window.clearInterval(timer);
    };
  }, [retryAt]);
  const secondsLeft = retryAt === null ? 0 : Math.max(0, Math.ceil((retryAt - now) / 1000));

  const blockedReason = disabledReason ?? denied;
  const rateLimited = secondsLeft > 0;
  const canSubmit =
    blockedReason === null &&
    !rateLimited &&
    !sending &&
    !uploading &&
    (value.trim() !== '' || files.length > 0);

  const uploadFiles = useCallback(
    async (incoming: File[]) => {
      if (!canAttach || incoming.length === 0) {
        return;
      }
      setUploadError(null);
      setNotice(null);
      const tooLarge =
        maxUploadSize === undefined
          ? undefined
          : incoming.find((file) => file.size > maxUploadSize);
      if (tooLarge !== undefined) {
        setNotice(
          t('chat.composer.tooLarge', {
            name: tooLarge.name,
            limit: formatBytes(maxUploadSize ?? 0, i18n.language),
          }),
        );
        return;
      }
      setUploading(true);
      try {
        const uploaded: UploadedFile[] = [];
        for (const file of incoming) {
          uploaded.push(await uploadChannelFile(channel.id, file));
        }
        setFiles((current) => [...current, ...uploaded]);
      } catch (error) {
        setUploadError(error);
      } finally {
        setUploading(false);
      }
    },
    [canAttach, channel.id, i18n.language, maxUploadSize, t],
  );

  const submit = async (): Promise<void> => {
    const content = value.trim();
    if (!canSubmit || (content === '' && files.length === 0)) {
      return;
    }
    setSending(true);
    setSendError(null);
    try {
      await useMessagesStore.getState().send({
        channelId: channel.id,
        content,
        ...(replyTo === null ? {} : { replyToId: replyTo.id }),
        ...(files.length === 0 ? {} : { files }),
      });
      setValue('');
      setFiles([]);
      setNotice(null);
      // Отправка прошла — лимит частоты больше не держим.
      setRetryAt(null);
      onCancelReply();
    } catch (error) {
      // Текст и вложения остаются в композере — пользователь может повторить.
      setSendError(error);
      const code = errorCode(error);
      if (code === 'perm.denied') {
        setDenied(t('chat.composer.denied'));
      }
      const retry = retryAfterMs(error);
      if (retry !== null) {
        setNow(Date.now());
        setRetryAt(Date.now() + retry);
      }
    } finally {
      setSending(false);
    }
  };

  const counter = value.length;
  const nearLimit = counter >= MESSAGE_MAX_LENGTH - 200;

  return (
    <div
      className="border-t border-border/40 px-3 pb-3 pt-2"
      data-testid="composer"
      onDragOver={(event) => {
        if (!canAttach) {
          return;
        }
        event.preventDefault();
        setDragging(true);
      }}
      onDragLeave={() => setDragging(false)}
      onDrop={(event) => {
        if (!canAttach) {
          return;
        }
        event.preventDefault();
        setDragging(false);
        void uploadFiles([...event.dataTransfer.files]);
      }}
    >
      {replyTo === null ? null : (
        <div className="mb-2 flex items-center justify-between gap-2 rounded-[var(--radius-md)] border border-border/60 bg-surface-2 px-2 py-1 text-xs text-fg-muted">
          <span className="truncate">
            {t('chat.reply.composer', { name: authors.resolve(replyTo.author_id).name })}
          </span>
          <button
            type="button"
            aria-label={t('chat.reply.cancel')}
            className="rounded-[var(--radius-sm)] px-1 text-sm leading-none text-fg-muted hover:text-fg"
            onClick={onCancelReply}
          >
            ×
          </button>
        </div>
      )}

      {files.length === 0 ? null : (
        <ul className="mb-2 flex flex-wrap gap-2" aria-label={t('chat.composer.attachments')}>
          {files.map((file) => {
            const url = fileContentUrl(file.file_id);
            const isImage = file.content_type.startsWith('image/');
            return (
              <li
                key={file.file_id}
                className="flex items-center gap-2 rounded-[var(--radius-md)] border border-border/60 bg-surface-2 px-2 py-1 text-xs"
              >
                {isImage ? (
                  <img src={url} alt="" className="h-8 w-8 rounded object-cover" />
                ) : (
                  <span aria-hidden="true">📎</span>
                )}
                <span className="max-w-40 truncate">{file.filename}</span>
                <span className="text-fg-muted">
                  {formatBytes(file.size_bytes ?? 0, i18n.language)}
                </span>
                <button
                  type="button"
                  aria-label={t('chat.composer.removeAttachment', { name: file.filename })}
                  className="rounded-[var(--radius-sm)] px-1 leading-none text-fg-muted hover:text-danger"
                  onClick={() => {
                    setFiles((current) => current.filter((item) => item.file_id !== file.file_id));
                  }}
                >
                  ×
                </button>
              </li>
            );
          })}
        </ul>
      )}

      {notice === null ? null : (
        <p role="status" className="mb-1 text-xs text-warning">
          {notice}
        </p>
      )}

      <div
        className={`flex items-end gap-2 rounded-[var(--radius-md)] border bg-surface-2 px-2 py-1 ${
          dragging ? 'border-accent' : 'border-border/60'
        }`}
      >
        <button
          type="button"
          aria-label={t('chat.composer.attach')}
          title={t('chat.composer.attach')}
          disabled={!canAttach || uploading || blockedReason !== null}
          className="rounded-[var(--radius-sm)] px-1 pb-1 text-lg leading-none text-fg-muted transition-colors duration-[var(--duration-fast)] hover:text-fg disabled:cursor-not-allowed disabled:opacity-40"
          onClick={() => fileInputRef.current?.click()}
        >
          📎
        </button>
        <input
          ref={fileInputRef}
          type="file"
          multiple
          hidden
          aria-label={t('chat.composer.fileInput')}
          onChange={(event) => {
            const list = event.target.files;
            if (list !== null) {
              void uploadFiles([...list]);
            }
            event.target.value = '';
          }}
        />
        <textarea
          ref={textareaRef}
          aria-label={t(direct ? 'chat.composer.directLabel' : 'chat.composer.label', {
            name: channel.name,
          })}
          placeholder={t(direct ? 'chat.composer.directPlaceholder' : 'chat.composer.placeholder', {
            name: channel.name,
          })}
          className="max-h-44 min-h-[1.75rem] w-full resize-none bg-transparent py-1 text-sm text-fg placeholder:text-fg-muted/70 focus:outline-none disabled:opacity-60"
          rows={1}
          value={value}
          maxLength={MESSAGE_MAX_LENGTH}
          disabled={blockedReason !== null}
          onChange={(event) => {
            setValue(event.target.value);
            useMessagesStore.getState().notifyTyping(channel.id);
          }}
          onKeyDown={(event) => {
            if (event.key === 'Enter' && !event.shiftKey) {
              event.preventDefault();
              void submit();
            }
            if (event.key === 'Escape' && replyTo !== null) {
              onCancelReply();
            }
          }}
        />
        <button
          type="button"
          aria-label={t('chat.composer.send')}
          title={t('chat.composer.send')}
          disabled={!canSubmit || rateLimited}
          className="rounded-[var(--radius-sm)] px-2 pb-1 text-lg leading-none text-accent transition-transform duration-[var(--duration-fast)] hover:opacity-90 active:scale-95 disabled:cursor-not-allowed disabled:opacity-40"
          onClick={() => void submit()}
        >
          ➤
        </button>
      </div>

      <div className="mt-1 flex items-center justify-between gap-2 text-xs text-fg-muted">
        <span>
          {blockedReason === null
            ? uploading
              ? t('chat.composer.uploading')
              : t('chat.composer.hint')
            : blockedReason}
        </span>
        <span className={nearLimit ? 'text-warning' : undefined}>
          {t('chat.composer.counter', { count: counter, max: MESSAGE_MAX_LENGTH })}
        </span>
      </div>

      {rateLimited ? (
        <p role="alert" className="mt-1 text-xs text-warning">
          {t('chat.composer.rateLimited', { seconds: secondsLeft })}
        </p>
      ) : null}
      {uploadError === null ? null : <ErrorNotice className="mt-1" error={uploadError} />}
      {sendError === null ? null : <ErrorNotice className="mt-1" error={sendError} />}
    </div>
  );
}