import { message } from 'ant-design-vue';
import { fetchAttachmentBlob, getSessionAttachments } from '/@/views/ventAI/manageAssistent/api';
import type { SessionAttachment } from '/@/views/ventAI/manageAssistent/api';
import { isCsvFile, isDwgFile, isDxfFile, isExcelFile, isTextFile, isWordFile, getPreviewMimeType } from '/@/views/ventAI/manageAssistent/lib';
import type { AttachedFile, Message, Task } from '/@/views/ventAI/manageAssistent/types/index';

/**
 * 会话附件历史：加载后按 message_id 挂回用户消息，无法匹配的进入兜底列表；
 * 附件内容按需下载（预览时才取二进制），下载/预览都带令牌走附件下载接口。
 */

const toAttachedFile = (item: SessionAttachment): AttachedFile => ({
  id: item.file_id,
  fileId: item.file_id,
  messageId: item.message_id,
  name: item.filename,
  size: item.size_bytes,
  type: item.content_type || '',
  uploadTime: item.created_at,
  createdAt: item.created_at,
  downloadUrl: item.download_url,
});

const fileKey = (file: AttachedFile): string => file.fileId || file.id;

const mergeAttachedFiles = (existing: AttachedFile[], incoming: AttachedFile[]): AttachedFile[] => {
  const map = new Map<string, AttachedFile>();
  for (const file of [...existing, ...incoming]) {
    map.set(fileKey(file), file);
  }
  return Array.from(map.values());
};

const saveBlob = (blob: Blob, filename: string) => {
  const url = URL.createObjectURL(blob);
  const a = document.createElement('a');
  a.href = url;
  a.download = filename || '附件';
  document.body.appendChild(a);
  a.click();
  document.body.removeChild(a);
  // 让浏览器先拿到下载任务再释放对象 URL
  setTimeout(() => URL.revokeObjectURL(url), 0);
};

const hasContent = (file: AttachedFile): boolean =>
  file.content !== undefined || file.arrayBuffer !== undefined || file.preview !== undefined || !!file.originalFile;

/**
 * 预览用的 blob 换成真实类型：附件下载接口统一回 application/octet-stream（还带 Content-Disposition: attachment），
 * 浏览器凭这个类型认不出内容——PDF 放进 iframe 会被当成下载而不是显示。
 */
const withPreviewType = (file: AttachedFile, blob: Blob): Blob => {
  const type = getPreviewMimeType(file.name, file.type || blob.type);
  return type && type !== blob.type ? new Blob([blob], { type }) : blob;
};

/** 历史附件没有原始内容，首次预览时按文件类型取回并缓存到附件对象上 */
const ensureAttachmentContent = async (file: AttachedFile): Promise<AttachedFile> => {
  if (hasContent(file)) return file;
  if (!file.fileId) throw new Error('附件缺少下载标识');

  // dwg 历史附件不用把原始文件下载回来：预览面板会按 fileId 直接取后端已转换好的 svg
  //（见 DwgPreview 的 requestSvgText），下载几百 KB 只为了再上传转换一遍属于纯浪费。
  if (isDwgFile(file.name)) return file;

  const blob = await fetchAttachmentBlob(file.fileId, file.downloadUrl);
  if (isTextFile(file.name) || isCsvFile(file.name) || isDxfFile(file.name)) {
    file.content = await blob.text();
  } else if (isWordFile(file.name) || isExcelFile(file.name)) {
    file.arrayBuffer = await blob.arrayBuffer();
  } else {
    file.preview = URL.createObjectURL(withPreviewType(file, blob));
  }
  file.originalFile = new File([blob], file.name, {
    type: file.type || blob.type || 'application/octet-stream',
  });
  return file;
};

export const useChatAttachments = () => {
  /**
   * 拉取会话附件并挂到历史消息上。
   * - message_id 能匹配到用户消息：挂到该消息的 attachedFiles；
   * - message_id 为 null 或消息已合并/跳过：进入 task.orphanAttachments，由消息区底部兜底展示。
   * 附件接口失败不阻断历史消息展示（旧环境可能还没有这个接口）。
   */
  const loadHistoryAttachments = async (task: Task, sessionId: string, messages: Message[]): Promise<AttachedFile[]> => {
    try {
      const res = await getSessionAttachments(sessionId);
      const attachments = (res?.attachments || []).map(toAttachedFile);
      if (!attachments.length) {
        task.orphanAttachments = [];
        return [];
      }

      const userMessageById = new Map<number, Message>();
      for (const msg of messages) {
        if (msg.type === 'user' && msg.id != null) userMessageById.set(msg.id, msg);
      }

      const orphans: AttachedFile[] = [];
      for (const file of attachments) {
        const target = file.messageId != null ? userMessageById.get(file.messageId) : undefined;
        if (target) {
          if (!target.attachedFiles) target.attachedFiles = [];
          if (!target.attachedFiles.some((f) => fileKey(f) === fileKey(file))) {
            target.attachedFiles.push(file);
          }
        } else {
          orphans.push(file);
        }
      }

      task.orphanAttachments = orphans;
      task.attachedFiles = mergeAttachedFiles(task.attachedFiles, attachments);
      return attachments;
    } catch (e) {
      // 历史消息是主内容，附件是增强信息：失败只记录，不打断会话打开
      console.error('加载会话附件失败:', e);
      return [];
    }
  };

  const handleAttachmentPreview = async (file: AttachedFile, openPreview: (target: AttachedFile) => void) => {
    if (hasContent(file)) {
      openPreview(file);
      return;
    }
    if (!file.fileId) {
      message.warning('该附件暂不支持预览');
      return;
    }

    const closeLoading = message.loading('正在加载附件…', 0);
    try {
      await ensureAttachmentContent(file);
      openPreview(file);
    } catch (e) {
      console.error('加载附件失败:', e);
      message.error((e as Error)?.message || '附件加载失败');
    } finally {
      closeLoading();
    }
  };

  const handleAttachmentDownload = async (file: AttachedFile) => {
    try {
      if (file.fileId) {
        const closeLoading = message.loading('正在下载附件…', 0);
        try {
          const blob = await fetchAttachmentBlob(file.fileId, file.downloadUrl);
          saveBlob(blob, file.name);
        } finally {
          closeLoading();
        }
        return;
      }
      if (file.originalFile) {
        saveBlob(file.originalFile, file.name);
        return;
      }
      if (file.preview?.startsWith('blob:') || file.preview?.startsWith('data:')) {
        const blob = await (await fetch(file.preview)).blob();
        saveBlob(blob, file.name);
        return;
      }
      message.warning('该附件暂不支持下载');
    } catch (e) {
      console.error('下载附件失败:', e);
      message.error((e as Error)?.message || '附件下载失败');
    }
  };

  return { loadHistoryAttachments, handleAttachmentPreview, handleAttachmentDownload };
};