import { useRef, useState } from 'react';
import * as api from '../api/client';
import type { Attachment } from '../types';
import { PaperclipIcon, DownloadIcon, FileIcon, CloseIcon, SpinnerIcon } from './icons';

/** 已发出邮件的附件清单（只读，点击下载）。 */
export function AttachmentList({ items }: { items: Attachment[] }) {
  if (!items || items.length === 0) return null;

  return (
    <div className="mt-4 border-t border-gray-100 pt-3">
      <div className="flex items-center gap-1.5 mb-2">
        <PaperclipIcon className="w-3.5 h-3.5 text-gray-400" />
        <span className="text-2xs font-medium text-gray-500">
          附件 {items.length}
        </span>
      </div>
      <ul className="space-y-1">
        {items.map(a => (
          <li key={a.attachment_id}>
            <a
              href={api.attachmentURL(a.attachment_id)}
              // download 让浏览器保存而非尝试渲染；服务端也已强制 octet-stream + attachment
              download={a.filename}
              className="group flex items-center gap-2 px-2 py-1.5 rounded border border-gray-200 hover:border-blue-300 hover:bg-blue-50 transition-colors"
            >
              <FileIcon className="w-3.5 h-3.5 text-gray-400 shrink-0" />
              <span className="text-xs text-gray-800 truncate flex-1">{a.filename}</span>
              <span className="text-3xs text-gray-400 shrink-0">
                {api.formatSize(a.size_bytes)}
              </span>
              <DownloadIcon className="w-3.5 h-3.5 text-gray-300 group-hover:text-blue-500 shrink-0" />
            </a>
          </li>
        ))}
      </ul>
    </div>
  );
}

/** 待发送的附件：已上传到服务器、等着随邮件发出。 */
export interface PendingAttachment {
  id: string;
  filename: string;
  size: number;
}

/**
 * 写信时的附件选择器。
 *
 * 上传是独立一步：选中即上传，拿到 attachment_id 后暂存，发信时一并提交。
 * 之所以不等到点「发送」再传：大文件上传要时间，让用户在写正文时就完成上传体验更好，
 * 而且上传失败能立刻反馈而不是卡在发送那一刻。
 */
export function AttachmentPicker({
  items,
  onChange,
  disabled
}: {
  items: PendingAttachment[];
  onChange: (next: PendingAttachment[]) => void;
  disabled?: boolean;
}) {
  const inputRef = useRef<HTMLInputElement>(null);
  const [uploading, setUploading] = useState<{ name: string; pct: number } | null>(null);
  const [error, setError] = useState<string | null>(null);

  const pick = () => inputRef.current?.click();

  const handleFiles = async (files: FileList | null) => {
    if (!files || files.length === 0) return;
    setError(null);

    // 逐个上传而非并发：并发时进度条只能显示其中一个，且大文件同时传更容易触发体积限制
    const added: PendingAttachment[] = [];
    for (const file of Array.from(files)) {
      setUploading({ name: file.name, pct: 0 });
      try {
        const r = await api.uploadAttachment(file, pct => setUploading({ name: file.name, pct }));
        added.push({
          id: r.attachment.attachment_id,
          filename: r.attachment.filename,
          size: r.attachment.size_bytes
        });
      } catch (err) {
        setError(`${file.name}：${err instanceof Error ? err.message : String(err)}`);
        break; // 一个失败就停下，避免连续弹同类错误
      }
    }
    setUploading(null);
    if (added.length > 0) onChange([...items, ...added]);

    // 清空 input，否则重复选同一个文件不会触发 change
    if (inputRef.current) inputRef.current.value = '';
  };

  const remove = async (a: PendingAttachment) => {
    // 从服务器删掉未挂载的附件，不然它会占着磁盘等 24 小时 GC
    try {
      await api.deleteAttachment(a.id);
    } catch {
      /* 删不掉也只是留给 GC，不该阻塞用户移除操作 */
    }
    onChange(items.filter(x => x.id !== a.id));
  };

  return (
    <div className="space-y-2">
      <input
        ref={inputRef}
        type="file"
        multiple
        className="hidden"
        onChange={e => handleFiles(e.target.files)}
      />

      <div className="flex items-center gap-2 flex-wrap min-w-0">
        <button
          type="button"
          onClick={pick}
          disabled={disabled || uploading !== null}
          className="tap shrink-0 inline-flex items-center gap-1.5 text-xs px-2.5 py-1.5 border border-gray-300 rounded-md hover:bg-gray-50 disabled:opacity-40"
        >
          <PaperclipIcon className="w-3.5 h-3.5" />
          添加附件
        </button>

        {uploading && (
          <span className="min-w-0 flex-1 inline-flex items-center gap-1.5 text-2xs text-gray-500">
            <SpinnerIcon className="w-3.5 h-3.5 animate-spin shrink-0" />
            <span className="truncate">{uploading.name}</span>
            <span className="shrink-0">{uploading.pct}%</span>
          </span>
        )}

        {items.length > 0 && !uploading && (
          <span className="text-2xs text-gray-500 min-w-0 break-words">
            {items.length} 个附件 ·{' '}
            {api.formatSize(items.reduce((sum, a) => sum + a.size, 0))}
          </span>
        )}
      </div>

      {error && <div className="text-2xs text-red-600 break-words">{error}</div>}

      {items.length > 0 && (
        <ul className="space-y-1">
          {items.map(a => (
            <li
              key={a.id}
              className="flex items-center gap-2 px-2 py-1.5 rounded border border-gray-200 bg-gray-50"
            >
              <FileIcon className="w-3.5 h-3.5 text-gray-400 shrink-0" />
              <span className="text-xs text-gray-800 truncate flex-1">{a.filename}</span>
              <span className="text-3xs text-gray-400 shrink-0">{api.formatSize(a.size)}</span>
              <button
                type="button"
                onClick={() => remove(a)}
                disabled={disabled}
                title="移除"
                className="tap shrink-0 inline-flex items-center justify-center text-gray-500 hover:text-red-600 disabled:opacity-40"
              >
                <CloseIcon className="w-3.5 h-3.5" />
              </button>
            </li>
          ))}
        </ul>
      )}
    </div>
  );
}