import { useRef, useState } from "react";

import { api, session, uploadFile } from "../lib/client";
import { Download, Paperclip, Plus, Spinner, Trash } from "./icons";

export interface Attachment {
  id: string;
  item_id: string;
  filename: string;
  content_type: string;
  size: number;
  uploader_id: string;
  created_at: string;
  can_delete: boolean;
}

interface Props {
  wsId: string;
  itemId: string;
  attachments: Attachment[];
  onChange: (next: Attachment[]) => void;
  onError?: (message: string) => void;
  disabled?: boolean;
}

function humanSize(bytes: number): string {
  if (bytes < 1024) return `${bytes} B`;
  if (bytes < 1024 * 1024) return `${(bytes / 1024).toFixed(0)} KB`;
  return `${(bytes / 1024 / 1024).toFixed(1)} MB`;
}

/**
 * 条目附件（任务 / 工单 / 知识共用）。
 *
 * 下载走一次带 Authorization 头的 fetch 再转 blob：
 * 直接用 <a href> 会把令牌拼进 URL，留在浏览器历史里不值得。
 */
export function AttachmentPanel({
  wsId,
  itemId,
  attachments,
  onChange,
  onError,
  disabled = false,
}: Props) {
  const fileRef = useRef<HTMLInputElement>(null);
  const [busy, setBusy] = useState(false);
  const [dragging, setDragging] = useState(false);

  async function addFiles(files: File[]) {
    if (files.length === 0) return;
    setBusy(true);
    try {
      const created: Attachment[] = [];
      for (const file of files) {
        created.push(
          await uploadFile<Attachment>(`/workspaces/${wsId}/items/${itemId}/attachments`, file),
        );
      }
      onChange([...created, ...attachments]);
    } catch (err) {
      onError?.(err instanceof Error ? err.message : "上传失败");
    } finally {
      setBusy(false);
    }
  }

  async function download(row: Attachment) {
    try {
      const resp = await fetch(
        `/api/v1/workspaces/${wsId}/attachments/${row.id}/download`,
        { headers: { Authorization: `Bearer ${session.access ?? ""}` } },
      );
      if (!resp.ok) throw new Error(`下载失败（HTTP ${resp.status}）`);
      const blob = await resp.blob();
      const url = URL.createObjectURL(blob);
      const anchor = document.createElement("a");
      anchor.href = url;
      anchor.download = row.filename;
      anchor.click();
      URL.revokeObjectURL(url);
    } catch (err) {
      onError?.(err instanceof Error ? err.message : "下载失败");
    }
  }

  async function remove(row: Attachment) {
    if (!window.confirm(`删除附件「${row.filename}」？正文里的引用会变成坏链。`)) return;
    setBusy(true);
    try {
      // 后端要求显式确认：删除不可逆，前端这一步只是二次确认
      await api.del(`/workspaces/${wsId}/attachments/${row.id}?confirm=true`);
      onChange(attachments.filter((item) => item.id !== row.id));
    } catch (err) {
      onError?.(err instanceof Error ? err.message : "删除失败");
    } finally {
      setBusy(false);
    }
  }

  return (
    <div
      onDragOver={(event) => {
        if (event.dataTransfer.types.includes("Files")) {
          event.preventDefault();
          setDragging(true);
        }
      }}
      onDragLeave={() => setDragging(false)}
      onDrop={(event) => {
        const files = Array.from(event.dataTransfer.files ?? []);
        if (files.length > 0) {
          event.preventDefault();
          setDragging(false);
          void addFiles(files);
        }
      }}
      className={dragging ? "rounded-xl ring-2 ring-primary-500/40" : ""}
    >
      <div className="flex items-center gap-2">
        <span className="inline-flex items-center gap-1.5 text-2xs font-medium text-ink-500">
          <Paperclip size={13} />
          附件 {attachments.length > 0 && <span className="text-ink-400">· {attachments.length}</span>}
        </span>
        <button
          type="button"
          disabled={disabled || busy}
          onClick={() => fileRef.current?.click()}
          className="ml-auto inline-flex items-center gap-1 rounded-md px-1.5 py-0.5 text-2xs text-ink-500 transition hover:bg-paper-200 hover:text-ink-800 disabled:opacity-40"
        >
          {busy ? <Spinner size={12} /> : <Plus size={12} />}
          上传
        </button>
      </div>

      <input
        ref={fileRef}
        type="file"
        multiple
        className="hidden"
        onChange={(event) => {
          void addFiles(Array.from(event.target.files ?? []));
          event.target.value = "";
        }}
      />

      {attachments.length === 0 ? (
        <p className="mt-1.5 rounded-lg border border-dashed border-line-200 px-3 py-2 text-2xs text-ink-400">
          可以把文件拖到这里，或点「上传」。
        </p>
      ) : (
        <ul className="mt-1.5 space-y-1">
          {attachments.map((row) => (
            <li
              key={row.id}
              className="group flex items-center gap-2 rounded-lg px-2 py-1.5 transition hover:bg-paper-200"
            >
              <span className="min-w-0 flex-1 truncate text-xs text-ink-700">{row.filename}</span>
              <span className="shrink-0 text-2xs text-ink-400">{humanSize(row.size)}</span>
              <button
                type="button"
                onClick={() => void download(row)}
                title="下载"
                aria-label={`下载 ${row.filename}`}
                className="grid h-6 w-6 place-items-center rounded text-ink-400 opacity-0 transition hover:bg-paper-300 hover:text-ink-700 group-hover:opacity-100"
              >
                <Download size={13} />
              </button>
              {row.can_delete && !disabled && (
                <button
                  type="button"
                  onClick={() => void remove(row)}
                  title="删除"
                  aria-label={`删除 ${row.filename}`}
                  className="grid h-6 w-6 place-items-center rounded text-ink-400 opacity-0 transition hover:bg-rust-50 hover:text-rust-600 group-hover:opacity-100"
                >
                  <Trash size={13} />
                </button>
              )}
            </li>
          ))}
        </ul>
      )}
    </div>
  );
}