import { useState } from 'react';

import { useMutation, useQuery, useQueryClient } from '@tanstack/react-query';
import { Link } from 'react-router-dom';

import { Avatar } from '@/app/Avatar';
import { Icon } from '@/app/Icon';
import { SelectionCheckbox } from '@/app/SelectionCheckbox';
import { Toast } from '@/app/Toast';
import { fetchAllPages } from '@/lib/api/client';
import { batchUnblockUsers, getBlocks, unblockUser } from '@/lib/api/friends';
import { formatEventTimestamp } from '@/lib/messages/time';

/** README §5.6. `getBlocks` nests the user under `.user` (see friends.ts's own comment on that
 *  endpoint's real shape, a doc-drift bug caught during Phase 1-2's review).
 *
 * Multi-select + batch-unblock has no dedicated mock anywhere in this design handoff (04-contacts.dc.html's
 * own #1g only ever shows a single row, one 移出 button each) -- rather than invent a new interaction
 * pattern from nothing, this reuses the SAME 多选/已选择N项/取消 header convention FavoritesLayout.tsx
 * already established for its own multi-select, so it's consistent with something this app already does,
 * not a one-off design.
 */
export function BlocklistView() {
  const queryClient = useQueryClient();
  const [error, setError] = useState('');
  const [selectMode, setSelectMode] = useState(false);
  const [selected, setSelected] = useState<Set<string>>(new Set());
  const query = useQuery({ queryKey: ['blocks'], queryFn: () => fetchAllPages((cursor) => getBlocks(cursor)) });

  const unblockMutation = useMutation({
    mutationFn: (userId: string) => unblockUser(userId),
    onSuccess: () => queryClient.invalidateQueries({ queryKey: ['blocks'] }),
    onError: (err) => setError(err instanceof Error ? err.message : '移出黑名单失败'),
  });

  const exitSelectMode = () => {
    setSelectMode(false);
    setSelected(new Set());
  };

  const bulkUnblockMutation = useMutation({
    mutationFn: (userIds: string[]) => batchUnblockUsers(userIds),
    onSuccess: (data) => {
      queryClient.invalidateQueries({ queryKey: ['blocks'] });
      // A 200 here only means the REQUEST was accepted -- the doc's own worked example returns a
      // per-item `failed[]` array alongside `items[]`, so some of the selected users can fail to
      // unblock while the rest succeed. Silently treating this as full success (the same pattern
      // already fixed for favorites/GroupAdminModal elsewhere in this app) would leave a user still
      // on the blocklist with no indication anything went wrong.
      if (data.failed?.length) setError(`${data.failed.length} 人移出失败，请重试`);
      exitSelectMode();
    },
    onError: (err) => setError(err instanceof Error ? err.message : '批量移出失败'),
  });

  const toggleSelected = (userId: string) =>
    setSelected((prev) => {
      const next = new Set(prev);
      if (next.has(userId)) next.delete(userId);
      else next.add(userId);
      return next;
    });

  const items = query.data || [];

  return (
    <div className="flex h-full w-full flex-col overflow-y-auto bg-surface-content">
      {selectMode ? (
        <header className="flex h-15 flex-none items-center justify-between border-b border-border-panel bg-white px-6">
          <span className="text-sm text-text-secondary">
            已选择 <strong className="font-semibold text-accent">{selected.size}</strong> 项
          </span>
          <span className="flex items-center gap-2">
            <button
              type="button"
              onClick={() => bulkUnblockMutation.mutate(Array.from(selected))}
              disabled={selected.size === 0 || bulkUnblockMutation.isPending}
              className="flex h-8.5 items-center gap-1.5 whitespace-nowrap rounded-md border border-[#d5d9df] px-3.5 text-[13px] text-text-tertiary-1 disabled:opacity-40"
            >
              <Icon name="remove_circle_outline" className="text-[18px]" />
              移出
            </button>
            <button type="button" onClick={exitSelectMode} className="grid h-8.5 place-items-center px-3.5 text-[13px] text-text-tertiary-1">
              取消
            </button>
          </span>
        </header>
      ) : (
        <header className="flex h-15 flex-none items-center gap-1 border-b border-border-panel bg-white px-6">
          <Link to="/contacts" className="grid h-9.5 w-9.5 flex-none place-items-center text-text-heading md:hidden">
            <Icon name="arrow_back_ios_new" />
          </Link>
          <strong className="flex-1 text-base font-semibold text-text-heading">
            黑名单{items.length ? ` ${items.length}` : ''}
          </strong>
          {items.length > 1 ? (
            <button type="button" onClick={() => setSelectMode(true)} className="text-sm text-accent">
              多选
            </button>
          ) : null}
        </header>
      )}
      <div className="flex flex-col gap-2.5 p-6">
        {query.isLoading ? (
          <div className="py-10 text-center text-sm text-text-tertiary-4">加载中…</div>
        ) : query.isError ? (
          <div className="flex flex-col items-center gap-2 py-10 text-sm text-danger-text">
            <span>加载失败，请重试</span>
            <button type="button" onClick={() => query.refetch()} className="text-accent">
              重试
            </button>
          </div>
        ) : items.length === 0 ? (
          <div className="py-10 text-center text-sm text-text-tertiary-4">黑名单是空的</div>
        ) : (
          items.map((b) => (
            <div
              key={b.user.user_id}
              role={selectMode ? 'button' : undefined}
              tabIndex={selectMode ? 0 : undefined}
              onClick={selectMode ? () => toggleSelected(b.user.user_id) : undefined}
              onKeyDown={selectMode ? (e) => e.key === 'Enter' && toggleSelected(b.user.user_id) : undefined}
              className={`flex items-center gap-3 rounded-xl bg-white px-4 py-3 shadow-bubble ${selectMode ? 'cursor-pointer' : ''}`}
            >
              {selectMode ? <SelectionCheckbox selected={selected.has(b.user.user_id)} /> : null}
              <Avatar
                id={b.user.user_id}
                name={b.user.display_name}
                avatarFileId={b.user.avatar_file_id}
                className="h-11 w-11 flex-none rounded-lg text-base grayscale"
              />
              <span className="flex min-w-0 flex-1 flex-col gap-0.5">
                <strong className="truncate text-[15px] font-medium text-text-body">{b.user.display_name || b.user.user_id}</strong>
                <span className="truncate text-xs text-text-tertiary-2">
                  拉黑于 {formatEventTimestamp(new Date(b.blocked_at))} · 对方无法向你发送消息或发起通话
                </span>
              </span>
              {selectMode ? null : (
                <button
                  type="button"
                  onClick={() => unblockMutation.mutate(b.user.user_id)}
                  disabled={unblockMutation.isPending}
                  className="h-8 flex-none rounded-lg border border-[#d5d9df] px-3 text-xs text-text-secondary disabled:opacity-50"
                >
                  移出
                </button>
              )}
            </div>
          ))
        )}
        {items.length ? (
          <p className="m-0 mt-2 text-xs text-text-tertiary-3">移出黑名单后恢复通信权限，但不会自动恢复已删除的好友关系。</p>
        ) : null}
      </div>
      <Toast message={error} variant="error" onDone={() => setError('')} />
    </div>
  );
}