async function http(method, path, body, opts = {}) {
    const res = await fetch(path, {
        method,
        credentials: 'same-origin',
        headers: body ? { 'Content-Type': 'application/json' } : {},
        body: body ? JSON.stringify(body) : undefined,
        signal: opts.signal
    });
    if (res.status === 204) return null;
    const ct = res.headers.get('content-type') || '';
    const data = ct.includes('json') ? await res.json() : await res.text();
    if (!res.ok) throw Object.assign(new Error(data?.error || res.statusText), { status: res.status, data });
    return data;
}

// Returns true for AbortError thrown by `fetch(... { signal })` so callers can
// silently ignore cancelled requests instead of surfacing them as errors.
export function isAbort(err) {
    return err && (err.name === 'AbortError' || err.code === 20);
}

export const api = {
    get: (p, opts) => http('GET', p, null, opts),
    post: (p, b, opts) => http('POST', p, b, opts),
    put: (p, b, opts) => http('PUT', p, b, opts),
    patch: (p, b, opts) => http('PATCH', p, b, opts),
    del: (p, opts) => http('DELETE', p, null, opts)
};