/**
 * Add a resource to a list, or replace the copy already there.
 *
 * A list fed by both a save and a broadcast can receive the same record twice, in either order: the
 * server broadcasts as it writes, so its event can land before the save's own response. Matching by id
 * keeps one copy whichever arrives first. A resource with no id cannot match anything and is appended.
 */
export const upsertById = <T extends { id?: string }>(list: T[], item: T): T[] =>
    item.id !== undefined && list.some((entry) => entry.id === item.id)
        ? list.map((entry) => (entry.id === item.id ? item : entry))
        : [...list, item];