import type { LeaderboardResponse } from './leaderboard.js';

export const leaderboardPageSize = 25;

/** Keep a viewed ranking stable until the reader chooses to apply new results. */
export function createLeaderboardUpdates(scope: string, current: LeaderboardResponse) {
    let pending: LeaderboardResponse | null = null;
    return {
        reset(nextScope: string, report: LeaderboardResponse) {
            scope = nextScope;
            current = report;
            pending = null;
        },
        receive(requestScope: string, report: LeaderboardResponse, inspecting: boolean) {
            if (requestScope !== scope) return null;
            if (JSON.stringify(current) === JSON.stringify(report)) pending = null;
            else if (inspecting || pending) pending = report;
            else current = report;
            return { current, pending };
        },
        apply() {
            if (pending) current = pending;
            pending = null;
            return current;
        }
    };
}