relay-cursor-paging/src/checkPagingSanity.js

Relay Cursor-Based Pagination Support for Sequelize

function checkPagingSanity(args) {
    var first = args.first, last = args.last, after = args.after, before = args.before;
    var isForwardPaging = !!first || !!after;
    var isBackwardPaging = !!last || !!before;
    if (isForwardPaging && isBackwardPaging) {
        throw new Error("cursor-based pagination cannot be forwards AND backwards");
    }
    if (isForwardPaging && before || isBackwardPaging && after) {
        throw new Error("paging must use either first/after or last/before");
    }
    if (isForwardPaging && first < 0 || isBackwardPaging && last < 0) {
        throw new Error("paging limit must be positive");
    }
    // This is a weird corner case. We'd have to invert the ordering of query to get the last few items then re-invert it when emitting the results.
    // We'll just ignore it for now.
    if (last && !before) {
        throw new Error("when paging backwards, a 'before' argument is required");
    }
    return { isForwardPaging: isForwardPaging, isBackwardPaging: isBackwardPaging };
}
Object.defineProperty(exports, "__esModule", { value: true });
exports.default = checkPagingSanity;