@tpluscode/rdfine/lib/rdf-list.js

RDF/JS idiomatic, native, effective

import namespace from '@rdfjs/namespace';
const rdf = namespace('http://www.w3.org/1999/02/22-rdf-syntax-ns#');
function isLast(node) {
    return rdf.nil.equals(node.term);
}
export function isList(node) {
    const isLastListNode = isLast(node);
    const isListNode = node.out([rdf.first, rdf.rest]).values.length === 2;
    return isLastListNode || isListNode;
}
export function enumerateList(parent, listNode, fromTerm) {
    const items = [];
    let current = listNode;
    while (!isLast(current)) {
        const firstItem = current.out(parent.env.ns.rdf.first).map((first, index) => {
            if (index > 0) {
                throw new Error('Malformed RDF List with multiple rdf:first objects');
            }
            return fromTerm.call(parent, first);
        });
        firstItem.forEach(item => {
            if (Array.isArray(item)) {
                throw new Error('Malformed RDF List had multiple rdf:first objects');
            }
            items.push(item);
        });
        current = current.out(parent.env.ns.rdf.rest).map((quad, index) => {
            if (index > 0) {
                throw new Error('Malformed RDF List with multiple rdf:rest objects');
            }
            return quad;
        })[0];
    }
    return items;
}
export function initialize(...items) {
    return items.reduceRight((prev, item) => {
        if (!prev) {
            return {
                [rdf.first.value]: item,
                [rdf.rest.value]: rdf.nil,
            };
        }
        return {
            [rdf.first.value]: item,
            [rdf.rest.value]: prev,
        };
    }, null) || rdf.nil;
}