Cell array keyed

cell_arrayed_keyed.ts

export function cellArrayKeyed2<K,A,B>(keyEq: (a:K,b:K)=>boolean, keyExtractor: (a:A)=>K, transform: (a:A) => B, cas: sodium.Cell<A[]>): sodium.Cell<B[]> {
    return sodium.Operational
        .updates(cas)
        .accumLazy(
            cas.sampleLazy().map(as => as.map(a => T2.of(keyExtractor(a), transform(a)))),
            (nextAs: A[], lastResult: T2<K,B>[]) => {
                let nextResult: T2<K,B>[] = [];
                for (let i = 0; i < nextAs.length; ++i) {
                    let a = nextAs[i];
                    let key = keyExtractor(a);
                    let existingOp: Option<T2<K,B>> = Option.none();
                    for (let j = 0; j < lastResult.length; ++j) {
                        let r = lastResult[j];
                        if (keyEq(r._1, key)) {
                            existingOp = Option.some(r);
                            break;
                        }
                    }
                    if (existingOp.isSome) {
                        let existing = existingOp.fromSome();
                        nextResult.push(existing);
                    } else {
                        nextResult.push(T2.of(key, transform(a)));
                    }
                }
                return nextResult;
            }
        )
        .map(x => x.map(x2 => x2._2));
}