collection-abstraction/pairs

import BasePairs from './BasePairs.js';
import insert from './insert.js';
import remove from './remove.js';

export default class EfficientlyInvertiblePairs extends BasePairs {
    static from(pairs) {
        const set = new EfficientlyInvertiblePairs(new Map(), new Map(), 0);
        return set.update(pairs);
    }

    // Set-like

    constructor(map, imap, size) {
        super();
        this._map = map;
        this._imap = imap;
        this.size = size;
    }

    add([A, B]) {
        if (!this.has([A, B])) {
            insert(this._map, A, B);
            insert(this._imap, B, A);
            ++this.size;
        }

        return this;
    }

    clear() {
        this.size = 0;
        this._map.clear();
        this._imap.clear();
        return undefined;
    }

    delete([A, B]) {
        if (remove(this._map, A, B)) {
            remove(this._imap, B, A);
            --this.size;
            return true;
        }

        return false;
    }

    // Custom

    right() {
        return this._imap.keys();
    }

    *leftOf(B) {
        if (this._imap.has(B)) yield* this._imap.get(B);
    }

    invert() {
        return new EfficientlyInvertiblePairs(this._imap, this._map, this.size);
    }
}