collection-abstraction/pairs

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

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

    // Set-like

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

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

        return this;
    }

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

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

        return false;
    }

    // Custom

    invert() {
        return MemoryEfficientPairs.from(invertIterable(this.values()));
    }
}