// TODO: remove this, Set is already insertion-ordered in javascript!
/** an insertion ordered set */
export default class IOSet<T> {
    // NOTE: this data structure could be improved to have O(1)
    //       deletion time if `list` is swapped out with a linked
    //       list instead of an array.
    map: Map<T, number>;
    list: T[];

    constructor(values?: Iterable<T>) {
        this.map = new Map();
        this.list = [];

        if (values !== undefined) this.extend(values);
    }

    has(v: T) {
        return this.map.has(v);
    }

    add(v: T) {
        if (!this.map.has(v)) {
            this.map.set(v, this.list.length);
            this.list.push(v);
        }
    }

    delete(v: T) {
        const idx = this.map.get(v);
        if (idx === undefined) return false;
        this.map.delete(v);
        this.list.splice(idx, 1);
        return true;
    }

    extend(values: Iterable<T>) {
        for (const v of values) {
            this.add(v);
        }
    }

    shift() {
        const v = this.list[0]!;
        // NOTE: performance could be boosted since no need for this.map.get(v) and if
        this.delete(v);
        return v;
    }

    pop() {
        const v = this.list[this.list.length - 1]!;
        // NOTE: performance could be boosted since no need for this.map.get(v) and if
        this.delete(v);
        return v;
    }

    get size() {
        return this.list.length;
    }

    [Symbol.iterator]() {
        return this.list[Symbol.iterator]();
    }
}