data-structures-and-algorithms/deque

import {IndexError} from '@failure-abstraction/error';

import Deque from './Deque.js';

/**
 * SingleElementDeque.
 *
 * @param {Iterable<any>} iterable
 */
export default function SingleElementDeque(iterable) {
    this._empty = true;

    this._value = 0;

    if (iterable !== null) {
        this.extend(iterable);
    }
}

SingleElementDeque.prototype = new Deque();

SingleElementDeque.prototype.len = function () {
    return this._empty ? 0 : 1;
};

SingleElementDeque.prototype.capacity = function () {
    return 1;
};

SingleElementDeque.prototype.values = function* () {
    if (this._empty) {
        return;
    }

    yield this._value;
};

SingleElementDeque.prototype.append =
    // eslint-disable-next-line no-multi-assign
    SingleElementDeque.prototype.appendleft = function (x) {
        this._empty = false;
        this._value = x;

        return this;
    };

SingleElementDeque.prototype.clear = function () {
    this._empty = true;
    this._value = 0;

    return this;
};

SingleElementDeque.prototype.copy = function () {
    return new SingleElementDeque(this);
};

SingleElementDeque.prototype.pop =
    // eslint-disable-next-line no-multi-assign
    SingleElementDeque.prototype.popleft = function () {
        if (this._empty) {
            throw new IndexError('pop / popleft');
        }

        const value = this._value;

        this._empty = true;
        this._value = 0;

        return value;
    };

SingleElementDeque.prototype.get = function (i) {
    if (this._empty || i !== 0) {
        throw new IndexError(i);
    }

    return this._value;
};

SingleElementDeque.prototype.set = function (i, value) {
    if (this._empty || i !== 0) {
        throw new IndexError(i);
    }

    this._value = value;

    return this;
};