collection-abstraction/counter

import {nlargest} from '@data-structure/heapq';
import {NotImplementedError} from '@failure-abstraction/error';

import counts from './counts.js';

export default function BaseCounter(Map, Dict) {
    const Counter = function (iterable) {
        this.container = new Map();

        if (iterable !== null) this.update(iterable);
    };

    Counter.prototype = new Dict();

    // eslint-disable-next-line no-unused-vars
    Counter.fromkeys = function (seq, value = null) {
        throw new NotImplementedError(
            'Counter.fromkeys() is undefined.  Use Counter(iterable) instead.',
        );
    };

    Counter.prototype.get = function (key) {
        if (this.has(key)) return this.container.get(key);

        return 0;
    };

    Counter.prototype.elements = function* () {
        for (let [key, count] of this) {
            while (count-- > 0) yield key;
        }
    };

    Counter.prototype.increment = function (key, amount = 1) {
        this.set(key, this.get(key) + amount);
    };

    Counter.prototype.decrement = function (key, amount = 1) {
        this.increment(key, -amount);
    };

    Counter.prototype.update = function (iterable) {
        for (const key of iterable) this.increment(key);
    };

    Counter.prototype.add = function (other) {
        for (const [key, count] of other) this.increment(key, count);
    };

    Counter.prototype.subtract = function (other) {
        for (const [key, count] of other) this.decrement(key, count);
    };

    Counter.prototype.most_common = function (n = this.len()) {
        return nlargest(counts, n, this);
    };

    return Counter;
}