@codibre/fluent-iterable/dist/utils/get-grouping-top-hit.js

Provides LINQ-like fluent api operations for iterables and async iterables (ES2018+).

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.getGroupingTopHit = getGroupingTopHit;
const prepare_1 = require("../types-internal/prepare");
const utils_1 = require("./utils");
const noDistinct = (0, utils_1.constant)(1);
function getGroupingTopHit(distinct, choose, mapper = utils_1.identity) {
    const preparedMapper = (0, prepare_1.prepare)(mapper);
    let preparedDistinct;
    if (!choose) {
        preparedDistinct = noDistinct;
        choose = distinct;
        const chosenMap = new Map();
        return function (k, v, previous) {
            const mapped = preparedMapper(v);
            const prev = chosenMap.get(k);
            if (!prev) {
                chosenMap.set(k, [mapped, previous.length]);
                return [mapped];
            }
            const chosen = choose(prev[0], mapped);
            if (chosen !== prev[0]) {
                chosenMap.set(k, [chosen, prev[1]]);
                previous[prev[1]] = chosen;
            }
        };
    }
    preparedDistinct = (0, prepare_1.prepare)(distinct);
    const groupMap = new Map();
    return function (k, v, previous) {
        let chosenMap = groupMap.get(k);
        if (!chosenMap) {
            chosenMap = new Map();
            groupMap.set(k, chosenMap);
        }
        const mapped = preparedMapper(v);
        const chosenKey = preparedDistinct(v);
        const prev = chosenMap.get(chosenKey);
        if (!prev) {
            chosenMap.set(chosenKey, [mapped, previous.length]);
            return [mapped];
        }
        const chosen = choose(prev[0], mapped);
        if (chosen !== prev[0]) {
            chosenMap.set(chosenKey, [chosen, prev[1]]);
            previous[prev[1]] = chosen;
        }
    };
}