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import {InternMap} from "internmap";
import identity from "./identity.js";
export default function group(values, ...keys) {
return nest(values, identity, identity, keys);
}
export function groups(values, ...keys) {
return nest(values, Array.from, identity, keys);
}
function flatten(groups, keys) {
for (let i = 1, n = keys.length; i < n; ++i) {
groups = groups.flatMap(g => g.pop().map(([key, value]) => [...g, key, value]));
}
return groups;
}
export function flatGroup(values, ...keys) {
return flatten(groups(values, ...keys), keys);
}
export function flatRollup(values, reduce, ...keys) {
return flatten(rollups(values, reduce, ...keys), keys);
}
export function rollup(values, reduce, ...keys) {
return nest(values, identity, reduce, keys);
}
export function rollups(values, reduce, ...keys) {
return nest(values, Array.from, reduce, keys);
}
export function index(values, ...keys) {
return nest(values, identity, unique, keys);
}
export function indexes(values, ...keys) {
return nest(values, Array.from, unique, keys);
}
function unique(values) {
if (values.length !== 1) throw new Error("duplicate key");
return values[0];
}
function nest(values, map, reduce, keys) {
return (function regroup(values, i) {
if (i >= keys.length) return reduce(values);
const groups = new InternMap();
const keyof = keys[i++];
let index = -1;
for (const value of values) {
const key = keyof(value, ++index, values);
const group = groups.get(key);
if (group) group.push(value);
else groups.set(key, [value]);
}
for (const [key, values] of groups) {
groups.set(key, regroup(values, i));
}
return map(groups);
})(values, 0);
}
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