69 lines
1.8 KiB
TypeScript
69 lines
1.8 KiB
TypeScript
// Copyright 2023 Signal Messenger, LLC
|
|
// SPDX-License-Identifier: AGPL-3.0-only
|
|
|
|
/**
|
|
* Accepts an array and a predicate function. Returns an array of arrays, where
|
|
* each time the predicate returns false, a new sub-array is started.
|
|
*
|
|
* Useful for grouping sequential items in an array.
|
|
*
|
|
* @example
|
|
* ```ts
|
|
* groupWhile([1, 2, 3, 4, 5, 6], (item, prev) => {
|
|
* return prev + 1 === item
|
|
* })
|
|
* // => [[1, 2, 3], [4, 5, 6]]
|
|
* ```
|
|
*/
|
|
export function groupWhile<T>(
|
|
array: ReadonlyArray<T>,
|
|
iteratee: (item: T, prev: T) => boolean
|
|
): Array<Array<T>> {
|
|
const groups: Array<Array<T>> = [];
|
|
let cursor = 0;
|
|
while (cursor < array.length) {
|
|
const group: Array<T> = [];
|
|
do {
|
|
// eslint-disable-next-line @typescript-eslint/no-non-null-assertion
|
|
group.push(array[cursor]!);
|
|
cursor += 1;
|
|
// eslint-disable-next-line @typescript-eslint/no-non-null-assertion
|
|
if (!iteratee(array[cursor]!, array[cursor - 1]!)) {
|
|
break;
|
|
}
|
|
} while (cursor < array.length);
|
|
groups.push(group);
|
|
}
|
|
return groups;
|
|
}
|
|
|
|
/**
|
|
* @example
|
|
* ```ts
|
|
* let result = [[1, 2], [4, 5], [7], [9, 10]]
|
|
* let formatted = formatGroups(result, "-", ", ", String)
|
|
* // => "1-2, 4-5, 7, 9-10"
|
|
* ```
|
|
*/
|
|
export function formatGroups<T>(
|
|
groups: Array<Array<T>>,
|
|
rangeSeparator: string,
|
|
groupSeparator: string,
|
|
formatItem: (value: T) => string
|
|
): string {
|
|
return groups
|
|
.map(group => {
|
|
if (group.length === 0) {
|
|
return '';
|
|
}
|
|
// eslint-disable-next-line @typescript-eslint/no-non-null-assertion
|
|
const start = formatItem(group.at(0)!);
|
|
if (group.length === 1) {
|
|
return start;
|
|
}
|
|
// eslint-disable-next-line @typescript-eslint/no-non-null-assertion
|
|
const end = formatItem(group.at(-1)!);
|
|
return `${start}${rangeSeparator}${end}`;
|
|
})
|
|
.join(groupSeparator);
|
|
}
|