refactor(frontend): scripts -> utility

packages/frontend/src/utility/array.ts

@@ -0,0 +1,118 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+type EndoRelation<T> = (a: T, b: T) => boolean;
+type Predicate<T> = (x: T) => boolean;
+
+/**
+ * Count the number of elements that satisfy the predicate
+ */
+
+export function countIf<T>(f: Predicate<T>, xs: T[]): number {
+	return xs.filter(f).length;
+}
+
+/**
+ * Count the number of elements that is equal to the element
+ */
+export function count<T>(a: T, xs: T[]): number {
+	return countIf(x => x === a, xs);
+}
+
+/**
+ * Concatenate an array of arrays
+ */
+export function concat<T>(xss: T[][]): T[] {
+	return ([] as T[]).concat(...xss);
+}
+
+/**
+ * Intersperse the element between the elements of the array
+ * @param sep The element to be interspersed
+ */
+export function intersperse<T>(sep: T, xs: T[]): T[] {
+	return concat(xs.map(x => [sep, x])).slice(1);
+}
+
+/**
+ * Returns the array of elements that is not equal to the element
+ */
+export function erase<T>(a: T, xs: T[]): T[] {
+	return xs.filter(x => x !== a);
+}
+
+/**
+ * Finds the array of all elements in the first array not contained in the second array.
+ * The order of result values are determined by the first array.
+ */
+export function difference<T>(xs: T[], ys: T[]): T[] {
+	return xs.filter(x => !ys.includes(x));
+}
+
+/**
+ * Remove all but the first element from every group of equivalent elements
+ */
+export function unique<T>(xs: T[]): T[] {
+	return [...new Set(xs)];
+}
+
+export function uniqueBy<TValue, TKey>(values: TValue[], keySelector: (value: TValue) => TKey): TValue[] {
+	const map = new Map<TKey, TValue>();
+
+	for (const value of values) {
+		const key = keySelector(value);
+		if (!map.has(key)) map.set(key, value);
+	}
+
+	return [...map.values()];
+}
+
+export function sum(xs: number[]): number {
+	return xs.reduce((a, b) => a + b, 0);
+}
+
+export function maximum(xs: number[]): number {
+	return Math.max(...xs);
+}
+
+/**
+ * Compare two arrays by lexicographical order
+ */
+export function lessThan(xs: number[], ys: number[]): boolean {
+	for (let i = 0; i < Math.min(xs.length, ys.length); i++) {
+		if (xs[i] < ys[i]) return true;
+		if (xs[i] > ys[i]) return false;
+	}
+	return xs.length < ys.length;
+}
+
+/**
+ * Returns the longest prefix of elements that satisfy the predicate
+ */
+export function takeWhile<T>(f: Predicate<T>, xs: T[]): T[] {
+	const ys: T[] = [];
+	for (const x of xs) {
+		if (f(x)) {
+			ys.push(x);
+		} else {
+			break;
+		}
+	}
+	return ys;
+}
+
+export function cumulativeSum(xs: number[]): number[] {
+	const ys = Array.from(xs); // deep copy
+	for (let i = 1; i < ys.length; i++) ys[i] += ys[i - 1];
+	return ys;
+}
+
+export function toArray<T>(x: T | T[] | undefined): T[] {
+	return Array.isArray(x) ? x : x != null ? [x] : [];
+}
+
+export function toSingle<T>(x: T | T[] | undefined): T | undefined {
+	return Array.isArray(x) ? x[0] : x;
+}