refactoring

Resolve #7779

packages/backend/src/prelude/README.md

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+# Prelude
+このディレクトリのコードはJavaScriptの表現能力を補うためのコードです。
+Misskey固有の処理とは独立したコードの集まりですが、Misskeyのコードを読みやすくすることを目的としています。

packages/backend/src/prelude/array.ts

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+import { EndoRelation, Predicate } from './relation';
+
+/**
+ * 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 sum(xs: number[]): number {
+	return xs.reduce((a, b) => a + b, 0);
+}
+
+export function maximum(xs: number[]): number {
+	return Math.max(...xs);
+}
+
+/**
+ * Splits an array based on the equivalence relation.
+ * The concatenation of the result is equal to the argument.
+ */
+export function groupBy<T>(f: EndoRelation<T>, xs: T[]): T[][] {
+	const groups = [] as T[][];
+	for (const x of xs) {
+		if (groups.length !== 0 && f(groups[groups.length - 1][0], x)) {
+			groups[groups.length - 1].push(x);
+		} else {
+			groups.push([x]);
+		}
+	}
+	return groups;
+}
+
+/**
+ * Splits an array based on the equivalence relation induced by the function.
+ * The concatenation of the result is equal to the argument.
+ */
+export function groupOn<T, S>(f: (x: T) => S, xs: T[]): T[][] {
+	return groupBy((a, b) => f(a) === f(b), xs);
+}
+
+export function groupByX<T>(collections: T[], keySelector: (x: T) => string) {
+	return collections.reduce((obj: Record<string, T[]>, item: T) => {
+		const key = keySelector(item);
+		if (!obj.hasOwnProperty(key)) {
+			obj[key] = [];
+		}
+
+		obj[key].push(item);
+
+		return obj;
+	}, {});
+}
+
+/**
+ * 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 = [];
+	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;
+}

packages/backend/src/prelude/await-all.ts

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+type Await<T> = T extends Promise<infer U> ? U : T;
+
+type AwaitAll<T> = {
+	[P in keyof T]: Await<T[P]>;
+};
+
+export async function awaitAll<T>(obj: T): Promise<AwaitAll<T>> {
+	const target = {} as any;
+	const keys = Object.keys(obj);
+	const values = Object.values(obj);
+
+	const resolvedValues = await Promise.all(values.map(value =>
+		(!value || !value.constructor || value.constructor.name !== 'Object')
+			? value
+			: awaitAll(value)
+	));
+
+	for (let i = 0; i < keys.length; i++) {
+		target[keys[i]] = resolvedValues[i];
+	}
+
+	return target;
+}

packages/backend/src/prelude/math.ts

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+export function gcd(a: number, b: number): number {
+	return b === 0 ? a : gcd(b, a % b);
+}

packages/backend/src/prelude/maybe.ts

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+export interface IMaybe<T> {
+	isJust(): this is IJust<T>;
+}
+
+export interface IJust<T> extends IMaybe<T> {
+	get(): T;
+}
+
+export function just<T>(value: T): IJust<T> {
+	return {
+		isJust: () => true,
+		get: () => value
+	};
+}
+
+export function nothing<T>(): IMaybe<T> {
+	return {
+		isJust: () => false,
+	};
+}

packages/backend/src/prelude/relation.ts

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+export type Predicate<T> = (a: T) => boolean;
+
+export type Relation<T, U> = (a: T, b: U) => boolean;
+
+export type EndoRelation<T> = Relation<T, T>;

packages/backend/src/prelude/string.ts

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+export function concat(xs: string[]): string {
+	return xs.join('');
+}
+
+export function capitalize(s: string): string {
+	return toUpperCase(s.charAt(0)) + toLowerCase(s.slice(1));
+}
+
+export function toUpperCase(s: string): string {
+	return s.toUpperCase();
+}
+
+export function toLowerCase(s: string): string {
+	return s.toLowerCase();
+}

packages/backend/src/prelude/symbol.ts

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+export const fallback = Symbol('fallback');

packages/backend/src/prelude/time.ts

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+const dateTimeIntervals = {
+	'day': 86400000,
+	'hour': 3600000,
+	'ms': 1,
+};
+
+export function dateUTC(time: number[]): Date {
+	const d = time.length === 2 ? Date.UTC(time[0], time[1])
+					: time.length === 3 ? Date.UTC(time[0], time[1], time[2])
+					: time.length === 4 ? Date.UTC(time[0], time[1], time[2], time[3])
+					: time.length === 5 ? Date.UTC(time[0], time[1], time[2], time[3], time[4])
+					: time.length === 6 ? Date.UTC(time[0], time[1], time[2], time[3], time[4], time[5])
+					: time.length === 7 ? Date.UTC(time[0], time[1], time[2], time[3], time[4], time[5], time[6])
+					: null;
+
+	if (!d) throw 'wrong number of arguments';
+
+	return new Date(d);
+}
+
+export function isTimeSame(a: Date, b: Date): boolean {
+	return a.getTime() === b.getTime();
+}
+
+export function isTimeBefore(a: Date, b: Date): boolean {
+	return (a.getTime() - b.getTime()) < 0;
+}
+
+export function isTimeAfter(a: Date, b: Date): boolean {
+	return (a.getTime() - b.getTime()) > 0;
+}
+
+export function addTime(x: Date, value: number, span: keyof typeof dateTimeIntervals = 'ms'): Date {
+	return new Date(x.getTime() + (value * dateTimeIntervals[span]));
+}
+
+export function subtractTime(x: Date, value: number, span: keyof typeof dateTimeIntervals = 'ms'): Date {
+	return new Date(x.getTime() - (value * dateTimeIntervals[span]));
+}

packages/backend/src/prelude/url.ts

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+export function query(obj: {}): string {
+	const params = Object.entries(obj)
+		.filter(([, v]) => Array.isArray(v) ? v.length : v !== undefined)
+		.reduce((a, [k, v]) => (a[k] = v, a), {} as Record<string, any>);
+
+	return Object.entries(params)
+		.map((e) => `${e[0]}=${encodeURIComponent(e[1])}`)
+		.join('&');
+}
+
+export function appendQuery(url: string, query: string): string {
+	return `${url}${/\?/.test(url) ? url.endsWith('?') ? '' : '&' : '?'}${query}`;
+}

packages/backend/src/prelude/xml.ts

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+const map: Record<string, string> = {
+	'&': '&amp;',
+	'<': '&lt;',
+	'>': '&gt;',
+	'"': '&quot;',
+	'\'': '&apos;'
+};
+
+const beginingOfCDATA = '<![CDATA[';
+const endOfCDATA = ']]>';
+
+export function escapeValue(x: string): string {
+	let insideOfCDATA = false;
+	let builder = '';
+	for (
+		let i = 0;
+		i < x.length;
+	) {
+		if (insideOfCDATA) {
+			if (x.slice(i, i + beginingOfCDATA.length) === beginingOfCDATA) {
+				insideOfCDATA = true;
+				i += beginingOfCDATA.length;
+			} else {
+				builder += x[i++];
+			}
+		} else {
+			if (x.slice(i, i + endOfCDATA.length) === endOfCDATA) {
+				insideOfCDATA = false;
+				i += endOfCDATA.length;
+			} else {
+				const b = x[i++];
+				builder += map[b] || b;
+			}
+		}
+	}
+	return builder;
+}
+
+export function escapeAttribute(x: string): string {
+	return Object.entries(map).reduce((a, [k, v]) => a.replace(k, v), x);
+}