Vencord/src/utils/lazy.ts
2023-07-06 00:54:49 +02:00

94 lines
3 KiB
TypeScript

/*
* Vencord, a modification for Discord's desktop app
* Copyright (c) 2022 Vendicated and contributors
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
export function makeLazy<T>(factory: () => T): () => T {
let cache: T;
return () => cache ?? (cache = factory());
}
// Proxies demand that these properties be unmodified, so proxyLazy
// will always return the function default for them.
const unconfigurable = ["arguments", "caller", "prototype"];
const handler: ProxyHandler<any> = {};
const kGET = Symbol.for("vencord.lazy.get");
const kCACHE = Symbol.for("vencord.lazy.cached");
for (const method of [
"apply",
"construct",
"defineProperty",
"deleteProperty",
"get",
"getOwnPropertyDescriptor",
"getPrototypeOf",
"has",
"isExtensible",
"ownKeys",
"preventExtensions",
"set",
"setPrototypeOf"
]) {
handler[method] =
(target: any, ...args: any[]) => Reflect[method](target[kGET](), ...args);
}
handler.ownKeys = target => {
const v = target[kGET]();
const keys = Reflect.ownKeys(v);
for (const key of unconfigurable) {
if (!keys.includes(key)) keys.push(key);
}
return keys;
};
handler.getOwnPropertyDescriptor = (target, p) => {
if (typeof p === "string" && unconfigurable.includes(p))
return Reflect.getOwnPropertyDescriptor(target, p);
const descriptor = Reflect.getOwnPropertyDescriptor(target[kGET](), p);
if (descriptor) Object.defineProperty(target, p, descriptor);
return descriptor;
};
/**
* Wraps the result of {@see makeLazy} in a Proxy you can consume as if it wasn't lazy.
* On first property access, the lazy is evaluated
* @param factory lazy factory
* @param attempts how many times to try to evaluate the lazy before giving up
* @returns Proxy
*
* Note that the example below exists already as an api, see {@link findByPropsLazy}
* @example const mod = proxyLazy(() => findByProps("blah")); console.log(mod.blah);
*/
export function proxyLazy<T>(factory: () => T, attempts = 5): T {
let tries = 0;
const proxyDummy = Object.assign(function () { }, {
[kCACHE]: void 0 as T | undefined,
[kGET]() {
if (!proxyDummy[kCACHE] && attempts > tries++) {
proxyDummy[kCACHE] = factory();
}
return proxyDummy[kCACHE];
}
});
return new Proxy(proxyDummy, handler) as any;
}