QOL: Move source code under the src directory. (#1318)

src/providers/decorators.ts

@@ -0,0 +1,91 @@
+export function singleton<T extends (...params: never[]) => unknown>(fn: T): T {
+  let called = false;
+
+  return ((...args) => {
+    if (called) {
+      return;
+    }
+
+    called = true;
+    return fn(...args);
+  }) as T;
+}
+
+export function debounce<T extends (...params: never[]) => unknown>(fn: T, delay: number): T {
+  let timeout: NodeJS.Timeout;
+  return ((...args) => {
+    clearTimeout(timeout);
+    timeout = setTimeout(() => fn(...args), delay);
+  }) as T;
+}
+
+export function cache<T extends (...params: P) => R, P extends never[], R>(fn: T): T {
+  let lastArgs: P;
+  let lastResult: R;
+  return ((...args: P) => {
+    if (
+      args.length !== lastArgs?.length
+      || args.some((arg, i) => arg !== lastArgs[i])
+    ) {
+      lastArgs = args;
+      lastResult = fn(...args);
+    }
+
+    return lastResult;
+  }) as T;
+}
+
+/*
+  The following are currently unused, but potentially useful in the future
+*/
+
+export function throttle<T extends (...params: unknown[]) => unknown>(fn: T, delay: number): T {
+  let timeout: NodeJS.Timeout | undefined;
+  return ((...args) => {
+    if (timeout) {
+      return;
+    }
+
+    timeout = setTimeout(() => {
+      timeout = undefined;
+      fn(...args);
+    }, delay);
+  }) as T;
+}
+
+function memoize<T extends (...params: unknown[]) => unknown>(fn: T): T {
+  const cache = new Map();
+
+  return ((...args) => {
+    const key = JSON.stringify(args);
+    if (!cache.has(key)) {
+      cache.set(key, fn(...args));
+    }
+
+    return cache.get(key) as unknown;
+  }) as T;
+}
+
+function retry<T extends (...params: unknown[]) => unknown>(fn: T, { retries = 3, delay = 1000 } = {}): T {
+  return ((...args) => {
+    try {
+      return fn(...args);
+    } catch (error) {
+      if (retries > 0) {
+        retries--;
+        setTimeout(() => retry(fn, { retries, delay })(...args), delay);
+      } else {
+        throw error;
+      }
+    }
+  }) as T;
+}
+
+export default {
+  singleton,
+  debounce,
+  cache,
+  throttle,
+  memoize,
+  retry,
+};