Put everything in src directories

packages/lib/src/LRUCache.ts

@@ -0,0 +1,69 @@
+export class LRUCache<T, U> {
+  map = new Map<T, U>()
+  keys: T[] = []
+
+  constructor(readonly maxSize: number = Infinity) {}
+
+  has(k: T) {
+    return this.map.has(k)
+  }
+
+  get(k: T) {
+    const v = this.map.get(k)
+
+    if (v !== undefined) {
+      this.keys.push(k as T)
+
+      if (this.keys.length > this.maxSize * 2) {
+        this.keys.splice(-this.maxSize)
+      }
+    }
+
+    return v
+  }
+
+  set(k: T, v: U) {
+    this.map.set(k, v)
+    this.keys.push(k)
+
+    if (this.map.size > this.maxSize) {
+      this.map.delete(this.keys.shift() as T)
+    }
+  }
+}
+
+export function cached<T, V, Args extends any[]>({
+  maxSize,
+  getKey,
+  getValue,
+}: {
+  maxSize: number
+  getKey: (args: Args) => T
+  getValue: (args: Args) => V
+}) {
+  const cache = new LRUCache<T, V>(maxSize)
+
+  const get = (...args: Args) => {
+    const k = getKey(args)
+
+    let v = cache.get(k)
+
+    if (!v) {
+      v = getValue(args)
+
+      cache.set(k, v)
+    }
+
+    return v
+  }
+
+  get.cache = cache
+  get.getKey = getKey
+  get.getValue = getValue
+
+  return get
+}
+
+export function simpleCache<V, Args extends any[]>(getValue: (args: Args) => V) {
+  return cached({maxSize: 10**10, getKey: xs => xs.join(':'), getValue})
+}