backend v4 half

SerpentRace_Backend/node_modules/libphonenumber-js/source/findNumbers/LRUCache.js

@@ -0,0 +1,107 @@
+// https://medium.com/dsinjs/implementing-lru-cache-in-javascript-94ba6755cda9
+
+class Node {
+  constructor(key, value, next = null, prev = null) {
+    this.key = key;
+    this.value = value;
+    this.next = next;
+    this.prev = prev;
+  }
+}
+
+export default class LRUCache {
+  //set default limit of 10 if limit is not passed.
+  constructor(limit = 10) {
+    this.size = 0;
+    this.limit = limit;
+    this.head = null;
+    this.tail = null;
+    this.cache = {};
+  }
+
+  // Write Node to head of LinkedList
+  // update cache with Node key and Node reference
+  put(key, value){
+    this.ensureLimit();
+
+    if(!this.head){
+      this.head = this.tail = new Node(key, value);
+    }else{
+      const node = new Node(key, value, this.head);
+      this.head.prev = node;
+      this.head = node;
+    }
+
+    //Update the cache map
+    this.cache[key] = this.head;
+    this.size++;
+  }
+
+  // Read from cache map and make that node as new Head of LinkedList
+  get(key){
+    if(this.cache[key]){
+      const value = this.cache[key].value;
+
+      // node removed from it's position and cache
+      this.remove(key)
+      // write node again to the head of LinkedList to make it most recently used
+      this.put(key, value);
+
+      return value;
+    }
+
+    console.log(`Item not available in cache for key ${key}`);
+  }
+
+  ensureLimit(){
+    if(this.size === this.limit){
+      this.remove(this.tail.key)
+    }
+  }
+
+  remove(key){
+    const node = this.cache[key];
+
+    if(node.prev !== null){
+      node.prev.next = node.next;
+    }else{
+      this.head = node.next;
+    }
+
+    if(node.next !== null){
+      node.next.prev = node.prev;
+    }else{
+      this.tail = node.prev
+    }
+
+    delete this.cache[key];
+    this.size--;
+  }
+
+  clear() {
+    this.head = null;
+    this.tail = null;
+    this.size = 0;
+    this.cache = {};
+  }
+
+  // // Invokes the callback function with every node of the chain and the index of the node.
+  // forEach(fn) {
+  //   let node = this.head;
+  //   let counter = 0;
+  //   while (node) {
+  //     fn(node, counter);
+  //     node = node.next;
+  //     counter++;
+  //   }
+  // }
+
+  // // To iterate over LRU with a 'for...of' loop
+  // *[Symbol.iterator]() {
+  //   let node = this.head;
+  //   while (node) {
+  //     yield node;
+  //     node = node.next;
+  //   }
+  // }
+}