From d792c6764a0e4638b1ca0a7da25a9326cc44a9c9 Mon Sep 17 00:00:00 2001
From: Gus Caplan <me@gus.host>
Date: Sat, 26 Aug 2017 05:48:31 -0700
Subject: [PATCH] ChannelStore LRU (#1832)

---
 src/stores/ChannelStore.js | 39 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/src/stores/ChannelStore.js b/src/stores/ChannelStore.js
index cffa642bb..657af240a 100644
--- a/src/stores/ChannelStore.js
+++ b/src/stores/ChannelStore.js
@@ -3,12 +3,51 @@ const DMChannel = require('../structures/DMChannel');
 const GroupDMChannel = require('../structures/GroupDMChannel');
 const Constants = require('../util/Constants');
 
+const kLru = Symbol('LRU');
+const lruable = ['group', 'dm'];
+
 /**
  * Stores channels.
  * @private
  * @extends {DataStore}
  */
 class ChannelStore extends DataStore {
+  constructor(iterable, options = {}) {
+    super(iterable);
+
+    if (options.lru) {
+      const lru = this[kLru] = [];
+      lru.add = item => {
+        lru.remove(item);
+        lru.unshift(item);
+        while (lru.length > options.lru) this.remove(lru[lru.length - 1]);
+      };
+      lru.remove = item => {
+        const index = lru.indexOf(item);
+        if (index > -1) lru.splice(index, 1);
+      };
+    }
+  }
+
+  get(key, peek = false) {
+    const item = super.get(key);
+    if (!item || !lruable.includes(item.type)) return item;
+    if (!peek && this[kLru]) this[kLru].add(key);
+    return item;
+  }
+
+  set(key, val) {
+    if (this[kLru] && lruable.includes(val.type)) this[kLru].add(key);
+    return super.set(key, val);
+  }
+
+  delete(key) {
+    const item = this.get(key, true);
+    if (!item) return false;
+    if (this[kLru] && lruable.includes(item.type)) this[kLru].remove(key);
+    return super.delete(key);
+  }
+
   create(data, guild, cache = true) {
     const existing = this.get(data.id);
     if (existing) return existing;