[Glitch] Emoji Rendering Efficiency

Port 6bca52453a to glitch-soc

Signed-off-by: Claire <claire.github-309c@sitedethib.com>

app/javascript/flavours/glitch/utils/cache.ts

@@ -0,0 +1,60 @@
+export interface LimitedCache<CacheKey, CacheValue> {
+  has: (key: CacheKey) => boolean;
+  get: (key: CacheKey) => CacheValue | undefined;
+  delete: (key: CacheKey) => void;
+  set: (key: CacheKey, value: CacheValue) => void;
+  clear: () => void;
+}
+
+interface LimitedCacheArguments {
+  maxSize?: number;
+  log?: (...args: unknown[]) => void;
+}
+
+export function createLimitedCache<CacheValue, CacheKey = string>({
+  maxSize = 100,
+  log = () => null,
+}: LimitedCacheArguments = {}): LimitedCache<CacheKey, CacheValue> {
+  const cacheMap = new Map<CacheKey, CacheValue>();
+  const cacheKeys = new Set<CacheKey>();
+
+  function touchKey(key: CacheKey) {
+    if (cacheKeys.has(key)) {
+      cacheKeys.delete(key);
+    }
+    cacheKeys.add(key);
+  }
+
+  return {
+    has: (key) => cacheMap.has(key),
+    get: (key) => {
+      if (cacheMap.has(key)) {
+        touchKey(key);
+      }
+      return cacheMap.get(key);
+    },
+    delete: (key) => cacheMap.delete(key) && cacheKeys.delete(key),
+    set: (key, value) => {
+      cacheMap.set(key, value);
+      touchKey(key);
+
+      const lastKey = cacheKeys.values().toArray().shift();
+      if (cacheMap.size > maxSize && lastKey) {
+        cacheMap.delete(lastKey);
+        cacheKeys.delete(lastKey);
+        log(
+          'Added %s and deleted %s from cache, now size %d',
+          key,
+          lastKey,
+          cacheMap.size,
+        );
+      } else {
+        log('Added %s to cache, now size %d', key, cacheMap.size);
+      }
+    },
+    clear: () => {
+      cacheMap.clear();
+      cacheKeys.clear();
+    },
+  };
+}