pref: optimize the diff to make it more accurately reflect changes (#11)

* pref: optimize the diff to make it more accurately reflect changes

* pref: optimize the diff page selection

app/.client/utils/lru-cache.ts

@@ -0,0 +1,42 @@
+export class LRUCache<K, V> {
+  private cache = new Map<K, V>();
+  private maxSize: number;
+
+  constructor(maxSize: number) {
+    this.maxSize = maxSize;
+  }
+
+  get(key: K): V | undefined {
+    if (!this.cache.has(key)) {
+      return undefined;
+    }
+    const value = this.cache.get(key)!;
+    this.cache.delete(key);
+    this.cache.set(key, value);
+    return value;
+  }
+
+  set(key: K, value: V): void {
+    if (this.cache.has(key)) {
+      this.cache.delete(key);
+    } else if (this.cache.size >= this.maxSize) {
+      const firstKey = this.cache.keys().next().value;
+      if (firstKey !== undefined) {
+        this.cache.delete(firstKey);
+      }
+    }
+    this.cache.set(key, value);
+  }
+
+  has(key: K): boolean {
+    return this.cache.has(key);
+  }
+
+  clear(): void {
+    this.cache.clear();
+  }
+
+  get size(): number {
+    return this.cache.size;
+  }
+}