perf(plugin-shikiji): 优化开发时编译速度

plugins/plugin-shikiji/src/node/lru.ts

@@ -0,0 +1,39 @@
+// adapted from https://stackoverflow.com/a/46432113/11613622
+
+export class LRUCache<K, V> {
+  private max: number
+  private cache: Map<K, V>
+
+  constructor(max: number = 10) {
+    this.max = max
+    this.cache = new Map<K, V>()
+  }
+
+  get(key: K): V | undefined {
+    const item = this.cache.get(key)
+    if (item !== undefined) {
+      // refresh key
+      this.cache.delete(key)
+      this.cache.set(key, item)
+    }
+    return item
+  }
+
+  set(key: K, val: V): void {
+    // refresh key
+    if (this.cache.has(key))
+      this.cache.delete(key)
+    // evict oldest
+    else if (this.cache.size === this.max)
+      this.cache.delete(this.first()!)
+    this.cache.set(key, val)
+  }
+
+  first(): K | undefined {
+    return this.cache.keys().next().value
+  }
+
+  clear(): void {
+    this.cache.clear()
+  }
+}