1 files changed, 48 insertions, 0 deletions
diff --git a/server/utils/limit-queue.js b/server/utils/limit-queue.js
new file mode 100644
index 0000000..9da6d41
--- /dev/null
+++ b/server/utils/limit-queue.js
@@ -0,0 +1,48 @@
+const { ArrayWithKey } = require("./array-with-key");
+
+/**
+ * Limit Queue
+ * The first element will be removed when the length exceeds the limit
+ */
+class LimitQueue extends ArrayWithKey {
+
+    /**
+     * The limit of the queue after which the first element will be removed
+     * @private
+     * @type {number}
+     */
+    __limit;
+    /**
+     * The callback function when the queue exceeds the limit
+     * @private
+     * @callback onExceedCallback
+     * @param {{key:K,value:V}|nul} item
+     */
+    __onExceed = null;
+
+    /**
+     * @param {number} limit The limit of the queue after which the first element will be removed
+     */
+    constructor(limit) {
+        super();
+        this.__limit = limit;
+    }
+
+    /**
+     * @inheritDoc
+     */
+    push(key, value) {
+        super.push(key, value);
+        if (this.length() > this.__limit) {
+            let item = this.shift();
+            if (this.__onExceed) {
+                this.__onExceed(item);
+            }
+        }
+    }
+
+}
+
+module.exports = {
+    LimitQueue
+};