From 3da6befe1058816f122e269f7e37bde9a83c970b Mon Sep 17 00:00:00 2001
From: Book Pauk <bookpauk@gmail.com>
Date: Sun, 26 Jan 2020 18:38:09 +0700
Subject: [PATCH] =?UTF-8?q?=D0=94=D0=BE=D0=B1=D0=B0=D0=B2=D0=BB=D0=B5?=
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---
 server/core/LimitedQueue.js | 120 ++++++++++++++++++++++++++++++++++++
 1 file changed, 120 insertions(+)
 create mode 100644 server/core/LimitedQueue.js

diff --git a/server/core/LimitedQueue.js b/server/core/LimitedQueue.js
new file mode 100644
index 00000000..fd9d68e0
--- /dev/null
+++ b/server/core/LimitedQueue.js
@@ -0,0 +1,120 @@
+const cleanPeriod = 60*1000;//1 минута
+const cleanTimeout = 60;//timeout в минутах (cleanPeriod)
+
+class LimitedQueue {
+    constructor(enqueueAfter = 10, size = 100, timeout = cleanTimeout) {//timeout в минутах (cleanPeriod)
+        this.size = size;
+        this.timeout = timeout;
+
+        this.freed = enqueueAfter;
+        this.listeners = [];
+
+        this.timer = setTimeout(() => { this.periodicClean(); }, cleanPeriod);
+    }
+
+    _addListener(listener) {
+        this.listeners.push(Object.assign({regTime: Date.now()}, listener));
+    }
+
+    //отсылаем сообщение первому ожидающему и удаляем его из списка
+    _emitFree() {
+        if (this.listeners.length > 0) {
+            let listener = this.listeners.shift();
+            listener.onFree();
+
+            const now = Date.now();
+            for (let i = 0; i < this.listeners.length; i++) {
+                listener = this.listeners[i];
+                listener.regTime = now;
+                listener.onPlaceChange(i + 1);
+            }
+
+        }
+    }
+
+    get(onPlaceChange) {
+        return new Promise((resolve, reject) => {
+            if (this.destroyed)
+                reject('destroyed');
+
+            const take = () => {
+                if (this.freed <= 0)
+                    throw new Error('Ошибка получения ресурсов в очереди ожидания');
+
+                this.freed--;
+
+                let returned = false;
+                return {
+                    ret: () => {
+                        if (!returned) {
+                            this.freed++;
+                            this._emitFree();
+                            returned = true;
+                        }
+                    }
+                };
+            };
+
+            if (this.freed > 0) {
+                resolve(take());
+            } else {
+                if (this.listeners.length < this.size) {
+                    this._addListener({
+                        onFree: () => {
+                            resolve(take());
+                        },
+                        onError: (err) => {
+                            reject(err);
+                        },
+                        onPlaceChange: (i) => {
+                            if (onPlaceChange)
+                                onPlaceChange(i);
+                        }
+                    });
+                    if (onPlaceChange)
+                        onPlaceChange(this.listeners.length);
+                } else {
+                    reject('Превышен размер очереди ожидания');
+                }
+            }
+        });
+    }
+
+    destroy() {
+        if (this.timer) {
+            clearTimeout(this.timer);
+            this.timer = null;
+        }
+
+        for (const listener of this.listeners) {
+            listener.onError('destroy');
+        }
+        this.listeners = [];
+
+        this.destroyed = true;
+    }
+
+    periodicClean() {
+        try {
+            this.timer = null;
+
+            const now = Date.now();
+            //чистка listeners, убираем зависшие в очереди на одном месте
+            let newListeners = [];
+            for (const listener of this.listeners) {
+                if (now - listener.regTime < this.timeout*cleanPeriod - 50) {
+                    newListeners.push(listener);
+                } else {
+                    listener.onError('Время ожидания в очереди истекло');
+                }
+            }
+            this.listeners = newListeners;
+        } finally {
+            if (!this.destroyed) {
+                this.timer = setTimeout(() => { this.periodicClean(); }, cleanPeriod);
+            }
+        }
+    }
+}
+
+module.exports = LimitedQueue;
\ No newline at end of file