Add a Port pool manager to handle specific port atribution

lib/PortManager.js

@@ -0,0 +1,60 @@
+import Debug from 'debug';
+
+class PortManager {
+  constructor(opt) {
+    this.debug = Debug('lt:PortManager');
+    this.range = opt.range || null;
+    this.first = null;
+    this.last = null;
+    this.pool = {};
+    this.initializePool();
+  }
+
+  initializePool() {
+    if (this.range === null) {
+      return;
+    }
+
+    if (!/^[0-9]+:[0-9]+$/.test(this.range)) {
+      throw new Error('Bad range expression: ' + this.range);
+    }
+
+    [this.first, this.last] = this.range.split(':').map((port) => parseInt(port));
+
+    if (this.first > this.last) {
+      throw new Error('Bad range expression min > max: ' + this.range);
+    }
+
+    for (let port = this.first; port <= this.last; port++) {
+      this.pool['_' + port] = null;
+    }
+    this.debug = Debug('lt:PortManager');
+    this.debug('Pool initialized ' + JSON.stringify(this.pool));
+  }
+
+  release(port) {
+    if (this.range === null) {
+      return;
+    }
+    this.debug('Release port ' + port);
+    this.pool['_' + port] = null;
+  }
+
+  getNextAvailable(clientId) {
+    if (this.range === null) {
+      return null;
+    }
+
+    for (let port = this.first; port <= this.last; port++) {
+      if (this.pool['_' + port] === null) {
+        this.pool['_' + port] = clientId;
+        this.debug('Port found ' + port);
+        return port;
+      }
+    }
+    this.debug('No more ports available ');
+    throw new Error('No more ports available in range ' + this.range);
+  }
+}
+
+export default PortManager;

lib/PortManager.test.js

@@ -0,0 +1,51 @@
+import assert from 'assert';
+
+import PortManager from './PortManager';
+
+describe('PortManager', () => {
+    it('should construct with no range', () => {
+      const portManager = new PortManager({});
+      assert.equal(portManager.range, null);
+      assert.equal(portManager.first, null);
+      assert.equal(portManager.last, null);
+    });
+
+    it('should construct with range', () => {
+      const portManager = new PortManager({range: '10:20'});
+      assert.equal(portManager.range, '10:20');
+      assert.equal(portManager.first, 10);
+      assert.equal(portManager.last, 20);
+    });
+
+    it('should not construct with bad range expression', () => {
+      assert.throws(()=>{
+        new PortManager({range: 'a1020'});
+      }, /Bad range expression: a1020/)
+    });
+
+    it('should not construct with bad range max>min', () => {
+      assert.throws(()=>{
+        new PortManager({range: '20:10'});
+      }, /Bad range expression min > max: 20:10/)
+    });
+
+    it('should work has expected', async () => {
+      const portManager = new PortManager({range: '10:12'});
+      assert.equal(10,portManager.getNextAvailable('a'));
+      assert.equal(11,portManager.getNextAvailable('b'));
+      assert.equal(12,portManager.getNextAvailable('c'));
+
+      assert.throws(()=>{
+        portManager.getNextAvailable();
+      }, /No more ports available in range 10:12/)
+
+      portManager.release(11);
+      assert.equal(11,portManager.getNextAvailable('bb'));
+
+      portManager.release(10);
+      portManager.release(12);
+
+      assert.equal(10,portManager.getNextAvailable('cc'));
+      assert.equal(12,portManager.getNextAvailable('dd'));
+    });
+});