From 82043f530809785bcdc50554e0b9337078c6d7c8 Mon Sep 17 00:00:00 2001
From: "Cimon Lucas (LCM)" <lucas_cimon@connect-tech.sncf>
Date: Wed, 16 Nov 2022 15:16:55 +0100
Subject: [PATCH] Adding MockPortBinding.writeToPort &
 MockBinding.getOpenMockPort()

---
 lib/index-test.ts | 48 ++++++++++++++++++++++++++++++++++++++++++++++-
 lib/index.ts      | 20 +++++++++++++++++++-
 2 files changed, 66 insertions(+), 2 deletions(-)

diff --git a/lib/index-test.ts b/lib/index-test.ts
index 43ad031..49346b5 100644
--- a/lib/index-test.ts
+++ b/lib/index-test.ts
@@ -27,7 +27,7 @@ const openOptions: OpenOptions = {
 }
 
 describe('MockBinding', () => {
-  afterEach(() => {
+  beforeEach(() => {
     MockBinding.reset()
   })
 
@@ -88,5 +88,51 @@ describe('MockBinding', () => {
         assert.strictEqual(port.port.info.serialNumber, '1')
       })
     })
+    describe('getOpenMockPort', () => {
+      beforeEach(async () => {
+        MockBinding.reset()
+      })
+
+      it('should return a value for an existing open port', async () => {
+        MockBinding.createPort('/dev/exists')
+        await MockBinding.open(openOptions)
+        const openPort = MockBinding.getOpenMockPort('/dev/exists')
+        assert.strictEqual(openPort.port.info.serialNumber, '1')
+      })
+
+      it('should return undefined for an unknown port path', async () => {
+        const openPort = MockBinding.getOpenMockPort('/dev/unknown')
+        assert.strictEqual(openPort, undefined)
+      })
+
+      it('should return undefined for an existing port that is not open', async () => {
+        MockBinding.createPort('/dev/exists')
+        const openPort = MockBinding.getOpenMockPort('/dev/exists')
+        assert.strictEqual(openPort, undefined)
+      })
+    })
+  })
+})
+
+describe('MockPortBinding', () => {
+  beforeEach(() => {
+    MockBinding.reset()
+  })
+
+  describe('instance property', () => {
+    describe('writeToPort', () => {
+      it('can send data from one port to another', async () => {
+        MockBinding.createPort('/dev/exists')
+        const port1 = await MockBinding.open(openOptions)
+        const port2 = await MockBinding.open(openOptions)
+        port1.writeToPort = port2
+
+        const message = Buffer.from('MSG')
+        await port1.write(message)
+        const receivingBuffer = Buffer.alloc(message.length)
+        await port2.read(receivingBuffer, 0, message.length)
+        assert.isTrue(receivingBuffer.equals(message))
+      })
+    })
   })
 })
diff --git a/lib/index.ts b/lib/index.ts
index cedb871..db74ae2 100644
--- a/lib/index.ts
+++ b/lib/index.ts
@@ -25,6 +25,9 @@ export interface CreatePortOptions {
 let ports: {
   [key: string]: MockPortInternal
 } = {}
+let openMockPortBindings: {
+  [key: string]: MockPortBinding
+} = {};
 let serialNumber = 0
 
 function resolveNextTick() {
@@ -42,11 +45,13 @@ export class CanceledError extends Error {
 export interface MockBindingInterface extends BindingInterface<MockPortBinding> {
   reset(): void
   createPort(path: string, opt?: CreatePortOptions): void
+  getOpenMockPort(path: string): MockPortBinding
 }
 
 export const MockBinding: MockBindingInterface = {
   reset() {
     ports = {}
+    openMockPortBindings = {}
     serialNumber = 0
   },
 
@@ -82,6 +87,10 @@ export const MockBinding: MockBindingInterface = {
     debug(serialNumber, 'created port', JSON.stringify({ path, opt: options }))
   },
 
+  getOpenMockPort(path) {
+    return openMockPortBindings[path];
+  },
+
   async list() {
     debug(null, 'list')
     return Object.values(ports).map(port => port.info)
@@ -133,7 +142,9 @@ export const MockBinding: MockBindingInterface = {
 
     port.openOpt = { ...openOptions }
 
-    return new MockPortBinding(port, openOptions)
+    const portBinding = new MockPortBinding(port, openOptions)
+    openMockPortBindings[path] = portBinding
+    return portBinding
   },
 }
 
@@ -149,6 +160,7 @@ export class MockPortBinding implements BindingPortInterface {
   writeOperation: null | Promise<void>
   isOpen: boolean
   serialNumber?: string
+  writeToPort?: MockPortBinding
 
   constructor(port: MockPortInternal, openOptions: Required<OpenOptions>) {
     this.port = port
@@ -289,6 +301,12 @@ export class MockPortBinding implements BindingPortInterface {
             this.emitData(data)
           }
         })
+      } else if (this.writeToPort) {
+        process.nextTick(() => {
+          if (this.writeToPort.isOpen) {
+            this.writeToPort.emitData(data);
+          }
+        });
       }
       this.writeOperation = null
       debug(this.serialNumber, 'writing finished')