From 0d6b0d52a4dd80ce3eb9e6bdeb3e594deb618d29 Mon Sep 17 00:00:00 2001
From: J-Rojas <jrojas@redlinesoftworks.com>
Date: Mon, 16 May 2022 09:11:10 -0700
Subject: [PATCH] PR to refactor and address #16 "Support bidirectional
 exec/operation"

---
 src/comm.js | 189 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 189 insertions(+)
 create mode 100644 src/comm.js

diff --git a/src/comm.js b/src/comm.js
new file mode 100644
index 0000000..74b3fa3
--- /dev/null
+++ b/src/comm.js
@@ -0,0 +1,189 @@
+const TinyEmitter = require('./tiny-emitter');
+
+const MESSAGE_RESULT = 0;
+const MESSAGE_EVENT = 1;
+
+const RESULT_ERROR = 0;
+const RESULT_SUCCESS = 1;
+
+const DEFAULT_HANDLER = 'main';
+
+class TransferableResponse {
+    constructor(payload, transferable) {
+      this.payload = payload;
+      this.transferable = transferable;
+    }
+}
+
+const isPromise = o => typeof o === 'object' && typeof o.then === 'function' && typeof o.catch === 'function';
+
+class Communicator extends TinyEmitter {
+    
+    constructor(messagePort, defaultHandler) {
+        super()
+        this._messageId = 1;
+        this._messagePort = messagePort
+        this._handlers = {[DEFAULT_HANDLER]: defaultHandler};
+        this._outgoing = new Map()
+        this._incoming = new Map()
+    }
+
+    /**
+     * return true if there is no unresolved jobs
+     * @returns {boolean}
+     */
+    isFree() {
+        return this._outgoing.size === 0;
+    }
+
+    jobsLength() {
+        return this._outgoing.size;
+    }
+
+    /**
+     * @param operationName string
+     * @param data any
+     * @param transferable array
+     * @param onEvent function
+     * @returns {Promise}
+     */
+    exec(operationName, data = null, transferable = [], onEvent) {
+        return new Promise((res, rej) => {
+            const messageId = this._messageId++;
+            this._outgoing.set(messageId, [res, rej, onEvent]);
+            this._messagePort.postMessage([messageId, data, operationName], transferable || []);
+        });
+    }
+
+    /**
+     *
+     * @param data any
+     * @param transferable array
+     * @param onEvent function
+     * @returns {Promise}
+     */
+    postMessage(data = null, transferable = [], onEvent) {
+        return new Promise((res, rej) => {
+            const messageId = this._messageId++;
+            this._outgoing.set(messageId, [res, rej, onEvent]);
+            this._messagePort.postMessage([messageId, data], transferable || []);
+        });
+    }
+
+    emit(eventName, ...args) {
+        if (args.length == 1 && args[0] instanceof TransferableResponse) {
+            this._messagePort.postMessage({eventName, args}, args[0].transferable);
+        } else {
+            this._messagePort.postMessage({eventName, args});
+        }
+        return this;
+    }
+
+    emitLocally(eventName, ...args) {
+        super.emit(eventName, ...args);
+    }
+
+    operation(name, handler) {
+        this._handlers[name] = handler;
+        return this;
+    }
+
+    _onRun(messageId, payload, handlerName) {
+
+        const runFn = (messageId, payload, handlerName) =>  {
+            const handler = this._handlers[handlerName || DEFAULT_HANDLER];
+            if(!handler)
+            throw new Error(`Not found handler for this request`);
+
+            return handler(payload, sendEvent.bind(null, messageId))
+        };
+
+        const sendResult = (messageId, success, payload, transferable = []) => {
+            this._messagePort.postMessage([MESSAGE_RESULT, messageId, success, payload], transferable);
+        };
+
+        const sendEvent = (messageId, eventName, payload) => {
+            if(!eventName)
+            throw new Error('eventName is required');
+
+            if(typeof eventName !== 'string')
+            throw new Error('eventName should be string');
+
+            this._messagePort.postMessage([MESSAGE_EVENT, messageId, eventName, payload]);
+        };
+
+        const onSuccess = (result) => {
+            if(result && result instanceof TransferableResponse) {
+                sendResult(messageId, RESULT_SUCCESS, result.payload, result.transferable);
+            }
+            else {
+                sendResult(messageId, RESULT_SUCCESS, result);
+            }
+        };
+
+        const onError = (e) => {
+            sendResult(messageId, RESULT_ERROR, {
+                message: e.message,
+                stack: e.stack
+            });
+        };
+
+        try {
+            const result = runFn(messageId, payload, handlerName);
+            if(isPromise(result)) {
+                result.then(onSuccess).catch(onError);
+            } else {
+                onSuccess(result);
+            }
+        } catch (e) {
+            onError(e);
+        }
+
+    }
+
+    _onMessage(data) {
+        if(Array.isArray(data)) {
+            if (data.length == 4) {
+                // event
+                this._onResponse(data)
+            } else {
+                // event response
+                this._onRun(...data);
+            }
+        } else if(data && data.eventName) {
+            this.emitLocally(data.eventName, ...data.args);
+        }
+    }
+
+    _onResponse(e) {
+        const [type, ...args] = e;
+
+        if(type === MESSAGE_EVENT)
+            this._onEvent(...args);
+        else if(type === MESSAGE_RESULT)
+            this._onResult(...args);
+        else
+            throw new Error(`Wrong message type '${type}'`);
+    }
+
+    _onResult(messageId, success, payload) {
+        const [res, rej] = this._outgoing.get(messageId);
+        this._outgoing.delete(messageId);
+
+        return success === RESULT_SUCCESS ? res(payload) : rej(payload);
+    }
+
+    _onEvent(messageId, eventName, data) {
+        const [,,onEvent] = this._outgoing.get(messageId);
+
+        if(onEvent) {
+            onEvent(eventName, data);
+        }
+    }
+
+}
+
+module.exports = {
+    Communicator,
+    TransferableResponse
+}
\ No newline at end of file