Python-bindings-for-nodejs/python_bindings.js

import { PythonShell } from "python-shell";

export default class Bindings {
	constructor(initialProps) {

		this.pythonShell    = new PythonShell("./python/index.py", { mode: "text" });
		this.responseQueue  = new Array();
		this.sendQueue      = new Array();
		this.isSending      = false;
		this.streamCallback = null;

		this.pythonShell.on("message", function(message) {
			if (typeof message === "string" && message.startsWith("__STREAM__")) {
				var dataStr = message.substring(10);
				var data    = null;

				try {
					data = JSON.parse(dataStr);
				} catch (err) {
					console.error("Invalid streamed JSON:", dataStr);
					return;
				}

				if (this.streamCallback) {
					this.streamCallback(data);
				}

				return;
			}

			var response = null;

			try {
				response = JSON.parse(message);
			} catch (err) {
				console.error("Invalid JSON response:", message);
				var resolve = this.responseQueue.shift();

				if (resolve) {
					resolve({ error: "Invalid JSON from Python" });
				}

				return;
			}

			var resolve = this.responseQueue.shift();

			if (resolve) {
				resolve(response);
			}

			this.processSendQueue();

		}.bind(this));

		this.pythonShell.on("error", function(err) {
			console.error("PythonShell error:", err);
		});

		this.pythonShell.on("stderr", function(stderr) {
			console.error("PythonShell stderr:", stderr);
		});

		// Set initial properties if any
		if (initialProps && typeof initialProps === "object") {
			var keys = Object.keys(initialProps);

			for (var i = 0; i < keys.length; i++) {
				var key   = keys[i];
				var value = initialProps[key];

				this.callMethod("setProperty", key, value);
			}
		}

		return new Proxy(this, {
			get: function(target, prop) {
				if (typeof prop === "string") {
					if (prop === "end") {
						return target.end.bind(target);
					}

					if (prop === "onMessage") {
						return target.onMessage.bind(target);
					}

					return function() {
						var args = new Array(arguments.length);

						for (var i = 0; i < arguments.length; i++) {
							args[i] = arguments[i];
						}

						return target.callMethod(prop, ...args);
					};
				}

				return undefined;
			},

			set: function(target, prop, value) {
				return target.callMethod("setProperty", prop, value)
					.then(function() {
						return true;
					})
					.catch(function(err) {
						console.error(err);
						return false;
					});
			}
		});
	}

	onMessage(callback) {
		this.streamCallback = callback;
	}

	callMethod(method) {
		var args = new Array(arguments.length - 1);

		for (var i = 1; i < arguments.length; i++) {
			args[i - 1] = arguments[i];
		}

		return new Promise(function(resolve, reject) {
			this.responseQueue.push(function(response) {
				if (response.error) {
					reject(new Error(response.error));
				} else {
					resolve(response.result !== undefined ? response.result : response);
				}
			});

			var params = {};

			if (method === "setProperty" && args.length === 2) {
				params = { name: args[0], value: args[1] };
			} else if (args.length === 1 && typeof args[0] === "object") {
				params = args[0];
			} else if (args.length > 0) {
				params = { args: args };
			}

			this.sendQueue.push({ method: method, params: params });

			this.processSendQueue();

		}.bind(this));
	}

	processSendQueue() {
		if (this.isSending === true) {
			return;
		}

		if (this.sendQueue.length === 0) {
			return;
		}

		var message = this.sendQueue.shift();

		this.isSending = true;

		try {
			this.pythonShell.send(JSON.stringify(message));
		} catch (err) {
			var resolve = this.responseQueue.shift();

			if (resolve) {
				resolve({ error: err.message });
			}
		}

		this.isSending = false;
	}

	end() {
		this.pythonShell.end(function(err) {
			if (err !== undefined && err !== null) {
				console.error("Error ending PythonShell:", err);
			}
		});
	}
}