From 36cc33f9e96a38ecea98ac8d26275b4828347d80 Mon Sep 17 00:00:00 2001
From: Julien Dessaux
Date: Sat, 1 Jul 2023 23:13:13 +0200
Subject: Moved the nodejs agent to its own subfolder to make room for my
 haskell agent

---
 nodejs/lib/api.js | 140 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 140 insertions(+)
 create mode 100644 nodejs/lib/api.js

(limited to 'nodejs/lib/api.js')

diff --git a/nodejs/lib/api.js b/nodejs/lib/api.js
new file mode 100644
index 0000000..667ef37
--- /dev/null
+++ b/nodejs/lib/api.js
@@ -0,0 +1,140 @@
+import * as fs from 'fs';
+import * as events from 'events';
+
+import { getToken } from '../database/config.js';
+import { PriorityQueue } from './priority_queue.js';
+
+// queue processor module variables
+const bus = new events.EventEmitter(); // a bus to notify the queue processor to start processing messages
+let busy = false; // true if we are already sending api requests.
+let backoffSeconds = 0;
+let running = false;
+// other module variables
+let headers = undefined; // a file scope variable so that we only evaluate these once.
+let queue = new PriorityQueue(); // a priority queue to hold api calls we want to send, allows for throttling.
+
+// a single queue processor should be running at any time, otherwise there will be trouble!
+async function queue_processor() {
+	if (running) {
+		throw 'refusing to start a second queue processor';
+	}
+	running = true;
+	while(true) {
+		try {
+			if (backoffSeconds > 0) {
+				await sleep(backoffSeconds * 1000);
+				backoffSeconds = 0;
+			}
+			if (queue.isEmpty()) {
+				busy = false;
+				await new Promise(resolve => bus.once('send', resolve));
+				busy = true;
+			}
+			const before = new Date();
+			await send_this(queue.dequeue().element);
+			const duration = new Date() - before;
+			if (duration < 400) { // 333 should work, but 400 should still allow some manual requests to go through during development
+				await sleep(400 - duration);
+			}
+		} catch (e) {
+			running = false;
+			throw e;
+		}
+	}
+}
+queue_processor();
+
+// send takes a request object as argument and an optional context ctx
+// example request: {
+//    endpoint: the path part of the url to call,
+//    method: HTTP method for `fetch` call, defaults to 'GET',
+//    payload: optional json object that will be send along with the request,
+//    priority: optional priority value (defaults to 10, lower than 10 means the message will be sent faster)
+// }
+export function send(request, ctx) {
+	return new Promise((resolve, reject) => {
+		let data = {
+			ctx: ctx,
+			reject: reject,
+			request: request,
+			resolve: resolve,
+		};
+		queue.enqueue(data, request.priority ? request.priority : 10);
+		if (!busy) {
+			bus.emit('send'); // the queue was previously empty, let's wake up the queue_processor
+		}
+	});
+}
+
+// send_this take a data object as argument built in the send function above
+async function send_this(data) {
+	if (headers === undefined) {
+		const token = getToken();
+		if (token === null) {
+			throw 'Could not get token from the database. Did you init or register yet?';
+		}
+		headers = {
+			'Content-Type': 'application/json',
+			'Authorization': `Bearer ${token}`
+		};
+	}
+	let options = {
+		headers: headers,
+	};
+	if (data.request.method !== undefined) {
+		options['method'] = data.request.method;
+	}
+	if (data.request.payload !== undefined) {
+		options['body'] = JSON.stringify(data.request.payload);
+	}
+	fs.writeFileSync('log', JSON.stringify({event: 'send', date: new Date(), data: data}) + '\n', {flag: 'a+'});
+	try {
+		let response = await fetch(`https://api.spacetraders.io/v2${data.request.endpoint}`, options);
+		response = await response.json();
+		switch(response.error?.code) {
+			//case 401: // TODO 401 means a server reset happened
+			// TODO reject all promises in queue
+			// close database file
+			// rm database file
+			// logrotate
+			// spawnSync
+			// break;
+		case 429:  // 429 means rate limited, let's hold back as instructed
+			backoffSeconds = response.error.data.retryAfter;
+			queue.enqueue(data, 1);
+			break;
+		case 503:  // 503 means maintenance mode, let's hold back for 1 minute
+			backoffSeconds = 60;
+			queue.enqueue(data, 1);
+			break;
+		default: // no error!
+			fs.writeFileSync('log', JSON.stringify({event: 'response', date: new Date(), data: response}) + '\n', {flag: 'a+'});
+			return data.resolve(response);
+		}
+	} catch (err) {
+		fs.writeFileSync('log', JSON.stringify({event: 'error', date: new Date(), data: err}) + '\n', {flag: 'a+'});
+		switch(err.cause?.code) {
+		case 'EAI_AGAIN': // DNS lookup timed out error, let's hold back for 5 seconds
+			backoffSeconds = 5;
+			queue.enqueue(data, 1);
+			break;
+		case 'ECONNRESET':
+			queue.enqueue(data, 1);
+			break;
+		case 'UND_ERR_CONNECT_TIMEOUT':
+			queue.enqueue(data, 1);
+			break;
+		default:
+			data.reject(response);
+		}
+	}
+}
+
+export function debugLog(ctx) {
+	console.log(`--- ${Date()} -----------------------------------------------------------------------------`);
+	console.log(JSON.stringify(ctx, null, 2));
+}
+
+export function sleep(delay) {
+	return new Promise((resolve) => setTimeout(resolve, delay))
+}
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