Rewrote the api rate limiter with promises instead of callbacks

database/001_systems.sql

@@ -0,0 +1,6 @@
+CREATE TABLE systems (
+       id INTEGER PRIMARY KEY,
+       symbol TEXT NOT NULL UNIQUE,
+       data TEXT NOT NULL,
+       updated DATE DEFAULT (datetime('now'))
+);

database/db.js

@@ -3,6 +3,7 @@ import Database from 'better-sqlite3';
 
 const allMigrations = [
 	'database/000_init.sql',
+	'database/001_systems.sql',
 ];
 
 const db = new Database(

database/systems.js

@@ -0,0 +1,26 @@
+import db from './db.js';
+
+const getSystemStatement = db.prepare(`SELECT data from systems where symbol = ?;`);
+const setSystemStatement = db.prepare(`INSERT INTO systems(symbol, data) VALUES (?, ?);`);
+
+export function getSystem(symbol) {
+	try {
+		const data = getSystemStatement.get(symbol);
+		if (data === undefined) {
+			return null;
+		}
+		return JSON.parse(data.data);
+	} catch (err) {
+		console.log(err);
+		return null;
+	}
+}
+
+export function setSystem(symbol, data) {
+	try {
+		return setSystemStatement.run(symbol, JSON.stringify(data)).lastInsertRowid;
+	} catch (err) {
+		console.log(err);
+		return null;
+	}
+}

lib/api.js

@@ -5,32 +5,28 @@ let busy = false; // lets us know if we are already sending api requests or not.
 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.
 
-// chain takes an array of actions as argument. For each one it sets the `next` property.
-// example action: {
-//    action: function to call,
-//    next: optional nested action object, would get overriden by this function, except for the last action,
-//    ... other attributes as required by the action function (for example ship or waypoing symbol...)
-// }
-export function chain(actions) {
-	for(let i=actions.length-1;i>0;--i) {
-		actions[i-1].next = actions[i];
-	}
-	actions[0].action(actions[0]);
-}
-
-// send takes a data object as argument
-// example data: {
+// send takes a request object as argument and an optional context ctx
+// example request: {
 //    endpoint: the url endpoint to call,
 //    method: HTTP method for `fetch` call, defaults to 'GET',
-//    next: optional nested action object, as specified above with the chain function,
 //    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(data) {
-	if (!busy) {
-		send_this(data);
-	} else {
-		queue.enqueue(data, data.priority ? data.priority : 10);
-	}
+export function send(request, ctx) {
+	return new Promise((resolve, reject) => {
+		let data = {
+			ctx: ctx,
+			reject: reject,
+			request: request,
+			resolve: resolve,
+		};
+		if (!busy) {
+			busy = true;
+			send_this(data);
+		} else {
+			queue.enqueue(data, request.priority ? request.priority : 10);
+		}
+	});
 }
 
 function send_next() {
@@ -41,6 +37,7 @@ function send_next() {
 	}
 }
 
+// send_this take a data object as argument built in the send function above
 function send_this(data) {
 	if (headers === undefined) {
 		const token = getToken();
@@ -55,22 +52,20 @@ function send_this(data) {
 	let options = {
 		headers: headers,
 	};
-	if (data.method !== undefined) {
-		options['method'] = data.method;
+	if (data.request.method !== undefined) {
+		options['method'] = data.request.method;
 	}
-	if (data.payload !== undefined) {
-		options['body'] = JSON.stringify(data.payload);
+	if (data.request.payload !== undefined) {
+		options['body'] = JSON.stringify(data.request.payload);
 	}
-	busy = true;
-	fetch(`https://api.spacetraders.io/v2${data.endpoint}`, options)
+	fetch(`https://api.spacetraders.io/v2${data.request.endpoint}`, options)
 		.then(response => response.json())
-		.then(response => {
-			if (data.next !== undefined) { // if we have a next action, call it now
-				data.next.action(data.next, response);
-			} else { // otherwise use this debug action
-				console.log(JSON.stringify(response, null, 2));
-			}
-		})
-		.catch(err => console.error(err));
+		.then(response => data.resolve(response))
+		.catch(err => data.reject(err));
 	setTimeout(send_next, 500);
 }
+
+export function debugLog(ctx) {
+	console.log(`--- ${Date()} -----------------------------------------------------------------------------`);
+	console.log(JSON.stringify(ctx, null, 2));
+}

lib/systems.js

@@ -0,0 +1,36 @@
+import * as api from './api.js';
+import * as db from '../database/systems.js';
+
+// Retrieves a list of waypoints that have a specific ctx.trait like a SHIPYARD or a MARKETPLACE in the system ctx.symbol
+export async function trait(ctx) {
+	const s = await getSystem(ctx);
+	return s.filter(s => s.traits.some(t => t.symbol === ctx.trait));
+}
+
+// Retrieves a list of waypoints that have a specific ctx.type like ASTEROID_FIELD in the system ctx.symbol
+export async function type(ctx, response) {
+	const s = await getSystem(ctx);
+	return s.filter(s => s.type === ctx.type);
+}
+
+// Retrieves the system's information for ctx.symbol and cache it in the database
+async function getSystem(ctx) {
+	let s = db.getSystem(ctx.symbol);
+	if (s === null) {
+		const response = await api.send({endpoint: `/systems/${ctx.symbol}/waypoints?limit=20&page=1`});
+		if (response.error !== undefined) {
+			switch(response.error.code) {
+			case 404:
+				throw `Error retrieving waypoints for system ${ctx.symbol}: ${response.error.message}`;
+			default: // yet unhandled error
+				throw response;
+			}
+		}
+		if (response.meta !== undefined && response.meta.total > response.meta.limit) {
+			throw `Error retrieving waypoints for system ${ctx.symbol}: Pagination is not implemented yet!`;
+		}
+		s = response.data;
+		db.setSystem(ctx.symbol, s);
+	}
+	return s;
+}

main.js

@@ -1,6 +1,7 @@
 import * as agent from './lib/agent.js';
 import * as api from './lib/api.js';
 import * as ships from './lib/ships.js';
+import * as systems from './lib/systems.js';
 
 function usage() {
 	console.log(`contracts\t\t\tList all of your contracts.
@@ -72,11 +73,11 @@ default:
 	case 'sell':
 		ships.sell({ship: process.argv[3], good: process.argv[4], units: process.argv[5]});
 		break;
-	case 'shipyard':
-		api.send({endpoint: `/systems/${process.argv[3]}/waypoints/${process.argv[4]}/shipyard`});
+	case 'asteroids':
+		api.debugLog(await systems.type({symbol: process.argv[3], type: 'ASTEROID_FIELD'}));
 		break;
-	case 'waypoints':
-		api.send({endpoint: `/systems/${process.argv[3]}/waypoints?limit=20&page=1`});
+	case 'shipyards':
+		api.debugLog(await systems.trait({symbol: process.argv[3], trait: 'SHIPYARD'}));
 		break;
 	default:
 		usage();