Fetch categories from DB

Author: yuxuanleong

Backend/MatchingService/rabbitmq/setup.js

@@ -5,15 +5,24 @@ const matching_exchange_name = "matching_exchange";
 const dead_letter_exchange_name = "dead_letter_exchange";
 const dead_letter_queue_name = "dead_letter_queue";
 const cancel_queue_name = "cancel_queue";
-const difficulties = ["easy", "medium", "hard", "any"]; // Add "any" for fallback
-const categories = ["data-structures", "strings", "arrays"]; // Adjust to include categories
-
-const queueNames = generator.generateQueueNames(
-    generator.generateCombinations(difficulties, categories)
-);
+const difficulties = ["easy", "medium", "hard", "any"];
+const axios = require('axios');
+const categoryAPIUrl = 'http://localhost:3001/api/categories';
+
+let queueNamesPromise = axios.get(categoryAPIUrl)
+    .then(response => {
+        const categories = response.data.map(category => category.name.toLowerCase().replace(/\s+/g, '-')); 
+        console.log("categories from api: ", categories)
+        return generator.generateQueueNames(generator.generateCombinations(difficulties, categories));
+    })
+    .catch(error => {
+        console.error("Error fetching categories:", error);
+        return []; // Return an empty array if categories couldn't be fetched
+    });
 
 async function setupRabbitMQ() {
     try {
+        const queueNames = await queueNamesPromise;
         const connection = await amqp.connect(process.env.RABBITMQ_URL);
 
         if (!connection) {
@@ -30,29 +39,27 @@ async function setupRabbitMQ() {
 
         // Declare and bind all main queues with TTL and DLQ bindings
         for (let queueName of queueNames) {
-            await channel.deleteQueue(queueName);  // Ensure we start fresh for each setup
+            await channel.deleteQueue(queueName); // Ensure we start fresh for each setup
 
             await channel.assertQueue(queueName, {
                 durable: true, 
                 arguments: {
-                    'x-message-ttl': 10000,  // 60 seconds TTL
-                    'x-dead-letter-exchange': dead_letter_exchange_name  // Bind to dead-letter exchange
+                    'x-message-ttl': 10000, // TTL for messages in the queue
+                    'x-dead-letter-exchange': dead_letter_exchange_name // Bind to dead-letter exchange
                 }
             });
 
             await channel.bindQueue(queueName, matching_exchange_name, queueName); // Bind to exchange
         }
 
-        // Delete DLQ before asserting it
+        // Delete and recreate the DLQ
         await channel.deleteQueue(dead_letter_queue_name);
-
-        // Declare the dead-letter queue and bind it to the dead-letter exchange
         await channel.assertQueue(dead_letter_queue_name, { durable: true });
         await channel.bindQueue(dead_letter_queue_name, dead_letter_exchange_name, ''); // Bind with no routing key
 
-        // Declare and bind the cancel queue
-        await channel.deleteQueue(cancel_queue_name);  // Delete any existing cancel queue
-        await channel.assertQueue(cancel_queue_name, { durable: true }); // Declare the cancel queue
+        // Delete and recreate the cancel queue
+        await channel.deleteQueue(cancel_queue_name);
+        await channel.assertQueue(cancel_queue_name, { durable: true });
         await channel.bindQueue(cancel_queue_name, matching_exchange_name, 'cancel'); // Bind with the "cancel" routing key
 
         console.log("RabbitMQ setup complete with queues, DLQ, and bindings.");
@@ -64,4 +71,4 @@ async function setupRabbitMQ() {
     }
 }
 
-module.exports = { setupRabbitMQ, matching_exchange_name, queueNames, dead_letter_queue_name , cancel_queue_name};
+module.exports = { setupRabbitMQ, matching_exchange_name, queueNamesPromise, dead_letter_queue_name, cancel_queue_name };

Backend/MatchingService/rabbitmq/subscriber.js

@@ -1,11 +1,11 @@
 const amqp = require('amqplib');
-const { queueNames } = require('./setup.js');
+const { queueNamesPromise } = require('./setup.js');
 // const { matchUsers } = require('../services/matchingService.js');
 const { notifyUsers } = require('../websocket/websocket');
 const { v4: uuidv4 } = require('uuid');
 // matchingService/fetchQuestion.js
 const axios = require('axios');
-const questionServiceUrl = 'http://localhost:3001/api/questions';
+const questionAPIUrl = 'http://localhost:3001/api/questions';
 
 
 // TODO: Subscribe and acknowledge messages with user info when timeout/user matched
@@ -69,7 +69,8 @@ function matchUsers(channel, msg, userId, difficulty, category) {
 
     if (waitingUsers[criteriaKey].length >= 2) {
         const matchedUsers = waitingUsers[criteriaKey].splice(0, 2);
-        delete waitingUsers[categoryKey];
+        removeMatchedUsersFromOtherLists(matchedUsers, categoryKey);
+        console.log("waitingusers after strict matching: ", waitingUsers)
         notifyMatch(channel, matchedUsers, category);
         return true;
     } 
@@ -80,7 +81,8 @@ function matchUsers(channel, msg, userId, difficulty, category) {
         console.log(`Fallback: User ${userId} added to ${categoryKey}. Waiting list: ${waitingUsers[categoryKey].length}`);
         if (waitingUsers[categoryKey].length >= 2) {
             const matchedUsers = waitingUsers[categoryKey].splice(0, 2);
-            delete waitingUsers[criteriaKey];
+            removeMatchedUsersFromOtherLists(matchedUsers, criteriaKey);
+            console.log("waitingusers after lenient matching: ", waitingUsers)
             notifyMatch(channel, matchedUsers, category);
             return true;
         }
@@ -89,12 +91,22 @@ function matchUsers(channel, msg, userId, difficulty, category) {
     return false;
 }
 
+function removeMatchedUsersFromOtherLists(matchedUsers, keyToSkip) {
+    for (const key in waitingUsers) {
+        if (key !== keyToSkip) {
+            waitingUsers[key] = waitingUsers[key].filter(
+                user => !matchedUsers.some(matchedUser => matchedUser.userId === user.userId)
+            );
+        }
+    }
+}
+
 async function notifyMatch(channel, matchedUsers, category) {
     const roomId = uuidv4();
 
     try {
         // Fetch a question from QuestionService based on category
-        const response = await axios.get(`${questionServiceUrl}/by-category`, {
+        const response = await axios.get(`${questionAPIUrl}/by-category`, {
             params: { category: category }
         });
 
@@ -242,6 +254,7 @@ async function rejectMessage(channel, msg, userId) {
 
 async function consumeQueue() {
     try {
+        const queueNames = await queueNamesPromise;
         const connection = await amqp.connect(process.env.RABBITMQ_URL);
         const channel = await connection.createChannel();