resolve some logic error within the matching algorithm

Author: Nanxi-Huang

peer-prep/src/matching-service/controllers/matchingController.js

@@ -2,16 +2,30 @@ const matchingService = require('../services/matchingService');
 
 async function findMatch(req, res, next) {
     try {
-        const { id, language, proficiency, difficulty, topic } = req.body;
+        const {language, proficiency, difficulty, topic } = req.body;
+        const id = req.params.userId; // Extract user id from request params
         console.log(req.body);
         console.log(`${id}, ${language}, ${proficiency}, ${difficulty}, ${topic}`);
 
-        const matchResult = await matchingService.findMatch({ id, language, proficiency, difficulty, topic });
-
-        res.status(200).json(matchResult);
+        const matchResult = await matchingService.findMatch({id, language, proficiency, difficulty, topic});
+        
+        switch(matchResult.status) {
+            case 'success':
+                res.status(200).json(matchResult);
+                break;
+            case 'failed': 
+                res.status(400).json(matchResult);
+                break;
+            case 'cancel':
+                res.status(200).json(matchResult);
+                break;
+            default:
+                res.status(500).json({message:'Failed to find a match. Please try again!'});
+        }
 
     } catch (error) {
-        next(error);
+        console.error(error);
+        res.status(500).json({message:'Failed to find a match. Please try again!'})
     }
 }
 

peer-prep/src/matching-service/database/matchedPairDb.js

@@ -38,7 +38,12 @@ async function endSession(sessionId) {
     try {
         const filter = { sessionId: sessionId };
         const update = { $set: { isEnded: true } };
-        await MatchedPair.updateOne(filter, update);
+        const result = await MatchedPair.updateOne(filter, update);
+
+        if (result.nModified == 0) {
+            console.warn(`No session was updated for session ${sessionId}`);
+        }
+
         console.log(`Successfully update session state for session ${sessionId}`);
 
     } catch (error) {

peer-prep/src/matching-service/server.js

@@ -1,16 +1,17 @@
 const express = require('express');
 const app = express();
 const mongoose = require('mongoose');
-const bodyParser = require('body-parser');
-const routes = require('./routes/routes');
 const config = require('./config/config');
+const routes = require('./routes/routes');
+
 
 mongoose.connect(config.mongodbUri, {
     useNewUrlParser: true,
     useUnifiedTopology: true,
 });
 
-app.use(bodyParser.urlencoded({ extended: true }));
+app.use(express.urlencoded({ extended: true })); // use express's built-in middleware
+app.use(express.json()); // This is the middleware to handle JSON payloads
 
 app.use('/', routes);
 

peer-prep/src/matching-service/services/matchingService.js

@@ -3,6 +3,8 @@ const amqp = require('amqplib');
 const { v4: uuidv4 } = require('uuid');
 const { addMatchedPair, getCurrentMatchedPair } = require('../database/matchedPairDb');
 const MatchedPair = require('../models/matchedPairModel');
+const matchedPairDb = require('../database/matchedPairDb');
+
 
 const refreshDuration = 3000; // 3 seconds
 const waitingDuration = 3000;
@@ -14,6 +16,7 @@ let availabilityCache = new Set();
 
 // Find matching pair based on the selected criteria : language, proficiency, difficulty, topic
 async function findMatch(request) {
+
     return new Promise(async(resolve) => {
         let connection;
         let channel;
@@ -25,10 +28,10 @@ async function findMatch(request) {
 
             console.log('Successfully connected to RabbitMQ');
 
-            const criteria = `${request.language}
-                            .${request.proficiency}
-                            .${request.difficulty}
-                            .${request.topic}`;
+            const criteria = `${request.language || 'None'}
+                            .${request.proficiency || 'None'}
+                            .${request.difficulty || 'None'}
+                            .${request.topic || 'None'}`;
 
             checkCancel = setInterval(async() => {
                 if (isCancelled.has(parseInt(request.id))) {
@@ -94,6 +97,8 @@ async function findMatch(request) {
             }
         } catch (error) {
             console.log('Error finding match: ', error);
+            throw error;
+
         } finally {
             availabilityCache.delete(request.id);
 
@@ -107,6 +112,18 @@ async function findMatch(request) {
     });
 }
 
+function criteriaMatches(requestCriteria, currentCriteria) {
+    const fields = ['language', 'proficiency', 'difficulty', 'topic'];
+    for (let field of fields) {
+        if (requestCriteria[field] !== "None" &&
+            currentCriteria[field] !== "None" &&
+            requestCriteria[field] !== currentCriteria[field]) {
+            return false;
+        }
+    }
+    return true;
+}
+
 // Add new request into the queue, 'topic' exchange type is used to route the message
 async function addRequestIntoQueue(channel, criteria, request) {
     try {
@@ -167,29 +184,26 @@ async function listenToMatchingQueue(channel, criteria, request) {
             channel.consume(queueName, async(message) => {
                 const currentRequest = JSON.parse(message.content.toString());
                 const checkActivePair = await getCurrentMatchedPair(currentRequest.request.id);
-
-                if (checkActivePair &&
-                    (String(checkActivePair.id1) === String(request.id) ||
-                        String(checkActivePair.id2) === String(request.id))) {
-
+                
+                // Check if there is an active pair and if the criteria still match
+                if (checkActivePair && criteriaMatches(request, currentRequest.request)) {
+                    const collaboratorId = String(checkActivePair.id1) === String(request.id) ? checkActivePair.id2 : checkActivePair.id1;
                     resolve({
                         stored: true,
                         isMatched: true,
                         id: request.id,
-                        collaboratorId: currentRequest.request.id
+                        collaboratorId: collaboratorId
                     });
 
                 } else if (checkActivePair ||
                     isCancelled.has(parseInt(currentRequest.request.id))) {
 
                     console.log(`Remove match ${currentRequest.request.id}`);
-
                     availabilityCache.delete(currentRequest.request.id);
                     channel.ack(message);
 
                 } else if (!matched &&
-                    currentRequest.request.id !== request.id &&
-                    currentRequest.criteria === criteria &&
+                    currentRequest.request.id !== request.id && criteriaMatches(request, currentRequest.request) &&
                     availabilityCache.has(currentRequest.request.id)) {
 
                     console.log(`Found a match for ${request.id}`);
@@ -219,13 +233,42 @@ async function listenToMatchingQueue(channel, criteria, request) {
 
 // Cancel matching service
 
+//async function cancelMatch(requestId) {
+//    isCancelled.add(parseInt(requestId));
+//    availabilityCache.delete(requestId);
+//
+//    console.log(`Matching service is cancelled for ${requestId}`);
+
+//    return true;
+//}
+
 async function cancelMatch(requestId) {
+    // Adding the requestId to the cancelled set
     isCancelled.add(parseInt(requestId));
+    
+    // Removing the requestId from the availability cache
     availabilityCache.delete(requestId);
 
     console.log(`Matching service is cancelled for ${requestId}`);
 
+    // Check if there's an ongoing session for the given requestId
+    const currentMatchedPair = await matchedPairDb.getCurrentMatchedPair(requestId);
+    if (currentMatchedPair) {
+        console.log(`Found ongoing session for ${requestId}. Terminating...`);
+
+        try {
+            await matchedPairDb.endSession(currentMatchedPair.sessionId);
+            console.log(`Successfully terminated session for ${requestId}`);
+        } catch (error) {
+            console.error(`Error while terminating session for ${requestId}:`, error);
+            throw error;
+        }
+    } else {
+        console.log(`No ongoing session found for ${requestId}`);
+    }
+
     return true;
 }
 
+
 module.exports = { findMatch, cancelMatch };