Implement problem recommendation algorithm

@@ -3,5 +3,6 @@ const session = new Router();
 const sessionCtrl = require('./session.ctrl');
 
 session.post("/createproblem/:how",sessionCtrl.createProblem);
+session.get("/status",sessionCtrl.status);
 
 module.exports = session;
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+const axios = require("axios");
 const Participation = require("../../models/participation");
 const Session = require("../../models/session");
 const Group = require("../../models/group");
 const User = require("../../models/user");
+const Challenge = require("../../models/challenge");
+const Problem = require("../../models/problem");
 const mongoose = require("mongoose");
 
 const {ObjectId} = mongoose.Types;
 
 /* POST /api/session/createproblem/:how
 {   
-    sessionId: ObjectId,
-    groupId: ObjectId,
-    problemList:[Number],
+    sessionId: ObjectId or String,
+    groupId: ObjectId or String,
+    problemList:[Number], (optional)
 }
 */
 exports.createProblem = async (ctx)=>{
@@ -25,15 +28,20 @@ exports.createProblem = async (ctx)=>{
         if(typeof(problemList)==='string'){
             problemList=JSON.parse(problemList);
         }
+        const session = await Session.findById(sessionId);
+        const challengeId = session['challengeId'];
+        const challenge = await Challenge.findById(challengeId);
+        const goalPerSession = challenge['goalPerSession'];
         const participation = await Participation.findOne({sessionId:sessionId,groupId:groupId});
         const group = await Group.findById(groupId);
         const how=ctx.params.how;
         if(how==='self'){
+            if(problemList.length!==goalPerSession){
+                ctx.throw(400,'문제 수가 맞지 않습니다.');
+            }
             let check = true;
             for(let i=0;i<group.members.length;i++){
                 const user = await User.findById(group.members[i]);
-                console.log(user);
-                console.log(typeof(user.solvedBJ_date.solvedBJbyDATE));
                 let userProblemList = [];
                 for(let key in user.solvedBJ_date.solvedBJbyDATE){
                     userProblemList.push(user.solvedBJ_date.solvedBJbyDATE[key]);
@@ -47,7 +55,7 @@ exports.createProblem = async (ctx)=>{
                 }
             }
             if(!check){
-                ctx.throw('그룹원이 이미 푼 문제는 등록할 수 없습니다.');
+                ctx.throw(400,'그룹원이 이미 푼 문제는 등록할 수 없습니다.');
                 return;
             }
             else{
@@ -56,10 +64,72 @@ exports.createProblem = async (ctx)=>{
             }
         }
         else if(how==='recommend'){
-            //TODO
+            let groupProblemList=[];
+            let selectedProblemList=[];
+            for(let i=0;i<group.members.length;i++){
+                const user = await User.findById(group.members[i]);
+                for(let key in user.solvedBJ_date.solvedBJbyDATE){
+                    groupProblemList.push(user.solvedBJ_date.solvedBJbyDATE[key]);
+                }
+            }
+            groupProblemList=groupProblemList.flat().sort((a,b)=>new Date(b.solvedDate)-new Date(a.solvedDate)).map(elem=>elem.problem_number);
+            groupProblemList=groupProblemList.filter((x,i)=>groupProblemList.indexOf(x)===i);
+            console.log(groupProblemList);
+            const problems=await Problem.find({}).sort({count:-1});
+            console.log(problems);
+            console.log(goalPerSession);
+            for(let i=0;i<problems.length;i++){
+                if(!groupProblemList.includes(String(problems[i].problemNum))){
+                    selectedProblemList.push(String(problems[i].problemNum));
+                }
+                if(selectedProblemList.length===goalPerSession || i/problems.length >= 0.75){
+                    break;
+                }
+            }
+            for(let i=0; i<groupProblemList.length && selectedProblemList.length < goalPerSession; i++){
+                const p = await Problem.findOne({problemNum:groupProblemList[i]});
+                if( Number(p.solvedacLevel)< 1 || Number(p.solvedacLevel)>30 ){
+                    continue;
+                }
+                const body = await axios.get(`https://api.solved.ac/v2/search/problems.json?query=solvable:true+tier:${p.solvedacLevel}&page=1&sort=solved&sort_direction=desc`);
+                let data = body.data;
+                if(typeof(data)==='string'){
+                    data=JSON.parse(data);
+                }
+                for(let j=0;j<data.result.problems.length;j++){
+                    if(!groupProblemList.includes(data.result.problems[j].id)){
+                        selectedProblemList.push(data.result.problems[j].id.toString());
+                        break;
+                    }
+                }
+            }
+            selectedProblemList.map(async problemNum=>await participation.addProblem({problemNum:problemNum,isSolved:false}));
+            ctx.body=participation.serialize(); 
         }
     }
     catch(e){
+        console.error(e);
         ctx.throw(500,e);
     }
 };
+
+
+// GET /api/session/status?sessionId&groupId
+
+exports.status=async (ctx)=>{
+    try{
+        let {sessionId,groupId}=ctx.request.query;
+        if(typeof(sessionId)==='string'){
+            sessionId=new ObjectId(sessionId);
+        }
+        if(typeof(groupId)==='string'){
+            groupId=new ObjectId(groupId);
+        }
+        const participation=await Participation.findOne({sessionId:sessionId,groupId:groupId});
+        const group = await Group.findById(groupId);
+        
+    }
+    catch(e){
+        ctx.throw(500,e);
+    }
+}
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