Edit api/challenge/addchallenge

 const Challenge = require("../../models/challenge");
+const Session = require("../../models/session");
+const Participation = require("../../models/participation");
+const Group = require("../../models/group");
+const User = require('../../models/user');
+
 const Joi = require("joi");
 /*POST /api/challenge/getChallenge
 {
@@ -8,7 +13,7 @@ const Joi = require("joi");
 exports.getChallenge = async (ctx) => {
   try {
     const { challengeName } = ctx.request.body;
-    const challenge = await Challenge.findByChallengeName(challengeName);
+    const challenge = await Challenge.findByChallengeName(challengeName).select('-_id');
     if (!challenge) {
       ctx.status = 401;
       return;
@@ -53,7 +58,7 @@ exports.addChallenge = async (ctx) => {
   } = ctx.request.body;
 
   try {
-    const isChallengeExist = await Challenge.findByChallengeName(challengeName);
+    const isChallengeExist = await Challenge.findByChallengeName(challengeName).select('-_id');
 
     if (isChallengeExist) {
       ctx.status = 409;
@@ -68,11 +73,95 @@ exports.addChallenge = async (ctx) => {
     });
 
     await challenge.save();
+    
+    const newChallenge=await Challenge.findByChallengeName(challengeName);
+    const newChallenge_id=newChallenge._id;
+    const timeStep=Number(durationPerSession.slice(0,-1))
+    for(let s_date=startDate,e_date=s_date;s_date<endDate;){
+      if(durationPerSession[durationPerSession.length-1]==='d'){
+        e_date.setDate(s_date.getDate()+timeStep);
+      }
+      else if(durationPerSession[durationPerSession.length-1]==='w'){
+        e_date.setDate(s_date.getDate()+timeStep*7);
+      }
+      else if(durationPerSession[durationPerSession.length-1]==='m'){
+        e_date.setMonth(s_date.getMonth()+timeStep);
+      }
+      e_date.setMinutes(e_date.getMinutes()-1);
+      if(e_date>endDate){
+        break;
+      }
+      let status="";
+      if (s_date>new Date()){
+        status="enrolled";
+      }
+      else if (s_date<=new Date() && new Date() <= e_date){
+        status="progress";
+      }
+      else{
+        status="end";
+      }
+      const session=new Session({
+        challengeId:newChallenge_id,
+        sessionStartDate:s_date,
+        sessionEndDate:e_date,
+        status:status,
+      });
+      await session.save();
+      s_date=e_date;
+      s_date.setMinutes(s_date.getMinutes()+1);
+    }
     ctx.body = challenge();
   } catch (e) {
     ctx.throw(500, e);
   }
+};
+
+
+/* GET /api/challenge/list?status
+query string status can be in ['all','enrolled','progress','end']
+*/
+exports.list = async (ctx) => {
+  try{
+    const status = ctx.qs.status;
+    if (status!=='all'){
+      const challenges = await Challenge.find({status:status}).select('-_id');
+      ctx.body = challenges;
+    }
+    else {
+      const challenges = await Challenge.find({}).select('-_id');
+      ctx.body = challenges;
+    }
+  }
+  catch(e){
+    ctx.throw(500,e);
+  }
+};
+
+/* POST /api/challenge/participate
+{
+  username: 'username',
+  challengeName: 'challengename'
+}
+*/
+
+exports.participate=async (ctx)=>{
+  try{
   /*
-  TODO: How to handle group?
+  TODO: access token validation,
+  recommend:get username from access_token
   */
-};
+    const {username,challengeName}=ctx.body;
+    const challenge=await Challenge.findByChallengeName(challengeName);
+    const challenge_id=challenge._id;
+    const user=await User.findByUsername(username);
+    const user_id=user._id;
+    const newGroup=new Group({
+      members:[user_id],
+    });
+    newGroup.save();
+  }
+  catch(e){
+    ctx.throw(500,e);
+  }
+};
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