diff --git a/_data/bootcamps.json b/_data/bootcamps.json
index da806f1..c117ee8 100644
--- a/_data/bootcamps.json
+++ b/_data/bootcamps.json
@@ -12,8 +12,7 @@
     "housing": true,
     "jobAssistance": true,
     "jobGuarantee": false,
-    "acceptGi": true,
-    "averageCost": 10000
+    "acceptGi": true
   },
   {
     "_id": "5d713a66ec8f2b88b8f830b8",
@@ -28,8 +27,7 @@
     "housing": false,
     "jobAssistance": true,
     "jobGuarantee": false,
-    "acceptGi": true,
-    "averageCost": 12000
+    "acceptGi": true
   },
   {
     "_id": "5d725a037b292f5f8ceff787",
@@ -44,8 +42,7 @@
     "housing": false,
     "jobAssistance": false,
     "jobGuarantee": false,
-    "acceptGi": false,
-    "averageCost": 8000
+    "acceptGi": false
   },
   {
     "_id": "5d725a1b7b292f5f8ceff788",
@@ -65,7 +62,6 @@
     "housing": false,
     "jobAssistance": true,
     "jobGuarantee": true,
-    "acceptGi": true,
-    "averageCost": 5000
+    "acceptGi": true
   }
 ]
diff --git a/controllers/bootcamps.js b/controllers/bootcamps.js
index acf7a25..4fe6f27 100644
--- a/controllers/bootcamps.js
+++ b/controllers/bootcamps.js
@@ -1,9 +1,8 @@
-const geocider = require('../utils/geocoder');
 const Bootcamp = require('../models/Bootcamp');
 const ErrorResponse = require('../utils/errorResponse');
 const asyncHandler = require('../middleware/async');
 const geocoder = require('../utils/geocoder');
-const { remove } = require('../models/Bootcamp');
+const path = require('path'); //core node module
 
 /**
  * NOTES
@@ -44,7 +43,7 @@ exports.getBootcamps = asyncHandler(async (req, res, next) => {
     queryStr = queryStr.replace(/\b(gt|gte|lt|lte|in)\b/g, match => `$${match}`);
 
     // Finding resource
-    query = Bootcamp.find(JSON.parse(queryStr)); //queryString is a string, needs to be a JS object
+    query = Bootcamp.find(JSON.parse(queryStr)).populate('courses'); //queryString is a string, needs to be a JS object
 
     // Select Fields ie. ?select=name,description will return only name and description of all entries
     if (req.query.select) {
@@ -157,10 +156,16 @@ exports.updateBootcamp = asyncHandler(async (req, res, next) => {
 // @route DELETE /api/v1/bootcamps/:id
 // @access Private
 exports.deleteBootcamp = asyncHandler(async (req, res, next) => {
-    const bootcamp = await Bootcamp.findByIdAndDelete(req.params.id);
+    // const bootcamp = await Bootcamp.findByIdAndDelete(req.params.id); --> "findbyIdAndDelete" will not trigger the delete middleware in Bootcamp.js model
+    
+    // INSTEAD, 1. get the bootcamp
+    const bootcamp = await Bootcamp.findById(req.params.id);
 
     if (!bootcamp) return next(new ErrorResponse(`Bootcamp not found with id of ${req.params.id}`, 404));
 
+    // 2. this will trigger middleware
+    bootcamp.remove();
+
     res.status(200).json({success: true, data: {}});
 });
 
@@ -189,4 +194,49 @@ exports.getBootcampsInRadius = asyncHandler(async (req, res, next) => {
         count: bootcamps.length,
         data: bootcamps
     });
+});
+
+// @desc Upload a photo for bootcamp
+// @route PUT /api/v1/bootcamps/:id/photo
+// @access Private
+exports.bootcampPhotoUpload = asyncHandler(async (req, res, next) => {
+    
+    const bootcamp = await Bootcamp.findById(req.params.id);
+
+    if (!bootcamp) return next(new ErrorResponse(`Bootcamp not found with id of ${req.params.id}`, 404));
+
+    if (!req.files) return next(new ErrorResponse(`Please uoload file`, 400));
+
+    // console.log(req.files); --> see how file is sent by postman
+
+    const file = req.files.file;
+
+    // Make sure the image is a photo
+    if (!file.mimetype.startsWith('image')) {
+        return next(new ErrorResponse(`Please upload an image file`, 400));
+    }
+
+    // Check file size
+    if (file.size > process.env.MAX_FILE_UPLOAD) {
+        return next(new ErrorResponse(`Please upload an image less than ${process.env.MAX_FILE_UPLOAD}`, 400));
+    }
+
+    // Need to change file name (in case someone adds another photo with same name, it won't get overwritten)
+    file.name = `photo_${bootcamp._id}${path.parse(file.name).ext}`; // get extension of file name before changing it
+
+    //console.log(file.name);
+
+    file.mv(`${process.env.FILE_UPLOAD_PATH}/${file.name}`, async err => {
+        if (err){
+            console.error(err);
+            return next(new ErrorResponse(`Problem with file upload`, 500));
+        }
+
+        await Bootcamp.findByIdAndUpdate(req.params.id, { photo: file.name });
+
+        res.status(200).json({
+            success: true,
+            data: file.name
+        })
+    });
 });
\ No newline at end of file
diff --git a/controllers/courses.js b/controllers/courses.js
new file mode 100644
index 0000000..6fca544
--- /dev/null
+++ b/controllers/courses.js
@@ -0,0 +1,115 @@
+const Course = require('../models/Course');
+const Bootcamp = require('../models/Bootcamp');
+const ErrorResponse = require('../utils/errorResponse');
+const asyncHandler = require('../middleware/async');
+
+// @desc Get all courses
+// @route GET /api/v1/courses
+// @route GET /api/v1/bootcamps/:bootcampid/courses
+// @access Public
+
+exports.getCourses = asyncHandler(async (req, res, next) => {
+    let query;
+
+    if (req.params.bootcampId) {
+        query = Course.find({ bootcamp: req.params.bootcampId});
+    }
+    else {
+        query = Course.find().populate({ // populate the course's bootcamp field with the bootcamp name and description
+            path: 'bootcamp',
+            select: 'name description'
+        });
+    }
+
+    const courses = await query;
+
+    res.status(200).json({
+        success: true,
+        count: courses.length,
+        data: courses
+    });
+});
+
+// @desc Get single course by id
+// @route GET /api/v1/courses/:id
+// @access Public
+
+exports.getCourse = asyncHandler(async (req, res, next) => {
+   const course = await Course.findById(req.params.id).populate({
+       path: 'bootcamp',
+       select: 'name description'
+   });
+
+   if (!course) {
+       return next(new ErrorResponse(`No course with id of ${req.params.id}`), 404);
+   }
+
+    res.status(200).json({
+        success: true,
+        data: course
+    });
+});
+
+// @desc Add course
+// @route POST /api/v1/bootcamps/:bootcampid/courses
+// @access Private
+
+exports.addCourse = asyncHandler(async (req, res, next) => {
+    req.body.bootcamp = req.params.bootcampId; //req.body.bootcamp refers to the 'bootcamp' field in the Course model
+
+    const bootcamp = await Bootcamp.findById(req.params.bootcampId);
+ 
+    if (!bootcamp) {
+        return next(new ErrorResponse(`No bootcamp with id of ${req.params.bootcampId}`), 404);
+    }
+
+    const course = await Course.create(req.body);
+ 
+     res.status(200).json({
+         success: true,
+         data: course
+     });
+ });
+
+// @desc Update a course
+// @route PUT /api/v1/courses/:id
+// @access Private
+
+exports.updateCourse = asyncHandler(async (req, res, next) => {
+
+    let course = await Course.findById(req.params.id);
+ 
+    if (!course) {
+        return next(new ErrorResponse(`No course with id of ${req.params.id}`), 404);
+    }
+
+    course = await Course.findByIdAndUpdate(req.params.id, req.body, {
+        new: true,
+        runValidators: true
+    });
+
+     res.status(200).json({
+         success: true,
+         data: course
+     });
+ });
+
+ // @desc Delete a course
+// @route DELETE /api/v1/courses/:id
+// @access Private
+
+exports.deleteCourse = asyncHandler(async (req, res, next) => {
+
+    const course = await Course.findById(req.params.id);
+ 
+    if (!course) {
+        return next(new ErrorResponse(`No course with id of ${req.params.id}`), 404);
+    }
+
+    await course.remove(); // cannot use findByIdAndDelete due to course middleware
+
+     res.status(200).json({
+         success: true,
+         data: {}
+     });
+ });
\ No newline at end of file
diff --git a/models/Bootcamp.js b/models/Bootcamp.js
index 0ae1765..21d924e 100644
--- a/models/Bootcamp.js
+++ b/models/Bootcamp.js
@@ -99,6 +99,9 @@ const BootcampSchema = new mongoose.Schema({
         type: Date,
         default: Date.now
       }
+}, {
+  toJSON: { virtuals: true},
+  toObject: { virtuals: true }
 });
 
 /**
@@ -139,4 +142,24 @@ BootcampSchema.pre('save', async function(next) {
   next();
 });
 
+// Cascade delete courses when bootcamp is deleted (if bootcamp is deleted, delete all cooresponding courses)
+BootcampSchema.pre('remove', async function (next) {
+  console.log(`Courses are being removed from bootcamp ${this._id}`);
+
+  // Delete courses with bootcamp field = this._id (current bootcamp)
+      // Note: this must be "pre" middleware (if it were "post", since we are deleting the bootcamp, we would not be able to access "this" fields)
+  await this.model('Course').deleteMany({ bootcamp: this._id }); 
+  next();
+})
+
+// Reverse Populate with Virtuals (populate Bootcamp object with all courses it coresponds to)
+  // This creates a new field called 'courses' in Bootcamp model that holds all courses coresponding to bootcamp
+  // NOTE: this does NOT get saved on the DB
+BootcampSchema.virtual('courses', {
+  ref: 'Course',
+  localField: '_id',
+  foreignField: 'bootcamp', // field in the Course model that is tageted
+  justOne: false // need an array
+})
+
 module.exports = mongoose.model('Bootcamp', BootcampSchema);
\ No newline at end of file
diff --git a/models/Course.js b/models/Course.js
index 47a7a8d..8f7d35d 100644
--- a/models/Course.js
+++ b/models/Course.js
@@ -1,4 +1,5 @@
 const mongoose = require('mongoose');
+const Bootcamp = require('./Bootcamp');
 
 const CourseSchema = new mongoose.Schema({
     title: {
@@ -38,4 +39,45 @@ const CourseSchema = new mongoose.Schema({
     }
 });
 
+/**
+ * MONGOOSE MIDDLEWARE
+ */
+
+ // Static method to get avg of course tuitions (static method gets called on Model object)
+ //     NOTE: each bootcamp has an array of courses --> this function calculates the average cost of a particular bootcamp's courses
+
+ CourseSchema.statics.getAverageCost = async function(bootcampId) {
+    //console.log('Calculating avg cost... '.blue);
+
+    const obj = await this.aggregate([ // aggregate funciton called on entire Course model
+        {   
+            $match: { bootcamp: bootcampId }
+        },
+        {
+            $group: {
+                _id: '$bootcamp',
+                averageCost: { $avg: '$tuition' }
+            }
+        }
+    ]); // ie. console.log(obj) --> [ { _id: 5d725a1b7b292f5f8ceff788, averageCost: 11250 } ], where _id is id of a bootcamp
+
+    // Save averageCost to DB (at Bootcamp object)
+    try {
+        // get Bootcamp field from Course
+        await this.model('Bootcamp').findByIdAndUpdate(bootcampId, { averageCost: Math.ceil(obj[0].averageCost / 10) * 10 }); // log obj to understand
+    } catch (err) {
+        console.error(err);
+    }
+ }
+
+//Call getAverage Cost after save
+CourseSchema.post('save', function() {
+    this.constructor.getAverageCost(this.bootcamp);
+});
+
+// Call getAverageCost before remove
+CourseSchema.pre('remove', function() {
+    this.constructor.getAverageCost(this.bootcamp);
+});
+
 module.exports = mongoose.model('Course', CourseSchema);
\ No newline at end of file
diff --git a/package-lock.json b/package-lock.json
index cdf5a7f..e74079c 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -12,6 +12,7 @@
         "colors": "^1.4.0",
         "dotenv": "^8.2.0",
         "express": "^4.17.1",
+        "express-fileupload": "^1.2.1",
         "mongoose": "^5.11.14",
         "morgan": "^1.10.0",
         "node-geocoder": "^3.27.0",
@@ -352,6 +353,17 @@
         "node": ">=0.6.19"
       }
     },
+    "node_modules/busboy": {
+      "version": "0.3.1",
+      "resolved": "https://registry.npmjs.org/busboy/-/busboy-0.3.1.tgz",
+      "integrity": "sha512-y7tTxhGKXcyBxRKAni+awqx8uqaJKrSFSNFSeRG5CsWNdmy2BIK+6VGWEW7TZnIO/533mtMEA4rOevQV815YJw==",
+      "dependencies": {
+        "dicer": "0.3.0"
+      },
+      "engines": {
+        "node": ">=4.5.0"
+      }
+    },
     "node_modules/bytes": {
       "version": "3.1.0",
       "resolved": "https://registry.npmjs.org/bytes/-/bytes-3.1.0.tgz",
@@ -680,6 +692,17 @@
       "resolved": "https://registry.npmjs.org/destroy/-/destroy-1.0.4.tgz",
       "integrity": "sha1-l4hXRCxEdJ5CBmE+N5RiBYJqvYA="
     },
+    "node_modules/dicer": {
+      "version": "0.3.0",
+      "resolved": "https://registry.npmjs.org/dicer/-/dicer-0.3.0.tgz",
+      "integrity": "sha512-MdceRRWqltEG2dZqO769g27N/3PXfcKl04VhYnBlo2YhH7zPi88VebsjTKclaOyiuMaGU72hTfw3VkUitGcVCA==",
+      "dependencies": {
+        "streamsearch": "0.1.2"
+      },
+      "engines": {
+        "node": ">=4.5.0"
+      }
+    },
     "node_modules/dot-prop": {
       "version": "5.3.0",
       "resolved": "https://registry.npmjs.org/dot-prop/-/dot-prop-5.3.0.tgz",
@@ -805,6 +828,17 @@
         "node": ">= 0.10.0"
       }
     },
+    "node_modules/express-fileupload": {
+      "version": "1.2.1",
+      "resolved": "https://registry.npmjs.org/express-fileupload/-/express-fileupload-1.2.1.tgz",
+      "integrity": "sha512-fWPNAkBj+Azt9Itmcz/Reqdg3LeBfaXptDEev2JM8bCC0yDptglCnlizhf0YZauyU5X/g6v7v4Xxqhg8tmEfEA==",
+      "dependencies": {
+        "busboy": "^0.3.1"
+      },
+      "engines": {
+        "node": ">=8.0.0"
+      }
+    },
     "node_modules/extend": {
       "version": "3.0.2",
       "resolved": "https://registry.npmjs.org/extend/-/extend-3.0.2.tgz",
@@ -2225,6 +2259,14 @@
         "node": ">=0.10.0"
       }
     },
+    "node_modules/streamsearch": {
+      "version": "0.1.2",
+      "resolved": "https://registry.npmjs.org/streamsearch/-/streamsearch-0.1.2.tgz",
+      "integrity": "sha1-gIudDlb8Jz2Am6VzOOkpkZoanxo=",
+      "engines": {
+        "node": ">=0.8.0"
+      }
+    },
     "node_modules/string_decoder": {
       "version": "1.1.1",
       "resolved": "https://registry.npmjs.org/string_decoder/-/string_decoder-1.1.1.tgz",
@@ -2819,6 +2861,14 @@
       "resolved": "https://registry.npmjs.org/bson/-/bson-1.1.5.tgz",
       "integrity": "sha512-kDuEzldR21lHciPQAIulLs1LZlCXdLziXI6Mb/TDkwXhb//UORJNPXgcRs2CuO4H0DcMkpfT3/ySsP3unoZjBg=="
     },
+    "busboy": {
+      "version": "0.3.1",
+      "resolved": "https://registry.npmjs.org/busboy/-/busboy-0.3.1.tgz",
+      "integrity": "sha512-y7tTxhGKXcyBxRKAni+awqx8uqaJKrSFSNFSeRG5CsWNdmy2BIK+6VGWEW7TZnIO/533mtMEA4rOevQV815YJw==",
+      "requires": {
+        "dicer": "0.3.0"
+      }
+    },
     "bytes": {
       "version": "3.1.0",
       "resolved": "https://registry.npmjs.org/bytes/-/bytes-3.1.0.tgz",
@@ -3070,6 +3120,14 @@
       "resolved": "https://registry.npmjs.org/destroy/-/destroy-1.0.4.tgz",
       "integrity": "sha1-l4hXRCxEdJ5CBmE+N5RiBYJqvYA="
     },
+    "dicer": {
+      "version": "0.3.0",
+      "resolved": "https://registry.npmjs.org/dicer/-/dicer-0.3.0.tgz",
+      "integrity": "sha512-MdceRRWqltEG2dZqO769g27N/3PXfcKl04VhYnBlo2YhH7zPi88VebsjTKclaOyiuMaGU72hTfw3VkUitGcVCA==",
+      "requires": {
+        "streamsearch": "0.1.2"
+      }
+    },
     "dot-prop": {
       "version": "5.3.0",
       "resolved": "https://registry.npmjs.org/dot-prop/-/dot-prop-5.3.0.tgz",
@@ -3177,6 +3235,14 @@
         "vary": "~1.1.2"
       }
     },
+    "express-fileupload": {
+      "version": "1.2.1",
+      "resolved": "https://registry.npmjs.org/express-fileupload/-/express-fileupload-1.2.1.tgz",
+      "integrity": "sha512-fWPNAkBj+Azt9Itmcz/Reqdg3LeBfaXptDEev2JM8bCC0yDptglCnlizhf0YZauyU5X/g6v7v4Xxqhg8tmEfEA==",
+      "requires": {
+        "busboy": "^0.3.1"
+      }
+    },
     "extend": {
       "version": "3.0.2",
       "resolved": "https://registry.npmjs.org/extend/-/extend-3.0.2.tgz",
@@ -4259,6 +4325,11 @@
       "resolved": "https://registry.npmjs.org/stealthy-require/-/stealthy-require-1.1.1.tgz",
       "integrity": "sha1-NbCYdbT/SfJqd35QmzCQoyJr8ks="
     },
+    "streamsearch": {
+      "version": "0.1.2",
+      "resolved": "https://registry.npmjs.org/streamsearch/-/streamsearch-0.1.2.tgz",
+      "integrity": "sha1-gIudDlb8Jz2Am6VzOOkpkZoanxo="
+    },
     "string_decoder": {
       "version": "1.1.1",
       "resolved": "https://registry.npmjs.org/string_decoder/-/string_decoder-1.1.1.tgz",
diff --git a/package.json b/package.json
index e0f778c..216d657 100644
--- a/package.json
+++ b/package.json
@@ -21,6 +21,7 @@
     "colors": "^1.4.0",
     "dotenv": "^8.2.0",
     "express": "^4.17.1",
+    "express-fileupload": "^1.2.1",
     "mongoose": "^5.11.14",
     "morgan": "^1.10.0",
     "node-geocoder": "^3.27.0",
diff --git a/public/uploads/photo_5d725a1b7b292f5f8ceff788.jpg b/public/uploads/photo_5d725a1b7b292f5f8ceff788.jpg
new file mode 100644
index 0000000..b2cf399
Binary files /dev/null and b/public/uploads/photo_5d725a1b7b292f5f8ceff788.jpg differ
diff --git a/routes/bootcamps.js b/routes/bootcamps.js
index 93889a2..9eb602c 100644
--- a/routes/bootcamps.js
+++ b/routes/bootcamps.js
@@ -1,6 +1,16 @@
 const express = require('express');
 
-const router = express.Router(); // allows api routes to be in different file than server.js
+// allows api routes to be in different file than server.js
+const router = express.Router();
+
+//Include other resource routers
+const courseRouter = require('./courses');
+
+// Re-route to other resource routers
+    // if this route is hit, will continue on to './courses' which will call the appropriate route
+    // allows re-routing so that no need to import 'getCourses' route in this file
+router.use('/:bootcampId/courses', courseRouter);
+
 
 // Notes: if APIs were in this file
     // 1. Replace "app.xxx" with "router.xxx"
@@ -13,9 +23,11 @@ const router = express.Router(); // allows api routes to be in different file th
 
 // However, API logic will be in a middleware file (see ./controllers/bootcamps.js)
     //1. bring in API names from '../controller/bootcamps
-    const { getBootcamps, getBootcamp, createBootcamp, updateBootcamp, deleteBootcamp, getBootcampsInRadius } = require('../controllers/bootcamps')
-    //2. 
+    const { getBootcamps, getBootcamp, createBootcamp, updateBootcamp, deleteBootcamp, getBootcampsInRadius, bootcampPhotoUpload } = require('../controllers/bootcamps')
+
+    // 2. 
     router.route('/radius/:zipcode/:distance').get(getBootcampsInRadius);
+    router.route('/:id/photo').put(bootcampPhotoUpload);
     router.route('/').get(getBootcamps).post(createBootcamp);
     router.route('/:id').get(getBootcamp).put(updateBootcamp).delete(deleteBootcamp);
 
diff --git a/routes/courses.js b/routes/courses.js
new file mode 100644
index 0000000..f0548ab
--- /dev/null
+++ b/routes/courses.js
@@ -0,0 +1,11 @@
+const express = require('express');
+
+const { getCourses, getCourse, addCourse, updateCourse, deleteCourse } = require('../controllers/courses');
+const { deleteMany } = require('../models/Course');
+
+const router = express.Router({ mergeParams: true }); // mergeParams used for re-routing from bootcamps routes to courses routes
+
+router.route('/').get(getCourses).post(addCourse);
+router.route('/:id').get(getCourse).put(updateCourse).delete(deleteCourse);
+
+module.exports = router;
\ No newline at end of file
diff --git a/server.js b/server.js
index fbd218d..87cb5c2 100644
--- a/server.js
+++ b/server.js
@@ -2,7 +2,9 @@ const express = require('express');
 const dotenv = require('dotenv');
 const morgan = require('morgan');
 const connectDB = require('./config/db');
+const fileupload = require('express-fileupload');
 const colors = require('colors');
+const path = require('path');
 
 // Middlwares
 const errorHandler = require('./middleware/error');
@@ -50,6 +52,7 @@ connectDB();
 
 // Import route files
 const bootcamps = require('./routes/bootcamps');
+const courses = require('./routes/courses');
 
 const app = express();
 
@@ -61,8 +64,15 @@ if (process.env.NODE_ENV === 'development'){
     app.use(morgan('dev'));
 }
 
+// File Uploading
+app.use(fileupload());
+
+// Set 'public' filder as static
+app.use(express.static(path.join(__dirname, 'public')));
+
 // Mount routers (from bootcamps file)
 app.use('/api/v1/bootcamps', bootcamps);
+app.use('/api/v1/courses', courses);
 
 app.use(errorHandler);