Add courses aggregate endpoint to professor endpoint

api/controllers/professor.go

@@ -143,3 +143,133 @@ func ProfessorAll(c *gin.Context) {
 	// return result
 	c.JSON(http.StatusOK, responses.MultiProfessorResponse{Status: http.StatusOK, Message: "success", Data: professors})
 }
+
+// @Id professorCourseSearch
+// @Router /professor [get]
+// @Description "Returns all of the courses of all the professors matching the query's string-typed key-value pairs"
+// @Produce json
+// @Param first_name query string false "The professor's first name"
+// @Param last_name query string false "The professor's last name"
+// @Param titles query string false "One of the professor's title"
+// @Param email query string false "The professor's email address"
+// @Param phone_number query string false "The professor's phone number"
+// @Param office.building query string false "The building of the location of the professor's office"
+// @Param office.room query string false "The room of the location of the professor's office"
+// @Param office.map_uri query string false "A hyperlink to the UTD room locator of the professor's office"
+// @Param profile_uri query string false "A hyperlink pointing to the professor's official university profile"
+// @Param image_uri query string false "A link to the image used for the professor on the professor's official university profile"
+// @Param office_hours.start_date query string false "The start date of one of the office hours meetings of the professor"
+// @Param office_hours.end_date query string false "The end date of one of the office hours meetings of the professor"
+// @Param office_hours.meeting_days query string false "One of the days that one of the office hours meetings of the professor"
+// @Param office_hours.start_time query string false "The time one of the office hours meetings of the professor starts"
+// @Param office_hours.end_time query string false "The time one of the office hours meetings of the professor ends"
+// @Param office_hours.modality query string false "The modality of one of the office hours meetings of the professor"
+// @Param office_hours.location.building query string false "The building of one of the office hours meetings of the professor"
+// @Param office_hours.location.room query string false "The room of one of the office hours meetings of the professor"
+// @Param office_hours.location.map_uri query string false "A hyperlink to the UTD room locator of one of the office hours meetings of the professor"
+// @Param sections query string false "The _id of one of the sections the professor teaches"
+// @Success 200 {array} schema.Course "A list of Courses"
+func ProfessorCourseSearch() gin.HandlerFunc {
+	// Wrapper of professorCourse() with flag of Search
+	return func(c *gin.Context) {
+		professorCourse("Search", c)
+	}
+}
+
+// @Id professorCourseById
+// @Router /professor/{id} [get]
+// @Description "Returns all the courses taught by the professor with given ID"
+// @Produce json
+// @Param id path string true "ID of the professor to get"
+// @Success 200 {array} schema.Course "A list of courses"
+func ProfessorCourseById() gin.HandlerFunc {
+	// Essentially wrapper of professorCourse() with flag of ById
+	return func(c *gin.Context) {
+		professorCourse("ById", c)
+	}
+}
+
+// Get all of the courses of the professors depending on the type of flag
+func professorCourse(flag string, c *gin.Context) {
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+
+	var professorCourses []schema.Course // array of courses of the professors (or single professor with Id)
+	var professorQuery bson.M            // query filter the professor
+	var err error
+
+	defer cancel()
+
+	if flag == "Search" {
+		// if the flag is Search, filter professors based on query parameters
+		professorQuery, err = schema.FilterQuery[schema.Professor](c)
+		if err != nil {
+			c.JSON(http.StatusBadRequest, responses.ErrorResponse{Status: http.StatusBadRequest, Message: "schema validation error", Data: err.Error()})
+			return
+		}
+	} else if flag == "ById" {
+		// if the flag is ById, filter that single professor based on their _id
+		// parse the ObjectId
+		professorId := c.Param("id")
+		professorObjId, err := primitive.ObjectIDFromHex(professorId)
+		if err != nil {
+			log.WriteError(err)
+			c.JSON(http.StatusBadRequest, responses.ErrorResponse{Status: http.StatusBadRequest, Message: "error", Data: err.Error()})
+			return
+		}
+		professorQuery = bson.M{"_id": professorObjId}
+	} else {
+		// something wrong that messed up the server
+		c.JSON(http.StatusInternalServerError, responses.ErrorResponse{Status: http.StatusInternalServerError, Message: "error", Data: "Endpoint broken"})
+		return
+	}
+
+	// TODO: ASK QUESTION ABOUT THE OPTION LIMIT
+
+	// Pipeline to query the courses from the filtered professors (or a single professor)
+	professorCoursePipeline := mongo.Pipeline{
+		// filter the professors
+		bson.D{{Key: "$match", Value: professorQuery}},
+
+		// lookup the array of sections from sections collection
+		bson.D{{Key: "$lookup", Value: bson.D{
+			{Key: "from", Value: "sections"},
+			{Key: "localField", Value: "sections"},
+			{Key: "foreignField", Value: "_id"},
+			{Key: "as", Value: "sections"},
+		}}},
+
+		// project the courses referenced by each section in the array
+		bson.D{{Key: "$project", Value: bson.D{{Key: "courses", Value: "$sections.course_reference"}}}},
+
+		// lookup the array of courses from coures collection
+		bson.D{{Key: "$lookup", Value: bson.D{
+			{Key: "from", Value: "courses"},
+			{Key: "localField", Value: "courses"},
+			{Key: "foreignField", Value: "_id"},
+			{Key: "as", Value: "courses"},
+		}}},
+
+		// unwind the courses
+		bson.D{{Key: "$unwind", Value: bson.D{
+			{Key: "path", Value: "$courses"},
+			{Key: "preserveNullAndEmptyArrays", Value: true},
+		}}},
+
+		// replace the combination of ids and courses with the courses entirely
+		bson.D{{Key: "$replaceWith", Value: "$courses"}},
+	}
+
+	// Perform aggreration on the pipeline
+	cursor, err := professorCollection.Aggregate(ctx, professorCoursePipeline)
+	if err != nil {
+		// return the error with there's something wrong with the aggregation
+		log.WriteError(err)
+		c.JSON(http.StatusInternalServerError, responses.ErrorResponse{Status: http.StatusInternalServerError, Message: "error", Data: err.Error()})
+		return
+	}
+	// Parse the array of courses from these professors
+	if err = cursor.All(ctx, &professorCourses); err != nil {
+		panic(err)
+	}
+	c.JSON(http.StatusOK, responses.MultiCourseResponse{Status: http.StatusOK, Message: "success", Data: professorCourses})
+}

api/routes/professor.go

@@ -14,4 +14,8 @@ func ProfessorRoute(router *gin.Engine) {
 	professorGroup.GET("", controllers.ProfessorSearch)
 	professorGroup.GET(":id", controllers.ProfessorById)
 	professorGroup.GET("all", controllers.ProfessorAll)
+
+	// Endpoints to get the courses of the professors
+	professorGroup.GET("course", controllers.ProfessorCourseSearch())
+	professorGroup.GET(":id/course", controllers.ProfessorCourseById())
 }