Merge pull request #4 from CS3219-AY2425S1/question-page

Add Question List Page

Author: alvinlim277

backend/.gitignore

@@ -0,0 +1,2 @@
+questionDB.env
+log

backend/common/logger_struct.go

@@ -0,0 +1,14 @@
+package common
+
+import (
+	"github.com/sirupsen/logrus"
+)
+
+//contains the logger
+type Logger struct {
+	Log *logrus.Logger
+}
+
+func NewLogger(logger *logrus.Logger) *Logger {
+	return &Logger{Log: logger}
+}

backend/common/question_struct.go

@@ -0,0 +1,22 @@
+// defines the JSON format of quesitons.
+package common
+
+type Difficulty int 
+
+const (
+	Easy Difficulty = 1
+	Medium Difficulty = 2
+	Hard Difficulty = 3
+)
+
+// Question struct
+type Question struct {
+	ID         int       `json:"id"`
+	Difficulty Difficulty `json:"difficulty"`
+	Title 	string    `json:"title"`
+	Description string `json:"description"`
+	Categories []string `json:"categories"`
+	TestCases map[string]string `json:"test_cases"`
+	//Images []string `json:"images"` // for future uses
+}
+

backend/database/database_interactions.go

@@ -0,0 +1,84 @@
+// contains the database-related functions for the questions API.
+package database
+
+import (
+	"context"
+	"errors"
+	"net/http"
+	"fmt"
+
+	"go.mongodb.org/mongo-driver/bson"
+	"go.mongodb.org/mongo-driver/mongo/options"
+	"peerprep/common"
+)
+
+func (db *QuestionDB) GetAllQuestionsWithQuery(logger *common.Logger, filter bson.D) ([]common.Question, error) {
+	questionCursor, err := db.questions.Find(context.Background(), filter)
+
+	if err != nil {
+		logger.Log.Error("Error retrieving questions: ", err.Error())
+		return nil, err
+	}
+
+	var questions []common.Question
+
+	if err = questionCursor.All(context.Background(), &questions); err != nil {
+		logger.Log.Error("Error decoding questions: ", err.Error())
+		return nil, err
+	}
+
+	return questions, nil
+}
+
+func (db *QuestionDB) AddQuestion(logger *common.Logger, question *common.Question) (int, error) {
+	if db.QuestionExists(question) {
+		logger.Log.Warn("Cannot add question: question already exists")
+		return http.StatusConflict, errors.New("question already exists")
+	}
+
+	question.ID = db.FindNextQuestionId()
+
+	if question.ID == -1 {
+		logger.Log.Error("Could not find next question ID")
+		return http.StatusBadGateway, errors.New("could not find the next question ID")
+	}
+
+	if _, err := db.questions.InsertOne(context.Background(), question); err != nil {
+		logger.Log.Error("Error adding question", err.Error())
+		return http.StatusBadGateway, err
+	}
+
+	db.IncrementNextQuestionId(question.ID + 1, logger)
+	return http.StatusOK, nil
+}
+
+func (db *QuestionDB) UpsertQuestion(logger *common.Logger, question *common.Question) (int, error) {
+
+	filter := bson.D{bson.E{Key: "id", Value: question.ID}}
+	setter := bson.M{"$set": question}
+	upsert := options.Update().SetUpsert(true)
+	
+	_, err := db.questions.UpdateOne(context.Background(), filter, setter, upsert)
+
+	if err != nil {
+		logger.Log.Error("Error while upserting question", err.Error())
+		return http.StatusBadGateway, err
+	}
+
+	return http.StatusOK, nil
+}
+
+func (db *QuestionDB) DeleteQuestion(logger *common.Logger, id int) (int, error) {
+	deleteStatus, err := db.questions.DeleteOne(context.Background(), bson.D{bson.E{Key: "id", Value: id}})
+
+	if err != nil {
+		logger.Log.Error("Error deleting question", err.Error())
+		return http.StatusBadGateway, err
+	} else if deleteStatus.DeletedCount == 0 {
+		msg := fmt.Sprintf("Question with ID %d not found when deleting question", id)
+		logger.Log.Warn(msg)
+		return http.StatusNotFound, errors.New(msg)
+	}
+
+	return http.StatusNoContent, nil
+}

backend/database/database_util.go

@@ -0,0 +1,51 @@
+// utility functions for questions api
+package database
+
+import (
+	"context"
+	"fmt"
+
+	"go.mongodb.org/mongo-driver/bson"
+	"peerprep/common"
+)
+
+// used to check if a question already exists in the database.
+func (db *QuestionDB) QuestionExists(question *common.Question) bool {
+	filter := bson.D{bson.E{Key: "title", Value: question.Title}}
+	err := db.questions.FindOne(context.Background(), filter).Decode(&common.Question{}) //FindOne() returns error if no document is found
+	return err == nil
+}
+
+// used to find the next question ID to be used. Similar to SERIAL in psql.
+func (db *QuestionDB) FindNextQuestionId() int {
+	id := struct {
+		Next int `json:"next"`
+	}{}
+	filter := bson.D{}
+
+	if err := db.nextId.FindOne(context.Background(), filter).Decode(&id); err != nil {
+		return -1
+	}
+
+	return id.Next
+}
+
+// used to increment the next question ID to be used.
+// since the collection is capped at one document, inserting a new document will replace the old one.
+func (db *QuestionDB) IncrementNextQuestionId(nextId int, logger *common.Logger) {
+	var err error
+	if _, err = db.nextId.InsertOne(context.Background(), bson.D{bson.E{Key: "next", Value: nextId}}); err != nil {
+		logger.Log.Error("Error incrementing next question ID: ", err)
+		return
+	}
+
+	logger.Log.Info(fmt.Sprintf("Next question ID incremented to %d successfully", nextId))
+}
+
+// used to check if a question being replaced will cause duplicates in the database
+
+func (db *QuestionDB) QuestionExistsExceptId(question *common.Question) bool {
+	filter := bson.D{bson.E{Key: "title", Value: question.Title}, bson.E{Key: "id", Value: bson.D{bson.E{Key: "$ne", Value: question.ID}}}}
+	err := db.questions.FindOne(context.Background(), filter).Decode(&common.Question{}) //FindOne() returns error if no document is found
+	return err == nil
+}

backend/database/initialise_database.go

@@ -0,0 +1,45 @@
+// this is used to initialise the database connection
+package database
+
+import (
+	"context"
+	"log"
+	"os"
+
+	"github.com/joho/godotenv"
+	"go.mongodb.org/mongo-driver/mongo"
+	"go.mongodb.org/mongo-driver/mongo/options"
+)
+
+func InitialiseDB() (*mongo.Client, error) {
+	// Load environment variables
+	err := godotenv.Load("questionDB.env")
+
+	if err != nil {
+		log.Fatal("Error loading environment variables: " + err.Error())
+	}
+
+	mongoURI := os.Getenv("MONGODB_URI")
+
+	if mongoURI == "" {
+		log.Fatal("MONGODB_URI not set in environment variables")
+	}
+
+	clientOptions := options.Client().ApplyURI(mongoURI)
+
+	// Connect to MongoDB
+	server, err := mongo.Connect(context.Background(), clientOptions)
+
+	if err != nil {
+		log.Fatal("Error connecting to MongoDB" + err.Error())
+	}
+
+	// Check the connection
+	err = server.Ping(context.Background(), nil)
+
+	if err != nil {
+		return nil, err
+	}
+
+	return server, nil
+}

backend/database/questionDB_struct.go

@@ -0,0 +1,20 @@
+package database
+
+import (
+	"go.mongodb.org/mongo-driver/mongo"
+)
+
+// QuestionDB is a struct that contains a pointer to a mongo client.
+// questions is the collection with all the questions, nextId is a single-entry collection that stores the next ID to be used.
+type QuestionDB struct {
+	questions *mongo.Collection
+	nextId 	  *mongo.Collection
+}
+
+// returns a pointer to an instance of the Question collection
+func NewQuestionDB(client *mongo.Client) *QuestionDB {
+
+	questionCollection := client.Database("questions").Collection("questions")
+	idCollection := client.Database("questions").Collection("id")
+	return &QuestionDB{questions: questionCollection, nextId: idCollection}
+}

backend/go.mod

@@ -0,0 +1,47 @@
+module peerprep
+
+go 1.20
+
+require github.com/joho/godotenv v1.5.1 // indirect  -allows to load environment variables from a .env file instead of hardcoding them in the code
+
+require (
+	github.com/bytedance/sonic v1.11.6 // indirect
+	github.com/bytedance/sonic/loader v0.1.1 // indirect
+	github.com/cloudwego/base64x v0.1.4 // indirect
+	github.com/cloudwego/iasm v0.2.0 // indirect
+	github.com/gabriel-vasile/mimetype v1.4.3 // indirect
+	github.com/gin-contrib/sse v0.1.0 // indirect
+	github.com/gin-gonic/gin v1.10.0 // indirect
+	github.com/go-playground/locales v0.14.1 // indirect
+	github.com/go-playground/universal-translator v0.18.1 // indirect
+	github.com/go-playground/validator/v10 v10.20.0 // indirect
+	github.com/goccy/go-json v0.10.2 // indirect
+	github.com/golang/snappy v0.0.4 // indirect
+	github.com/json-iterator/go v1.1.12 // indirect
+	github.com/klauspost/compress v1.13.6 // indirect
+	github.com/klauspost/cpuid/v2 v2.2.7 // indirect
+	github.com/leodido/go-urn v1.4.0 // indirect
+	github.com/mattn/go-isatty v0.0.20 // indirect
+	github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect
+	github.com/modern-go/reflect2 v1.0.2 // indirect
+	github.com/montanaflynn/stats v0.7.1 // indirect
+	github.com/pelletier/go-toml/v2 v2.2.2 // indirect
+	github.com/sirupsen/logrus v1.9.3 // indirect    - Logging library
+	github.com/twitchyliquid64/golang-asm v0.15.1 // indirect
+	github.com/ugorji/go/codec v1.2.12 // indirect
+	github.com/xdg-go/pbkdf2 v1.0.0 // indirect
+	github.com/xdg-go/scram v1.1.2 // indirect
+	github.com/xdg-go/stringprep v1.0.4 // indirect
+	github.com/youmark/pkcs8 v0.0.0-20181117223130-1be2e3e5546d // indirect
+	go.mongodb.org/mongo-driver v1.16.1 // indirect
+	golang.org/x/arch v0.8.0 // indirect
+	golang.org/x/crypto v0.23.0 // indirect
+	golang.org/x/net v0.25.0 // indirect
+	golang.org/x/sync v0.7.0 // indirect
+	golang.org/x/sys v0.20.0 // indirect
+	golang.org/x/text v0.15.0 // indirect
+	google.golang.org/protobuf v1.34.1 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)
+
+require github.com/gin-contrib/cors v1.7.2 // indirect