Enable functionality to handle add and remove of entry from mongo

db/mongo.go

@@ -11,18 +11,98 @@ import (
 	"net"
 	"strconv"
 
-	"github.com/Prabhjot-Sethi/core/errors"
-
+	"go.mongodb.org/mongo-driver/bson"
 	"go.mongodb.org/mongo-driver/mongo"
 	"go.mongodb.org/mongo-driver/mongo/options"
 	"go.opentelemetry.io/contrib/instrumentation/go.mongodb.org/mongo-driver/mongo/otelmongo"
+
+	"github.com/Prabhjot-Sethi/core/errors"
 )
 
+type mongoCollection struct {
+	StoreCollection
+	parent  *mongoStore // handler for the parent mongo DB object
+	colName string      // name of the collection this collection object is working with
+	col     *mongo.Collection
+}
+
+// inserts one entry with given key and data to the collection
+// returns errors if entry already exists or if there is a connection
+// error with the database server
+func (c *mongoCollection) InsertOne(ctx context.Context, key interface{}, data interface{}) error {
+	if data == nil {
+		return errors.Wrap(errors.InvalidArgument, "db Insert error: No data to store")
+	}
+	if key == nil {
+		return errors.Wrap(errors.InvalidArgument, "db Insert error: No Key specified to store")
+	}
+
+	// convert data to bson document for transacting with mongo db library
+	marshaledData, err := bson.Marshal(data)
+	if err != nil {
+		// return if any error occured
+		return err
+	}
+
+	bd := bson.D{}
+	err = bson.Unmarshal(marshaledData, &bd)
+	if err != nil {
+		// return if any error occured
+		return err
+	}
+
+	// key is already nil checked
+	// set the primary key to specified key.
+	//
+	// TODO(prabhjot) check if we want to allow nil key at some point
+	// Typically mongodb allows inserts with key not specified
+	// where it auto allocates the key to random id
+	primKey := bson.E{
+		Key:   "_id", // set primary key
+		Value: key,
+	}
+	bd = append(bd, primKey)
+
+	_, err = c.col.InsertOne(ctx, bd)
+	if err != nil {
+		// TODO(prabhjot) we may need to identify and differentiate
+		// Already Exist error here.
+		return err
+	}
+	return nil
+}
+
+// remove one entry from the collection matching the given key
+func (c *mongoCollection) DeleteOne(ctx context.Context, key interface{}) error {
+	resp, err := c.col.DeleteOne(ctx, bson.M{"_id": key})
+	if err != nil {
+		// TODO(prabhjot) we may need to identify and differentiate
+		// Not found error here
+		return err
+	}
+	if resp.DeletedCount == 0 {
+		return errors.Wrap(errors.NotFound, "No Document found")
+	}
+
+	return nil
+}
+
 type mongoStore struct {
 	Store
 	db *mongo.Database
 }
 
+func (s *mongoStore) GetCollection(name string) StoreCollection {
+	handle := s.db.Collection(name)
+	c := &mongoCollection{
+		parent:  s,
+		colName: name,
+		col:     handle,
+	}
+
+	return c
+}
+
 type mongoClient struct {
 	StoreClient
 	client *mongo.Client
@@ -95,6 +175,13 @@ func (c *mongoClient) GetDataStore(dbName string) Store {
 	return mongoStore
 }
 
+// gets Mongo DB collection for given collection name
+// inside a database specified with db name
+func (c *mongoClient) GetCollection(dbName, col string) StoreCollection {
+	s := c.GetDataStore(dbName)
+	return s.GetCollection(col)
+}
+
 func (c *mongoClient) HealthCheck(ctx context.Context) error {
 	return c.client.Ping(ctx, nil)
 }

db/mongo_test.go

@@ -8,6 +8,14 @@ import (
 	"testing"
 )
 
+type MyKey struct {
+	Name string
+}
+
+type MyData struct {
+	Desc string
+}
+
 func Test_ClientConnection(t *testing.T) {
 	t.Run("Valid_Auth_Config", func(t *testing.T) {
 		config := &MongoConfig{
@@ -29,7 +37,30 @@ func Test_ClientConnection(t *testing.T) {
 			t.Errorf("failed to perform Health check with DB Error: %s", err)
 		}
 
-		_ = client.GetDataStore("test")
+		s := client.GetDataStore("test")
+
+		col := s.GetCollection("collection1")
+
+		key := &MyKey{
+			Name: "test-key",
+		}
+		data := &MyData{
+			Desc: "sample-description",
+		}
+		err = col.InsertOne(context.Background(), key, data)
+		if err != nil {
+			t.Errorf("failed to insert an entry to collection Error: %s", err)
+		}
+
+		err = col.DeleteOne(context.Background(), key)
+		if err != nil {
+			t.Errorf("failed to delete entry using key Error: %s", err)
+		}
+
+		err = col.DeleteOne(context.Background(), key)
+		if err == nil {
+			t.Errorf("attemptting delete on already deleted entry, but didn't receive expected error")
+		}
 	})
 
 	t.Run("InValid_Port", func(t *testing.T) {

db/store.go

@@ -10,13 +10,31 @@ import (
 	"context"
 )
 
+// interface definition for a collection in store
+type StoreCollection interface {
+	// insert one entry to the collection for the given key and data
+	InsertOne(ctx context.Context, key interface{}, data interface{}) error
+
+	// remove one entry from the collection matching the given key
+	DeleteOne(ctx context.Context, key interface{}) error
+}
+
+// interface definition for a store, responsible for holding group
+// of collections
 type Store interface {
+	// Gets collection corresponding to the collection name
+	GetCollection(col string) StoreCollection
 }
 
+// interface definition for Client corresponding to a store and
 type StoreClient interface {
 	// Get the Data Store interface given the client interface
 	GetDataStore(dbName string) Store
 
+	// Gets collection corresponding to the collection name inside
+	// the requested database name
+	GetCollection(dbName, col string) StoreCollection
+
 	// Health Check, if the Store is connectable and healthy
 	// returns the status of health of the server by means of
 	// error if error is nil the health of the DB store can be