[Don't Merge] DB Helper Functions

models/databasehelper.go

@@ -0,0 +1,76 @@
+package models
+
+import (
+	// "database/sql"
+	"errors"
+	"github.com/lib/pq"
+)
+
+// UniqueConstraintError is returned when a uniqueness constraint is violated during an insert.
+var UniqueConstraintError = errors.New("postgres: unique constraint violation")
+
+// QueryResultContainedMultipleRowsError is returned when a query unexpectedly returns more than one row.
+var QueryResultContainedMultipleRowsError = errors.New("query result unexpectedly contained multiple rows")
+
+// QueryResultContainedNoRowsError is returned when a query unexpectedly returns no rows.
+var QueryResultContainedNoRowsError = errors.New("query result unexpectedly contained no rows")
+
+func convertPostgresError(err error) error {
+	const uniqueConstraintErrorCode = "23505"
+
+	if postgresErr, ok := err.(*pq.Error); ok {
+		if postgresErr.Code == uniqueConstraintErrorCode {
+			return UniqueConstraintError
+		}
+	}
+
+	return err
+}
+
+func (db *DB) execOneResult(sqlQuery string, object interface{}, args ...interface{}) error {
+
+	rows, err := db.Query(sqlQuery, args...)
+	if err != nil {
+		return convertPostgresError(err)
+	}
+	defer rows.Close()
+
+	foundResult := false
+	for rows.Next() {
+
+		if foundResult {
+			return QueryResultContainedMultipleRowsError
+		}
+
+		if err := rows.Scan(object); err != nil {
+			return convertPostgresError(err)
+		}
+
+		foundResult = true
+	}
+
+	if !foundResult {
+		return QueryResultContainedNoRowsError
+	}
+
+	if err := rows.Err(); err != nil {
+		return convertPostgresError(err)
+	}
+
+	return nil
+}
+
+func (db *DB) execNoResults(sqlQuery string, args ...interface{}) (int64, error) {
+
+	res, err := db.Exec(sqlQuery, args...)
+	if err != nil {
+		return 0, convertPostgresError(err)
+	}
+
+	numAffected, err := res.RowsAffected()
+	if err != nil {
+		return 0, convertPostgresError(err)
+	}
+
+	return numAffected, nil
+}

models/datastore.go

@@ -2,20 +2,8 @@ package models
 
 import (
 	"database/sql"
-	"errors"
-
-	"github.com/lib/pq"
 )
 
-// UniqueConstraintError is returned when a uniqueness constraint is violated during an insert.
-var UniqueConstraintError = errors.New("postgres: unique constraint violation")
-
-// QueryResultContainedMultipleRowsError is returned when a query unexpectedly returns more than one row.
-var QueryResultContainedMultipleRowsError = errors.New("query result unexpectedly contained multiple rows")
-
-// QueryResultContainedNoRowsError is returned when a query unexpectedly returns no rows.
-var QueryResultContainedNoRowsError = errors.New("query result unexpectedly contained no rows")
-
 // ConnectToDatabase also pings the database to ensure a working connection.
 func ConnectToDatabase(databaseUrl string) (*DB, error) {
 	tempDb, err := sql.Open("postgres", databaseUrl)
@@ -41,15 +29,3 @@ type Datastore interface {
 type DB struct {
 	*sql.DB
 }
-
-func convertPostgresError(err error) error {
-	const uniqueConstraintErrorCode = "23505"
-
-	if postgresErr, ok := err.(*pq.Error); ok {
-		if postgresErr.Code == uniqueConstraintErrorCode {
-			return UniqueConstraintError
-		}
-	}
-
-	return err
-}

models/note.go

@@ -27,31 +27,9 @@ func (db *DB) StoreNewNote(
 		VALUES ($1, $2, $3)
 		RETURNING id`
 
-	rows, err := db.Query(sqlQuery, authorId, content, creationTime)
-	if err != nil {
-		return 0, convertPostgresError(err)
-	}
-	defer rows.Close()
-
 	var noteId int64 = 0
-	for rows.Next() {
-
-		if noteId != 0 {
-			return 0, QueryResultContainedMultipleRowsError
-		}
-
-		if err := rows.Scan(&noteId); err != nil {
-			return 0, convertPostgresError(err)
-		}
+	if err := db.execOneResult(sqlQuery, &noteId, authorId, content, creationTime); err != nil {
+		return 0, err
 	}
-
-	if noteId == 0 {
-		return 0, QueryResultContainedNoRowsError
-	}
-
-	if err := rows.Err(); err != nil {
-		return 0, convertPostgresError(err)
-	}
-
 	return NoteId(noteId), nil
 }

models/note_category.go

@@ -21,6 +21,7 @@ var categoryStrings = [...]string{
 }
 
 var CannotDeserializeNoteCategoryStringError = errors.New("String does not correspond to a Note Category")
+var NoteAlreadyContainsCategoryError = errors.New("NoteId already has a category stored for it")
 
 func DeserializeNoteCategory(input string) (NoteCategory, error) {
 	for i := 0; i < len(categoryStrings); i++ {
@@ -48,14 +49,11 @@ func (db *DB) StoreNewNoteCategoryRelationship(
 		INSERT INTO note_to_category_relationship (note_id, category)
 		VALUES ($1, $2)`
 
-	rows, err := db.Query(sqlQuery, int64(noteId), category.String())
-	if err != nil {
-		return convertPostgresError(err)
-	}
-	defer rows.Close()
-
-	if err := rows.Err(); err != nil {
-		return convertPostgresError(err)
+	if _, err := db.execNoResults(sqlQuery, int64(noteId), category.String()); err != nil {
+		if err == UniqueConstraintError {
+			return NoteAlreadyContainsCategoryError
+		}
+		return err
 	}
 
 	return nil

models/user.go

@@ -51,14 +51,12 @@ func (db *DB) StoreNewUser(
 		INSERT INTO app_user (display_name, email_address, password, creation_time)
 		VALUES ($1, $2, $3, $4)`
 
-	rows, err := db.Query(sqlQuery, displayName, emailAddress.String(), hashedPassword, creationTime)
-	if err != nil {
-		return convertPostgresError(err)
-	}
-	defer rows.Close()
+	if _, err := db.execNoResults(sqlQuery, displayName, emailAddress.String(), hashedPassword, creationTime); err != nil {
+		if err == UniqueConstraintError {
+			return EmailAddressAlreadyInUseError
+		}
 
-	if err := rows.Err(); err != nil {
-		return convertPostgresError(err)
+		return err
 	}
 
 	return nil
@@ -69,25 +67,10 @@ func (db *DB) AuthenticateUserCredentials(emailAddress *EmailAddress, password s
 		SELECT password FROM app_user
 		WHERE email_address = $1`
 
-	rows, err := db.Query(sqlQuery, emailAddress.String())
-	if err != nil {
-		return convertPostgresError(err)
-	}
-	defer rows.Close()
-
 	var storedHashedPassword []byte
-	for rows.Next() {
-		if storedHashedPassword != nil {
-			return QueryResultContainedMultipleRowsError
-		}
 
-		if err := rows.Scan(&storedHashedPassword); err != nil {
-			return err
-		}
-	}
-
-	if storedHashedPassword == nil {
-		return QueryResultContainedNoRowsError
+	if err := db.execOneResult(sqlQuery, &storedHashedPassword, emailAddress.String()); err != nil {
+		return err
 	}
 
 	if err := bcrypt.CompareHashAndPassword(
@@ -109,25 +92,12 @@ func (db *DB) GetIdForUserWithEmailAddress(emailAddress *EmailAddress) (UserId,
 		SELECT id FROM app_user
 		WHERE email_address = $1`
 
-	rows, err := db.Query(sqlQuery, emailAddress.String())
-	if err != nil {
-		return 0, convertPostgresError(err)
-	}
-	defer rows.Close()
-
 	var userId int64
-	for rows.Next() {
-		if userId != 0 {
-			return 0, QueryResultContainedMultipleRowsError
+	if err := db.execOneResult(sqlQuery, &userId, emailAddress.String()); err != nil {
+		if err == QueryResultContainedNoRowsError {
+			return 0, CredentialsNotAuthorizedError
 		}
-
-		if err := rows.Scan(&userId); err != nil {
-			return 0, err
-		}
-	}
-
-	if userId == 0 {
-		return 0, QueryResultContainedNoRowsError
+		return 0, err
 	}
 
 	return UserId(userId), nil