Improve comments and code readability

service/database/database.go

@@ -79,8 +79,11 @@ type AppDatabase interface {
 	Ping() error
 }
 
+// DBTransaction is the interface for a generic database transaction
 type DBTransaction interface {
+	// Commit commits the transaction
 	Commit() error
+	// Rollback rolls back the transaction
 	Rollback() error
 }
 
@@ -95,16 +98,17 @@ func New(db *sql.DB) (AppDatabase, error) {
 		return nil, errors.New("database is required when building a AppDatabase")
 	}
 
-	// Check if tables exist. If not, the database is empty, and we need to create the structure
+	// Check if some table exists. If not, the database is empty, and we need to create the structure
 	var tableName string
-	//todo: check for all the tables, not just users
+
 	err := db.QueryRow(`SELECT name FROM sqlite_master WHERE type='table' AND name='users';`).Scan(&tableName)
 	if errors.Is(err, sql.ErrNoRows) {
+		// Database is empty, let's create the structure
 		sqlStmt := `CREATE TABLE "users" (
 			"uid"	TEXT NOT NULL,
 			"name"	TEXT NOT NULL UNIQUE,
 			PRIMARY KEY("uid")
-		)` // todo: one query is enough! We are we doing a query per table?
+		)`
 		_, err = db.Exec(sqlStmt)
 		if err != nil {
 			return nil, fmt.Errorf("error creating database structure: %w", err)

service/database/db-likes.go

@@ -96,6 +96,7 @@ func (db *appdbimpl) UnlikePhoto(uid string, photo int64, liker_uid string) (Que
 	// But our DB implementation only requires the photo id.
 	exists, err := db.photoExists(uid, photo)
 	if err != nil || !exists {
+		// The photo does not exist, or the user has been banned
 		return ERR_NOT_FOUND, err
 	}
 
@@ -111,6 +112,7 @@ func (db *appdbimpl) UnlikePhoto(uid string, photo int64, liker_uid string) (Que
 		return ERR_INTERNAL, err
 	}
 
+	// The user was not liking the photo
 	if rows == 0 {
 		return ERR_NOT_FOUND, nil
 	}

service/database/db-photos.go

@@ -18,7 +18,6 @@ func (db *appdbimpl) PostPhoto(uid string) (DBTransaction, int64, error) {
 		err_rb := tx.Rollback()
 		// If rollback fails, we return the original error plus the rollback error
 		if err_rb != nil {
-			// todo: we are losing track of err_rb here
 			err = fmt.Errorf("Rollback error. Rollback cause: %w", err)
 		}
 
@@ -30,7 +29,6 @@ func (db *appdbimpl) PostPhoto(uid string) (DBTransaction, int64, error) {
 		err_rb := tx.Rollback()
 		// If rollback fails, we return the original error plus the rollback error
 		if err_rb != nil {
-			// todo: we are losing track of err_rb here
 			err = fmt.Errorf("Rollback error. Rollback cause: %w", err)
 		}
 
@@ -66,6 +64,7 @@ func (db *appdbimpl) photoExists(uid string, photo int64) (bool, error) {
 	return cnt > 0, nil
 }
 
+// Check if a given photo owned by a given user exists, and the requesting user is not banned by the author
 func (db *appdbimpl) PhotoExists(uid string, photo int64, requesting_uid string) (bool, error) {
 
 	var cnt int64

service/database/db-transactions.go

@@ -2,14 +2,17 @@ package database
 
 import "database/sql"
 
+// dbtransaction is a struct to represent an SQL transaction, it implements the DBTransaction interface
 type dbtransaction struct {
 	c *sql.Tx
 }
 
 func (tx *dbtransaction) Commit() error {
+	// Commit the SQL transaction
 	return tx.c.Commit()
 }
 
 func (tx *dbtransaction) Rollback() error {
+	// Rollback the SQL transaction
 	return tx.c.Rollback()
 }

service/database/db_errors/db-errors.go

@@ -2,7 +2,7 @@ package db_errors
 
 import "strings"
 
-// Returns true if the query result has no rows
+// Returns true if the error is a "no rows in result set" error
 func EmptySet(err error) bool {
 	if err == nil {
 		return false
@@ -10,6 +10,7 @@ func EmptySet(err error) bool {
 	return strings.Contains(err.Error(), "no rows in result set")
 }
 
+// Returns true if the error is a Unique constraint violation error
 func UniqueViolation(err error) bool {
 	if err == nil {
 		return false
@@ -17,6 +18,7 @@ func UniqueViolation(err error) bool {
 	return strings.Contains(err.Error(), "UNIQUE constraint failed")
 }
 
+// Returns true if the error is a Foreign Key constraint violation error
 func ForeignKeyViolation(err error) bool {
 	if err == nil {
 		return false

service/database/set-name.go

@@ -1,7 +0,0 @@
-package database
-
-// SetName is an example that shows you how to execute insert/update
-func (db *appdbimpl) SetName(name string) error {
-	_, err := db.c.Exec("INSERT INTO example_table (id, name) VALUES (1, ?)", name)
-	return err
-}