Convert db backend to use Gorm, with basis for support

for Mysql and Postgres in addition to existing Sqlite

backend/internal/database/db.go

@@ -0,0 +1,80 @@
+package database
+
+import (
+	"fmt"
+	"strings"
+
+	"npm/internal/config"
+	"npm/internal/logger"
+
+	"github.com/glebarez/sqlite"
+	"github.com/rotisserie/eris"
+	"gorm.io/driver/mysql"
+	"gorm.io/driver/postgres"
+	"gorm.io/gorm"
+	"gorm.io/gorm/schema"
+)
+
+var dbInstance *gorm.DB
+
+// NewDB creates a new connection
+func NewDB() {
+	logger.Info("Creating new DB instance using %s", strings.ToLower(config.Configuration.DB.Driver))
+	db, err := connect()
+	if err != nil {
+		logger.Error("DatabaseConnectError", err)
+	} else if db != nil {
+		dbInstance = db
+	}
+}
+
+// GetDB returns an existing or new instance
+func GetDB() *gorm.DB {
+	if dbInstance == nil {
+		NewDB()
+	}
+	return dbInstance
+}
+
+func connect() (*gorm.DB, error) {
+	var d gorm.Dialector
+	dsn := config.Configuration.DB.GetGormConnectURL()
+	switch strings.ToLower(config.Configuration.DB.Driver) {
+
+	case config.DatabaseSqlite:
+		// autocreate(dsn)
+		d = sqlite.Open(dsn)
+
+	case config.DatabasePostgres:
+		d = postgres.Open(dsn)
+
+	case config.DatabaseMysql:
+		d = mysql.Open(dsn)
+
+	default:
+		return nil, eris.New(fmt.Sprintf("Database driver %s is not supported. Valid options are: %s, %s or %s", config.Configuration.DB.Driver, config.DatabaseSqlite, config.DatabasePostgres, config.DatabaseMysql))
+	}
+
+	return gorm.Open(d, &gorm.Config{
+		// see: https://gorm.io/docs/gorm_config.html
+		NamingStrategy: schema.NamingStrategy{
+			SingularTable: true,
+			NoLowerCase:   true,
+		},
+		PrepareStmt: false,
+	})
+}
+
+/*
+func autocreate(dbFile string) {
+	if _, err := os.Stat(dbFile); os.IsNotExist(err) {
+		// Create it
+		logger.Info("Creating Sqlite DB: %s", dbFile)
+		// nolint: gosec
+		_, err = os.Create(dbFile)
+		if err != nil {
+			logger.Error("FileCreateError", err)
+		}
+	}
+}
+*/