add factory methods to make storages

- Implement new function `NewPostgres` for creating a Postgres database connection with proper error handling.
- Create `storage.go` file to manage database connections, supporting Sqlite, Postgres, and MySQL.
- Implement `prepareStoreURL` to determine the database type from the connection URL and handle connection string formatting.

app/storage/engine/engine.go

@@ -17,6 +17,7 @@ const (
 	Unknown  Type = ""
 	Sqlite   Type = "sqlite"
 	Postgres Type = "postgres"
+	Mysql    Type = "mysql"
 )
 
 // SQL is a wrapper for sqlx.DB with type.
@@ -31,14 +32,23 @@ type SQL struct {
 func NewSqlite(file, gid string) (*SQL, error) {
 	db, err := sqlx.Connect("sqlite", file)
 	if err != nil {
-		return &SQL{}, err
+		return &SQL{}, fmt.Errorf("failed to connect to sqlite: %w", err)
 	}
 	if err := setSqlitePragma(db); err != nil {
 		return &SQL{}, err
 	}
 	return &SQL{DB: *db, gid: gid, dbType: Sqlite}, nil
 }
 
+// NewPostgres creates a new postgres database
+func NewPostgres(ctx context.Context, connURL, gid string) (*SQL, error) {
+	db, err := sqlx.ConnectContext(ctx, "postgres", connURL)
+	if err != nil {
+		return &SQL{}, fmt.Errorf("failed to connect to postgres: %w", err)
+	}
+	return &SQL{DB: *db, gid: gid, dbType: Postgres}, nil
+}
+
 // GID returns the group id
 func (e *SQL) GID() string {
 	return e.gid

app/storage/storage.go

@@ -0,0 +1,67 @@
+package storage
+
+import (
+	"context"
+	"fmt"
+	"strings"
+
+	"github.com/umputun/tg-spam/app/storage/engine"
+)
+
+// New creates a new store based on the connection URL and the session duration.
+func New(ctx context.Context, connURL, gid string) (*engine.SQL, error) {
+	dbType, conn, err := prepareStoreURL(connURL)
+	if err != nil {
+		return nil, err
+	}
+
+	switch dbType {
+	case engine.Sqlite:
+		res, err := engine.NewSqlite(conn, gid)
+		if err != nil {
+			return nil, fmt.Errorf("failed to create sqlite engine: %w", err)
+		}
+		return res, nil
+	case engine.Postgres:
+		res, err := engine.NewPostgres(ctx, conn, gid)
+		if err != nil {
+			return nil, fmt.Errorf("failed to create postgres engine: %w", err)
+		}
+		return res, nil
+	default:
+		return nil, fmt.Errorf("unsupported database type in connection string")
+	}
+}
+
+// prepareStoreURL returns the type of the store based on the connection URL and the connection URL.
+// supported connection strings for psq, mysql and sqlite
+// returns the type of the store and the connection string to use with sqlx
+func prepareStoreURL(connURL string) (dbType engine.Type, conn string, err error) {
+	if strings.HasPrefix(connURL, "postgres://") {
+		return engine.Postgres, connURL, nil
+	}
+	if strings.Contains(connURL, "@tcp(") {
+		// check if parseTime=true is set in the connection string and add it if not
+		if !strings.Contains(connURL, "parseTime=true") {
+			if strings.Contains(connURL, "?") {
+				connURL += "&parseTime=true"
+			} else {
+				connURL += "?parseTime=true"
+			}
+		}
+		return engine.Mysql, connURL, nil
+	}
+	if strings.HasPrefix(connURL, "sqlite:/") || strings.HasPrefix(connURL, "sqlite3:/") ||
+		strings.HasSuffix(connURL, ".sqlite") || strings.HasSuffix(connURL, ".db") {
+		connURL = strings.Replace(connURL, "sqlite:/", "file:/", 1)
+		connURL = strings.Replace(connURL, "sqlite3:/", "file:/", 1)
+		return engine.Sqlite, connURL, nil
+	}
+
+	if connURL == "memory" || strings.Contains(connURL, ":memory:") ||
+		strings.HasPrefix(connURL, "memory://") || strings.HasPrefix(connURL, "mem://") {
+		return engine.Sqlite, ":memory:", nil
+	}
+
+	return engine.Unknown, "", fmt.Errorf("unsupported database type in connection string")
+}