basic internal structure

internal/service/currency.go

@@ -0,0 +1,47 @@
+package service
+
+import (
+	"Portifolio/internal/model"
+	"database/sql"
+)
+
+func InsertCurrency(db *sql.DB, input model.CurrencyInput) (int, error) {
+	res, err := db.Exec(
+		`INSERT INTO currencies (code, name) VALUES (?, ?)`,
+		input.Code, input.Name,
+	)
+	if err != nil {
+		return 0, err
+	}
+	id, err := res.LastInsertId()
+	return int(id), err
+}
+
+func GetCurrencyByCode(db *sql.DB, code string) (*model.Currency, error) {
+	c := &model.Currency{}
+	err := db.QueryRow(
+		`SELECT id, code, name FROM currencies WHERE code = ?`, code,
+	).Scan(&c.ID, &c.Code, &c.Name)
+	if err == sql.ErrNoRows {
+		return nil, nil
+	}
+	return c, err
+}
+
+func GetAllCurrencies(db *sql.DB) ([]model.Currency, error) {
+	rows, err := db.Query(`SELECT id, code, name FROM currencies ORDER BY code`)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	var currencies []model.Currency
+	for rows.Next() {
+		var c model.Currency
+		if err := rows.Scan(&c.ID, &c.Code, &c.Name); err != nil {
+			return nil, err
+		}
+		currencies = append(currencies, c)
+	}
+	return currencies, rows.Err()
+}