Refactor codebase for Phase 3

internal/dbutil/mysql.go

@@ -0,0 +1,68 @@
+package dbutil
+
+import (
+	"database/sql"
+	"errors"
+	"fmt"
+	"strings"
+
+	"github.com/go-sql-driver/mysql"
+)
+
+func OpenMySQLAndCreateDatabaseIfMissing(dsn string) (*sql.DB, error) {
+	db, err := sql.Open("mysql", dsn)
+	if err != nil {
+		return nil, err
+	}
+	if err := db.Ping(); err == nil {
+		return db, nil
+	} else {
+		_ = db.Close()
+		var mysqlErr *mysql.MySQLError
+		if !errors.As(err, &mysqlErr) || mysqlErr.Number != 1049 {
+			return nil, err
+		}
+	}
+
+	cfg, err := mysql.ParseDSN(dsn)
+	if err != nil {
+		return nil, err
+	}
+	if cfg.DBName == "" {
+		return nil, errors.New("DSN does not include a database name")
+	}
+	databaseName := cfg.DBName
+	cfg.DBName = ""
+
+	adminDB, err := sql.Open("mysql", cfg.FormatDSN())
+	if err != nil {
+		return nil, err
+	}
+	defer adminDB.Close()
+	if err := adminDB.Ping(); err != nil {
+		return nil, err
+	}
+	if _, err := adminDB.Exec("CREATE DATABASE IF NOT EXISTS " + QuoteMySQLIdentifier(databaseName) + " CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci"); err != nil {
+		return nil, err
+	}
+	fmt.Printf("created database %q\n", databaseName)
+
+	db, err = sql.Open("mysql", dsn)
+	if err != nil {
+		return nil, err
+	}
+	if err := db.Ping(); err != nil {
+		_ = db.Close()
+		return nil, err
+	}
+	return db, nil
+}
+
+func QuoteMySQLIdentifier(name string) string {
+	return "`" + strings.ReplaceAll(name, "`", "``") + "`"
+}
+
+func IsDuplicateColumnError(err error) bool {
+	var mysqlErr *mysql.MySQLError
+	return errors.As(err, &mysqlErr) && mysqlErr.Number == 1060
+}

internal/dbutil/mysql_test.go

@@ -0,0 +1,10 @@
+package dbutil
+
+import "testing"
+
+func TestQuoteMySQLIdentifier(t *testing.T) {
+	got := QuoteMySQLIdentifier("git`ocean")
+	if got != "`git``ocean`" {
+		t.Fatalf("unexpected quote: %q", got)
+	}
+}