started working on the backend

backend/pkg/db/db.go

@@ -0,0 +1,225 @@
+package db
+
+import (
+	"database/sql"
+	"fmt"
+	"reflect"
+	"strings"
+	"time"
+
+	"github.com/go-sql-driver/mysql"
+	"github.com/jmoiron/sqlx"
+	_config "github.com/johannesbuehl/golunteer/backend/pkg/config"
+	_logger "github.com/johannesbuehl/golunteer/backend/pkg/logger"
+)
+
+var logger = _logger.Logger
+var config = _config.Config
+
+// connection to database
+var DB *sqlx.DB
+
+func init() {
+	// setup the database-connection
+	sqlConfig := mysql.Config{
+		AllowNativePasswords: true,
+		Net:                  "tcp",
+		User:                 config.Database.User,
+		Passwd:               config.Database.Password,
+		Addr:                 config.Database.Host,
+		DBName:               config.Database.Database,
+	}
+
+	// connect to the database
+	DB = sqlx.MustOpen("mysql", sqlConfig.FormatDSN())
+	DB.SetMaxIdleConns(10)
+	DB.SetMaxIdleConns(100)
+	DB.SetConnMaxLifetime(time.Minute)
+
+}
+
+// query the database
+func SelectOld[T any](table string, where string, args ...any) ([]T, error) {
+	// validate columns against struct T
+	tType := reflect.TypeOf(new(T)).Elem()
+	columns := make([]string, tType.NumField())
+
+	validColumns := make(map[string]any)
+	for ii := 0; ii < tType.NumField(); ii++ {
+		field := tType.Field(ii)
+		validColumns[strings.ToLower(field.Name)] = struct{}{}
+		columns[ii] = strings.ToLower(field.Name)
+	}
+
+	for _, col := range columns {
+		if _, ok := validColumns[strings.ToLower(col)]; !ok {
+			return nil, fmt.Errorf("invalid column: %s for struct type %T", col, new(T))
+		}
+	}
+
+	// create the query
+	completeQuery := fmt.Sprintf("SELECT %s FROM %s", strings.Join(columns, ", "), table)
+
+	if where != "" && where != "*" {
+		completeQuery = fmt.Sprintf("%s WHERE %s", completeQuery, where)
+	}
+
+	var rows *sql.Rows
+	var err error
+
+	if len(args) > 0 {
+		DB.Ping()
+
+		rows, err = DB.Query(completeQuery, args...)
+	} else {
+		DB.Ping()
+
+		rows, err = DB.Query(completeQuery)
+	}
+
+	if err != nil {
+		logger.Error().Msgf("database access failed with error %v", err)
+
+		return nil, err
+	}
+
+	defer rows.Close()
+	results := []T{}
+
+	for rows.Next() {
+		var lineResult T
+
+		scanArgs := make([]any, len(columns))
+		v := reflect.ValueOf(&lineResult).Elem()
+
+		for ii, col := range columns {
+			field := v.FieldByName(col)
+
+			if field.IsValid() && field.CanSet() {
+				scanArgs[ii] = field.Addr().Interface()
+			} else {
+				logger.Warn().Msgf("Field %s not found in struct %T", col, lineResult)
+				scanArgs[ii] = new(any) // save dummy value
+			}
+		}
+
+		// scan the row into the struct
+		if err := rows.Scan(scanArgs...); err != nil {
+			logger.Warn().Msgf("Scan-error: %v", err)
+
+			return nil, err
+		}
+
+		results = append(results, lineResult)
+	}
+
+	if err := rows.Err(); err != nil {
+		logger.Error().Msgf("rows-error: %v", err)
+		return nil, err
+	} else {
+		return results, nil
+	}
+}
+
+// insert data intot the databse
+func Insert(table string, vals any) error {
+	// extract columns from vals
+	v := reflect.ValueOf(vals)
+	t := v.Type()
+
+	columns := make([]string, t.NumField())
+	values := make([]any, t.NumField())
+
+	for ii := 0; ii < t.NumField(); ii++ {
+		fieldValue := v.Field(ii)
+
+		field := t.Field(ii)
+
+		columns[ii] = strings.ToLower(field.Name)
+		values[ii] = fieldValue.Interface()
+	}
+
+	placeholders := strings.Repeat(("?, "), len(columns))
+	placeholders = strings.TrimSuffix(placeholders, ", ")
+
+	completeQuery := fmt.Sprintf("INSERT INTO %s (%s) VALUES (%s)", table, strings.Join(columns, ", "), placeholders)
+
+	_, err := DB.Exec(completeQuery, values...)
+
+	return err
+}
+
+// update data in the database
+func Update(table string, set, where any) error {
+	setV := reflect.ValueOf(set)
+	setT := setV.Type()
+
+	setColumns := make([]string, setT.NumField())
+	setValues := make([]any, setT.NumField())
+
+	for ii := 0; ii < setT.NumField(); ii++ {
+		fieldValue := setV.Field(ii)
+
+		field := setT.Field(ii)
+
+		setColumns[ii] = strings.ToLower(field.Name) + " = ?"
+		setValues[ii] = fieldValue.Interface()
+	}
+
+	whereV := reflect.ValueOf(where)
+	whereT := whereV.Type()
+
+	whereColumns := make([]string, whereT.NumField())
+	whereValues := make([]any, whereT.NumField())
+
+	for ii := 0; ii < whereT.NumField(); ii++ {
+		fieldValue := whereV.Field(ii)
+
+		// skip empty (zero) values
+		if !fieldValue.IsZero() {
+			field := whereT.Field(ii)
+
+			whereColumns[ii] = strings.ToLower(field.Name) + " = ?"
+			whereValues[ii] = fmt.Sprint(fieldValue.Interface())
+		}
+	}
+
+	sets := strings.Join(setColumns, ", ")
+	wheres := strings.Join(whereColumns, " AND ")
+
+	placeholderValues := append(setValues, whereValues...)
+
+	completeQuery := fmt.Sprintf("UPDATE %s SET %s WHERE %s", table, sets, wheres)
+
+	_, err := DB.Exec(completeQuery, placeholderValues...)
+
+	return err
+}
+
+// remove data from the database
+func Delete(table string, vals any) error {
+	// extract columns from vals
+	v := reflect.ValueOf(vals)
+	t := v.Type()
+
+	columns := make([]string, t.NumField())
+	values := make([]any, t.NumField())
+
+	for ii := 0; ii < t.NumField(); ii++ {
+		fieldValue := v.Field(ii)
+
+		// skip empty (zero) values
+		if !fieldValue.IsZero() {
+			field := t.Field(ii)
+
+			columns[ii] = strings.ToLower(field.Name) + " = ?"
+			values[ii] = fmt.Sprint(fieldValue.Interface())
+		}
+	}
+
+	completeQuery := fmt.Sprintf("DELETE FROM %s WHERE %s", table, strings.Join(columns, ", "))
+
+	_, err := DB.Exec(completeQuery, values...)
+
+	return err
+}