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validator.go
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validator.go
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package csvtogo
import (
"fmt"
"reflect"
"strconv"
)
const (
tagMin = "min"
tagMax = "max"
)
func validateStruct[T any](f T, row int) error {
v := reflect.ValueOf(&f).Elem()
for i := 0; i < v.NumField(); i++ {
//check minimum value length
err := checkMin[T](f, i, row, v)
if err != nil {
return err
}
//check maximum value length
err = checkMax[T](f, i, row, v)
if err != nil {
return err
}
}
return nil
}
func checkMin[T any](field T, sequence, row int, v reflect.Value) error {
minimum, err := isTagFound[T](field, sequence, tagMin, v)
if err != nil {
return err
}
if minimum < 0 {
//no tag found, then skip validate
return nil
}
value := fmt.Sprintf("%v", v.Field(sequence).Interface())
if len([]rune(value)) < minimum {
return fmt.Errorf("value of %v at row %v is invalid, value length must more than or equal %v, but got: %v",
v.Type().Field(sequence).Name,
row,
minimum,
len([]rune(value)),
)
}
return nil
}
func checkMax[T any](field T, sequence, row int, v reflect.Value) error {
maximum, err := isTagFound[T](field, sequence, tagMax, v)
if err != nil {
return err
}
if maximum < 0 {
//no tag found, then skip validate
return nil
}
value := fmt.Sprintf("%v", v.Field(sequence).Interface())
if len([]rune(value)) > maximum {
return fmt.Errorf("value of %v at row %v is invalid, value length must less than or equal %v, but got: %v",
v.Type().Field(sequence).Name,
row,
maximum,
len([]rune(value)),
)
}
return nil
}
func isTagFound[T any](field T, sequence int, tag string, v reflect.Value) (int, error) {
tmp := reflect.TypeOf(&field).Elem().Field(sequence).Tag.Get(tag)
if len(tmp) > 0 {
val, err := strconv.Atoi(tmp)
if err != nil {
return -1, fmt.Errorf("tag %v of field %v must be integer, got: %v", tag, v.Type().Field(sequence).Name, tmp)
}
if val < 0 {
return -1, fmt.Errorf("tag %v of field %v must more than zero, got: %v", tag, v.Type().Field(sequence).Name, tmp)
}
return val, nil
}
return -1, nil
}