argumenter.go

package argumenter

import (
	"fmt"
	"reflect"
	"strconv"
	"strings"
)

/*
 * reflect version
 */

func ValidReflect(in interface{}) error {

	v := reflect.ValueOf(in)

	if v.Kind() != reflect.Ptr || v.Elem().Kind() != reflect.Struct {
		return fmt.Errorf("must be pointer of struct")
	}

	vv := v.Elem()
	t := vv.Type()

	for i := 0; i < t.NumField(); i++ {
		fv := vv.Field(i)
		ft := t.Field(i)

		for _, p := range strings.Split(ft.Tag.Get("arg"), ",") {

			pair := strings.SplitN(p, "=", 2)
			var intval int64
			switch ft.Type.Kind() {
			case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
				i, e := strconv.ParseInt(pair[1], 10, 64)
				if e != nil {
					return fmt.Errorf("%s field tag is invalid: %s", ft.Name, e)
				}
				intval = i
			}

			switch pair[0] {
			case "max":
				switch ft.Type.Kind() {
				case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
					if fv.Int() > intval {
						return fmt.Errorf("%s field must less than %d: %d", ft.Name, intval, fv.Int())
					}
				}
			case "min":
				switch ft.Type.Kind() {
				case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
					if fv.Int() < intval {
						return fmt.Errorf("%s field must greater than %d: %d", ft.Name, intval, fv.Int())
					}
				}
			case "default":
				switch ft.Type.Kind() {
				case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
					if fv.Int() == 0 {
						fv.SetInt(intval)
					}
				}
			}
		}
	}

	return nil
}

/*
 * generate version
 */

type MyArg struct {
	Arg1 int `arg:"min=0,max=10,default=5"`
}

func ValidGenerate(in *MyArg) error {
	if in.Arg1 > 10 {
		return fmt.Errorf("Arg1 field must less than %d: %d", 10, in.Arg1)
	}
	if in.Arg1 < 0 {
		return fmt.Errorf("Arg1 field must greater than %d: %d", 0, in.Arg1)
	}
	if in.Arg1 == 0 {
		in.Arg1 = 5
	}
	return nil
}