package binstruct

import (
	"fmt"
	"reflect"
)

type StaticSizer interface {
	BinaryStaticSize() int
}

func StaticSize(obj any) int {
	sz, err := staticSize(reflect.TypeOf(obj))
	if err != nil {
		panic(err)
	}
	return sz
}

var staticSizerType = reflect.TypeOf((*StaticSizer)(nil)).Elem()

func staticSize(typ reflect.Type) (int, error) {
	if typ.Implements(staticSizerType) {
		return reflect.New(typ).Elem().Interface().(StaticSizer).BinaryStaticSize(), nil
	}
	switch typ.Kind() {
	case reflect.Uint8, reflect.Int8:
		return 1, nil
	case reflect.Ptr:
		return staticSize(typ.Elem())
	case reflect.Array:
		elemSize, err := staticSize(typ.Elem())
		if err != nil {
			return 0, err
		}
		return elemSize * typ.Len(), nil
	case reflect.Struct:
		return getStructHandler(typ).Size, nil
	default:
		return 0, fmt.Errorf("type=%v does not implement binfmt.StaticSizer and kind=%v is not a supported statically-sized kind",
			typ, typ.Kind())
	}
}