package internal

import "reflect"

type BuiltinFunc func(args []any) (any, bool)

var builtins = map[string]BuiltinFunc{
	"len": builtinLen,
}

func builtinLen(args []any) (any, bool) {
	if len(args) != 1 {
		return nil, false
	}
	if args[0] == nil {
		return 0, true
	}
	v := reflect.ValueOf(args[0])
	switch v.Kind() {
	case reflect.Slice, reflect.Array, reflect.String, reflect.Map, reflect.Chan:
		return v.Len(), true
	default:
		return 0, false
	}
}

func LookupBuiltin(name string) (BuiltinFunc, bool) {
	fn, ok := builtins[name]
	return fn, ok
}