package server

import (
	"reflect"
	"sync/atomic"
)

/*net rpc need suffice the following conditions
the method’s type is exported. – 方法所属类型是导出的。
the method is exported. – 方式是导出的。
the method has two arguments, both exported (or builtin) types. – 两个入参，均为导出或内置类型。
the method’s second argument is a pointer. – 第二个入参必须是一个指针。
the method has return type error. – 返回值为 error 类型。
*/

//methodType represents a method
//include method itself, first argtype,second arg type(must be a pointer) and callCnt
type methodType struct {
	method    reflect.Method
	ArgType   reflect.Type // first arg type
	ReplyType reflect.Type // second arg type
	numCalls  uint64       //has call this method numCalls cnts
}

func (m *methodType) NumCalls() uint64 {
	//automic get numCalls
	return atomic.LoadUint64(&m.numCalls)
}

func (m *methodType) newArgv() reflect.Value {
	var argv reflect.Value
	if m.ArgType.Kind() == reflect.Ptr {
		//is pointer type return argv is also pointer
		argv = reflect.New(m.ArgType.Elem())
	} else {
		//a value type return argv is a value type
		argv = reflect.New(m.ArgType).Elem()
	}
	return argv
}

func (m *methodType) newReply() reflect.Value {
	//reply must be a pointer type
	replyv := reflect.New(m.ReplyType.Elem())
	switch m.ReplyType.Elem().Kind() {
	//if ReplyType is map or slice, it must make address
	case reflect.Map:
		replyv.Elem().Set(reflect.MakeMap(m.ReplyType.Elem()))
	case reflect.Slice:
		replyv.Elem().Set(reflect.MakeSlice(m.ReplyType.Elem(), 0, 0))
	}
	return replyv
}