[Idea] New Command Register Interface about bdlauncher HOT 10 OPEN

@codehz What about
void teleport_to_player(CommandOriginHelper&/Helper class for access to BDS CommandOrigin/ origin,CustomCommandResult& res,ServerPlayer* sp){
//origin.getPlayer returns ServerPlayer*
if(!origin.isPlayer()){
res.error();
res<<"error "<<123<<origin.getName(); //overloaded << operator
}
}
BDLCMDRegistry::registerCommand("tpa",overload1/*Infer arguments automatically */,overload2,if_no_overload_found_handler);

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@codehz and could you please show how to register a command with enum?
like /tpa {accept,deny},etc.

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to register enum:

enum class MyEnum: int {A, B};
auto test = BDLCommandRegistry::newEnum<MyEnum>("test");
test.add("A", MyEnum::A);
test.add("B", MyEnum::B);

dynamic enum:

// in global scope
static auto test = BDLCommandRegistry::newDynamicEnum<decltype("test_dynamic"_dynenum)>(); // use gcc extension to generate type from string
// in some function
test.set({"A", "B"});
test.clear();
test.add("C");

and a better command register method:

auto command = BDLCommandRegistry::newCommand("command");
command.add(impl_01);
command.add(impl_02);
command.set_fallback(if_no_overload_found_handler); // I'm not sure if it can be implemented...

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maybe we should use codegen insteads of just template meta programming...
or the argument name cannot be inferred from function..
(and optional argument)

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@codehz yeah,you're right.
I wonder whether overload will be called,if no suitable overload is found.
like this.
/tpa <{to,from}:enum> name:player
/tpa fallback:string <--- will be called when "/tpa wrong usage xxxx"

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BTW, the command parsing is happened in server side.. so the malformed command expression would be able to detect in server side and rerouting to fallback handler.. seems pointless..

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@codehz using mojang command overload api seems like a morr complex way to solve problem(need to generate class and vtable dynamically(or need a codegen),need to reverse-engineer more api).
Use a simple lexer with overload support maybe a better choice?
Maybe we can use tricks to make client show overloads,like multi-line command description.(hadnt tested)

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@codehz I dont know if duplicated availableCommandsPacket with only one command works well.(it means sending overloads of a mod
commands after server sent previous availableCommandsPacket to client )
Modifing availableCommandsPacket::write seems like a difficult job.

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@codehz @codehz new idea:

void tpa_to_impl(...,ServerPlayer* sp,int xx){

}
CommandBase cmd("tpa");
cmd.overload("to <dest:player> <testval:int>",tpa_to_impl);//use template like overload(string_view,void(*)(...,T ,T2) to determine how many arguments need to be parsed(in base.h) and base.so just exports regCommand0(sview,void *function),regCommand1...,etc..
and lexer parses overload,and do some preparations(convert string to int,ServerPlayer*,etc)
and use (void(*)(...,void*,void*))callback(arg0,arg1,argx)

CONS :
1.assume that all arguments are 64bits long.(so passing string_view and const string(abi:cxx11) cant work?(because string_view uses two registers).And float cant work ad well(because it uses %xmm0 register) )
2.use a lot of else
if to make right calls(right counts of arguments)

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alternative concept: for codegen

// header (.h)
struct Teleport : CustomCommandDescription {
static constexpr auto name = "teleport";
static constexpr auto permission = CommandPermission::OP;
// any name
void impl_01(ServerPlayer *target); // generate `teleport <target: player>`
// use std::optional for optional argument
void impl_02(Vec3 pos, std::optional<int> angle);  // generate `teleport <pos: position> [angle: int]`
// use enum
void impl_03(MyEnum target);  // generate `teleport <target: my_enum>`
};
extern "C" {
BDL_EXPORT int mod_register_command(CommandRegistry *); // codegen
}
// impl (.cpp)
void Teleport::impl_01(ServerPlayer *target) {}
....

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