Add Lua HTTP Client API

[Dreae]

This adds lua functions for sending HTTP POST and GET requests (closes #55). The requests are sent synchronously using the current httplib header on a boost::asio::thread_pool so as to not block the lua thread. The request results are returned to lua via callback functions.
It supports both HTTP and HTTPS, the API looks like this:

-- err - string error if something went wrong, or else nil
-- status - numeric HTTP status code
-- body - string response body
-- headers - response headers as a table 
Http.Get("http://localhost:8080", "/hello", function (err, status, body, headers)
    print(err)
    print(status)
    print(headers)
end)

Http.Post("http://localhost:8080", "/hello", { hello = "world" }, function (err, status, body, headers)
    print(err)
    print(status)
    print(headers)
end)

The following overloads are available for both new methods:

Http.Get(host, path, callback)
Http.Get(host, path, headers, callback)
-- For these methods body is passed as a table and sent as `application/x-www-form-urlencoded`
Http.Post(host, path, body, callback)
Http.Post(host, path, body, headers, callback)
-- For these methods body is passed as a string and you must provide a content_type
Http.Post(host, path, body, content_type, callback)
Http.Post(host, path, body, content_type, headers, callback)

There are some supporting changes to TLuaEngine and TLuaEngine::QueuedFunction to support enqueuing function calls to a reference to a function on the lua stack, as well as a new overload to StateThreadData::EnqueueFunction

[[nodiscard]] std::shared_ptr<TLuaResult> EnqueueFunctionCall(std::shared_ptr<sol::reference> FunctionRef, const std::vector<TLuaArgTypes>& Args);

[lionkor]

Hi, do you have Discord? I'd like to talk to you really quick :) If you could add me lion_kor that'd be awesome.

[lionkor]

The existing "Http.CreateConnection" can be nuked, it's not used anywhere :)

[lionkor]

Rebased to update to current master, if you can't pull now, try git fetch && git reset --hard origin/master (this will reset your own changes if you made any that aren't pushed)

[lionkor]

Currently doesn't compile for me:

/home/lion/src/BeamMP-Server/src/TLuaEngine.cpp: At global scope:
/home/lion/src/BeamMP-Server/src/TLuaEngine.cpp:608:18: error: no previous declaration for ‘httplib::Headers table_to_headers(const sol::table&)’ [-Werror=missing-declarations]
  608 | httplib::Headers table_to_headers(const sol::table& headers) {
      |                  ^~~~~~~~~~~~~~~~

[lionkor]

Hi @Dreae, sorry it's been so slow. It seems like it doesn't work when the host has a trailing /

[lionkor]

I basically joined back into the team around when you made the latest changes, so there was more than enough to do that had very high prio - but I think the way you solved this is very very neat, and it'd be cool if we could give you the contributor role in our discord so we can all chat for any possible future issues as well :)

[carsakiller]

Is there any chance this could be merged in as part of a minor update rather than 4.0.0? This feature is super valuable, and I would love to get my hands on it as soon as possible 🙂

[lionkor]

This is still in review as last time I tested it there were many issues.

[lionkor]

needs fixing, please reopen when ready

[Tcoder3]

@Dreae Are you planning to fix/continue/reopen this? This would be useful for my project.
Otherwise is there some guidance/tutorial/something available for the luasocket or similar library to make HTTP requests and/or open sockets/serve HTTP from beammp server lua?

[carsakiller]

@Tcoder3 HTTP is something I've been trying to work around as well. I used to use io.popen to call a separate process that would make the request for me, however that no longer works. My last hope for a workaround is probably os.execute and pipe into a temp file that can then be read from 😔

[20dka]

@carsakiller that is a workaround I've seen others use as well, but we are aware of the bug with popen

[Dreae]

@Tcoder3 as far as I know this code is working. There were some minor changes requested, which I made, before the PR was closed as "needs fixing" so 🤷

[Tcoder3]

@Dreae Would it be a bad idea to reopen the PR or @-mention the guy who closed it and say that you want to know what needs fixing or does not work? Because of cource you can't fix something you don't know about... 🤷

[Dreae]

I probably wont be reopening it personally, but I'm happy to answer questions about the code or provide assistance if someone else wants to take up the torch to get it merged