initial rate limit support

myirc/include/connection.hpp

@@ -2,6 +2,7 @@
 
 #include "irc_command.hpp"
 #include "ircmsg.hpp"
+#include "ratelimit.hpp"
 #include "ref.hpp"
 #include "snote.hpp"
 #include "stream.hpp"
@@ -46,7 +47,12 @@ private:
     // AUTHENTICATE support
     std::string authenticate_buffer_;
 
+    /// write buffers after consulting with rate limit
     auto write_buffers() -> void;
+
+    /// write a specific number of messages now
+    auto write_buffers(size_t) -> void;
+
     auto dispatch_line(char *line) -> void;
 
     static constexpr std::chrono::seconds watchdog_duration = std::chrono::seconds{30};
@@ -68,6 +74,7 @@ public:
     boost::signals2::signal<void(IrcCommand, const IrcMsg &)> sig_ircmsg;
     boost::signals2::signal<void(SnoteMatch &)> sig_snote;
     boost::signals2::signal<void(std::string_view)> sig_authenticate;
+    std::unique_ptr<RateLimit> rate_limit;
 
     Connection(boost::asio::io_context &io);
 

myirc/include/ratelimit.hpp

@@ -0,0 +1,20 @@
+#pragma once
+
+#include <chrono>
+#include <utility>
+
+struct RateLimit {
+    virtual ~RateLimit();
+    auto virtual query(size_t want_to_send) -> std::pair<std::chrono::milliseconds, size_t> = 0;
+};
+
+struct Rfc1459RateLimit final : RateLimit
+{
+    using clock = std::chrono::steady_clock;
+
+    std::chrono::milliseconds cost_ {2'000};
+    std::chrono::milliseconds allowance_ {10'000};
+    clock::time_point horizon_{};
+
+    auto query(size_t want_to_send) -> std::pair<std::chrono::milliseconds, size_t> override;
+};