dep: Add discord-rpc

dep/discord-rpc/src/rpc_connection.h

@@ -0,0 +1,59 @@
+#pragma once
+
+#include "connection.h"
+#include "serialization.h"
+
+// I took this from the buffer size libuv uses for named pipes; I suspect ours would usually be much
+// smaller.
+constexpr size_t MaxRpcFrameSize = 64 * 1024;
+
+struct RpcConnection {
+    enum class ErrorCode : int {
+        Success = 0,
+        PipeClosed = 1,
+        ReadCorrupt = 2,
+    };
+
+    enum class Opcode : uint32_t {
+        Handshake = 0,
+        Frame = 1,
+        Close = 2,
+        Ping = 3,
+        Pong = 4,
+    };
+
+    struct MessageFrameHeader {
+        Opcode opcode;
+        uint32_t length;
+    };
+
+    struct MessageFrame : public MessageFrameHeader {
+        char message[MaxRpcFrameSize - sizeof(MessageFrameHeader)];
+    };
+
+    enum class State : uint32_t {
+        Disconnected,
+        SentHandshake,
+        AwaitingResponse,
+        Connected,
+    };
+
+    BaseConnection* connection{nullptr};
+    State state{State::Disconnected};
+    void (*onConnect)(JsonDocument& message){nullptr};
+    void (*onDisconnect)(int errorCode, const char* message){nullptr};
+    char appId[64]{};
+    int lastErrorCode{0};
+    char lastErrorMessage[256]{};
+    RpcConnection::MessageFrame sendFrame;
+
+    static RpcConnection* Create(const char* applicationId);
+    static void Destroy(RpcConnection*&);
+
+    inline bool IsOpen() const { return state == State::Connected; }
+
+    void Open();
+    void Close();
+    bool Write(const void* data, size_t length);
+    bool Read(JsonDocument& message);
+};