Use more thread save Message Output

Thanks to OnBattery!

include/MessageOutput.h

@@ -2,12 +2,14 @@
 #pragma once
 
 #include <AsyncWebSocket.h>
-#include <HardwareSerial.h>
-#include <Stream.h>
 #include <TaskSchedulerDeclarations.h>
+#include <Print.h>
+#include <freertos/task.h>
 #include <mutex>
-
-#define BUFFER_SIZE 500
+#include <vector>
+#include <unordered_map>
+#include <queue>
+#include <memory>
 
 class MessageOutputClass : public Print {
 public:
@@ -22,13 +24,34 @@ private:
 
     Task _loopTask;
 
+    using message_t = std::vector<uint8_t>;
+
+    // we keep a buffer for every task and only write complete lines to the
+    // serial output and then move them to be pushed through the websocket.
+    // this way we prevent mangling of messages from different contexts.
+    std::unordered_map<TaskHandle_t, message_t> _task_messages;
+    std::queue<message_t> _lines;
+
+    // we chunk the websocket output to circumvent issues with TCP delayed ACKs:
+    // if the websocket client (Windows in particular) is using delayed ACKs,
+    // and since we wait for an ACK before sending the next chunk, we will
+    // accumulate way too many messages and we won't be able to send them out
+    // fast enough as the rate of produced messages is higher than the rate of
+    // ACKs received. by chunking and waiting in between chunks, we either
+    // "motivate" the client to send out ACKs immediately as the TCP packets are
+    // "large", or we will wait long enough for the TCP stack to send out the
+    // ACK anyways.
+    void send_ws_chunk(message_t&& line);
+    static constexpr size_t WS_CHUNK_SIZE_BYTES = 512;
+    static constexpr uint32_t WS_CHUNK_INTERVAL_MS = 250;
+    std::shared_ptr<message_t> _ws_chunk = nullptr;
+    uint32_t _last_ws_chunk_sent = 0;
+
     AsyncWebSocket* _ws = nullptr;
-    char _buffer[BUFFER_SIZE];
-    uint16_t _buff_pos = 0;
-    uint32_t _lastSend = 0;
-    bool _forceSend = false;
 
     std::mutex _msgLock;
+
+    void serialWrite(message_t const& m);
 };
 
 extern MessageOutputClass MessageOutput;