Add onConnect callback to EventSources

usage:
  AsyncEventSource events("/events");
  events.onConnect([](AsyncEventSourceClient *client){
    client->send("Hello!",NULL,0,1000);
  });
  server.addHandler(&events);
  ...
  events.send("boot finished","system");//send "system" event

src/AsyncEventSource.cpp

@@ -20,109 +20,7 @@
 #include "Arduino.h"
 #include "AsyncEventSource.h"
 
-// Client
+static String generateEventMessage(const char *message, const char *event, uint32_t id, uint32_t reconnect){
-
-AsyncEventSourceClient::AsyncEventSourceClient(AsyncWebServerRequest *request, AsyncEventSource *server){
-  _client = request->client();
-  _server = server;
-  next = NULL;
-  //_client->onError([](void *r, AsyncClient* c, int8_t error){ ((AsyncEventSourceClient*)(r))->_onError(error); }, this);
-  //_client->onAck([](void *r, AsyncClient* c, size_t len, uint32_t time){ ((AsyncEventSourceClient*)(r))->_onAck(len, time); }, this);
-  //_client->onPoll([](void *r, AsyncClient* c){ ((AsyncEventSourceClient*)(r))->_onPoll(); }, this);
-  _client->onError(NULL, NULL);
-  _client->onAck(NULL, NULL);
-  _client->onPoll(NULL, NULL);
-  _client->onData(NULL, NULL);
-  _client->onTimeout([](void *r, AsyncClient* c, uint32_t time){ ((AsyncEventSourceClient*)(r))->_onTimeout(time); }, this);
-  _client->onDisconnect([](void *r, AsyncClient* c){ ((AsyncEventSourceClient*)(r))->_onDisconnect(); }, this);
-  _server->_addClient(this);
-  delete request;
-}
-
-AsyncEventSourceClient::~AsyncEventSourceClient(){
-  close();
-}
-
-//void AsyncEventSourceClient::_onAck(size_t len, uint32_t time){}
-//void AsyncEventSourceClient::_onPoll(){}
-//void AsyncEventSourceClient::_onError(int8_t){}
-void AsyncEventSourceClient::_onTimeout(uint32_t time){
-  _client->close(true);
-}
-
-void AsyncEventSourceClient::_onDisconnect(){
-  AsyncClient* cl = _client;
-  _client = NULL;
-  cl->free();
-  delete cl;
-  _server->_handleDisconnect(this);
-}
-
-void AsyncEventSourceClient::close(){
-  if(_client != NULL)
-    _client->close(true);
-}
-
-void AsyncEventSourceClient::send(const char * message, size_t len){
-  if(!_client->canSend()){
-    return;
-  }
-  if(_client->space() < len){
-    return;
-  }
-  _client->write(message, len);
-}
-
-
-// Handler
-
-AsyncEventSource::AsyncEventSource(String url):_url(url){}
-
-AsyncEventSource::~AsyncEventSource(){
-  close();
-}
-
-void AsyncEventSource::_addClient(AsyncEventSourceClient * client){
-  if(_clients == NULL){
-    _clients = client;
-    return;
-  }
-  AsyncEventSourceClient * c = _clients;
-  while(c->next != NULL) c = c->next;
-  c->next = client;
-}
-
-void AsyncEventSource::_handleDisconnect(AsyncEventSourceClient * client){
-  if(_clients == NULL){
-    return;
-  }
-  if(_clients == client){
-    _clients = client->next;
-    delete client;
-    return;
-  }
-  AsyncEventSourceClient * c = _clients;
-  while(c->next != NULL && c->next != client) c = c->next;
-  if(c->next == NULL){
-    return;
-  }
-  c->next = client->next;
-  delete client;
-}
-
-void AsyncEventSource::close(){
-  AsyncEventSourceClient * c = _clients;
-  while(c != NULL){
-    if(c->connected())
-      c->close();
-    c = c->next;
-  }
-}
-
-void AsyncEventSource::send(const char *message, const char *event, uint32_t id, uint32_t reconnect){
-  if(_clients == NULL)
-    return;
-
   String ev = "";
 
   if(reconnect){
@@ -151,7 +49,6 @@ void AsyncEventSource::send(const char *message, const char *event, uint32_t id,
       char * nextN = strchr(lineStart, '\n');
       char * nextR = strchr(lineStart, '\r');
       if(nextN == NULL && nextR == NULL){
-        //last line
         size_t llen = ((char *)message + messageLen) - lineStart;
         char * ldata = (char *)malloc(llen+1);
         if(ldata != NULL){
@@ -204,15 +101,134 @@ void AsyncEventSource::send(const char *message, const char *event, uint32_t id,
     } while(lineStart < ((char *)message + messageLen));
   }
 
-  //os_printf("EVENT_SOURCE:\n%s", ev.c_str());
+  return ev;
+}
 
+// Client
+
+AsyncEventSourceClient::AsyncEventSourceClient(AsyncWebServerRequest *request, AsyncEventSource *server){
+  _client = request->client();
+  _server = server;
+  next = NULL;
+  //_client->onError([](void *r, AsyncClient* c, int8_t error){ ((AsyncEventSourceClient*)(r))->_onError(error); }, this);
+  //_client->onAck([](void *r, AsyncClient* c, size_t len, uint32_t time){ ((AsyncEventSourceClient*)(r))->_onAck(len, time); }, this);
+  //_client->onPoll([](void *r, AsyncClient* c){ ((AsyncEventSourceClient*)(r))->_onPoll(); }, this);
+  _client->onError(NULL, NULL);
+  _client->onAck(NULL, NULL);
+  _client->onPoll(NULL, NULL);
+  _client->onData(NULL, NULL);
+  _client->onTimeout([](void *r, AsyncClient* c, uint32_t time){ ((AsyncEventSourceClient*)(r))->_onTimeout(time); }, this);
+  _client->onDisconnect([](void *r, AsyncClient* c){ ((AsyncEventSourceClient*)(r))->_onDisconnect(); }, this);
+  _server->_addClient(this);
+  delete request;
+}
+
+AsyncEventSourceClient::~AsyncEventSourceClient(){
+  close();
+}
+
+//void AsyncEventSourceClient::_onAck(size_t len, uint32_t time){}
+//void AsyncEventSourceClient::_onPoll(){}
+//void AsyncEventSourceClient::_onError(int8_t){}
+void AsyncEventSourceClient::_onTimeout(uint32_t time){
+  _client->close(true);
+}
+
+void AsyncEventSourceClient::_onDisconnect(){
+  AsyncClient* cl = _client;
+  _client = NULL;
+  cl->free();
+  delete cl;
+  _server->_handleDisconnect(this);
+}
+
+void AsyncEventSourceClient::close(){
+  if(_client != NULL)
+    _client->close(true);
+}
+
+void AsyncEventSourceClient::write(const char * message, size_t len){
+  if(!_client->canSend()){
+    return;
+  }
+  if(_client->space() < len){
+    return;
+  }
+  _client->write(message, len);
+}
+
+void AsyncEventSourceClient::send(const char *message, const char *event, uint32_t id, uint32_t reconnect){
+  String ev = generateEventMessage(message, event, id, reconnect);
+  write(ev.c_str(), ev.length());
+}
+
+
+// Handler
+
+AsyncEventSource::AsyncEventSource(String url)
+  : _url(url)
+  , _clients(NULL)
+  , _connectcb(NULL)
+{}
+
+AsyncEventSource::~AsyncEventSource(){
+  close();
+}
+
+void AsyncEventSource::onConnect(ArEventHandlerFunction cb){
+  _connectcb = cb;
+}
+
+void AsyncEventSource::_addClient(AsyncEventSourceClient * client){
+  if(_clients == NULL){
+    _clients = client;
+    return;
+  }
+  AsyncEventSourceClient * c = _clients;
+  while(c->next != NULL) c = c->next;
+  c->next = client;
+  if(_connectcb)
+    _connectcb(client);
+}
+
+void AsyncEventSource::_handleDisconnect(AsyncEventSourceClient * client){
+  if(_clients == NULL){
+    return;
+  }
+  if(_clients == client){
+    _clients = client->next;
+    delete client;
+    return;
+  }
+  AsyncEventSourceClient * c = _clients;
+  while(c->next != NULL && c->next != client) c = c->next;
+  if(c->next == NULL){
+    return;
+  }
+  c->next = client->next;
+  delete client;
+}
+
+void AsyncEventSource::close(){
   AsyncEventSourceClient * c = _clients;
   while(c != NULL){
     if(c->connected())
-      c->send(ev.c_str(), ev.length());
+      c->close();
+    c = c->next;
+  }
+}
+
+void AsyncEventSource::send(const char *message, const char *event, uint32_t id, uint32_t reconnect){
+  if(_clients == NULL)
+    return;
+
+  String ev = generateEventMessage(message, event, id, reconnect);
+  AsyncEventSourceClient * c = _clients;
+  while(c != NULL){
+    if(c->connected())
+      c->write(ev.c_str(), ev.length());
     c = c->next;
   }
-  ev = String();
 }
 
 bool AsyncEventSource::canHandle(AsyncWebServerRequest *request){

src/AsyncEventSource.h

@@ -27,6 +27,7 @@
 class AsyncEventSource;
 class AsyncEventSourceResponse;
 class AsyncEventSourceClient;
+typedef std::function<void(AsyncEventSourceClient *client)> ArEventHandlerFunction;
 
 class AsyncEventSourceClient {
   private:
@@ -41,7 +42,8 @@ class AsyncEventSourceClient {
 
     AsyncClient* client(){ return _client; }
     void close();
-    void send(const char * message, size_t len);
+    void write(const char * message, size_t len);
+    void send(const char *message, const char *event=NULL, uint32_t id=0, uint32_t reconnect=0);
     bool connected(){ return (_client != NULL) && _client->connected(); }
 
     //system callbacks (do not call)
@@ -56,6 +58,7 @@ class AsyncEventSource: public AsyncWebHandler {
   private:
     String _url;
     AsyncEventSourceClient * _clients;
+    ArEventHandlerFunction _connectcb;
     uint32_t _cNextId;
   public:
     AsyncEventSource(String url);
@@ -63,6 +66,7 @@ class AsyncEventSource: public AsyncWebHandler {
 
     const char * url(){ return _url.c_str(); }
     void close();
+    void onConnect(ArEventHandlerFunction cb);
     void send(const char *message, const char *event=NULL, uint32_t id=0, uint32_t reconnect=0);
 
     //system callbacks (do not call)