From c106094540cb3f4c8dcb06bcfca0ee4af5d32fed Mon Sep 17 00:00:00 2001
From: Barry Kane <barra@ocathain.ie>
Date: Sun, 9 Jul 2023 01:15:05 +0100
Subject: [PATCH] Basic Client Side Prediction

---
 README.org               | 11 +++++++++++
 src/client/cspt-client.c | 12 +++++++++++-
 src/cspt-state.c         | 37 ++++++++++++++++++++++++++++---------
 src/server/cspt-server.c |  4 ++--
 4 files changed, 52 insertions(+), 12 deletions(-)

diff --git a/README.org b/README.org
index 49c9d15..2db6212 100644
--- a/README.org
+++ b/README.org
@@ -32,6 +32,17 @@ I think my first step will be creating the TCP portion of the client-server
 interaction. This should be relatively trivial, so I can get right to it. Simply
 transmitting a few integers back and forth will do well.
 
+** Entry 02: TCP & UDP basics completed:
+The TCP portion is completed, and I have also created a basic simulation which
+is based on the model that is described in the first article in the series, and
+the model which "Spacewar!" currently uses. Time to start work on actual client
+side prediction and other techniques. 
+
+** Entry 03: That seems far too easy:
+Simply duplicating the server's game thread seems to meet the concept of client
+side prediction described in the second article. I'd imagine there's still a lot
+more to deal with, but we'll see how much of a difference this makes to how it
+feels. I'll report back.
 
 * Notes On Techniques:
 ** Entry 00: Where I'm Learning All This From:
diff --git a/src/client/cspt-client.c b/src/client/cspt-client.c
index 3fda7f1..02f89e1 100644
--- a/src/client/cspt-client.c
+++ b/src/client/cspt-client.c
@@ -91,6 +91,15 @@ void * networkHandler(void * parameters)
 	}
 }
 
+void * gameThreadHandler(void * arguments)
+{
+	while (true)
+	{
+		doGameTick(arguments);
+		usleep(15625);
+	}
+}
+
 void * graphicsThreadHandler(void * parameters)
 {
 	struct gameState * state = ((struct threadParameters *)parameters)->state;
@@ -201,7 +210,7 @@ void * graphicsThreadHandler(void * parameters)
 int main(int argc, char ** argv)
 {
 	int serverSocket = 0;
-	pthread_t graphicsThread, networkThread;
+	pthread_t graphicsThread, networkThread, gameThread;
 	struct CsptMessage currentMessage;
 	bool continueRunning = true;
 	struct gameState * currentState = calloc(1, sizeof(struct gameState));
@@ -249,6 +258,7 @@ int main(int argc, char ** argv)
 	parameters.message = clientInput;
 	parameters.state = currentState;
 	pthread_create(&graphicsThread, NULL, graphicsThreadHandler, &parameters);
+	pthread_create(&gameThread, NULL, gameThreadHandler, currentState);
 	pthread_create(&networkThread, NULL, networkHandler, &parameters);
 	
 	while (continueRunning)
diff --git a/src/cspt-state.c b/src/cspt-state.c
index 1935d4f..b6795f7 100644
--- a/src/cspt-state.c
+++ b/src/cspt-state.c
@@ -20,31 +20,50 @@ void doGameTick(struct gameState * state)
 		// Calculate acceleration:
 		if (state->clients[index].leftAcceleration)
 		{
-			state->clients[index].xVelocity -= 0.1;
+			state->clients[index].xVelocity -= 0.5;
 		}
 		if (state->clients[index].rightAcceleration)
 		{
-			state->clients[index].xVelocity += 0.1;
+			state->clients[index].xVelocity += 0.5;
+		}
+		if (!state->clients[index].leftAcceleration && !state->clients[index].rightAcceleration)
+		{
+			state->clients[index].xVelocity *= 0.9;			
 		}
 		if (state->clients[index].upAcceleration)
 		{
-			state->clients[index].yVelocity -= 0.1;
+			state->clients[index].yVelocity -= 0.5;
 		}
 		if (state->clients[index].downAcceleration)
 		{
-			state->clients[index].yVelocity += 0.1;
+			state->clients[index].yVelocity += 0.5;
+		}
+		if (!state->clients[index].upAcceleration && !state->clients[index].downAcceleration)
+		{
+			state->clients[index].yVelocity *= 0.9;			
 		}
-
 		// Do movement:
 		state->clients[index].xPosition += state->clients[index].xVelocity;
 		state->clients[index].yPosition += state->clients[index].yVelocity;
-		if(state->clients[index].xPosition > 600 || state->clients[index].xPosition < 0)
+		if(state->clients[index].xPosition > 1000)
 		{
-			state->clients[index].xPosition = 300;
+			state->clients[index].xPosition = 1000;
+			state->clients[index].xVelocity = 0;
 		}
-		if(state->clients[index].yPosition > 600 || state->clients[index].yPosition < 0)
+		if(state->clients[index].xPosition < 0)
 		{
-			state->clients[index].yPosition = 300;
+			state->clients[index].xPosition = 0;
+			state->clients[index].xVelocity = 0;
+		}
+		if(state->clients[index].yPosition > 1000)
+		{
+			state->clients[index].yPosition = 1000;
+			state->clients[index].yVelocity = 0;
+		}
+		if(state->clients[index].yPosition < 0)
+		{
+			state->clients[index].yPosition = 0;
+			state->clients[index].yVelocity = 0;
 		}
 	}
 }
diff --git a/src/server/cspt-server.c b/src/server/cspt-server.c
index 2b514c9..58efb31 100644
--- a/src/server/cspt-server.c
+++ b/src/server/cspt-server.c
@@ -70,10 +70,10 @@ void * networkThreadHandler(void * arguments)
 
 void * gameThreadHandler(void * arguments)
 {
-	while(true)
+	while (true)
 	{
 		doGameTick(arguments);
-		usleep(9000);
+		usleep(15625);
 	}
 }
 int main(int argc, char ** argv)