Add flag to log network packets for debugging, --network-debug

Pass -n or --network-debug to print out the packets from the server as
they are received, as well as write to last-packet for later analysis.
Useful when debugging network protocol issues. Builds on #90 #114.

src/main.rs

@@ -166,11 +166,15 @@ impl Game {
 }
 
 #[derive(StructOpt, Debug)]
-#[structopt(name = "basic")]
+#[structopt(name = "Stevenarella")]
 struct Opt {
     /// Server to connect to
     #[structopt(short = "s", long = "server")]
     server: Option<String>,
+
+    /// Log decoded packets received from network
+    #[structopt(short = "n", long = "network-debug")]
+    network_debug: bool,
 }
 
 cfg_if! {
@@ -273,6 +277,10 @@ pub fn main() {
     };
     game.renderer.camera.pos = cgmath::Point3::new(0.5, 13.2, 0.5);
 
+    if opt.network_debug {
+        unsafe { protocol::NETWORK_DEBUG = true; }
+    }
+
     if opt.server.is_some() {
         game.connect_to(&opt.server.unwrap());
     }

src/protocol/mod.rs

@@ -42,6 +42,7 @@ pub const SUPPORTED_PROTOCOLS: [i32; 13] = [477, 452, 451, 404, 340, 316, 315, 2
 
 // TODO: switch to using thread_local storage?, see https://doc.rust-lang.org/std/macro.thread_local.html
 pub static mut CURRENT_PROTOCOL_VERSION: i32 = SUPPORTED_PROTOCOLS[0];
+pub static mut NETWORK_DEBUG: bool = false;
 
 /// Helper macro for defining packets
 #[macro_export]
@@ -923,8 +924,19 @@ impl Conn {
             Direction::Serverbound => Direction::Clientbound,
         };
 
+        let network_debug = unsafe { NETWORK_DEBUG };
+
+        if network_debug {
+            println!("about to parse id={:x}, dir={:?} state={:?}", id, dir, self.state);
+            std::fs::File::create("last-packet")?.write_all(buf.get_ref())?;
+        }
+
         let packet = packet::packet_by_id(self.protocol_version, self.state, dir, id, &mut buf)?;
 
+        if network_debug {
+            println!("packet = {:?}", packet);
+        }
+
         match packet {
             Some(val) => {
                 let pos = buf.position() as usize;