From 143d53ed1d795c5c5f6e0773ab3c71700d3ef9a0 Mon Sep 17 00:00:00 2001
From: Scott Worley <scottworley@scottworley.com>
Date: Tue, 10 Oct 2023 15:34:58 -0700
Subject: [PATCH] server: Parse messages

---
 server/src/main.rs | 40 ++++++++++++++++++++++++++++++++++++++--
 1 file changed, 38 insertions(+), 2 deletions(-)

diff --git a/server/src/main.rs b/server/src/main.rs
index 0d4377a..c4c0b19 100644
--- a/server/src/main.rs
+++ b/server/src/main.rs
@@ -18,6 +18,41 @@ use std::net::UdpSocket;
 
 const MESSAGE_SIZE: usize = 12;
 
+#[derive(Debug)]
+struct MessageKey {
+    epoch: u32,
+    device: u16,
+    seq: u16,
+}
+
+#[derive(Debug)]
+struct Message {
+    key: MessageKey,
+    ago: u32,
+}
+
+impl From<&[u8; MESSAGE_SIZE]> for Message {
+    fn from(value: &[u8; MESSAGE_SIZE]) -> Self {
+        Self {
+            key: MessageKey {
+                epoch: u32::from_be_bytes(value[0..=3].try_into().expect("I can't count")),
+                device: u16::from_be_bytes(value[4..=5].try_into().expect("I can't count")),
+                seq: u16::from_be_bytes(value[6..=7].try_into().expect("I can't count")),
+            },
+            ago: u32::from_be_bytes(value[8..=11].try_into().expect("I can't count")),
+        }
+    }
+}
+impl TryFrom<&[u8]> for Message {
+    type Error = std::array::TryFromSliceError;
+    fn try_from(value: &[u8]) -> Result<Self, Self::Error> {
+        match <[u8; MESSAGE_SIZE]>::try_from(value) {
+            Ok(correct_size) => Ok(Message::from(&correct_size)),
+            Err(e) => Err(e),
+        }
+    }
+}
+
 fn main() {
     let socket = UdpSocket::bind("0.0.0.0:29803").expect("couldn't bind to address");
     loop {
@@ -25,12 +60,13 @@ fn main() {
         match socket.recv_from(&mut buf) {
             Err(e) => eprintln!("Didn't receive data: {e}"),
             Ok((number_of_bytes, src_addr)) => {
-                let filled_buf = &mut buf[..number_of_bytes];
+                let filled_buf = &buf[..number_of_bytes];
                 if number_of_bytes != MESSAGE_SIZE {
                     eprintln!("Ignoring short message ({number_of_bytes}) from {src_addr}");
                     continue;
                 }
-                println!("Got packet from {src_addr}: {filled_buf:?}");
+                let message = Message::try_from(filled_buf).expect("I can't count");
+                println!("Got packet from {src_addr}: {message:?}");
             }
         }
     }
-- 
2.44.1