server: extract open_log_for_writing()

[tattlekey] / server / src / main.rs

diff --git a/server/src/main.rs b/server/src/main.rs
index 071c4b26e74a7fc9103c76fd954c431abefaf9a1..5edadbb9bc3b671244e46f6d24dcb1f471958ab0 100644 (file)
--- a/server/src/main.rs
+++ b/server/src/main.rs
@@ -20,6 +20,7 @@ use std::net::UdpSocket;
 use std::time::{Duration, SystemTime};
 
 const MESSAGE_SIZE: usize = 12;
+const LOGFILENAME: &str = "log.csv";
 
 #[derive(Eq, Debug, Hash, PartialEq, Serialize)]
 struct MessageKey {
@@ -79,8 +80,20 @@ impl Range {
     }
 }
 
+fn open_log_for_writing() -> csv::Writer<std::fs::File> {
+    let log_file_exists = std::path::Path::new(LOGFILENAME).exists();
+    let logfile = std::fs::OpenOptions::new()
+        .create_new(!log_file_exists)
+        .append(true)
+        .open(LOGFILENAME)
+        .expect("Coudln't open log file");
+    csv::WriterBuilder::new()
+        .has_headers(!log_file_exists)
+        .from_writer(logfile)
+}
+
 fn main() {
-    let mut log = csv::Writer::from_writer(std::io::stdout());
+    let mut log = open_log_for_writing();
     let mut presses = HashMap::<MessageKey, Range>::new();
     let socket = UdpSocket::bind("0.0.0.0:29803").expect("couldn't bind to address");
     loop {