initial commit

.gitignore

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+/target

Cargo.lock

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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "timer"
+version = "0.1.0"

Cargo.toml

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+[package]
+name = "timer"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

src/main.rs

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+use std::io::Write;
+
+const HOUR: u64 = 60 * 60;
+const MINUTE: u64 = 60;
+
+fn main() {
+    let Some(arg) = std::env::args().nth(1) else {
+        eprintln!("Missing time argument");
+        return;
+    };
+    let start = std::time::Instant::now();
+
+    let parts: Vec<&str> = arg.split(':').collect();
+    let secs = match parts[..] {
+        [s] => s.parse::<u64>().expect("parse seconds"),
+        [m, s] => {
+            s.parse::<u64>().expect("parse seconds")
+                + m.parse::<u64>().expect("parse minutes") * MINUTE
+        }
+        [h, m, s] => {
+            s.parse::<u64>().expect("parse seconds")
+                + m.parse::<u64>().expect("parse minutes") * MINUTE
+                + h.parse::<u64>().expect("parse hours") * HOUR
+        }
+        _ => {
+            eprintln!("Invalid time format: {arg}");
+            return;
+        }
+    };
+    let show_hours = secs > HOUR;
+    let duration = std::time::Duration::from_secs(secs);
+    let stop = start + duration;
+    let mut now = std::time::Instant::now();
+
+    while now < stop {
+        let rem = stop - now;
+        let rems = rem.as_secs();
+        let h = rems / HOUR;
+        let m = (rems / MINUTE) % 60;
+        let s = rems % 60;
+        if show_hours {
+            print!("\r{h:02}:{m:02}:{s:02}");
+        } else {
+            print!("\r{m:02}:{s:02}");
+        }
+        std::io::stdout().lock().flush().expect("stdout lock");
+        std::thread::sleep(std::time::Duration::from_secs(1));
+        now = std::time::Instant::now();
+    }
+    println!();
+}