move duration-formatting to a separate function and add tests for that

src/context.rs

@@ -9,6 +9,7 @@ use crate::chat::*;
 use crate::config::Config;
 use crate::constants::*;
 use crate::contact::*;
+use crate::dc_tools::duration_to_str;
 use crate::error::*;
 use crate::events::Event;
 use crate::imap::*;
@@ -314,11 +315,8 @@ impl Context {
         );
         res.insert("fingerprint", fingerprint_str);
 
-        let elapsed = self.creation_time.elapsed().as_secs();
-        let hours = elapsed / 3600;
-        let minutes = elapsed % 3600 / 60;
-        let seconds = elapsed % 3600 % 60;
-        res.insert("uptime", format!("{}h {}m {}s", hours, minutes, seconds));
+        let elapsed = self.creation_time.elapsed();
+        res.insert("uptime", duration_to_str(elapsed.unwrap_or_default()));
 
         res
     }

src/dc_tools.rs

@@ -5,7 +5,7 @@ use core::cmp::{max, min};
 use std::borrow::Cow;
 use std::path::{Path, PathBuf};
 use std::str::FromStr;
-use std::time::SystemTime;
+use std::time::{Duration, SystemTime};
 use std::{fmt, fs};
 
 use chrono::{Local, TimeZone};
@@ -75,6 +75,14 @@ pub fn dc_timestamp_to_str(wanted: i64) -> String {
     ts.format("%Y.%m.%d %H:%M:%S").to_string()
 }
 
+pub fn duration_to_str(duration: Duration) -> String {
+    let secs = duration.as_secs();
+    let h = secs / 3600;
+    let m = secs % 3600 / 60;
+    let s = secs % 3600 % 60;
+    format!("{}h {}m {}s", h, m, s)
+}
+
 pub(crate) fn dc_gm2local_offset() -> i64 {
     /* returns the offset that must be _added_ to an UTC/GMT-time to create the localtime.
     the function may return negative values. */
@@ -854,4 +862,37 @@ mod tests {
         let next = dc_smeared_time(&t.ctx);
         assert!((start + count - 1) < next);
     }
+
+    #[test]
+    fn test_duration_to_str() {
+        assert_eq!(duration_to_str(Duration::from_secs(0)), "0h 0m 0s");
+        assert_eq!(duration_to_str(Duration::from_secs(59)), "0h 0m 59s");
+        assert_eq!(duration_to_str(Duration::from_secs(60)), "0h 1m 0s");
+        assert_eq!(duration_to_str(Duration::from_secs(61)), "0h 1m 1s");
+        assert_eq!(duration_to_str(Duration::from_secs(59 * 60)), "0h 59m 0s");
+        assert_eq!(
+            duration_to_str(Duration::from_secs(59 * 60 + 59)),
+            "0h 59m 59s"
+        );
+        assert_eq!(
+            duration_to_str(Duration::from_secs(59 * 60 + 60)),
+            "1h 0m 0s"
+        );
+        assert_eq!(
+            duration_to_str(Duration::from_secs(2 * 60 * 60 + 59 * 60 + 59)),
+            "2h 59m 59s"
+        );
+        assert_eq!(
+            duration_to_str(Duration::from_secs(2 * 60 * 60 + 59 * 60 + 60)),
+            "3h 0m 0s"
+        );
+        assert_eq!(
+            duration_to_str(Duration::from_secs(3 * 60 * 60 + 59)),
+            "3h 0m 59s"
+        );
+        assert_eq!(
+            duration_to_str(Duration::from_secs(3 * 60 * 60 + 60)),
+            "3h 1m 0s"
+        );
+    }
 }