time: add time_ago function from Damus iOS

Useful relative time formatting

Signed-off-by: William Casarin <jb55@jb55.com>

src/lib.rs

@@ -10,6 +10,7 @@ mod result;
 mod filter;
 mod ui;
 mod timecache;
+mod time;
 mod frame_history;
 mod timeline;
 

src/time.rs

@@ -0,0 +1,47 @@
+use std::time::{Duration, SystemTime, UNIX_EPOCH};
+
+/// Show a relative time string based on some timestamp
+pub fn time_ago_since(timestamp: u64) -> String {
+    let now = SystemTime::now()
+        .duration_since(UNIX_EPOCH)
+        .expect("Time went backwards")
+        .as_secs();
+    let duration = now.checked_sub(timestamp).unwrap_or(0);
+
+    let years = duration / 31_536_000; // seconds in a year
+    if years >= 1 {
+        return format!("{}yr", years);
+    }
+
+    let months = duration / 2_592_000; // seconds in a month (30.44 days)
+    if months >= 1 {
+        return format!("{}mth", months);
+    }
+
+    let weeks = duration / 604_800; // seconds in a week
+    if weeks >= 1 {
+        return format!("{}wk", weeks);
+    }
+
+    let days = duration / 86_400; // seconds in a day
+    if days >= 1 {
+        return format!("{}d", days);
+    }
+
+    let hours = duration / 3600; // seconds in an hour
+    if hours >= 1 {
+        return format!("{}h", hours);
+    }
+
+    let minutes = duration / 60; // seconds in a minute
+    if minutes >= 1 {
+        return format!("{}m", minutes);
+    }
+
+    let seconds = duration;
+    if seconds >= 3 {
+        return format!("{}s", seconds);
+    }
+
+    "now".to_string()
+}