feat: out-of-box experience (#2)

Reviewed-on: https://git.reya.su/reya/signed/pulls/2

crates/utils/src/lib.rs

@@ -0,0 +1,5 @@
+mod pubkey;
+mod time;
+
+pub use pubkey::shorten_pubkey;
+pub use time::{relative_time, relative_time_secs};

crates/utils/src/pubkey.rs

@@ -0,0 +1,7 @@
+use nostr::prelude::*;
+
+/// Shorten a [`PublicKey`] to `npub1abc...wxyz` form.
+pub fn shorten_pubkey(public_key: PublicKey, len: usize) -> String {
+    let npub = public_key.to_bech32().unwrap();
+    format!("{}...{}", &npub[..(len + 5)], &npub[npub.len() - len..])
+}

crates/utils/src/time.rs

@@ -0,0 +1,48 @@
+use nostr::prelude::*;
+
+/// Format a timestamp as a short relative time (e.g. "3h ago").
+pub fn relative_time(timestamp: Timestamp) -> String {
+    let now = Timestamp::now().as_secs();
+    let secs = now.saturating_sub(timestamp.as_secs());
+
+    if secs < 60 {
+        "just now".to_string()
+    } else if secs < 3600 {
+        format!("{}m ago", secs / 60)
+    } else if secs < 86_400 {
+        format!("{}h ago", secs / 3600)
+    } else if secs < 30 * 86_400 {
+        format!("{}d ago", secs / 86_400)
+    } else if secs < 365 * 86_400 {
+        format!("{}mo ago", secs / (30 * 86_400))
+    } else {
+        format!("{}y ago", secs / (365 * 86_400))
+    }
+}
+
+/// Format a unix timestamp in seconds as a short relative time (e.g. "3h ago").
+pub fn relative_time_secs(secs: i64) -> String {
+    relative_time(Timestamp::from_secs(secs.max(0) as u64))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn formats_relative_time() {
+        let now = Timestamp::now();
+
+        assert_eq!(relative_time(now), "just now");
+        assert_eq!(relative_time(now - 300), "5m ago");
+        assert_eq!(relative_time(now - 7_200), "2h ago");
+        assert_eq!(relative_time(now - 3 * 86_400), "3d ago");
+        assert_eq!(relative_time(now - 60 * 86_400), "2mo ago");
+        assert_eq!(relative_time(now - 800 * 86_400), "2y ago");
+    }
+
+    #[test]
+    fn clamps_future_timestamps() {
+        assert_eq!(relative_time(Timestamp::now() + 600), "just now");
+    }
+}