Extract shared display formatting into keep-core (#288)

keep-core/src/display.rs

@@ -0,0 +1,95 @@
+// SPDX-FileCopyrightText: © 2026 PrivKey LLC
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+use chrono::{DateTime, Utc};
+
+/// Truncate a string to `prefix` leading chars + `...` + `suffix` trailing chars.
+///
+/// Returns the original string unchanged if it is short enough or not ASCII.
+pub fn truncate_str(s: &str, prefix: usize, suffix: usize) -> String {
+    let guard = prefix + suffix + 3;
+    if !s.is_ascii() || s.len() <= guard {
+        return s.to_owned();
+    }
+    format!("{}...{}", &s[..prefix], &s[s.len() - suffix..])
+}
+
+/// Format a Unix timestamp as `"2024-01-15 10:30 UTC"`.
+pub fn format_timestamp(ts: i64) -> String {
+    DateTime::<Utc>::from_timestamp(ts, 0)
+        .map(|dt| dt.format("%Y-%m-%d %H:%M UTC").to_string())
+        .unwrap_or_else(|| ts.to_string())
+}
+
+/// Format a Unix timestamp as `"Jan 15, 2024 10:30:00"` (detailed, no timezone label).
+pub fn format_timestamp_detailed(ts: i64) -> String {
+    DateTime::<Utc>::from_timestamp(ts, 0)
+        .map(|dt| dt.format("%b %d, %Y %H:%M:%S").to_string())
+        .unwrap_or_else(|| ts.to_string())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn truncate_short_string_unchanged() {
+        assert_eq!(truncate_str("npub1abc", 12, 6), "npub1abc");
+    }
+
+    #[test]
+    fn truncate_non_ascii_unchanged() {
+        let s = "npub1こんにちは世界abc";
+        assert_eq!(truncate_str(s, 12, 6), s);
+    }
+
+    #[test]
+    fn truncate_at_guard_boundary_unchanged() {
+        // prefix=8, suffix=6, guard=17; string of length 17 should be unchanged
+        let s = "a".repeat(17);
+        assert_eq!(truncate_str(&s, 8, 6), s);
+    }
+
+    #[test]
+    fn truncate_one_over_guard() {
+        let s = "a".repeat(18);
+        let result = truncate_str(&s, 8, 6);
+        assert_eq!(result, "aaaaaaaa...aaaaaa");
+        assert_eq!(result.len(), 17);
+    }
+
+    #[test]
+    fn truncate_npub_style() {
+        let npub = "npub1aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaabbbbbb";
+        let result = truncate_str(npub, 12, 6);
+        assert_eq!(&result[..12], "npub1aaaaaaa");
+        assert!(result.contains("..."));
+        assert_eq!(&result[result.len() - 6..], "bbbbbb");
+    }
+
+    #[test]
+    fn truncate_hex_style() {
+        let hex = "abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789";
+        let result = truncate_str(hex, 8, 6);
+        assert_eq!(&result[..8], "abcdef01");
+        assert!(result.contains("..."));
+        assert_eq!(&result[result.len() - 6..], "456789");
+    }
+
+    #[test]
+    fn format_timestamp_valid() {
+        let result = format_timestamp(1705314600);
+        assert_eq!(result, "2024-01-15 10:30 UTC");
+    }
+
+    #[test]
+    fn format_timestamp_zero() {
+        assert_eq!(format_timestamp(0), "1970-01-01 00:00 UTC");
+    }
+
+    #[test]
+    fn format_timestamp_detailed_valid() {
+        let result = format_timestamp_detailed(1705314600);
+        assert_eq!(result, "Jan 15, 2024 10:30:00");
+    }
+}

keep-core/src/lib.rs

@@ -38,6 +38,8 @@ pub mod audit;
 pub mod backend;
 /// Cryptographic primitives for encryption, key derivation, and hashing.
 pub mod crypto;
+/// Display formatting helpers for truncation and timestamps.
+pub mod display;
 /// Multi-source entropy mixing for defense-in-depth randomness.
 pub mod entropy;
 /// Error types and result aliases.

keep-desktop/src/screen/bunker.rs

@@ -21,14 +21,7 @@ pub struct ConnectedClient {
 
 impl ConnectedClient {
     pub fn truncated_pubkey(&self) -> String {
-        if self.pubkey.len() <= 16 {
-            return self.pubkey.clone();
-        }
-        format!(
-            "{}...{}",
-            &self.pubkey[..8],
-            &self.pubkey[self.pubkey.len() - 6..]
-        )
+        keep_core::display::truncate_str(&self.pubkey, 8, 6)
     }
 
     pub fn permission_labels(&self) -> Vec<&'static str> {

keep-desktop/src/screen/mod.rs

@@ -16,22 +16,13 @@ pub mod signing_audit;
 pub mod unlock;
 pub mod wallet;
 
-use chrono::{DateTime, Utc};
-
 use crate::message::Message;
 use layout::{NavItem, SidebarState};
 
-pub fn format_timestamp(ts: i64) -> String {
-    DateTime::<Utc>::from_timestamp(ts, 0)
-        .map(|dt| dt.format("%Y-%m-%d %H:%M UTC").to_string())
-        .unwrap_or_else(|| ts.to_string())
-}
+pub use keep_core::display::format_timestamp;
 
 pub fn truncate_npub(npub: &str) -> String {
-    if !npub.is_ascii() || npub.len() <= 20 {
-        return npub.to_owned();
-    }
-    format!("{}...{}", &npub[..12], &npub[npub.len() - 6..])
+    keep_core::display::truncate_str(npub, 12, 6)
 }
 
 pub enum Screen {

keep-desktop/src/screen/signing_audit.rs

@@ -263,9 +263,7 @@ impl SigningAuditScreen {
             );
         }
 
-        let timestamp = chrono::DateTime::from_timestamp(entry.timestamp, 0)
-            .map(|dt| dt.format("%b %d, %Y %H:%M:%S").to_string())
-            .unwrap_or_else(|| entry.timestamp.to_string());
+        let timestamp = keep_core::display::format_timestamp_detailed(entry.timestamp);
 
         let time_text = text(timestamp)
             .size(theme::size::TINY)
@@ -280,10 +278,7 @@ impl SigningAuditScreen {
 }
 
 fn truncate_hex(s: &str) -> String {
-    if s.len() <= 20 || !s.is_ascii() {
-        return s.to_string();
-    }
-    format!("{}...{}", &s[..8], &s[s.len() - 6..])
+    keep_core::display::truncate_str(s, 8, 6)
 }
 
 fn format_request_type(rt: &str) -> String {

keep-desktop/src/screen/wallet.rs

@@ -3,7 +3,6 @@
 
 use std::collections::HashMap;
 
-use chrono::{DateTime, Utc};
 use iced::widget::{button, column, container, row, scrollable, text, text_input, Space};
 use iced::{Alignment, Element, Length};
 use keep_frost_net::AnnouncedXpub;
@@ -483,10 +482,8 @@ impl WalletScreen {
                 .color(theme::color::TEXT_DIM);
 
             let created = i64::try_from(entry.created_at)
-                .ok()
-                .and_then(|ts| DateTime::<Utc>::from_timestamp(ts, 0))
-                .map(|dt| dt.format("%Y-%m-%d %H:%M UTC").to_string())
-                .unwrap_or_else(|| entry.created_at.to_string());
+                .map(keep_core::display::format_timestamp)
+                .unwrap_or_else(|_| entry.created_at.to_string());
             let created_text = text(format!("Created: {created}"))
                 .size(theme::size::SMALL)
                 .color(theme::color::TEXT_MUTED);

keep-mobile/src/keep_mobile.udl

@@ -4,6 +4,10 @@
 namespace keep_mobile {
     [Throws=KeepMobileError]
     ParsedBunkerUrl parse_bunker_url(string url);
+
+    string format_timestamp(i64 ts);
+    string format_timestamp_detailed(i64 ts);
+    string truncate_str(string s, u32 prefix_len, u32 suffix_len);
 };
 
 [Error]

keep-mobile/src/lib.rs

@@ -33,6 +33,18 @@ pub use types::{
     SignRequestMetadata, ThresholdConfig, WalletDescriptorInfo,
 };
 
+pub fn format_timestamp(ts: i64) -> String {
+    keep_core::display::format_timestamp(ts)
+}
+
+pub fn format_timestamp_detailed(ts: i64) -> String {
+    keep_core::display::format_timestamp_detailed(ts)
+}
+
+pub fn truncate_str(s: String, prefix_len: u32, suffix_len: u32) -> String {
+    keep_core::display::truncate_str(&s, prefix_len as usize, suffix_len as usize)
+}
+
 use keep_core::frost::{
     ShareExport, ShareMetadata, SharePackage, ThresholdConfig as CoreThresholdConfig, TrustedDealer,
 };