refactor: consolidate truncate functions to use cortex-common (#431)

- Replace local truncate_model_name in billing_client.rs with cortex_common::truncate_model_name
- Replace local truncate_command in permission/prompts.rs with cortex_common::truncate_command
- Replace local truncate_for_display in edit_file.rs with cortex_common::truncate_for_display
- Replace local truncate_string in edit_strategies.rs with cortex_common::truncate_for_display
- Fix test expectations for truncate_model_name (correct max_len calculation)
- Add comment clarifying unicode-aware truncation in text_utils.rs

This reduces code duplication and ensures consistent truncation behavior
across the codebase. All truncation functions now delegate to the centralized
implementations in cortex-common.

Co-authored-by: Droid Agent <droid@factory.ai>

Author: echobt

cortex-common/src/truncate.rs

@@ -139,9 +139,10 @@ pub fn truncate_model_name(name: &str, max_len: usize) -> Cow<'_, str> {
         // Try to keep the model family prefix if possible
         if let Some(slash_pos) = name.find('/') {
             let prefix = &name[..slash_pos + 1];
-            if prefix.len() < max_len.saturating_sub(5) {
-                let remaining = max_len - prefix.len() - 3;
-                let suffix_start = name.len().saturating_sub(remaining);
+            // Check if we have enough room for prefix + "..." + at least 5 chars of suffix
+            if prefix.len() + 3 + 5 <= max_len {
+                let suffix_len = max_len - prefix.len() - 3;
+                let suffix_start = name.len().saturating_sub(suffix_len);
                 return Cow::Owned(format!("{}...{}", prefix, &name[suffix_start..]));
             }
         }
@@ -210,8 +211,16 @@ mod tests {
     #[test]
     fn test_truncate_model_name() {
         assert_eq!(truncate_model_name("gpt-4", 10).as_ref(), "gpt-4");
+        // For max_len=20: prefix "anthropic/" (10) + "..." (3) + suffix (7) = 20
+        // suffix_start = 32 - 7 = 25, so suffix is "0240229"
         assert_eq!(
             truncate_model_name("anthropic/claude-3-opus-20240229", 20).as_ref(),
+            "anthropic/...0240229"
+        );
+        // For max_len=21: prefix "anthropic/" (10) + "..." (3) + suffix (8) = 21
+        // suffix_start = 32 - 8 = 24, so suffix is "20240229"
+        assert_eq!(
+            truncate_model_name("anthropic/claude-3-opus-20240229", 21).as_ref(),
             "anthropic/...20240229"
         );
     }

cortex-engine/src/billing_client.rs

@@ -596,11 +596,7 @@ fn format_number(n: u64) -> String {
 
 /// Truncates a model name to fit display width.
 fn truncate_model_name(name: &str, max_len: usize) -> String {
-    if name.len() <= max_len {
-        name.to_string()
-    } else {
-        format!("{}...", &name[..max_len - 3])
-    }
+    cortex_common::truncate_model_name(name, max_len).into_owned()
 }
 
 // ============================================================================

cortex-engine/src/permission/prompts.rs

@@ -214,11 +214,7 @@ impl fmt::Display for PermissionPrompt {
 
 /// Truncate a command for display.
 fn truncate_command(command: &str, max_len: usize) -> String {
-    if command.len() <= max_len {
-        command.to_string()
-    } else {
-        format!("{}...", &command[..max_len - 3])
-    }
+    cortex_common::truncate_command(command, max_len).into_owned()
 }
 
 /// Format a permission list for display.
@@ -325,9 +321,11 @@ mod tests {
     #[test]
     fn test_truncate_command() {
         assert_eq!(truncate_command("short", 10), "short");
+        // truncate_command tries to cut on word boundaries, so "this is a..." (12 chars)
+        // instead of "this is a ve..." (14 chars) because we look for last space
         assert_eq!(
             truncate_command("this is a very long command", 15),
-            "this is a ve..."
+            "this is a..."
         );
     }
 }

cortex-engine/src/tools/handlers/edit_file.rs

@@ -314,9 +314,5 @@ pub fn diagnose_match(content: &str, search: &str) -> Vec<(&'static str, bool, f
 
 /// Truncate string for display in error messages
 fn truncate_for_display(s: &str, max_len: usize) -> String {
-    if s.len() <= max_len {
-        s.to_string()
-    } else {
-        format!("{}...", &s[..max_len.saturating_sub(3)])
-    }
+    cortex_common::truncate_for_display(s, max_len).into_owned()
 }

cortex-engine/src/tools/handlers/edit_strategies.rs

@@ -984,11 +984,7 @@ fn find_context_match(content: &str, search: &str, context_lines: usize) -> Opti
 
 /// Truncates a string for display purposes.
 fn truncate_string(s: &str, max_len: usize) -> String {
-    if s.len() <= max_len {
-        s.to_string()
-    } else {
-        format!("{}...", &s[..max_len.saturating_sub(3)])
-    }
+    cortex_common::truncate_for_display(s, max_len).into_owned()
 }
 
 // =============================================================================

cortex-tui/src/ui/text_utils.rs

@@ -37,6 +37,8 @@ pub const MIN_TERMINAL_WIDTH: u16 = 40;
 /// assert_eq!(truncate_with_ellipsis("Test", 3), "...");
 /// ```
 pub fn truncate_with_ellipsis(text: &str, max_width: usize) -> String {
+    // Use unicode-aware width calculation for proper handling of
+    // CJK characters and other wide glyphs
     let text_width = UnicodeWidthStr::width(text);
 
     if text_width <= max_width {