feat: implement breaking change input

src/prompts/prompter.rs

@@ -5,8 +5,10 @@
 //! [`CommitWorkflow`](super::CommitWorkflow) to use real interactive prompts
 //! in production while accepting mock implementations in tests.
 
+use inquire::{Confirm, Text};
+
 use crate::{
-    commit::types::{CommitType, Description, Scope},
+    commit::types::{BreakingChange, CommitType, Description, Scope},
     error::Error,
 };
 
@@ -24,6 +26,9 @@ pub trait Prompter: Send + Sync {
     /// Prompt the user to input a required description
     fn input_description(&self) -> Result<Description, Error>;
 
+    /// Prompt the user for breaking change
+    fn input_breaking_change(&self) -> Result<BreakingChange, Error>;
+
     /// Prompt the user to confirm applying the commit message
     fn confirm_apply(&self, message: &str) -> Result<bool, Error>;
 
@@ -34,6 +39,18 @@ pub trait Prompter: Send + Sync {
     fn emit_message(&self, msg: &str);
 }
 
+fn format_message_box(message: &str) -> String {
+    let preview_width = 72 + 2; // max width + space padding
+    let mut lines: Vec<String> = Vec::new();
+    lines.push(format!("┌{}┐", "─".repeat(preview_width)));
+    for line in message.split("\n") {
+        let padding = 72_usize.saturating_sub(line.chars().count());
+        lines.push(format!("│ {line}{:padding$} │", ""));
+    }
+    lines.push(format!("└{}┘", "─".repeat(preview_width)));
+    lines.join("\n")
+}
+
 /// Production implementation of [`Prompter`] using the `inquire` crate
 #[derive(Debug)]
 pub struct RealPrompts;
@@ -137,18 +154,30 @@ impl Prompter for RealPrompts {
         }
     }
 
+    fn input_breaking_change(&self) -> Result<BreakingChange, Error> {
+        if !Confirm::new("Does this revision include a breaking change?")
+            .with_default(false)
+            .prompt()
+            .map_err(|_| Error::Cancelled)?
+        {
+            return Ok(BreakingChange::No);
+        }
+        let answer = Text::new("Enter the description of the breaking change:")
+            .with_help_message("Enter an empty message to skip creating a message footer")
+            .prompt()
+            .map_err(|_| Error::Cancelled)?;
+        let trimmed = answer.trim();
+        Ok(trimmed.into())
+    }
+
     fn confirm_apply(&self, message: &str) -> Result<bool, Error> {
         use inquire::Confirm;
 
         // Show preview
-        println!();
-        println!("📝 Commit Message Preview:");
-        println!("┌────────────────────────────────────────────────────────────────────────┐");
-        // Pad with spaces to fill the box
-        let padding = 72_usize.saturating_sub(message.chars().count()) - 1;
-        println!("│ {message}{:padding$}│", "");
-        println!("└────────────────────────────────────────────────────────────────────────┘");
-        println!();
+        println!(
+            "\n📝 Commit Message Preview:\n{}\n",
+            format_message_box(message)
+        );
 
         // Get confirmation
         Confirm::new("Apply this commit message?")
@@ -174,4 +203,71 @@ mod tests {
         fn _accepts_prompter(_p: impl Prompter) {}
         _accepts_prompter(real);
     }
+
+    /// Top border uses exactly preview_width (74) dashes; bottom likewise
+    #[test]
+    fn format_message_box_borders() {
+        let result = format_message_box("hello");
+        let lines: Vec<&str> = result.split('\n').collect();
+        let dashes = "─".repeat(74);
+        assert_eq!(lines[0], format!("┌{dashes}┐"));
+        assert_eq!(lines[lines.len() - 1], format!("└{dashes}┘"));
+    }
+
+    /// A single-line message produces exactly 3 rows: top, content, bottom
+    #[test]
+    fn format_message_box_single_line_row_count() {
+        let result = format_message_box("feat: add login");
+        assert_eq!(result.split('\n').count(), 3);
+    }
+
+    /// A message with one `\n` produces 4 rows: top, two content, bottom
+    #[test]
+    fn format_message_box_multi_line_row_count() {
+        let result = format_message_box("feat: add login\nsecond line");
+        assert_eq!(result.split('\n').count(), 4);
+    }
+
+    /// A breaking-change message (`\n\n`) produces an empty content row for the blank line
+    #[test]
+    fn format_message_box_blank_separator_line() {
+        let msg = "feat!: drop old API\n\nBREAKING CHANGE: removed";
+        let result = format_message_box(msg);
+        assert_eq!(result.split('\n').count(), 5); // top + 3 content + bottom
+    }
+
+    /// All output rows have identical char counts (the box is rectangular)
+    #[test]
+    fn format_message_box_all_rows_same_width() {
+        let msg = "feat(auth): add login\n\nBREAKING CHANGE: old API removed";
+        let result = format_message_box(msg);
+        let widths: Vec<usize> = result.split('\n').map(|l| l.chars().count()).collect();
+        let expected = widths[0];
+        assert!(
+            widths.iter().all(|&w| w == expected),
+            "rows have differing widths: {:?}",
+            widths
+        );
+    }
+
+    /// An empty message produces a single fully-padded content row
+    #[test]
+    fn format_message_box_empty_message() {
+        let result = format_message_box("");
+        let lines: Vec<&str> = result.split('\n').collect();
+        assert_eq!(lines.len(), 3);
+        // "│ " + 72 spaces + " │" = 76 chars
+        let expected = format!("│ {:72} │", "");
+        assert_eq!(lines[1], expected);
+    }
+
+    /// A line of exactly 72 characters leaves no right-hand padding
+    #[test]
+    fn format_message_box_line_exactly_72_chars() {
+        let line_72 = "a".repeat(72);
+        let result = format_message_box(&line_72);
+        let lines: Vec<&str> = result.split('\n').collect();
+        let expected = format!("│ {line_72} │");
+        assert_eq!(lines[1], expected);
+    }
 }