Add App core struct with event-handling and initialization logic for TUI.

crates/owlen-core/src/formatting.rs

@@ -0,0 +1,61 @@
+use crate::types::Message;
+use textwrap::{wrap, Options};
+
+/// Formats messages for display across different clients.
+#[derive(Debug, Clone)]
+pub struct MessageFormatter {
+    wrap_width: usize,
+    show_role_labels: bool,
+    preserve_empty_lines: bool,
+}
+
+impl MessageFormatter {
+    /// Create a new formatter
+    pub fn new(wrap_width: usize, show_role_labels: bool) -> Self {
+        Self {
+            wrap_width: wrap_width.max(20),
+            show_role_labels,
+            preserve_empty_lines: true,
+        }
+    }
+
+    /// Override whether empty lines should be preserved
+    pub fn with_preserve_empty(mut self, preserve: bool) -> Self {
+        self.preserve_empty_lines = preserve;
+        self
+    }
+
+    /// Render a message to a list of visual lines ready for display
+    pub fn format_message(&self, message: &Message) -> Vec<String> {
+        let mut lines = Vec::new();
+
+        let mut content = message.content.trim_end().to_string();
+        if content.is_empty() && self.preserve_empty_lines {
+            content.push(' ');
+        }
+
+        let options = Options::new(self.wrap_width)
+            .break_words(true)
+            .word_separator(textwrap::WordSeparator::UnicodeBreakProperties);
+
+        let wrapped = wrap(&content, &options);
+
+        if self.show_role_labels {
+            let label = format!("{}:", message.role.to_string().to_uppercase());
+            if let Some(first) = wrapped.first() {
+                lines.push(format!("{label} {first}"));
+                for line in wrapped.iter().skip(1) {
+                    lines.push(format!("{:width$} {line}", "", width = label.len()));
+                }
+            } else {
+                lines.push(label);
+            }
+        } else {
+            for line in wrapped {
+                lines.push(line.into_owned());
+            }
+        }
+
+        lines
+    }
+}