feat(tui): add syntax highlighting for code panes using syntect and a new highlight module

crates/owlen-tui/Cargo.toml

@@ -27,6 +27,8 @@ tree-sitter = "0.20"
 tree-sitter-rust = "0.20"
 dirs = { workspace = true }
 toml = { workspace = true }
+syntect = "5.3"
+once_cell = "1.19"
 
 # Async runtime
 tokio = { workspace = true }

crates/owlen-tui/src/highlight.rs

@@ -0,0 +1,102 @@
+use once_cell::sync::Lazy;
+use ratatui::style::{Color as TuiColor, Modifier, Style as TuiStyle};
+use std::path::{Path, PathBuf};
+use syntect::easy::HighlightLines;
+use syntect::highlighting::{FontStyle, Style as SynStyle, Theme, ThemeSet};
+use syntect::parsing::{SyntaxReference, SyntaxSet};
+
+static SYNTAX_SET: Lazy<SyntaxSet> = Lazy::new(SyntaxSet::load_defaults_newlines);
+static THEME_SET: Lazy<ThemeSet> = Lazy::new(ThemeSet::load_defaults);
+static THEME: Lazy<Theme> = Lazy::new(|| {
+    THEME_SET
+        .themes
+        .get("base16-ocean.dark")
+        .cloned()
+        .or_else(|| THEME_SET.themes.values().next().cloned())
+        .unwrap_or_default()
+});
+
+fn select_syntax(path_hint: Option<&Path>) -> &'static SyntaxReference {
+    if let Some(path) = path_hint {
+        if let Ok(Some(syntax)) = SYNTAX_SET.find_syntax_for_file(path) {
+            return syntax;
+        }
+        if let Some(ext) = path.extension().and_then(|ext| ext.to_str())
+            && let Some(syntax) = SYNTAX_SET.find_syntax_by_extension(ext)
+        {
+            return syntax;
+        }
+        if let Some(name) = path.file_name().and_then(|name| name.to_str())
+            && let Some(syntax) = SYNTAX_SET.find_syntax_by_token(name)
+        {
+            return syntax;
+        }
+    }
+
+    SYNTAX_SET.find_syntax_plain_text()
+}
+
+fn path_hint_from_components(absolute: Option<&Path>, display: Option<&str>) -> Option<PathBuf> {
+    if let Some(abs) = absolute {
+        return Some(abs.to_path_buf());
+    }
+    display.map(PathBuf::from)
+}
+
+fn style_from_syntect(style: SynStyle) -> TuiStyle {
+    let mut tui_style = TuiStyle::default().fg(TuiColor::Rgb(
+        style.foreground.r,
+        style.foreground.g,
+        style.foreground.b,
+    ));
+
+    let mut modifiers = Modifier::empty();
+    if style.font_style.contains(FontStyle::BOLD) {
+        modifiers |= Modifier::BOLD;
+    }
+    if style.font_style.contains(FontStyle::ITALIC) {
+        modifiers |= Modifier::ITALIC;
+    }
+    if style.font_style.contains(FontStyle::UNDERLINE) {
+        modifiers |= Modifier::UNDERLINED;
+    }
+
+    if !modifiers.is_empty() {
+        tui_style = tui_style.add_modifier(modifiers);
+    }
+
+    tui_style
+}
+
+pub fn build_highlighter(
+    absolute: Option<&Path>,
+    display: Option<&str>,
+) -> HighlightLines<'static> {
+    let hint_path = path_hint_from_components(absolute, display);
+    let syntax = select_syntax(hint_path.as_deref());
+    HighlightLines::new(syntax, &THEME)
+}
+
+pub fn highlight_line(
+    highlighter: &mut HighlightLines<'static>,
+    line: &str,
+) -> Vec<(TuiStyle, String)> {
+    let mut segments = Vec::new();
+    match highlighter.highlight_line(line, &SYNTAX_SET) {
+        Ok(result) => {
+            for (style, piece) in result {
+                let tui_style = style_from_syntect(style);
+                segments.push((tui_style, piece.to_string()));
+            }
+        }
+        Err(_) => {
+            segments.push((TuiStyle::default(), line.to_string()));
+        }
+    }
+
+    if segments.is_empty() {
+        segments.push((TuiStyle::default(), String::new()));
+    }
+
+    segments
+}

crates/owlen-tui/src/lib.rs

@@ -17,6 +17,7 @@ pub mod code_app;
 pub mod commands;
 pub mod config;
 pub mod events;
+pub mod highlight;
 pub mod model_info_panel;
 pub mod slash;
 pub mod state;

crates/owlen-tui/src/ui.rs

@@ -12,6 +12,7 @@ use unicode_segmentation::UnicodeSegmentation;
 use unicode_width::UnicodeWidthStr;
 
 use crate::chat_app::{ChatApp, HELP_TAB_COUNT, MessageRenderContext, ModelSelectorItemKind};
+use crate::highlight;
 use crate::state::{
     CodePane, EditorTab, FileFilterMode, FileNode, LayoutNode, PaletteGroup, PaneId,
     RepoSearchRowKind, SplitAxis, VisibleFileEntry,
@@ -2338,6 +2339,8 @@ fn render_code_pane(
                 .add_modifier(Modifier::ITALIC),
         )));
     } else {
+        let mut highlighter =
+            highlight::build_highlighter(pane.absolute_path(), pane.display_path());
         for (idx, content) in pane.lines.iter().enumerate() {
             let number = format!("{:>4} ", idx + 1);
             let mut spans = vec![Span::styled(
@@ -2347,12 +2350,22 @@ fn render_code_pane(
                     .add_modifier(Modifier::DIM),
             )];
 
+            let segments = highlight::highlight_line(&mut highlighter, content);
+            if segments.is_empty() {
                 let mut line_style = Style::default().fg(theme.text);
                 if !is_active {
                     line_style = line_style.add_modifier(Modifier::DIM);
                 }
-
                 spans.push(Span::styled(content.clone(), line_style));
+            } else {
+                for (segment_style, text) in segments {
+                    let mut style = segment_style;
+                    if !is_active {
+                        style = style.add_modifier(Modifier::DIM);
+                    }
+                    spans.push(Span::styled(text, style));
+                }
+            }
             lines.push(Line::from(spans));
         }
     }