feat: first cut on M0 - base structure of project

crates/bds-editor/src/highlight.rs

@@ -0,0 +1,81 @@
+use syntect::highlighting::{Style, ThemeSet};
+use syntect::parsing::{SyntaxReference, SyntaxSet};
+
+/// Syntax highlighter using syntect.
+pub struct Highlighter {
+    syntax_set: SyntaxSet,
+    theme_set: ThemeSet,
+    theme_name: String,
+}
+
+/// A line of highlighted text: spans of (style, text).
+pub type HighlightedLine = Vec<(Style, String)>;
+
+impl Highlighter {
+    pub fn new() -> Self {
+        Self {
+            syntax_set: SyntaxSet::load_defaults_newlines(),
+            theme_set: ThemeSet::load_defaults(),
+            theme_name: "base16-ocean.dark".to_string(),
+        }
+    }
+
+    /// Find the syntax definition for a file extension.
+    pub fn syntax_for_extension(&self, ext: &str) -> &SyntaxReference {
+        self.syntax_set
+            .find_syntax_by_extension(ext)
+            .unwrap_or_else(|| self.syntax_set.find_syntax_plain_text())
+    }
+
+    /// Highlight all lines of the given text for a specific syntax.
+    pub fn highlight_lines(&self, text: &str, syntax: &SyntaxReference) -> Vec<HighlightedLine> {
+        use syntect::easy::HighlightLines;
+
+        let theme = &self.theme_set.themes[&self.theme_name];
+        let mut h = HighlightLines::new(syntax, theme);
+        let mut result = Vec::new();
+
+        for line in text.lines() {
+            let line_with_newline = format!("{line}\n");
+            let ranges = h
+                .highlight_line(&line_with_newline, &self.syntax_set)
+                .unwrap_or_default();
+            let styled: HighlightedLine = ranges
+                .into_iter()
+                .map(|(style, text)| (style, text.to_string()))
+                .collect();
+            result.push(styled);
+        }
+
+        result
+    }
+}
+
+impl Default for Highlighter {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn highlight_markdown() {
+        let h = Highlighter::new();
+        let syntax = h.syntax_for_extension("md");
+        let lines = h.highlight_lines("# Hello\n\nSome text.", syntax);
+        assert_eq!(lines.len(), 3);
+        assert!(!lines[0].is_empty());
+    }
+
+    #[test]
+    fn plain_text_fallback() {
+        let h = Highlighter::new();
+        let syntax = h.syntax_for_extension("nonexistent");
+        // Should not panic, falls back to plain text
+        let lines = h.highlight_lines("hello", syntax);
+        assert_eq!(lines.len(), 1);
+    }
+}