basic syntax highlighting

1 files changed, 76 insertions, 0 deletions

diff --git a/src/syntax_highlighting.rs b/src/syntax_highlighting.rs
new file mode 100644
index 0000000..8a369da
--- /dev/null
+++ b/src/syntax_highlighting.rs
@@ -0,0 +1,76 @@
+use crate::parse::{Highlight, HighlightKind, Keyword};
+
+pub struct Highlighter {
+    pub enabled: bool,
+}
+
+impl Highlighter {
+    pub fn new() -> Self {
+        Self { enabled: true }
+    }
+
+    pub fn color(&self, h: HighlightKind) -> &[u8] {
+        // TODO: configurable
+        const GREEN: &[u8] = b"\x1b[32m";
+        const BLUE: &[u8] = b"\x1b[36m";
+        const MAGENTA: &[u8] = b"\x1b[95m";
+        const COLOR_RESET: &[u8] = b"\x1b[0m";
+        match h {
+            HighlightKind::Keyword(
+                Keyword::If | Keyword::Elif | Keyword::Else | Keyword::While,
+            ) => GREEN,
+            HighlightKind::Keyword(Keyword::OpenBrace | Keyword::CloseBrace) => BLUE,
+            HighlightKind::String => MAGENTA,
+            HighlightKind::None => COLOR_RESET,
+        }
+    }
+
+    pub fn pretty_print(
+        &self,
+        bytes: &[u8],
+        colors: Vec<Highlight>,
+        stdout: &mut dyn std::io::Write,
+    ) -> std::io::Result<()> {
+        let mut coloring: Vec<_> = colors
+            .into_iter()
+            .flat_map(|hi| {
+                [
+                    (hi.span.start as usize, false, hi.kind),
+                    (hi.span.end as usize, true, hi.kind),
+                ]
+            })
+            .collect();
+        coloring.sort_by_key(|x| (x.0, x.1));
+        let mut coloring = &coloring[..];
+        let mut color_stack = Vec::new();
+
+        let mut current_color = self.color(HighlightKind::None);
+
+        for (i, x) in bytes.iter().cloned().enumerate() {
+            while let Some((k, is_end, kind)) = coloring.first().cloned()
+                && k == i
+            {
+                coloring = &coloring[1..];
+                if is_end {
+                    color_stack.pop();
+                } else {
+                    color_stack.push(kind);
+                }
+
+                let new_color =
+                    self.color(color_stack.last().cloned().unwrap_or(HighlightKind::None));
+
+                if current_color != new_color {
+                    stdout.write_all(new_color)?;
+                    current_color = new_color;
+                }
+            }
+
+            stdout.write_all(&[x])?;
+        }
+
+        stdout.write_all(self.color(HighlightKind::None))?;
+
+        Ok(())
+    }
+}