Split markdown parsing and highlighting

src/markdown/span.rs

@@ -3,6 +3,8 @@ use std::{
     ops::{Deref, Range},
 };
 
+use eyre::{bail, eyre};
+
 #[derive(Clone, Eq, PartialEq)]
 pub struct Span<'a> {
     complete_str: &'a str,
@@ -17,6 +19,13 @@ impl<'a> Span<'a> {
         }
     }
 
+    pub const fn empty() -> Self {
+        Span {
+            complete_str: "",
+            range: 0..0,
+        }
+    }
+
     pub fn get(&self, slice: Range<usize>) -> Option<Self> {
         let start = self.range.start.checked_add(slice.start)?;
         let end = self.range.start.checked_add(slice.end)?;
@@ -41,26 +50,49 @@ impl<'a> Span<'a> {
         Some((head, tail))
     }
 
+    pub fn trim_end_matches(&self, p: &str) -> Self {
+        if !self.ends_with(p) {
+            return self.clone();
+        }
+
+        Self {
+            range: self.range.start..self.range.end - p.len(),
+            complete_str: self.complete_str,
+        }
+    }
+
     /// Try to merge the spans.
     ///
+    /// If either spans is empty, this just returns the other one.
     /// This only works if spans are pointing into the same backing buffer, and are adjacent.
-    pub fn try_merge(&self, other: &Self) -> Option<Self> {
+    pub fn try_merge(&self, other: &Self) -> eyre::Result<Self> {
+        if self.is_empty() {
+            return Ok(other.clone());
+        }
+
+        if other.is_empty() {
+            return Ok(self.clone());
+        }
+
         if self.complete_str.as_ptr() != other.complete_str.as_ptr() {
-            return None;
+            bail!("Can't merge different strings");
         }
 
         if self.range.end == other.range.start {
-            Some(Self {
+            Ok(Self {
                 range: self.range.start..other.range.end,
                 ..*self
             })
         } else if self.range.start == other.range.end {
-            Some(Self {
+            Ok(Self {
                 range: other.range.start..self.range.end,
                 ..*self
             })
         } else {
-            None
+            Err(eyre!("String: {:?}", self.complete_str)
+                .wrap_err(eyre!("Span 2: {:?}", other.deref()))
+                .wrap_err(eyre!("Span 1: {:?}", self.deref()))
+                .wrap_err("Can't merge disjoint string spans"))
         }
     }
 }