From f7de564deb0c310b487c895bbbb66ef7f802ecf5 Mon Sep 17 00:00:00 2001
From: Tom Alexander <tom@fizz.buzz>
Date: Sun, 18 Dec 2022 03:43:13 -0500
Subject: [PATCH] Add a source trait to ensure we can re-create the source
 document using the parsed objects.

---
 src/parser/token.rs | 39 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/src/parser/token.rs b/src/parser/token.rs
index 90e8d90..db1bf19 100644
--- a/src/parser/token.rs
+++ b/src/parser/token.rs
@@ -71,3 +71,42 @@ pub struct Paragraph<'a> {
     pub contents: Vec<TextElement<'a>>,
     pub paragraph_end: &'a str,
 }
+
+pub trait Source<'a> {
+    fn get_source(&'a self) -> &'a str;
+}
+
+impl<'a> Source<'a> for TextElement<'a> {
+    fn get_source(&'a self) -> &'a str {
+        match self {
+            TextElement::Span(elem) => elem.contents,
+            TextElement::Space(elem) => elem.contents,
+            TextElement::LineBreak(elem) => elem.contents,
+            TextElement::Symbol(elem) => elem.contents,
+            TextElement::Bold(elem) => elem.contents,
+            TextElement::Link(elem) => elem.contents,
+        }
+    }
+}
+
+impl<'a> Source<'a> for Paragraph<'a> {
+    fn get_source(&'a self) -> &'a str {
+        if self.contents.is_empty() {
+            return self.paragraph_end;
+        }
+        // TODO: Is there a better way to do this? At a minimum I should be checking that the pointers are contiguous instead of blindly adding their lengths but maybe theres a good way in nom to get both the recognize() value and the parsed values so we can just store a &str to the source.
+        let start = self.contents[0].get_source().as_ptr();
+        let len = self
+            .contents
+            .iter()
+            .map(|text_element| text_element.get_source().len())
+            .sum::<usize>()
+            + self.paragraph_end.len();
+        let full_source = unsafe {
+            let slice = std::slice::from_raw_parts(start, len);
+            std::str::from_utf8(slice)
+                .expect("A token should always be made with valid utf-8 source material.")
+        };
+        full_source
+    }
+}