From 11bfb6836fc12f77ff2fbc993170d81cf4db6b3d Mon Sep 17 00:00:00 2001
From: Tom Alexander <tom@fizz.buzz>
Date: Mon, 23 Oct 2023 22:38:00 -0400
Subject: [PATCH] Include a self-link for the blog.

---
 src/blog_post/convert.rs        | 40 ++++++++++++++++++++++++++++++---
 src/blog_post/render_context.rs |  4 ++++
 2 files changed, 41 insertions(+), 3 deletions(-)

diff --git a/src/blog_post/convert.rs b/src/blog_post/convert.rs
index baed94d..8a03dd6 100644
--- a/src/blog_post/convert.rs
+++ b/src/blog_post/convert.rs
@@ -31,8 +31,14 @@ pub(crate) fn convert_blog_post_page_to_render_context<D: AsRef<Path>, F: AsRef<
         "blog_post.js",
     )?];
     let global_settings = GlobalSettings::new(page.title.clone(), css_files, js_files);
+    let link_to_blog_post = get_web_path(
+        config,
+        output_directory,
+        output_file,
+        output_file.strip_prefix(output_directory)?,
+    )?;
 
-    let ret = RenderBlogPostPage::new(global_settings, page.title.clone());
+    let ret = RenderBlogPostPage::new(global_settings, page.title.clone(), Some(link_to_blog_post));
     Ok(ret)
 }
 
@@ -46,13 +52,15 @@ fn get_web_path<D: AsRef<Path>, F: AsRef<Path>, P: AsRef<Path>>(
     if config.use_relative_paths() {
         let output_directory = output_directory.as_ref();
         let containing_file = containing_file.as_ref();
+        let containing_file_relative_to_output_directory =
+            containing_file.strip_prefix(output_directory)?;
         // Subtracting 1 from the depth to "remove" the file name.
-        let depth_from_web_root = containing_file
-            .strip_prefix(output_directory)?
+        let depth_from_web_root = containing_file_relative_to_output_directory
             .components()
             .count()
             - 1;
         let prefix = "../".repeat(depth_from_web_root);
+        // TODO: It should be possible to strip some of the "../" components based on whether the path_from_web_root goes down the same path as the containing file.
         let final_path = PathBuf::from(prefix).join(path_from_web_root);
         let final_string = final_path
             .as_path()
@@ -73,3 +81,29 @@ fn get_web_path<D: AsRef<Path>, F: AsRef<Path>, P: AsRef<Path>>(
         Ok(final_string)
     }
 }
+
+#[allow(dead_code)]
+fn count_shared_steps<A: AsRef<Path>, B: AsRef<Path>>(left: A, right: B) -> usize {
+    let left = left.as_ref();
+    let right = right.as_ref();
+    left.components()
+        .zip(right.components())
+        .position(|(l, r)| l != r)
+        .unwrap_or_else(|| left.components().count())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_count_shared_steps() {
+        assert_eq!(count_shared_steps("", ""), 0);
+        assert_eq!(count_shared_steps("foo.txt", "foo.txt"), 1);
+        assert_eq!(count_shared_steps("cat/foo.txt", "dog/foo.txt"), 0);
+        assert_eq!(
+            count_shared_steps("foo/bar/baz/lorem.txt", "foo/bar/ipsum/dolar.txt"),
+            2
+        );
+    }
+}
diff --git a/src/blog_post/render_context.rs b/src/blog_post/render_context.rs
index 8015ece..4085b9d 100644
--- a/src/blog_post/render_context.rs
+++ b/src/blog_post/render_context.rs
@@ -31,16 +31,20 @@ pub(crate) struct RenderBlogPostPage {
 
     /// The title that will be shown visibly on the page.
     title: Option<String>,
+
+    self_link: Option<String>,
 }
 
 impl RenderBlogPostPage {
     pub(crate) fn new(
         global_settings: GlobalSettings,
         title: Option<String>,
+        self_link: Option<String>,
     ) -> RenderBlogPostPage {
         RenderBlogPostPage {
             global_settings,
             title,
+            self_link,
         }
     }
 }