Serve the Mews Profile stylesheet from an embedded copy

mews_profile pins both the stylesheet's name and its content, so a site
never actually chooses either; leaving the file itself to be placed in
every content root by hand just gave operators a way to get it stale or
missing. The byte-for-byte copy from mews.page/spec 5.1 now ships in the
binary and resolves `mews-0.1.css` at any depth, matching how a page's
relative link to it resolves, across every protocol that can hit it.

README.md

@@ -42,7 +42,7 @@ site = "smol"
 
 HTTP and Spartan route by the hostname the request carries, falling back to `default_site`; Nex and Gopher carry none, so their listener names one site outright. Every format a listener serves must be compiled in, which `--check` reports. A `.itsybitsy.toml` in a content directory sets rendering options for that directory — `[defaults]` for all its Markdown files, `[page."name.md"]` for one — with no inheritance from parent directories. Editing it re-renders on the next request.
 
-A site can set `mews_profile = true` to render its `xhtmlmp` and `html` output as [Mews Profile](https://mews.page/spec/) pages: the XHTML-MP 1.2 doctype, the conformance marker, the viewport tag and the default stylesheet link, with raw HTML and off-site or `data:` images dropped rather than passed through. Sites sharing one root must agree on this setting, since they share one render cache.
+A site can set `mews_profile = true` to render its `xhtmlmp` and `html` output as [Mews Profile](https://mews.page/spec/) pages: the XHTML-MP 1.2 doctype, the conformance marker, the viewport tag and the default stylesheet link, with raw HTML and off-site or `data:` images dropped rather than passed through. The stylesheet itself is served from an embedded copy, at whatever path the link's `href` resolves to, so there is nothing to place in the content root. Sites sharing one root must agree on this setting, since they share one render cache.
 
 ### Formats and protocols
 

bin/src/proto/gemini.rs

@@ -68,6 +68,9 @@ pub fn serve(listener: &Listener, mut stream: TcpStream) -> Result<()> {
             std::io::copy(&mut file, &mut stream)?;
             Ok(())
         }
+        Ok(Resolution::Found(Resource::Embedded { bytes, media_type })) => {
+            body_response(&mut stream, media_type, bytes)
+        }
         Ok(Resolution::Redirect(location)) => header(&mut stream, 31, &location),
         Ok(Resolution::NotFound) => header(&mut stream, 51, "Not found"),
         Err(err) => {

bin/src/proto/gopher.rs

@@ -55,6 +55,10 @@ pub fn serve(listener: &Listener, mut stream: TcpStream) -> Result<()> {
             std::io::copy(&mut file, &mut stream)?;
             Ok(())
         }
+        Ok(Resolution::Found(Resource::Embedded { bytes, .. })) => {
+            stream.write_all(bytes)?;
+            Ok(())
+        }
         // resolve_flat follows redirects and sub-documents to real content.
         Ok(_) => text(&mut stream, b"Not found\n"),
         Err(err) => {

bin/src/proto/http.rs

@@ -175,6 +175,9 @@ pub fn serve(listener: &Listener, mut stream: TcpStream) -> Result<()> {
             }
             Ok(())
         }
+        Ok(Resolution::Found(Resource::Embedded { bytes, media_type })) => {
+            respond(&mut stream, 200, "OK", media_type, bytes, &[], head_only)
+        }
         Ok(Resolution::Redirect(location)) => respond(
             &mut stream,
             301,

bin/src/proto/nex.rs

@@ -45,6 +45,9 @@ pub fn serve(listener: &Listener, mut stream: TcpStream) -> Result<()> {
             let mut file = std::fs::File::open(&path)?;
             std::io::copy(&mut file, &mut stream)?;
         }
+        Ok(Resolution::Found(Resource::Embedded { bytes, .. })) => {
+            stream.write_all(bytes)?;
+        }
         // resolve_flat follows redirects and sub-documents to real content, so
         // neither reaches here; they are matched for completeness.
         Ok(_) => stream.write_all(b"Not found\n")?,

bin/src/proto/spartan.rs

@@ -73,6 +73,9 @@ pub fn serve(listener: &Listener, mut stream: TcpStream) -> Result<()> {
             std::io::copy(&mut file, &mut stream)?;
             Ok(())
         }
+        Ok(Resolution::Found(Resource::Embedded { bytes, media_type })) => {
+            status(&mut stream, 2, media_type, bytes)
+        }
         Ok(Resolution::Redirect(location)) => status(&mut stream, 3, &location, b""),
         Ok(Resolution::NotFound) => status(&mut stream, 4, "Not found", b""),
         Err(err) => {

core/assets/mews-0.1.css

@@ -0,0 +1,106 @@
+/* Mews Profile default stylesheet 0.1 */
+
+/* Base: light theme */
+body {
+  background-color: #faf8f3;
+  color: #1f1f1f;
+  font-family: "Atkinson Hyperlegible", Verdana, Tahoma, system-ui, sans-serif;
+  font-size: 106%;
+  line-height: 1.5;
+  margin: 0 auto;
+  padding: 1em;
+  max-width: 40em;
+}
+
+h1, h2, h3, h4, h5, h6 {
+  font-weight: bold;
+  line-height: 1.25;
+  margin: 1.6em 0 0.5em 0;
+}
+h1 { font-size: 1.6em; margin-top: 0.5em; }
+h2 { font-size: 1.3em; }
+h3 { font-size: 1.1em; }
+h4, h5, h6 { font-size: 1em; }
+
+p, ul, ol, dl, blockquote, pre, table, address {
+  margin: 0 0 1em 0;
+}
+ul, ol { padding-left: 1.5em; }
+li { margin-bottom: 0.25em; }
+dt { font-weight: bold; }
+dd { margin: 0 0 0.5em 1.5em; }
+
+a { color: #1a4f9c; text-decoration: underline; }
+a:visited { color: #5b2a86; }
+a:focus, a:active { outline: 2px solid #1a4f9c; }
+
+blockquote {
+  margin-left: 0;
+  padding-left: 1em;
+  border-left: 3px solid #c9c4b8;
+}
+
+pre, code, kbd, samp {
+  font-family: "Source Code Pro", Consolas, Menlo, "DejaVu Sans Mono", monospace;
+  font-size: 0.9em;
+}
+pre {
+  background-color: #efece4;
+  padding: 0.75em;
+  overflow: auto;
+}
+
+hr {
+  border: 0;
+  border-top: 1px solid #c9c4b8;
+  margin: 2em 0;
+}
+
+table { border-collapse: collapse; }
+th, td {
+  border: 1px solid #c9c4b8;
+  padding: 0.3em 0.6em;
+  text-align: left;
+  vertical-align: top;
+}
+caption { font-weight: bold; text-align: left; }
+
+img {
+  display: block;
+  max-width: 100%;
+  height: auto;
+  border: 0;
+}
+
+input, select, textarea { font-size: 1em; font-family: inherit; }
+
+/* Body variants: light */
+body.mews-warm { background-color: #fbf4e8; color: #2a2420; }
+body.mews-warm a { color: #8a3d14; }
+body.mews-cool { background-color: #f3f6fa; color: #1c2430; }
+body.mews-cool a { color: #1a4f9c; }
+body.mews-green { background-color: #f2f6ef; color: #1f2a1f; }
+body.mews-green a { color: #24502a; }
+body.mews-mono { background-color: #e8ebe1; color: #1e2219; }
+body.mews-mono a { color: #1e2219; }
+
+/* Dark theme: follows the system setting */
+@media (prefers-color-scheme: dark) {
+  body { background-color: #18191b; color: #e3e1dc; }
+  a { color: #8fb8f5; }
+  a:visited { color: #c9a3f2; }
+  a:focus, a:active { outline-color: #8fb8f5; }
+  blockquote, hr, th, td { border-color: #45464a; }
+  pre { background-color: #222326; }
+
+  body.mews-warm { background-color: #1d1916; color: #e8dfd3; }
+  body.mews-warm a { color: #f0b48a; }
+  body.mews-cool { background-color: #161a20; color: #dde4ee; }
+  body.mews-cool a { color: #8fb8f5; }
+  body.mews-green { background-color: #161b16; color: #dbe6d8; }
+  body.mews-green a { color: #9fd39a; }
+  body.mews-mono { background-color: #1b1d18; color: #c8d0b8; }
+  body.mews-mono a { color: #c8d0b8; }
+}
+
+html { color-scheme: light dark; }

core/src/site.rs

@@ -23,6 +23,16 @@ use crate::render::{Page, Registry, title_from_stem};
 /// always enough; the cap is there so a future rule cannot loop.
 const MAX_FLAT_HOPS: usize = 5;
 
+/// Name a Mews page's stylesheet `<link>` carries (`wap::xhtmlmp::MEWS_HEAD_EXTRA`).
+const MEWS_STYLESHEET_NAME: &str = "mews-0.1.css";
+
+/// The stylesheet itself, byte for byte as published at mews.page/spec (5.1).
+/// Served from here rather than from a file an operator must place in every
+/// site's root: the link's name and content are pinned to the spec version a
+/// site opts into, not something a site chooses, so there is nothing for a
+/// copy on disk to add and every way for it to go stale or go missing.
+const MEWS_STYLESHEET: &[u8] = include_bytes!("../assets/mews-0.1.css");
+
 /// What a request path resolved to.
 #[derive(Debug)]
 pub enum Resolution {
@@ -38,6 +48,9 @@ pub enum Resource {
     Document { url: String, page: Arc<Page> },
     /// A file served byte for byte, streamed rather than buffered.
     Raw { path: PathBuf, media_type: &'static str },
+    /// A byte slice built into the binary, served like `Raw` but with no file
+    /// to open: currently only the Mews Profile stylesheet.
+    Embedded { bytes: &'static [u8], media_type: &'static str },
     /// A sub-document of a page, addressed under the page's own URL.
     ///
     /// Only a paginating format produces these, so whether this slug exists
@@ -110,8 +123,20 @@ impl Site {
     /// | `/foo` | `foo.md`, else `foo/index.md` |
     /// | `/foo.md` | redirects to `/foo` |
     /// | `/img.png` | the file itself, by media type |
+    /// | `/mews-0.1.css` | the embedded stylesheet, when `mews_profile` is set |
     pub fn resolve(&self, url_path: &str) -> Result<Resolution, Error> {
         let Some(clean) = clean_path(url_path) else { return Ok(Resolution::NotFound) };
+
+        // Checked by name only, so the link resolves the same at any depth: a
+        // page under `/foo/bar` carries the same relative `href` as one at the
+        // root, and both must land here rather than on a per-directory copy.
+        if self.mews_profile && clean.rsplit('/').next() == Some(MEWS_STYLESHEET_NAME) {
+            return Ok(Resolution::Found(Resource::Embedded {
+                bytes: MEWS_STYLESHEET,
+                media_type: mime::media_type(Path::new(MEWS_STYLESHEET_NAME)),
+            }));
+        }
+
         let Some(source) = self.file_for(&clean) else { return self.part_for(&clean) };
 
         // `/foo.md` always redirects to its extensionless form, so one
@@ -473,6 +498,28 @@ mod tests {
         assert_not_found(&site, "/nope");
     }
 
+    #[test]
+    fn the_mews_stylesheet_is_served_embedded_when_the_profile_is_on() {
+        let (dir, _site) = fixture();
+        let mews_site =
+            Site::new(dir.path(), registry(), vec!["stub".to_string()], true, Vec::new()).unwrap();
+        for path in ["/mews-0.1.css", "/dir/mews-0.1.css"] {
+            match mews_site.resolve(path).unwrap() {
+                Resolution::Found(Resource::Embedded { bytes, media_type }) => {
+                    assert_eq!(media_type, "text/css; charset=utf-8");
+                    assert_eq!(bytes, MEWS_STYLESHEET, "{path}");
+                }
+                other => panic!("expected the embedded stylesheet at {path}, got {other:?}"),
+            }
+        }
+    }
+
+    #[test]
+    fn the_mews_stylesheet_name_is_an_ordinary_missing_file_when_the_profile_is_off() {
+        let (_dir, site) = fixture();
+        assert_not_found(&site, "/mews-0.1.css");
+    }
+
     #[test]
     fn a_bare_unresolvable_segment_resolves_to_nothing() {
         // The obvious implementation splits on the last `/`, where a bare