implement basic directory listing

README.md

@@ -40,7 +40,7 @@ agate --content path/to/content/ \
 
 All of the command-line arguments are optional.  Run `agate --help` to see the default values used when arguments are omitted.
 
-When a client requests the URL `gemini://example.com/foo/bar`, Agate will respond with the file at `path/to/content/foo/bar`.  If there is a directory at that path, Agate will look for a file named `index.gmi` inside that directory.
+When a client requests the URL `gemini://example.com/foo/bar`, Agate will respond with the file at `path/to/content/foo/bar`.  If there is a directory at that path, Agate will look for a file named `index.gmi` inside that directory. If there is no such file, but a file named `.directory-listing-ok` exists inside that directory, a basic directory listing is displayed. Files whose name starts with a dot (e.g. `.hidden`) are omitted from the list.
 
 [Gemini]: https://gemini.circumlunar.space/
 [Rust]: https://www.rust-lang.org/

src/main.rs

@@ -188,6 +188,34 @@ async fn send_response<W: Write + Unpin>(url: Url, stream: &mut W) -> Result {
             // if the path ends with a slash or the path is empty, the links will work the same
             // without a redirect
             path.push("index.gmi");
+            if path.exists() {
+                // index file exists
+            } else if path.with_file_name(".directory-listing-ok").exists() {
+                // no index file, but directory listing allowed
+                path.pop();
+                log::info!("Listing directory {:?}", path);
+                let entries = std::fs::read_dir(path)?;
+                let listing = entries
+                    .filter(Result::is_ok)
+                    .map(Result::unwrap)
+                    .map(|entry| {
+                        // transform filenames into gemini link lines
+                        let mut name = String::from("=> ");
+                        name += &entry.file_name().to_string_lossy();
+                        if entry.path().is_dir() {
+                            // to avoid redirects link to directories with a trailing slash
+                            name += "/";
+                        }
+                        name + "\n"
+                    })
+                    // filter out files starting with a dot
+                    .filter(|entry| !entry.starts_with("=> ."))
+                    .collect::<String>();
+
+                respond(stream, "20", &["text/gemini"]).await?;
+                stream.write_all(listing.as_bytes()).await?;
+                return Ok(());
+            }
         } else {
             // if client is not redirected, links may not work as expected without trailing slash
             return respond(stream, "31", &[url.as_str(), "/"]).await;