Redirect to ".md" page if client expects Markdown format

Author: hongquan

Cargo.lock

@@ -14,7 +14,7 @@ strip = "debuginfo"
 ammonia = "4.1.3"
 atom_syndication = { version = "0.12.9", features = ["serde"] }
 axum = { version = "0.8.9", features = ["macros"] }
-axum-extra = { version = "0.12.6", features = ["with-rejection"] }
+axum-extra = { version = "0.12.6", features = ["with-rejection", "typed-header"] }
 axum-login = "0.18.0"
 chrono = { version = "0.4.45", features = [
     "serde",
@@ -39,9 +39,11 @@ gel-derive = { git = "https://github.com/geldata/gel-rust" }
 gel-errors = { git = "https://github.com/geldata/gel-rust", features = ["miette"] }
 gel-protocol = { git = "https://github.com/geldata/gel-rust", features = ["all-types"] }
 gel-tokio = { git = "https://github.com/geldata/gel-rust", features = ["miette-errors"] }
+headers-accept = "0.3.0"
 http = "1.4.2"
 indexmap = { version = "2.14.0", features = ["serde"] }
 libpassgen = "1.0.3"
+mediatype = "0.21.0"
 miette = { version = "7.6.0", features = ["fancy", "serde"] }
 mime_guess = "2.0.5"
 minijinja = { version = "2.21.0", features = ["loader", "internal_debug"] }

Cargo.toml

@@ -17,7 +17,10 @@ impl LaxPaging {
     /// The type is NonZeroU16 because our website is small enough for page number
     /// to be fit in u16.
     pub fn get_page_as_number(&self) -> NonZeroU16 {
-        self.page.as_deref().and_then(|s| s.parse().ok()).unwrap_or(NonZeroU16::MIN)
+        self.page
+            .as_deref()
+            .and_then(|s| s.parse().ok())
+            .unwrap_or(NonZeroU16::MIN)
     }
 }
 

src/front/structs.rs

@@ -3,8 +3,12 @@ use std::num::NonZeroU16;
 use axum::extract::{OriginalUri, Path, Query, State};
 use axum::http::StatusCode;
 use axum::response::{Html, Result as AxumResult};
+use axum_extra::TypedHeader;
+use headers_accept::Accept;
 use http::header::LOCATION;
 use indexmap::indexmap;
+use mediatype::media_type;
+use mediatype::names::MARKDOWN;
 use minijinja::{context, value::Value as MJValue};
 use str_macro::str;
 use tower_sessions::Session;
@@ -19,10 +23,14 @@ use crate::stores::blog::{get_detailed_post_by_slug, get_next_post, get_previous
 use crate::types::{AppState, HtmlOrMd, Paginator};
 use crate::utils::html::render_with;
 
+// If the client requests with `Accept: text/markdown` (indicating that it is an AI agent), we will redirect to the ".md" page,
+// which returns content in Markdown format. Otherwise, we serve HTML.
 pub async fn show_post(
     auth_session: AuthSession,
-    Path((_y, _m, slug_ext)): Path<(u16, u16, String)>,
+    Path((y, m, slug_ext)): Path<(u16, u16, String)>,
     Query(params): Query<PostPageParams>,
+    // Value of `Accept` header
+    TypedHeader(accept): TypedHeader<Accept>,
     session: Session,
     State(state): State<AppState>,
 ) -> AxumResult<HtmlOrMd> {
@@ -31,6 +39,17 @@ pub async fn show_post(
         Some((slug, ".md")) => (slug, true),
         _ => (slug_ext.as_str(), false),
     };
+    if !is_md {
+        let available = vec![media_type!(TEXT / HTML), media_type!(TEXT / MARKDOWN)];
+        let preferred_type = accept.negotiate(&available);
+        if preferred_type.map(|t| t.subty) == Some(MARKDOWN) {
+            return Err((
+                StatusCode::TEMPORARY_REDIRECT,
+                format!("/post/{y}/{m}/{slug}.md"),
+            )
+                .into());
+        };
+    };
     let post = get_detailed_post_by_slug(slug, &db)
         .await
         .map_err(PageError::GelQueryError)?