fix: content negotiation for followers/following — resolve AP router conflict

crates/presentation/src/handlers/feed.rs

@@ -14,9 +14,12 @@ use application::use_cases::profile::get_user_by_username;
 use application::use_cases::search::{search_thoughts, search_users};
 use axum::{
     extract::{Path, Query, State},
+    http::{header, HeaderMap},
+    response::{IntoResponse, Response},
     Json,
 };
 use domain::models::feed::PageParams;
+use domain::value_objects::UserId;
 
 fn to_thought_response(e: &domain::models::feed::FeedEntry) -> ThoughtResponse {
     ThoughtResponse {
@@ -151,34 +154,82 @@ pub async fn search_handler(
 
 pub async fn get_following_handler(
     State(s): State<AppState>,
-    Path(username): Path<String>,
+    Path(param): Path<String>,
     Query(q): Query<PaginationQuery>,
-) -> Result<Json<serde_json::Value>, ApiError> {
-    let user = get_user_by_username(&*s.users, &username).await?;
+    headers: HeaderMap,
+) -> Result<Response, ApiError> {
+    let accept = headers
+        .get(header::ACCEPT)
+        .and_then(|v| v.to_str().ok())
+        .unwrap_or("");
+
+    if accept.contains("application/activity+json") {
+        let user_id = resolve_user_id(&s, &param).await?;
+        let page = q.page().try_into().ok();
+        let json = s
+            .federation
+            .following_collection_json(&user_id, page)
+            .await?;
+        return Ok(([(header::CONTENT_TYPE, "application/activity+json")], json).into_response());
+    }
+
+    let user = get_user_by_username(&*s.users, &param).await?;
     let page = PageParams {
         page: q.page(),
         per_page: q.per_page(),
     };
     let result = get_following(&*s.follows, &user.id, page).await?;
-    Ok(Json(
-        serde_json::json!({ "total": result.total, "items": result.items.iter().map(to_user_response).collect::<Vec<_>>() }),
-    ))
+    Ok(Json(serde_json::json!({
+        "total": result.total,
+        "items": result.items.iter().map(to_user_response).collect::<Vec<_>>()
+    }))
+    .into_response())
 }
 
 pub async fn get_followers_handler(
     State(s): State<AppState>,
-    Path(username): Path<String>,
+    Path(param): Path<String>,
     Query(q): Query<PaginationQuery>,
-) -> Result<Json<serde_json::Value>, ApiError> {
-    let user = get_user_by_username(&*s.users, &username).await?;
+    headers: HeaderMap,
+) -> Result<Response, ApiError> {
+    let accept = headers
+        .get(header::ACCEPT)
+        .and_then(|v| v.to_str().ok())
+        .unwrap_or("");
+
+    if accept.contains("application/activity+json") {
+        let user_id = resolve_user_id(&s, &param).await?;
+        let page = q.page().try_into().ok();
+        let json = s
+            .federation
+            .followers_collection_json(&user_id, page)
+            .await?;
+        return Ok(([(header::CONTENT_TYPE, "application/activity+json")], json).into_response());
+    }
+
+    let user = get_user_by_username(&*s.users, &param).await?;
     let page = PageParams {
         page: q.page(),
         per_page: q.per_page(),
     };
     let result = get_followers(&*s.follows, &user.id, page).await?;
-    Ok(Json(
-        serde_json::json!({ "total": result.total, "items": result.items.iter().map(to_user_response).collect::<Vec<_>>() }),
-    ))
+    Ok(Json(serde_json::json!({
+        "total": result.total,
+        "items": result.items.iter().map(to_user_response).collect::<Vec<_>>()
+    }))
+    .into_response())
+}
+
+async fn resolve_user_id(s: &AppState, param: &str) -> Result<UserId, ApiError> {
+    if let Ok(uuid) = uuid::Uuid::parse_str(param) {
+        s.users
+            .find_by_id(&UserId::from_uuid(uuid))
+            .await?
+            .map(|u| u.id)
+            .ok_or_else(|| ApiError::from(domain::errors::DomainError::NotFound))
+    } else {
+        Ok(get_user_by_username(&*s.users, param).await?.id)
+    }
 }
 
 #[utoipa::path(