Adding a get_random_community endpoint.

- Fixes #4698

crates/api/src/community/mod.rs

@@ -3,4 +3,5 @@ pub mod ban;
 pub mod block;
 pub mod follow;
 pub mod hide;
+pub mod random;
 pub mod transfer;

crates/api/src/community/random.rs

@@ -0,0 +1,57 @@
+use activitypub_federation::config::Data;
+use actix_web::web::Json;
+use lemmy_api_common::{
+  community::CommunityResponse,
+  context::LemmyContext,
+  utils::{check_private_instance, is_mod_or_admin_opt},
+};
+use lemmy_db_schema::source::{
+  actor_language::CommunityLanguage,
+  community::Community,
+  local_site::LocalSite,
+};
+use lemmy_db_views::structs::LocalUserView;
+use lemmy_db_views_actor::structs::CommunityView;
+use lemmy_utils::error::{LemmyErrorType, LemmyResult};
+
+#[tracing::instrument(skip(context))]
+pub async fn get_random_community(
+  context: Data<LemmyContext>,
+  local_user_view: Option<LocalUserView>,
+) -> LemmyResult<Json<CommunityResponse>> {
+  let local_site = LocalSite::read(&mut context.pool()).await?;
+
+  check_private_instance(&local_user_view, &local_site)?;
+
+  let local_user = local_user_view.as_ref().map(|u| &u.local_user);
+
+  let random_community_id = Community::get_random_local_community(&mut context.pool())
+    .await?
+    .ok_or(LemmyErrorType::CouldntFindCommunity)?
+    .id;
+
+  let is_mod_or_admin = is_mod_or_admin_opt(
+    &mut context.pool(),
+    local_user_view.as_ref(),
+    Some(random_community_id),
+  )
+  .await
+  .is_ok();
+
+  let community_view = CommunityView::read(
+    &mut context.pool(),
+    random_community_id,
+    local_user,
+    is_mod_or_admin,
+  )
+  .await?
+  .ok_or(LemmyErrorType::CouldntFindCommunity)?;
+
+  let discussion_languages =
+    CommunityLanguage::read(&mut context.pool(), random_community_id).await?;
+
+  Ok(Json(CommunityResponse {
+    community_view,
+    discussion_languages,
+  }))
+}

crates/db_schema/src/impls/community.rs

@@ -35,8 +35,7 @@ use crate::{
 use chrono::{DateTime, Utc};
 use diesel::{
   deserialize,
-  dsl,
-  dsl::{exists, insert_into},
+  dsl::{self, exists, insert_into, not},
   pg::Pg,
   result::Error,
   select,
@@ -196,6 +195,20 @@ impl Community {
       .await?;
     Ok(())
   }
+
+  pub async fn get_random_local_community(pool: &mut DbPool<'_>) -> Result<Option<Self>, Error> {
+    let conn = &mut get_conn(pool).await?;
+    sql_function!(fn random() -> Text);
+    community::table
+      .filter(community::local)
+      .filter(not(community::deleted))
+      .filter(not(community::removed))
+      .order(random())
+      .limit(1)
+      .first::<Self>(conn)
+      .await
+      .optional()
+  }
 }
 
 impl CommunityModerator {

src/api_routes_http.rs

@@ -17,6 +17,7 @@ use lemmy_api::{
     block::block_community,
     follow::follow_community,
     hide::hide_community,
+    random::get_random_community,
     transfer::transfer_community,
   },
   local_user::{
@@ -193,6 +194,7 @@ pub fn config(cfg: &mut web::ServiceConfig, rate_limit: &RateLimitCell) {
           .wrap(rate_limit.message())
           .route("", web::get().to(get_community))
           .route("", web::put().to(update_community))
+          .route("/random", web::get().to(get_random_community))
           .route("/hide", web::put().to(hide_community))
           .route("/list", web::get().to(list_communities))
           .route("/follow", web::post().to(follow_community))