Adding a get_random_community endpoint. (#5042)

* Adding a get_random_community endpoint.

- Fixes #4698

* Fixing issue from main.

* Adding ListingType to the query.

* More concise query filter.

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 +1,55 @@
+use activitypub_federation::config::Data;
+use actix_web::web::{Json, Query};
+use lemmy_api_common::{
+  community::{CommunityResponse, GetRandomCommunity},
+  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::LemmyResult;
+
+#[tracing::instrument(skip(context))]
+pub async fn get_random_community(
+  data: Query<GetRandomCommunity>,
+  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_community_id(&mut context.pool(), &data.type_).await?;
+
+  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?;
+
+  let discussion_languages =
+    CommunityLanguage::read(&mut context.pool(), random_community_id).await?;
+
+  Ok(Json(CommunityResponse {
+    community_view,
+    discussion_languages,
+  }))
+}

crates/api/src/site/leave_admin.rs

@@ -63,7 +63,7 @@ pub async fn leave_admin(
   let discussion_languages = SiteLanguage::read_local_raw(&mut context.pool()).await?;
   let oauth_providers = OAuthProvider::get_all_public(&mut context.pool()).await?;
   let blocked_urls = LocalSiteUrlBlocklist::get_all(&mut context.pool()).await?;
-  let tagline = Tagline::get_random(&mut context.pool()).await?;
+  let tagline = Tagline::get_random(&mut context.pool()).await.ok();
 
   Ok(Json(GetSiteResponse {
     site_view,

crates/api_common/src/community.rs

@@ -225,3 +225,12 @@ pub struct TransferCommunity {
   pub community_id: CommunityId,
   pub person_id: PersonId,
 }
+
+#[skip_serializing_none]
+#[derive(Debug, Serialize, Deserialize, Clone, Default, PartialEq, Eq, Hash)]
+#[cfg_attr(feature = "full", derive(TS))]
+#[cfg_attr(feature = "full", ts(export))]
+/// Fetches a random community
+pub struct GetRandomCommunity {
+  pub type_: Option<ListingType>,
+}

crates/api_crud/src/site/read.rs

@@ -43,7 +43,7 @@ pub async fn get_site(
       let all_languages = Language::read_all(&mut context.pool()).await?;
       let discussion_languages = SiteLanguage::read_local_raw(&mut context.pool()).await?;
       let blocked_urls = LocalSiteUrlBlocklist::get_all(&mut context.pool()).await?;
-      let tagline = Tagline::get_random(&mut context.pool()).await?;
+      let tagline = Tagline::get_random(&mut context.pool()).await.ok();
       let admin_oauth_providers = OAuthProvider::get_all(&mut context.pool()).await?;
       let oauth_providers =
         OAuthProvider::convert_providers_to_public(admin_oauth_providers.clone());

crates/db_schema/src/impls/community.rs

@@ -30,12 +30,13 @@ use crate::{
     get_conn,
     DbPool,
   },
+  ListingType,
   SubscribedType,
 };
 use chrono::{DateTime, Utc};
 use diesel::{
   deserialize,
-  dsl::{self, exists, insert_into},
+  dsl::{self, exists, insert_into, not},
   pg::Pg,
   result::Error,
   select,
@@ -193,6 +194,30 @@ impl Community {
       .await?;
     Ok(())
   }
+
+  pub async fn get_random_community_id(
+    pool: &mut DbPool<'_>,
+    type_: &Option<ListingType>,
+  ) -> Result<CommunityId, Error> {
+    let conn = &mut get_conn(pool).await?;
+    sql_function!(fn random() -> Text);
+
+    let mut query = community::table
+      .filter(not(community::deleted))
+      .filter(not(community::removed))
+      .into_boxed();
+
+    if let Some(ListingType::Local) = type_ {
+      query = query.filter(community::local);
+    }
+
+    query
+      .select(community::id)
+      .order(random())
+      .limit(1)
+      .first::<CommunityId>(conn)
+      .await
+  }
 }
 
 impl CommunityModerator {

crates/db_schema/src/impls/tagline.rs

@@ -5,7 +5,7 @@ use crate::{
   traits::Crud,
   utils::{get_conn, limit_and_offset, DbPool},
 };
-use diesel::{insert_into, result::Error, ExpressionMethods, OptionalExtension, QueryDsl};
+use diesel::{insert_into, result::Error, ExpressionMethods, QueryDsl};
 use diesel_async::RunQueryDsl;
 
 #[async_trait]
@@ -51,14 +51,9 @@ impl Tagline {
       .await
   }
 
-  pub async fn get_random(pool: &mut DbPool<'_>) -> Result<Option<Self>, Error> {
+  pub async fn get_random(pool: &mut DbPool<'_>) -> Result<Self, Error> {
     let conn = &mut get_conn(pool).await?;
     sql_function!(fn random() -> Text);
-    tagline
-      .order(random())
-      .limit(1)
-      .first::<Self>(conn)
-      .await
-      .optional()
+    tagline.order(random()).limit(1).first::<Self>(conn).await
   }
 }

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))