From 53ace3bf57a92da9619f23b896fa6916ec57dc63 Mon Sep 17 00:00:00 2001
From: silverpill <silverpill@firemail.cc>
Date: Sat, 6 Aug 2022 16:17:38 +0000
Subject: [PATCH] Add helper function for creating responses with pagination
 header

---
 src/mastodon_api/mod.rs                 |  3 +-
 src/mastodon_api/notifications/views.rs | 58 +++++++-----------------
 src/mastodon_api/pagination.rs          | 60 +++++++++++++++++++++++++
 3 files changed, 78 insertions(+), 43 deletions(-)
 create mode 100644 src/mastodon_api/pagination.rs

diff --git a/src/mastodon_api/mod.rs b/src/mastodon_api/mod.rs
index 9ef8bbf..dd3a38b 100644
--- a/src/mastodon_api/mod.rs
+++ b/src/mastodon_api/mod.rs
@@ -5,8 +5,9 @@ pub mod markers;
 pub mod media;
 pub mod notifications;
 pub mod oauth;
+mod pagination;
 pub mod search;
 pub mod statuses;
 pub mod timelines;
 
-pub const MASTODON_API_VERSION: &str = "3.0.0";
+const MASTODON_API_VERSION: &str = "3.0.0";
diff --git a/src/mastodon_api/notifications/views.rs b/src/mastodon_api/notifications/views.rs
index a9a5947..2b374a6 100644
--- a/src/mastodon_api/notifications/views.rs
+++ b/src/mastodon_api/notifications/views.rs
@@ -1,33 +1,26 @@
 /// https://docs.joinmastodon.org/methods/notifications/
-use actix_web::{get, web, HttpResponse, Scope as ActixScope};
+use actix_web::{
+    get, web,
+    HttpRequest, HttpResponse,
+    Scope as ActixScope,
+};
 use actix_web_httpauth::extractors::bearer::BearerAuth;
 
 use crate::config::Config;
 use crate::database::{Pool, get_database_client};
 use crate::errors::HttpError;
 use crate::mastodon_api::oauth::auth::get_current_user;
+use crate::mastodon_api::pagination::get_paginated_response;
 use crate::models::notifications::queries::get_notifications;
 use super::types::{ApiNotification, NotificationQueryParams};
 
-fn get_pagination_header(
-    instance_url: &str,
-    last_id: &str,
-) -> String {
-    let next_page_url = format!(
-        "{}/api/v1/notifications?max_id={}",
-        instance_url,
-        last_id
-    );
-    // https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Link
-    format!(r#"<{}>; rel="next""#, next_page_url)
-}
-
 #[get("")]
 async fn get_notifications_view(
     auth: BearerAuth,
     config: web::Data<Config>,
     db_pool: web::Data<Pool>,
     query_params: web::Query<NotificationQueryParams>,
+    request: HttpRequest,
 ) -> Result<HttpResponse, HttpError> {
     let db_client = &**get_database_client(&db_pool).await?;
     let current_user = get_current_user(db_client, auth.token()).await?;
@@ -40,18 +33,15 @@ async fn get_notifications_view(
         .into_iter()
         .map(|item| ApiNotification::from_db(item, &config.instance_url()))
         .collect();
-    let max_index = usize::from(query_params.limit - 1);
-    let response = if let Some(item) = notifications.get(max_index) {
-        let pagination_header = get_pagination_header(&config.instance_url(), &item.id);
-        HttpResponse::Ok()
-            .append_header(("Link", pagination_header))
-            // Link header needs to be exposed
-            // https://github.com/actix/actix-extras/issues/192
-            .append_header(("Access-Control-Expose-Headers", "Link"))
-            .json(notifications)
-    } else {
-        HttpResponse::Ok().json(notifications)
-    };
+    let max_index = usize::from(query_params.limit.saturating_sub(1));
+    let maybe_last_id = notifications.get(max_index)
+        .map(|item| item.id.clone());
+    let response = get_paginated_response(
+        &config.instance_url(),
+        request.uri().path(),
+        notifications,
+        maybe_last_id,
+    );
     Ok(response)
 }
 
@@ -59,19 +49,3 @@ pub fn notification_api_scope() -> ActixScope {
     web::scope("/api/v1/notifications")
         .service(get_notifications_view)
 }
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-
-    const INSTANCE_URL: &str = "https://example.org";
-
-    #[test]
-    fn test_get_next_page_link() {
-        let result = get_pagination_header(INSTANCE_URL, "123");
-        assert_eq!(
-            result,
-            r#"<https://example.org/api/v1/notifications?max_id=123>; rel="next""#,
-        );
-    }
-}
diff --git a/src/mastodon_api/pagination.rs b/src/mastodon_api/pagination.rs
new file mode 100644
index 0000000..bb78c3d
--- /dev/null
+++ b/src/mastodon_api/pagination.rs
@@ -0,0 +1,60 @@
+use actix_web::HttpResponse;
+use serde::Serialize;
+
+fn get_pagination_header(
+    instance_url: &str,
+    path: &str,
+    last_id: &str,
+) -> String {
+    let next_page_url = format!(
+        "{}{}?max_id={}",
+        instance_url,
+        path,
+        last_id
+    );
+    // https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Link
+    format!(r#"<{}>; rel="next""#, next_page_url)
+}
+
+pub fn get_paginated_response(
+    instance_url: &str,
+    path: &str,
+    items: Vec<impl Serialize>,
+    maybe_last_item_id: Option<impl ToString>,
+) -> HttpResponse {
+    if let Some(last_item_id) = maybe_last_item_id {
+        let pagination_header = get_pagination_header(
+            instance_url,
+            path,
+            &last_item_id.to_string(),
+        );
+        HttpResponse::Ok()
+            .append_header(("Link", pagination_header))
+            // Link header needs to be exposed
+            // https://github.com/actix/actix-extras/issues/192
+            .append_header(("Access-Control-Expose-Headers", "Link"))
+            .json(items)
+    } else {
+        HttpResponse::Ok().json(items)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const INSTANCE_URL: &str = "https://example.org";
+
+    #[test]
+    fn test_get_next_page_link() {
+        let result = get_pagination_header(
+            INSTANCE_URL,
+            "/api/v1/notifications",
+            "123",
+        );
+        assert_eq!(
+            result,
+            r#"<https://example.org/api/v1/notifications?max_id=123>; rel="next""#,
+        );
+    }
+}