wip: start adding an ActivityCursorIter

egg-mode-rs · Jul 21, 2020 · 7e8468f · 7e8468f
1 parent 05be063
commit 7e8468f
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Showing 4 changed files with 106 additions and 2 deletions.
diff --git a/src/cursor.rs b/src/cursor.rs
@@ -9,9 +9,11 @@
 //! module. The rest of it is available to make sure consumers of the API can understand precisely
 //! what types come out of functions that return `CursorIter`.
 
-use futures::Stream;
+use hyper::{Body, Request};
+use futures::{FutureExt, Stream};
 use serde::{de::DeserializeOwned, Deserialize};
 use std::future::Future;
+use std::marker::PhantomData;
 use std::pin::Pin;
 use std::task::{Context, Poll};
 
@@ -369,3 +371,84 @@ where
         self.poll_next(cx)
     }
 }
+
+/// Trait to generalize over paginated views of results on the Account Activity API.
+///
+/// Cursors on the Account Activity API differ from other cursors on the REST API in that they
+/// cannot page backwards, and in that their page IDs are strings instead of integers.
+///
+/// This is mainly meant to be implemented on raw/internal types to allow `ActivityCursorIter` to
+/// function, when paired with a type that implements `ActivityItem`.
+pub trait ActivityCursor: DeserializeOwned {
+    /// Moves the ID for the next page, if present, out of the cursor.
+    fn next_cursor(&mut self) -> Option<String>;
+}
+
+/// Trait for items which can be returned by `ActivityCursorIter`.
+pub trait ActivityItem: Sized {
+    /// What is the cursor type that `ActivityCursorIter` can deserialize into?
+    type Cursor: ActivityCursor + Into<Vec<Self>>;
+}
+
+pub struct ActivityCursorIter<CursorItem> {
+    url: &'static str,
+    token: auth::Token,
+    pub next_cursor: Option<String>,
+    pub count: u32,
+    pub loaded: bool,
+    _marker: PhantomData<CursorItem>,
+}
+
+impl<CursorItem: ActivityItem> ActivityCursorIter<CursorItem> {
+    pub(crate) fn new(url: &'static str, token: &auth::Token) -> Self {
+        ActivityCursorIter {
+            url,
+            token: token.clone(),
+            next_cursor: None,
+            count: 20,
+            loaded: false,
+            _marker: PhantomData,
+        }
+    }
+
+    pub fn with_page_size(self, count: u32) -> Self {
+        ActivityCursorIter {
+            count,
+            next_cursor: None,
+            loaded: false,
+            ..self
+        }
+    }
+
+    /// Clears the saved cursor information on this `ActivityCursorIter`.
+    pub fn reset(&mut self) {
+        self.next_cursor = None;
+        self.loaded = false;
+    }
+
+    fn request(&self, cursor: Option<String>) -> Request<Body> {
+        let params = ParamList::new()
+            .add_param("count", self.count.to_string())
+            .add_opt_param("cursor", cursor);
+
+        get(self.url, &self.token, Some(&params))
+    }
+
+    /// Loads the next page of messages, setting the `next_cursor` to the one received from
+    /// Twitter.
+    pub fn next_page<'s>(&'s mut self)
+        -> impl Future<Output = Result<Response<Vec<CursorItem>>>> + 's
+    {
+        let next_cursor = self.next_cursor.take();
+        let req = self.request(next_cursor);
+        let loader = request_with_json_response(req);
+        loader.map(
+            move |resp: Result<Response<CursorItem::Cursor>>| {
+                let mut resp = resp?;
+                self.loaded = true;
+                self.next_cursor = resp.next_cursor();
+                Ok(Response::map(resp, |c| c.into()))
+            }
+        )
+    }
+}
diff --git a/src/direct/mod.rs b/src/direct/mod.rs
@@ -123,6 +123,10 @@ impl From<raw::EventCursor> for Vec<DirectMessage> {
     }
 }
 
+impl crate::cursor::ActivityItem for DirectMessage {
+    type Cursor = raw::EventCursor;
+}
+
 /// Container for URL, hashtag, and mention information associated with a direct message.
 ///
 /// As far as entities are concerned, a DM can contain nearly everything a tweet can. The only

diff --git a/src/direct/raw.rs b/src/direct/raw.rs
@@ -171,6 +171,12 @@ pub struct EventCursor {
     pub next_cursor: Option<String>,
 }
 
+impl crate::cursor::ActivityCursor for EventCursor {
+    fn next_cursor(&mut self) -> Option<String> {
+        self.next_cursor.take()
+    }
+}
+
 /// Wrapper enum to represent a `DMEvent` in the Account Activity API.
 ///
 /// As direct messages are part of the Account Activity API, they are presented as an event type in

diff --git a/src/direct/welcome_messages.rs b/src/direct/welcome_messages.rs
@@ -72,6 +72,10 @@ impl From<MessageCursor> for Vec<WelcomeMessage> {
     }
 }
 
+impl crate::cursor::ActivityItem for WelcomeMessage {
+    type Cursor = MessageCursor;
+}
+
 #[derive(Deserialize)]
 struct RawWelcomeMessage {
     #[serde(with = "serde_via_string")]
@@ -113,13 +117,20 @@ struct SingleMessage {
 }
 
 #[derive(Deserialize)]
-struct MessageCursor {
+#[doc(hidden)]
+pub struct MessageCursor {
     #[serde(default)]
     apps: HashMap<String, TweetSource>,
     welcome_messages: Vec<RawWelcomeMessage>,
     next_cursor: Option<String>,
 }
 
+impl crate::cursor::ActivityCursor for MessageCursor {
+    fn next_cursor(&mut self) -> Option<String> {
+        self.next_cursor.take()
+    }
+}
+
 /// Helper struct to navigate a collection of welcome messages.
 pub struct Timeline {
     link: &'static str,