Merge pull request #1198 from iced-rs/subscription-helpers

`websocket` example and helpers to create custom subscriptions

7 files changed, 460 insertions, 92 deletions

diff --git a/examples/clock/src/main.rs b/examples/clock/src/main.rs
index de9e879a..325ccc1a 100644
--- a/examples/clock/src/main.rs
+++ b/examples/clock/src/main.rs
@@ -66,16 +66,12 @@ impl Application for Clock {
     }
 
     fn view(&mut self) -> Element<Message> {
-        let canvas = Canvas::new(self)
-            .width(Length::Units(400))
-            .height(Length::Units(400));
+        let canvas = Canvas::new(self).width(Length::Fill).height(Length::Fill);
 
         Container::new(canvas)
             .width(Length::Fill)
             .height(Length::Fill)
             .padding(20)
-            .center_x()
-            .center_y()
             .into()
     }
 }
diff --git a/examples/download_progress/src/download.rs b/examples/download_progress/src/download.rs
index 08805f13..7db1206b 100644
--- a/examples/download_progress/src/download.rs
+++ b/examples/download_progress/src/download.rs
@@ -1,111 +1,79 @@
-use iced_futures::futures;
-use std::hash::{Hash, Hasher};
+use iced_native::subscription;
+
+use std::hash::Hash;
 
 // Just a little utility function
-pub fn file<I: 'static + Hash + Copy + Send, T: ToString>(
+pub fn file<I: 'static + Hash + Copy + Send + Sync, T: ToString>(
     id: I,
     url: T,
 ) -> iced::Subscription<(I, Progress)> {
-    iced::Subscription::from_recipe(Download {
-        id,
-        url: url.to_string(),
+    subscription::unfold(id, State::Ready(url.to_string()), move |state| {
+        download(id, state)
     })
 }
 
+#[derive(Debug, Hash, Clone)]
 pub struct Download<I> {
     id: I,
     url: String,
 }
 
-// Make sure iced can use our download stream
-impl<H, I, T> iced_native::subscription::Recipe<H, I> for Download<T>
-where
-    T: 'static + Hash + Copy + Send,
-    H: Hasher,
-{
-    type Output = (T, Progress);
-
-    fn hash(&self, state: &mut H) {
-        struct Marker;
-        std::any::TypeId::of::<Marker>().hash(state);
-
-        self.id.hash(state);
-    }
+async fn download<I: Copy>(
+    id: I,
+    state: State,
+) -> (Option<(I, Progress)>, State) {
+    match state {
+        State::Ready(url) => {
+            let response = reqwest::get(&url).await;
 
-    fn stream(
-        self: Box<Self>,
-        _input: futures::stream::BoxStream<'static, I>,
-    ) -> futures::stream::BoxStream<'static, Self::Output> {
-        let id = self.id;
+            match response {
+                Ok(response) => {
+                    if let Some(total) = response.content_length() {
+                        (
+                            Some((id, Progress::Started)),
+                            State::Downloading {
+                                response,
+                                total,
+                                downloaded: 0,
+                            },
+                        )
+                    } else {
+                        (Some((id, Progress::Errored)), State::Finished)
+                    }
+                }
+                Err(_) => (Some((id, Progress::Errored)), State::Finished),
+            }
+        }
+        State::Downloading {
+            mut response,
+            total,
+            downloaded,
+        } => match response.chunk().await {
+            Ok(Some(chunk)) => {
+                let downloaded = downloaded + chunk.len() as u64;
 
-        Box::pin(futures::stream::unfold(
-            State::Ready(self.url),
-            move |state| async move {
-                match state {
-                    State::Ready(url) => {
-                        let response = reqwest::get(&url).await;
+                let percentage = (downloaded as f32 / total as f32) * 100.0;
 
-                        match response {
-                            Ok(response) => {
-                                if let Some(total) = response.content_length() {
-                                    Some((
-                                        (id, Progress::Started),
-                                        State::Downloading {
-                                            response,
-                                            total,
-                                            downloaded: 0,
-                                        },
-                                    ))
-                                } else {
-                                    Some((
-                                        (id, Progress::Errored),
-                                        State::Finished,
-                                    ))
-                                }
-                            }
-                            Err(_) => {
-                                Some(((id, Progress::Errored), State::Finished))
-                            }
-                        }
-                    }
+                (
+                    Some((id, Progress::Advanced(percentage))),
                     State::Downloading {
-                        mut response,
+                        response,
                         total,
                         downloaded,
-                    } => match response.chunk().await {
-                        Ok(Some(chunk)) => {
-                            let downloaded = downloaded + chunk.len() as u64;
-
-                            let percentage =
-                                (downloaded as f32 / total as f32) * 100.0;
-
-                            Some((
-                                (id, Progress::Advanced(percentage)),
-                                State::Downloading {
-                                    response,
-                                    total,
-                                    downloaded,
-                                },
-                            ))
-                        }
-                        Ok(None) => {
-                            Some(((id, Progress::Finished), State::Finished))
-                        }
-                        Err(_) => {
-                            Some(((id, Progress::Errored), State::Finished))
-                        }
                     },
-                    State::Finished => {
-                        // We do not let the stream die, as it would start a
-                        // new download repeatedly if the user is not careful
-                        // in case of errors.
-                        let _: () = iced::futures::future::pending().await;
+                )
+            }
+            Ok(None) => (Some((id, Progress::Finished)), State::Finished),
+            Err(_) => (Some((id, Progress::Errored)), State::Finished),
+        },
+        State::Finished => {
+            // We do not let the stream die, as it would start a
+            // new download repeatedly if the user is not careful
+            // in case of errors.
+            let _: () = iced::futures::future::pending().await;
 
-                        None
-                    }
-                }
-            },
-        ))
+            unreachable!()
+        }
     }
 }
 
diff --git a/examples/websocket/Cargo.toml b/examples/websocket/Cargo.toml
new file mode 100644
index 00000000..6b4d9d10
--- /dev/null
+++ b/examples/websocket/Cargo.toml
@@ -0,0 +1,22 @@
+[package]
+name = "websocket"
+version = "0.1.0"
+authors = ["Héctor Ramón Jiménez <hector0193@gmail.com>"]
+edition = "2018"
+publish = false
+
+[dependencies]
+iced = { path = "../..", features = ["tokio", "debug"] }
+iced_native = { path = "../../native" }
+iced_futures = { path = "../../futures" }
+
+[dependencies.async-tungstenite]
+version = "0.16"
+features = ["tokio-rustls-webpki-roots"]
+
+[dependencies.tokio]
+version = "1"
+features = ["time"]
+
+[dependencies.warp]
+version = "0.3"
diff --git a/examples/websocket/README.md b/examples/websocket/README.md
new file mode 100644
index 00000000..16e983da
--- /dev/null
+++ b/examples/websocket/README.md
@@ -0,0 +1,17 @@
+## Websocket
+
+A simple example that keeps a WebSocket connection open to an echo server.
+
+The example consists of 3 modules:
+- [`main`] contains the `Application` logic.
+- [`echo`] implements a WebSocket client for the [`echo::server`] with `async-tungstenite`.
+- [`echo::server`] implements a simple WebSocket echo server with `warp`.
+
+You can run it with `cargo run`:
+```
+cargo run --package websocket
+```
+
+[`main`]: src/main.rs
+[`echo`]: src/echo.rs
+[`echo::server`]: src/echo/server.rs
diff --git a/examples/websocket/src/echo.rs b/examples/websocket/src/echo.rs
new file mode 100644
index 00000000..13596ddd
--- /dev/null
+++ b/examples/websocket/src/echo.rs
@@ -0,0 +1,146 @@
+pub mod server;
+
+use iced_futures::futures;
+use iced_native::subscription::{self, Subscription};
+
+use futures::channel::mpsc;
+use futures::sink::SinkExt;
+use futures::stream::StreamExt;
+
+use async_tungstenite::tungstenite;
+
+pub fn connect() -> Subscription<Event> {
+    struct Connect;
+
+    subscription::unfold(
+        std::any::TypeId::of::<Connect>(),
+        State::Disconnected,
+        |state| async move {
+            match state {
+                State::Disconnected => {
+                    const ECHO_SERVER: &str = "ws://localhost:3030";
+
+                    match async_tungstenite::tokio::connect_async(ECHO_SERVER)
+                        .await
+                    {
+                        Ok((websocket, _)) => {
+                            let (sender, receiver) = mpsc::channel(100);
+
+                            (
+                                Some(Event::Connected(Connection(sender))),
+                                State::Connected(websocket, receiver),
+                            )
+                        }
+                        Err(_) => {
+                            let _ = tokio::time::sleep(
+                                tokio::time::Duration::from_secs(1),
+                            )
+                            .await;
+
+                            (Some(Event::Disconnected), State::Disconnected)
+                        }
+                    }
+                }
+                State::Connected(mut websocket, mut input) => {
+                    let mut fused_websocket = websocket.by_ref().fuse();
+
+                    futures::select! {
+                        received = fused_websocket.select_next_some() => {
+                            match received {
+                                Ok(tungstenite::Message::Text(message)) => {
+                                    (
+                                        Some(Event::MessageReceived(Message::User(message))),
+                                        State::Connected(websocket, input)
+                                    )
+                                }
+                                Ok(_) => {
+                                    (None, State::Connected(websocket, input))
+                                }
+                                Err(_) => {
+                                    (Some(Event::Disconnected), State::Disconnected)
+                                }
+                            }
+                        }
+
+                        message = input.select_next_some() => {
+                            let result = websocket.send(tungstenite::Message::Text(String::from(message))).await;
+
+                            if result.is_ok() {
+                                (None, State::Connected(websocket, input))
+                            } else {
+                                (Some(Event::Disconnected), State::Disconnected)
+                            }
+                        }
+                    }
+                }
+            }
+        },
+    )
+}
+
+#[derive(Debug)]
+enum State {
+    Disconnected,
+    Connected(
+        async_tungstenite::WebSocketStream<
+            async_tungstenite::tokio::ConnectStream,
+        >,
+        mpsc::Receiver<Message>,
+    ),
+}
+
+#[derive(Debug, Clone)]
+pub enum Event {
+    Connected(Connection),
+    Disconnected,
+    MessageReceived(Message),
+}
+
+#[derive(Debug, Clone)]
+pub struct Connection(mpsc::Sender<Message>);
+
+impl Connection {
+    pub fn send(&mut self, message: Message) {
+        let _ = self
+            .0
+            .try_send(message)
+            .expect("Send message to echo server");
+    }
+}
+
+#[derive(Debug, Clone)]
+pub enum Message {
+    Connected,
+    Disconnected,
+    User(String),
+}
+
+impl Message {
+    pub fn new(message: &str) -> Option<Self> {
+        if message.is_empty() {
+            None
+        } else {
+            Some(Self::User(message.to_string()))
+        }
+    }
+
+    pub fn connected() -> Self {
+        Message::Connected
+    }
+
+    pub fn disconnected() -> Self {
+        Message::Disconnected
+    }
+}
+
+impl From<Message> for String {
+    fn from(message: Message) -> Self {
+        match message {
+            Message::Connected => String::from("Connected successfully!"),
+            Message::Disconnected => {
+                String::from("Connection lost... Retrying...")
+            }
+            Message::User(message) => message,
+        }
+    }
+}
diff --git a/examples/websocket/src/echo/server.rs b/examples/websocket/src/echo/server.rs
new file mode 100644
index 00000000..7702d417
--- /dev/null
+++ b/examples/websocket/src/echo/server.rs
@@ -0,0 +1,57 @@
+use iced_futures::futures;
+
+use futures::channel::mpsc;
+use futures::{SinkExt, StreamExt};
+use warp::ws::WebSocket;
+use warp::Filter;
+
+// Basic WebSocket echo server adapted from:
+// https://github.com/seanmonstar/warp/blob/3ff2eaf41eb5ac9321620e5a6434d5b5ec6f313f/examples/websockets_chat.rs
+//
+// Copyright (c) 2018-2020 Sean McArthur
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+pub async fn run() {
+    let routes = warp::path::end().and(warp::ws()).map(|ws: warp::ws::Ws| {
+        ws.on_upgrade(move |socket| user_connected(socket))
+    });
+
+    warp::serve(routes).run(([127, 0, 0, 1], 3030)).await;
+}
+
+async fn user_connected(ws: WebSocket) {
+    let (mut user_ws_tx, mut user_ws_rx) = ws.split();
+    let (mut tx, mut rx) = mpsc::unbounded();
+
+    tokio::task::spawn(async move {
+        while let Some(message) = rx.next().await {
+            let _ = user_ws_tx.send(message).await.unwrap_or_else(|e| {
+                eprintln!("websocket send error: {}", e);
+            });
+        }
+    });
+
+    while let Some(result) = user_ws_rx.next().await {
+        let msg = match result {
+            Ok(msg) => msg,
+            Err(_) => break,
+        };
+
+        let _ = tx.send(msg).await;
+    }
+}
diff --git a/examples/websocket/src/main.rs b/examples/websocket/src/main.rs
new file mode 100644
index 00000000..c03a9f3a
--- /dev/null
+++ b/examples/websocket/src/main.rs
@@ -0,0 +1,162 @@
+mod echo;
+
+use iced::alignment::{self, Alignment};
+use iced::button::{self, Button};
+use iced::executor;
+use iced::scrollable::{self, Scrollable};
+use iced::text_input::{self, TextInput};
+use iced::{
+    Application, Color, Column, Command, Container, Element, Length, Row,
+    Settings, Subscription, Text,
+};
+
+pub fn main() -> iced::Result {
+    WebSocket::run(Settings::default())
+}
+
+#[derive(Default)]
+struct WebSocket {
+    messages: Vec<echo::Message>,
+    message_log: scrollable::State,
+    new_message: String,
+    new_message_state: text_input::State,
+    new_message_button: button::State,
+    state: State,
+}
+
+#[derive(Debug, Clone)]
+enum Message {
+    NewMessageChanged(String),
+    Send(echo::Message),
+    Echo(echo::Event),
+    Server,
+}
+
+impl Application for WebSocket {
+    type Message = Message;
+    type Flags = ();
+    type Executor = executor::Default;
+
+    fn new(_flags: Self::Flags) -> (Self, Command<Message>) {
+        (
+            Self::default(),
+            Command::perform(echo::server::run(), |_| Message::Server),
+        )
+    }
+
+    fn title(&self) -> String {
+        String::from("WebSocket - Iced")
+    }
+
+    fn update(&mut self, message: Message) -> Command<Message> {
+        match message {
+            Message::NewMessageChanged(new_message) => {
+                self.new_message = new_message;
+            }
+            Message::Send(message) => match &mut self.state {
+                State::Connected(connection) => {
+                    self.new_message.clear();
+
+                    connection.send(message);
+                }
+                State::Disconnected => {}
+            },
+            Message::Echo(event) => match event {
+                echo::Event::Connected(connection) => {
+                    self.state = State::Connected(connection);
+
+                    self.messages.push(echo::Message::connected());
+                }
+                echo::Event::Disconnected => {
+                    self.state = State::Disconnected;
+
+                    self.messages.push(echo::Message::disconnected());
+                }
+                echo::Event::MessageReceived(message) => {
+                    self.messages.push(message);
+                    self.message_log.snap_to(1.0);
+                }
+            },
+            Message::Server => {}
+        }
+
+        Command::none()
+    }
+
+    fn subscription(&self) -> Subscription<Message> {
+        echo::connect().map(Message::Echo)
+    }
+
+    fn view(&mut self) -> Element<Message> {
+        let message_log = if self.messages.is_empty() {
+            Container::new(
+                Text::new("Your messages will appear here...")
+                    .color(Color::from_rgb8(0x88, 0x88, 0x88)),
+            )
+            .width(Length::Fill)
+            .height(Length::Fill)
+            .center_x()
+            .center_y()
+            .into()
+        } else {
+            self.messages
+                .iter()
+                .cloned()
+                .fold(
+                    Scrollable::new(&mut self.message_log),
+                    |scrollable, message| scrollable.push(Text::new(message)),
+                )
+                .width(Length::Fill)
+                .height(Length::Fill)
+                .spacing(10)
+                .into()
+        };
+
+        let new_message_input = {
+            let mut input = TextInput::new(
+                &mut self.new_message_state,
+                "Type a message...",
+                &self.new_message,
+                Message::NewMessageChanged,
+            )
+            .padding(10);
+
+            let mut button = Button::new(
+                &mut self.new_message_button,
+                Text::new("Send")
+                    .height(Length::Fill)
+                    .vertical_alignment(alignment::Vertical::Center),
+            )
+            .padding([0, 20]);
+
+            if matches!(self.state, State::Connected(_)) {
+                if let Some(message) = echo::Message::new(&self.new_message) {
+                    input = input.on_submit(Message::Send(message.clone()));
+                    button = button.on_press(Message::Send(message));
+                }
+            }
+
+            Row::with_children(vec![input.into(), button.into()])
+                .spacing(10)
+                .align_items(Alignment::Fill)
+        };
+
+        Column::with_children(vec![message_log, new_message_input.into()])
+            .width(Length::Fill)
+            .height(Length::Fill)
+            .padding(20)
+            .spacing(10)
+            .into()
+    }
+}
+
+enum State {
+    Disconnected,
+    Connected(echo::Connection),
+}
+
+impl Default for State {
+    fn default() -> Self {
+        Self::Disconnected
+    }
+}