Make Command implementations platform-specific

This allows us to introduce a platform-specific `Action` to both `iced_native`
and `iced_web` and remove the `Clipboard` from `Application::update` to maintain
purity.

Additionally, this should let us implement further actions to let users query
and modify the shell environment (e.g. window, clipboard, and more!)

futures/src/command.rs

@@ -1,138 +0,0 @@
-use crate::BoxFuture;
-use futures::future::{Future, FutureExt};
-
-/// A collection of async operations.
-///
-/// You should be able to turn a future easily into a [`Command`], either by
-/// using the `From` trait or [`Command::perform`].
-pub struct Command<T> {
-    futures: Vec<BoxFuture<T>>,
-}
-
-impl<T> Command<T> {
-    /// Creates an empty [`Command`].
-    ///
-    /// In other words, a [`Command`] that does nothing.
-    pub fn none() -> Self {
-        Self {
-            futures: Vec::new(),
-        }
-    }
-
-    /// Creates a [`Command`] that performs the action of the given future.
-    #[cfg(not(target_arch = "wasm32"))]
-    pub fn perform<A>(
-        future: impl Future<Output = T> + 'static + Send,
-        f: impl Fn(T) -> A + 'static + Send,
-    ) -> Command<A> {
-        Command {
-            futures: vec![Box::pin(future.map(f))],
-        }
-    }
-
-    /// Creates a [`Command`] that performs the action of the given future.
-    #[cfg(target_arch = "wasm32")]
-    pub fn perform<A>(
-        future: impl Future<Output = T> + 'static,
-        f: impl Fn(T) -> A + 'static + Send,
-    ) -> Command<A> {
-        Command {
-            futures: vec![Box::pin(future.map(f))],
-        }
-    }
-
-    /// Applies a transformation to the result of a [`Command`].
-    #[cfg(not(target_arch = "wasm32"))]
-    pub fn map<A>(
-        mut self,
-        f: impl Fn(T) -> A + 'static + Send + Sync,
-    ) -> Command<A>
-    where
-        T: 'static,
-    {
-        let f = std::sync::Arc::new(f);
-
-        Command {
-            futures: self
-                .futures
-                .drain(..)
-                .map(|future| {
-                    let f = f.clone();
-
-                    Box::pin(future.map(move |result| f(result)))
-                        as BoxFuture<A>
-                })
-                .collect(),
-        }
-    }
-
-    /// Applies a transformation to the result of a [`Command`].
-    #[cfg(target_arch = "wasm32")]
-    pub fn map<A>(mut self, f: impl Fn(T) -> A + 'static) -> Command<A>
-    where
-        T: 'static,
-    {
-        let f = std::rc::Rc::new(f);
-
-        Command {
-            futures: self
-                .futures
-                .drain(..)
-                .map(|future| {
-                    let f = f.clone();
-
-                    Box::pin(future.map(move |result| f(result)))
-                        as BoxFuture<A>
-                })
-                .collect(),
-        }
-    }
-
-    /// Creates a [`Command`] that performs the actions of all the given
-    /// commands.
-    ///
-    /// Once this command is run, all the commands will be executed at once.
-    pub fn batch(commands: impl IntoIterator<Item = Command<T>>) -> Self {
-        Self {
-            futures: commands
-                .into_iter()
-                .flat_map(|command| command.futures)
-                .collect(),
-        }
-    }
-
-    /// Converts a [`Command`] into its underlying list of futures.
-    pub fn futures(self) -> Vec<BoxFuture<T>> {
-        self.futures
-    }
-}
-
-#[cfg(not(target_arch = "wasm32"))]
-impl<T, A> From<A> for Command<T>
-where
-    A: Future<Output = T> + 'static + Send,
-{
-    fn from(future: A) -> Self {
-        Self {
-            futures: vec![future.boxed()],
-        }
-    }
-}
-
-#[cfg(target_arch = "wasm32")]
-impl<T, A> From<A> for Command<T>
-where
-    A: Future<Output = T> + 'static,
-{
-    fn from(future: A) -> Self {
-        Self {
-            futures: vec![future.boxed_local()],
-        }
-    }
-}
-
-impl<T> std::fmt::Debug for Command<T> {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        f.debug_struct("Command").finish()
-    }
-}