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/// A set of asynchronous actions to be performed by some runtime.
#[derive(Debug)]
pub struct Command<T>(Internal<T>);
#[derive(Debug)]
enum Internal<T> {
None,
Single(T),
Batch(Vec<T>),
}
impl<T> Command<T> {
/// Creates an empty [`Command`].
///
/// In other words, a [`Command`] that does nothing.
pub const fn none() -> Self {
Self(Internal::None)
}
/// Creates a [`Command`] that performs a single [`Action`].
pub const fn single(action: T) -> Self {
Self(Internal::Single(action))
}
/// 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 {
let mut batch = Vec::new();
for Command(command) in commands {
match command {
Internal::None => {}
Internal::Single(command) => batch.push(command),
Internal::Batch(commands) => batch.extend(commands),
}
}
Self(Internal::Batch(batch))
}
/// Applies a transformation to the result of a [`Command`].
pub fn map<A>(self, f: impl Fn(T) -> A) -> Command<A>
where
T: 'static,
{
let Command(command) = self;
match command {
Internal::None => Command::none(),
Internal::Single(action) => Command::single(f(action)),
Internal::Batch(batch) => {
Command(Internal::Batch(batch.into_iter().map(f).collect()))
}
}
}
/// Returns all of the actions of the [`Command`].
pub fn actions(self) -> Vec<T> {
let Command(command) = self;
match command {
Internal::None => Vec::new(),
Internal::Single(action) => vec![action],
Internal::Batch(batch) => batch,
}
}
}
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