1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138

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()
    }
}