crux_core/command/builder.rs
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//! Command builders are an abstraction allowing chaining effects,
//! where outputs of one effect can serve as inputs to further effects,
//! without requiring an async context.
//!
//! Chaining streams with streams is currently not supported, as the semantics
//! of the composition are unclear. If you need to compose streams, use the async
//! API and tools from the `futures` crate.
use std::{future::Future, pin::pin};
use futures::{FutureExt, Stream, StreamExt};
use super::{context::CommandContext, Command};
/// A builder of one-off request command
// Task is a future which does the shell talking and returns an output
pub struct RequestBuilder<Effect, Event, Task> {
make_task: Box<dyn FnOnce(CommandContext<Effect, Event>) -> Task + Send>,
}
impl<Effect, Event, Task, T> RequestBuilder<Effect, Event, Task>
where
Effect: Send + 'static,
Event: Send + 'static,
Task: Future<Output = T> + Send + 'static,
{
pub fn new<F>(make_task: F) -> Self
where
F: FnOnce(CommandContext<Effect, Event>) -> Task + Send + 'static,
{
let make_task = Box::new(make_task);
RequestBuilder { make_task }
}
pub fn map<F, U>(self, map: F) -> RequestBuilder<Effect, Event, impl Future<Output = U>>
where
F: FnOnce(T) -> U + Send + 'static,
{
RequestBuilder::new(|ctx| self.into_future(ctx.clone()).map(map))
}
/// Chain another [`RequestBuilder`] to run after completion of this one,
/// passing the result to the provided closure `make_next_builder`.
///
/// The returned value of the closure must be a `RequestBuilder`, which
/// can represent some more work to be done before the composed future
/// is finished.
///
/// If you want to chain a subscription, use [`Self::then_stream`] instead.
///
/// The closure `make_next_builder` is only run *after* successful completion
/// of the `self` future.
///
/// Note that this function consumes the receiving `RequestBuilder` and returns a
/// new one that represents the composition.
///
/// # Example
///
/// ```
/// # use crux_core::{Command, Request};
/// # use crux_core::capability::Operation;
/// # use serde::{Deserialize, Serialize};
/// # #[derive(Debug, PartialEq, Clone, Serialize)]
/// # enum AnOperation {
/// # One,
/// # Two,
/// # More(u8),
/// # }
/// #
/// # #[derive(Debug, PartialEq, Deserialize)]
/// # enum AnOperationOutput {
/// # One,
/// # Two,
/// # Other(u8),
/// # }
/// #
/// # impl Operation for AnOperation {
/// # type Output = AnOperationOutput;
/// # }
/// #
/// # #[derive(Debug)]
/// # enum Effect {
/// # AnEffect(Request<AnOperation>),
/// # }
/// #
/// # impl From<Request<AnOperation>> for Effect {
/// # fn from(request: Request<AnOperation>) -> Self {
/// # Self::AnEffect(request)
/// # }
/// # }
/// #
/// # #[derive(Debug, PartialEq)]
/// # enum Event {
/// # Completed(AnOperationOutput),
/// # }
/// let mut cmd: Command<Effect, Event> = Command::request_from_shell(AnOperation::More(1))
/// .then_request(|first| {
/// let AnOperationOutput::Other(first) = first else {
/// panic!("Invalid output!")
/// };
///
/// let second = first + 1;
/// Command::request_from_shell(AnOperation::More(second))
/// })
/// .then_send(Event::Completed);
///
/// let Effect::AnEffect(mut request) = cmd.effects().next().unwrap();
/// assert_eq!(request.operation, AnOperation::More(1));
///
/// request
/// .resolve(AnOperationOutput::Other(1))
/// .expect("to resolve");
///
/// let Effect::AnEffect(mut request) = cmd.effects().next().unwrap();
/// assert_eq!(request.operation, AnOperation::More(2));
/// ```
pub fn then_request<F, U, NextTask>(
self,
make_next_builder: F,
) -> RequestBuilder<Effect, Event, impl Future<Output = U>>
where
F: FnOnce(T) -> RequestBuilder<Effect, Event, NextTask> + Send + 'static,
NextTask: Future<Output = U> + Send + 'static,
{
RequestBuilder::new(|ctx| {
self.into_future(ctx.clone())
.then(|out| make_next_builder(out).into_future(ctx))
})
}
/// Chain a [`StreamBuilder`] to run after completion of this [`RequestBuilder`],
/// passing the result to the provided closure `make_next_builder`.
///
/// The returned value of the closure must be a `StreamBuilder`, which
/// can represent some more work to be done before the composed future
/// is finished.
///
/// If you want to chain a request, use [`Self::then_request`] instead.
///
/// The closure `make_next_builder` is only run *after* successful completion
/// of the `self` future.
///
/// Note that this function consumes the receiving `RequestBuilder` and returns a
/// [`StreamBuilder`] that represents the composition.
///
/// # Example
///
/// ```
/// # use crux_core::{Command, Request};
/// # use crux_core::capability::Operation;
/// # use serde::{Deserialize, Serialize};
/// # #[derive(Debug, PartialEq, Clone, Serialize)]
/// # enum AnOperation {
/// # One,
/// # Two,
/// # More(u8),
/// # }
/// #
/// # #[derive(Debug, PartialEq, Deserialize)]
/// # enum AnOperationOutput {
/// # One,
/// # Two,
/// # Other(u8),
/// # }
/// #
/// # impl Operation for AnOperation {
/// # type Output = AnOperationOutput;
/// # }
/// #
/// # #[derive(Debug)]
/// # enum Effect {
/// # AnEffect(Request<AnOperation>),
/// # }
/// #
/// # impl From<Request<AnOperation>> for Effect {
/// # fn from(request: Request<AnOperation>) -> Self {
/// # Self::AnEffect(request)
/// # }
/// # }
/// #
/// # #[derive(Debug, PartialEq)]
/// # enum Event {
/// # Completed(AnOperationOutput),
/// # }
/// let mut cmd: Command<Effect, Event> = Command::request_from_shell(AnOperation::More(1))
/// .then_stream(|first| {
/// let AnOperationOutput::Other(first) = first else {
/// panic!("Invalid output!")
/// };
///
/// let second = first + 1;
/// Command::stream_from_shell(AnOperation::More(second))
/// })
/// .then_send(Event::Completed);
///
/// let Effect::AnEffect(mut request) = cmd.effects().next().unwrap();
/// assert_eq!(request.operation, AnOperation::More(1));
///
/// request
/// .resolve(AnOperationOutput::Other(1))
/// .expect("to resolve");
///
/// let Effect::AnEffect(mut request) = cmd.effects().next().unwrap();
/// assert_eq!(request.operation, AnOperation::More(2));
pub fn then_stream<F, U, NextTask>(
self,
make_next_builder: F,
) -> StreamBuilder<Effect, Event, impl Stream<Item = U>>
where
F: FnOnce(T) -> StreamBuilder<Effect, Event, NextTask> + Send + 'static,
NextTask: Stream<Item = U> + Send + 'static,
{
StreamBuilder::new(|ctx| {
self.into_future(ctx.clone())
.map(make_next_builder)
.into_stream()
.flat_map(move |builder| builder.into_stream(ctx.clone()))
})
}
/// Convert the request builder into a future to use in an async context
pub fn into_future(self, ctx: CommandContext<Effect, Event>) -> Task {
let make_task = self.make_task;
make_task(ctx)
}
/// Create the command in an evented context
pub fn then_send<E>(self, event: E) -> Command<Effect, Event>
where
E: FnOnce(T) -> Event + Send + 'static,
Task: Future<Output = T> + Send + 'static,
{
Command::new(|ctx| async move {
let out = self.into_future(ctx.clone()).await;
ctx.send_event(event(out));
})
}
}
/// A builder of stream command
pub struct StreamBuilder<Effect, Event, Task> {
make_stream: Box<dyn FnOnce(CommandContext<Effect, Event>) -> Task + Send>,
}
impl<Effect, Event, Task, T> StreamBuilder<Effect, Event, Task>
where
Effect: Send + 'static,
Event: Send + 'static,
Task: Stream<Item = T> + Send + 'static,
{
pub fn new<F>(make_task: F) -> Self
where
F: FnOnce(CommandContext<Effect, Event>) -> Task + Send + 'static,
{
let make_task = Box::new(make_task);
StreamBuilder {
make_stream: make_task,
}
}
pub fn map<F, U>(self, map: F) -> StreamBuilder<Effect, Event, impl Stream<Item = U>>
where
F: FnMut(T) -> U + Send + 'static,
{
StreamBuilder::new(|ctx| self.into_stream(ctx.clone()).map(map))
}
/// Chain a [`RequestBuilder`] to run after completion of this [`StreamBuilder`],
/// passing the result to the provided closure `make_next_builder`.
///
/// The returned value of the closure must be a [`StreamBuilder`], which
/// can represent some more work to be done before the composed future
/// is finished.
///
/// If you want to chain a subscription, use [`Self::then_stream`] instead.
///
/// The closure `make_next_builder` is only run *after* successful completion
/// of the `self` future.
///
/// Note that this function consumes the receiving `StreamBuilder` and returns a
/// new one that represents the composition.
///
/// # Example
///
/// ```
/// # use crux_core::{Command, Request};
/// # use crux_core::capability::Operation;
/// # use serde::{Deserialize, Serialize};
/// # #[derive(Debug, PartialEq, Clone, Serialize)]
/// # enum AnOperation {
/// # One,
/// # Two,
/// # More(u8),
/// # }
/// #
/// # #[derive(Debug, PartialEq, Deserialize)]
/// # enum AnOperationOutput {
/// # One,
/// # Two,
/// # Other(u8),
/// # }
/// #
/// # impl Operation for AnOperation {
/// # type Output = AnOperationOutput;
/// # }
/// #
/// # #[derive(Debug)]
/// # enum Effect {
/// # AnEffect(Request<AnOperation>),
/// # }
/// #
/// # impl From<Request<AnOperation>> for Effect {
/// # fn from(request: Request<AnOperation>) -> Self {
/// # Self::AnEffect(request)
/// # }
/// # }
/// #
/// # #[derive(Debug, PartialEq)]
/// # enum Event {
/// # Completed(AnOperationOutput),
/// # }
/// let mut cmd: Command<Effect, Event> = Command::stream_from_shell(AnOperation::More(1))
/// .then_request(|first| {
/// let AnOperationOutput::Other(first) = first else {
/// panic!("Invalid output!")
/// };
///
/// let second = first + 1;
/// Command::request_from_shell(AnOperation::More(second))
/// })
/// .then_send(Event::Completed);
///
/// let Effect::AnEffect(mut request) = cmd.effects().next().unwrap();
/// assert_eq!(request.operation, AnOperation::More(1));
///
/// request
/// .resolve(AnOperationOutput::Other(1))
/// .expect("to resolve");
///
/// let Effect::AnEffect(mut request) = cmd.effects().next().unwrap();
/// assert_eq!(request.operation, AnOperation::More(2));
/// ```
pub fn then_request<F, U, NextTask>(
self,
make_next_builder: F,
) -> StreamBuilder<Effect, Event, impl Stream<Item = U>>
where
F: Fn(T) -> RequestBuilder<Effect, Event, NextTask> + Send + 'static,
NextTask: Future<Output = U> + Send + 'static,
{
StreamBuilder::new(|ctx| {
self.into_stream(ctx.clone())
.then(move |item| make_next_builder(item).into_future(ctx.clone()))
})
}
/// Chain another [`StreamBuilder`] to run after completion of this one,
/// passing the result to the provided closure `make_next_builder`.
///
/// The returned value of the closure must be a `StreamBuilder`, which
/// can represent some more work to be done before the composed future
/// is finished.
///
/// If you want to chain a request, use [`Self::then_request`] instead.
///
/// The closure `make_next_builder` is only run *after* successful completion
/// of the `self` future.
///
/// Note that this function consumes the receiving `StreamBuilder` and returns a
/// new one that represents the composition.
///
/// # Example
///
/// ```
/// # use crux_core::{Command, Request};
/// # use crux_core::capability::Operation;
/// # use serde::{Deserialize, Serialize};
/// # #[derive(Debug, PartialEq, Clone, Serialize)]
/// # enum AnOperation {
/// # One,
/// # Two,
/// # More(u8),
/// # }
/// #
/// # #[derive(Debug, PartialEq, Deserialize)]
/// # enum AnOperationOutput {
/// # One,
/// # Two,
/// # Other(u8),
/// # }
/// #
/// # impl Operation for AnOperation {
/// # type Output = AnOperationOutput;
/// # }
/// #
/// # #[derive(Debug)]
/// # enum Effect {
/// # AnEffect(Request<AnOperation>),
/// # }
/// #
/// # impl From<Request<AnOperation>> for Effect {
/// # fn from(request: Request<AnOperation>) -> Self {
/// # Self::AnEffect(request)
/// # }
/// # }
/// #
/// # #[derive(Debug, PartialEq)]
/// # enum Event {
/// # Completed(AnOperationOutput),
/// # }
/// let mut cmd: Command<Effect, Event> = Command::stream_from_shell(AnOperation::More(1))
/// .then_stream(|first| {
/// let AnOperationOutput::Other(first) = first else {
/// panic!("Invalid output!")
/// };
///
/// let second = first + 1;
/// Command::stream_from_shell(AnOperation::More(second))
/// })
/// .then_send(Event::Completed);
///
/// let Effect::AnEffect(mut request) = cmd.effects().next().unwrap();
/// assert_eq!(request.operation, AnOperation::More(1));
///
/// request
/// .resolve(AnOperationOutput::Other(1))
/// .expect("to resolve");
///
/// let Effect::AnEffect(mut request) = cmd.effects().next().unwrap();
/// assert_eq!(request.operation, AnOperation::More(2));
pub fn then_stream<F, U, NextTask>(
self,
make_next_builder: F,
) -> StreamBuilder<Effect, Event, impl Stream<Item = U>>
where
F: Fn(T) -> StreamBuilder<Effect, Event, NextTask> + Send + 'static,
NextTask: Stream<Item = U> + Send + 'static,
{
StreamBuilder::new(move |ctx| {
self.into_stream(ctx.clone())
.map(move |item| {
let next_builder = make_next_builder(item);
Box::pin(next_builder.into_stream(ctx.clone()))
})
.flatten_unordered(None)
})
}
/// Create the command in an evented context
pub fn then_send<E>(self, event: E) -> Command<Effect, Event>
where
E: Fn(T) -> Event + Send + 'static,
{
Command::new(|ctx| async move {
let mut stream = pin!(self.into_stream(ctx.clone()));
while let Some(out) = stream.next().await {
ctx.send_event(event(out));
}
})
}
/// Convert the stream builder into a stream to use in an async context
pub fn into_stream(self, ctx: CommandContext<Effect, Event>) -> Task {
let make_stream = self.make_stream;
make_stream(ctx)
}
}