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use crate :: { Filter, Observe, ObserveLocal };
/// Indicate that a type is observable. You can call [`observe`](Observable::observe) to get a
/// stream of events.
///
/// Generally used with a [Pharos](crate::Pharos) object which manages the observers for you.
///
/// ```
/// use pharos::*;
/// use futures::stream::StreamExt;
///
/// // The event we want to broadcast
/// //
/// #[ derive( Debug, Clone ) ]
/// //
/// enum Steps
/// {
/// Step1 ,
/// Step2 ,
/// Done ,
///
/// // Data is possible, but it has to be clone and will be cloned for each observer
/// // except observers that filter this event out.
/// //
/// Error(u8) ,
/// }
///
///
/// impl Steps
/// {
/// // We can use this as a predicate to filter events.
/// //
/// fn is_err( &self ) -> bool
/// {
/// match self
/// {
/// Self::Error(_) => true ,
/// _ => false ,
/// }
/// }
/// }
///
///
/// // The object we want to be observable.
/// //
/// struct Foo { pharos: Pharos<Steps> };
///
/// impl Observable<Steps> for Foo
/// {
/// type Error = PharErr;
///
/// // Pharos implements observable, so we just forward the call.
/// //
/// fn observe( &mut self, options: ObserveConfig<Steps> ) -> Observe< '_, Steps, Self::Error>
/// {
/// self.pharos.observe( options )
/// }
/// }
///
///
/// // use in async context
/// //
/// async fn task()
/// {
/// let mut foo = Foo { pharos: Pharos::default() };
/// let mut errors = foo.observe( Filter::Pointer( Steps::is_err ).into() ).await.expect( "observe" );
///
/// // will only be notified on errors thanks to the filter.
/// //
/// let next_error = errors.next().await;
/// }
/// ```
//
pub trait Observable<Event>
where Event: Clone + 'static + Send ,
{
/// The error type that is returned if observing is not possible.
///
/// [Pharos](crate::Pharos) implements
/// [Sink](https://docs.rs/futures-preview/0.3.0-alpha.19/futures/sink/trait.Sink.html)
/// which has a close method, so observing will no longer be possible after close is called.
///
/// Other than that, you might want to have moments in your objects lifetime when you don't want to take
/// any more observers. Returning a result from [observe](Observable::observe) enables that.
///
/// You can of course map the error of pharos to your own error type.
//
type Error: std::error::Error;
/// Add an observer to the observable. Options allow chosing the channel type and
/// to filter events with a predicate.
//
fn observe( &mut self, options: ObserveConfig<Event> ) -> Observe<'_, Event, Self::Error >;
}
/// Like Observable, but the future returned is not `Send`, thus the observable type does not need to be `Send`.
//
pub trait ObservableLocal<Event>
where Event: Clone + 'static + Send ,
{
/// The error type that is returned if observing is not possible.
///
/// [Pharos](crate::Pharos) implements
/// [Sink](https://docs.rs/futures-preview/0.3.0-alpha.19/futures/sink/trait.Sink.html)
/// which has a close method, so observing will no longer be possible after close is called.
///
/// Other than that, you might want to have moments in your objects lifetime when you don't want to take
/// any more observers. Returning a result from [observe](Observable::observe) enables that.
///
/// You can of course map the error of pharos to your own error type.
//
type Error: std::error::Error;
/// Add an observer to the observable. Options allow chosing the channel type and
/// to filter events with a predicate.
//
fn observe_local( &mut self, options: ObserveConfig<Event> ) -> ObserveLocal<'_, Event, Self::Error >;
}
/// Choose the type of channel that will be used for your event stream. Used in [ObserveConfig].
//
#[ derive( Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord )]
//
pub enum Channel
{
/// A channel with a limited message queue (the usize parameter). Creates back pressure when the buffer is full.
/// This means that producer tasks may block if consumers can't process fast enough.
///
/// The minimum valid buffer size is 1.
//
Bounded(usize),
/// A channel with unbounded capacity. Note that this may lead to unbounded memory consumption if producers
/// outpace consumers.
//
Unbounded,
/// This enum might grow in the future, thanks to this that won't be a breaking change.
//
__NonExhaustive__
}
impl Default for Channel
{
fn default() -> Self
{
Channel::Unbounded
}
}
/// Configuration for your event stream.
///
/// Pass to [Observable::observe] when subscribing. This let's you choose the type of [channel](Channel) and let's
/// you set a [filter](Filter) to ignore certain events.
///
/// ```
/// use pharos::*;
///
/// // We choose event type usize for simplicity. You choose whatever type you want here,
/// // see the bounds on the Event type parameter throughout this library.
/// //
/// let mut pharos = Pharos::<usize>::default();
///
/// // Use defaults, unbounded channel and no filter.
/// //
/// pharos.observe( ObserveConfig::default() );
///
/// // Use bounded channel and defaults for other options.
/// //
/// pharos.observe( Channel::Bounded(5).into() );
///
/// // Use a filter and defaults for other options.
/// // Will only receive events if they are bigger than three.
/// //
/// pharos.observe( Filter::Pointer( |evt| *evt > 3 ).into() );
///
/// // Set both channel and filter. Note you can only set one filter per observable.
/// //
/// let opts = ObserveConfig::default()
///
/// .channel( Channel::Bounded( 5 ) )
/// .filter ( |evt| *evt > 3 )
/// ;
///
/// pharos.observe( opts );
/// ```
//
#[ derive( Debug ) ]
//
pub struct ObserveConfig<Event> where Event: Clone + 'static + Send
{
pub(crate) channel: Channel,
pub(crate) filter : Option<Filter<Event>>,
}
/// Create a default configuration:
/// - no filter
/// - an unbounded channel
//
impl<Event> Default for ObserveConfig<Event> where Event: Clone + 'static + Send
{
fn default() -> Self
{
Self
{
channel: Channel::default(),
filter : None ,
}
}
}
impl<Event> ObserveConfig<Event> where Event: Clone + 'static + Send
{
/// Choose which channel implementation to use for your event stream.
//
pub fn channel( mut self, channel: Channel ) -> Self
{
self.channel = channel;
self
}
/// Filter your event stream with a predicate that is a fn pointer.
/// You can only set one filter per observable.
//
pub fn filter( mut self, filter: fn(&Event) -> bool ) -> Self
{
debug_assert!( self.filter.is_none(), "You can only set one filter on ObserveConfig" );
self.filter = Some( Filter::Pointer(filter) );
self
}
/// Filter your event stream with a predicate that is a closure that captures environment.
/// It is preferred to use [filter](ObserveConfig::filter) if you can as this will box the closure.
/// You can only set one filter per observable.
//
pub fn filter_boxed( mut self, filter: impl FnMut(&Event) -> bool + Send + 'static ) -> Self
{
debug_assert!( self.filter.is_none(), "You can only set one filter on ObserveConfig" );
self.filter = Some( Filter::Closure( Box::new(filter) ) );
self
}
}
/// Create a [ObserveConfig] from a [Channel], getting default values for other options.
//
impl<Event> From<Channel> for ObserveConfig<Event> where Event: Clone + 'static + Send
{
fn from( channel: Channel ) -> Self
{
Self::default().channel( channel )
}
}
/// Create a [ObserveConfig] from a [Filter], getting default values for other options.
//
impl<Event> From<Filter<Event>> for ObserveConfig<Event> where Event: Clone + 'static + Send
{
fn from( filter: Filter<Event> ) -> Self
{
Self
{
filter: Some(filter),
..Self::default()
}
}
}