noema 0.1.3

use crate::resolver::Container;
use async_trait::async_trait;
use futures::future::join_all;
use std::error::Error;
use std::sync::Arc;

/// Event trait for events
/// # Examples
/// ```ignore
/// struct MyEvent{
///     pub information: String,
/// }
/// impl Event for MyEvent {
///     fn name(&self) -> String {
///         "MyEvent".to_string()
///     }
///     fn dispatch_strategy(&self) -> DispatchStrategy {
///         DispatchStrategy::parallel_continue_on_error()
///     }
/// }
/// ```
pub trait Event {
    /// Name of the event
    fn name(&self) -> String {
        std::any::type_name::<Self>().to_string()
    }

    /// Describe the event
    fn describe(&self) -> String {
        format!("Event {}", self.name())
    }

    /// Strategy for Event dispatching
    fn dispatch_strategy(&self) -> DispatchStrategy {
        DispatchStrategy::sequential_continue_on_error()
    }
}

/// Handler of an Event type E, processing the event
#[async_trait]
pub trait EventHandler<E: Event + Send + Sync> {
    async fn handle(&self, event: Arc<E>) -> Result<(), Box<dyn Error + Send + Sync>>;
}

/// How to dispatch events
pub enum DispatcherMode {
    Sequential,
    Parallel,
}

/// What to do on error during dispatch
pub enum DispatchOnError {
    StopOnError,
    ContinueOnError,
}

/// Strategy for dispatching the event
pub struct DispatchStrategy {
    pub mode: DispatcherMode,
    pub on_error: DispatchOnError,
}
impl DispatchStrategy {
    pub fn new(mode: DispatcherMode, on_error: DispatchOnError) -> Self {
        Self { mode, on_error }
    }
    pub fn sequential_stop_on_error() -> Self {
        Self {
            mode: DispatcherMode::Sequential,
            on_error: DispatchOnError::StopOnError,
        }
    }
    pub fn sequential_continue_on_error() -> Self {
        Self {
            mode: DispatcherMode::Sequential,
            on_error: DispatchOnError::ContinueOnError,
        }
    }
    pub fn parallel_stop_on_error() -> Self {
        Self {
            mode: DispatcherMode::Parallel,
            on_error: DispatchOnError::StopOnError,
        }
    }
    pub fn parallel_continue_on_error() -> Self {
        Self {
            mode: DispatcherMode::Parallel,
            on_error: DispatchOnError::ContinueOnError,
        }
    }
}

/// Dispatcher for Event type E
#[async_trait]
pub trait Dispatcher<E: Event + Send + Sync + 'static> {
    /// Get all event handlers for the event type E
    fn get_event_handlers()
    -> Arc<Vec<Arc<dyn Fn() -> Arc<dyn EventHandler<E> + Send + Sync> + Send + Sync>>>;

    /// Dispatch event to all handlers according to how and on_error parameters
    async fn dispatch(event: E) -> Result<(), Vec<Box<dyn Error + Send + Sync>>> {
        let event = Arc::new(event);
        let handlers = Self::get_event_handlers()
            .iter()
            .map(|factory| factory())
            .collect::<Vec<_>>();
        let mut errors: Vec<Box<dyn Error + Send + Sync>> = vec![];
        let strategy = event.dispatch_strategy();
        let mode = strategy.mode;
        let on_error = strategy.on_error;
        match mode {
            DispatcherMode::Sequential => {
                for handler in handlers.iter() {
                    let res = handler.handle(event.clone()).await;
                    if res.is_err() {
                        if let DispatchOnError::StopOnError = on_error {
                            return Err(vec![res.err().unwrap()]);
                        } else {
                            errors.push(res.err().unwrap());
                        }
                    }
                }
            }
            DispatcherMode::Parallel => {
                let mut errors: Vec<Box<dyn Error + Send + Sync>> = vec![];
                let futures_vec = handlers
                    .iter()
                    .map(|handler| {
                        let event_clone = event.clone();
                        let handler_clone = handler.clone();
                        async move { handler_clone.handle(event_clone).await }
                    })
                    .collect::<Vec<_>>();

                let results = join_all(futures_vec).await;
                for res in results {
                    if let Err(e) = res {
                        if let DispatchOnError::StopOnError = on_error {
                            return Err(vec![e]);
                        } else {
                            errors.push(e);
                        }
                    }
                }
            }
        }
        if !errors.is_empty() {
            return Err(errors);
        }
        Ok(())
    }
}

/// Dispatch an event to all its handlers
/// # Examples
/// ```ignore
/// let event = MyEvent {
///     information: "Some info".to_string(),
/// };
/// dispatch(event).await.unwrap();
/// ```
pub async fn dispatch<E: Event + Send + Sync + 'static>(
    event: E,
) -> Result<(), Vec<Box<dyn std::error::Error + Send + Sync>>>
where
    Container: Dispatcher<E>,
{
    <Container as Dispatcher<E>>::dispatch(event).await
}

/// Macro to register event handlers for event types
/// WHERE
///     Event MUST implement Event
///     EventHandlers MUST implement EventHandler and Injectable
///
/// Supports multiple event-handler registrations:
/// - Event: [Handler1, Handler2, Handler3]
///
/// # Examples
/// ```ignore
/// events_handlers!(
///     MyEvent: [MyEventHandler, MyAnotherEventHandler],
///     MyEventB: [MyEventBHandler, MyAnotherEventBHandler]
/// );
/// ```
#[macro_export]
macro_rules! events_handlers {
    // Entry point - process all items
    ($($item:tt)*) => {
        $crate::__events_handlers_internal!($($item)*);
    };
}

#[doc(hidden)]
#[macro_export]
macro_rules! __events_handlers_internal {
    // Base case - empty
    () => {};

    // Event: [handlers], more items
    ($event:path: [$($handler:ty),* $(,)?], $($rest:tt)*) => {
        const _: () = {
            use $crate::dispatcher::{Dispatcher, EventHandler};
            use $crate::inject::Injectable;
            use std::sync::{Arc, LazyLock};

            static _EVENT_HANDLERS: LazyLock<Arc<Vec<Arc<dyn Fn() -> Arc<dyn EventHandler<$event> + Send + Sync> + Send + Sync>>>> =
                LazyLock::new(|| {
                    let mut handlers: Vec<Arc<dyn Fn() -> Arc<dyn EventHandler<$event> + Send + Sync> + Send + Sync>> = Vec::new();
                    $(
                        let factory: Arc<dyn Fn() -> Arc<dyn EventHandler<$event> + Send + Sync> + Send + Sync> =
                            Arc::new(|| {
                                let handler = <$handler as Injectable>::inject();
                                Arc::new(handler) as Arc<dyn EventHandler<$event> + Send + Sync>
                            });
                        handlers.push(factory);
                    )*
                    Arc::new(handlers)
                });

            use $crate::resolver::{Container};
            impl Dispatcher<$event> for Container {
                fn get_event_handlers(&self) -> Arc<Vec<Arc<dyn Fn() -> Arc<dyn EventHandler<$event> + Send + Sync> + Send + Sync>>> {
                    _EVENT_HANDLERS.clone()
                }
            }

        };
        $crate::__events_handlers_internal!($($rest)*);
    };

    // Event: [handlers], last item
    ($event:path: [$($handler:ty),* $(,)?]) => {
        const _: () = {
            use $crate::dispatcher::{Dispatcher, EventHandler};
            use $crate::inject::Injectable;
            use std::sync::{Arc, LazyLock};

            static _EVENT_HANDLERS: LazyLock<Arc<Vec<Arc<dyn Fn() -> Arc<dyn EventHandler<$event> + Send + Sync> + Send + Sync>>>> =
                LazyLock::new(|| {
                    let mut handlers: Vec<Arc<dyn Fn() -> Arc<dyn EventHandler<$event> + Send + Sync> + Send + Sync>> = Vec::new();
                    $(
                        let factory: Arc<dyn Fn() -> Arc<dyn EventHandler<$event> + Send + Sync> + Send + Sync> =
                            Arc::new(|| {
                                let handler = <$handler as Injectable>::inject();
                                Arc::new(handler) as Arc<dyn EventHandler<$event> + Send + Sync>
                            });
                        handlers.push(factory);
                    )*
                    Arc::new(handlers)
                });

            use $crate::resolver::{Container};
            impl Dispatcher<$event> for Container {
                fn get_event_handlers() -> Arc<Vec<Arc<dyn Fn() -> Arc<dyn EventHandler<$event> + Send + Sync> + Send + Sync>>> {
                    _EVENT_HANDLERS.clone()
                }
            }
        };
    };
}

#[cfg(test)]
mod test {
    #[test]
    fn dispatcher_test() {
        use crate::dispatcher::{Event, EventHandler, dispatch};
        struct TestEvent {
            pub info: String,
        }
        impl Event for TestEvent {
            fn name(&self) -> String {
                "TestEvent".to_string()
            }
        }
        struct TestEventHandler;
        #[async_trait::async_trait]
        impl EventHandler<TestEvent> for TestEventHandler {
            async fn handle(
                &self,
                event: std::sync::Arc<TestEvent>,
            ) -> Result<(), Box<dyn std::error::Error + Send + Sync>> {
                println!("Handling event: {}", event.info);
                Ok(())
            }
        }
        impl crate::inject::Injectable for TestEventHandler {
            fn inject() -> Self {
                TestEventHandler {}
            }
        }
        events_handlers!(
            TestEvent: [TestEventHandler]
        );
        let event = TestEvent {
            info: "This is a test event".to_string(),
        };
        let result = futures::executor::block_on(dispatch(event));
        assert!(result.is_ok());
    }
}