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

//! This module contains the `Envelope` that allow
//! to call methods of actors related to a sepcific
//! imcoming message.

use crate::{Actor, Context};
use anyhow::{anyhow, Error};
use async_trait::async_trait;
use futures::channel::oneshot;

pub(crate) struct Envelope<A: Actor> {
    handler: Box<dyn Handler<A>>,
}

impl<A: Actor> Envelope<A> {
    pub(crate) async fn handle(
        &mut self,
        actor: &mut A,
        ctx: &mut Context<A>,
    ) -> Result<(), Error> {
        self.handler.handle(actor, ctx).await
    }

    /// Creates an `Envelope` for `Interaction`.
    pub(crate) fn interaction<I>(input: I) -> (Self, oneshot::Receiver<Result<I::Output, Error>>)
    where
        A: InteractionHandler<I>,
        I: Interaction,
    {
        let (tx, rx) = oneshot::channel();
        let handler = InteractionHandlerImpl {
            input: Some(input),
            tx: Some(tx),
        };
        let this = Self {
            handler: Box::new(handler),
        };
        (this, rx)
    }

    /// Creates an `Envelope` for `Action`.
    pub(crate) fn action<I>(input: I) -> Self
    where
        A: ActionHandler<I>,
        I: Action,
    {
        let handler = ActionHandlerImpl { input: Some(input) };
        Self {
            handler: Box::new(handler),
        }
    }
}

/// Internal `Handler` type that used by `Actor`'s routine to execute
/// `ActionHandler` or `InteractionHandler`.
#[async_trait]
trait Handler<A: Actor>: Send {
    /// Main method that expects a mutable reference to `Actor` that
    /// will be used by implementations to handle messages.
    async fn handle(&mut self, actor: &mut A, _ctx: &mut Context<A>) -> Result<(), Error>;
}

/// `Interaction` type can be sent to an `Actor` that implements
/// `InteractionHandler` for that message type.
/// It has to return a response of `Output` type.
pub trait Interaction: Send + 'static {
    /// The type of a response.
    type Output: Send + 'static;
}

/// Type of `Handler` to process interaction in request-response style.
#[async_trait]
pub trait InteractionHandler<I: Interaction>: Actor {
    /// Asyncronous method that receives incoming message and return a response.
    async fn handle(&mut self, input: I, _ctx: &mut Context<Self>) -> Result<I::Output, Error>;
}

struct InteractionHandlerImpl<I, O> {
    input: Option<I>,
    tx: Option<oneshot::Sender<Result<O, Error>>>,
}

#[async_trait]
impl<A, I, O> Handler<A> for InteractionHandlerImpl<I, O>
where
    A: Actor + InteractionHandler<I>,
    I: Interaction<Output = O>,
    O: Send + 'static,
{
    async fn handle(&mut self, actor: &mut A, ctx: &mut Context<A>) -> Result<(), Error> {
        let input = self
            .input
            .take()
            .expect("interaction handler called twice (no msg)");
        let response = actor.handle(input, ctx).await;
        let tx = self
            .tx
            .take()
            .expect("interaction handler called twice (no tx)");
        tx.send(response)
            .map_err(|_| anyhow!("can't send a response of interaction"))?;
        Ok(())
    }
}

/// `Action` type can be sent to an `Actor` that implements
/// `ActionHandler` for that message type.
pub trait Action: Send + 'static {}

/// Type of `Handler` to process incoming messages in one-shot style.
#[async_trait]
pub trait ActionHandler<I: Action>: Actor {
    /// Asyncronous method that receives incoming message.
    async fn handle(&mut self, input: I, _ctx: &mut Context<Self>) -> Result<(), Error>;
}

struct ActionHandlerImpl<I> {
    input: Option<I>,
}

#[async_trait]
impl<A, I> Handler<A> for ActionHandlerImpl<I>
where
    A: Actor + ActionHandler<I>,
    I: Action,
{
    async fn handle(&mut self, actor: &mut A, ctx: &mut Context<A>) -> Result<(), Error> {
        let input = self.input.take().expect("action handler called twice");
        actor.handle(input, ctx).await
    }
}