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
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
//!
//! A context allows a child's future to access its received
//! messages, parent and supervisor.

use crate::child_ref::ChildRef;
use crate::children_ref::ChildrenRef;
use crate::envelope::{Envelope, RefAddr, SignedMessage};
use crate::message::{Answer, BastionMessage, Message, Msg};
use crate::supervisor::SupervisorRef;
use futures::pending;
use qutex::{Guard, Qutex};
use std::collections::VecDeque;
use std::fmt::{self, Display, Formatter};
use uuid::Uuid;

/// Identifier for a root supervisor and dead-letters children.
pub const NIL_ID: BastionId = BastionId(Uuid::nil());

#[derive(Hash, Eq, PartialEq, Debug, Clone)]
/// An identifier used by supervisors, children groups and
/// their elements to identify themselves, using a v4 UUID.
///
/// A `BastionId` is unique to its attached element and is
/// reset when it is restarted. A special `BastionId` exists
/// for the "system supervisor" (the supervisor created by
/// the system at startup) which is a nil UUID
/// (00000000-0000-0000-0000-000000000000).
///
/// # Example
///
/// ```rust
/// # use bastion::prelude::*;
/// #
/// # fn main() {
///     # Bastion::init();
///     #
/// Bastion::children(|children| {
///     children.with_exec(|ctx| {
///         async move {
///             let child_id: &BastionId = ctx.current().id();
///             // ...
///             # Ok(())
///         }
///     })
/// }).expect("Couldn't create the children group.");
///     #
///     # Bastion::start();
///     # Bastion::stop();
///     # Bastion::block_until_stopped();
/// # }
/// ```
pub struct BastionId(Uuid);

#[derive(Debug)]
/// A child's execution context, allowing its [`exec`] future
/// to receive messages and access a [`ChildRef`] referencing
/// it, a [`ChildrenRef`] referencing its children group and
/// a [`SupervisorRef`] referencing its supervisor.
///
/// # Example
///
/// ```rust
/// # use bastion::prelude::*;
/// #
/// # fn main() {
///     # Bastion::init();
///     #
/// Bastion::children(|children| {
///     children.with_exec(|ctx: BastionContext| {
///         async move {
///             // Get a `ChildRef` referencing the child executing
///             // this future...
///             let current: &ChildRef = ctx.current();
///             // Get a `ChildrenRef` referencing the children
///             // group of the child executing this future...
///             let parent: &ChildrenRef = ctx.parent();
///             // Try to get a `SupervisorRef` referencing the
///             // supervisor of the child executing this future...
///             let supervisor: Option<&SupervisorRef> = ctx.supervisor();
///             // Note that `supervisor` will be `None` because
///             // this child was created using `Bastion::children`,
///             // which made it supervised by the system supervisor
///             // (which users can't get a reference to).
///
///             // Try to receive a message...
///             let opt_msg: Option<SignedMessage> = ctx.try_recv().await;
///             // Wait for a message to be received...
///             let msg: SignedMessage = ctx.recv().await?;
///
///             Ok(())
///         }
///     })
/// }).expect("Couldn't create the children group.");
///     #
///     # Bastion::start();
///     # Bastion::stop();
///     # Bastion::block_until_stopped();
/// # }
/// ```
pub struct BastionContext {
    id: BastionId,
    child: ChildRef,
    children: ChildrenRef,
    supervisor: Option<SupervisorRef>,
    state: Qutex<ContextState>,
}

#[derive(Debug)]
pub(crate) struct ContextState {
    msgs: VecDeque<SignedMessage>,
}

impl BastionId {
    pub(crate) fn new() -> Self {
        let uuid = Uuid::new_v4();

        BastionId(uuid)
    }
}

impl BastionContext {
    pub(crate) fn new(
        id: BastionId,
        child: ChildRef,
        children: ChildrenRef,
        supervisor: Option<SupervisorRef>,
        state: Qutex<ContextState>,
    ) -> Self {
        debug!("BastionContext({}): Creating.", id);
        BastionContext {
            id,
            child,
            children,
            supervisor,
            state,
        }
    }

    /// Returns a [`ChildRef`] referencing the children group's
    /// element that is linked to this `BastionContext`.
    ///
    /// # Example
    ///
    /// ```rust
    /// # use bastion::prelude::*;
    /// #
    /// # fn main() {
    ///     # Bastion::init();
    ///     #
    /// Bastion::children(|children| {
    ///     children.with_exec(|ctx: BastionContext| {
    ///         async move {
    ///             let current: &ChildRef = ctx.current();
    ///             // Stop or kill the current element (note that this will
    ///             // only take effect after this future becomes "pending")...
    ///
    ///             Ok(())
    ///         }
    ///     })
    /// }).expect("Couldn't create the children group.");
    ///     #
    ///     # Bastion::start();
    ///     # Bastion::stop();
    ///     # Bastion::block_until_stopped();
    /// # }
    /// ```
    ///
    /// [`ChildRef`]: children/struct.ChildRef.html
    pub fn current(&self) -> &ChildRef {
        &self.child
    }

    /// Returns a [`ChildrenRef`] referencing the children group
    /// of the element that is linked to this `BastionContext`.
    ///
    /// # Example
    ///
    /// ```rust
    /// # use bastion::prelude::*;
    /// #
    /// # fn main() {
    ///     # Bastion::init();
    ///     #
    /// Bastion::children(|children| {
    ///     children.with_exec(|ctx: BastionContext| {
    ///         async move {
    ///             let parent: &ChildrenRef = ctx.parent();
    ///             // Get the other elements of the group, broadcast message,
    ///             // or stop or kill the children group...
    ///
    ///             Ok(())
    ///         }
    ///     })
    /// }).expect("Couldn't create the children group.");
    ///     #
    ///     # Bastion::start();
    ///     # Bastion::stop();
    ///     # Bastion::block_until_stopped();
    /// # }
    /// ```
    ///
    /// [`ChildrenRef`]: children/struct.ChildrenRef.html
    pub fn parent(&self) -> &ChildrenRef {
        &self.children
    }

    /// Returns a [`SupervisorRef`] referencing the supervisor
    /// that supervises the element that is linked to this
    /// `BastionContext` if it isn't the system supervisor
    /// (ie. if the children group wasn't created using
    /// [`Bastion::children`]).
    ///
    /// # Example
    ///
    /// ```rust
    /// # use bastion::prelude::*;
    /// #
    /// # fn main() {
    ///     # Bastion::init();
    ///     #
    /// // When calling the method from a children group supervised
    /// // by a supervisor created by the user...
    /// Bastion::supervisor(|sp| {
    ///     sp.children(|children| {
    ///         children.with_exec(|ctx: BastionContext| {
    ///             async move {
    ///                 // ...the method will return a SupervisorRef referencing the
    ///                 // user-created supervisor...
    ///                 let supervisor: Option<&SupervisorRef> = ctx.supervisor(); // Some
    ///                 assert!(supervisor.is_some());
    ///
    ///                 Ok(())
    ///             }
    ///         })
    ///     })
    /// }).expect("Couldn't create the supervisor.");
    ///
    /// // When calling the method from a children group supervised
    /// // by the system's supervisor...
    /// Bastion::children(|children| {
    ///     children.with_exec(|ctx: BastionContext| {
    ///         async move {
    ///             // ...the method won't return a SupervisorRef...
    ///             let supervisor: Option<&SupervisorRef> = ctx.supervisor(); // None
    ///             assert!(supervisor.is_none());
    ///
    ///             Ok(())
    ///         }
    ///     })
    /// }).expect("Couldn't create the children group.");
    ///     #
    ///     # Bastion::start();
    ///     # Bastion::stop();
    ///     # Bastion::block_until_stopped();
    /// # }
    /// ```
    ///
    /// [`SupervisorRef`]: supervisor/struct.SupervisorRef.html
    /// [`Bastion::children`]: struct.Bastion.html#method.children
    pub fn supervisor(&self) -> Option<&SupervisorRef> {
        self.supervisor.as_ref()
    }

    /// Tries to retrieve asynchronously a message received by
    /// the element this `BastionContext` is linked to.
    ///
    /// If you need to wait (always asynchronously) until at
    /// least one message can be retrieved, use [`recv`] instead.
    ///
    /// This method returns [`SignedMessage`] if a message was available, or
    /// `None` otherwise.
    ///
    /// # Example
    ///
    /// ```rust
    /// # use bastion::prelude::*;
    /// #
    /// # fn main() {
    ///     # Bastion::init();
    ///     #
    /// Bastion::children(|children| {
    ///     children.with_exec(|ctx: BastionContext| {
    ///         async move {
    ///             let opt_msg: Option<SignedMessage> = ctx.try_recv().await;
    ///             // If a message was received by the element, `opt_msg` will
    ///             // be `Some(Msg)`, otherwise it will be `None`.
    ///
    ///             Ok(())
    ///         }
    ///     })
    /// }).expect("Couldn't create the children group.");
    ///     #
    ///     # Bastion::start();
    ///     # Bastion::stop();
    ///     # Bastion::block_until_stopped();
    /// # }
    /// ```
    ///
    /// [`recv`]: #method.recv
    /// [`SignedMessage`]: ../prelude/struct.SignedMessage.html
    pub async fn try_recv(&self) -> Option<SignedMessage> {
        debug!("BastionContext({}): Trying to receive message.", self.id);
        // TODO: Err(Error)
        let mut state = self.state.clone().lock_async().await.ok()?;

        if let Some(msg) = state.msgs.pop_front() {
            trace!("BastionContext({}): Received message: {:?}", self.id, msg);
            Some(msg)
        } else {
            trace!("BastionContext({}): Received no message.", self.id);
            None
        }
    }

    /// Retrieves asynchronously a message received by the element
    /// this `BastionContext` is linked to and waits (always
    /// asynchronously) for one if none has been received yet.
    ///
    /// If you don't need to wait until at least one message
    /// can be retrieved, use [`try_recv`] instead.
    ///
    /// This method returns [`SignedMessage`] if it succeeded, or `Err(())`
    /// otherwise.
    ///
    /// # Example
    ///
    /// ```rust
    /// # use bastion::prelude::*;
    /// #
    /// # fn main() {
    ///     # Bastion::init();
    ///     #
    /// Bastion::children(|children| {
    ///     children.with_exec(|ctx: BastionContext| {
    ///         async move {
    ///             // This will block until a message has been received...
    ///             let msg: SignedMessage = ctx.recv().await?;
    ///
    ///             Ok(())
    ///         }
    ///     })
    /// }).expect("Couldn't create the children group.");
    ///     #
    ///     # Bastion::start();
    ///     # Bastion::stop();
    ///     # Bastion::block_until_stopped();
    /// # }
    /// ```
    ///
    /// [`try_recv`]: #method.try_recv
    /// [`SignedMessage`]: ../prelude/struct.SignedMessage.html
    pub async fn recv(&self) -> Result<SignedMessage, ()> {
        debug!("BastionContext({}): Waiting to receive message.", self.id);
        loop {
            // TODO: Err(Error)
            let mut state = self.state.clone().lock_async().await.unwrap();

            if let Some(msg) = state.msgs.pop_front() {
                trace!("BastionContext({}): Received message: {:?}", self.id, msg);
                return Ok(msg);
            }

            Guard::unlock(state);

            pending!();
        }
    }

    /// Returns [`RefAddr`] of the current `BastionContext`
    ///
    /// # Example
    ///
    /// ```rust
    /// # use bastion::prelude::*;
    /// #
    /// # fn main() {
    ///     # Bastion::init();
    ///     #
    ///
    /// Bastion::children(|children| {
    ///     children.with_exec(|ctx: BastionContext| {
    ///         async move {
    ///             ctx.tell(&ctx.signature(), "Hello to myself");
    ///
    ///             # Bastion::stop();
    ///             Ok(())
    ///         }
    ///     })
    /// }).expect("Couldn't create the children group.");
    ///     #
    ///     # Bastion::start();
    ///     # Bastion::block_until_stopped();
    /// # }
    /// ```
    ///
    /// [`RefAddr`]: /prelude/struct.Answer.html
    pub fn signature(&self) -> RefAddr {
        RefAddr::new(
            self.current().path().clone(),
            self.current().sender().clone(),
        )
    }

    /// Sends a message to the specified [`RefAddr`]
    ///
    /// # Arguments
    ///
    /// * `to` – the [`RefAddr`] to send the message to
    /// * `msg` – The actual message to send
    ///
    /// # Example
    ///
    /// ```rust
    /// # use bastion::prelude::*;
    /// #
    /// # fn main() {
    ///     # Bastion::init();
    ///     #
    /// Bastion::children(|children| {
    ///     children.with_exec(|ctx: BastionContext| {
    ///         async move {
    ///             // Wait for a message to be received...
    ///             let smsg: SignedMessage = ctx.recv().await?;
    ///             // Obtain address of this message sender...
    ///             let sender_addr = smsg.signature();
    ///             // And send something back
    ///             ctx.tell(&sender_addr, "Ack").expect("Unable to acknowledge");
    ///             Ok(())
    ///         }
    ///     })
    /// }).expect("Couldn't create the children group.");
    ///     #
    ///     # Bastion::start();
    ///     # Bastion::stop();
    ///     # Bastion::block_until_stopped();
    /// # }
    /// ```
    ///
    /// [`RefAddr`]: ../prelude/struct.RefAddr.html
    pub fn tell<M: Message>(&self, to: &RefAddr, msg: M) -> Result<(), M> {
        debug!(
            "{:?}: Telling message: {:?} to: {:?}",
            self.current().path(),
            msg,
            to.path()
        );
        let msg = BastionMessage::tell(msg);
        let env = Envelope::new_with_sign(msg, self.signature());
        // FIXME: panics?
        to.sender()
            .unbounded_send(env)
            .map_err(|err| err.into_inner().into_msg().unwrap())
    }

    /// Sends a message from behalf of current context to the addr,
    /// allowing to addr owner answer.
    ///
    /// This method returns [`Answer`] if it succeeded, or `Err(msg)`
    /// otherwise.
    ///
    /// # Argument
    ///
    /// * `msg` - The message to send.
    ///
    /// # Example
    ///
    /// ```
    /// # use bastion::prelude::*;
    /// #
    /// # fn main() {
    ///     # Bastion::init();
    /// // The message that will be "asked"...
    /// const ASK_MSG: &'static str = "A message containing data (ask).";
    /// // The message the will be "answered"...
    /// const ANSWER_MSG: &'static str = "A message containing data (answer).";
    ///
    ///     # let children_ref =
    /// // Create a new child...
    /// Bastion::children(|children| {
    ///     children.with_exec(|ctx: BastionContext| {
    ///         async move {
    ///             // ...which will receive the message asked...
    ///             msg! { ctx.recv().await?,
    ///                 msg: &'static str =!> {
    ///                     assert_eq!(msg, ASK_MSG);
    ///                     // Handle the message...
    ///
    ///                     // ...and eventually answer to it...
    ///                     answer!(ctx, ANSWER_MSG);
    ///                 };
    ///                 // This won't happen because this example
    ///                 // only "asks" a `&'static str`...
    ///                 _: _ => ();
    ///             }
    ///
    ///             Ok(())
    ///         }
    ///     })
    /// }).expect("Couldn't create the children group.");
    ///
    ///     # Bastion::children(|children| {
    ///         # children.with_exec(move |ctx: BastionContext| {
    ///             # let child_ref = children_ref.elems()[0].clone();
    ///             # async move {
    /// // Later, the message is "asked" to the child...
    /// let answer: Answer = ctx.ask(&child_ref.addr(), ASK_MSG).expect("Couldn't send the message.");
    ///
    /// // ...and the child's answer is received...
    /// msg! { answer.await.expect("Couldn't receive the answer."),
    ///     msg: &'static str => {
    ///         assert_eq!(msg, ANSWER_MSG);
    ///         // Handle the answer...
    ///     };
    ///     // This won't happen because this example
    ///     // only answers a `&'static str`...
    ///     _: _ => ();
    /// }
    ///                 #
    ///                 # Ok(())
    ///             # }
    ///         # })
    ///     # }).unwrap();
    ///     #
    ///     # Bastion::start();
    ///     # Bastion::stop();
    ///     # Bastion::block_until_stopped();
    /// # }
    /// ```
    ///
    /// [`Answer`]: /message/struct.Answer.html
    pub fn ask<M: Message>(&self, to: &RefAddr, msg: M) -> Result<Answer, M> {
        debug!(
            "{:?}: Asking message: {:?} to: {:?}",
            self.current().path(),
            msg,
            to
        );
        let (msg, answer) = BastionMessage::ask(msg);
        let env = Envelope::new_with_sign(msg, self.signature());
        // FIXME: panics?
        to.sender()
            .unbounded_send(env)
            .map_err(|err| err.into_inner().into_msg().unwrap())?;

        Ok(answer)
    }
}

impl ContextState {
    pub(crate) fn new() -> Self {
        let msgs = VecDeque::new();

        ContextState { msgs }
    }

    pub(crate) fn push_msg(&mut self, msg: Msg, sign: RefAddr) {
        self.msgs.push_back(SignedMessage::new(msg, sign))
    }
}

impl Display for BastionId {
    fn fmt(&self, fmt: &mut Formatter) -> fmt::Result {
        self.0.fmt(fmt)
    }
}