From df3bd77384d882b0e53fd20b100b258c9d948b71 Mon Sep 17 00:00:00 2001
From: gmega <giuliano.mega@gmail.com>
Date: Tue, 29 Aug 2023 17:30:08 -0300
Subject: [PATCH] add basic peer lifecycle

---
 swarmsim/engine/peer.nim       | 43 ++++++++++++++++++++++++++++++++++
 swarmsim/engine/protocol.nim   |  8 +++++++
 swarmsim/engine/types.nim      |  6 +++++
 tests/codex/tblockexchange.nim |  7 +++++-
 tests/engine/tnetwork.nim      |  1 +
 tests/engine/tpeer.nim         | 36 +++++++++++++++++++++++++++-
 tests/helpers/inbox.nim        | 14 +++++++++++
 7 files changed, 113 insertions(+), 2 deletions(-)

diff --git a/swarmsim/engine/peer.nim b/swarmsim/engine/peer.nim
index 618263d..d47acb5 100644
--- a/swarmsim/engine/peer.nim
+++ b/swarmsim/engine/peer.nim
@@ -2,6 +2,7 @@ import std/options
 import std/random
 import std/hashes
 import sequtils
+import sugar
 
 import ./types
 import ./message
@@ -15,6 +16,33 @@ export protocol
 export eventdrivenengine
 export Peer
 
+type
+  PeerLifecycleChange* = ref object of SchedulableEvent
+    peer: Peer
+    network: Network
+    event: LifecycleEventType
+
+method atScheduledTime*(self: PeerLifecycleChange,
+    engine: EventDrivenEngine): void =
+
+  let peer = self.peer
+  let oldState = peer.up
+
+  # XXX We're somewhat lax with state machine transitions and will allow
+  # self-transitions...
+  let newState = case self.event:
+    of started, up:
+      true
+    of down:
+      false
+
+  peer.up = newState
+
+  # ... but self-transitions do not get reported downstream.
+  if oldState != newState:
+    self.peer.protocols.values.toSeq.apply(p =>
+        p.onLifecycleEventType(self.peer, self.event, self.network))
+
 proc getProtocol*(self: Peer, id: string): Option[Protocol] =
   if self.protocols.hasKey(id):
     return self.protocols[id].some
@@ -34,6 +62,21 @@ proc deliver*(self: Peer, message: Message, engine: EventDrivenEngine,
   self.deliverForType(message.messageType, message, engine, network)
   self.deliverForType(Message.allMessages, message, engine, network)
 
+proc scheduleLifecycleChange*(self: Peer, event: LifecycleEventType,
+    network: Network, time: uint64): void =
+  network.engine.schedule(PeerLifecycleChange(
+    peer: self,
+    network: network,
+    event: event,
+    time: time
+  ))
+
+proc startAt*(self: Peer, network: Network, time: uint64): void =
+  self.scheduleLifecycleChange(started, network, time)
+
+proc start*(self: Peer, network: Network): void =
+  self.startAt(network, network.engine.currentTime)
+
 proc initPeer*(self: Peer, protocols: seq[Protocol],
     peerId: Option[int] = none(int)): Peer =
 
diff --git a/swarmsim/engine/protocol.nim b/swarmsim/engine/protocol.nim
index 7d01dd9..8672c41 100644
--- a/swarmsim/engine/protocol.nim
+++ b/swarmsim/engine/protocol.nim
@@ -14,3 +14,11 @@ method deliver*(
   network: Network
 ): void {.base.} =
   raise newException(CatchableError, "Method without implementation override")
+
+method onLifecycleEventType*(
+  self: Protocol,
+  peer: Peer,
+  event: LifecycleEventType,
+  network: Network
+): void {.base.} =
+  discard
diff --git a/swarmsim/engine/types.nim b/swarmsim/engine/types.nim
index 9dbfcc4..630366e 100644
--- a/swarmsim/engine/types.nim
+++ b/swarmsim/engine/types.nim
@@ -37,8 +37,14 @@ type
     messageTypes*: seq[string]
 
 type
+  LifecycleEventType* = enum
+    started
+    up
+    down
+
   Peer* = ref object of RootObj
     peerId*: int
+    up*: bool = false
     protocols*: Table[string, Protocol]
     dispatch*: MultiTable[string, Protocol]
 
diff --git a/tests/codex/tblockexchange.nim b/tests/codex/tblockexchange.nim
index 04b3927..8b8fa0f 100644
--- a/tests/codex/tblockexchange.nim
+++ b/tests/codex/tblockexchange.nim
@@ -9,9 +9,11 @@ import ../helpers/testpeer
 
 suite "block exchange":
 
-  test "should respond to want-block message with a list of the blocks it has":
+  setup:
     let engine = EventDrivenEngine()
     let network = Network(engine: engine)
+
+  test "should respond to want-have message with a list of the blocks it has":
     let sender = TestPeer.new(network)
 
     let bex = BlockExchangeProtocol.new()
@@ -41,3 +43,6 @@ suite "block exchange":
     let response = Have(sender.inbox.messages[0])
 
     check(response.haves == toIntSet([0, 1, 4]))
+
+
+
diff --git a/tests/engine/tnetwork.nim b/tests/engine/tnetwork.nim
index 7289513..612b116 100644
--- a/tests/engine/tnetwork.nim
+++ b/tests/engine/tnetwork.nim
@@ -10,6 +10,7 @@ import ../helpers/inbox
 import ../helpers/types
 
 suite "network":
+
   test "should dispatch message to the correct peer":
 
     let engine = EventDrivenEngine()
diff --git a/tests/engine/tpeer.nim b/tests/engine/tpeer.nim
index 64d0b02..ee27713 100644
--- a/tests/engine/tpeer.nim
+++ b/tests/engine/tpeer.nim
@@ -9,6 +9,8 @@ import swarmsim/engine/message
 import ../helpers/inbox
 import ../helpers/types
 
+import pretty
+
 # We need this here as otherwise for some reason the nim compiler trips.
 proc `$`*(m: Message): string = repr m
 
@@ -79,7 +81,6 @@ suite "peer":
 
     check(i1.messages == @[m1, m2])
 
-
   test "should deliver all message types when listening to Message.allMessages":
     let i1 = Inbox(protocolId: "protocol1", messageTypes: @[Message.allMessages])
 
@@ -95,3 +96,36 @@ suite "peer":
 
     check(i1.messages == @[m1, m2, m3])
 
+  test "should be up after start":
+    let i1 = Inbox(protocolId: "lifecycleListener", messageTypes: @[])
+    let peer = Peer.new(protocols = @[Protocol i1])
+
+    peer.startAt(network, 5)
+
+    check(not peer.up)
+
+    engine.run()
+
+    check((repr i1.events) == (repr @[
+      LifecycleEvent(event: started, time: 5.uint64)]))
+
+    check(peer.up)
+
+  test "should not be up after going down":
+    let i1 = Inbox(protocolId: "lifecycleListener", messageTypes: @[])
+
+    let peer = Peer.new(protocols = @[Protocol i1])
+
+    peer.start(network)
+    peer.scheduleLifecycleChange(
+      event = down,
+      network = network,
+      time = 10
+    )
+
+    engine.run()
+
+    check((repr i1.events) == (repr @[
+      LifecycleEvent(event: started, time: 0),
+      LifecycleEvent(event: down, time: 10)
+    ]))
diff --git a/tests/helpers/inbox.nim b/tests/helpers/inbox.nim
index d25cccf..deefcbc 100644
--- a/tests/helpers/inbox.nim
+++ b/tests/helpers/inbox.nim
@@ -9,6 +9,11 @@ withTypeId:
     Inbox* = ref object of Protocol
       protocolId*: string
       messages*: seq[Message]
+      events*: seq[LifecycleEvent]
+
+    LifecycleEvent* = ref object of RootObj
+      event*: LifecycleEventType
+      time*: uint64
 
 method deliver*(
   self: Inbox,
@@ -20,7 +25,16 @@ method deliver*(
 
 method `protocolId`*(self: Inbox): string = self.protocolId
 
+method onLifecycleEventType*(
+  self: Inbox,
+  peer: Peer,
+  event: LifecycleEventType,
+  network: Network
+) =
+  self.events.add(LifecycleEvent(event: event, time: network.engine.currentTime))
+
 export Message
+export LifecycleEvent
 export peer
 export protocol
 export network