@startuml
'https://plantuml.com/sequence-diagram

actor "Player One" as Player1
actor "Player Two" as Player2
participant Matchmaker
participant Agones
participant "GameServer\nResource" as GameServer
box "Game Server Pod"
  participant "Game Server\nProcess" as Binary
  participant SDK
end box

activate GameServer

== No allocated <i>GameServers</i> ==

Player1 -> Matchmaker: Requests a game session
Matchmaker -> Agones: Create: <i>GameServerAllocation</i>
note left
  <i>GameServerAllocation</i> implemented to
  optionally select an already allocated <i>GameServer</i>
  if one exists. At this stage, one does not, so
  Agones will allocate a <i>Ready</i> <i>GameServer</i>.
end note
Agones -> GameServer: Finds a <i>Ready</i> <i>GameServer</i>,\nsets it to <i>Allocated</i> State
Matchmaker <-- Agones : <i>GameServerAllocation</i> is returned\nwith <i>GameServer</i> details\nincluding IP and port to connect to.
Player1 <-- Matchmaker : Returns <i>GameServer</i> connection information
Player1 -> Binary : Connects to game server process
Binary -> SDK : SDK.Alpha.PlayerConnect(id)
note right
  Process calls <i>PlayerConnect(...)</i>
  on player client connection.
end note
GameServer <-- SDK : Increments <i>Status.Players.Count</i>\nand add <i>id</i> to <i>Status.Players.Ids</i>

== Allocated <i>GameServers</i> with player(s) on them ==

Player2 -> Matchmaker: Requests a game session
Matchmaker -> Agones: Create: <i>GameServerAllocation</i>
note left
  The <i>GameServerAllocation</i> will this time
  find the Allocated <i>GameServer</i> that "Player One"
  is currently active on.
end note
Agones -> GameServer: Finds the Allocated <i>GameServer</i>\nwith player capacity.
note right
  This is the same <i>GameServer</i> that "Player One"
  is currently playing on.
end note
Matchmaker <-- Agones: returns <i>Allocated GameServer</i> record
Player2 <-- Matchmaker : Returns <i>GameServer</i> connection information
Player2 -> Binary : Connects to game server process
Binary -> SDK : SDK.Alpha.PlayerConnect(id)
GameServer <-- SDK : Increments <i>Status.Players.Count</i>\nand add <i>id</i> to <i>Status.Players.Ids</i>

@enduml