From fa22f6f6f6357f3b1f78637fc022e6a8fd9cc894 Mon Sep 17 00:00:00 2001
From: Justin van der Leij <justinvanderleij@gmail.com>
Date: Wed, 21 Feb 2018 13:38:27 +0100
Subject: [PATCH] Some more work on system-instance interaction

---
 fluid/eventManager.lua |  4 +++-
 fluid/instance.lua     | 31 ++++++++++++-------------------
 fluid/system.lua       | 13 ++++++++++---
 3 files changed, 25 insertions(+), 23 deletions(-)

diff --git a/fluid/eventManager.lua b/fluid/eventManager.lua
index 61d0066..0283a27 100644
--- a/fluid/eventManager.lua
+++ b/fluid/eventManager.lua
@@ -45,7 +45,9 @@ function EventManager:deregister(name, listener, callback)
             table.remove(listeners, index)
             listeners.count = listeners.count - 1
 
-            return
+            if callback then
+               break
+            end
          end
       end
    end
diff --git a/fluid/instance.lua b/fluid/instance.lua
index 8d8005c..720a3ec 100644
--- a/fluid/instance.lua
+++ b/fluid/instance.lua
@@ -9,10 +9,9 @@ Instance.__index = Instance
 function Instance.new()
    local instance = setmetatable({
       entities     = List(),
+      systems      = List(),
+      systemCount  = {},
       eventManager = EventManager(),
-
-      systems      = {},
-      namedSystems = {},
    }, Instance)
 
    return instance
@@ -25,8 +24,8 @@ function Instance:addEntity(e)
 end
 
 function Instance:checkEntity(e)
-   for _, system in ipairs(self.systems) do
-      system:__checkEntity(e)
+   for i = 1, self.systems.size do
+      self.systems:get(i):__check(e)
    end
 end
 
@@ -34,16 +33,14 @@ function Instance:removeEntity(e)
    e.instances:remove(self)
    self.entities:remove(e)
 
-   for _, system in ipairs(self.systems) do
-      system:__remove(e)
+   for i = 1, self.systems.size do
+      self.systems:get(i):__remove(e)
    end
 end
 
 function Instance:addSystem(system, eventName, callback)
-   if not self.namedSystems[system] then
-      self.systems[#self.systems + 1] = system
-      self.namedSystems[system]       = system
-   end
+   self.systemCount[system] = (self.systemCount[system] or 0) + 1
+   self.systems:add(system)
 
    self.eventManager:register(eventName, system, callback)
 
@@ -51,16 +48,12 @@ function Instance:addSystem(system, eventName, callback)
 end
 
 function Instance:removeSystem(system, callback)
-   for index, other in ipairs(self.systems) do
-      if system == other then
-         table.remove(self.systems, index)
-      end
+   self.systemCount[system] = self.systemCount[system] - 1
+   if self.systemCount[system] == 0 then
+      self.systemCount[system] = nil
+      self.eventManager:deregister(eventName, system, callback)
    end
 
-   self.eventManager:deregister(eventName, system, callback)
-
-   self.namedSystems[system] = nil
-
    return self
 end
 
diff --git a/fluid/system.lua b/fluid/system.lua
index 0775f88..e9e5b58 100644
--- a/fluid/system.lua
+++ b/fluid/system.lua
@@ -8,8 +8,9 @@ System.mt    = {
    __index = System,
    __call  = function(systemProto, ...)
       local system = setmetatable({
-         __all   = {},
-         __pools = {},
+         __all      = {},
+         __pools    = {},
+         __instance = nil,
       }, systemProto)
 
       for _, filter in pairs(systemProto.__filter) do
@@ -39,6 +40,12 @@ end
 function System:init(...)
 end
 
+function System:destroy()
+   if self.instance then
+      self.instance:removeSystem(self)
+   end
+end
+
 function System:__buildPool(pool)
    local name   = "pool"
    local filter = {}
@@ -54,7 +61,7 @@ function System:__buildPool(pool)
    return Pool(name, filter)
 end
 
-function System:__checkEntity(e)
+function System:__check(e)
    local systemHas = self:__has(e)
 
    for _, pool in ipairs(self.__pools) do