From 11255fd72268036c05b61ba6759ba4f42cebd32b Mon Sep 17 00:00:00 2001
From: Justin van der Leij <justinvanderleij@gmail.com>
Date: Tue, 2 Oct 2018 21:52:23 +0200
Subject: [PATCH] Optimized Lists. Added pool.added and .removed. Added
 entity:ensure

---
 TODO                            |  8 ++++++
 examples/simpleDrawing/init.lua | 22 ++++++++--------
 lib/entity.lua                  | 28 +++++++++++++++++---
 lib/instance.lua                |  4 +++
 lib/list.lua                    | 45 ++++++++++++++++++---------------
 lib/pool.lua                    |  9 +++++++
 lib/system.lua                  | 36 ++++++++++++++++----------
 7 files changed, 104 insertions(+), 48 deletions(-)
 create mode 100644 TODO

diff --git a/TODO b/TODO
new file mode 100644
index 0000000..4ef844e
--- /dev/null
+++ b/TODO
@@ -0,0 +1,8 @@
+[x] Modify pools and list to be more efficient
+[x] Rework Entity:give to remove any previous component and re-add it.
+[x] Add Entity:ensure (maybe?)
+[ ] Put pools in the Instance and invert dependency.
+[ ] Share pools between systems
+[ ] Remove System callbacks
+[x] Put .added and .removed in pools so they can be iterated over
+[ ] Implement assemblages
diff --git a/examples/simpleDrawing/init.lua b/examples/simpleDrawing/init.lua
index 9879f94..f9a2d9f 100644
--- a/examples/simpleDrawing/init.lua
+++ b/examples/simpleDrawing/init.lua
@@ -31,10 +31,7 @@ end)
 
 local RectangleRenderer = System({Position, Rectangle})
 function RectangleRenderer:draw()
-   local e
-   for i = 1, self.pool.size do
-      e = self.pool:get(i)
-
+   for _, e in ipairs(self.pool) do
       local position  = e:get(Position)
       local rectangle = e:get(Rectangle)
       local color     = e:get(Color)
@@ -49,11 +46,16 @@ function RectangleRenderer:draw()
 end
 
 local CircleRenderer = System({Position, Circle})
-function CircleRenderer:draw()
-   local e
-   for i = 1, self.pool.size do
-      e = self.pool:get(i)
+function CircleRenderer:flush()
+   for _, e in ipairs(self.pool.removed) do
+      print(tostring(e).. " was removed from my pool D:")
+   end
 
+   self:clear()
+end
+
+function CircleRenderer:draw()
+   for _, e in ipairs(self.pool) do
       local position = e:get(Position)
       local circle   = e:get(Circle)
       local color    = e:get(Color)
@@ -76,7 +78,7 @@ end
 function RandomRemover:update(dt)
    self.time = self.time + dt
 
-   if self.time >= 0.25 then
+   if self.time >= 0.5 then
       self.time = 0
 
       if self.pool.size > 0 then
@@ -115,4 +117,4 @@ for i = 1, 100 do
    end
 
    Game:addEntity(e)
-end
\ No newline at end of file
+end
diff --git a/lib/entity.lua b/lib/entity.lua
index 68fedeb..bfb9a07 100644
--- a/lib/entity.lua
+++ b/lib/entity.lua
@@ -22,6 +22,12 @@ function Entity.new()
    return e
 end
 
+local function give(e, component, ...)
+   local comp = component:__initialize(...)
+   e.components[component] = comp
+   e[component] = comp
+end
+
 --- Gives an Entity a component with values.
 -- @param component The Component to add
 -- @param ... The values passed to the Component
@@ -31,9 +37,25 @@ function Entity:give(component, ...)
       error("bad argument #1 to 'Entity:give' (Component expected, got "..type(component)..")", 2)
    end
 
-   local comp = component:__initialize(...)
-   self.components[component] = comp
-   self[component] = comp
+   if self[component] then
+      self:remove(component):apply()
+   end
+
+   give(self, component, ...)
+
+   return self
+end
+
+function Entity:ensure(component, ...)
+   if not Type.isComponent(component) then
+      error("bad argument #1 to 'Entity:ensure' (Component expected, got "..type(component)..")", 2)
+   end
+
+   if self[component] then
+      return self
+   end
+
+   give(self, component, ...)
 
    return self
 end
diff --git a/lib/instance.lua b/lib/instance.lua
index f2a947e..f4d63a0 100644
--- a/lib/instance.lua
+++ b/lib/instance.lua
@@ -92,6 +92,10 @@ function Instance:flush()
       end
    end
 
+   for i = 1, self.systems.size do
+      self.systems:get(i):flush()
+   end
+
    return self
 end
 
diff --git a/lib/list.lua b/lib/list.lua
index 33b2c10..a5698c9 100644
--- a/lib/list.lua
+++ b/lib/list.lua
@@ -7,18 +7,21 @@ local mt = {__index = List}
 -- @return A new list
 function List.new()
    return setmetatable({
-      objects  = {},
-      pointers = {},
-      size     = 0,
+      size = 0,
    }, mt)
 end
 
 --- Clears the List completely.
 -- @return self
 function List:clear()
-   self.objects  = {}
-   self.pointers = {}
-   self.size     = 0
+   for i = 1, self.size do
+      local o = self[i]
+
+      self[o] = nil
+      self[i] = nil
+   end
+
+   self.size = 0
 
    return self
 end
@@ -26,12 +29,12 @@ end
 --- Adds an object to the List.
 -- @param obj The object to add
 -- @return self
-function List:add(obj)
+function List:add(obj) -- obj can not be a number and also not the string "size"
    local size = self.size + 1
 
-   self.objects[size] = obj
-   self.pointers[obj] = size
-   self.size          = size
+   self[size] = obj
+   self[obj]  = size
+   self.size  = size
 
    return self
 end
@@ -40,22 +43,22 @@ end
 -- @param obj The object to remove
 -- @return self
 function List:remove(obj)
-   local index = self.pointers[obj]
-   if not index then return end 
+   local index = self[obj]
+   if not index then return end
    local size  = self.size
-   
+
    if index == size then
-      self.objects[size] = nil
+      self[size] = nil
    else
-      local other = self.objects[size]
+      local other = self[size]
 
-      self.objects[index]  = other
-      self.pointers[other] = index
+      self[index] = other
+      self[other] = index
 
-      self.objects[size] = nil
+      self[size] = nil
    end
 
-   self.pointers[obj] = nil
+   self[obj] = nil
    self.size = size - 1
 end
 
@@ -63,14 +66,14 @@ end
 -- @param index The index to look at
 -- @return The object at the index
 function List:get(index)
-   return self.objects[index]
+   return self[index]
 end
 
 --- Gets if the List has the object.
 -- @param obj The object to search for
 -- true if the list has the object, false otherwise
 function List:has(obj)
-   return self.pointers[obj] and true
+   return self[obj] and true
 end
 
 return setmetatable(List, {
diff --git a/lib/pool.lua b/lib/pool.lua
index c2d1ab4..5a7f44b 100644
--- a/lib/pool.lua
+++ b/lib/pool.lua
@@ -14,6 +14,9 @@ Pool.__index = Pool
 function Pool.new(name, filter)
    local pool = setmetatable(List(), Pool)
 
+   pool.added   = {}
+   pool.removed = {}
+
    pool.name   = name
    pool.filter = filter
 
@@ -22,6 +25,12 @@ function Pool.new(name, filter)
    return pool
 end
 
+function Pool:flush()
+   for i = 1, math.max(#self.added, #self.removed) do
+      self.added[i], self.removed[i] = nil, nil
+   end
+end
+
 --- Checks if an Entity is eligible for the Pool.
 -- @param e The Entity to check
 -- @return True if the entity is eligible, false otherwise
diff --git a/lib/system.lua b/lib/system.lua
index ac769ba..7c7b22a 100644
--- a/lib/system.lua
+++ b/lib/system.lua
@@ -66,7 +66,7 @@ end
 -- @param e The Entity to check
 -- @return True if the Entity was added, false if it was removed. Nil if nothing happend
 function System:__check(e)
-   local systemHas = self:__has(e)
+   local systemHas = self.__all[e]
 
    for _, pool in ipairs(self.__pools) do
       local poolHas  = pool:has(e)
@@ -74,23 +74,28 @@ function System:__check(e)
 
       if not poolHas and eligible then
          pool:add(e)
+         pool.added[#pool.added + 1] = e
+
          self:entityAddedTo(e, pool)
          self:__tryAdd(e)
       elseif poolHas and not eligible then
          pool:remove(e)
+         pool.removed[#pool.removed + 1] = e
+
          self:entityRemovedFrom(e, pool)
          self:__tryRemove(e)
       end
    end
 end
 
---- Removed an Entity from the System.
+--- Remove an Entity from the System.
 -- @param e The Entity to remove
 function System:__remove(e)
-   if self:__has(e) then
+   if self.__all[e] then
       for _, pool in ipairs(self.__pools) do
          if pool:has(e) then
             pool:remove(e)
+            pool.removed[#pool.removed + 1] = e
             self:entityRemovedFrom(e, pool)
          end
       end
@@ -103,7 +108,7 @@ end
 --- Tries to add an Entity to the System.
 -- @param e The Entity to add
 function System:__tryAdd(e)
-   if not self:__has(e) then
+   if not self.__all[e] then
       self.__all[e] = 0
       self:entityAdded(e)
    end
@@ -114,7 +119,7 @@ end
 --- Tries to remove an Entity from the System.
 -- @param e The Entity to remove
 function System:__tryRemove(e)
-   if self:__has(e) then
+   if self.__all[e] then
       self.__all[e] = self.__all[e] - 1
 
       if self.__all[e] == 0 then
@@ -124,19 +129,22 @@ function System:__tryRemove(e)
    end
 end
 
+function System:flush()
+   self:clear()
+end
+
+function System:clear()
+   for i = 1, #self.__pools do
+      self.__pools[i]:flush()
+   end
+end
+
 --- Returns the Instance the System is in.
 -- @return The Instance
 function System:getInstance()
    return self.__instance
 end
 
---- Returns if the System has the Entity.
--- @param e The Entity to check for
--- @return True if the System has the Entity. False otherwise
-function System:__has(e)
-   return self.__all[e] and true
-end
-
 --- Default callback for system initialization.
 -- @param ... Varags
 function System:init(...)
@@ -170,12 +178,12 @@ function System:addedTo(instance)
 end
 
 -- Default callback for when a System's callback is enabled.
--- @param callbackName The name of the callback that was enabled 
+-- @param callbackName The name of the callback that was enabled
 function System:enabledCallback(callbackName)
 end
 
 -- Default callback for when a System's callback is disabled.
--- @param callbackName The name of the callback that was disabled 
+-- @param callbackName The name of the callback that was disabled
 function System:disabledCallback(callbackName)
 end