MindState: Untested attempt at adding stackable states

MindState.lua

@@ -13,7 +13,9 @@ require 'MiddleClass.lua'
 ]]
 StatefulObject = class('StatefulObject')
 
-StatefulObject.states = {} -- the root state list
+StatefulObject.states = {} -- the root state list
+
+local private = setmetatable({}, {__mode = "k"})   -- weak table storing private references
 
 -- Instance methods
 
@@ -25,7 +27,10 @@ StatefulObject.states = {} -- the root state list
 function StatefulObject:initialize(initParameters)
   super.initialize(self)
   initParameters = initParameters or {} --initialize to empty table if nil
-  self.states = {}
+  self.states = {}
+  private[self] = {
+    stateStack = {}
+  }
   for stateName,stateClass in pairs(self.class.states) do 
     local state = stateClass:new(unpack(initParameters[stateName] or {}))
     state.name = stateName
@@ -37,29 +42,116 @@ end
   If the current state has a method called onExitState, it will be called, with the instance as a parameter.
   If the "next" state exists and has a method called onExitState, it will be called, with the instance as a parameter.
   use gotoState(nil) for setting states to nothing
-  This method invokes the exitState and enterState functions if they exist on the current state
+  This method invokes the exitState and enterState functions if they exist on the current state
+  Second parameter is optional. If true, the stack will be conserved. Otherwise, it will be popped.
 ]]
-function StatefulObject:gotoState(stateName)
+function StatefulObject:gotoState(newStateName, keepStack)
   assert(self.states~=nil, "Attribute 'states' not detected. check that you called instance:gotoState and not instance.gotoState, and that you invoked super.initialize(self) in the constructor.")
-
-  local nextState
-  if(stateName~=nil) then
-    nextState = self.states[stateName]
-    assert(nextState~=nil, "State '" .. stateName .. "' not found")
-  end
-
-  local prevState = self.currentState
-  if(prevState~=nil and type(prevState.exitState) == "function") then
-    prevState.exitState(self)
-  end
 
-  self.previousState = prevState
-  self.currentState = nextState
-
-  if(nextState~=nil and type(nextState.enterState) == "function") then
-    nextState.enterState(self)
+  local prevState = self:getCurrentState()
+
+  -- If we're trying to go to a state in which we already are, return (do nothing)
+  if(prevState~=nil and prevState.name == newStateName) then return end
+
+  local nextState
+  if(newStateName~=nil) then
+    nextState = self.states[newStateName]
+    assert(nextState~=nil, "State '" .. newStateName .. "' not found")
   end
+
+  -- Invoke exitState on the previous state
+  if(prevState~=nil and type(prevState.exitState) == "function") then prevState.exitState(self, newStateName) end
+
+  -- Empty the stack unless keepStack is true.
+  if(keepStack~=true) then self:popAllStates() end
+
+  -- replace the top of the stack with the new state
+  local stack = private[self].stateStack
+  stack[math.max(#stack,1)] = nextState
+
+  -- Invoke enterState on the new state. 2nd parameter is the name of the previous state, or nil
+  if(nextState~=nil and type(nextState.enterState) == "function") then
+    nextState.enterState(self, prevState~=nil and prevState.name or nil)
+  end
+end
+
+function StatefulObject:pushState(newStateName)
+  assert(type(newState)=='string', "newStateName must be a string.")
+  assert(self.states~=nil, "Attribute 'states' not detected. check that you called instance:pushState and not instance.pushState, and that you invoked super.initialize(self) in the constructor.")
+
+  local nextState = self.states[newStateName]
+  assert(nextState~=nil, "State '" .. newStateName .. "' not found")
+
+  -- If we attempt to push a state and the state is already on return (do nothing)
+  local stack = private[self].stateStack
+  for _,state in ipairs(stack) do 
+    if(state.name == newStateName) then return end
+  end
+
+  -- Invoke pausedState on the previous state
+  local prevState = self:getCurrentState()
+  if(prevState~=nil and type(prevState.pausedState) == "function") then prevState.pausedState(self) end
+
+  -- Do the push
+  table.insert(stack, nextState)
+
+  -- Invoke pushState on the next state
+  if(type(nextState.pushedState) == "function") then nextState.pushedState(self) end
+  
+  return nextState
+end
+
+-- If a state name is given, it will attempt to remove it from the stack. If not found on the stack it will do nothing.
+-- If no state name is give, this pops the top state from the stack, if any. Otherwise it does nothing.
+-- Callbacks will be called when needed.
+function StatefulObject:popState(stateName)
+  assert(self.states~=nil, "Attribute 'states' not detected. check that you called instance:popState and not instance.popState, and that you invoked super.initialize(self) in the constructor.")
+
+  -- Invoke poppedState on the previous state
+  local prevState = self:getCurrentState()
+  if(prevState~=nil and type(prevState.poppedState) == "function") then prevState.poppedState(self) end
+
+  -- Do the pop
+  local stack = private[self].stateStack
+  table.remove(stack, #stack)
+
+  -- Invoke continuedState on the new state
+  local newState = self:getCurrentState()
+  if(newState~=nil and type(newState.continuedState) == "function") then newState.continuedState(self) end
+  
+  return newState
+end
+
+function StatefulObject:popAllStates()
+  local state = self:popState()
+  while(state~=nil) do state = self:popState() end
+end
+
+function StatefulObject:getCurrentState()
+  local stack = private[self].stateStack
+  if #stack == 0 then return nil end
+  return(stack[#stack])
 end
+
+--[[
+  Returns true if the object is in the state named 'stateName'
+  If second(optional) parameter is true, this method returns true if the state is on the stack instead
+]]
+function StatefulObject:inState(stateName, testStateStack)
+  local stack = private[self].stateStack
+
+  if(testStateStack==true) then
+    for _,state in ipairs(stack) do 
+      if(state.name == stateName) then return true end
+    end
+  else --testStateStack==false
+    local state = stack[#stack]
+    if(state~=nil and state.name == stateName) then return true end
+  end
+
+  return false
+end
+
 
 -- Class methods
 
@@ -77,8 +169,13 @@ function StatefulObject:addState(stateName, superState)
   return state
 end
 
-
-local ignoredMethods = {states=1, initialize=1, gotoState=1, addState=1, subclass=1, includes=1, exitState=1, enterState=1}
+-- These methods will not be overriden by the states.
+local ignoredMethods = {
+  states=1, initialize=1,
+  gotoState=1, pushState=1, popState=1, popAllStates=1, getCurrentState=1, inState=1,
+  enterState=1, exitState=1, pushedState=1, poppedState=1, pausedState=1, continuedState=1,
+  addState=1, subclass=1, includes=1
+}
 local prevSubclass = StatefulObject.subclass
 --[[ creates a stateful subclass
   Subclasses inherit all the states of their superclases, in a special way:
@@ -97,17 +194,18 @@ function StatefulObject:subclass(name)
 
   --make sure that the currentState is used on the method lookup function before looking on the class dict
   local classDict = theClass.__classDict
-  classDict.__index = function(instance, method)
-    --first look on the current state
-    local currentState = rawget(instance, 'currentState')
-    if( currentState~=nil and
-        currentState[method]~=nil and
-        ignoredMethods[method]==nil) then
-      return currentState[method]
-    else
-    --if not found, look on the class itself
-      return classDict[method]
+  classDict.__index = function(instance, methodName)
+    -- If the method isn't on the 'ignoredMethods' list, look through the stack to see if it is defined
+    if(ignoredMethods[methodName]~=1) then
+      local stack = private[instance].stateStack
+      local method
+      for i = #stack,1,-1 do -- reversal loop
+        method = stack[i][methodName]
+        if(method~=nil) then return method end
+      end
     end
+    --if ignored or not found, look on the class itself
+    return classDict[methodName]
   end
 
   return theClass
@@ -119,19 +217,19 @@ end
      then each member of that module.states is included on the StatefulObject class.
      If module.states has a state that doesn't exist on StatefulObject, a new state will be created.
 ]]
-function StatefulObject:includes(module)
+function StatefulObject:includes(module, ...)
   assert(subclassOf(StatefulObject, self), "Use class:includes instead of class.includes")
   for methodName,method in pairs(module) do
     if methodName ~="included" and methodName ~= "states" then
       self[methodName] = method
     end
   end
-  if type(module.included)=="function" then module:included(self) end
+  if type(module.included)=="function" then module.included(self, ...) end
   if type(module.states)=="table" then
     for stateName,moduleState in pairs(module.states) do 
       local state = self.states[stateName]
       if(state==nil) then state = theClass:addState(stateName) end
-      state:includes(moduleState)
+      state:includes(moduleState, ...)
     end
   end
 end