Build a framework for a maintainable combat plugin

* Uses a hierarchy of WeaponClasses -> Weapons for performing attacks,
  with WeaponClass having a set of styles and associated Attacks for
  those styles. Weapons and their classes are built with an easy to use
  and clean DSL.

* Adds a BonusContainer mixin, so that Equipment, Weapons, and
  WeaponClasses can all have their own set of bonuses which apply to the
  player.

* Allows attacks to be queued to the Mobs CombatState instance from
  external code, allowing e.g., NPCs or auto-cast to queue attacks to be
  executed.

data/plugins/combat/combat_action.rb

@@ -0,0 +1,106 @@
+java_import 'org.apollo.game.action.Action'
+
+# Represents a one off {@code Attack}, which will not continue a combat session
+# upon completion.
+class AttackAction < Action
+
+  def initialize(source, target, delay, attack)
+    @source = source
+    @target = target
+    @delay  = delay
+    @attack = attack
+  end
+
+  def execute
+    begin
+      @attack.do(mob, @target)
+
+      stop
+    rescue AttackRequirementException => e
+      player.send_message e.message
+      stop
+    end
+  end
+end
+
+class CombatAction < Action
+  def initialize(source, attack = nil)
+    super(0, true, source)
+
+    @combat_state = get_combat_state(source)
+    @attack       = attack
+  end
+
+  def execute
+    if @combat_state.target.nil? and @combat_state.queued_attacks.empty?
+      @combat_state.reset
+      stop
+    end
+
+    case @combat_state.state
+      when :idle
+        update_idle
+      when :attacking
+        update_attacking
+      when :chasing
+        update_chasing
+      else
+        throw ArgumentError.new('invalid combat state')
+    end
+  end
+
+  def update_idle
+    if @combat_state.queued_attacks.empty? and @combat_state.supports_weapon
+      weapon       = EquipmentUtil.equipped_weapon mob
+      weapon_class = weapon.weapon_class
+      combat_style = weapon_class.style_at mob.combat_style
+
+      if mob.attacking
+        set_delay weapon_class.speed(combat_style) - 1
+      else
+        set_delay 0
+        mob.attacking = true
+      end
+
+      if mob.using_special and weapon.special_attack?
+        @combat_state.next_attack = weapon.special_attack
+      else
+        @combat_state.next_attack = weapon_class.attack(combat_style)
+      end
+
+      @combat_state.state = :attacking
+    elsif @combat_state.queued_attacks.size > 0
+      @combat_state.next_attack = @combat_state.queued_attacks.pop
+      @combat_state.state       = :attacking
+    else
+      stop
+      @combat_state.reset
+    end
+  end
+
+  def update_attacking
+    raise RuntimeError.new('no attack when in :attacking state') if @combat_state.next_attack.nil?
+
+    begin
+      @combat_state.next_attack.do(mob, @combat_state.target)
+
+      @combat_state.state = :idle
+      set_delay 0
+    rescue AttackRequirementException => e
+      mob.send_message e.message
+    end
+  end
+
+  def update_chasing
+
+  end
+
+  def stop
+    super
+
+    @combat_state.reset
+    mob.attacking = false
+    
+    puts 'stopped combat action'
+  end
+end