Implement refreshing auras declaratively

This is the fifth version of the Aura API

We are not deprecating the old system yet, although this is preferrable
over attribute-script based modifiers where relevant.

Previously, we would create an attribute script for atk/cost for some
cards and return a modified value based on the board. For example,
Old Murk-Eye would consistently have its attack depend on the number
of murlocs on the board.

This is a problem for three reasons:
 - It's ugly in the DSL. You'd have to filter the board with race=Race.MURLOC,
   exclude self, etc. The new system allows for reuse of selectors.
 - Attribute scripts are constantly "on". Murk-Eye would then have 3 atk in
   the hand, Mountain Giant would have its cost reduced on the board, etc.
 - We currently have to create custom cards for every single buff. That's a
   huge hassle, and problematic for Kettle.

fireplace/aura.py

@@ -1,3 +1,4 @@
+from .managers import CardManager
 from .utils import CardList, fireplace_logger as logger
 
 
@@ -71,3 +72,63 @@ def destroy(self):
 		del self._buffs
 		del self._buffed
 		self.source.auras.remove(self)
+
+
+class AuraBuff:
+	def __init__(self, source, entity):
+		self.source = source
+		self.entity = entity
+		self.tags = CardManager(self)
+
+	def __repr__(self):
+		return "<AuraBuff on %r from %r>" % (self.entity, self.source)
+
+	def update_tags(self, tags):
+		self.tags.update(tags)
+		self.tick = self.source.game.tick
+
+	def destroy(self):
+		self.entity.slots.remove(self)
+		self.source.game.active_aura_buffs.remove(self)
+
+	def _getattr(self, attr, i):
+		value = getattr(self, attr, 0)
+		if callable(value):
+			return value(self.entity, i)
+		return i + value
+
+
+class Refresh:
+	"""
+	Refresh a buff or a set of tags on an entity
+	"""
+	def __init__(self, selector, tags):
+		self.selector = selector
+		self.tags = tags
+
+	def trigger(self, source):
+		entities = self.selector.eval(source.game, source)
+		for entity in entities:
+			tags = {}
+			for tag, value in self.tags.items():
+				if not isinstance(value, int) and not callable(value):
+					value = value.evaluate(source)
+				tags[tag] = value
+
+			entity.refresh_buff(source, tags)
+
+
+class TargetableByAuras:
+	def refresh_buff(self, source, tags):
+		for slot in self.slots[:]:
+			if isinstance(slot, AuraBuff) and slot.source is source:
+				slot.update_tags(tags)
+				# Move the buff position at the end again
+				self.slots.remove(slot)
+				self.slots.append(slot)
+				break
+		else:
+			buff = AuraBuff(source, self)
+			buff.update_tags(tags)
+			self.slots.append(buff)
+			source.game.active_aura_buffs.append(buff)

fireplace/card.py

@@ -1,7 +1,7 @@
 from itertools import chain
 from . import cards as CardDB, rules
 from .actions import Damage, Deaths, Destroy, Heal, Morph, Play, Shuffle, SetCurrentHealth
-from .aura import Aura
+from .aura import Aura, TargetableByAuras
 from .entity import Entity, boolean_property, int_property
 from .enums import CardType, PlayReq, Race, Rarity, Zone
 from .managers import CardManager
@@ -120,7 +120,7 @@ def buff(self, target, buff, **kwargs):
 		return ret
 
 
-class PlayableCard(BaseCard):
+class PlayableCard(BaseCard, TargetableByAuras):
 	windfury = boolean_property("windfury")
 
 	def __init__(self, id, data):

fireplace/game.py

@@ -33,6 +33,8 @@ def __init__(self, players):
 		self.auras = []
 		self.minions_killed_this_turn = CardList()
 		self.no_aura_refresh = False
+		self.tick = 0
+		self.active_aura_buffs = []
 
 	def __repr__(self):
 		return "%s(players=%r)" % (self.__class__.__name__, self.players)
@@ -211,6 +213,14 @@ def refresh_auras(self):
 			return
 		for aura in self.auras:
 			aura.update()
+		for entity in self.entities:
+			if entity.data and hasattr(entity.data.scripts, "update"):
+				if not entity.silenced:
+					entity.data.scripts.update.trigger(entity)
+		for buff in self.active_aura_buffs[:]:
+			if buff.tick < self.tick:
+				buff.destroy()
+		self.tick += 1
 
 	def prepare(self):
 		self.players[0].opponent = self.players[1]

fireplace/player.py

@@ -1,6 +1,7 @@
 import random
 from itertools import chain
 from .actions import Draw, Give, Steal, Summon
+from .aura import TargetableByAuras
 from .card import Card
 from .deck import Deck
 from .entity import Entity
@@ -11,7 +12,7 @@
 from .utils import CardList
 
 
-class Player(Entity):
+class Player(Entity, TargetableByAuras):
 	Manager = PlayerManager
 	extra_deathrattles = slot_property("extra_deathrattles")
 	healing_double = slot_property("healing_double", sum)