-- Lua API
local _G = _G

-- WoW API
local IsInGroup = _G.IsInGroup
local IsInInstance = _G.IsInInstance
local UnitExists = _G.UnitExists
local UnitThreatSituation = _G.UnitThreatSituation

local UpdateColor = function(element, unit, status, r, g, b)
	if element.OverrideColor then
		return element:OverrideColor(unit, status, r, g, b)
	end

	-- Just some little trickery to easily support both textures and frames
	element[element.SetVertexColor and "SetVertexColor" or "SetBackdropBorderColor"](element, r, g, b)

	if element.PostUpdateColor then 
		element:PostUpdateColor(unit, status, r, g, b)
	end 
end

local Update = function(self, event, unit)
	if (not unit) or (unit ~= self.unit) then 
		return 
	end 

	local element = self.Threat
	if element.PreUpdate then
		element:PreUpdate(unit)
	end

	local status

	-- BUG: Non-existent '*target' or '*pet' units cause UnitThreatSituation() errors (thank you oUF!)
	if UnitExists(unit) and ((not element.hideSolo) or (IsInGroup() or IsInInstance())) then
		local feedbackUnit = element.feedbackUnit
		if (feedbackUnit and (feedbackUnit ~= unit) and UnitExists(feedbackUnit)) then
			status = UnitThreatSituation(feedbackUnit, unit)
		else
			status = UnitThreatSituation(unit)
		end
	end

	local r, g, b
	if (status and (status > 0)) then
		r, g, b = self.colors.threat[status][1], self.colors.threat[status][2], self.colors.threat[status][3]
		element:UpdateColor(unit, status, r, g, b)
		element:Show()
	else
		element:Hide()
	end
	
	if element.PostUpdate then
		return element:PostUpdate(unit, status, r, g, b)
	end	
end 

local Proxy = function(self, ...)
	return (self.Threat.Override or Update)(self, ...)
end 

local ForceUpdate = function(element)
	return Proxy(element._owner, "Forced", element._owner.unit)
end

local Enable = function(self)
	local element = self.Threat
	if element then
		element._owner = self
		element.ForceUpdate = ForceUpdate
		element.UpdateColor = UpdateColor
		self:RegisterEvent("UNIT_THREAT_SITUATION_UPDATE", Proxy)
		self:RegisterEvent("UNIT_THREAT_LIST_UPDATE", Proxy)
		return true
	end
end 

local Disable = function(self)
	local element = self.Threat
	if element then
		self:UnregisterEvent("UNIT_THREAT_SITUATION_UPDATE", Proxy)
		self:UnregisterEvent("UNIT_THREAT_LIST_UPDATE", Proxy)
		element:Hide()
	end
end 

-- Register it with compatible libraries
for _,Lib in ipairs({ (CogWheel("LibUnitFrame", true)), (CogWheel("LibNamePlate", true)) }) do 
	Lib:RegisterElement("Threat", Enable, Disable, Proxy, 10)
end 
