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-- Module: Transparency
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local ADDON_NAME, Addon = ...

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-- Imported functions and constants
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-- Lua APIs

-- WoW APIs
local UnitExists = UnitExists

-- ThreatPlates APIs
local Style = Addon.Style
local AnimationFadePlate, AnimationStopFade = Addon.Animation.FadePlate, Addon.Animation.StopFade
local CVars = Addon.CVars
local SubscribeEvent, PublishEvent = Addon.EventService.Subscribe, Addon.EventService.Publish
local MathClamp = Addon.Clamp

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-- Module Setup
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local TransparencyModule = Addon.Transparency

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-- Local variables
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local UpdatePlate_SetAlpha, UpdatePlate_InitializeAlpha, UpdatePlate_Transparency

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-- Cached configuration settings (for performance reasons)
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local Settings, FadingIsEnabled
local SettingsOccludedAlpha, SettingsEnabledOccludedAlpha, FadeInOccludedUnitsIsEnabled, FadeOutOccludedUnitsIsEnabled
-- Cached CVARs
local CVAR_NameplateOccludedAlphaMult

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-- Functions handling transparency of nameplates
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local function TransparencySituational(unit)
	local db = Addon.db.profile.nameplate

	-- Do checks for situational transparency settings:
	if unit.TargetMarkerIcon and db.toggle.MarkedA then
		return db.alpha.Marked
	elseif unit.isMouseover and not Addon.UnitIsTarget(unit.unitid) and db.toggle.MouseoverUnitAlpha then
		return db.alpha.MouseoverUnit
	elseif unit.isCasting then
		local unit_friendly = (unit.reaction == "FRIENDLY")
		if unit_friendly and db.toggle.CastingUnitAlpha then
			return db.alpha.CastingUnit
		elseif not unit_friendly and db.toggle.CastingEnemyUnitAlpha then
			return db.alpha.CastingEnemyUnit
		end
	end

	return nil
end

local function TransparencyGeneral(unit)
  -- Target always has priority
  if not Addon.UnitIsTarget(unit.unitid) then
    -- Do checks for situational transparency settings:
    local tranparency = TransparencySituational(unit)
    if tranparency then
      return tranparency
    end
  end

	-- Do checks for target settings:
	local db = Addon.db.profile.nameplate

  local target_alpha
	if Addon.TargetUnitExists() then
    local unit_is_target = Addon.UnitIsTarget(unit.unitid)
    if unit_is_target and db.toggle.TargetA then
      target_alpha = db.alpha.Target
    elseif not unit_is_target and db.toggle.NonTargetA then
      target_alpha = db.alpha.NonTarget
    end
	elseif db.toggle.NoTargetA then
		target_alpha = db.alpha.NoTarget
	end

	if target_alpha then
		--if db.alpha.AddTargetAlpha then
    if db.alpha.AbsoluteTargetAlpha then
			-- units will always be set to this alpha
      return target_alpha
    end
    return (db.alpha[unit.TP_DetailedUnitType] or 1) + target_alpha - 1
  end

	return db.alpha[unit.TP_DetailedUnitType] or 1
end

local function TransparencyThreat(unit, style)
	local db = Addon.db.profile.threat

	if not db.useAlpha then
		return TransparencyGeneral(unit)
	end

	if db.marked.alpha then
		local transparency = TransparencySituational(unit)
		if transparency then
			return transparency
		end
	end

  local alpha = db[style].alpha[unit.ThreatLevel]

  if db.AdditiveAlpha then
    alpha = alpha + TransparencyGeneral(unit) - 1
  end

  return alpha
end

local function AlphaNormal(unit, non_combat_transparency)
  local style = Style:GetThreatStyle(unit)
  if style == "normal" then
    return non_combat_transparency or TransparencyGeneral(unit)
  else -- dps, tank
    return TransparencyThreat(unit, style)
  end
end

local function AlphaUnique(unit)
	local unique_setting = unit.CustomPlateSettings

	if unique_setting.overrideAlpha then
		return AlphaNormal(unit)
	elseif unique_setting.UseThreatColor then
    return AlphaNormal(unit, unique_setting.alpha)
  end

  return unique_setting.alpha
end

local function AlphaUniqueNameOnly(unit)
	local unique_setting = unit.CustomPlateSettings

  if unique_setting.overrideAlpha then
    local db = Addon.db.profile.HeadlineView
    if db.useAlpha then
			return AlphaNormal(unit)
    end

    return 1
	elseif unique_setting.UseThreatColor then
    return AlphaNormal(unit, unique_setting.alpha)
  end

  return unique_setting.alpha
end

local function TransparencyEmpty(unit)
	return 0
end

local function TransparencyNameOnly(unit)
	local db = Addon.db.profile.HeadlineView

	if db.useAlpha then
    return AlphaNormal(unit)
  end

	return 1
end

local ALPHA_FUNCTIONS = {
	dps = TransparencyThreat,
	tank = TransparencyThreat,
	normal = TransparencyGeneral,
	totem = TransparencyGeneral,
	unique = AlphaUnique,
	empty = TransparencyEmpty,
	etotem = TransparencyGeneral,
	NameOnly = TransparencyNameOnly,
	["NameOnly-Unique"] = AlphaUniqueNameOnly,
}

local function GetTransparency(unit)
  return MathClamp(ALPHA_FUNCTIONS[unit.style](unit, unit.style), 0, 1)
end

local function UpdatePlate_SetAlphaWithFading(tp_frame, unit)
  local target_alpha = GetTransparency(unit)

  if target_alpha ~= tp_frame.CurrentAlpha then
    AnimationFadePlate(tp_frame, target_alpha)
    tp_frame.CurrentAlpha = target_alpha
  end
end

-- local function UpdatePlate_InitializeAlphaWithFading(tp_frame, unit)
--   local target_alpha = GetTransparency(unit)

--   Animations:ShowPlate(tp_frame, target_alpha)
--   --tp_frame.CurrentAlpha = target_alpha
-- end

local function UpdatePlate_SetAlphaNoFading(tp_frame, unit)
  local target_alpha = GetTransparency(unit)

  if target_alpha ~= tp_frame.CurrentAlpha then
    tp_frame:SetAlpha(target_alpha)
    tp_frame.CurrentAlpha = target_alpha
  end
end

local	function UpdatePlate_SetAlphaWithOcclusion(tp_frame, unit)
  if not tp_frame:IsShown() or (tp_frame.IsOccluded and not Addon.UnitIsTarget(unit.unitid)) then
    return
  end

  UpdatePlate_SetAlpha(tp_frame, unit)
end

local function SetOccludedTransparencyWithFadingOnUpdate(self, frame)
  if not SettingsEnabledOccludedAlpha then return end

  local target_alpha
  local plate_alpha = frame.Parent:GetAlpha()
  local unit_was_occluded = false

  if plate_alpha < (CVAR_NameplateOccludedAlphaMult + 0.05) then
    frame.IsOccluded = true
    target_alpha = SettingsOccludedAlpha
  -- elseif frame.IsOccluded or not frame.CurrentAlpha then
    -- unit_was_occluded = frame.IsOccluded
    -- frame.IsOccluded = false
    -- target_alpha = GetTransparency(frame.unit)

  -- plate_alpha >= (CVAR_NameplateOccludedAlphaMult + 0.05)
  elseif frame.IsOccluded then
    frame.IsOccluded = false
    unit_was_occluded = true
    target_alpha = GetTransparency(frame.unit)
  -- elseif not frame.CurrentAlpha then
  --   frame.IsOccluded = false
  --   unit_was_occluded = false
  --   target_alpha = GetTransparency(frame.unit)
  end

  if target_alpha and target_alpha ~= frame.CurrentAlpha then
    if (frame.IsOccluded and not FadeOutOccludedUnitsIsEnabled) or (unit_was_occluded and not FadeInOccludedUnitsIsEnabled) then
      AnimationStopFade(frame)
      frame:SetAlpha(target_alpha)
      frame.IsShowing = false
    elseif frame.IsShowing then
      AnimationStopFade(frame)
      frame:SetAlpha(target_alpha)

      -- Disable showing only if plate is not occluded at least once
      if unit_was_occluded then
        frame.IsShowing = false
      end
    else
      AnimationFadePlate(frame, target_alpha)
      frame.IsShowing = false
    end

    frame.CurrentAlpha = target_alpha
  end
end

local function SetOccludedTransparencyWithoutFadingOnUpdate(self, frame)
  if not SettingsEnabledOccludedAlpha then return end

  local target_alpha
  local plate_alpha = frame.Parent:GetAlpha()

  if plate_alpha < (CVAR_NameplateOccludedAlphaMult + 0.05) then
    frame.IsOccluded = true
    target_alpha = SettingsOccludedAlpha
  elseif frame.IsOccluded or not frame.CurrentAlpha then
    frame.IsOccluded = false
    target_alpha = GetTransparency(frame.unit)
  end

  if target_alpha and target_alpha ~= frame.CurrentAlpha then
    frame:SetAlpha(target_alpha)
    frame.CurrentAlpha = target_alpha
  end
end

function TransparencyModule.UpdateStyle(frame)
  AnimationStopFade(frame)
  frame:SetAlpha(0)

  frame.CurrentAlpha = nil
  frame.IsOccluded = false
  frame.IsShowing = true

  -- Plate is not yet shown here and not yet occluded, so adjust the alpha with or without fading
  UpdatePlate_InitializeAlpha(frame, frame.unit)
  -- Also initialize occlusion here to avoid a short flicker of the nameplate if occlusion is enabled
  SetOccludedTransparencyWithoutFadingOnUpdate(TransparencyModule, frame)
end

function TransparencyModule.UpdateSettings()
  Settings = Addon.db.profile

  CVAR_NameplateOccludedAlphaMult = CVars:GetAsNumber("nameplateOccludedAlphaMult")

  FadingIsEnabled = Settings.Animations.FadeToDuration > 0

  UpdatePlate_InitializeAlpha = UpdatePlate_SetAlphaNoFading
  if FadingIsEnabled then
    UpdatePlate_SetAlpha = UpdatePlate_SetAlphaWithFading
    --UpdatePlate_InitializeAlpha = UpdatePlate_InitializeAlphaWithFading
    TransparencyModule.SetOccludedTransparency = SetOccludedTransparencyWithFadingOnUpdate
  else
    UpdatePlate_SetAlpha = UpdatePlate_SetAlphaNoFading
    --UpdatePlate_InitializeAlpha = UpdatePlate_SetAlphaNoFading
    TransparencyModule.SetOccludedTransparency = SetOccludedTransparencyWithoutFadingOnUpdate
  end

  SettingsEnabledOccludedAlpha = Settings.nameplate.toggle.OccludedUnits
  SettingsOccludedAlpha = Settings.nameplate.alpha.OccludedUnits

  if SettingsEnabledOccludedAlpha then
    if CVars.InvalidCVarsForOcclusionDetection() then
      SettingsEnabledOccludedAlpha = false
      UpdatePlate_Transparency = UpdatePlate_SetAlpha
    else
      UpdatePlate_Transparency = UpdatePlate_SetAlphaWithOcclusion
    end
  else
    UpdatePlate_Transparency = UpdatePlate_SetAlpha
  end

  FadeInOccludedUnitsIsEnabled = Settings.Animations.FadeInOccludedUnits
  FadeOutOccludedUnitsIsEnabled = Settings.Animations.FadeOutOccludedUnits
end

function TransparencyModule.OcclusionDetectionIsEnabled()
	return SettingsEnabledOccludedAlpha
end

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-- React to events that could change the nameplate scale/size
---------------------------------------------------------------------------------------------------

-- Move UpdatePlate_SetAlpha to this file
local function SituationalEvent(tp_frame)
  if not tp_frame:IsShown() or (tp_frame.IsOccluded and not Addon.UnitIsTarget(tp_frame.unit.unitid)) then
    return
  end

  local target_alpha = GetTransparency(tp_frame.unit)

	if target_alpha ~= tp_frame.CurrentAlpha then
    if FadingIsEnabled then
      AnimationStopFade(tp_frame)
    end
		tp_frame:SetAlpha(target_alpha)
		tp_frame.CurrentAlpha = target_alpha
    --tp_frame.IsShowing = false
	end
end

-- Update the target unit and all non-target units
local function TargetGained(tp_frame)
  -- Update the nameplate of the current target unit
  SituationalEvent(tp_frame)

  local db = Addon.db.profile.nameplate
  if db.toggle.NonTargetA then
    -- Update all non-target units
    for _, active_tp_frame in Addon:GetActiveThreatPlates() do
      if not Addon.UnitIsTarget(active_tp_frame.unit.unitid) then
        SituationalEvent(active_tp_frame)
      end
    end
  end
end

-- Update all units unless there is a new target unit (TargetGained will be called then anyway)
local function TargetLost(tp_frame)
  -- Update the nameplate of the unit that lost the target
  SituationalEvent(tp_frame)

  if UnitExists("target") then return end

  -- Update all units as there is no target now (except the unit that lost the target as it was already updated above
  for _, active_tp_frame in Addon:GetActiveThreatPlates() do
    if active_tp_frame ~= tp_frame then
      SituationalEvent(active_tp_frame)
    end
  end
end

SubscribeEvent(TransparencyModule, "MouseoverOnEnter", SituationalEvent)
SubscribeEvent(TransparencyModule, "MouseoverOnLeave", SituationalEvent)
SubscribeEvent(TransparencyModule, "CastingStarted", SituationalEvent)
SubscribeEvent(TransparencyModule, "CastingStopped", SituationalEvent)
SubscribeEvent(TransparencyModule, "TargetMarkerUpdate", SituationalEvent)
SubscribeEvent(TransparencyModule, "TargetGained", TargetGained)
SubscribeEvent(TransparencyModule, "TargetLost", TargetLost)
SubscribeEvent(TransparencyModule, "FactionUpdate", SituationalEvent)
SubscribeEvent(TransparencyModule, "ThreatUpdate", SituationalEvent)
