BNP = BNP or {}

-- Tank Mode for SuperWoW GUID nameplates.
-- Default: GREEN = hostile NPC currently targets the player, RED = another unit.
-- Optional Invert Tank Colors reverses those two states.
-- Idle hostile NPCs keep their normal Blizzard color.

local GREEN_R, GREEN_G, GREEN_B = 0.00, 1.00, 0.00
local RED_R, RED_G, RED_B = 1.00, 0.00, 0.00

local playerGUID = nil

local function GetPlayerGUID()
  local exists, guid = UnitExists("player")
  if exists and guid then playerGUID = guid end
  return playerGUID
end

local function GetPlateGUID(plate)
  if not plate or not plate.GetName then return nil end
  local guid = plate:GetName(1)
  if guid and guid ~= "" then return guid end
  return nil
end

local function GetTargetGUID(guid)
  if not guid then return nil end
  local exists, targetGUID = UnitExists(guid .. "target")
  if exists then return targetGUID end
  return nil
end

local function GetBar(plate)
  return plate and (plate.healthbar or plate.healthBar) or nil
end

local function IsHostileNPC(guid)
  if not guid or not UnitExists(guid) then return false end
  if UnitIsPlayer and UnitIsPlayer(guid) then return false end
  -- Player-controlled pets/guardians are not NPC tank targets. Treating them
  -- as hostile NPCs made Tank Mode overwrite their normal pet plate colors.
  if UnitPlayerControlled and UnitPlayerControlled(guid) then return false end
  return UnitCanAttack("player", guid) and true or false
end

local function IsForeignTaggedGUID(guid)
  if not guid or not UnitExists(guid) then return false end
  if UnitCanAttack and not UnitCanAttack("player", guid) then return false end
  if not UnitIsTapped or not UnitIsTapped(guid) then return false end
  if UnitIsTappedByPlayer and UnitIsTappedByPlayer(guid) then return false end
  return true
end

local function RestoreNormalColor(plate, bar)
  -- Do not restore a cached RGB value. Outside an active Tank Mode state,
  -- Blizzard owns the NPC healthbar color completely.
  plate.BNPTankActive = nil
  plate.BNPTankR = nil
  plate.BNPTankG = nil
  plate.BNPTankB = nil
end

local function ClearTankState(plate)
  if not plate then return end
  plate.BNPTankActive = nil
  plate.BNPTankR = nil
  plate.BNPTankG = nil
  plate.BNPTankB = nil
end

local function ApplyTankColor(plate, bar, r, g, b)
  bar:SetStatusBarColor(r, g, b, 1)
  plate.BNPTankActive = true
  plate.BNPTankR = r
  plate.BNPTankG = g
  plate.BNPTankB = b
end

local function EnforceTankColor(plate)
  if not plate or not plate.BNPTankActive then return end
  local bar = GetBar(plate)
  if not bar or not plate.BNPTankR then return end

  local r, g, b = bar:GetStatusBarColor()
  if math.abs(r - plate.BNPTankR) > 0.01
    or math.abs(g - plate.BNPTankG) > 0.01
    or math.abs(b - plate.BNPTankB) > 0.01 then
    bar:SetStatusBarColor(plate.BNPTankR, plate.BNPTankG, plate.BNPTankB, 1)
  end
end

function BNP:UpdateTankModePlate(plate)
  if not plate or not plate:IsShown() then return end

  local bar = GetBar(plate)
  if not bar then return end

  if not self:IsTankModeEnabled() then
    RestoreNormalColor(plate, bar)
    return
  end

  local guid = GetPlateGUID(plate)
  if not IsHostileNPC(guid) then
    -- NPC reaction colors belong to Blizzard. Never restore a stale cached
    -- Tank Mode color onto neutral/friendly/recycled nameplates.
    ClearTankState(plate)
    return
  end

  -- Foreign-tag grey has priority over Tank Mode. Previously Tank Mode wrote
  -- RED every 0.10s while fullalpha.lua restored GREY every frame, producing
  -- the visible grey/red flicker. Clear any cached tank color and let the
  -- foreign-tag renderer own the bar until the mob is ours/untapped again.
  if IsForeignTaggedGUID(guid) then
    ClearTankState(plate)
    return
  end

  local myGUID = GetPlayerGUID()
  if not myGUID then return end

  local targetGUID = GetTargetGUID(guid)
  local inverted = self:AreTankModeColorsInverted()

  if targetGUID and targetGUID == myGUID then
    if inverted then
      ApplyTankColor(plate, bar, RED_R, RED_G, RED_B)
    else
      ApplyTankColor(plate, bar, GREEN_R, GREEN_G, GREEN_B)
    end
  elseif targetGUID then
    if inverted then
      ApplyTankColor(plate, bar, GREEN_R, GREEN_G, GREEN_B)
    else
      ApplyTankColor(plate, bar, RED_R, RED_G, RED_B)
    end
  else
    RestoreNormalColor(plate, bar)
  end
end

function BNP:RefreshTankMode()
  local plate
  for plate in pairs(self.plates or {}) do
    if plate and plate:IsShown() then
      self:UpdateTankModePlate(plate)
    end
  end
end

function BNP:UpdateTankMode()
  self:RefreshTankMode()
end

function BNP:InstallTankMode()
  if self.BNPTankModeInstalled then return end
  if not self.libnameplate or not self.libnameplate.OnUpdate then return end

  GetPlayerGUID()

  table.insert(self.libnameplate.OnInit, function(plate)
    local current = plate or this
    if not current then return end

    ClearTankState(current)

    local bar = GetBar(current)
    if bar and not current.BNPTankColorHooked then
      local old = bar:GetScript("OnValueChanged")
      bar:SetScript("OnValueChanged", function()
        if old then old() end
        EnforceTankColor(current)
      end)
      current.BNPTankColorHooked = true
    end
  end)

  table.insert(self.libnameplate.OnShow, function(plate)
    local current = plate or this
    if not current then return end
    ClearTankState(current)
  end)

  table.insert(self.libnameplate.OnUpdate, function(plate, elapsed)
    local current = plate or this
    if not current then return end

    -- Tank Mode is optional. Avoid all GUID/target/tap queries while it is off.
    -- Only clean an old BNP-owned state if one is still present.
    if not BNP:IsTankModeEnabled() then
      if current.BNPTankActive then ClearTankState(current) end
      return
    end

    BNP:UpdateTankModePlate(current)
    EnforceTankColor(current)
  end)

  self.BNPTankModeInstalled = true
end