local _G = ShaguTweaks.GetGlobalEnv()
local T = ShaguTweaks.T
local API = ShaguTweaks.API
local LegacyCastingInfo = ShaguTweaks.UnitCastingInfo
local LegacyChannelInfo = ShaguTweaks.UnitChannelInfo

local module = ShaguTweaks:register({
  title = T["Enemy Castbars"],
  description = T["Shows an enemy castbar on target unit frame."],
  expansions = { ["vanilla"] = true },
  category = T["Unit Frames"],
  enabled = true,
})

local castbar = CreateFrame("StatusBar", "ShaguTargetCastbar", TargetFrame)
castbar:SetPoint("BOTTOM", TargetFrame, "BOTTOM", -12, -4)
castbar:SetStatusBarTexture("Interface\\TargetingFrame\\UI-StatusBar")
castbar:SetStatusBarColor(1, .8, 0, 1)
castbar:SetWidth(140)
castbar:SetHeight(10)
castbar:Hide()

castbar.texture = CreateFrame("Frame", nil, castbar)
castbar.texture:SetPoint("RIGHT", castbar, "LEFT", -2, 0)
castbar.texture:SetHeight(20)
castbar.texture:SetWidth(20)

castbar.texture.icon = castbar.texture:CreateTexture(nil, "BACKGROUND")
castbar.texture.icon:SetPoint("CENTER", 0, 0)
castbar.texture.icon:SetWidth(16)
castbar.texture.icon:SetHeight(16)
castbar.texture:SetBackdrop({
  edgeFile = "Interface\\Tooltips\\UI-Tooltip-Border",
  tile = true, tileSize = 8, edgeSize = 12,
  insets = { left = 3, right = 3, top = 3, bottom = 3 }
})

castbar.bg = castbar:CreateTexture(nil, "BACKGROUND")
castbar.bg:SetTexture("Interface\\TARGETINGFRAME\\UI-StatusBar")
castbar.bg:SetVertexColor(.1, .1, 0, .8)
castbar.bg:SetAllPoints(true)

castbar.spark = castbar:CreateTexture(nil, "OVERLAY")
castbar.spark:SetTexture("Interface\\CastingBar\\UI-CastingBar-Spark")
castbar.spark:SetWidth(20)
castbar.spark:SetHeight(20)
castbar.spark:SetBlendMode("ADD")

castbar.backdrop = CreateFrame("Frame", nil, castbar)
castbar.backdrop:SetFrameStrata("BACKGROUND")
castbar.backdrop:SetPoint("TOPLEFT", castbar, "TOPLEFT", -3, 3)
castbar.backdrop:SetPoint("BOTTOMRIGHT", castbar, "BOTTOMRIGHT", 3, -3)
castbar.backdrop:SetBackdrop({
  edgeFile = "Interface\\Tooltips\\UI-Tooltip-Border",
  tile = true, tileSize = 8, edgeSize = 12,
  insets = { left = 3, right = 3, top = 3, bottom = 3 }
})

castbar.text = castbar:CreateFontString(nil, "HIGH", "GameFontWhite")
castbar.text:SetPoint("CENTER", castbar, "CENTER", 0, 0)
local font, size = castbar.text:GetFont()
castbar.text:SetFont(font, size - 2, "THINOUTLINE")

local function QueryLegacy(query)
  if not query then return end

  local cast, nameSubtext, text, texture, startTime, endTime, isTradeSkill = LegacyCastingInfo(query)
  if cast then
    return cast, nameSubtext, text, texture, startTime, endTime, isTradeSkill, false
  end

  local channel
  channel, nameSubtext, text, texture, startTime, endTime, isTradeSkill = LegacyChannelInfo(query)
  if channel then
    return channel, nameSubtext, text, texture, startTime, endTime, isTradeSkill, true
  end
end

local function QueryCast(unit)
  if not unit then return end

  -- ClassicAPI is authoritative for real unit tokens and provides exact
  -- engine/server timing. A nil result for an existing unit means that exact
  -- GUID is not casting; don't fall back to the legacy name-keyed database,
  -- otherwise two NPCs with the same name can share one castbar incorrectly.
  if API and API.casts then
    local cast, nameSubtext, text, texture, startTime, endTime, isTradeSkill = API.GetCastInfo(unit)
    if cast then
      return cast, nameSubtext, text, texture, startTime, endTime, isTradeSkill, false
    end

    local channel
    channel, nameSubtext, text, texture, startTime, endTime, isTradeSkill = API.GetChannelInfo(unit)
    if channel then
      return channel, nameSubtext, text, texture, startTime, endTime, isTradeSkill, true
    end

    -- SuperWoW's GUID-keyed legacy cache is still safe because it cannot
    -- collide merely because two creatures share the same display name.
    if ShaguTweaks.superwow_active and not UnitIsUnit(unit, "player") then
      local guid = API.UnitGUID(unit)
      if guid then
        local a, b, c, d, e, f, g, h = QueryLegacy(guid)
        if a then return a, b, c, d, e, f, g, h end
      end
    end

    return
  end

  -- Compatibility path for environments without ClassicAPI cast support.
  if ShaguTweaks.superwow_active and not UnitIsUnit(unit, "player") then
    local guid = API and API.UnitGUID and API.UnitGUID(unit)
    if guid then
      local a, b, c, d, e, f, g, h = QueryLegacy(guid)
      if a then return a, b, c, d, e, f, g, h end
    end
  end

  return QueryLegacy(unit)
end

local function UpdatePosition()
  castbar:ClearAllPoints()
  castbar:SetPoint("BOTTOM", TargetFrame, "BOTTOM", -12, -4)

  local targetOfTarget = TargetofTargetFrame and TargetofTargetFrame:IsShown()
  local debuff11 = TargetFrameDebuff11 and TargetFrameDebuff11:IsShown()
  local debuff7 = TargetFrameDebuff7 and TargetFrameDebuff7:IsShown()
  local buff1 = TargetFrameBuff1 and TargetFrameBuff1:IsShown()

  if targetOfTarget then
    castbar:ClearAllPoints()
    castbar:SetPoint("BOTTOM", TargetFrame, "BOTTOM", -12, -24)
    if debuff11 then
      castbar:ClearAllPoints()
      castbar:SetPoint("BOTTOM", TargetFrame, "BOTTOM", -12, -45)
      if buff1 then
        castbar:ClearAllPoints()
        castbar:SetPoint("BOTTOM", TargetFrame, "BOTTOM", -12, -65)
      end
    end
  elseif debuff7 then
    castbar:ClearAllPoints()
    castbar:SetPoint("BOTTOM", TargetFrame, "BOTTOM", -12, -24)
  end
end

local function HideCast()
  castbar.startTime = nil
  castbar.endTime = nil
  castbar.isChannel = nil
  castbar:Hide()
end

local function UpdateProgress()
  local startTime = castbar.startTime
  local endTime = castbar.endTime
  if not startTime or not endTime or endTime <= startTime then
    HideCast()
    return
  end

  local now = GetTime()
  local max = endTime - startTime
  if now >= endTime then
    HideCast()
    return
  end

  local cur
  if castbar.isChannel then
    cur = endTime - now
  else
    cur = now - startTime
  end

  cur = cur > max and max or cur
  cur = cur < 0 and 0 or cur

  castbar:SetValue(cur)

  local percent = max > 0 and cur / max or 0
  local x = castbar:GetWidth() * percent
  castbar.spark:ClearAllPoints()
  castbar.spark:SetPoint("CENTER", castbar, "LEFT", x, 0)

  -- The target frame can move its buff/debuff rows while a cast is active.
  -- Repositioning the visible bar is cheap and keeps it attached correctly.
  UpdatePosition()
end

local function RefreshCast()
  if not UnitExists("target") then
    HideCast()
    return
  end

  local cast, nameSubtext, text, texture, startTime, endTime, isTradeSkill, isChannel = QueryCast("target")
  if not cast or not startTime or not endTime or endTime <= startTime then
    HideCast()
    return
  end

  castbar.startTime = startTime / 1000
  castbar.endTime = endTime / 1000
  castbar.isChannel = isChannel

  local max = castbar.endTime - castbar.startTime
  castbar:SetMinMaxValues(0, max)
  castbar.text:SetText(cast)

  if texture then
    castbar.texture.icon:SetTexture(texture)
    castbar.texture.icon:Show()
  else
    castbar.texture.icon:Hide()
  end

  UpdatePosition()
  castbar:Show()
  UpdateProgress()
end

module.enable = function(self)
  -- OnUpdate is now animation-only and runs only while the castbar is visible.
  -- Cast discovery is driven by ClassicAPI's UNIT_SPELLCAST_* events instead
  -- of querying the target's cast state on every rendered frame.
  castbar:SetScript("OnUpdate", UpdateProgress)

  local listener = CreateFrame("Frame")
  listener:RegisterEvent("PLAYER_TARGET_CHANGED")

  local castEvents = {
    "UNIT_SPELLCAST_START",
    "UNIT_SPELLCAST_STOP",
    "UNIT_SPELLCAST_INTERRUPTED",
    "UNIT_SPELLCAST_FAILED",
    "UNIT_SPELLCAST_DELAYED",
    "UNIT_SPELLCAST_CHANNEL_START",
    "UNIT_SPELLCAST_CHANNEL_STOP",
    "UNIT_SPELLCAST_CHANNEL_UPDATE",
  }

  local hasClassicCastEvents = false
  if API and API.eventutils and _G.C_EventUtils and _G.C_EventUtils.IsEventValid then
    for _, eventName in pairs(castEvents) do
      if _G.C_EventUtils.IsEventValid(eventName) then
        listener:RegisterEvent(eventName)
        hasClassicCastEvents = true
      end
    end
  end

  listener:SetScript("OnEvent", function()
    if event == "PLAYER_TARGET_CHANGED" then
      RefreshCast()
      return
    end

    -- ClassicAPI fans remote cast events out to every unit token currently
    -- resolving to the caster, including "target" when appropriate.
    if arg1 == "target" then
      RefreshCast()
    end
  end)

  if not hasClassicCastEvents then
    -- Compatibility fallback for older ClassicAPI builds: discover state at
    -- 20 Hz, while the bar itself still animates every frame when visible.
    listener.elapsed = 0
    listener:SetScript("OnUpdate", function()
      this.elapsed = this.elapsed + arg1
      if this.elapsed >= .05 then
        this.elapsed = 0
        RefreshCast()
      end
    end)
  end

  RefreshCast()
end