pfUI:RegisterModule("buff", function ()
  -- Hide Blizz
  BuffFrame:Hide()
  BuffFrame:UnregisterAllEvents()
  TemporaryEnchantFrame:Hide()
  TemporaryEnchantFrame:UnregisterAllEvents()

  local br, bg, bb, ba = GetStringColor(pfUI_config.appearance.border.color)

  -- Player aura slot ids, enumerated once per refresh pass (ScanPlayerAuraSlots)
  -- and read per button by its aura index: one GetAuraSlots walk per range
  -- instead of a by-index walk per button.
  local helpfulSlots, harmfulSlots = {}, {}
  local function ScanPlayerAuraSlots()
    ScanAuraSlots("player", "HELPFUL", helpfulSlots, 32)
    ScanAuraSlots("player", "HARMFUL", harmfulSlots, 16)
  end

  -- weapon enchants report only their time left, and no event as their
  -- charges and time run down, so the OnUpdate below refreshes their buttons
  -- too: the charges, and the timer when the enchant was renewed
  local function RefreshWeaponButton(buff, timeleft, charges)
    timeleft = (timeleft or 0) / 1000
    charges = charges or 0
    buff.stacks:SetText(charges > 1 and charges or "")

    local expires = GetTime() + timeleft
    if timeleft <= 0 then
      buff.cd:Clear()
      buff.cdExpires = nil
    elseif not buff.cdExpires or abs(buff.cdExpires - expires) > 1 then
      SetCooldownTimeLeft(buff.cd, timeleft)
      buff.cdExpires = expires
    end
    buff.cdStart = nil
  end

  local function RefreshBuffButton(buff)
    if buff.btype == "HELPFUL" then
      if C.buffs.separateweapons == "1" then
        buff.id = buff.gid - (buff.weapon ~= nil and buff.gid or 0)
      else
        buff.id = buff.gid - pfUI.buff.wepbuffs.count
      end
    else
      buff.id = buff.gid
    end

    if not buff.backdrop then
      CreateBackdrop(buff)
      CreateBackdropShadow(buff)
    end

    local slots = buff.btype == "HELPFUL" and helpfulSlots or harmfulSlots
    local name, icon, count, dispelType, duration, expirationTime, _, _, _, spellId = C_UnitAuras.UnitAuraBySlot("player", slots[buff.id])

    --detect weapon buffs
    if buff.btype == "HELPFUL" and ((C.buffs.separateweapons == "0" and buff.gid <= pfUI.buff.wepbuffs.count) or (pfUI.buff.wepbuffs.count > 0 and buff.weapon ~= nil)) then
        local mh, mhtime, mhcharge, oh, ohtime, ohcharge = GetWeaponEnchantInfo()
        if pfUI.buff.wepbuffs.count == 2 then
          if buff.gid == 1 then
            buff.mode = "MAINHAND"
          else
            buff.mode = "OFFHAND"
          end
        else
          if C.buffs.separateweapons == "0" then
            buff.mode = mh and "MAINHAND" or oh and "OFFHAND"
          else
            if buff.gid == 1 then
              buff.mode = mh and "MAINHAND" or oh and "OFFHAND"
            else
              buff:Hide()
              return
            end
          end
        end

      -- Set Weapon Texture, Border and Timer
      if buff.mode == "MAINHAND" then
        buff.texture:SetTexture(GetInventoryItemTexture("player", 16))
        buff.backdrop:SetBackdropBorderColor(GetItemQualityColor(GetInventoryItemQuality("player", 16) or 1))
        RefreshWeaponButton(buff, mhtime, mhcharge)
      elseif buff.mode == "OFFHAND" then
        buff.texture:SetTexture(GetInventoryItemTexture("player", 17))
        buff.backdrop:SetBackdropBorderColor(GetItemQualityColor(GetInventoryItemQuality("player", 17) or 1))
        RefreshWeaponButton(buff, ohtime, ohcharge)
      end
    elseif name and (( buff.btype == "HARMFUL" and C.buffs.debuffs == "1" ) or ( buff.btype == "HELPFUL" and C.buffs.buffs == "1" )) then
      -- Set Buff Texture and Border
      buff.mode = buff.btype
      buff.spellId = spellId
      buff.texture:SetTexture(icon)
      buff.stacks:SetText((count or 0) > 1 and count or "")

      if buff.btype == "HARMFUL" then
        local dispelColor = C_UnitAuras.GetAuraDispelTypeColor(dispelType)
        buff.backdrop:SetBackdropBorderColor(dispelColor:GetRGBA())
      else
        buff.backdrop:SetBackdropBorderColor(br,bg,bb,ba)
      end

      -- start the timer from the aura's duration; permanent auras have none
      local start, dur = GetAuraTimer(duration, expirationTime)
      if dur <= 0 then
        buff.cd:Clear()
        buff.cdStart = nil
      elseif buff.cdStart == nil or abs(buff.cdStart - start) > .5 or buff.cdDuration ~= dur then
        CooldownFrame_SetTimer(buff.cd, start, dur, 1)
        buff.cdStart = start
        buff.cdDuration = dur
      end
      buff.cdExpires = nil
    else
      buff:Hide()
      return
    end

    buff:Show()
  end

  local function CreateBuffButton(i, btype, weapon)
    local buttonName, buttonParent
    if btype == "HELPFUL" then
      if weapon == 1 then
        buttonName = "pfWepBuffFrame" .. i
        buttonParent = pfUI.buff.wepbuffs
      else
        buttonName = "pfBuffFrameBuff" .. i
        buttonParent = pfUI.buff.buffs
      end
    else
      buttonName = "pfDebuffFrameBuff" .. i
      buttonParent = pfUI.buff.debuffs
    end
    local buff = CreateFrame("Button", buttonName, buttonParent)
    buff.texture = buff:CreateTexture("BuffIcon" .. i, "BACKGROUND")
    buff.texture:SetTexCoord(.07,.93,.07,.93)
    buff.texture:SetAllPoints(buff)

    -- overlay lifts the stacks above the sweep: a child frame renders above
    -- all of its parent's own regions, so they would dim under the dark
    -- wedge otherwise
    buff.overlay = CreateFrame("Frame", nil, buff)
    buff.overlay:SetAllPoints(buff)

    buff.stacks = buff.overlay:CreateFontString(nil, "OVERLAY", "GameFontNormal")
    buff.stacks:SetTextColor(1,1,1,1)
    buff.stacks:SetJustifyH("RIGHT")
    buff.stacks:SetJustifyV("BOTTOM")
    buff.stacks:SetAllPoints(buff)

    -- the sweep and the duration numbers (the template covers the button and
    -- starts hidden); RefreshBuffButton starts its timer
    buff.cd = CreateCooldown(buff, "buff", buttonName .. "Cooldown")
    buff.cd:SetFrameLevel(buff:GetFrameLevel() + 1)
    buff.overlay:SetFrameLevel(buff:GetFrameLevel() + 2)

    buff:RegisterForClicks("RightButtonUp")

    buff.weapon = weapon
    buff.btype = btype
    buff.gid = i

    -- PERF: OnUpdate moved to consolidated parent frame handler (see pfUI.buff:SetScript("OnUpdate"))
    -- Individual buff frames no longer have their own OnUpdate

    buff:SetScript("OnEnter", function()
      GameTooltip:SetOwner(this, "ANCHOR_BOTTOMRIGHT")
      if this.mode == this.btype then
        GameTooltip:SetUnitAura("player", this.id, this.btype)

        if IsShiftKeyDown() then
          local aura = C_UnitAuras.GetAuraDataByIndex("player", this.id, this.btype)
          local playerlist = aura and GetUnbuffedRoster(aura.name) or ""
          if strlen(playerlist) > 0 then
            GameTooltip:AddLine(" ")
            GameTooltip:AddLine(T["Unbuffed"] .. ":", .3, 1, .8)
            GameTooltip:AddLine(playerlist,1,1,1,1)
            GameTooltip:Show()
          end
        end
      elseif this.mode == "MAINHAND" then
        GameTooltip:SetInventoryItem("player", 16)
      elseif this.mode == "OFFHAND" then
        GameTooltip:SetInventoryItem("player", 17)
      end
    end)

    buff:SetScript("OnLeave", GameTooltip_Hide)

    buff:SetScript("OnClick", function()
      if this.spellId then
        C_Spell.CancelSpellByID(this.spellId)
      end
    end)

    RefreshBuffButton(buff)

    return buff
  end

  pfUI.buff = CreateFrame("Frame", "pfGlobalBuffFrame", UIParent)
  pfUI.buff:RegisterEvent("PLAYER_AURAS_CHANGED")
  pfUI.buff:RegisterEvent("PLAYER_EQUIPMENT_CHANGED")
  pfUI.buff:RegisterUnitEvent("UNIT_MODEL_CHANGED", "player")
  pfUI.buff:RegisterEvent("BUFF_UPDATE_DURATION_SELF")
  pfUI.buff:RegisterEvent("DEBUFF_UPDATE_DURATION_SELF")
  pfUI.buff:SetScript("OnEvent", function()

    if C.buffs.weapons == "1" then
      local mh, mhtime, mhcharge, oh, ohtime, ohcharge = GetWeaponEnchantInfo()
      pfUI.buff.wepbuffs.count = (mh and 1 or 0) + (oh and 1 or 0)
    else
      pfUI.buff.wepbuffs.count = 0
    end

    ScanPlayerAuraSlots()

    for i=1,32 do
      RefreshBuffButton(pfUI.buff.buffs.buttons[i])
    end

    for i=1,16 do
      RefreshBuffButton(pfUI.buff.debuffs.buttons[i])
    end

    if C.buffs.separateweapons == "1" then
      for i=1,2 do
        RefreshBuffButton(pfUI.buff.wepbuffs.buttons[i])
      end
    end
  end)

  -- the buttons that can show a weapon enchant: the first two buffs, or the
  -- separate weapon buttons
  local weaponButtons

  -- weapon enchants, see RefreshWeaponButton
  pfUI.buff:SetScript("OnUpdate", function()
    local now = GetTime()
    if not this.nextUpdate then this.nextUpdate = now + 0.1 end
    if this.nextUpdate > now then return end
    this.nextUpdate = now + 0.1

    local _, mhtime, mhcharge, _, ohtime, ohcharge = GetWeaponEnchantInfo()
    for _, buff in ipairs(weaponButtons) do
      if buff:IsShown() then
        if buff.mode == "MAINHAND" then
          RefreshWeaponButton(buff, mhtime, mhcharge)
        elseif buff.mode == "OFFHAND" then
          RefreshWeaponButton(buff, ohtime, ohcharge)
        end
      end
    end
  end)

  -- CreateBuffButton refreshes each new button from the slot buffers
  ScanPlayerAuraSlots()

  -- Weapon Buffs
  pfUI.buff.wepbuffs = CreateFrame("Frame", "pfWepBuffFrame", UIParent)
  pfUI.buff.wepbuffs.count = 0
  pfUI.buff.wepbuffs.buttons = {}
  for i=1,2 do
    pfUI.buff.wepbuffs.buttons[i] = CreateBuffButton(i, "HELPFUL", 1)
  end

  -- Buff Frame
  pfUI.buff.buffs = CreateFrame("Frame", "pfBuffFrame", UIParent)
  pfUI.buff.buffs.buttons = {}
  for i=1,32 do
    pfUI.buff.buffs.buttons[i] = CreateBuffButton(i, "HELPFUL")
  end

  -- Debuffs
  pfUI.buff.debuffs = CreateFrame("Frame", "pfDebuffFrame", UIParent)
  pfUI.buff.debuffs.buttons = {}
  for i=1,16 do
    pfUI.buff.debuffs.buttons[i] = CreateBuffButton(i, "HARMFUL")
  end

  weaponButtons = {
    pfUI.buff.buffs.buttons[1], pfUI.buff.buffs.buttons[2],
    pfUI.buff.wepbuffs.buttons[1], pfUI.buff.wepbuffs.buttons[2],
  }

  -- config loading
  function pfUI.buff:UpdateConfigBuffButton(buff)
    local fontsize = C.buffs.fontsize == "-1" and C.global.font_size or C.buffs.fontsize
    local buffSize, buffSpacing = tonumber(C.buffs.size), tonumber(C.buffs.spacing)
    local rowextra = C.buffs.textinside == "1" and 0 or GetCooldownFontSize(buffSize) * 1.5
    local rowcount, relFrame, offsetX, offsetY
    if buff.btype == "HELPFUL" then
      if buff.weapon == 1 and C.buffs.separateweapons == "1" then
        rowcount = floor((buff.gid-1) / tonumber(C.buffs.wepbuffrowsize))
        relFrame = pfUI.buff.wepbuffs
        offsetX = -(buff.gid-1-rowcount*tonumber(C.buffs.wepbuffrowsize))*(buffSize+2*buffSpacing)
        offsetY = -(rowcount) * (rowextra+buffSize+2*buffSpacing)
      else
        rowcount = floor((buff.gid-1) / tonumber(C.buffs.buffrowsize))
        relFrame = pfUI.buff.buffs
        offsetX = -(buff.gid-1-rowcount*tonumber(C.buffs.buffrowsize))*(buffSize+2*buffSpacing)
        offsetY = -(rowcount) * (rowextra+buffSize+2*buffSpacing)
      end
    else
      rowcount = floor((buff.gid-1) / tonumber(C.buffs.debuffrowsize))
      relFrame = pfUI.buff.debuffs
      offsetX = -(buff.gid-1-rowcount*tonumber(C.buffs.debuffrowsize))*(buffSize+2*buffSpacing)
      offsetY = -(rowcount) * (rowextra+buffSize+2*buffSpacing)
    end
    buff:SetSize(buffSize, buffSize)
    buff:ClearAllPoints()
    buff:SetPoint("TOPRIGHT", relFrame, "TOPRIGHT",offsetX, offsetY)

    buff.stacks:SetFont(pfUI.font_default, fontsize+1, "OUTLINE")

    -- the duration numbers sit inside the icon or below it
    local countdown = buff.cd:GetCountdownFontString()
    countdown:ClearAllPoints()
    if C.buffs.textinside == "1" then
      countdown:SetPoint("CENTER", buff, "CENTER", 0, 0)
    else
      countdown:SetPoint("TOP", buff, "BOTTOM", 0, -3)
    end
  end

  function pfUI.buff:UpdateConfig()
    local spacing  = tonumber(C.buffs.spacing)
    local cell     = tonumber(C.buffs.size) + 2 * spacing
    local rowextra = C.buffs.textinside == "1" and 0 or GetCooldownFontSize(tonumber(C.buffs.size)) * 1.5

    local function SizeBuffFrame(frame, rowsize, count)
      rowsize = tonumber(rowsize)
      frame:SetSize(rowsize * cell, ceil(count / rowsize) * (rowextra + cell))
    end

    SizeBuffFrame(pfUI.buff.buffs, C.buffs.buffrowsize, 32)
    pfUI.buff.buffs:SetPoint("TOPRIGHT", pfUI.minimap or UIParent, "TOPLEFT", -4 * spacing, 0)
    UpdateMovable(pfUI.buff.buffs)

    SizeBuffFrame(pfUI.buff.debuffs, C.buffs.debuffrowsize, 16)
    pfUI.buff.debuffs:SetPoint("TOPRIGHT", pfUI.buff.buffs, "BOTTOMRIGHT", 0, 0)
    UpdateMovable(pfUI.buff.debuffs)

    if C.buffs.separateweapons == "1" then
      pfUI.buff.wepbuffs:ClearAllPoints()
      SizeBuffFrame(pfUI.buff.wepbuffs, C.buffs.wepbuffrowsize, 2)
      pfUI.buff.wepbuffs:SetPoint("TOPRIGHT", pfUI.buff.debuffs, "BOTTOMRIGHT", 0, 0)
      pfUI.buff.wepbuffs:Show()
      UpdateMovable(pfUI.buff.wepbuffs)
    else
      pfUI.buff.wepbuffs:Hide()
      RemoveMovable(pfUI.buff.wepbuffs)
    end

    for i=1,32 do
      pfUI.buff:UpdateConfigBuffButton(pfUI.buff.buffs.buttons[i])
    end

    for i=1,16 do
      pfUI.buff:UpdateConfigBuffButton(pfUI.buff.debuffs.buttons[i])
    end

    for i=1,2 do
      pfUI.buff:UpdateConfigBuffButton(pfUI.buff.wepbuffs.buttons[i])
    end

    pfUI.buff:GetScript("OnEvent")()
  end

  pfUI.buff:UpdateConfig()
end)