-- ============================================================================
-- MSUF RangeFade v4 — Minimal C-API overhead
--
-- Architecture:
--   Target:
--     Friendly: UNIT_IN_RANGE_UPDATE event → 1× UnitInRange (0 polling)
--     Enemy:    1 spell registered with EnableSpellRangeCheck
--               → SPELL_RANGE_CHECK_UPDATE fires only for THAT spell (1 event/change)
--     Dead:     1 res spell registered → same mechanism
--
--   Focus:
--     Friendly: UNIT_IN_RANGE_UPDATE event (0 polling)
--     Enemy:    Ticker 0.5s combat / 2.0s OOC → 1× IsSpellInRange
--
--   Boss 1-5:
--     Ticker (shared with enemy focus) → 1× IsSpellInRange per visible boss
--     Only active during encounters.
--
-- Old R41z0r engine cost: 512 EnableSpellRangeCheck registrations → 100-500
-- SPELL_RANGE_CHECK_UPDATE events/sec → EventBus dispatch per event
--
-- New cost: 1 EnableSpellRangeCheck registration → 1 event on actual change
--
-- Secret-safe: IsSpellInRange NOT secret (Unhalted). Only UnitInRange +
--              CheckInteractDistance need issecretvalue guards.
-- ============================================================================

_G.MSUF_RangeFadeMul = _G.MSUF_RangeFadeMul or {}
local _rfMul = _G.MSUF_RangeFadeMul

function _G.MSUF_GetRangeFadeMul(key, unit, frame)
    local v = _rfMul[key]
    if v ~= nil then return v end
    if unit then
        v = _rfMul[unit]
        if v ~= nil then return v end
    end
    return 1
end

-- ============================================================================
-- Shared: Spell selection + secret helpers
-- ============================================================================
do
    local C_Spell = _G.C_Spell
    local C_SpellBook = _G.C_SpellBook
    local IsSpellInSpellBook = (C_SpellBook and C_SpellBook.IsSpellInSpellBook) or nil
    local EnableSpellRangeCheck = (C_Spell and C_Spell.EnableSpellRangeCheck) or nil
    local IsSpellInRange = (C_Spell and C_Spell.IsSpellInRange) or nil
    local UnitExists = _G.UnitExists
    local UnitInRange = _G.UnitInRange
    local UnitCanAttack = _G.UnitCanAttack
    local UnitIsDeadOrGhost = _G.UnitIsDeadOrGhost
    local CheckInteractDistance = _G.CheckInteractDistance
    local C_Timer_After = _G.C_Timer and _G.C_Timer.After
    local issecretvalue = _G.issecretvalue

    local playerClass = select(2, _G.UnitClass("player"))

    local ENEMY_SPELLS = {
        DEATHKNIGHT={49576,47541}, DEMONHUNTER={185123,183752},
        DRUID={8921,5176}, EVOKER={362969}, HUNTER={75,466930},
        MAGE={116,133}, MONK={117952,115546}, PALADIN={20473,20271},
        PRIEST={585,8092}, ROGUE={185565,36554}, SHAMAN={188196,8042},
        WARLOCK={686,232670}, WARRIOR={355,100},
    }
    local RES_SPELLS = {
        DEATHKNIGHT={61999}, DRUID={50769,20484}, EVOKER={361227},
        MONK={115178}, PALADIN={7328,391054}, PRIEST={2006,212036},
        SHAMAN={2008}, WARLOCK={20707},
    }
    -- Friendly spells for non-party range check (IsSpellInRange fallback).
    -- 40yd heals/buffs that most specs have access to.
    local FRIENDLY_SPELLS = {
        DRUID={774,8936}, EVOKER={360823,361469}, HUNTER={34477},
        MAGE={475}, MONK={116670,115546}, PALADIN={19750,85673},
        PRIEST={17,2061}, ROGUE={57934}, SHAMAN={8004,188070},
        WARLOCK={20707}, WARRIOR={3411},
    }

    local _pEnemy, _pRes, _pFriendly = nil, nil, nil

    local function PickFirst(list)
        if not list or not IsSpellInSpellBook then return nil end
        for i = 1, #list do
            if list[i] and IsSpellInSpellBook(list[i], nil, true) then return list[i] end
        end
        return nil
    end

    local function RebuildPrimaries()
        _pEnemy    = PickFirst(ENEMY_SPELLS[playerClass])
        _pRes      = PickFirst(RES_SPELLS[playerClass])
        _pFriendly = PickFirst(FRIENDLY_SPELLS[playerClass])
    end

    -- ══════════════════════════════════════════════════════════════
    -- Shared: State cache + apply helpers
    -- ══════════════════════════════════════════════════════════════
    local _state = {}
    local _bossUnits = { "boss1", "boss2", "boss3", "boss4", "boss5" }
    local _mulT = _G.MSUF_RangeFadeMul
    local _fastApply
    local _applyAlpha

    -- Focus/Boss rangefade must remain feature-complete by default.
    -- The lite lifecycle is now explicit opt-in only via:
    --   MSUF_DB.general.perfLiteRangeFadeFB = true
    -- This avoids silent feature regression for focus/boss range checks.
    local function UseLiteFBRuntime()
        local db = _G.MSUF_DB
        local general = db and db.general
        return (general and general.perfLiteRangeFadeFB == true) and true or false
    end

    -- Frame resolver: one canonical lookup per unit token.
    -- Target lives at _G.MSUF_target. Focus/Boss live in MSUF_UnitFrames.
    local function GetFrame(unit)
        local frames = _G.MSUF_UnitFrames
        return (frames and frames[unit]) or _G["MSUF_" .. unit]
    end

    local function ApplyMul(f, unit, confKey, conf, inRange)
        local prev = _state[unit]
        if inRange == prev then return false end
        _state[unit] = inRange
        local a = 1
        if inRange == false then
            a = (conf and tonumber(conf.rangeFadeAlpha)) or 0.5
            if a < 0 then a = 0 elseif a > 1 then a = 1 end
        end
        _mulT[unit] = a
        if not f or (f.IsForbidden and f:IsForbidden()) then return true end
        if f.IsShown and not f:IsShown() then return true end
        if not _fastApply then _fastApply = _G.MSUF_ApplyRangeFadeAlphaFast end
        if type(_fastApply) == "function" and _fastApply(f, confKey, a) then
            return true
        end
        if not _applyAlpha then _applyAlpha = _G.MSUF_ApplyUnitAlpha end
        if type(_applyAlpha) == "function" then _applyAlpha(f, confKey) end
        return true
    end

    local function ClearMul(unit, confKey)
        local hadState = (_state[unit] ~= nil)
        local hadMul = (_mulT[unit] ~= nil and _mulT[unit] ~= 1)
        if not hadState and not hadMul then return false end
        _state[unit] = nil
        _mulT[unit] = 1
        local f = GetFrame(unit)
        if not f or (f.IsForbidden and f:IsForbidden()) then return true end
        if f.IsShown and not f:IsShown() then return true end
        if not _fastApply then _fastApply = _G.MSUF_ApplyRangeFadeAlphaFast end
        if type(_fastApply) == "function" and _fastApply(f, confKey, 1) then
            return true
        end
        if not _applyAlpha then _applyAlpha = _G.MSUF_ApplyUnitAlpha end
        if type(_applyAlpha) == "function" then _applyAlpha(f, confKey) end
        return true
    end

    -- ══════════════════════════════════════════════════════════════
    -- Shared: Inline range check (enemy/dead)
    -- IsSpellInRange: NOT secret (Unhalted). Direct boolean test.
    -- ══════════════════════════════════════════════════════════════
    local function CheckEnemy(unit)
        if not UnitExists(unit) then return nil end
        if UnitIsDeadOrGhost and UnitIsDeadOrGhost(unit) then
            if _pRes and IsSpellInRange then
                local r = IsSpellInRange(_pRes, unit)
                if r ~= nil then return r and true or false end
            end
            return nil
        end
        if _pEnemy and IsSpellInRange then
            local r = IsSpellInRange(_pEnemy, unit)
            if r ~= nil then return r and true or false end
        end
        -- CheckInteractDistance: works on any unit, may return secret in combat
        if CheckInteractDistance then
            local ci = CheckInteractDistance(unit, 4)
            if ci ~= nil then
                if issecretvalue and issecretvalue(ci) then return nil end
                return ci and true or false
            end
        end
        return nil
    end

    -- Friendly range via UnitInRange (secret-guarded)
    -- Fallback chain for non-party friendly targets:
    --   1. UnitInRange (party/raid only — checked=true means reliable)
    --   2. IsSpellInRange with a friendly spell (works on any friendly unit)
    --   3. CheckInteractDistance (28yd, OOC only, secret-guarded)
    --   4. nil → treated as in-range (safe default)
    local function CheckFriendly(unit)
        if not UnitExists(unit) then return nil end

        -- Try UnitInRange first (works for party/raid members)
        if UnitInRange then
            local inR, checked = UnitInRange(unit)
            if issecretvalue and (issecretvalue(checked) or issecretvalue(inR)) then
                return true  -- secret → treat as in-range
            end
            if checked then return inR and true or false end
        end

        -- Fallback: IsSpellInRange with a friendly spell (NOT secret per Unhalted)
        -- Works on friendly players, but returns nil on NPCs (can't cast heals on them)
        if _pFriendly and IsSpellInRange then
            local r = IsSpellInRange(_pFriendly, unit)
            if r ~= nil then return r and true or false end
        end

        -- Fallback: CheckInteractDistance (works on ANY unit including NPCs)
        -- In combat may return secret values → secret guard handles this
        -- Index 4 = 28 yards (Follow distance)
        if CheckInteractDistance then
            local ci = CheckInteractDistance(unit, 4)
            if ci ~= nil then
                if issecretvalue and issecretvalue(ci) then return true end
                return ci and true or false
            end
        end

        return nil  -- truly indeterminate → caller treats as in-range
    end

    -- ══════════════════════════════════════════════════════════════
    -- TARGET: Event-driven with 1 registered spell (replaces R41z0r)
    -- ══════════════════════════════════════════════════════════════
    local _targetRegisteredSpell = nil
    local _targetIsEnemy = false
    local _targetEvtFrame = nil
    local _targetDeadState = nil

    local function TargetGetConf()
        local db = _G.MSUF_DB
        local t = db and db.target
        if not t or t.rangeFadeEnabled ~= true then return nil end
        if _G.MSUF_UnitEditModeActive == true then return nil end
        return t
    end

    local function TargetUnregisterSpell()
        if _targetRegisteredSpell and EnableSpellRangeCheck then
            EnableSpellRangeCheck(_targetRegisteredSpell, false)
            _targetRegisteredSpell = nil
        end
    end

    local function TargetRegisterSpell(spellID)
        if not spellID or not EnableSpellRangeCheck then return end
        if _targetRegisteredSpell == spellID then return end
        TargetUnregisterSpell()
        _targetRegisteredSpell = spellID
        EnableSpellRangeCheck(spellID, true)
    end

    -- SPELL_RANGE_CHECK_UPDATE handler: fires ONLY for our 1 registered spell
    local function OnTargetSpellRange(event, spellIdentifier, isInRange, checksRange)
        local conf = TargetGetConf()
        if not conf then ClearMul("target", "target"); return end
        if not UnitExists("target") then ClearMul("target", "target"); return end
        -- isInRange is NOT secret (per Unhalted). Direct test.
        if checksRange then
            local result = (isInRange == true or isInRange == 1) and true or false
            ApplyMul(GetFrame("target"), "target", "target", conf, result)
        end
    end

    -- UNIT_IN_RANGE_UPDATE handler (friendly target)
    local function OnTargetFriendlyRange(_, event, arg1)
        if arg1 and arg1 ~= "target" then return end
        local conf = TargetGetConf()
        if not conf then ClearMul("target", "target"); return end
        ApplyMul(GetFrame("target"), "target", "target", conf, CheckFriendly("target"))
    end

    local function EnsureTargetEvtFrame()
        if _targetEvtFrame then return end
        _targetEvtFrame = CreateFrame("Frame")
    end

    local _targetFriendlyTicker = nil

    local function StopTargetFriendlyTicker()
        if _targetFriendlyTicker then
            _targetFriendlyTicker:Cancel()
            _targetFriendlyTicker = nil
        end
    end

    local function TargetClassifyAndWire()
        local conf = TargetGetConf()
        if not conf or not UnitExists("target") then
            _targetDeadState = nil
            TargetUnregisterSpell()
            StopTargetFriendlyTicker()
            ClearMul("target", "target")
            if _targetEvtFrame then
                _targetEvtFrame:UnregisterEvent("UNIT_IN_RANGE_UPDATE")
                _targetEvtFrame:SetScript("OnEvent", nil)
            end
            return
        end

        EnsureTargetEvtFrame()
        _targetIsEnemy = (UnitCanAttack and UnitCanAttack("player", "target")) and true or false
        _targetDeadState = (UnitIsDeadOrGhost and UnitIsDeadOrGhost("target")) and true or false

        if _targetIsEnemy then
            -- Enemy: register 1 spell for SPELL_RANGE_CHECK_UPDATE
            _targetEvtFrame:UnregisterEvent("UNIT_IN_RANGE_UPDATE")
            StopTargetFriendlyTicker()
            local spell = _pEnemy
            if _targetDeadState then spell = _pRes end
            if spell then
                TargetRegisterSpell(spell)
            else
                TargetUnregisterSpell()
            end
            -- Also do an immediate check
            ApplyMul(GetFrame("target"), "target", "target", conf, CheckEnemy("target"))
        else
            -- Friendly path
            TargetUnregisterSpell()

            -- Check if target is a party/raid member (UnitInRange works → event-driven)
            local isPartyMember = false
            if UnitInRange then
                local _, checked = UnitInRange("target")
                if not issecretvalue or not issecretvalue(checked) then
                    isPartyMember = (checked == true)
                end
            end

            if isPartyMember then
                -- Party member: UNIT_IN_RANGE_UPDATE fires reliably
                StopTargetFriendlyTicker()
                _targetEvtFrame:RegisterUnitEvent("UNIT_IN_RANGE_UPDATE", "target")
                _targetEvtFrame:SetScript("OnEvent", OnTargetFriendlyRange)
            else
                -- Non-party friendly (NPC, non-group player):
                -- UNIT_IN_RANGE_UPDATE won't fire. Use 1s ticker with
                -- IsSpellInRange / CheckInteractDistance fallback.
                _targetEvtFrame:UnregisterEvent("UNIT_IN_RANGE_UPDATE")
                _targetEvtFrame:SetScript("OnEvent", nil)
                StopTargetFriendlyTicker()
                if _G.C_Timer and _G.C_Timer.NewTicker then
                    _targetFriendlyTicker = _G.C_Timer.NewTicker(1.0, function()
                        local c = TargetGetConf()
                        if not c or not UnitExists("target") then
                            StopTargetFriendlyTicker()
                            ClearMul("target", "target")
                            return
                        end
                        ApplyMul(GetFrame("target"), "target", "target", c, CheckFriendly("target"))
                    end)
                end
            end

            -- Immediate check
            ApplyMul(GetFrame("target"), "target", "target", conf, CheckFriendly("target"))
        end
    end

    -- ══════════════════════════════════════════════════════════════
    -- Target: Global event wiring
    -- ══════════════════════════════════════════════════════════════
    local _targetWired = false

    local function WireTargetEvents()
        if _targetWired then return end; _targetWired = true
        local bus = _G.MSUF_EventBus_Register
        if type(bus) ~= "function" then return end

        -- 1 event for our 1 registered spell (was: 100-500 events for 512 spells)
        bus("SPELL_RANGE_CHECK_UPDATE", "MSUF_RANGEFADE", function(event, spellIdentifier, isInRange, checksRange)
            if _targetIsEnemy then
                OnTargetSpellRange(event, spellIdentifier, isInRange, checksRange)
            end
        end)

        bus("PLAYER_TARGET_CHANGED", "MSUF_RANGEFADE", function()
            _state["target"] = nil
            TargetClassifyAndWire()
        end)
        bus("PLAYER_ENTERING_WORLD", "MSUF_RANGEFADE", function()
            RebuildPrimaries()
            _state["target"] = nil
            TargetClassifyAndWire()
        end)
        bus("UNIT_FLAGS", "MSUF_RANGEFADE", function(_, unit)
            if unit ~= "target" then return end
            if not UnitExists("target") then
                if _targetDeadState ~= nil then
                    _targetDeadState = nil
                    _state["target"] = nil
                    TargetClassifyAndWire()
                end
                return
            end
            local isDead = (UnitIsDeadOrGhost and UnitIsDeadOrGhost("target")) and true or false
            if isDead ~= _targetDeadState then
                _targetDeadState = isDead
                _state["target"] = nil
                TargetClassifyAndWire()
            end
        end)
        bus("SPELLS_CHANGED", "MSUF_RANGEFADE", function()
            RebuildPrimaries()
            -- Re-register with potentially new primary spell and/or dead-state spell.
            if _targetIsEnemy and UnitExists("target") then
                local spell = _pEnemy
                if UnitIsDeadOrGhost and UnitIsDeadOrGhost("target") then spell = _pRes end
                if spell ~= _targetRegisteredSpell then
                    TargetRegisterSpell(spell)
                end
            end
        end)
        bus("PLAYER_TALENT_UPDATE", "MSUF_RANGEFADE", function()
            RebuildPrimaries()
            if _targetIsEnemy and UnitExists("target") then
                TargetClassifyAndWire()
            end
        end)
        bus("ACTIVE_PLAYER_SPECIALIZATION_CHANGED", "MSUF_RANGEFADE", function()
            RebuildPrimaries()
            if _targetIsEnemy and UnitExists("target") then
                TargetClassifyAndWire()
            end
        end)
        bus("TRAIT_CONFIG_UPDATED", "MSUF_RANGEFADE", function()
            RebuildPrimaries()
            if _targetIsEnemy and UnitExists("target") then
                TargetClassifyAndWire()
            end
        end)
    end

    local function UnwireTargetEvents()
        if not _targetWired then return end; _targetWired = false
        local unreg = _G.MSUF_EventBus_Unregister
        if type(unreg) ~= "function" then return end
        unreg("SPELL_RANGE_CHECK_UPDATE", "MSUF_RANGEFADE")
        unreg("PLAYER_TARGET_CHANGED", "MSUF_RANGEFADE")
        unreg("PLAYER_ENTERING_WORLD", "MSUF_RANGEFADE")
        unreg("UNIT_FLAGS", "MSUF_RANGEFADE")
        unreg("SPELLS_CHANGED", "MSUF_RANGEFADE")
        unreg("PLAYER_TALENT_UPDATE", "MSUF_RANGEFADE")
        unreg("ACTIVE_PLAYER_SPECIALIZATION_CHANGED", "MSUF_RANGEFADE")
        unreg("TRAIT_CONFIG_UPDATED", "MSUF_RANGEFADE")
    end

    -- Public target API (signatures preserved)
    function _G.MSUF_RangeFade_Register(getConfigFn, applyAlphaFn, opts)
        -- Legacy compat: getConfigFn/applyAlphaFn are no longer used.
        -- Target now reads DB directly + uses ApplyMul.
    end

    function _G.MSUF_RangeFade_RebuildSpells()
        RebuildPrimaries()
        TargetClassifyAndWire()
    end

    function _G.MSUF_RangeFade_OnEvent_SpellRangeUpdate(spellIdentifier, isInRange, checksRange)
        -- Handled internally via EventBus now
    end

    function _G.MSUF_RangeFade_ApplyCurrent(force)
        local conf = TargetGetConf()
        if conf and UnitExists("target") then
            if _targetIsEnemy then
                ApplyMul(GetFrame("target"), "target", "target", conf, CheckEnemy("target"))
            else
                ApplyMul(GetFrame("target"), "target", "target", conf, CheckFriendly("target"))
            end
        end
    end

    function _G.MSUF_RangeFade_Reset()
        _state["target"] = nil
        _mulT.target = 1
        StopTargetFriendlyTicker()
        -- Re-apply on next target event
    end

    function _G.MSUF_RangeFade_Shutdown()
        TargetUnregisterSpell()
        StopTargetFriendlyTicker()
        UnwireTargetEvents()
        ClearMul("target", "target")
        if _targetEvtFrame then
            _targetEvtFrame:UnregisterEvent("UNIT_IN_RANGE_UPDATE")
            _targetEvtFrame:SetScript("OnEvent", nil)
        end
    end

    function _G.MSUF_RangeFade_EvaluateActive(force)
        local db = _G.MSUF_DB
        local t = db and db.target
        local want = (t and t.rangeFadeEnabled == true)
        if _G.MSUF_UnitEditModeActive == true then want = false end
        if want then
            RebuildPrimaries()
            WireTargetEvents()
            TargetClassifyAndWire()
        else
            TargetUnregisterSpell()
            StopTargetFriendlyTicker()
            UnwireTargetEvents()
            ClearMul("target", "target")
        end
    end

    -- Backwards compat
    function _G.MSUF_RangeFade_Rebuild()
        _G.MSUF_RangeFade_RebuildSpells()
    end

    -- ══════════════════════════════════════════════════════════════
    -- ══════════════════════════════════════════════════════════════
    -- FOCUS/BOSS: Smart-sleep ticker + event-driven friendly focus
    --
    -- Ticker lifecycle (SyncTicker):
    --   RUNNING when: enemy focus OR boss range enabled → 0.50s combat / 2.0s OOC
    --   SLEEPING when: only friendly focus (event-driven) → 0 CPU
    --   STOPPED when: no focus + no boss enabled → 0 CPU
    --
    -- Friendly focus: UNIT_IN_RANGE_UPDATE (oUF approach, 0 polling always)
    -- Unit swaps: immediate check via events, then SyncTicker re-evaluates
    -- Burst mode: 0.20s for a short window after focus/boss state changes
    -- ══════════════════════════════════════════════════════════════
    local _focusIsEnemy = false
    local _focusEvtFrame = nil
    local _ticker = nil
    local _tickRate = 0
    local _playerMoving = false
    local _TICK_COMBAT = 0.50
    local _TICK_OOC = 2.0
    local _TICK_COMBAT_FOCUS = 0.14
    local _TICK_COMBAT_BOSS = 0.12
    local _TICK_MOVING_FOCUS = 0.10
    local _TICK_MOVING_BOSS = 0.08
    local _TICK_OOC_FOCUS = 0.35
    local _TICK_OOC_BOSS = 0.22
    local _TICK_BURST = 0.05
    local _BURST_DURATION = 0.75
    local _burstSerial = 0
    local C_Timer_NewTicker = _G.C_Timer and _G.C_Timer.NewTicker
    local HasActiveEnemyFocusRangeUnit, HasActiveBossRangeUnit, NeedsPoll, RequestBurst
    local _pollUnits, _pollConfKey, _pollCount = {}, {}, 0

    local function OnFocusFriendlyRange(_, event, arg1)
        if arg1 and arg1 ~= "focus" then return end
        local db = _G.MSUF_DB
        local conf = db and db.focus
        if not conf or conf.rangeFadeEnabled ~= true then ClearMul("focus", "focus"); return end
        if _G.MSUF_UnitEditModeActive == true then ClearMul("focus", "focus"); return end
        ApplyMul(GetFrame("focus"), "focus", "focus", conf, CheckFriendly("focus"))
    end

    local function EnsureFocusEvtFrame()
        if _focusEvtFrame then return end
        _focusEvtFrame = CreateFrame("Frame")
        _focusEvtFrame:SetScript("OnEvent", OnFocusFriendlyRange)
    end

    local function StopTicker()
        if _ticker then _ticker:Cancel(); _ticker = nil end
        _tickRate = 0
        _burstSerial = _burstSerial + 1
    end

    local function RebuildPollList()
        _pollCount = 0
        if _G.MSUF_UnitEditModeActive == true then return end

        local db = _G.MSUF_DB
        local focusConf = db and db.focus
        if _focusIsEnemy and focusConf and focusConf.rangeFadeEnabled == true then
            local f = GetFrame("focus")
            if UnitExists and UnitExists("focus") and (not f or not f.IsShown or f:IsShown()) then
                _pollCount = _pollCount + 1
                _pollUnits[_pollCount] = "focus"
                _pollConfKey[_pollCount] = "focus"
            end
        end

        local bossConf = db and db.boss
        if bossConf and bossConf.rangeFadeEnabled == true then
            local frames = _G.MSUF_UnitFrames
            for i = 1, 5 do
                local unit = _bossUnits[i]
                local f = frames and frames[unit]
                if f and f.IsShown and f:IsShown() and UnitExists(unit) then
                    _pollCount = _pollCount + 1
                    _pollUnits[_pollCount] = unit
                    _pollConfKey[_pollCount] = "boss"
                end
            end
        end
    end

    local function CheckEnemyUnits()
        if _pollCount <= 0 then
            RebuildPollList()
            if _pollCount <= 0 then
                StopTicker()
                return
            end
        end

        local db = _G.MSUF_DB
        local focusConf = db and db.focus
        local bossConf = db and db.boss
        local changedAny = false

        for i = 1, _pollCount do
            local unit = _pollUnits[i]
            local confKey = _pollConfKey[i]
            local conf = (confKey == "focus") and focusConf or bossConf
            local f = GetFrame(unit)
            if conf and f and (not f.IsShown or f:IsShown()) and UnitExists(unit) then
                if ApplyMul(f, unit, confKey, conf, CheckEnemy(unit)) then
                    changedAny = true
                end
            else
                if ClearMul(unit, confKey) then
                    changedAny = true
                end
            end
        end

        if changedAny and _tickRate > _TICK_BURST and C_Timer_After then
            C_Timer_After(0, function()
                if NeedsPoll() then
                    RequestBurst(0.25)
                end
            end)
        end
    end

    function HasActiveEnemyFocusRangeUnit()
        if _G.MSUF_UnitEditModeActive == true then return false end
        local db = _G.MSUF_DB
        local conf = db and db.focus
        if not conf or conf.rangeFadeEnabled ~= true then return false end
        if not _focusIsEnemy then return false end
        if not UnitExists or not UnitExists("focus") then return false end
        local f = GetFrame("focus")
        if f and f.IsShown and not f:IsShown() then return false end
        return true
    end

    local function DesiredRate()
        local hasBoss = HasActiveBossRangeUnit()
        local hasEnemyFocus = HasActiveEnemyFocusRangeUnit()
        local inCombat = (_G.MSUF_InCombat == true)

        if _playerMoving then
            if hasBoss then return _TICK_MOVING_BOSS end
            if hasEnemyFocus then return _TICK_MOVING_FOCUS end
        end

        if inCombat then
            if hasBoss then return _TICK_COMBAT_BOSS end
            if hasEnemyFocus then return _TICK_COMBAT_FOCUS end
            return _TICK_COMBAT
        end

        if hasBoss then return _TICK_OOC_BOSS end
        if hasEnemyFocus then return _TICK_OOC_FOCUS end
        return _TICK_OOC
    end

    local function EnsureTicker(rate)
        if not C_Timer_NewTicker then return end
        if _ticker and _tickRate == rate then return end
        StopTicker()
        _tickRate = rate
        _ticker = C_Timer_NewTicker(rate, CheckEnemyUnits)
    end

    function HasActiveBossRangeUnit()
        local frames = _G.MSUF_UnitFrames
        for i = 1, 5 do
            local unit = _bossUnits[i]
            local f = frames and frames[unit]
            if f and f.IsShown and f:IsShown() and UnitExists(unit) then
                return true
            end
        end
        return false
    end

    -- Smart-sleep: only run ticker when enemy units need polling.
    -- Friendly focus = event-driven → no ticker needed.
    function NeedsPoll()
        if _G.MSUF_UnitEditModeActive == true then return false end
        if _pollCount > 0 then return true end
        if HasActiveEnemyFocusRangeUnit() then return true end
        local db = _G.MSUF_DB
        local bossConf = db and db.boss
        if bossConf and bossConf.rangeFadeEnabled == true and HasActiveBossRangeUnit() then return true end
        return false
    end

    local function SyncTicker()
        RebuildPollList()
        if _pollCount > 0 then
            EnsureTicker(DesiredRate())
        else
            StopTicker()
        end
    end

    function RequestBurst(duration)
        if _G.MSUF_UnitEditModeActive == true then return end
        if not NeedsPoll() then return end
        duration = tonumber(duration) or _BURST_DURATION
        if duration < 0.20 then duration = 0.20 end
        EnsureTicker(_TICK_BURST)
        if not C_Timer_After then return end
        _burstSerial = _burstSerial + 1
        local serial = _burstSerial
        C_Timer_After(duration, function()
            if serial ~= _burstSerial then return end
            SyncTicker()
        end)
    end

    local function IsTrackedFBUnit(unit)
        local db = _G.MSUF_DB
        local focusOn = db and db.focus and db.focus.rangeFadeEnabled == true and not UseLiteFBRuntime()
        local bossOn  = db and db.boss  and db.boss.rangeFadeEnabled  == true and not UseLiteFBRuntime()
        if unit == "focus" then return focusOn and true or false end
        if unit == "boss1" or unit == "boss2" or unit == "boss3" or unit == "boss4" or unit == "boss5" then
            return bossOn and true or false
        end
        return false
    end

    local function RangeFadeFBWanted()
        if UseLiteFBRuntime() then return false end
        local db = _G.MSUF_DB
        if db and db.focus and db.focus.rangeFadeEnabled == true then return true end
        if db and db.boss  and db.boss.rangeFadeEnabled  == true then return true end
        return false
    end

    local function ClassifyFocus()
        if not UnitExists or not UnitExists("focus") then _focusIsEnemy = false; return end
        _focusIsEnemy = (UnitCanAttack and UnitCanAttack("player", "focus")) and true or false
    end

    local _fbEvtFrame = nil
    local _fbEvents = {}
    local function EnsureFBEventFrame()
        if _fbEvtFrame then return _fbEvtFrame end
        local ef = CreateFrame("Frame")
        ef:SetScript("OnEvent", function(_, event, arg1)
            if event == "PLAYER_REGEN_DISABLED" then
                if not NeedsPoll() and not _ticker then return end
                SyncTicker()
                if NeedsPoll() or _ticker then
                    CheckEnemyUnits()
                end
            elseif event == "PLAYER_REGEN_ENABLED" then
                if not NeedsPoll() and not _ticker then return end
                SyncTicker()
                if NeedsPoll() or _ticker then
                    CheckEnemyUnits()
                end
            elseif event == "PLAYER_STARTED_MOVING" then
                if not NeedsPoll() and not _ticker then return end
                _playerMoving = true
                SyncTicker()
                if NeedsPoll() then
                    RequestBurst(0.60)
                    CheckEnemyUnits()
                end
            elseif event == "PLAYER_STOPPED_MOVING" then
                if not NeedsPoll() and not _ticker then return end
                _playerMoving = false
                SyncTicker()
                if NeedsPoll() or _ticker then
                    CheckEnemyUnits()
                end
            elseif event == "PLAYER_FOCUS_CHANGED" then
                _state["focus"] = nil
                ClassifyFocus()
                if UnitExists("focus") and not _focusIsEnemy then
                    EnsureFocusEvtFrame()
                    _focusEvtFrame:RegisterUnitEvent("UNIT_IN_RANGE_UPDATE", "focus")
                    OnFocusFriendlyRange(nil, event, "focus")
                else
                    if _focusEvtFrame then _focusEvtFrame:UnregisterEvent("UNIT_IN_RANGE_UPDATE") end
                    if not UnitExists("focus") then
                        ClearMul("focus", "focus")
                    end
                end
                SyncTicker()
                if NeedsPoll() then
                    RequestBurst(_BURST_DURATION)
                    CheckEnemyUnits()
                end
            elseif event == "INSTANCE_ENCOUNTER_ENGAGE_UNIT" then
                for i = 1, 5 do _state[_bossUnits[i]] = nil end
                SyncTicker()
                if NeedsPoll() then
                    RequestBurst(_BURST_DURATION)
                    CheckEnemyUnits()
                end
            elseif event == "UNIT_FLAGS" or event == "UNIT_CONNECTION"
                or event == "UNIT_PHASE" or event == "UNIT_TARGETABLE_CHANGED"
                or event == "UNIT_FACTION" then
                local unit = arg1
                if not IsTrackedFBUnit(unit) then return end
                _state[unit] = nil
                if unit == "focus" then
                    ClassifyFocus()
                    if UnitExists("focus") and not _focusIsEnemy then
                        EnsureFocusEvtFrame()
                        _focusEvtFrame:RegisterUnitEvent("UNIT_IN_RANGE_UPDATE", "focus")
                        OnFocusFriendlyRange(nil, event, "focus")
                        SyncTicker()
                        return
                    else
                        if _focusEvtFrame then _focusEvtFrame:UnregisterEvent("UNIT_IN_RANGE_UPDATE") end
                        if not UnitExists("focus") then
                            ClearMul("focus", "focus")
                        end
                    end
                end
                SyncTicker()
                if NeedsPoll() then
                    RequestBurst(0.80)
                    CheckEnemyUnits()
                elseif unit ~= "focus" then
                    ClearMul(unit, "boss")
                end
            elseif event == "SPELLS_CHANGED" or event == "PLAYER_ENTERING_WORLD"
                or event == "ACTIVE_PLAYER_SPECIALIZATION_CHANGED"
                or event == "PLAYER_TALENT_UPDATE" or event == "TRAIT_CONFIG_UPDATED" then
                if event == "PLAYER_ENTERING_WORLD" then
                    _playerMoving = false
                end
                RebuildPrimaries()
                for k in pairs(_state) do _state[k] = nil end
                SyncTicker()
                if NeedsPoll() or _ticker then
                    if NeedsPoll() then
                        RequestBurst(0.80)
                    end
                    CheckEnemyUnits()
                end
            end
        end)
        _fbEvtFrame = ef
        return ef
    end

    local function SetFBEvent(event, want)
        local ef = EnsureFBEventFrame()
        if want then
            if not _fbEvents[event] then
                ef:RegisterEvent(event)
                _fbEvents[event] = true
            end
        elseif _fbEvents[event] then
            ef:UnregisterEvent(event)
            _fbEvents[event] = nil
        end
    end

    local function RefreshFBEventLifecycle()
        local db = _G.MSUF_DB
        local focusOn = db and db.focus and db.focus.rangeFadeEnabled == true and not UseLiteFBRuntime()
        local bossOn  = db and db.boss  and db.boss.rangeFadeEnabled  == true and not UseLiteFBRuntime()

        if not focusOn and not bossOn then
            if _fbEvtFrame then
                _fbEvtFrame:UnregisterAllEvents()
            end
            for k in pairs(_fbEvents) do _fbEvents[k] = nil end
            return false, false
        end

        -- shared polling/reactivity events only when at least one FB feature is on
        SetFBEvent("PLAYER_REGEN_DISABLED", true)
        SetFBEvent("PLAYER_REGEN_ENABLED", true)
        SetFBEvent("PLAYER_STARTED_MOVING", true)
        SetFBEvent("PLAYER_STOPPED_MOVING", true)
        SetFBEvent("SPELLS_CHANGED", true)
        SetFBEvent("ACTIVE_PLAYER_SPECIALIZATION_CHANGED", true)
        SetFBEvent("PLAYER_TALENT_UPDATE", true)
        SetFBEvent("TRAIT_CONFIG_UPDATED", true)
        SetFBEvent("PLAYER_ENTERING_WORLD", true)
        SetFBEvent("UNIT_FLAGS", true)
        SetFBEvent("UNIT_CONNECTION", true)
        SetFBEvent("UNIT_PHASE", true)
        SetFBEvent("UNIT_TARGETABLE_CHANGED", true)
        SetFBEvent("UNIT_FACTION", true)

        -- focus-only lifecycle
        SetFBEvent("PLAYER_FOCUS_CHANGED", focusOn)

        -- boss-only lifecycle
        SetFBEvent("INSTANCE_ENCOUNTER_ENGAGE_UNIT", bossOn)

        return focusOn, bossOn
    end

    function _G.MSUF_RangeFadeFB_RebuildSpells()
        if RangeFadeFBWanted() ~= true then return end
        RebuildPrimaries()
    end

    function _G.MSUF_RangeFadeFB_Reset()
        for k in pairs(_state) do _state[k] = nil end
        _pollCount = 0
        _mulT.focus = 1
        for i = 1, 5 do _mulT[_bossUnits[i]] = 1 end
    end

    function _G.MSUF_RangeFadeFB_EvaluateActive(force)
        local focusOn, bossOn = RefreshFBEventLifecycle()
        if focusOn or bossOn then
            if force == true then for k in pairs(_state) do _state[k] = nil end end
            RebuildPrimaries()
            if focusOn then
                ClassifyFocus()
                -- Friendly focus: event-driven
                if UnitExists and UnitExists("focus") and not _focusIsEnemy then
                    EnsureFocusEvtFrame()
                    _focusEvtFrame:RegisterUnitEvent("UNIT_IN_RANGE_UPDATE", "focus")
                    OnFocusFriendlyRange(nil, "INIT", "focus")
                else
                    if _focusEvtFrame then _focusEvtFrame:UnregisterEvent("UNIT_IN_RANGE_UPDATE") end
                end
            else
                _focusIsEnemy = false
                if _focusEvtFrame then _focusEvtFrame:UnregisterEvent("UNIT_IN_RANGE_UPDATE") end
                ClearMul("focus", "focus")
            end
            if not bossOn then
                for i = 1, 5 do ClearMul(_bossUnits[i], "boss") end
            end
            -- Ticker: only when enemy units need polling (smart-sleep)
            SyncTicker()
            CheckEnemyUnits()
            return
        end
        -- Fully shut down focus/boss rangefade lifecycle when both features are off.
        _playerMoving = false
        StopTicker()
        _focusIsEnemy = false
        if _focusEvtFrame then _focusEvtFrame:UnregisterEvent("UNIT_IN_RANGE_UPDATE") end
        ClearMul("focus", "focus")
        for i = 1, 5 do ClearMul(_bossUnits[i], "boss") end
    end

    function _G.MSUF_RangeFadeFB_ApplyCurrent(force)
        _G.MSUF_RangeFadeFB_EvaluateActive(force)
    end

    -- ══════════════════════════════════════════════════════════════
    -- InitPostLogin: called once after unitframes exist
    -- ══════════════════════════════════════════════════════════════
    function _G.MSUF_RangeFade_InitPostLogin()
        RebuildPrimaries()

        -- Target: evaluate via EvaluateActive (wires events + registers 1 spell)
        if C_Timer_After then
            C_Timer_After(0, function()
                if _G.MSUF_RangeFade_EvaluateActive then
                    _G.MSUF_RangeFade_EvaluateActive(true)
                end
            end)
        elseif _G.MSUF_RangeFade_EvaluateActive then
            _G.MSUF_RangeFade_EvaluateActive(true)
        end

        -- Focus/Boss: evaluate active
        _G.MSUF_RangeFadeFB_EvaluateActive(true)
    end
end
