重力井：重力井吸怪加减速

 fx-gravitywell

-- @file GravityWell.lua
-- 重力井 —— 重力井吸怪往中心拉，站进去走不动

local GravityWell = {}

local CONST = {
    WELL_LIFE     = 4.0,
    WELL_CD       = 5.0,
    WELL_RADIUS   = 100,
    PULL_FORCE    = 200,

    COLOR_WELL    = "#6868b8",
    COLOR_DEEP    = "#1a1a52",
    COLOR_GHOST   = "#c8c8f4",

    ZORDER_WELL   = 130,
    ZORDER_FX     = 135,
    AUTOINC_BASE  = 1070000,
}

local _wellT     = 0
local _wellX     = 0
local _wellY     = 0
local _cdLeft    = 0
local _wellFx    = nil
local _scheduler = nil
local _autoInc   = 0

local function GenID(prefix)
    _autoInc = _autoInc + 1
    return string.format("%s_%d", prefix or "GPW",
        CONST.AUTOINC_BASE + _autoInc)
end

local function GetActorPos(id)
    if not id then return nil end
    local x = SL:GetValue("ACTOR_POSITION_X", id)
    local y = SL:GetValue("ACTOR_POSITION_Y", id)
    if not x or not y then return nil end
    return { x = x, y = y }
end

local function SafeRemove(node)
    if node and not GUI:Widget_IsNull(node) then
        GUI:removeFromParent(node)
    end
end

local function ShowTip(msg)
    if msg and msg ~= "" then SL:ShowSystemTips(msg) end
end

function GravityWell.Cast()
    if _cdLeft > 0 or _wellT > 0 then return end
    local tid = SL:GetValue("MARK_TARGET_ID")
    local tp = GetActorPos(tid)
    if not tid or not tp then return end
    _cdLeft = CONST.WELL_CD
    _wellT = CONST.WELL_LIFE
    _wellX = tp.x
    _wellY = tp.y
    SafeRemove(_wellFx)
    _wellFx = GUI:Layout_Create(GUI:Attach_SceneF(),
        GenID("Well"), _wellX, _wellY, 0, 0, false)
    GUI:setLocalZOrder(_wellFx, CONST.ZORDER_WELL)
    SL:PlayWellStartFx(_wellX, _wellY)
    ShowTip("重力井开了——四秒吸怪往中心拉")
end

-- 定时器：吸拉推进与井环演出
if not _scheduler then
    _scheduler = SL:Schedule(function(dt)
        _cdLeft = math.max(0, _cdLeft - dt)
        if _wellT > 0 then
            _wellT = _wellT - dt
            local tid = SL:GetValue("MARK_TARGET_ID")
            local tp = tid and GetActorPos(tid)
            if not tp then
                _wellT = 0
                SafeRemove(_wellFx)
                return
            end
            local dx = _wellX - tp.x
            local dy = _wellY - tp.y
            local dist = math.sqrt(dx * dx + dy * dy)
            if dist > 3 then
                SL:SetActorPos(tid,
                    tp.x + dx * 2 * dt,
                    tp.y + dy * 2 * dt)
            end
            if _wellT <= 0 then
                SafeRemove(_wellFx)
                ShowTip("井散了——它自由了")
            end
        end
    end, 0.02)
end

SL:ScheduleOnce(function()
    SL:BindDebugButton("引力井", function()
        GravityWell.Cast()
    end)
    ShowTip("技能已加载: 重力井 (调试按钮触发)")
end, 1.0)

function GravityWell.Unload()
    if _scheduler then SL:Unschedule(_scheduler) end
    SafeRemove(_wellFx)
    _wellT = 0
end

return GravityWell