影刺：化影绕后，背刺一刀双倍

 fx-shadowstab

-- @file ShadowStab.lua
-- 影刺 —— 化影绕后，从背刺出的一刀双倍

local ShadowStab = {}

local CONST = {
    BEHIND_BAND   = 70,
    CRIT_AMP      = 2.0,
    BASE_DMG      = 12,
    STEP_LIFE     = 0.3,
    STEP_CD       = 4.0,
    STEP_OFFSET   = 54,

    COLOR_STAB    = "#8a7ab8",
    COLOR_DEEP    = "#2a1a4a",
    COLOR_GHOST   = "#e0d8f0",

    ZORDER_STEP   = 133,
    ZORDER_FX     = 135,
    AUTOINC_BASE  = 980000,
}

local _stepT      = 0
local _stepFrom   = 0
local _stepTo     = 0
local _cdLeft     = 0
local _scheduler  = nil
local _autoInc    = 0

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

local function CreateBehindRing(x)
    local node = GUI:Layout_Create(GUI:Attach_SceneF(),
        GenID("Ring"), x, 6, 0, 0, false)
    GUI:setLocalZOrder(node, CONST.ZORDER_STEP)
    for i = 1, 22 do
        local a1 = (i - 1) / 22 * 6.28
        local a2 = i / 22 * 6.28
        GUI:DrawLine_Create(node, string.format("r_%d", i), 0, 0, 2.5,
            m_cos(a1) * 34, m_sin(a1) * 12,
            m_cos(a2) * 34, m_sin(a2) * 12,
            CONST.COLOR_STAB, 210)
    end
    return node
end

function ShadowStab.Step()
    if _cdLeft > 0 or _stepT > 0 then return end
    local tp = GetActorPos(SL:GetValue("MARK_TARGET_ID"))
    local mp = GetActorPos(SL:GetValue("USER_ID"))
    if not tp or not mp then return end
    _cdLeft = CONST.STEP_CD
    _stepT = CONST.STEP_LIFE
    _stepFrom = mp.x
    _stepTo = tp.x + (mp.x > tp.x and CONST.STEP_OFFSET
        or -CONST.STEP_OFFSET)
end

-- 朝向判定
local function IsBehind(myX, foeX, foeDir)
    if foeDir == 2 and myX < foeX - 10 then return true end
    if foeDir == 6 and myX > foeX + 10 then return true end
    return false
end

-- 定时器
if not _scheduler then
    _scheduler = SL:Schedule(function(dt)
        _cdLeft = math.max(0, _cdLeft - dt)
        if _stepT > 0 then
            _stepT = _stepT - dt
            local k = 1 - math.max(0, _stepT) / CONST.STEP_LIFE
            local mp = GetActorPos(SL:GetValue("USER_ID"))
            if mp then
                SL:FlyActorTo(_stepFrom + (_stepTo - _stepFrom) * k)
                SL:DropGhost()
            end
            if _stepT <= 0 then _stepT = 0 end
            return
        end
        _atkT = (_atkT or 1.0) - dt
        if _atkT <= 0 then
            _atkT = behind and 0.9 or 1.3
            local myID = SL:GetValue("USER_ID")
            local mp = GetActorPos(myID)
            local tid = SL:GetValue("MARK_TARGET_ID")
            local tp = tid and GetActorPos(tid)
            if mp and tp and IsBehind(mp.x, tp.x,
                SL:GetValue("ACTOR_DIR", tid)) then
                local vd = CONST.BASE_DMG * CONST.CRIT_AMP
                SL:ActorHurt(tid, vd)
                SL:TipAbove(tid, "-" .. vd)
                SL:ScreenShake(3, 0.16)
            else
                SL:ActorHurt(tid, CONST.BASE_DMG)
            end
        end
    end, 0.02)
end

return ShadowStab