local Players = game:GetService("Players")
local RunService = game:GetService("RunService")
local Workspace = game:GetService("Workspace")
local lp = Players.LocalPlayer

local cfg = {
	active = true,
	visual = true,
	compFactor = 0.7,
	jitterW = 0.6,
	maxCompMs = 350,
	maxOfs = 18,
	smooth = 7,
	blendUp = 2.5,
	blendDn = 4.0,
	dirUp = 2.0,
	dirDn = 3.5,
	velMin = 1.5,
	velAlpha = 17.0,
	tpDist = 50,
	rttA = 0.08,
	jitA = 0.06,
	yDamp = 0.1,
	spdClamp = 1.15,
	boundsCheck = true,
	maxOfsRate = 0.8,
	pingFadeLo = 0.03,
	pingFadeHi = 0.07,
	minDt = 1 / 300,
	maxDt = 1 / 15,
	owThresh = 0.05,
	accelAlpha = 3.5,
	accelScale = 0.3,
	staleRate = 1.5,
	staleFade = 0.6,
	groundUp = 10,
	groundDown = 80,
	adaptSmoothMin = 3,
	adaptSmoothMax = 12,
	adaptJitScale = 120,
}

local net = { rtt = 0, jit = 0.01 }
local ents = {}
local conns = {}
local running = false
local rcP = RaycastParams.new()
rcP.FilterType = Enum.RaycastFilterType.Exclude
local filterTable = {}

local function expAlpha(rate, dt)
	return 1 - math.exp(-rate * dt)
end

local function pingFade(rtt)
	local hi = math.max(cfg.pingFadeHi, net.jit * 2.5)
	if rtt <= cfg.pingFadeLo then return 0 end
	if rtt >= hi then return 1 end
	return (rtt - cfg.pingFadeLo) / (hi - cfg.pingFadeLo)
end

local function compT()
	local raw = net.rtt * 0.5 * cfg.compFactor + net.jit * cfg.jitterW
	local v = math.min(raw * pingFade(net.rtt), cfg.maxCompMs / 1000)
	if v ~= v or v < 0 then return 0 end
	return v
end

local function updateNet()
	local r = lp:GetNetworkPing() * 2
	if r ~= r or r < 0 then r = 0 end
	net.rtt = net.rtt == 0 and r or net.rtt + cfg.rttA * (r - net.rtt)
	net.jit = net.jit + cfg.jitA * (math.abs(r - net.rtt) - net.jit)
end

local function newE()
	return {
		engPos = nil,
		readCF = CFrame.identity,
		lastPP = nil,
		vel = Vector3.zero,
		sVel = Vector3.zero,
		dir = Vector3.zero,
		dcon = 0,
		bld = 0,
		ofs = Vector3.zero,
		pred = CFrame.identity,
		char = nil,
		root = nil,
		hum = nil,
		alive = false,
		ok = false,
		accel = Vector3.zero,
		prevVel = nil,
		airborne = false,
		stale = 0,
		conf = 0,
	}
end

local function rstE(e)
	e.vel = Vector3.zero
	e.sVel = Vector3.zero
	e.dir = Vector3.zero
	e.dcon = 0
	e.bld = 0
	e.ofs = Vector3.zero
	e.ok = false
	e.engPos = nil
	e.lastPP = nil
	e.accel = Vector3.zero
	e.prevVel = nil
	e.airborne = false
	e.stale = 0
	e.conf = 0
end

local function getWS(e)
	return (e.hum and e.hum.WalkSpeed) or 16
end

local function validatePos(origin, target)
	if not cfg.boundsCheck then return target end
	local disp = target - origin
	local dist = disp.Magnitude
	if dist < 0.1 then return target end
	local wh = Workspace:Raycast(origin, disp, rcP)
	if wh then return origin + disp.Unit * math.max(wh.Distance - 0.5, 0) end
	local gh = Workspace:Raycast(target + Vector3.new(0, cfg.groundUp, 0), Vector3.new(0, -(cfg.groundUp + cfg.groundDown), 0), rcP)
	if not gh then return origin end
	return target
end
local function updE(e, dt)
	local root = e.root
	local cf = root.CFrame
	local p = cf.Position
	local rv = root.AssemblyLinearVelocity
	local rvm = rv.Magnitude
	if rvm ~= rvm or rvm > 5000 then rv = Vector3.zero end

	e.readCF = cf

	local freshData = false
	local engP
	if cfg.visual and e.lastPP and e.engPos then
		if (p - e.lastPP).Magnitude > cfg.owThresh then
			engP = p
			freshData = true
		else
			engP = e.engPos + rv * dt
		end
	else
		engP = p
		freshData = true
	end

	if e.engPos and (engP - e.engPos).Magnitude > cfg.tpDist then
		rstE(e)
		engP = p
		freshData = true
	end

	e.engPos = engP

	local va = expAlpha(cfg.velAlpha, dt)
	e.sVel = e.sVel:Lerp(rv, va)

	local ws = getWS(e)
	local maxSpd = ws * cfg.spdClamp
	local hRaw = Vector3.new(e.sVel.X, 0, e.sVel.Z)
	local hMag = hRaw.Magnitude

	if hMag > maxSpd then
		local s = maxSpd / hMag
		e.vel = Vector3.new(e.sVel.X * s, e.sVel.Y, e.sVel.Z * s)
	else
		e.vel = e.sVel
	end

	if e.prevVel then
		local rawAccel = (e.vel - e.prevVel) / dt
		local ram = rawAccel.Magnitude
		if ram ~= ram or ram > 5000 then rawAccel = Vector3.zero end
		e.accel = e.accel:Lerp(rawAccel, expAlpha(cfg.accelAlpha, dt))
	end
	e.prevVel = e.vel

	e.airborne = e.hum and e.hum.FloorMaterial == Enum.Material.Air

	local hv = Vector3.new(e.vel.X, 0, e.vel.Z)
	local hspd = hv.Magnitude

	if hspd > cfg.velMin then
		local nv = hv.Unit
		if e.dir.Magnitude < 0.1 then
			e.dir = nv
			e.dcon = 0.2
		else
			local dot = math.clamp(nv:Dot(e.dir), 0, 1)
			e.dcon = e.dcon + cfg.dirUp * dt * (dot - e.dcon)
			local nd = e.dir:Lerp(nv, math.clamp(5 * dt, 0, 1))
			e.dir = nd.Magnitude > 0.001 and nd.Unit or nv
		end
		e.bld = math.min(e.bld + cfg.blendUp * dt, 1)
	else
		e.dcon = math.max(e.dcon - cfg.dirDn * dt, 0)
		e.bld = math.max(e.bld - cfg.blendDn * dt, 0)
		if e.bld < 0.01 then e.dir = Vector3.zero end
	end

	if freshData then
		e.stale = 0
	else
		e.stale = e.stale + dt * cfg.staleRate
	end
	local staleMul = math.max(1 - e.stale * cfg.staleFade, 0)

	local sc = e.bld * e.dcon * staleMul
	local ct = compT()
	local adaptSmooth = math.clamp(cfg.smooth - net.jit * cfg.adaptJitScale, cfg.adaptSmoothMin, cfg.adaptSmoothMax)
	local tgt
	if sc > 0.01 then
		local t = ct * sc
		local pv
		if e.airborne then
			local grav = Workspace.Gravity
			pv = e.vel * t + Vector3.new(0, -grav * 0.5 * t * t, 0) + Vector3.new(e.accel.X, 0, e.accel.Z) * (cfg.accelScale * 0.5 * t * t)
		else
			local dampedVel = Vector3.new(e.vel.X, e.vel.Y * cfg.yDamp, e.vel.Z)
			pv = dampedVel * t + Vector3.new(e.accel.X, 0, e.accel.Z) * (cfg.accelScale * 0.5 * t * t)
		end
		tgt = pv
		local m = tgt.Magnitude
		local dynMax = math.min(cfg.maxOfs, ws * ct * cfg.spdClamp)
		if m > dynMax then tgt = tgt * (dynMax / m) end
	else
		tgt = Vector3.zero
	end

	local a = expAlpha(adaptSmooth, dt)
	local desired = e.ofs:Lerp(tgt, a)
	local delta = desired - e.ofs
	local deltaMag = delta.Magnitude
	local maxDelta = maxSpd * dt * cfg.maxOfsRate
	if deltaMag > maxDelta and deltaMag > 0.001 then
		desired = e.ofs + delta * (maxDelta / deltaMag)
	end

	e.ofs = desired
	local ofsMag = e.ofs.Magnitude
	if ofsMag ~= ofsMag then
		e.ofs = Vector3.zero
		ofsMag = 0
	elseif ofsMag < 0.01 then
		e.ofs = Vector3.zero
		ofsMag = 0
	end

	if ofsMag > 0.01 and sc > 0.05 then
		e.conf = math.min(e.conf + 2.0 * dt, 1)
	else
		e.conf = math.max(e.conf - 3.0 * dt, 0)
	end

	local predPos = validatePos(engP, engP + e.ofs)
	e.pred = (cf - p) + predPos
	e.ok = true
end
local M = {}

function M.start()
	if running then return end
	running = true

	conns.leave = Players.PlayerRemoving:Connect(function(pl)
		ents[pl] = nil
	end)

	conns.hb = RunService.Heartbeat:Connect(function(rawDt)
		if not cfg.active then return end
		local dt = math.clamp(rawDt, cfg.minDt, cfg.maxDt)
		updateNet()

				local pls = Players:GetPlayers()
		table.clear(filterTable)
		local fi = 0
		for i = 1, #pls do
			local ch = pls[i].Character
			if ch then fi = fi + 1; filterTable[fi] = ch end
		end
		rcP.FilterDescendantsInstances = filterTable

		for i = 1, #pls do
			local pl = pls[i]
			if pl ~= lp then
				local ch = pl.Character
				if ch then
					local root = ch:FindFirstChild("HumanoidRootPart")
					local hum = ch:FindFirstChild("Humanoid")
					if root and hum and hum.Health > 0 then
						local e = ents[pl]
						if not e then e = newE(); ents[pl] = e end
						if e.char ~= ch then
							rstE(e)
							e.char = ch
						end
						e.root = root
						e.hum = hum
						e.alive = true
						updE(e, dt)
						if cfg.visual and root.Parent then
							root.CFrame = e.pred
							e.lastPP = e.pred.Position
						else
							e.lastPP = nil
						end
					else
						local e = ents[pl]
						if e and e.alive then
							e.alive = false
							if cfg.visual and e.ok and e.root and e.root.Parent and e.engPos then
								e.root.CFrame = (e.readCF - e.readCF.Position) + e.engPos
							end
						end
					end
				else
					local e = ents[pl]
					if e then e.alive = false end
				end
			end
		end
	end)
end

function M.stop()
	running = false
	for k, c in pairs(conns) do c:Disconnect(); conns[k] = nil end
	for _, e in pairs(ents) do
		if cfg.visual and e.ok and e.root and e.root.Parent and e.engPos then
			e.root.CFrame = (e.readCF - e.readCF.Position) + e.engPos
		end
	end
	table.clear(ents)
	table.clear(filterTable)
	rcP.FilterDescendantsInstances = filterTable
end

function M.predicted(pl)
	local e = ents[pl]
	return e and e.ok and e.pred.Position or nil
end

function M.predictedCF(pl)
	local e = ents[pl]
	return e and e.ok and e.pred or nil
end

function M.partPos(pl, name)
	local e = ents[pl]
	if not e or not e.ok or not e.char or not e.engPos then return nil end
	local pt = e.char:FindFirstChild(name)
	if not pt then return nil end
	return e.pred.Position + (pt.Position - e.readCF.Position)
end

function M.headPos(pl)
	return M.partPos(pl, "Head")
end

function M.leadPoint(pl, projSpd)
	local e = ents[pl]
	if not e or not e.ok then return nil end
	if not projSpd or projSpd <= 0 then return e.pred.Position end
	local mc = lp.Character
	local mr = mc and mc:FindFirstChild("HumanoidRootPart")
	if not mr then return e.pred.Position end
	local d = (e.pred.Position - mr.Position).Magnitude
	local t = d / projSpd + net.rtt * 0.5
	return e.pred.Position + e.vel * t + e.accel * (cfg.accelScale * 0.5 * t * t)
end

function M.nearest(fov, rng, los)
	local cam = Workspace.CurrentCamera
	if not cam then return nil end
	fov = fov or 15
	rng = rng or 500
	local o = cam.CFrame.Position
	local l = cam.CFrame.LookVector
	local best, bs = nil, math.huge
	for pl, e in pairs(ents) do
		if e.ok and e.alive then
			local dv = e.pred.Position - o
			local dm = dv.Magnitude
			if dm > 0.1 and dm < rng then
				local ang = math.deg(math.acos(math.clamp(l:Dot(dv / dm), -1, 1)))
				if ang < fov then
					if los then
						local hit = Workspace:Raycast(o, dv, rcP)
						if hit then continue end
					end
					local sc = ang + dm * 0.01
					if sc < bs then best, bs = pl, sc end
				end
			end
		end
	end
	return best
end

function M.velocity(pl)
	local e = ents[pl]
	return e and e.vel or nil
end

function M.moving(pl, t)
	local e = ents[pl]
	return e ~= nil and e.vel.Magnitude > (t or cfg.velMin)
end

function M.offset(pl)
	local e = ents[pl]
	return e and e.ofs or nil
end

function M.confidence(pl)
	local e = ents[pl]
	return e and e.conf or 0
end

function M.stats()
	return {
		rtt = net.rtt,
		rttMs = net.rtt * 1000,
		jitter = net.jit,
		jitterMs = net.jit * 1000,
		compMs = compT() * 1000,
		oneWayMs = net.rtt * 500,
	}
end

function M.allPreds()
	local r = {}
	for pl, e in pairs(ents) do
		if e.ok and e.alive then
			r[pl] = {
				position = e.pred.Position,
				cframe = e.pred,
				velocity = e.vel,
				offset = e.ofs,
				acceleration = e.accel,
				confidence = e.conf,
				airborne = e.airborne,
			}
		end
	end
	return r
end

function M.setVisual(on)
	if not on and cfg.visual then
		for _, e in pairs(ents) do
			if e.ok and e.root and e.root.Parent and e.engPos then
				e.root.CFrame = (e.readCF - e.readCF.Position) + e.engPos
			end
			e.ofs = Vector3.zero
			e.lastPP = nil
			e.stale = 0
			e.conf = 0
		end
	end
	cfg.visual = on
end

function M.setActive(on)
	cfg.active = on
	if not on then M.setVisual(false) end
end

function M.config()
	return cfg
end

M.start()
return M