local oldtypeof = typeof
local function typeof(objIn: any): string
	local objType = oldtypeof(objIn)
	if objType ~= "table" then return objType end

	local meta = getmetatable(objIn)
	if oldtypeof(meta) ~= "table" then return objType end

	local customType: string? = meta["__type"] 
	if customType == nil then return objType end
	return customType
end

type CanPierceFunction = (ActiveCast, RaycastResult, Vector3) -> boolean

 type GenericTable = {[any]: any}
 type Caster = {
	WorldRoot: WorldRoot,
	LengthChanged: RBXScriptSignal,
	RayHit: RBXScriptSignal,
	RayPierced: RBXScriptSignal,
	CastTerminating: RBXScriptSignal,
	Fire: (Vector3, Vector3, Vector3 | number, FastCastBehavior) -> ()
}

 type FastCastBehavior = {
	RaycastParams: RaycastParams?,
	MaxDistance: number,
	Acceleration: Vector3,
	HighFidelityBehavior: number,
	HighFidelitySegmentSize: number,
	CosmeticBulletTemplate: Instance?,
	CosmeticBulletProvider: any, -- Intended to be a PartCache. Dictated via TypeMarshaller.
	CosmeticBulletContainer: Instance?,
	AutoIgnoreContainer: boolean,
	CanPierceFunction: CanPierceFunction
}

 type CastTrajectory = {
	StartTime: number,
	EndTime: number,
	Origin: Vector3,
	InitialVelocity: Vector3,
	Acceleration: Vector3
}

 type CastStateInfo = {
	UpdateConnection: RBXScriptSignal,
	HighFidelityBehavior: number,
	HighFidelitySegmentSize: number,
	Paused: boolean,
	TotalRuntime: number,
	DistanceCovered: number,
	IsActivelySimulatingPierce: boolean,
	IsActivelyResimulating: boolean,
	CancelHighResCast: boolean,
	Trajectories: {[number]: CastTrajectory}
}
 type CastRayInfo = {
	Parameters: RaycastParams,
	WorldRoot: WorldRoot,
	MaxDistance: number,
	CosmeticBulletObject: Instance?,
	CanPierceCallback: CanPierceFunction
}

 type ActiveCast = {
	Caster: Caster,
	StateInfo: CastStateInfo,
	RayInfo: CastRayInfo,
	UserData: {[any]: any}
}
local RNG = Random.new()
local RobloxTable = table
local Table = {}
Table.insert = function (tbl, i, v)
	if tonumber(i) ~= nil then
		RobloxTable.insert(tbl, i, v)
	else
		RobloxTable.insert(tbl, i)
	end
end
Table.find = function (tbl, v)
	return RobloxTable.find(tbl, v)
end
Table.pack = function (...)
	return RobloxTable.pack(...)
end
Table.unpack = function (...)
	return RobloxTable.unpack(...)
end
Table.contains = function (tbl, value)
	return Table.indexOf(tbl, value) ~= nil -- This is kind of cheatsy but it promises the best performance.
end

Table.indexOf = function (tbl, value)
	local fromFind = table.find(tbl, value)
	if fromFind then return fromFind end
	
	return Table.keyOf(tbl, value)
end

Table.keyOf = function (tbl, value)
	for index, obj in pairs(tbl) do
		if obj == value then
			return index
		end
	end
	return nil
end

-- Only works on ordinal. yada yada.
Table.insertAndGetIndexOf = function (tbl, value)
	tbl[#tbl + 1] = value
	return #tbl
end

-- ONLY SUPPORTS ORDINAL TABLES (ARRAYS). Skips *n* objects in the table, and returns a new table that contains indices (n + 1) to (end of table)
Table.skip = function (tbl, n)
	return table.move(tbl, n+1, #tbl, 1, table.create(#tbl-n))
end

Table.take = function (tbl, n)
	return table.move(tbl, 1, n, 1, table.create(n))
end

Table.range = function (tbl, start, finish)
	return table.move(tbl, start, finish, 1, table.create(finish - start + 1))
end

Table.skipAndTake = function (tbl, skip, take)
	return table.move(tbl, skip + 1, skip + take, 1, table.create(take))
end

Table.random = function (tbl)
	return tbl[RNG:NextInteger(1, #tbl)]
end

Table.join = function (tbl0, tbl1)
	local nt = table.create(#tbl0 + #tbl1)
	local t2 = table.move(tbl0, 1, #tbl0, 1, nt)
	return table.move(tbl1, 1, #tbl1, #tbl0 + 1, nt)
end

Table.removeObject = function (tbl, obj)
	local index = Table.indexOf(tbl, obj)
	if index then
		table.remove(tbl, index)
	end
end
table = Table
local TestService = game:GetService("TestService")

local SignalStatic = {}
SignalStatic.__index = SignalStatic
SignalStatic.__type = "Signal" 
local ConnectionStatic = {}
ConnectionStatic.__index = ConnectionStatic
ConnectionStatic.__type = "SignalConnection" 
type Signal = {
	Name: string,
	Connections: {[number]: Connection},
	YieldingThreads: {[number]: BindableEvent}
}

type Connection = {
	Signal: Signal?,
	Delegate: any,
	Index: number	
}

-- Format params: methodName, ctorName
local ERR_NOT_INSTANCE = "Cannot statically invoke method '%s' - It is an instance method. Call it on an instance of this class created via %s"

function SignalStatic.new(signalName: string): Signal
	local signalObj: Signal = {
		Name = signalName,
		Connections = {},
		YieldingThreads = {}
	}
	return setmetatable(signalObj, SignalStatic)
end

local function NewConnection(sig: Signal, func: any): Connection 
	local connectionObj: Connection = {
		Signal = sig,
		Delegate = func,
		Index = -1
	}
	return setmetatable(connectionObj, ConnectionStatic)
end

local function ThreadAndReportError(delegate: any, args: GenericTable, handlerName: string)
	local thread = coroutine.create(function ()
		delegate(unpack(args))
	end)
	local success, msg = coroutine.resume(thread)
	if not success then 
		-- For the love of god roblox PLEASE add the ability to customize message type in output statements.
		-- This "testservice" garbage at the start of my message is annoying as all hell.
		TestService:Error(string.format("Exception thrown in your %s event handler: %s", handlerName, msg))
		TestService:Checkpoint(debug.traceback(thread))
	end
end

function SignalStatic:Connect(func)
	assert(getmetatable(self) == SignalStatic, ERR_NOT_INSTANCE:format("Connect", "Signal.new()"))
	local connection = NewConnection(self, func)
	connection.Index = #self.Connections + 1
	table.insert(self.Connections, connection.Index, connection)
	return connection
end

function SignalStatic:Fire(...)
	assert(getmetatable(self) == SignalStatic, ERR_NOT_INSTANCE:format("Fire", "Signal.new()"))
	local args = table.pack(...)
	local allCons = self.Connections
	local yieldingThreads = self.YieldingThreads
	for index = 1, #allCons do
		local connection = allCons[index]
		if connection.Delegate ~= nil then
			-- Catch case for disposed signals.
			ThreadAndReportError(connection.Delegate, args, connection.Signal.Name)
		end
	end
	for index = 1, #yieldingThreads do
		local thread = yieldingThreads[index]
		if thread ~= nil then
			coroutine.resume(thread, ...)
		end
	end
end

function SignalStatic:FireSync(...)
	assert(getmetatable(self) == SignalStatic, ERR_NOT_INSTANCE:format("FireSync", "Signal.new()"))
	local args = table.pack(...)
	local allCons = self.Connections
	local yieldingThreads = self.YieldingThreads
	for index = 1, #allCons do
		local connection = allCons[index]
		if connection.Delegate ~= nil then
			-- Catch case for disposed signals.
			connection.Delegate(unpack(args))
		end
	end
	for index = 1, #yieldingThreads do
		local thread = yieldingThreads[index]
		if thread ~= nil then
			coroutine.resume(thread, ...)
		end
	end
end

function SignalStatic:Wait()
	assert(getmetatable(self) == SignalStatic, ERR_NOT_INSTANCE:format("Wait", "Signal.new()"))
	local args = {}
	local thread = coroutine.running()
	table.insert(self.YieldingThreads, thread)
	args = { coroutine.yield() }
	table.removeObject(self.YieldingThreads, thread)
	return unpack(args)
end

function SignalStatic:Dispose()
	assert(getmetatable(self) == SignalStatic, ERR_NOT_INSTANCE:format("Dispose", "Signal.new()"))
	local allCons = self.Connections
	for index = 1, #allCons do
		allCons[index]:Disconnect()
	end
	self.Connections = {}
	setmetatable(self, nil)
end

function ConnectionStatic:Disconnect()
	assert(getmetatable(self) == ConnectionStatic, ERR_NOT_INSTANCE:format("Disconnect", "private function NewConnection()"))
	table.remove(self.Signal.Connections, self.Index)
	self.SignalStatic = nil
	self.Delegate = nil
	self.YieldingThreads = {}
	self.Index = -1
	setmetatable(self, nil)
end


local ActiveCastStatic = {}
ActiveCastStatic.__index = ActiveCastStatic
ActiveCastStatic.__type = "ActiveCast" -- For compatibility with TypeMarshaller
local RunService = game:GetService("RunService")
local FastCast = nil 

local ERR_NOT_INSTANCE = "Cannot statically invoke method '%s' - It is an instance method. Call it on an instance of this class created via %s"

local ERR_INVALID_TYPE = "Invalid type for parameter '%s' (Expected %s, got %s)"

-- The name of the folder containing the 3D GUI elements for visualizing casts in debug mode.
local FC_VIS_OBJ_NAME = "FastCastVisualizationObjects"

-- Format params: N/A
local ERR_OBJECT_DISPOSED = "This ActiveCast has been terminated. It can no longer be used."

-- If pierce callback has to run more than this many times, it will register a hit and stop calculating pierces.
-- This only applies for repeated piercings, e.g. the amount of parts that fit within the space of a single cast segment (NOT the whole bullet's trajectory over its entire lifetime)
local MAX_PIERCE_TEST_COUNT = 100

-----------------------------------------------------------
------------------------ UTILITIES ------------------------
-----------------------------------------------------------

-- Looks for a folder within workspace.Terrain that contains elements to visualize casts.
local function GetFastCastVisualizationContainer(): Instance
	local fcVisualizationObjects = workspace.Terrain:FindFirstChild(FC_VIS_OBJ_NAME)
	if fcVisualizationObjects ~= nil then
		return fcVisualizationObjects
	end
	
	fcVisualizationObjects = Instance.new("Folder")
	fcVisualizationObjects.Name = FC_VIS_OBJ_NAME
	fcVisualizationObjects.Archivable = false 
	fcVisualizationObjects.Parent = workspace.Terrain
	return fcVisualizationObjects
end

-----------------------------------------------------------
------------------------ DEBUGGING ------------------------
-----------------------------------------------------------

-- Print that runs only if debug mode is active.
local function PrintDebug(message: string)
	if FastCast.DebugLogging == true then
		print(message)
	end
end

-- Visualizes a ray. This will not run if FastCast.VisualizeCasts is false.
function DbgVisualizeSegment(castStartCFrame: CFrame, castLength: number): ConeHandleAdornment?
	if FastCast.VisualizeCasts ~= true then return nil end
	local adornment = Instance.new("ConeHandleAdornment")
	adornment.Adornee = workspace.Terrain
	adornment.CFrame = castStartCFrame
	adornment.Height = castLength
	adornment.Color3 = Color3.new()
	adornment.Radius = 0.25
	adornment.Transparency = 0.5
	adornment.Parent = GetFastCastVisualizationContainer()
	return adornment
end

-- Visualizes an impact. This will not run if FastCast.VisualizeCasts is false.
function DbgVisualizeHit(atCF: CFrame, wasPierce: boolean): SphereHandleAdornment?
	if FastCast.VisualizeCasts ~= true then return nil end
	local adornment = Instance.new("SphereHandleAdornment")
	adornment.Adornee = workspace.Terrain
	adornment.CFrame = atCF
	adornment.Radius = 0.4
	adornment.Transparency = 0.25
	adornment.Color3 = (wasPierce == false) and Color3.new(0.2, 1, 0.5) or Color3.new(1, 0.2, 0.2)
	adornment.Parent = GetFastCastVisualizationContainer()
	return adornment
end

-----------------------------------------------------------
------------------------ CORE CODE ------------------------
-----------------------------------------------------------

-- Thanks to zoebasil for supplying the velocity and position functions below. (I've modified these functions)
-- I was having a huge issue trying to get it to work and I had overcomplicated a bunch of stuff.
-- GetPositionAtTime is used in physically simulated rays (Where Caster.HasPhysics == true or the specific Fire has a specified acceleration).
-- This returns the location that the bullet will be at when you specify the amount of time the bullet has existed, the original location of the bullet, and the velocity it was launched with.
local function GetPositionAtTime(time: number, origin: Vector3, initialVelocity: Vector3, acceleration: Vector3): Vector3
	local force = Vector3.new((acceleration.X * time^2) / 2,(acceleration.Y * time^2) / 2, (acceleration.Z * time^2) / 2)
	return origin + (initialVelocity * time) + force
end

-- A variant of the function above that returns the velocity at a given point in time.
local function GetVelocityAtTime(time: number, initialVelocity: Vector3, acceleration: Vector3): Vector3
	return initialVelocity + acceleration * time
end

local function GetTrajectoryInfo(cast: ActiveCast, index: number): {[number]: Vector3}
	assert(cast.StateInfo.UpdateConnection ~= nil, ERR_OBJECT_DISPOSED)
	local trajectories = cast.StateInfo.Trajectories
	local trajectory = trajectories[index]
	local duration = trajectory.EndTime - trajectory.StartTime
	
	local origin = trajectory.Origin
	local vel = trajectory.InitialVelocity
	local accel = trajectory.Acceleration
	
	return {GetPositionAtTime(duration, origin, vel, accel), GetVelocityAtTime(duration, vel, accel)}
end

local function GetLatestTrajectoryEndInfo(cast: ActiveCast): {[number]: Vector3}
	assert(cast.StateInfo.UpdateConnection ~= nil, ERR_OBJECT_DISPOSED)
	return GetTrajectoryInfo(cast, #cast.StateInfo.Trajectories)
end

local function CloneCastParams(params: RaycastParams): RaycastParams
	local clone = RaycastParams.new()
	clone.CollisionGroup = params.CollisionGroup
	clone.FilterType = params.FilterType
	clone.FilterDescendantsInstances = params.FilterDescendantsInstances
	clone.IgnoreWater = params.IgnoreWater
	return clone
end

local function SendRayHit(cast: ActiveCast, resultOfCast: RaycastResult, segmentVelocity: Vector3, cosmeticBulletObject: Instance?)
	--cast.RayHit:Fire(cast, resultOfCast, segmentVelocity, cosmeticBulletObject)
	cast.Caster.RayHit:Fire(cast, resultOfCast, segmentVelocity, cosmeticBulletObject)
end

local function SendRayPierced(cast: ActiveCast, resultOfCast: RaycastResult, segmentVelocity: Vector3, cosmeticBulletObject: Instance?)
	--cast.RayPierced:Fire(cast, resultOfCast, segmentVelocity, cosmeticBulletObject)
	cast.Caster.RayPierced:Fire(cast, resultOfCast, segmentVelocity, cosmeticBulletObject)
end

local function SendLengthChanged(cast: ActiveCast, lastPoint: Vector3, rayDir: Vector3, rayDisplacement: number, segmentVelocity: Vector3, cosmeticBulletObject: Instance?)
	--cast.LengthChanged:Fire(cast, lastPoint, rayDir, rayDisplacement, segmentVelocity, cosmeticBulletObject)
	cast.Caster.LengthChanged:Fire(cast, lastPoint, rayDir, rayDisplacement, segmentVelocity, cosmeticBulletObject)
end

-- Simulate a raycast by one tick.
local function SimulateCast(cast: ActiveCast, delta: number, expectingShortCall: boolean)
	assert(cast.StateInfo.UpdateConnection ~= nil, ERR_OBJECT_DISPOSED)
	PrintDebug("Casting for frame.")
	local latestTrajectory = cast.StateInfo.Trajectories[#cast.StateInfo.Trajectories]
	
	local origin = latestTrajectory.Origin
	local totalDelta = cast.StateInfo.TotalRuntime - latestTrajectory.StartTime
	local initialVelocity = latestTrajectory.InitialVelocity
	local acceleration = latestTrajectory.Acceleration
	
	local lastPoint = GetPositionAtTime(totalDelta, origin, initialVelocity, acceleration)
	local lastVelocity = GetVelocityAtTime(totalDelta, initialVelocity, acceleration)
	local lastDelta = cast.StateInfo.TotalRuntime - latestTrajectory.StartTime
	
	cast.StateInfo.TotalRuntime += delta
	
	-- Recalculate this.
	totalDelta = cast.StateInfo.TotalRuntime - latestTrajectory.StartTime
	
	local currentTarget = GetPositionAtTime(totalDelta, origin, initialVelocity, acceleration)
	local segmentVelocity = GetVelocityAtTime(totalDelta, initialVelocity, acceleration) 
	local totalDisplacement = currentTarget - lastPoint -- This is the displacement from where the ray was on the last from to where the ray is now.
	
	local rayDir = totalDisplacement.Unit * segmentVelocity.Magnitude * delta
	local targetWorldRoot = cast.RayInfo.WorldRoot
	local resultOfCast = targetWorldRoot:Raycast(lastPoint, rayDir, cast.RayInfo.Parameters)
	
	local point = currentTarget
	local part: Instance? = nil
	local material = Enum.Material.Air
	local normal = Vector3.new()
	
	if (resultOfCast ~= nil) then
		point = resultOfCast.Position
		part = resultOfCast.Instance
		material = resultOfCast.Material
		normal = resultOfCast.Normal
	end
	
	local rayDisplacement = (point - lastPoint).Magnitude
	-- For clarity -- totalDisplacement is how far the ray would have traveled if it hit nothing,
	-- and rayDisplacement is how far the ray really traveled (which will be identical to totalDisplacement if it did indeed hit nothing)
	
	SendLengthChanged(cast, lastPoint, rayDir.Unit, rayDisplacement, segmentVelocity, cast.RayInfo.CosmeticBulletObject)
	cast.StateInfo.DistanceCovered += rayDisplacement
	
	local rayVisualization: ConeHandleAdornment? = nil
	if (delta > 0) then
		rayVisualization = DbgVisualizeSegment(CFrame.new(lastPoint, lastPoint + rayDir), rayDisplacement)
	end
	
	
	-- HIT DETECTED. Handle all that garbage, and also handle behaviors 1 and 2 (default behavior, go high res when hit) if applicable.
	-- CAST BEHAVIOR 2 IS HANDLED IN THE CODE THAT CALLS THIS FUNCTION.
	
	if part and part ~= cast.RayInfo.CosmeticBulletObject then
		local start = tick()
		PrintDebug("Hit something, testing now.")
		
		-- SANITY CHECK: Don't allow the user to yield or run otherwise extensive code that takes longer than one frame/heartbeat to execute.
		if (cast.RayInfo.CanPierceCallback ~= nil) then
			if expectingShortCall == false then
				if (cast.StateInfo.IsActivelySimulatingPierce) then
					cast:Terminate()
					error("ERROR: The latest call to CanPierceCallback took too long to complete! This cast is going to suffer desyncs which WILL cause unexpected behavior and errors. Please fix your performance problems, or remove statements that yield (e.g. wait() calls)")
					-- Use error. This should absolutely abort the cast.
				end
			end
			-- expectingShortCall is used to determine if we are doing a forced resolution increase, in which case this will be called several times in a single frame, which throws this error.
			cast.StateInfo.IsActivelySimulatingPierce = true
		end
		------------------------------
		
		if cast.RayInfo.CanPierceCallback == nil or (cast.RayInfo.CanPierceCallback ~= nil and cast.RayInfo.CanPierceCallback(cast, resultOfCast, segmentVelocity, cast.RayInfo.CosmeticBulletObject) == false) then
			PrintDebug("Piercing function is nil or it returned FALSE to not pierce this hit.")
			cast.StateInfo.IsActivelySimulatingPierce = false
			
			if (cast.StateInfo.HighFidelityBehavior == 2 and latestTrajectory.Acceleration ~= Vector3.new() and cast.StateInfo.HighFidelitySegmentSize ~= 0) then
				cast.StateInfo.CancelHighResCast = false -- Reset this here.
				
				if cast.StateInfo.IsActivelyResimulating then
					cast:Terminate()
					error("Cascading cast lag encountered! The caster attempted to perform a high fidelity cast before the previous one completed, resulting in exponential cast lag. Consider increasing HighFidelitySegmentSize.")
				end
				

				cast.StateInfo.IsActivelyResimulating = true
				
				-- This is a physics based cast and it needs to be recalculated.
				PrintDebug("Hit was registered, but recalculation is on for physics based casts. Recalculating to verify a real hit...")
				
				-- Split this ray segment into smaller segments of a given size.
				-- In 99% of cases, it won't divide evently (e.g. I have a distance of 1.25 and I want to divide into 0.1 -- that won't work)
				-- To fix this, the segments need to be stretched slightly to fill the space (rather than having a single shorter segment at the end)
				
				local numSegmentsDecimal = rayDisplacement / cast.StateInfo.HighFidelitySegmentSize -- say rayDisplacement is 5.1, segment size is 0.5 -- 10.2 segments
				local numSegmentsReal = math.floor(numSegmentsDecimal) -- 10 segments + 0.2 extra segments
				local realSegmentLength = rayDisplacement / numSegmentsReal -- this spits out 0.51, which isn't exact to the defined 0.5, but it's close
				
				-- Now the real hard part is converting this to time.
				local timeIncrement = delta / numSegmentsReal
				for segmentIndex = 1, numSegmentsReal do
					if cast.StateInfo.CancelHighResCast then
						cast.StateInfo.CancelHighResCast = false
						break
					end
					
					local subPosition = GetPositionAtTime(lastDelta + (timeIncrement * segmentIndex), origin, initialVelocity, acceleration)
					local subVelocity = GetVelocityAtTime(lastDelta + (timeIncrement * segmentIndex), initialVelocity, acceleration) 
					local subRayDir = subVelocity * delta
					local subResult = targetWorldRoot:Raycast(subPosition, subRayDir, cast.RayInfo.Parameters)
					
					local subDisplacement = (subPosition - (subPosition + subVelocity)).Magnitude
					
					if (subResult ~= nil) then
						local subDisplacement = (subPosition - subResult.Position).Magnitude
						local dbgSeg = DbgVisualizeSegment(CFrame.new(subPosition, subPosition + subVelocity), subDisplacement)
						if (dbgSeg ~= nil) then dbgSeg.Color3 = Color3.new(0.286275, 0.329412, 0.247059) end
						
						if cast.RayInfo.CanPierceCallback == nil or (cast.RayInfo.CanPierceCallback ~= nil and cast.RayInfo.CanPierceCallback(cast, subResult, subVelocity, cast.RayInfo.CosmeticBulletObject) == false) then
							-- Still hit even at high res
							cast.StateInfo.IsActivelyResimulating = false
							
							SendRayHit(cast, subResult, subVelocity, cast.RayInfo.CosmeticBulletObject)
							cast:Terminate()
							local vis = DbgVisualizeHit(CFrame.new(point), false)
							if (vis ~= nil) then vis.Color3 = Color3.new(0.0588235, 0.87451, 1) end
							return
						else
							-- Recalculating hit something pierceable instead.
							SendRayPierced(cast, subResult, subVelocity, cast.RayInfo.CosmeticBulletObject) -- This may result in CancelHighResCast being set to true.
							local vis = DbgVisualizeHit(CFrame.new(point), true)
							if (vis ~= nil) then vis.Color3 = Color3.new(1, 0.113725, 0.588235) end
							if (dbgSeg ~= nil) then dbgSeg.Color3 = Color3.new(0.305882, 0.243137, 0.329412) end
						end
					else
						local dbgSeg = DbgVisualizeSegment(CFrame.new(subPosition, subPosition + subVelocity), subDisplacement)
						if (dbgSeg ~= nil) then dbgSeg.Color3 = Color3.new(0.286275, 0.329412, 0.247059) end
						
					end
				end
				
				-- If the script makes it here, then it wasn't a real hit (higher resolution revealed that the low-res hit was faulty)
				-- Just let it keep going.
				cast.StateInfo.IsActivelyResimulating = false
			elseif (cast.StateInfo.HighFidelityBehavior ~= 1 and cast.StateInfo.HighFidelityBehavior ~= 3) then
				cast:Terminate()
				error("Invalid value " .. (cast.StateInfo.HighFidelityBehavior) .. " for HighFidelityBehavior.")
			else
				-- This is not a physics cast, or recalculation is off.
				PrintDebug("Hit was successful. Terminating.")
				SendRayHit(cast, resultOfCast, segmentVelocity, cast.RayInfo.CosmeticBulletObject)
				cast:Terminate()
				DbgVisualizeHit(CFrame.new(point), false)
				return
			end
		else
			PrintDebug("Piercing function returned TRUE to pierce this part.")
			if rayVisualization ~= nil then
				rayVisualization.Color3 = Color3.new(0.4, 0.05, 0.05) -- Turn it red to signify that the cast was scrapped.
			end
			DbgVisualizeHit(CFrame.new(point), true)
			
			local params = cast.RayInfo.Parameters
			local alteredParts = {}
			local currentPierceTestCount = 0
			local originalFilter = params.FilterDescendantsInstances
			local brokeFromSolidObject = false
			while true do
				-- So now what I need to do is redo this entire cast, just with the new filter list
								
				-- Catch case: Is it terrain?
				if resultOfCast.Instance:IsA("Terrain") then
					if material == Enum.Material.Water then
						-- Special case: Pierced on water?
						cast:Terminate()
						error("Do not add Water as a piercable material. If you need to pierce water, set cast.RayInfo.Parameters.IgnoreWater = true instead", 0)
					end
					warn("WARNING: The pierce callback for this cast returned TRUE on Terrain! This can cause severely adverse effects.")
				end
				
				if params.FilterType == Enum.RaycastFilterType.Blacklist then
					-- blacklist
					-- DO NOT DIRECTLY TABLE.INSERT ON THE PROPERTY
					local filter = params.FilterDescendantsInstances
					table.insert(filter, resultOfCast.Instance)
					table.insert(alteredParts, resultOfCast.Instance)
					params.FilterDescendantsInstances = filter
				else
					-- whitelist
					-- method implemeneted by custom table system
					-- DO NOT DIRECTLY TABLE.REMOVEOBJECT ON THE PROPERTY
					local filter = params.FilterDescendantsInstances
					table.removeObject(filter, resultOfCast.Instance)
					table.insert(alteredParts, resultOfCast.Instance)
					params.FilterDescendantsInstances = filter
				end
				
				SendRayPierced(cast, resultOfCast, segmentVelocity, cast.RayInfo.CosmeticBulletObject)
				
				-- List has been updated, so let's cast again.
				resultOfCast = targetWorldRoot:Raycast(lastPoint, rayDir, params)
				
				-- No hit? No simulation. Break.
				if resultOfCast == nil then
					break
				end
				
				if currentPierceTestCount >= MAX_PIERCE_TEST_COUNT then
					warn("WARNING: Exceeded maximum pierce test budget for a single ray segment (attempted to test the same segment " .. MAX_PIERCE_TEST_COUNT .. " times!)")
					break
				end
				currentPierceTestCount = currentPierceTestCount + 1;
				
				if cast.RayInfo.CanPierceCallback(cast, resultOfCast, segmentVelocity, cast.RayInfo.CosmeticBulletObject) == false then
					brokeFromSolidObject = true
					break
				end
			end
			
			-- Restore the filter to its default state.
			cast.RayInfo.Parameters.FilterDescendantsInstances = originalFilter
			cast.StateInfo.IsActivelySimulatingPierce = false
			
			if brokeFromSolidObject then
				-- We actually hit something while testing.
				PrintDebug("Broke because the ray hit something solid (" .. tostring(resultOfCast.Instance) .. ") while testing for a pierce. Terminating the cast.")
				SendRayHit(cast, resultOfCast, segmentVelocity, cast.RayInfo.CosmeticBulletObject)
				cast:Terminate()
				DbgVisualizeHit(CFrame.new(resultOfCast.Position), false)
				return
			end
			
			-- And exit the function here too.
		end
	end
	
	if (cast.StateInfo.DistanceCovered >= cast.RayInfo.MaxDistance) then
		-- SendRayHit(cast, nil, segmentVelocity, cast.RayInfo.CosmeticBulletObject)
		cast:Terminate()
		DbgVisualizeHit(CFrame.new(currentTarget), false)
	end
end

function ActiveCastStatic.new(caster: Caster, origin: Vector3, direction: Vector3, velocity: Vector3 | number, castDataPacket: FastCastBehavior): ActiveCast
	if typeof(velocity) == "number" then
		velocity = direction.Unit * velocity
	end	
	
	if (castDataPacket.HighFidelitySegmentSize <= 0) then
		error("Cannot set FastCastBehavior.HighFidelitySegmentSize <= 0!", 0)
	end
	
	-- Basic setup
	local cast = {
		Caster = caster,
		
		-- Data that keeps track of what's going on as well as edits we might make during runtime.
		StateInfo = {
			UpdateConnection = nil,
			Paused = false,
			TotalRuntime = 0,
			DistanceCovered = 0,
			HighFidelitySegmentSize = castDataPacket.HighFidelitySegmentSize,
			HighFidelityBehavior = castDataPacket.HighFidelityBehavior,
			IsActivelySimulatingPierce = false,
			IsActivelyResimulating = false,
			CancelHighResCast = false,
			Trajectories = {
				{
					StartTime = 0,
					EndTime = -1,
					Origin = origin,
					InitialVelocity = velocity,
					Acceleration = castDataPacket.Acceleration
				}
			}
		},
		
		-- Information pertaining to actual raycasting.
		RayInfo = {
			Parameters = castDataPacket.RaycastParams,
			WorldRoot = workspace,
			MaxDistance = castDataPacket.MaxDistance or 1000,
			CosmeticBulletObject = castDataPacket.CosmeticBulletTemplate, -- This is intended. We clone it a smidge of the way down.
			CanPierceCallback = castDataPacket.CanPierceFunction
		},
		
		UserData = {}
	}
	
	if cast.StateInfo.HighFidelityBehavior == 2 then
		cast.StateInfo.HighFidelityBehavior = 3
	end
	
	
	if cast.RayInfo.Parameters ~= nil then
		cast.RayInfo.Parameters = CloneCastParams(cast.RayInfo.Parameters)
	else
		cast.RayInfo.Parameters = RaycastParams.new()
	end

	local usingProvider = false
	if castDataPacket.CosmeticBulletProvider == nil then
		-- The provider is nil. Use a cosmetic object clone.
		if cast.RayInfo.CosmeticBulletObject ~= nil then
			cast.RayInfo.CosmeticBulletObject = cast.RayInfo.CosmeticBulletObject:Clone()
			cast.RayInfo.CosmeticBulletObject.CFrame = CFrame.new(origin, origin + direction)
			cast.RayInfo.CosmeticBulletObject.Parent = castDataPacket.CosmeticBulletContainer
		end
	else
		-- The provider is not nil.
		-- Is it what we want?
		if typeof(castDataPacket.CosmeticBulletProvider) == "PartCache" then
			-- this modded version of typeof is implemented up top.
			-- Aside from that, yes, it's a part cache. Good to go!
			
			if cast.RayInfo.CosmeticBulletObject ~= nil then
				-- They also set the template. Not good. Warn + clear this up.
				warn("Do not define FastCastBehavior.CosmeticBulletTemplate and FastCastBehavior.CosmeticBulletProvider at the same time! The provider will be used, and CosmeticBulletTemplate will be set to nil.")
				cast.RayInfo.CosmeticBulletObject = nil
				castDataPacket.CosmeticBulletTemplate = nil
			end

			cast.RayInfo.CosmeticBulletObject = castDataPacket.CosmeticBulletProvider:GetPart()
			cast.RayInfo.CosmeticBulletObject.CFrame = CFrame.new(origin, origin + direction)
			usingProvider = true
		else
			warn("FastCastBehavior.CosmeticBulletProvider was not an instance of the PartCache module (an external/separate model)! Are you inputting an instance created via PartCache.new? If so, are you on the latest version of PartCache? Setting FastCastBehavior.CosmeticBulletProvider to nil.")
			castDataPacket.CosmeticBulletProvider = nil
		end
	end

	local targetContainer: Instance;
	if usingProvider then
		targetContainer = castDataPacket.CosmeticBulletProvider.CurrentCacheParent
	else
		targetContainer = castDataPacket.CosmeticBulletContainer
	end
	
	if castDataPacket.AutoIgnoreContainer == true and targetContainer ~= nil then
		local ignoreList = cast.RayInfo.Parameters.FilterDescendantsInstances
		if table.find(ignoreList, targetContainer) == nil then
			table.insert(ignoreList, targetContainer)
			cast.RayInfo.Parameters.FilterDescendantsInstances = ignoreList
		end
	end
	
	local event
	if RunService:IsClient() then
		event = RunService.RenderStepped
	else
		event = RunService.Heartbeat
	end
	
	setmetatable(cast, ActiveCastStatic)
	
	cast.StateInfo.UpdateConnection = event:Connect(function (delta)
		if cast.StateInfo.Paused then return end
		
		PrintDebug("Casting for frame.")
		local latestTrajectory = cast.StateInfo.Trajectories[#cast.StateInfo.Trajectories]
		if (cast.StateInfo.HighFidelityBehavior == 3 and latestTrajectory.Acceleration ~= Vector3.new() and cast.StateInfo.HighFidelitySegmentSize > 0) then
			
			local timeAtStart = tick()
			
			if cast.StateInfo.IsActivelyResimulating then
				cast:Terminate()
				error("Cascading cast lag encountered! The caster attempted to perform a high fidelity cast before the previous one completed, resulting in exponential cast lag. Consider increasing HighFidelitySegmentSize.")
			end
			
			cast.StateInfo.IsActivelyResimulating = true
			
			-- Actually want to calculate this early to find displacement
			local origin = latestTrajectory.Origin
			local totalDelta = cast.StateInfo.TotalRuntime - latestTrajectory.StartTime
			local initialVelocity = latestTrajectory.InitialVelocity
			local acceleration = latestTrajectory.Acceleration
			
			local lastPoint = GetPositionAtTime(totalDelta, origin, initialVelocity, acceleration)
			local lastVelocity = GetVelocityAtTime(totalDelta, initialVelocity, acceleration)
			local lastDelta = cast.StateInfo.TotalRuntime - latestTrajectory.StartTime
			
			cast.StateInfo.TotalRuntime += delta
			
			-- Recalculate this.
			totalDelta = cast.StateInfo.TotalRuntime - latestTrajectory.StartTime
			
			local currentPoint = GetPositionAtTime(totalDelta, origin, initialVelocity, acceleration)
			local currentVelocity = GetVelocityAtTime(totalDelta, initialVelocity, acceleration) 
			local totalDisplacement = currentPoint - lastPoint -- This is the displacement from where the ray was on the last from to where the ray is now.
			
			local rayDir = totalDisplacement.Unit * currentVelocity.Magnitude * delta
			local targetWorldRoot = cast.RayInfo.WorldRoot
			local resultOfCast = targetWorldRoot:Raycast(lastPoint, rayDir, cast.RayInfo.Parameters)
			
			local point = currentPoint
			
			if (resultOfCast ~= nil) then
				point = resultOfCast.Position
			end
			
			local rayDisplacement = (point - lastPoint).Magnitude
			
			-- Now undo this. The line below in the for loop will add this time back gradually.
			cast.StateInfo.TotalRuntime -= delta
			
			-- And now that we have displacement, we can calculate segment size.
			local numSegmentsDecimal = rayDisplacement / cast.StateInfo.HighFidelitySegmentSize -- say rayDisplacement is 5.1, segment size is 0.5 -- 10.2 segments
			local numSegmentsReal = math.floor(numSegmentsDecimal) -- 10 segments + 0.2 extra segments
			if (numSegmentsReal == 0) then
				numSegmentsReal = 1
			end
			
			local timeIncrement = delta / numSegmentsReal
			
			for segmentIndex = 1, numSegmentsReal do
				if getmetatable(cast) == nil then return end -- Could have been disposed.
				if cast.StateInfo.CancelHighResCast then
					cast.StateInfo.CancelHighResCast = false
					break
				end
				PrintDebug("[" .. segmentIndex .. "] Subcast of time increment " .. timeIncrement)
				SimulateCast(cast, timeIncrement, true)
			end
			
			if getmetatable(cast) == nil then return end -- Could have been disposed.
			cast.StateInfo.IsActivelyResimulating = false
			
			if (tick() - timeAtStart) > 0.016 * 5 then
				warn("Extreme cast lag encountered! Consider increasing HighFidelitySegmentSize.")
			end
			
		else
			SimulateCast(cast, delta, false)
		end
	end)
	
	return cast
end

function ActiveCastStatic.SetStaticFastCastReference(ref)
	FastCast = ref
end

---- GETTERS AND SETTERS ----

local function ModifyTransformation(cast: ActiveCast, velocity: Vector3?, acceleration: Vector3?, position: Vector3?)
	local trajectories = cast.StateInfo.Trajectories
	local lastTrajectory = trajectories[#trajectories]
	
	-- NEW BEHAVIOR: Don't create a new trajectory if we haven't even used the current one.
	if lastTrajectory.StartTime == cast.StateInfo.TotalRuntime then
		-- This trajectory is fresh out of the box. Let's just change it since it hasn't actually affected the cast yet, so changes won't have adverse effects.
		if (velocity == nil) then
			velocity = lastTrajectory.InitialVelocity
		end
		if (acceleration == nil) then
			acceleration = lastTrajectory.Acceleration
		end
		if (position == nil) then
			position = lastTrajectory.Origin
		end	
		
		lastTrajectory.Origin = position
		lastTrajectory.InitialVelocity = velocity
		lastTrajectory.Acceleration = acceleration
	else
		-- The latest trajectory is done. Set its end time and get its location. 
		lastTrajectory.EndTime = cast.StateInfo.TotalRuntime
		
		local point, velAtPoint = unpack(GetLatestTrajectoryEndInfo(cast))
		
		if (velocity == nil) then
			velocity = velAtPoint
		end
		if (acceleration == nil) then
			acceleration = lastTrajectory.Acceleration
		end
		if (position == nil) then
			position = point
		end	
		table.insert(cast.StateInfo.Trajectories, {
			StartTime = cast.StateInfo.TotalRuntime,
			EndTime = -1,
			Origin = position,
			InitialVelocity = velocity,
			Acceleration = acceleration
		})
		cast.StateInfo.CancelHighResCast = true
	end
end

function ActiveCastStatic:SetVelocity(velocity: Vector3)
	assert(getmetatable(self) == ActiveCastStatic, ERR_NOT_INSTANCE:format("SetVelocity", "ActiveCast.new(...)"))
	assert(self.StateInfo.UpdateConnection ~= nil, ERR_OBJECT_DISPOSED)
	ModifyTransformation(self, velocity, nil, nil)
end

function ActiveCastStatic:SetAcceleration(acceleration: Vector3)
	assert(getmetatable(self) == ActiveCastStatic, ERR_NOT_INSTANCE:format("SetAcceleration", "ActiveCast.new(...)"))
	assert(self.StateInfo.UpdateConnection ~= nil, ERR_OBJECT_DISPOSED)
	ModifyTransformation(self, nil, acceleration, nil)
end

function ActiveCastStatic:SetPosition(position: Vector3)
	assert(getmetatable(self) == ActiveCastStatic, ERR_NOT_INSTANCE:format("SetPosition", "ActiveCast.new(...)"))
	assert(self.StateInfo.UpdateConnection ~= nil, ERR_OBJECT_DISPOSED)
	ModifyTransformation(self, nil, nil, position)
end

function ActiveCastStatic:GetVelocity(): Vector3
	assert(getmetatable(self) == ActiveCastStatic, ERR_NOT_INSTANCE:format("GetVelocity", "ActiveCast.new(...)"))
	assert(self.StateInfo.UpdateConnection ~= nil, ERR_OBJECT_DISPOSED)
	local currentTrajectory = self.StateInfo.Trajectories[#self.StateInfo.Trajectories]
	return GetVelocityAtTime(self.StateInfo.TotalRuntime - currentTrajectory.StartTime, currentTrajectory.InitialVelocity, currentTrajectory.Acceleration)
end

function ActiveCastStatic:GetAcceleration(): Vector3
	assert(getmetatable(self) == ActiveCastStatic, ERR_NOT_INSTANCE:format("GetAcceleration", "ActiveCast.new(...)"))
	assert(self.StateInfo.UpdateConnection ~= nil, ERR_OBJECT_DISPOSED)
	local currentTrajectory = self.StateInfo.Trajectories[#self.StateInfo.Trajectories]
	return currentTrajectory.Acceleration
end

function ActiveCastStatic:GetPosition(): Vector3
	assert(getmetatable(self) == ActiveCastStatic, ERR_NOT_INSTANCE:format("GetPosition", "ActiveCast.new(...)"))
	assert(self.StateInfo.UpdateConnection ~= nil, ERR_OBJECT_DISPOSED)
	local currentTrajectory = self.StateInfo.Trajectories[#self.StateInfo.Trajectories]
	return GetPositionAtTime(self.StateInfo.TotalRuntime - currentTrajectory.StartTime, currentTrajectory.Origin, currentTrajectory.InitialVelocity, currentTrajectory.Acceleration)
end

---- ARITHMETIC ----

function ActiveCastStatic:AddVelocity(velocity: Vector3)
	assert(getmetatable(self) == ActiveCastStatic, ERR_NOT_INSTANCE:format("AddVelocity", "ActiveCast.new(...)"))
	assert(self.StateInfo.UpdateConnection ~= nil, ERR_OBJECT_DISPOSED)
	self:SetVelocity(self:GetVelocity() + velocity)
end

function ActiveCastStatic:AddAcceleration(acceleration: Vector3)
	assert(getmetatable(self) == ActiveCastStatic, ERR_NOT_INSTANCE:format("AddAcceleration", "ActiveCast.new(...)"))
	assert(self.StateInfo.UpdateConnection ~= nil, ERR_OBJECT_DISPOSED)
	self:SetAcceleration(self:GetAcceleration() + acceleration)
end

function ActiveCastStatic:AddPosition(position: Vector3)
	assert(getmetatable(self) == ActiveCastStatic, ERR_NOT_INSTANCE:format("AddPosition", "ActiveCast.new(...)"))
	assert(self.StateInfo.UpdateConnection ~= nil, ERR_OBJECT_DISPOSED)
	self:SetPosition(self:GetPosition() + position)
end

---- STATE MODIFICATION ----

function ActiveCastStatic:Pause()
	assert(getmetatable(self) == ActiveCastStatic, ERR_NOT_INSTANCE:format("Pause", "ActiveCast.new(...)"))
	assert(self.StateInfo.UpdateConnection ~= nil, ERR_OBJECT_DISPOSED)
	self.StateInfo.Paused = true
end

function ActiveCastStatic:Resume()
	assert(getmetatable(self) == ActiveCastStatic, ERR_NOT_INSTANCE:format("Resume", "ActiveCast.new(...)"))
	assert(self.StateInfo.UpdateConnection ~= nil, ERR_OBJECT_DISPOSED)
	self.StateInfo.Paused = false
end

function ActiveCastStatic:Terminate()
	assert(getmetatable(self) == ActiveCastStatic, ERR_NOT_INSTANCE:format("Terminate", "ActiveCast.new(...)"))
	assert(self.StateInfo.UpdateConnection ~= nil, ERR_OBJECT_DISPOSED)
	
	-- First: Set EndTime on the latest trajectory since it is now done simulating.
	local trajectories = self.StateInfo.Trajectories
	local lastTrajectory = trajectories[#trajectories]
	lastTrajectory.EndTime = self.StateInfo.TotalRuntime
	
	-- Disconnect the update connection.
	self.StateInfo.UpdateConnection:Disconnect()
	
	-- Now fire CastTerminating
	self.Caster.CastTerminating:FireSync(self)
	
	-- And now set the update connection object to nil.
	self.StateInfo.UpdateConnection = nil
	
	-- And nuke everything in the table + clear the metatable.
	self.Caster = nil
	self.StateInfo = nil
	self.RayInfo = nil
	self.UserData = nil
	setmetatable(self, nil)
end

local FastCast = {}
FastCast.DebugLogging = false
FastCast.VisualizeCasts = false
FastCast.__index = FastCast
FastCast.__type = "FastCast" 
-- Extra stuff
FastCast.HighFidelityBehavior = {
	Default = 1,
	Always = 3
}

local Signal = SignalStatic


local ERR_NOT_INSTANCE = "Cannot statically invoke method '%s' - It is an instance method. Call it on an instance of this class created via %s"
local ERR_INVALID_TYPE = "Invalid type for parameter '%s' (Expected %s, got %s)"
local FC_VIS_OBJ_NAME = "FastCastVisualizationObjects"
local ERR_OBJECT_DISPOSED = "This Caster has been disposed. It can no longer be used."
ActiveCastStatic.SetStaticFastCastReference(FastCast)
function FastCast.new()
	return setmetatable({
		LengthChanged = SignalStatic.new("LengthChanged"),
		RayHit = SignalStatic.new("RayHit"),
		RayPierced = SignalStatic.new("RayPierced"),
		CastTerminating = SignalStatic.new("CastTerminating"),
		WorldRoot = workspace
	}, FastCast)
end

function FastCast.newBehavior(): FastCastBehavior
	return {
		RaycastParams = nil,
		Acceleration = Vector3.new(),
		MaxDistance = 1000,
		CanPierceFunction = nil,
		HighFidelityBehavior = FastCast.HighFidelityBehavior.Default,
		HighFidelitySegmentSize = 0.5,
		CosmeticBulletTemplate = nil,
		CosmeticBulletProvider = nil,
		CosmeticBulletContainer = nil,
		AutoIgnoreContainer = true
	}
end

local DEFAULT_DATA_PACKET = FastCast.newBehavior()
function FastCast:Fire(origin: Vector3, direction: Vector3, velocity: Vector3 | number, castDataPacket: FastCastBehavior?): ActiveCast
	if castDataPacket == nil then castDataPacket = DEFAULT_DATA_PACKET end
	
	local cast = ActiveCastStatic.new(self, origin, direction, velocity, castDataPacket)
	cast.RayInfo.WorldRoot = self.WorldRoot
	return cast
end
return FastCast