--[[
	diag_steer2.luau -- WHY does the steering servo not rotate?

	diag_steering showed TargetAngle -14..-26 deg with CurrentAngle stuck near
	0.3 deg. This isolates the cause by removing one load at a time:

	  A. HOISTED  -- body anchored, wheels in free air. No tyre load at all.
	                 If the servo still will not turn, the fault is the
	                 constraint itself, not grip.
	  B. GROUND, STATIC -- resting on the pad, no throttle.
	  C. GROUND, ROLLING -- coasting, no drive torque (drive is what saturates
	                 the friction circle).
	  D. TORQUE SWEEP -- is 1e6 actually enough?
]]

local ServerScriptService = game:GetService("ServerScriptService")
local ReplicatedStorage = game:GetService("ReplicatedStorage")
local RunService = game:GetService("RunService")

local out = {}
local function log(...)
	local parts = {}
	for i = 1, select("#", ...) do
		parts[#parts + 1] = tostring((select(i, ...)))
	end
	table.insert(out, table.concat(parts, " "))
end

local Shared = ReplicatedStorage:FindFirstChild("Shared")
local Cars = require(Shared.Cars)
local Chassis = require(Shared.Chassis)
local Server = ServerScriptService:FindFirstChild("Server", true)
local CarManager = require(Server.CarManager)

local pad = Instance.new("Part")
pad.Name = "DiagPad2"
pad.Size = Vector3.new(4000, 8, 4000)
pad.Position = Vector3.new(0, 5000, 0)
pad.Anchored = true
pad.Material = Enum.Material.Concrete
pad.Parent = workspace
local padTop = pad.Position.Y + 4

local car = Cars.Get("gtr_r34")
local tuning = Chassis.tuningFor(car)

local function build()
	local m = CarManager._buildForDiag(car, tuning)
	m.Parent = workspace
	m:PivotTo(CFrame.new(0, padTop + 3, 0))
	return m
end

local function partsOf(model)
	local servos, motors = {}, {}
	for _, d in ipairs(model:GetDescendants()) do
		if d:IsA("HingeConstraint") then
			if d.Name == Chassis.STEER_SERVO_NAME then
				table.insert(servos, d)
			elseif d.Name == Chassis.WHEEL_MOTOR_NAME then
				table.insert(motors, d)
			end
		end
	end
	return servos, motors
end

local LOCK = tuning.MaxSteerAngle
log(string.format("MaxSteerAngle %.1f deg | ServoMaxTorque 1e6 | AngularSpeed %.1f rad/s", LOCK, tuning.SteerSpeed))
log("")

-- Report the hinge axes once: a mis-set axis would make the servo yaw about
-- the wrong vector and look exactly like "no steering".
do
	local m = build()
	local servos = partsOf(m)
	for i, s in ipairs(servos) do
		local a0 = s.Attachment0
		local a1 = s.Attachment1
		log(
			string.format(
				"servo %d axis0 (%.2f,%.2f,%.2f) axis1 (%.2f,%.2f,%.2f) | A0 on %s, A1 on %s",
				i,
				a0.WorldAxis.X,
				a0.WorldAxis.Y,
				a0.WorldAxis.Z,
				a1.WorldAxis.X,
				a1.WorldAxis.Y,
				a1.WorldAxis.Z,
				a0.Parent.Name,
				a1.Parent.Name
			)
		)
	end
	m:Destroy()
	log("")
end

-- A. HOISTED ---------------------------------------------------------------
do
	local m = build()
	local body = m.PrimaryPart
	m:PivotTo(CFrame.new(0, padTop + 40, 0)) -- well clear of the pad
	body.Anchored = true
	local servos = partsOf(m)
	for _ = 1, 30 do
		RunService.Heartbeat:Wait()
	end
	for _, s in ipairs(servos) do
		s.TargetAngle = -LOCK
	end
	local trace = {}
	for step = 1, 120 do
		if step % 20 == 0 then
			table.insert(trace, string.format("%.1f", servos[1].CurrentAngle))
		end
		RunService.Heartbeat:Wait()
	end
	log(string.format("A. HOISTED (no tyre load): target %.1f -> CurrentAngle %s", -LOCK, table.concat(trace, ", ")))
	log(string.format("   final err %.2f deg", math.abs(servos[1].CurrentAngle - -LOCK)))
	m:Destroy()
end

-- B. GROUND, STATIC --------------------------------------------------------
do
	local m = build()
	local servos = partsOf(m)
	for _ = 1, 60 do
		RunService.Heartbeat:Wait()
	end
	for _, s in ipairs(servos) do
		s.TargetAngle = -LOCK
	end
	local trace = {}
	for step = 1, 120 do
		if step % 20 == 0 then
			table.insert(trace, string.format("%.1f", servos[1].CurrentAngle))
		end
		RunService.Heartbeat:Wait()
	end
	log(string.format("B. GROUND STATIC: target %.1f -> CurrentAngle %s", -LOCK, table.concat(trace, ", ")))
	log(string.format("   final err %.2f deg", math.abs(servos[1].CurrentAngle - -LOCK)))
	m:Destroy()
end

-- C. GROUND, COASTING (no drive torque) ------------------------------------
do
	local m = build()
	local body = m.PrimaryPart
	local servos, motors = partsOf(m)
	for _ = 1, 60 do
		RunService.Heartbeat:Wait()
	end
	-- Push to a moderate speed, then cut drive entirely and steer.
	body.AssemblyLinearVelocity = body.CFrame.LookVector * 60
	for _, mo in ipairs(motors) do
		mo.MotorMaxTorque = 0 -- freewheel: friction circle fully available for cornering
		mo.AngularVelocity = 0
	end
	for _, s in ipairs(servos) do
		s.TargetAngle = -LOCK
	end
	local trace, yawTrace = {}, {}
	for step = 1, 150 do
		if step % 30 == 0 then
			table.insert(trace, string.format("%.1f", servos[1].CurrentAngle))
			table.insert(yawTrace, string.format("%.3f", body.AssemblyAngularVelocity.Y))
		end
		RunService.Heartbeat:Wait()
	end
	log(string.format("C. GROUND COASTING @60: CurrentAngle %s", table.concat(trace, ", ")))
	log(string.format("   yawRate %s", table.concat(yawTrace, ", ")))
	m:Destroy()
end

-- D. TORQUE SWEEP (ground, static) -----------------------------------------
log("")
log("D. ServoMaxTorque sweep (ground, static, full lock, 1.5 s):")
for _, tq in ipairs({ 1e5, 1e6, 1e7, 1e8, 1e9 }) do
	local m = build()
	local servos = partsOf(m)
	for _ = 1, 45 do
		RunService.Heartbeat:Wait()
	end
	for _, s in ipairs(servos) do
		s.ServoMaxTorque = tq
		s.TargetAngle = -LOCK
	end
	for _ = 1, 90 do
		RunService.Heartbeat:Wait()
	end
	log(
		string.format(
			"   torque %10.0e -> CurrentAngle %6.1f (err %5.1f)",
			tq,
			servos[1].CurrentAngle,
			math.abs(servos[1].CurrentAngle + LOCK)
		)
	)
	m:Destroy()
end

pad:Destroy()
return table.concat(out, "\n")