--[[
	diag_shellyaw.luau -- measure the ACTUAL shell orientation on LIVE cars.

	Why this exists: the previous harness measured Wheel_* positions, which come
	from the constant Chassis.WHEEL_MOTOR/WHEELBASE_HALF (5.9). Those are
	identical for every car whether or not any fix applied, so the test passed
	vacuously. The visible "backwards" car is the COSMETIC SHELL, which is a
	separate model attached to the chassis -- that is what must be measured.

	Runs against the running game (Server datamodel), inspecting cars that the
	real spawn path actually produced. Reports, per live car:

	  bodyLook   : chassis Body forward (should be the car's true nose direction)
	  shellLook  : shell model forward
	  yawDelta   : signed angle between them, degrees. ~0 = aligned,
	               ~180 = shell rendering backwards relative to chassis.

	Also dumps the shell's own internal cue (mean Z of its F*/R* wheel labels)
	so we can see WHY the solver chose what it chose, and whether
	SHELL_YAW_OVERRIDE actually took effect on this car.
]]

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 function yawBetween(a: Vector3, b: Vector3): number
	local av = Vector3.new(a.X, 0, a.Z)
	local bv = Vector3.new(b.X, 0, b.Z)
	if av.Magnitude < 1e-4 or bv.Magnitude < 1e-4 then
		return 0 / 0
	end
	av, bv = av.Unit, bv.Unit
	local dot = math.clamp(av:Dot(bv), -1, 1)
	local ang = math.deg(math.acos(dot))
	local cross = av:Cross(bv).Y
	return (cross < 0) and -ang or ang
end

-- Find live cars anywhere in workspace (folder name varies).
local cars = {}
for _, d in ipairs(workspace:GetDescendants()) do
	if d:IsA("Model") and d.Name:match("^Car_") then
		cars[#cars + 1] = d
	end
end

log(string.format("live Car_* models found: %d", #cars))
if #cars == 0 then
	log("")
	log("No spawned cars. Drive/spawn a car, or this is the wrong datamodel.")
	return table.concat(out, "\n")
end

for _, model in ipairs(cars) do
	log("")
	log("=== " .. model.Name .. " ===")

	local body = model:FindFirstChild("Body")
	if not body or not body:IsA("BasePart") then
		log("  no Body part -- cannot establish chassis frame")
		continue
	end

	local bodyLook = body.CFrame.LookVector
	log(string.format("  bodyLook  = (%.2f, %.2f, %.2f)", bodyLook.X, bodyLook.Y, bodyLook.Z))

	-- The shell: a Model child that is not the chassis scaffolding.
	local shell = nil
	for _, c in ipairs(model:GetChildren()) do
		if c:IsA("Model") then
			shell = c
			break
		end
	end

	if not shell then
		log("  NO SHELL MODEL as a child -- cosmetic mesh may be parented elsewhere")
		local kids = {}
		for _, c in ipairs(model:GetChildren()) do
			kids[#kids + 1] = c.ClassName .. ":" .. c.Name
		end
		log("  children: " .. table.concat(kids, ", "))
		continue
	end

	local shellLook = shell:GetPivot().LookVector
	log(string.format("  shell     = %s", shell.Name))
	log(string.format("  shellLook = (%.2f, %.2f, %.2f)", shellLook.X, shellLook.Y, shellLook.Z))

	local delta = yawBetween(bodyLook, shellLook)
	log(
		string.format(
			"  yawDelta  = %.1f deg  --> %s",
			delta,
			(math.abs(delta) < 30) and "ALIGNED"
				or (math.abs(math.abs(delta) - 180) < 30) and "BACKWARDS (180 flip)"
				or "SKEWED"
		)
	)

	-- Why: the shell's own wheel-label cue, in the shell's local frame.
	local wf = shell:FindFirstChild("Wheels")
	if wf then
		local pivotInv = shell:GetPivot():Inverse()
		local fS, fN, rS, rN = 0, 0, 0, 0
		for _, d in ipairs(wf:GetDescendants()) do
			if d:IsA("BasePart") then
				local nm = d.Name:upper()
				local z = (pivotInv * d.CFrame).Z
				if nm:match("^F") then
					fS, fN = fS + z, fN + 1
				elseif nm:match("^R") then
					rS, rN = rS + z, rN + 1
				end
			end
		end
		if fN > 0 and rN > 0 then
			log(
				string.format(
					"  shell wheel cue: frontZ=%.2f rearZ=%.2f (labels say nose at %s)",
					fS / fN,
					rS / rN,
					(fS / fN < rS / rN) and "-Z" or "+Z"
				)
			)
		else
			log(string.format("  shell wheel cue: unusable (F parts=%d, R parts=%d)", fN, rN))
		end
	else
		log("  shell has no Wheels folder -- no cue available")
	end
end

return table.concat(out, "\n")