-- Which side of the deck does each slip + aux lane sit on?
-- Answers: are both existing slips on the SAME carriageway (so "the opposite"
-- means the other carriageway), or is one an entry and one an exit?
local ws = game:GetService("Workspace")
local RS = game:GetService("ReplicatedStorage")
local Circuit = require(RS:WaitForChild("Shared"):WaitForChild("Circuit"))

local map = ws:FindFirstChild("Map")
if not map then return "NOMAP" end
local samples = Circuit.samples
local out = {}
local function say(s) table.insert(out, s) end

-- Signed lateral offset of a world point from the mainline at sample i.
-- Positive = one side, negative = the other. Uses the deck's own right vector.
local function sideOf(i, p)
	local n = #samples
	local a = samples[((i - 1) % n) + 1]
	local b = samples[(i % n) + 1]
	local fwd = (b.pos - a.pos)
	fwd = Vector3.new(fwd.X, 0, fwd.Z).Unit
	local right = Vector3.new(-fwd.Z, 0, fwd.X)
	local rel = Vector3.new(p.X - a.pos.X, 0, p.Z - a.pos.Z)
	return rel:Dot(right)
end

local SLIPS = { { "PAWestSlip", 525, 537 }, { "PAEastSlip", 551, 539 } }
for _, s in ipairs(SLIPS) do
	local name, join, land = s[1], s[2], s[3]
	local first, last, nseg = nil, nil, 0
	local maxI = -1
	for _, d in ipairs(map:GetDescendants()) do
		if d:IsA("BasePart") then
			local k = tonumber(d.Name:match("^" .. name .. "_Deck_(%d+)$") or "")
			if k then
				nseg += 1
				if k <= 1 then first = d end
				if k > maxI then maxI, last = k, d end
			end
		end
	end
	if not first then
		say(name .. ": FAIL no deck parts")
	else
		local lat = sideOf(join, first.Position)
		say(("%s: segs=%d  mouth lateral %+.1f (%s side)  mouthY=%.1f landY=%.1f  -> %s")
			:format(name, nseg, lat, lat > 0 and "RIGHT" or "LEFT",
				first.Position.Y, last and last.Position.Y or -1,
				(last and last.Position.Y < first.Position.Y) and "DESCENDS (exit/off-ramp)"
					or "CLIMBS (entry/on-ramp)"))
	end
end

-- Aux lanes: which side, grouped by contiguous sample index.
local aux = {}
for _, d in ipairs(map:GetDescendants()) do
	if d:IsA("BasePart") then
		local ai = tonumber(d.Name:match("^AuxLane_(%d+)$") or "")
		if ai then table.insert(aux, { i = ai, p = d.Position }) end
	end
end
table.sort(aux, function(x, y) return x.i < y.i end)
if #aux == 0 then
	say("AUX: FAIL none built")
else
	local groups, cur = {}, { aux[1] }
	for k = 2, #aux do
		if aux[k].i - aux[k - 1].i > 3 then
			table.insert(groups, cur); cur = {}
		end
		table.insert(cur, aux[k])
	end
	table.insert(groups, cur)
	for gi, g in ipairs(groups) do
		local mid = g[math.max(1, math.floor(#g / 2))]
		local lat = sideOf(mid.i, mid.p)
		say(("AUX group %d: samples %d..%d (%d segs) lateral %+.1f (%s side)")
			:format(gi, g[1].i, g[#g].i, #g, lat, lat > 0 and "RIGHT" or "LEFT"))
	end
end

-- Does the deck carry traffic both ways, and is there a median?
local med = 0
for _, d in ipairs(map:GetDescendants()) do
	if d:IsA("BasePart") and d.Name:match("^Median") then med += 1 end
end
say(("median parts: %d  (deck is one slab split into two carriageways)"):format(med))
return table.concat(out, "\n")