-- Two questions, measured rather than eyeballed:
--   (1) WHERE exactly is the mainline missing barriers? Walk the deck edge and
--       report contiguous runs with no Barrier/EdgeRail within reach.
--       (User deleted ~106 parts by hand, so gaps are wherever they cut.)
--   (2) HOW does the south on-ramp differ from the north off-ramp? Compare the
--       two slips feature-by-feature so "make it look like the other" is a
--       concrete list of deltas, not a guess.
local out = {}
local function say(s) table.insert(out, s) end

local map = workspace:FindFirstChild("Map")
if not map then return "Map MISSING" end

-- Collect barrier-ish parts into a coarse spatial hash for fast lookup.
local CELL = 60
local grid = {}
local function key(x, z) return math.floor(x / CELL) .. ":" .. math.floor(z / CELL) end
local barrierCount = 0
for _, d in ipairs(map:GetDescendants()) do
	if d:IsA("BasePart") and (d.Name == "Barrier" or d.Name == "EdgeRail") then
		barrierCount += 1
		local k = key(d.Position.X, d.Position.Z)
		grid[k] = grid[k] or {}
		table.insert(grid[k], d)
	end
end
say(("indexed %d Barrier/EdgeRail parts"):format(barrierCount))

local function nearestBarrier(p)
	local best = math.huge
	local cx, cz = math.floor(p.X / CELL), math.floor(p.Z / CELL)
	for dx = -1, 1 do
		for dz = -1, 1 do
			local c = grid[(cx + dx) .. ":" .. (cz + dz)]
			if c then
				for _, b in ipairs(c) do
					local d2 = (Vector3.new(b.Position.X, 0, b.Position.Z) - Vector3.new(p.X, 0, p.Z)).Magnitude
					-- only count barriers at roughly this height
					if math.abs(b.Position.Y - p.Y) < 14 and d2 < best then best = d2 end
				end
			end
		end
	end
	return best
end

-- Walk the mainline deck parts to build an ordered centreline.
local deck = {}
for _, d in ipairs(map:GetDescendants()) do
	if d:IsA("BasePart") then
		local k = d.Name:match("^Road_(%d+)$") or d.Name:match("^Deck_(%d+)$")
			or d.Name:match("^RoadDeck_(%d+)$")
		if k then table.insert(deck, { i = tonumber(k), p = d.Position, cf = d.CFrame, sz = d.Size }) end
	end
end
table.sort(deck, function(a, b) return a.i < b.i end)
say(("mainline deck parts found: %d"):format(#deck))

if #deck > 0 then
	local UP = Vector3.new(0, 1, 0)
	local runs = {}
	local cur = nil
	for j, s in ipairs(deck) do
		local fwd = s.cf.LookVector
		local right = fwd:Cross(UP).Unit
		local half = s.sz.X / 2
		-- probe just outboard of each edge
		local gapL = nearestBarrier(s.p - right * (half + 2)) > 12
		local gapR = nearestBarrier(s.p + right * (half + 2)) > 12
		local bad = gapL or gapR
		if bad then
			local side = (gapL and gapR) and "BOTH" or (gapL and "L" or "R")
			if cur and cur.side == side and s.i - cur.last <= 2 then
				cur.last = s.i; cur.n += 1
			else
				if cur then table.insert(runs, cur) end
				cur = { first = s.i, last = s.i, n = 1, side = side, pos = s.p }
			end
		else
			if cur then table.insert(runs, cur); cur = nil end
		end
	end
	if cur then table.insert(runs, cur) end

	table.sort(runs, function(a, b) return a.n > b.n end)
	say(("UNBARRIERED RUNS: %d total"):format(#runs))
	for j = 1, math.min(#runs, 14) do
		local r = runs[j]
		say(("  samples %d..%d (%d) side=%s at (%.0f,%.0f,%.0f)"):format(
			r.first, r.last, r.n, r.side, r.pos.X, r.pos.Y, r.pos.Z))
	end
end

-- (2) Compare the two slips.
say("--- SLIP COMPARISON ---")
for _, s in ipairs({ "PAWestSlip", "PAEastSlip" }) do
	local segs, walls, lines, other = {}, 0, 0, {}
	for _, d in ipairs(map:GetDescendants()) do
		if d:IsA("BasePart") and d.Name:match("^" .. s) then
			local k = d.Name:match("^" .. s .. "_Deck_(%d+)$")
			if k then
				table.insert(segs, { i = tonumber(k), p = d.Position, sz = d.Size, cf = d.CFrame })
			elseif d.Name:match("_Wall_") then walls += 1
			elseif d.Name:match("[Ll]ine") then lines += 1
			else
				local nm = d.Name:gsub("^" .. s .. "_", ""):gsub("_%d+$", "")
				other[nm] = (other[nm] or 0) + 1
			end
		end
	end
	table.sort(segs, function(a, b) return a.i < b.i end)
	local ol = {}
	for k, v in pairs(other) do table.insert(ol, k .. "=" .. v) end
	table.sort(ol)
	if #segs > 0 then
		-- heading of first and last segment: which way does it run?
		local h1 = segs[1].cf.LookVector
		local hN = segs[#segs].cf.LookVector
		-- curvature: total heading change
		local turn = 0
		for j = 2, #segs do
			local a = segs[j - 1].cf.LookVector
			local b = segs[j].cf.LookVector
			turn += math.deg(math.acos(math.clamp(a:Dot(b), -1, 1)))
		end
		say(("%s: segs=%d walls=%d lines=%d  startY=%.1f endY=%.1f"):format(s, #segs, walls, lines, segs[1].p.Y, segs[#segs].p.Y))
		say(("   heading first=(%.2f,%.2f) last=(%.2f,%.2f) totalTurn=%.1fdeg"):format(h1.X, h1.Z, hN.X, hN.Z, turn))
		say(("   start=(%.0f,%.0f,%.0f) end=(%.0f,%.0f,%.0f)"):format(
			segs[1].p.X, segs[1].p.Y, segs[1].p.Z, segs[#segs].p.X, segs[#segs].p.Y, segs[#segs].p.Z))
		say("   other parts: " .. (#ol > 0 and table.concat(ol, " ") or "none"))
	end
end

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