-- Verify the linear slips against assertions that can FAIL.
-- Fixes the earlier harness bug: FindFirstChild must be RECURSIVE (PAFloor is
-- nested), otherwise `floor` is nil and every apron test vacuously reports
-- "does not reach" regardless of the real geometry.
local HttpService = game:GetService("HttpService")
local map = workspace:FindFirstChild("Map")
if not map then return "no Map -- run the rebuild first" end

local ramps = map:FindFirstChild("PARamps", true)
if not ramps then return "PARamps folder missing" end
local floor = map:FindFirstChild("PAFloor", true) -- RECURSIVE
if not floor then return "PAFloor missing" end

local fTop = floor.Position.Y + floor.Size.Y / 2
local fx0, fx1 = floor.Position.X - floor.Size.X / 2, floor.Position.X + floor.Size.X / 2
local fz0, fz1 = floor.Position.Z - floor.Size.Z / 2, floor.Position.Z + floor.Size.Z / 2

-- Collect deck segments per slip, ordered by their index suffix so we can find
-- the true LOW end rather than guessing from a bounding box.
local decks = { PAWestSlip = {}, PAEastSlip = {} }
local counts = {}
for _, d in ipairs(ramps:GetDescendants()) do
	if d:IsA("BasePart") then
		counts[d.Name:gsub("_%d+$", "")] = (counts[d.Name:gsub("_%d+$", "")] or 0) + 1
		for slipName, list in pairs(decks) do
			local idx = d.Name:match("^" .. slipName .. "_Deck_(%d+)$")
			if idx then
				table.insert(list, { i = tonumber(idx), p = d.Position, s = d.Size, cf = d.CFrame })
			end
		end
	end
end

local verdict, report = {}, {}
for slipName, list in pairs(decks) do
	table.sort(list, function(a, b) return a.i < b.i end)
	if #list < 50 then
		table.insert(verdict, slipName .. " FAIL: only " .. #list .. " deck segments")
	else
		local first, last = list[1], list[#list]
		local yTopFirst = first.p.Y + first.s.Y / 2
		local yTopLast = last.p.Y + last.s.Y / 2

		-- 1. Does the LOW end sit inside the apron footprint?
		local inX = last.p.X >= fx0 and last.p.X <= fx1
		local inZ = last.p.Z >= fz0 and last.p.Z <= fz1
		local lands = inX and inZ

		-- 2. Is the low end FLUSH with the apron surface? A lip catches cars.
		local lip = yTopLast - fTop

		-- 3. Is the high end flush with the mainline deck (Y 103)?
		local mouthErr = yTopFirst - 103

		-- 4. Peak grade over any single segment.
		local maxGrade = 0
		for k = 2, #list do
			local a, b = list[k - 1], list[k]
			local dy = math.abs((b.p.Y) - (a.p.Y))
			local dxz = (Vector3.new(b.p.X, 0, b.p.Z) - Vector3.new(a.p.X, 0, a.p.Z)).Magnitude
			if dxz > 0.5 then maxGrade = math.max(maxGrade, dy / dxz) end
		end

		report[slipName] = {
			segs = #list,
			mouth = { x = math.floor(first.p.X), z = math.floor(first.p.Z), yTop = math.floor(yTopFirst * 10) / 10 },
			landing = { x = math.floor(last.p.X), z = math.floor(last.p.Z), yTop = math.floor(yTopLast * 10) / 10 },
			landsInApron = lands,
			lipStuds = math.floor(lip * 100) / 100,
			mouthErrStuds = math.floor(mouthErr * 100) / 100,
			peakGradePct = math.floor(maxGrade * 1000) / 10,
		}

		if not lands then
			table.insert(verdict, ("%s FAIL: landing (%d,%d) outside apron x[%d..%d] z[%d..%d]")
				:format(slipName, last.p.X, last.p.Z, fx0, fx1, fz0, fz1))
		end
		if math.abs(lip) > 1.5 then
			table.insert(verdict, ("%s FAIL: %.2f stud lip at apron"):format(slipName, lip))
		end
		if math.abs(mouthErr) > 1.5 then
			table.insert(verdict, ("%s FAIL: %.2f stud step at mainline mouth"):format(slipName, mouthErr))
		end
		if maxGrade > 0.16 then
			table.insert(verdict, ("%s FAIL: peak grade %.1f%%"):format(slipName, maxGrade * 100))
		end
	end
end

-- 5. Does the mainline parapet actually open at each mouth? Count Barrier parts
-- within 160 studs of each mouth on the lot side; a sealed mouth = ramp is
-- decorative.
local road = map
local mouthBlocked = {}
for slipName, r in pairs(report) do
	local mp = Vector3.new(r.mouth.x, 103, r.mouth.z)
	local n = 0
	for _, d in ipairs(road:GetDescendants()) do
		if d:IsA("BasePart") and (d.Name == "Barrier" or d.Name == "Parapet") then
			if (Vector3.new(d.Position.X, 103, d.Position.Z) - mp).Magnitude < 150 then n += 1 end
		end
	end
	mouthBlocked[slipName] = n
end

return HttpService:JSONEncode({
	apron = { top = fTop, x = { math.floor(fx0), math.floor(fx1) }, z = { math.floor(fz0), math.floor(fz1) } },
	slips = report,
	partCounts = counts,
	barriersNearMouth = mouthBlocked,
	verdict = #verdict == 0 and "ALL PASS" or table.concat(verdict, " | "),
})