-- Verification v2: corrected geometric metrics.
--
-- v1 had two badly-written assertions (the CODE was fine, the TEST was wrong):
--   * seam lip used Position.Y + Size.Y/2, but decks are pitched by
--     CFrame.lookAt(mid, mid+dir, UP), so that is the centre height, not the
--     surface height at the seam. On a sloped segment it over-reports badly.
--     Correct: evaluate each deck's TOP SURFACE at the shared sample point.
--   * pier offset measured distance to the nearest sample, but piers sit at
--     segment MIDPOINTS and samples are 60 studs apart -- so ~30.0 is the
--     correct answer for a perfectly centred pier. Correct: perpendicular
--     distance to the centreline polyline.
local sss = game:GetService("ServerScriptService")
local orig = sss:FindFirstChild("MapBuilder", true)
local clone = orig:Clone()
clone.Name = "MapBuilder_Verify2"
clone.Parent = orig.Parent
local okM, MB = pcall(require, clone)
if not okM then
	clone:Destroy()
	return "FAIL require: " .. tostring(MB)
end
local okB, map = pcall(MB.build)
if not okB then
	clone:Destroy()
	return "FAIL build: " .. tostring(map)
end

local Circuit = require(game:GetService("ReplicatedStorage"):FindFirstChild("Circuit", true))
local samples = Circuit.samples
local n = #samples

local decks = {}
for _, d in ipairs(map:GetDescendants()) do
	if d:IsA("BasePart") then
		local idx = d.Name:match("^Road_(%d+)$")
		if idx then
			decks[tonumber(idx)] = d
		end
	end
end

local out = {}
local function line(s)
	out[#out + 1] = s
end

-- TRUE SEAM LIP -------------------------------------------------------------
-- Deck i spans local z in [-Size.Z/2, +Size.Z/2] and is 2 studs longer than
-- its segment (deliberate overlap), so the shared sample point sits at
-- local z = +(Size.Z - 2)/2 for deck i and -(Size.Z - 2)/2 for deck i+1.
local worst, worstAt = 0, -1
local lips = {}
for i = 1, n do
	local j = (i % n) + 1
	local a, b = decks[i], decks[j]
	if a and b then
		local ta = (a.CFrame * CFrame.new(0, a.Size.Y / 2, (a.Size.Z - 2) / 2)).Y
		local tb = (b.CFrame * CFrame.new(0, b.Size.Y / 2, -(b.Size.Z - 2) / 2)).Y
		local lip = math.abs(ta - tb)
		lips[#lips + 1] = { lip, i }
		if lip > worst then
			worst, worstAt = lip, i
		end
	end
end
table.sort(lips, function(p, q)
	return p[1] > q[1]
end)
local top = {}
for k = 1, math.min(5, #lips) do
	top[#top + 1] = ("i=%d:%.4f(%s)"):format(lips[k][2], lips[k][1], samples[lips[k][2]].piece)
end
line(("SEAM true max lip=%.4f at i=%d -> %s"):format(worst, worstAt, worst <= 0.30 and "PASS" or "FAIL"))
line("SEAM top5: " .. table.concat(top, " "))

-- Deck-width continuity: the taper must not jump more than a few studs
-- between neighbours, or the widening would look like a step in the road.
local maxJump, jumpAt = 0, -1
for i = 1, n do
	local j = (i % n) + 1
	if decks[i] and decks[j] then
		local dw = math.abs(decks[i].Size.X - decks[j].Size.X)
		if dw > maxJump then
			maxJump, jumpAt = dw, i
		end
	end
end
line(("TAPER max width step=%.2f studs at i=%d -> %s"):format(maxJump, jumpAt, maxJump <= 6 and "PASS" or "FAIL"))

-- PIER LATERAL OFFSET -------------------------------------------------------
-- Perpendicular distance from each pier to the centreline polyline (XZ).
local function segDist(p, u, v)
	local pu = Vector3.new(p.X - u.X, 0, p.Z - u.Z)
	local uv = Vector3.new(v.X - u.X, 0, v.Z - u.Z)
	local L2 = uv:Dot(uv)
	if L2 < 1e-6 then
		return pu.Magnitude
	end
	local t = math.clamp(pu:Dot(uv) / L2, 0, 1)
	return (pu - uv * t).Magnitude
end

local worstPier, nPier = 0, 0
for _, d in ipairs(map:GetDescendants()) do
	if d.Name == "OverpassPier" then
		nPier += 1
		local best = math.huge
		for i = 1, n do
			local j = (i % n) + 1
			best = math.min(best, segDist(d.Position, samples[i].pos, samples[j].pos))
		end
		worstPier = math.max(worstPier, best)
	end
end
line(
	("PIER lateral offset from centreline: n=%d worst=%.3f studs -> %s"):format(
		nPier,
		worstPier,
		(nPier > 0 and worstPier < 3) and "PASS" or "FAIL"
	)
)

-- Girders must hang BELOW their deck, never poke through the driving surface.
local bad, nG = 0, 0
for _, d in ipairs(map:GetDescendants()) do
	if d.Name == "BridgeGirder" then
		nG += 1
		local topY = d.Position.Y + d.Size.Y / 2
		local best, bi = math.huge, nil
		for i = 1, n do
			local dd = (Vector3.new(samples[i].pos.X, 0, samples[i].pos.Z) - Vector3.new(d.Position.X, 0, d.Position.Z)).Magnitude
			if dd < best then
				best, bi = dd, i
			end
		end
		if bi and decks[bi] then
			local deckBottom = decks[bi].Position.Y - decks[bi].Size.Y / 2
			if topY > deckBottom + 0.6 then
				bad += 1
			end
		end
	end
end
line(("GIRDER below deck: n=%d intruding=%d -> %s"):format(nG, bad, bad == 0 and "PASS" or "FAIL"))

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