--[[
	diag_elevation.luau -- measure the vertical relationship between the wangan
	mainline and the Daikoku PA, so the "elevate the highway over the PA"
	rebuild can be designed from real numbers instead of guesses.

	Reports, for the stretch of mainline nearest the PA:
	  * the deck Y profile (is it flat? already climbing? in a tunnel?)
	  * which SIDE of the carriageway the PA sits on, per sample
	  * perpendicular distance from the mainline centreline to the PA centre
	  * terrain/ground height under the PA and under the mainline

	Read-only.
]]

local RS = game:GetService("ReplicatedStorage")
local Workspace = game:GetService("Workspace")
local Circuit = require(RS:WaitForChild("Shared"):WaitForChild("Circuit"))

local samples = Circuit.samples
local c = Circuit.PA_CENTER
local n = #samples

-- Nearest non-tunnel sample = where planPA anchors the junctions.
local bestIdx, bestD = 1, math.huge
for i, s in ipairs(samples) do
	local d = (Vector3.new(s.pos.X, 0, s.pos.Z) - Vector3.new(c.X, 0, c.Z)).Magnitude
	if not s.tunnel and d < bestD then
		bestIdx, bestD = i, d
	end
end

-- Ground probe: ray straight down, ignoring the built map so we hit terrain.
local map = Workspace:FindFirstChild("Map")
local rp = RaycastParams.new()
rp.FilterType = Enum.RaycastFilterType.Exclude
rp.FilterDescendantsInstances = map and { map } or {}

local function groundY(x, z, fromY)
	local hit = Workspace:Raycast(Vector3.new(x, fromY, z), Vector3.new(0, -4000, 0), rp)
	return hit and math.floor(hit.Position.Y * 10) / 10 or nil
end

local rows = {}
for k = -30, 30 do
	local i = ((bestIdx + k - 1) % n) + 1
	local s = samples[i]
	local nxt = samples[(i % n) + 1]
	local fwd = (nxt.pos - s.pos)
	fwd = Vector3.new(fwd.X, 0, fwd.Z)
	if fwd.Magnitude < 0.01 then
		continue
	end
	fwd = fwd.Unit
	local right = Vector3.new(-fwd.Z, 0, fwd.X)
	local toPA = Vector3.new(c.X - s.pos.X, 0, c.Z - s.pos.Z)
	table.insert(rows, {
		k = k,
		i = i,
		y = math.floor(s.pos.Y * 10) / 10,
		tun = s.tunnel and 1 or 0,
		-- +1 => PA is to the RIGHT of travel, -1 => LEFT
		side = (toPA.Unit:Dot(right) >= 0) and 1 or -1,
		-- signed perpendicular offset and along-track offset to the PA centre
		perp = math.floor(toPA:Dot(right)),
		along = math.floor(toPA:Dot(fwd)),
		dist = math.floor(toPA.Magnitude),
	})
end

local ys = {}
for _, r in ipairs(rows) do
	table.insert(ys, r.y)
end
table.sort(ys)

return game:GetService("HttpService"):JSONEncode({
	bestIdx = bestIdx,
	bestDist = math.floor(bestD),
	paY = c.Y,
	mainYmin = ys[1],
	mainYmax = ys[#ys],
	groundUnderPA = groundY(c.X, c.Z, c.Y + 500),
	groundUnderMain = groundY(samples[bestIdx].pos.X, samples[bestIdx].pos.Z, samples[bestIdx].pos.Y + 500),
	ringRadius = (require(RS.Shared.Circuit) and Circuit.PA_RADIUS + 130) or 0,
	rows = rows,
})