output.txt

x__ Air
x__ Air
x__ Air
x__ Air
_x_ Grass
__x Rock
__x Rock
__x Rock
__x Rock
__x Rock
-----

WaveCollapseUtils1d.lua

---
-- @module WaveCollapseUtils
-- @author Quenty

local WaveCollapseUtils = {}

local EDGE_DATA = {
	{
		2, -- Edge index (forward)
		1, -- Neighbor's  edgeindex (backward)
		1, -- Number to add to index to get to neighbor
	},
	{
		1,
		2,
		-1,
	},
}

local MODULE_INDEX_TO_NAME = {
	[1] = "Air";
	[2] = "Grass";
	[3] = "Rock";
}

function WaveCollapseUtils.update(cells, index)
	local cell = cells[index]

	local toUpdate = {}

	for _, edgeData in pairs(EDGE_DATA) do
		local thisEdgeIndex = edgeData[1]
		local neighborEdgeIndex = edgeData[2]

		local validHashes = {}
		for _, _module in pairs(cell) do
			validHashes[_module[thisEdgeIndex]] = true
		end

		local neighborIndex = index + edgeData[3]
		local neighbor = cells[neighborIndex]
		if neighbor then
			local removed = false
			for moduleIndex, _module in pairs(neighbor) do
				if not validHashes[_module[neighborEdgeIndex]] then
					neighbor[moduleIndex] = nil
					removed = true
				end
			end

			if removed then
				table.insert(toUpdate, neighborIndex)
			end
		end
	end

	for _, cellIndex in pairs(toUpdate) do
		WaveCollapseUtils.update(cells, cellIndex)
	end
end

function WaveCollapseUtils.visualize(cells)
	for i=1, #cells do
		local cell = cells[i]
		local line = ""
		local cellNames = {}
		for j=1, #MODULE_INDEX_TO_NAME do
			if cell[j] then
				line = line .. "x"
				table.insert(cellNames, MODULE_INDEX_TO_NAME[j])
			else
				line = line .. "_"
			end
		end
		line = line .. " " .. table.concat(cellNames, ", ")
		print(line)
	end
	print("-----")
end


local function air()
	return {
		0; -- first edge (above)
		0; -- second edge (below)
	}
end

local function rock()
	return {
		1;
		1;
	}
end

local function grass()
	return {
		0;
		1;
	}
end

-- Creates a cell
local function cellMaker()
	return {
		air();
		grass();
		rock();
	}
end

local cells = {}
for _=1, 10 do
	table.insert(cells, cellMaker())
end

cells[5][1] = nil -- remove air from 5th cell
cells[5][3] = nil -- remove rock from 5th cell
WaveCollapseUtils.update(cells, 5) -- update 5th cell recursively
WaveCollapseUtils.visualize(cells)