TheDarkProject/mods/MAPGEN/mcl_surface_pools/init.lua

local adjacents = {
	vector.new(1,0,0),
	vector.new(1,0,1),
	vector.new(1,0,-1),
	vector.new(-1,0,0),
	vector.new(-1,0,1),
	vector.new(-1,0,-1),
	vector.new(0,0,1),
	vector.new(0,0,-1),
	vector.new(0,-1,0)
}

local function set_node_no_bedrock(pos,node)
	local n = minetest.get_node(pos)
	if n.name == "mcl_core:bedrock" then return end
	return minetest.set_node(pos,node)
end

local function airtower(pos)
	for i=0,55 do
		set_node_no_bedrock(vector.offset(pos,0,i,0),{name="air"})
	end
end

local function makelake(pos,size,liquid,border,pr)
	local node_under = minetest.get_node(vector.offset(pos,0,1,0))
	local p1 = vector.offset(pos,-size,-size,-size)
	local p2 = vector.offset(pos,size,size,size)
	local nn = minetest.find_nodes_in_area(p1,p2,{"group:material_stone", "group:sand", "group:dirt"})
	table.sort(nn,function(a, b)
		   return vector.distance(pos, a) < vector.distance(pos, b)
	end)
	if not nn[1] then return end
	local y = pos.y + 1
	local lq = {}
	for i=1,pr:next(1,#nn) do
		if nn[i].y == y then
			set_node_no_bedrock(nn[i],{name=liquid})
			airtower(vector.offset(nn[i],0,1,0))
			table.insert(lq,nn[i])
		end
	end

	for k,v in pairs(lq) do
		for kk,vv in pairs(adjacents) do
			local pp = vector.add(v,vv)
			local an = minetest.get_node(pp)
			local un = minetest.get_node(vector.offset(pp,0,1,0))
			if not border then
				if minetest.get_item_group(an.name,"solid") > 0 then
					border = an.name
				elseif minetest.get_item_group(minetest.get_node(nn[1]).name,"solid") > 0 then
					border = minetest.get_node(nn[1]).name
				else
					border = "mcl_core:stone"
				end
				if border == "mcl_core:dirt" then border = "mcl_core:dirt_with_grass" end
			end
			if an.name ~= liquid then
				set_node_no_bedrock(pp,{name=border})
				if un.name ~= liquid then
					airtower(vector.offset(pp,0,1,0))
				end
			end
		end
	end
	return true
end

mcl_structures.register_structure("lavapool",{
	place_on = {"group:sand", "group:dirt", "group:stone"},
	noise_params = {
		offset = 0,
		scale = 0.0000022,
		spread = {x = 250, y = 250, z = 250},
		seed = 78375213,
		octaves = 3,
		persist = 0.001,
		flags = "absvalue",
	},
	flags = "place_center_x, place_center_z, force_placement",
	y_max = mcl_vars.mg_overworld_max,
	y_min = minetest.get_mapgen_setting("water_level"),
	place_func = function(pos,def,pr)
		return makelake(pos,5,"mcl_core:lava_source","mcl_core:stone",pr)
	end
})

mcl_structures.register_structure("water_lake",{
	place_on = {"group:dirt","group:stone"},
	noise_params = {
		offset = 0,
		scale = 0.000032,
		spread = {x = 250, y = 250, z = 250},
		seed = 734341353,
		octaves = 3,
		persist = 0.001,
		flags = "absvalue",
	},
	flags = "place_center_x, place_center_z, force_placement",
	y_max = mcl_vars.mg_overworld_max,
	y_min = minetest.get_mapgen_setting("water_level"),
	place_func = function(pos,def,pr)
		return makelake(pos,5,"mcl_core:water_source",nil,pr)
	end
})