random_messages/signs.lua

local modname = minetest.get_current_modname()
	
-- Height limits to place the signs
local h_min = random_messages.options.signs.h_min or -200
local h_max = random_messages.options.signs.h_max or 200
local signs_per_chunk = random_messages.options.signs.signs_per_chunk or 1


	-- Register cubic sign node if no yard sign
if minetest.get_modpath("default") 
 and minetest.get_modpath("signs_lib") == nil
 and minetest.get_modpath("signs") == nil 	
 then
	local defsign = minetest.registered_nodes["default:sign_wall_wood"]
	local y_on_construct, y_on_receive_fields, y_sounds, y_groups
	if defsign then	
		y_on_construct = defsign.on_construct
		y_on_receive_fields = defsign.on_receive_fields
		y_sound = defsign.sound
		y_groups = defsign.groups
	end	
	
	-- New Yard Sign
	minetest.register_node(modname..":sign_yard", {
		paramtype = "light",
		sunlight_propagates = true,
		paramtype2 = "facedir",
		drawtype = "nodebox",
		node_box = {
			type = "fixed",
			fixed = {
					{-0.4375, -0.25, -0.0625, 0.4375, 0.375, 0},
					{-0.0625, -0.5, -0.0625, 0.0625, -0.1875, 0},
			}
		},
		selection_box = {
			type = "fixed",
			fixed = {-0.4375, -0.5, -0.0625, 0.4375, 0.375, 0}
		},
		tiles = {"rm_signs_top.png", "rm_signs_bottom.png", "rm_signs_side.png", "rm_signs_side.png", "rm_signs_back.png", "rm_signs_front.png"},
		inventory_image = "rm_signs_front.png",
		wield_image = "rm_signs_front.png",
		groups = y_groups or {choppy = 2, attached_node = 1, flammable = 2, oddly_breakable_by_hand = 3},
		sound = y_sound,
		on_construct = y_on_construct,
		on_receive_fields = y_on_receive_fields,
	})
	
	-- Recipe
	minetest.register_craft({
		output = modname..':sign_yard',
		recipe = {
			{'default:sign_wall_wood'},
			{'group:stick'},
		}
	})
	
	minetest.register_alias(":signs:sign_yard", modname..':sign_yard')
end


minetest.register_on_generated(function(minp, maxp, seed)
		
	-- How many chances signs haves to appear in this chunk
	local chances = random_messages.options.signs.chance_of_signs_in_chunk
	-- Ensure chances is a number 
	if type(chances) ~= "number" then chances = 1
	-- If number is higher than one, it is a fraction of 1
	elseif chances > 1 then	chances = 1/chances end
	-- Convert to a percentage
	local cpc = math.floor(chances * 100)
	-- Pick a random number between 1 and 100
	-- Return if number picked is higher than chance percent
	if ( math.random(0,100) > cpc ) then return end
			

	-- Most of the following code was adapted from tsm_chests_exemple 
		
	-- Get the water level and convert it to a number
	local water_level = minetest.setting_get("water_level")
	if water_level == nil or type(water_level) ~= "number" then
		water_level = 1
	else
		water_level = tonumber(water_level)
	end

	-- signs minimum and maximum spawn height
	local height_min = water_level + h_min 
	local height_max = water_level + h_max

	if(maxp.y < height_min or minp.y > height_max) then
		return
	end	
	local y_min = math.max(minp.y, height_min)
	local y_max = math.min(maxp.y, height_max)
	for i=1, signs_per_chunk do
		local pos = {x=math.random(minp.x,maxp.x),z=math.random(minp.z,maxp.z), y=minp.y}

		 -- Find ground level (look for air or liquid above something else)
		local ground = nil
		local top = y_max	
		local top_node = minetest.get_node({x=pos.x,y=y_max,z=pos.z})
		if top_node.name ~= "air" and minetest.get_node_group(top_node.name, "liquid") < 1 then
			for y=y_max,y_min,-1 do
				local p = {x=pos.x,y=y,z=pos.z}
				if minetest.get_node(p).name == "air" or minetest.get_node_group(minetest.get_node(p).name, "liquid") > 0 then
					top = y
					break
				end
			end
		end
		for y=top,y_min,-1 do
			local p = {x=pos.x,y=y,z=pos.z}
			if minetest.get_node(p).name ~= "air" and minetest.get_node_group(top_node.name, "liquid") < 1 then
				ground = y
				break
			end
		end
		
		if(ground~=nil) then
			local sign_pos = {x=pos.x,y=ground+1, z=pos.z}
			local nn = minetest.get_node(sign_pos).name	-- sign node name (before it becomes a sign)

			-- Return if node isn't air
			 if nn ~= "air" then return end
		
			-- Replace plants and other buildable to nodes instead of placing on it
			local under = minetest.get_node({x=pos.x, y=ground, z=pos.z}).name
			local under_def = minetest.registered_nodes[under] 
			if under_def and under_def.buildable_to then
				ground = ground - 1
				sign_pos = {x=pos.x,y=ground+1, z=pos.z}
				nn = minetest.get_node(sign_pos).name
			end
			
			-- Return if building in water
			if minetest.get_node_group(nn, "liquid") > 1 then return end
			
			-- Define message to display
			local message_number = table.random(random_messages.messages)
			local msg = random_messages.messages[message_number] or message_number
			if msg then
				-- Define the rest of the sign
				local sign = {}
				-- -- Name0
				if minetest.registered_nodes["signs:sign_yard"] then
					sign.name = "signs:sign_yard"		
				else sign.name = modname..":sign_yard"	
				end
				-- -- Facedir
				-- find possible faces
				local xp, xm, zp, zm
				xp = minetest.get_node({x=pos.x+1,y=ground+1, z=pos.z})
				xm = minetest.get_node({x=pos.x-1,y=ground+1, z=pos.z})
				zp = minetest.get_node({x=pos.x,y=ground+1, z=pos.z+1})
				zm = minetest.get_node({x=pos.x,y=ground+1, z=pos.z-1})

				local facedirs = {}
				if(xp.name=="air" or xp.name=="default:water_source") then
					table.insert(facedirs, minetest.dir_to_facedir({x=-1,y=0,z=0}))
				end
				if(xm.name=="air" or xm.name=="default:water_source") then
					table.insert(facedirs, minetest.dir_to_facedir({x=1,y=0,z=0}))
				end
				if(zp.name=="air" or zp.name=="default:water_source") then
					table.insert(facedirs, minetest.dir_to_facedir({x=0,y=0,z=-1}))
				end
				if(zm.name=="air" or zm.name=="default:water_source") then
					table.insert(facedirs, minetest.dir_to_facedir({x=0,y=0,z=1}))
				end
						
				-- choose a random face (if possible)
				if(#facedirs == 0) then
					minetest.set_node({x=pos.x,y=ground+1, z=pos.z+1},{name=nn})
					sign.param2 = minetest.dir_to_facedir({x=0,y=0,z=1})
				else
					sign.param2 = facedirs[math.floor(math.random(#facedirs))]
				end
								
				-- Lastly: place the sign
				minetest.set_node(sign_pos,sign)
				local meta = minetest.get_meta(sign_pos)
				meta:set_string("text",msg)
				meta:set_string("infotext",msg) 
			end
		end	
	end		
end)