abms.lua

local function level_snow(pos, node, depth)

   local sides = {
   {x=pos.x - 1, y=pos.y, z=pos.z},
   {x=pos.x - 1, y=pos.y, z=pos.z + 1},
   {x=pos.x, y=pos.y, z=pos.z + 1},
   {x=pos.x + 1, y=pos.y, z=pos.z + 1},
   {x=pos.x + 1, y=pos.y, z=pos.z},
   {x=pos.x + 1, y=pos.y, z=pos.z - 1},
   {x=pos.x, y=pos.y, z=pos.z - 1},
   {x=pos.x - 1, y=pos.y, z=pos.z - 1},
   }
   local snow_level = {}
   snow_level["air"] = {"mymonths:snow_cover_1", 0}
   snow_level["default:snow"] = {"mymonths:snow_cover_3", 2}
   snow_level["mymonths:snow_cover_1"] = {"mymonths:snow_cover_2", 1}
   snow_level["mymonths:snow_cover_2"] = {"mymonths:snow_cover_3", 2}
   snow_level["mymonths:snow_cover_3"] = {"mymonths:snow_cover_4", 3}
   snow_level["mymonths:snow_cover_4"] = {"mymonths:snow_cover_5", 4}
   snow_level["mymonths:snow_cover_5"] = {"default:snowblock", 5}

   for i = 1,8 do
      local temp_node = minetest.get_node_or_nil(sides[i])
   -- check if node exsists and block is solid
      if temp_node ~= nil and snow_level[temp_node.name] ~= nil then
   -- check the difference in snow heights
         if snow_level[node.name][2] - snow_level[temp_node.name][2] > 2 then
   -- shift the node down till it can be filled
            if temp_node.name == "air" then
               while minetest.get_node_or_nil({x=sides[i].x, y=sides[i].y - 1, z=sides[i].z}) ~= nil and
               snow_level[minetest.get_node_or_nil({x=sides[i].x, y=sides[i].y - 1, z=sides[i].z}).name] ~= nil do
                  sides[i].y = sides[i].y - 1
               end
               if depth > 4 or level_snow(sides[i], temp_node, depth + 1) then
                  temp_node = minetest.get_node_or_nil(sides[i])
               end
            end
            minetest.set_node(sides[i], {name = snow_level[temp_node.name][1]})
            return false
         end
      end
   end
   return true
end

local function is_inside(pos)

   if minetest.get_node_light({x=pos.x,y=pos.y+1,z=pos.z}, 0.5) ~= 15 then
   return true
   end

   local temp_node = minetest.get_node_or_nil({x=pos.x,y=pos.y+1,z=pos.z})

   for i = 2,50 do
   if temp_node ~= nil and temp_node.name ~= "air" then
      return true
   end
   temp_node = minetest.get_node_or_nil({x=pos.x,y=pos.y+i,z=pos.z})
   end
      return false
end

local function get_melt_prob(pos)
   local list1 = minetest.find_nodes_in_area({x=pos.x-3,y=pos.y-2,z=pos.z-3},
   {x=pos.x+3,y=pos.y+1,z=pos.z+3},{"default:ice", "default:snowblock"})
   local list2 = minetest.find_nodes_in_area({x=pos.x-3,y=pos.y-2,z=pos.z-3},
   {x=pos.x+3,y=pos.y+1,z=pos.z+3},{"mymonths:snow_cover_5",
   "mymonths:snow_cover_4","mymonths:snow_cover_3","mymonths:snow_cover_2","mymonths:snow_cover_1"})
   local list3 = minetest.find_nodes_in_area({x=pos.x-3,y=pos.y-2,z=pos.z-3},
   {x=pos.x+3,y=pos.y+1,z=pos.z+3},{"default:dirt_with_snow", "default:pine_tree"})
   -- list1 is snow blocks and ice, list 2 is snow cover nodes, list3 is snow dirt and pine trees
   local count = 2.25 * table.getn(list1) + table.getn(list2) + 2 * table.getn(list3)
   local prob = 1 - count/196
   prob = math.max(tonumber(string.format("%.2f", prob * 10)), 0.01)
   prob = 1 / (prob / 200)
   prob = math.min(tonumber(string.format("%04d", prob)), 1000)
   return prob
end


--Places Snow on ground
if mymonths.snow_on_ground == true then

minetest.register_abm({
   nodenames = {"group:leaves", "group:soil", "default:snowblock"},
   neighbors = {"air"},
   interval = 8,
   chance = 20,

   action = function (pos, node)
      if mymonths.weather == "snow" or mymonths.weather == "snowstorm" then
         local biome_jungle = minetest.find_node_near(pos, 5, "default:jungletree", "default:junglegrass")
         pos.y = pos.y + 1 -- check above node
         local na = minetest.get_node(pos)
         if biome_jungle == nil then
            if not is_inside(pos) and na.name == "air" then
               minetest.set_node(pos, {name = "mymonths:snow_cover_1"})
            end
         end
      end
   end
})

--Replace grass and flowers with snow
minetest.register_abm({
   nodenames = {"group:flora", "mymonths:puddle", "group:plant"},
   neighbors = {"air"},
   interval = 8,
   chance = 20,

   action = function (pos, node)
   if mymonths.weather == "snow" or mymonths.weather == "snowstorm" then
      local biome_jungle = minetest.find_node_near(pos, 5, "default:jungletree","default:junglegrass")
      if biome_jungle == nil then
         if not is_inside(pos) then
            minetest.set_node(pos, {name="mymonths:snow_cover_1"})
         end
      end
   end
end
})

-- Changes snow to larger snow
minetest.register_abm({
   nodenames = {"mymonths:snow_cover_1", "mymonths:snow_cover_2", "mymonths:snow_cover_3", "mymonths:snow_cover_4", "mymonths:snow_cover_5", "default:snow"},
   neighbors = {"group:soil", "default:snowblock"},
   interval = 20,
   chance = 40,

   action = function (pos, node)
      if mymonths.weather2 == "snow" or mymonths.weather2 == "snowstorm" then
      if mymonths.weather2 == "snow" and math.random(1, 4) ~= 1 then
         return
      end
      if node.name == "mymonths:snow_cover_1" then
         minetest.set_node(pos, {name = "mymonths:snow_cover_2"})
      elseif node.name == "mymonths:snow_cover_2" or node.name == "default:snow" then
         minetest.set_node(pos, {name = "mymonths:snow_cover_3"})
      elseif node.name == "mymonths:snow_cover_3" then
         minetest.set_node(pos, {name = "mymonths:snow_cover_4"})
      elseif node.name == "mymonths:snow_cover_4" then
         minetest.set_node(pos, {name = "mymonths:snow_cover_5"})
      elseif node.name == "mymonths:snow_cover_5" then
         local depth = 2
         local snow_biome = minetest.find_node_near(pos, 5, {"default:ice"})

   -- checks the number of snow blocks below to determine if snow is too deep
         local count = 0
         for i = 1, depth do
            local new_pos_y = pos.y - i
            local temp_node = minetest.get_node_or_nil({x=pos.x, y=new_pos_y, z=pos.z})
            if temp_node ~= nil then
               if temp_node.name == "default:snowblock" then
                  count = count + 1
               end
            end
         end
         if level_snow(pos, node, 0) and (count ~= depth or snow_biome) then
            minetest.set_node(pos, {name = "default:snowblock"})
         end
      end
   end
end
})

-- Snow Melting
minetest.register_abm({
   nodenames = {"mymonths:snow_cover_1", "mymonths:snow_cover_2", "mymonths:snow_cover_3", "mymonths:snow_cover_4", "mymonths:snow_cover_5", "default:snowblock", "default:snow"},
   neighbors = {"air"},
   interval = 10,
   chance = 1,

   action = function (pos, node)

   if mymonths.month_counter == 12 or mymonths.month_counter == 1 or mymonths.month_counter == 2 then
      return
   end

   local melt_prob = get_melt_prob(pos)
   if melt_prob == 1000 then
      return
   end

   if math.random(1, melt_prob) == 1 then
   -- check if there is any blocks above it
      while minetest.get_node_or_nil({x=pos.x, y=pos.y + 1, z=pos.z}) and
      minetest.get_node_or_nil({x=pos.x, y=pos.y + 1, z=pos.z}).name ~= "air" do
         pos.y = pos.y + 1
         node = minetest.get_node_or_nil(pos)
      end

      if node.name == "mymonths:snow_cover_2" or node.name == "default:snow" then
         minetest.set_node(pos, {name = "mymonths:snow_cover_1"})
      elseif node.name == "mymonths:snow_cover_3" then
         minetest.set_node(pos, {name = "mymonths:snow_cover_2"})
      elseif node.name == "mymonths:snow_cover_4" then
         minetest.set_node(pos, {name = "mymonths:snow_cover_3"})
      elseif node.name == "mymonths:snow_cover_5" then
         minetest.set_node(pos, {name = "mymonths:snow_cover_4"})
      elseif node.name == "default:snowblock" then
         minetest.set_node(pos, {name = "mymonths:snow_cover_5"})
      elseif node.name == "mymonths:snow_cover_1" then
         local nu = minetest.get_node({x = pos.x, y = pos.y - 1, z = pos.z})
         if nu.name == "default:dirt_with_grass" or nu.name == "default:dirt" then
            minetest.set_node(pos, {name = "mymonths:puddle"})
         else
            minetest.remove_node(pos)
         end
      end
   end
end
})

end -- END IF

if mymonths.use_puddles == true then

-- Makes Puddles when raining
minetest.register_abm({
   nodenames = {"group:soil"},
   neighbors = {"default:air"},
   interval = 10,
   chance = 50,

   action = function (pos, node)

      if mymonths.weather == "rain" then

   -- return if puddle found nearby
         if minetest.find_node_near(pos, 20, "mymonths:puddle") then
            return
         end

      pos.y = pos.y + 1

   -- otherwise place puddle in empty space
      if minetest.get_node_light(pos, 0.5) == 15
      and minetest.get_node(pos).name == "air" then
         minetest.set_node(pos, {name = "mymonths:puddle"})
      end
   end
end
})

-- Makes puddles dry up when not raining
minetest.register_abm({
   nodenames = {"mymonths:puddle"},
   neighbors = {"air"},
   interval = 5,
   chance = 5,

   action = function (pos, node)
      if mymonths.weather == "clear" then
         minetest.remove_node(pos)
      elseif mymonths.weather == "snow"
      or mymonths.weather == "snowstorm" then
         minetest.set_node(pos, {name = "mymonths:snow_cover_1"})
      end
   end
})

end -- END IF