Make farming more flexible

- API {farming.register_hoe(), farming.register_plant()}
- Fertilities -> Plant only grow on soil with a fitting fertility, e.g. Wheat only grows on grassland, while cotton grows in deserts and grassland)
- New soil: Desert Sand
- Place seeds instead of plants

mods/farming/nodes.lua

@@ -0,0 +1,139 @@
+minetest.override_item("default:dirt", {
+	groups = {crumbly=3,soil=1},
+	soil = {
+		base = "default:dirt",
+		dry = "farming:soil",
+		wet = "farming:soil_wet"
+	}
+})
+
+minetest.override_item("default:dirt_with_grass", {
+	groups = {crumbly=3,soil=1},
+	soil = {
+		base = "default:dirt_with_grass",
+		dry = "farming:soil",
+		wet = "farming:soil_wet"
+	}
+})
+
+minetest.register_node("farming:soil", {
+	description = "Soil",
+	tiles = {"farming_soil.png", "default_dirt.png"},
+	drop = "default:dirt",
+	is_ground_content = true,
+	groups = {crumbly=3, not_in_creative_inventory=1, soil=2, grassland = 1},
+	sounds = default.node_sound_dirt_defaults(),
+	soil = {
+		base = "default:dirt",
+		dry = "farming:soil",
+		wet = "farming:soil_wet"
+	}
+})
+
+minetest.register_node("farming:soil_wet", {
+	description = "Wet Soil",
+	tiles = {"farming_soil_wet.png", "farming_soil_wet_side.png"},
+	drop = "default:dirt",
+	is_ground_content = true,
+	groups = {crumbly=3, not_in_creative_inventory=1, soil=3, wet = 1, grassland = 1},
+	sounds = default.node_sound_dirt_defaults(),
+	soil = {
+		base = "default:dirt",
+		dry = "farming:soil",
+		wet = "farming:soil_wet"
+	}
+})
+
+minetest.override_item("default:desert_sand", {
+	groups = {crumbly=3, falling_node=1, sand=1, soil = 1},
+	soil = {
+		base = "default:desert_sand",
+		dry = "farming:desert_sand_soil",
+		wet = "farming:desert_sand_soil_wet"
+	}
+})
+minetest.register_node("farming:desert_sand_soil", {
+	description = "Desert Sand",
+	tiles = {"farming_desert_sand_soil.png", "default_desert_sand.png"},
+	is_ground_content = true,
+	groups = {crumbly=3, not_in_creative_inventory = 1, falling_node=1, sand=1, soil = 2, desert = 1},
+	sounds = default.node_sound_sand_defaults(),
+	soil = {
+		base = "default:desert_sand",
+		dry = "farming:desert_sand_soil",
+		wet = "farming:desert_sand_soil_wet"
+	}
+})
+
+minetest.register_node("farming:desert_sand_soil_wet", {
+	description = "Desert Sand",
+	drop = "default:desert_sand",
+	tiles = {"farming_desert_sand_soil_wet.png", "farming_desert_sand_soil_wet_side.png"},
+	is_ground_content = true,
+	groups = {crumbly=3, falling_node=1, sand=1, not_in_creative_inventory=1, soil=3, wet = 1, desert = 1},
+	sounds = default.node_sound_sand_defaults(),
+	soil = {
+		base = "default:desert_sand",
+		dry = "farming:desert_sand_soil",
+		wet = "farming:desert_sand_soil_wet"
+	}
+})
+
+minetest.register_abm({
+	nodenames = {"group:soil", "group:wet"},
+	interval = 5,
+	chance = 10,
+	action = function(pos, node)
+		pos.y = pos.y+1
+		local nn = minetest.get_node(pos).name
+		node = minetest.registered_nodes[node.name]
+		pos.y = pos.y-1
+		
+		if node.soil == nil or node.soil.wet == nil or node.soil.base == nil or node.soil.dry == nil then
+			minetest.log("error", "Could not process soil information of node " .. nn)
+			return
+		end
+		
+		if minetest.registered_nodes[nn] and minetest.registered_nodes[nn].walkable and minetest.get_item_group(nn, "plant") == 0 and node.name ~= node.soil.base then
+			minetest.set_node(pos, {name = node.soil.base})
+		end
+		-- check if there is water nearby
+		if minetest.find_node_near(pos, 3, {"group:water"}) then
+			-- if it is dry soil and not base node, turn it into wet soil
+			if node.name ~= node.soil.base and minetest.get_item_group(node.name, "wet") == 0 then
+				minetest.set_node(pos, {name = node.soil.wet})
+			end
+		else
+			-- turn it back into base if it is already dry
+			if minetest.get_item_group(node.name, "wet") == 0 then
+				-- only turn it back if there is no plant/seed on top of it
+				if minetest.get_item_group(nn, "plant") == 0 and minetest.get_item_group(nn, "seed") == 0 then
+					minetest.set_node(pos, {name = node.soil.base})
+				end
+				
+			-- if its wet turn it back into dry soil
+			elseif minetest.get_item_group(node.name, "wet") == 1 then
+				minetest.set_node(pos, {name = node.soil.dry})
+			end
+		end
+	end,
+})
+
+
+for i = 1, 5 do		
+	minetest.override_item("default:grass_"..i, {drop = {
+		max_items = 1,
+		items = {
+			{items = {'farming:seed_wheat'},rarity = 5},
+			{items = {'default:grass_1'}},
+		}
+	}})
+end
+	
+minetest.override_item("default:junglegrass", {drop = {
+	max_items = 1,
+	items = {
+		{items = {'farming:seed_cotton'},rarity = 8},
+		{items = {'default:junglegrass'}},
+	}
+}})