function riverdev_appletree(x, y, z, area, data)
	local c_tree = minetest.get_content_id("default:tree")
	local c_apple = minetest.get_content_id("default:apple")
	local c_appleleaf = minetest.get_content_id("riverdev:appleleaf")
	local top = 3 + math.random(2)
	for j = -2, top do
		if j == top - 1 or j == top then
			for k = -2, 2 do
				local vi = area:index(x - 2, y + j, z + k)
				local viu = area:index(x - 2, y + j - 1, z + k)
				for i = -2, 2 do
					if math.random() < 0.8 then
						data[vi] = c_appleleaf
						if j == top and math.random() < 0.04 then
							data[viu] = c_apple
						end
					end
					vi = vi + 1
					viu = viu + 1
				end
			end
		elseif j == top - 2 then
			for k = -1, 1 do
				local vi = area:index(x - 1, y + j, z + k)
				for i = -1, 1 do
					if math.abs(i) + math.abs(k) == 2 then
						data[vi] = c_tree
					end
					vi = vi + 1
				end
			end
		else
			local vi = area:index(x, y + j, z)
			data[vi] = c_tree
		end
	end
end

function riverdev_pinetree(x, y, z, area, data)
	local c_pinetree = minetest.get_content_id("riverdev:pinetree")
	local c_needles = minetest.get_content_id("riverdev:needles")
	for j = -4, 14 do
		if j == 3 or j == 6 or j == 9 or j == 12 then
			for k = -2, 2 do
				local vi = area:index(x - 2, y + j, z + k)
				for i = -2, 2 do
					if math.abs(i) == 2 or math.abs(k) == 2 then
						data[vi] = c_needles
					end
					vi = vi + 1
				end
			end
		elseif j == 4 or j == 7 or j == 10 then
			for k = -1, 1 do
				local vi = area:index(x - 1, y + j, z + k)
				for i = -1, 1 do
					if not (i == 0 and j == 0) then
						data[vi] = c_needles
					end
					vi = vi + 1
				end
			end
		elseif j == 13 then
			for k = -1, 1 do
				local vi = area:index(x - 1, y + j, z + k)
				local via = area:index(x - 1, y + j + 1, z + k)
				for i = -1, 1 do
					if not (i == 0 and j == 0) then
						data[vi] = c_needles
						data[via] = c_needles
					end
					vi = vi + 1
					via = via + 1
				end
			end
		end
		local vi = area:index(x, y + j, z)
		data[vi] = c_pinetree
	end
	local vi = area:index(x, y + 15, z)
	local via = area:index(x, y + 16, z)
	data[vi] = c_needles
	data[via] = c_needles
end

function riverdev_flower(data, vi)
	local c_danwhi = minetest.get_content_id("flowers:dandelion_white")
	local c_danyel = minetest.get_content_id("flowers:dandelion_yellow")
	local c_rose = minetest.get_content_id("flowers:rose")
	local c_tulip = minetest.get_content_id("flowers:tulip")
	local c_geranium = minetest.get_content_id("flowers:geranium")
	local c_viola = minetest.get_content_id("flowers:viola")
	local rand = math.random(6)
	if rand == 1 then
		data[vi] = c_danwhi
	elseif rand == 2 then
		data[vi] = c_rose
	elseif rand == 3 then
		data[vi] = c_tulip
	elseif rand == 4 then
		data[vi] = c_danyel
	elseif rand == 5 then
		data[vi] = c_geranium
	else
		data[vi] = c_viola
	end
end

-- ABM

-- Appletree sapling

minetest.register_abm({
	nodenames = {"riverdev:appling"},
	interval = 31,
	chance = 5,
	action = function(pos, node)
		local x = pos.x
		local y = pos.y
		local z = pos.z
		local vm = minetest.get_voxel_manip()
		local pos1 = {x=x-2, y=y-2, z=z-2}
		local pos2 = {x=x+2, y=y+5, z=z+2}
		local emin, emax = vm:read_from_map(pos1, pos2)
		local area = VoxelArea:new({MinEdge=emin, MaxEdge=emax})
		local data = vm:get_data()

		riverdev_appletree(x, y, z, area, data)

		vm:set_data(data)
		vm:write_to_map()
		vm:update_map()
	end,
})

-- Pinetree sapling

minetest.register_abm({
	nodenames = {"riverdev:pineling"},
	interval = 29,
	chance = 5,
	action = function(pos, node)
		local x = pos.x
		local y = pos.y
		local z = pos.z
		local vm = minetest.get_voxel_manip()
		local pos1 = {x=x-2, y=y-4, z=z-2}
		local pos2 = {x=x+2, y=y+16, z=z+2}
		local emin, emax = vm:read_from_map(pos1, pos2)
		local area = VoxelArea:new({MinEdge=emin, MaxEdge=emax})
		local data = vm:get_data()

		riverdev_pinetree(x, y, z, area, data)

		vm:set_data(data)
		vm:write_to_map()
		vm:update_map()
	end,
})

-- Set mapgen parameters

minetest.register_on_mapgen_init(function(mgparams)
	minetest.set_mapgen_params({mgname="singlenode"})
end)

-- Spawn player. Only works with chunksize = 5 mapblocks

function spawnplayer(player)
	local PSCA = 16 -- Player scatter. Maximum distance in chunks (80 nodes) of player spawn from (0, 0, 0)
	local YWATER = 1
	local YTER = -64 -- Deepest seabed y
	local TERSCA = 512 -- Terrain vertical scale in nodes
	local BASAMP = 0.3 -- Base amplitude relative to 3D noise amplitude. Ridge network structure
	local MIDAMP = 0.05 -- Mid amplitude relative to 3D noise amplitude. River valley structure

	local np_terrain = {
		offset = 0,
		scale = 1,
		spread = {x=192, y=192, z=192},
		seed = 5900033,
		octaves = 4,
		persist = 0.67
	}
	local np_mid = {
		offset = 0,
		scale = 1,
		spread = {x=768, y=768, z=768},
		seed = 85546,
		octaves = 5,
		persist = 0.4
	}
	local np_base = {
		offset = 0,
		scale = 1,
		spread = {x=3072, y=3072, z=3072},
		seed = -990054,
		octaves = 2,
		persist = 0.4
	}
	local np_patha = {
		offset = 0,
		scale = 1,
		spread = {x=768, y=768, z=768},
		seed = 7000023,
		octaves = 4,
		persist = 0.4
	}
	local np_pathb = {
		offset = 0,
		scale = 1,
		spread = {x=768, y=768, z=768},
		seed = 23,
		octaves = 4,
		persist = 0.4
	}

	local xsp
	local ysp
	local zsp
	for chunk = 1, 128 do
		print ("[riverdev] searching for spawn "..chunk)
		local x0 = 80 * math.random(-PSCA, PSCA) - 32
		local z0 = 80 * math.random(-PSCA, PSCA) - 32
		local y0 = 80 * math.floor((YWATER + 32) / 80) - 32
		local x1 = x0 + 79
		local z1 = z0 + 79
		local y1 = y0 + 79

		local sidelen = 80
		local chulensxyz = {x=sidelen, y=sidelen, z=sidelen}
		local minposxyz = {x=x0, y=y0, z=z0}
		local chulensxz = {x=sidelen, y=sidelen, z=sidelen}
		local minposxz = {x=x0, y=z0}
	
		local nvals_terrain = minetest.get_perlin_map(np_terrain, chulensxyz):get3dMap_flat(minposxyz)

		local nvals_mid = minetest.get_perlin_map(np_mid, chulensxz):get2dMap_flat(minposxz)
		local nvals_base = minetest.get_perlin_map(np_base, chulensxz):get2dMap_flat(minposxz)
		local nvals_patha = minetest.get_perlin_map(np_patha, chulensxz):get2dMap_flat(minposxz)
		local nvals_pathb = minetest.get_perlin_map(np_pathb, chulensxz):get2dMap_flat(minposxz)

		local nixyz = 1
		local nixz = 1
		for z = z0, z1 do
			for y = y0, y1 do
				for x = x0, x1 do
					local n_patha = nvals_patha[nixz]
					local n_abspatha = math.abs(n_patha)
					local n_pathb = nvals_pathb[nixz]
					local n_abspathb = math.abs(n_pathb)

					local n_terrain = (nvals_terrain[nixyz] + 2) / 2
					local n_absmid = (math.abs(nvals_mid[nixz])) ^ 0.8
					local n_absbase = (math.abs(nvals_base[nixz])) ^ 0.8
			
					local n_invbase = (1 - n_absbase)
					local grad = (YTER - y) / TERSCA
					local densitybase = n_invbase * BASAMP + grad
					local densitymid = n_absmid * MIDAMP + densitybase
					local density = n_terrain * n_invbase * n_absmid * n_abspatha ^ 1.5 * n_abspathb ^ 1.5 + densitymid

					if y >= YWATER and density > -0.01 and density < 0 then
						ysp = y + 1
						xsp = x
						zsp = z
						break
					end
					nixz = nixz + 1
					nixyz = nixyz + 1
				end
				if ysp then
					break
				end
				nixz = nixz - 80
			end
			if ysp then
				break
			end
			nixz = nixz + 80
		end
		if ysp then
			break
		end
	end
	if ysp then
		print ("[riverdev] spawn player ("..xsp.." "..ysp.." "..zsp..")")
		player:setpos({x=xsp, y=ysp, z=zsp})
	else	
		print ("[riverdev] no suitable spawn found")
		player:setpos({x=0, y=0, z=0})
	end
end

minetest.register_on_newplayer(function(player)
	spawnplayer(player)
end)

minetest.register_on_respawnplayer(function(player)
	spawnplayer(player)
	return true
end)