-- Biome library mod by VanessaE
--
-- I got the temperature map idea from "hmmmm", values used for it came from
-- Splizard's snow mod.
--

-- Various settings - most of these probably won't need to be changed

biome_lib = {}
biome_lib.air = {name = "air"}

biome_lib.block_log = {}

biome_lib.actionslist_aircheck = {}
biome_lib.actionslist_no_aircheck = {}

biome_lib.surfaceslist_aircheck = {}
biome_lib.surfaceslist_no_aircheck = {}

biome_lib.modpath = minetest.get_modpath("biome_lib")

local function tableize(s)
    return string.split(string.trim(string.gsub(s, " ", "")))
end

local c1 = minetest.settings:get("biome_lib_default_grow_through_nodes")
biome_lib.default_grow_through_nodes = {["air"] = true}
if c1 then
    for _, i in ipairs(tableize(c1)) do
        biome_lib.default_grow_through_nodes[i] = true
    end
else
    biome_lib.default_grow_through_nodes["default:snow"] = true
end

local c2 = minetest.settings:get("biome_lib_default_water_nodes")
biome_lib.default_water_nodes = {}
if c2 then
    for _, i in ipairs(tableize(c2)) do
        biome_lib.default_water_nodes[i] = true
    end
else
    biome_lib.default_water_nodes["default:water_source"] = true
    biome_lib.default_water_nodes["default:water_flowing"] = true
    biome_lib.default_water_nodes["default:river_water_source"] = true
    biome_lib.default_water_nodes["default:river_water_flowing"] = true
end

local c3 = minetest.settings:get("biome_lib_default_wet_surfaces")
local c4 = minetest.settings:get("biome_lib_default_ground_nodes")
local c5 = minetest.settings:get("biome_lib_default_grow_nodes")

biome_lib.default_wet_surfaces = c3 and tableize(c3) or {"default:dirt", "default:dirt_with_grass", "default:sand"}
biome_lib.default_ground_nodes = c4 and tableize(c4) or {"default:dirt_with_grass"}
biome_lib.default_grow_nodes =   c5 and tableize(c5) or {"default:dirt_with_grass"}

-- Boilerplate to support localized strings if intllib mod is installed.
local S
if minetest.global_exists("intllib") then
    if intllib.make_gettext_pair then
        S = intllib.make_gettext_pair()
    else
        S = intllib.Getter()
    end
else
    S = function(s) return s end
end
biome_lib.intllib = S

local DEBUG = minetest.settings:get_bool("biome_lib_debug", false)

function biome_lib:dbg(msg)
    if DEBUG then
        print("[Biome Lib] "..msg)
        minetest.log("verbose", "[Biome Lib] "..msg)
    end
end

biome_lib.plantlife_seed_diff = 329 -- needs to be global so other mods can see it

local perlin_octaves = 3
local perlin_persistence = 0.6
local perlin_scale = 100

local temperature_seeddiff = 112
local temperature_octaves = 3
local temperature_persistence = 0.5
local temperature_scale = 150

local humidity_seeddiff = 9130
local humidity_octaves = 3
local humidity_persistence = 0.5
local humidity_scale = 250

local time_scale = 1
local time_speed = tonumber(minetest.settings:get("time_speed"))

if time_speed and time_speed > 0 then
    time_scale = 72 / time_speed
end

--PerlinNoise(seed, octaves, persistence, scale)

biome_lib.perlin_temperature = PerlinNoise(temperature_seeddiff, temperature_octaves, temperature_persistence, temperature_scale)
biome_lib.perlin_humidity = PerlinNoise(humidity_seeddiff, humidity_octaves, humidity_persistence, humidity_scale)

-- Local functions

local function get_biome_data(pos, perlin_fertile)
    local fertility = perlin_fertile:get_2d({x=pos.x, y=pos.z})

    if type(minetest.get_biome_data) == "function" then
        local data = minetest.get_biome_data(pos)
        if data then
            return fertility, data.heat / 100, data.humidity / 100
        end
    end

    local temperature = biome_lib.perlin_temperature:get2d({x=pos.x, y=pos.z})
    local humidity = biome_lib.perlin_humidity:get2d({x=pos.x+150, y=pos.z+50})

    return fertility, temperature, humidity
end

function biome_lib:is_node_loaded(node_pos)
    local n = minetest.get_node_or_nil(node_pos)
    if (not n) or (n.name == "ignore") then
        return false
    end
    return true
end

function biome_lib:set_defaults(biome)
    biome.seed_diff = biome.seed_diff or 0
    biome.min_elevation = biome.min_elevation or -31000
    biome.max_elevation = biome.max_elevation or 31000
    biome.temp_min = biome.temp_min or 1
    biome.temp_max = biome.temp_max or -1
    biome.humidity_min = biome.humidity_min or 1
    biome.humidity_max = biome.humidity_max or -1
    biome.plantlife_limit = biome.plantlife_limit or 0.1
    biome.near_nodes_vertical = biome.near_nodes_vertical or 1

-- specific to on-generate

    biome.neighbors = biome.neighbors or biome.surface
    biome.near_nodes_size = biome.near_nodes_size or 0
    biome.near_nodes_count = biome.near_nodes_count or 1
    biome.rarity = biome.rarity or 50
    biome.max_count = biome.max_count or 125
    if biome.check_air ~= false then biome.check_air = true end

-- specific to abm spawner
    biome.seed_diff = biome.seed_diff or 0
    biome.light_min = biome.light_min or 0
    biome.light_max = biome.light_max or 15
    biome.depth_max = biome.depth_max or 1
    biome.facedir = biome.facedir or 0
end

local function search_table(t, s)
    for i = 1, #t do
        if t[i] == s then return true end
    end
    return false
end

-- register the list of surfaces to spawn stuff on, filtering out all duplicates.
-- separate the items by air-checking or non-air-checking map eval methods

function biome_lib:register_generate_plant(biomedef, nodes_or_function_or_model)

    -- if calling code passes an undefined node for a surface or
    -- as a node to be spawned, don't register an action for it.

    if type(nodes_or_function_or_model) == "string"
      and string.find(nodes_or_function_or_model, ":")
      and not minetest.registered_nodes[nodes_or_function_or_model] then
        biome_lib:dbg("Warning: Ignored registration for undefined spawn node: "..dump(nodes_or_function_or_model))
        return
    end

    if type(nodes_or_function_or_model) == "string"
      and not string.find(nodes_or_function_or_model, ":") then
        biome_lib:dbg("Warning: Registered function call using deprecated string method: "..dump(nodes_or_function_or_model))
    end

    if biomedef.check_air == false then
        biome_lib:dbg("Register no-air-check mapgen hook: "..dump(nodes_or_function_or_model))
        biome_lib.actionslist_no_aircheck[#biome_lib.actionslist_no_aircheck + 1] = { biomedef, nodes_or_function_or_model }
        local s = biomedef.surface
        if type(s) == "string" then
            if s and (string.find(s, "^group:") or minetest.registered_nodes[s]) then
                if not search_table(biome_lib.surfaceslist_no_aircheck, s) then
                    biome_lib.surfaceslist_no_aircheck[#biome_lib.surfaceslist_no_aircheck + 1] = s
                end
            else
                biome_lib:dbg("Warning: Ignored no-air-check registration for undefined surface node: "..dump(s))
            end
        else
            for i = 1, #biomedef.surface do
                local s = biomedef.surface[i]
                if s and (string.find(s, "^group:") or minetest.registered_nodes[s]) then
                    if not search_table(biome_lib.surfaceslist_no_aircheck, s) then
                        biome_lib.surfaceslist_no_aircheck[#biome_lib.surfaceslist_no_aircheck + 1] = s
                    end
                else
                    biome_lib:dbg("Warning: Ignored no-air-check registration for undefined surface node: "..dump(s))
                end
            end
        end
    else
        biome_lib:dbg("Register with-air-checking mapgen hook: "..dump(nodes_or_function_or_model))
        biome_lib.actionslist_aircheck[#biome_lib.actionslist_aircheck + 1] = { biomedef, nodes_or_function_or_model }
        local s = biomedef.surface
        if type(s) == "string" then
            if s and (string.find(s, "^group:") or minetest.registered_nodes[s]) then
                if not search_table(biome_lib.surfaceslist_aircheck, s) then
                    biome_lib.surfaceslist_aircheck[#biome_lib.surfaceslist_aircheck + 1] = s
                end
            else
                biome_lib:dbg("Warning: Ignored with-air-checking registration for undefined surface node: "..dump(s))
            end
        else
            for i = 1, #biomedef.surface do
                local s = biomedef.surface[i]
                if s and (string.find(s, "^group:") or minetest.registered_nodes[s]) then
                    if not search_table(biome_lib.surfaceslist_aircheck, s) then
                        biome_lib.surfaceslist_aircheck[#biome_lib.surfaceslist_aircheck + 1] = s
                    end
                else
                    biome_lib:dbg("Warning: Ignored with-air-checking registration for undefined surface node: "..dump(s))
                end
            end
        end
    end
end

-- Function to check whether a position matches the given biome definition
-- Returns true when the surface can be populated

local function populate_single_surface(biome, pos, perlin_fertile_area, checkair)
    local p_top = { x = pos.x, y = pos.y + 1, z = pos.z }

    if math.random(1, 100) <= biome.rarity then
        return
    end

    local fertility, temperature, humidity = get_biome_data(pos, perlin_fertile_area)

    local pos_biome_ok = pos.y >= biome.min_elevation and pos.y <= biome.max_elevation
        and fertility > biome.plantlife_limit
        and temperature <= biome.temp_min and temperature >= biome.temp_max
        and humidity <= biome.humidity_min and humidity >= biome.humidity_max

    if not pos_biome_ok then
        return -- Y position mismatch, outside of biome
    end

    local biome_surfaces_string = dump(biome.surface)
    local surface_ok = false

    if not biome.depth then
        local dest_node = minetest.get_node(pos)
        if string.find(biome_surfaces_string, dest_node.name) then
            surface_ok = true
        else
            if string.find(biome_surfaces_string, "group:") then
                for j = 1, #biome.surface do
                    if string.find(biome.surface[j], "^group:")
                      and minetest.get_item_group(dest_node.name, biome.surface[j]) then
                        surface_ok = true
                        break
                    end
                end
            end
        end
    elseif not string.find(biome_surfaces_string,
            minetest.get_node({ x = pos.x, y = pos.y-biome.depth-1, z = pos.z }).name) then
        surface_ok = true
    end

    if not surface_ok then
        return -- Surface does not match the given node group/name
    end

    if checkair and minetest.get_node(p_top).name ~= "air" then
        return
    end

    if biome.below_nodes and
            not string.find(dump(biome.below_nodes),
                minetest.get_node({x=pos.x, y=pos.y-1, z=pos.z}).name
            ) then
        return -- Node below does not match
    end

    if biome.ncount and
            #minetest.find_nodes_in_area(
                {x=pos.x-1, y=pos.y, z=pos.z-1},
                {x=pos.x+1, y=pos.y, z=pos.z+1},
                biome.neighbors
            ) <= biome.ncount then
        return -- Not enough similar biome nodes around
    end

    if biome.near_nodes and
            #minetest.find_nodes_in_area(
                {x=pos.x-biome.near_nodes_size, y=pos.y-biome.near_nodes_vertical, z=pos.z-biome.near_nodes_size},
                {x=pos.x+biome.near_nodes_size, y=pos.y+biome.near_nodes_vertical, z=pos.z+biome.near_nodes_size},
                biome.near_nodes
            ) < biome.near_nodes_count then
        return -- Long distance neighbours do not match
    end

    -- Position fits into given biome
    return true
end

function biome_lib.populate_surfaces(biome, nodes_or_function_or_model, snodes, checkair)
    local items_added = 0

    biome_lib:set_defaults(biome)

    -- filter stage 1 - find nodes from the supplied surfaces that are within the current biome.

    local in_biome_nodes = {}
    local perlin_fertile_area = minetest.get_perlin(biome.seed_diff, perlin_octaves, perlin_persistence, perlin_scale)

    for i = 1, #snodes do
        local pos = vector.new(snodes[i])
        if populate_single_surface(biome, pos, perlin_fertile_area, checkair) then
            in_biome_nodes[#in_biome_nodes + 1] = pos
        end
    end

    -- filter stage 2 - find places within that biome area to place the plants.

    local num_in_biome_nodes = #in_biome_nodes

    if num_in_biome_nodes == 0 then
        return 0
    end

    for i = 1, math.min(math.ceil(biome.max_count/25), num_in_biome_nodes) do
        local tries = 0
        local spawned = false
        while tries < 2 and not spawned do
            local pos = in_biome_nodes[math.random(1, num_in_biome_nodes)]
            if biome.spawn_replace_node then
                pos.y = pos.y-1
            end
            local p_top = { x = pos.x, y = pos.y + 1, z = pos.z }

            if not (biome.avoid_nodes and biome.avoid_radius
                    and minetest.find_node_near(p_top, biome.avoid_radius
                    + math.random(-1.5,2), biome.avoid_nodes)) then
                if biome.delete_above then
                    minetest.swap_node(p_top, biome_lib.air)
                    minetest.swap_node({x=p_top.x, y=p_top.y+1, z=p_top.z}, biome_lib.air)
                end

                if biome.delete_above_surround then
                    minetest.swap_node({x=p_top.x-1, y=p_top.y, z=p_top.z}, biome_lib.air)
                    minetest.swap_node({x=p_top.x+1, y=p_top.y, z=p_top.z}, biome_lib.air)
                    minetest.swap_node({x=p_top.x,   y=p_top.y, z=p_top.z-1}, biome_lib.air)
                    minetest.swap_node({x=p_top.x,   y=p_top.y, z=p_top.z+1}, biome_lib.air)

                    minetest.swap_node({x=p_top.x-1, y=p_top.y+1, z=p_top.z}, biome_lib.air)
                    minetest.swap_node({x=p_top.x+1, y=p_top.y+1, z=p_top.z}, biome_lib.air)
                    minetest.swap_node({x=p_top.x,   y=p_top.y+1, z=p_top.z-1}, biome_lib.air)
                    minetest.swap_node({x=p_top.x,   y=p_top.y+1, z=p_top.z+1}, biome_lib.air)
                end

                if biome.spawn_replace_node then
                    minetest.swap_node(pos, biome_lib.air)
                end

                local objtype = type(nodes_or_function_or_model)

                if objtype == "table" then
                    if nodes_or_function_or_model.axiom then
                        biome_lib:generate_tree(p_top, nodes_or_function_or_model)
                        biome_lib:dbg("An L-tree was spawned at "..minetest.pos_to_string(p_top))
                        spawned = true
                    else
                        local fdir = nil
                        if biome.random_facedir then
                            fdir = math.random(biome.random_facedir[1], biome.random_facedir[2])
                        end
                        local n=nodes_or_function_or_model[math.random(#nodes_or_function_or_model)]
                        minetest.swap_node(p_top, { name = n, param2 = fdir })
                        biome_lib:dbg("Node \""..n.."\" was randomly picked from a list and placed at "..minetest.pos_to_string(p_top))
                        spawned = true
                    end
                elseif objtype == "string" and
                  minetest.registered_nodes[nodes_or_function_or_model] then
                    local fdir = nil
                    if biome.random_facedir then
                        fdir = math.random(biome.random_facedir[1], biome.random_facedir[2])
                    end
                    minetest.swap_node(p_top, { name = nodes_or_function_or_model, param2 = fdir })
                    biome_lib:dbg("Node \""..nodes_or_function_or_model.."\" was placed at "..minetest.pos_to_string(p_top))
                    spawned = true
                elseif objtype == "function" then
                    nodes_or_function_or_model(pos)
                    biome_lib:dbg("A function was run on surface node at "..minetest.pos_to_string(pos))
                    spawned = true
                elseif objtype == "string" and pcall(loadstring(("return %s(...)"):
                    format(nodes_or_function_or_model)),pos) then
                    spawned = true
                    biome_lib:dbg("An obsolete string-specified function was run on surface node at "..minetest.pos_to_string(p_top))
                else
                    biome_lib:dbg("Warning: Ignored invalid definition for object "..dump(nodes_or_function_or_model).." that was pointed at {"..dump(pos).."}")
                end
            else
                tries = tries + 1
            end
        end
        if spawned then items_added = items_added + 1 end
    end
    return items_added
end

-- Primary log read-out/mapgen spawner

local function confirm_block_surroundings(p)
    local n=minetest.get_node_or_nil(p)
    if not n or n.name == "ignore" then return false end

    for x = -32,32,64 do -- step of 64 causes it to only check the 8 corner blocks
        for y = -32,32,64 do
            for z = -32,32,64 do
                local pos = {x=p.x + x, y=p.y + y, z=p.z + z}
                local n=minetest.get_node_or_nil(pos)
                if not n or n.name == "ignore" then return false end
            end
        end
    end
    return true
end

function biome_lib.generate_block(shutting_down)
    if not biome_lib.block_log[1] then return end -- the block log is empty

    local minp =        biome_lib.block_log[1][1]
    local maxp =        biome_lib.block_log[1][2]
    local airflag =     biome_lib.block_log[1][3]
    local pos_hash =    minetest.hash_node_position(minp)

    if not biome_lib.pos_hash then -- we need to read the maplock and get the surfaces list
        biome_lib.pos_hash = {}
        if not confirm_block_surroundings(minp) and not shutting_down then -- if any neighbors appear not to be loaded, move this block to the end of the queue
            biome_lib.block_log[#biome_lib.block_log + 1] = biome_lib.block_log[1]
            table.remove(biome_lib.block_log, 1)
            biome_lib.pos_hash = nil
                biome_lib:dbg("Mapblock at "..minetest.pos_to_string(minp)..
                    " had a neighbor not fully emerged, moved it to the end of the queue.")
            return
        else
            biome_lib.pos_hash.surface_node_list = airflag
                and minetest.find_nodes_in_area_under_air(minp, maxp, biome_lib.surfaceslist_aircheck)
                or minetest.find_nodes_in_area(minp, maxp, biome_lib.surfaceslist_no_aircheck)
            biome_lib.pos_hash.action_index = 1
            if #biome_lib.pos_hash.surface_node_list > 0 then
                biome_lib:dbg("Mapblock at "..minetest.pos_to_string(minp)..
                    " has "..#biome_lib.pos_hash.surface_node_list..
                    " surface nodes to work on (airflag="..dump(airflag)..")")
            end
        end
    elseif not (airflag and biome_lib.actionslist_aircheck[biome_lib.pos_hash.action_index])
      and not (not airflag and biome_lib.actionslist_no_aircheck[biome_lib.pos_hash.action_index]) then
        -- the block is finished, remove it
        if #biome_lib.pos_hash.surface_node_list > 0 then
            biome_lib:dbg("Deleted mapblock "..minetest.pos_to_string(minp).." from the block log")
        end
        table.remove(biome_lib.block_log, 1)
        biome_lib.pos_hash = nil
    else
        -- below, [1] is biome, [2] is the thing to be added
        local added = 0
        if airflag then
            if biome_lib.actionslist_aircheck[biome_lib.pos_hash.action_index] then
                added = biome_lib.populate_surfaces(
                            biome_lib.actionslist_aircheck[biome_lib.pos_hash.action_index][1],
                            biome_lib.actionslist_aircheck[biome_lib.pos_hash.action_index][2],
                            biome_lib.pos_hash.surface_node_list, true)
                biome_lib.pos_hash.action_index = biome_lib.pos_hash.action_index + 1
            end
        else
            if biome_lib.actionslist_no_aircheck[biome_lib.pos_hash.action_index] then
                added = biome_lib.populate_surfaces(
                            biome_lib.actionslist_no_aircheck[biome_lib.pos_hash.action_index][1],
                            biome_lib.actionslist_no_aircheck[biome_lib.pos_hash.action_index][2],
                            biome_lib.pos_hash.surface_node_list, false)
                biome_lib.pos_hash.action_index = biome_lib.pos_hash.action_index + 1
            end
        end
        if added > 0 then
            biome_lib:dbg("biome_lib.populate_surfaces ran on mapblock at "..
                minetest.pos_to_string(minp)..".  Entry #"..
                (biome_lib.pos_hash.action_index-1).." added "..added.." items.")
        end
    end
end

-- "Play" them back, populating them with new stuff in the process

local rr = tonumber(minetest.settings:get("biome_lib_queue_run_ratio")) or -100

biome_lib.queue_run_ratio = 100 - rr
biome_lib.entries_per_step = math.max(-rr, 1)

minetest.register_globalstep(function(dtime)
    if math.random(100) > biome_lib.queue_run_ratio then return end
    for s = 1, biome_lib.entries_per_step do
        biome_lib.generate_block()
    end
end)

-- Play out the entire log all at once on shutdown
-- to prevent unpopulated map areas

minetest.register_on_shutdown(function()
    if #biome_lib.block_log == 0 then
        return
    end

    print("[biome_lib] Stand by, playing out the rest of the mapblock log")
    print("(there are "..#biome_lib.block_log.." entries)...")
    while #biome_lib.block_log > 0 do
        biome_lib.generate_block(true)
    end
end)

-- The spawning ABM

function biome_lib:spawn_on_surfaces(sd,sp,sr,sc,ss,sa)

    local biome = {}

    if type(sd) ~= "table" then
        biome.spawn_delay = sd  -- old api expects ABM interval param here.
        biome.spawn_plants = {sp}
        biome.avoid_radius = sr
        biome.spawn_chance = sc
        biome.spawn_surfaces = {ss}
        biome.avoid_nodes = sa
    else
        biome = sd
    end

    if biome.spawn_delay*time_scale >= 1 then
        biome.interval = biome.spawn_delay*time_scale
    else
        biome.interval = 1
    end

    biome_lib:set_defaults(biome)
    biome.spawn_plants_count = #(biome.spawn_plants)

    local n
    if type(biome.spawn_plants) == "table" then
        n = "random: "..biome.spawn_plants[1]..", ..."
    else
        n = biome.spawn_plants
    end
    biome.label = biome.label or "biome_lib spawn_on_surfaces(): "..n

    minetest.register_abm({
        nodenames = biome.spawn_surfaces,
        interval = biome.interval,
        chance = biome.spawn_chance,
        neighbors = biome.neighbors,
        label = biome.label,
        action = function(pos, node, active_object_count, active_object_count_wider)
            local p_top = { x = pos.x, y = pos.y + 1, z = pos.z }
            local n_top = minetest.get_node(p_top)
            local perlin_fertile_area = minetest.get_perlin(biome.seed_diff, perlin_octaves, perlin_persistence, perlin_scale)

            local fertility, temperature, humidity = get_biome_data(pos, perlin_fertile_area)

            local pos_biome_ok = pos.y >= biome.min_elevation and pos.y <= biome.max_elevation
                and fertility > biome.plantlife_limit
                and temperature <= biome.temp_min and temperature >= biome.temp_max
                and humidity <= biome.humidity_min and humidity >= biome.humidity_max
                and biome_lib:is_node_loaded(p_top)

            if not pos_biome_ok then
                return -- Outside of biome
            end

            local n_light = minetest.get_node_light(p_top, nil)
            if n_light < biome.light_min or n_light > biome.light_max then
                return -- Too dark or too bright
            end

            if biome.avoid_nodes and biome.avoid_radius and minetest.find_node_near(
                    p_top, biome.avoid_radius + math.random(-1.5,2), biome.avoid_nodes) then
                return -- Nodes to avoid are nearby
            end

            if biome.neighbors and biome.ncount and
                    #minetest.find_nodes_in_area(
                        {x=pos.x-1, y=pos.y, z=pos.z-1},
                        {x=pos.x+1, y=pos.y, z=pos.z+1},
                        biome.neighbors
                    ) <= biome.ncount then
                return -- Near neighbour nodes are not present
            end

            local NEAR_DST = biome.near_nodes_size
            if biome.near_nodes and biome.near_nodes_count and biome.near_nodes_size and
                    #minetest.find_nodes_in_area(
                        {x=pos.x-NEAR_DST, y=pos.y-biome.near_nodes_vertical, z=pos.z-NEAR_DST},
                        {x=pos.x+NEAR_DST, y=pos.y+biome.near_nodes_vertical, z=pos.z+NEAR_DST},
                        biome.near_nodes
                    ) < biome.near_nodes_count then
                return -- Far neighbour nodes are not present
            end

            if (biome.air_count and biome.air_size) and
                    #minetest.find_nodes_in_area(
                        {x=p_top.x-biome.air_size, y=p_top.y, z=p_top.z-biome.air_size},
                        {x=p_top.x+biome.air_size, y=p_top.y, z=p_top.z+biome.air_size},
                        "air"
                    ) < biome.air_count then
                return -- Not enough air
            end

            local walldir = biome_lib:find_adjacent_wall(p_top, biome.verticals_list, biome.choose_random_wall)
            if biome.alt_wallnode and walldir then
                if n_top.name == "air" then
                    minetest.swap_node(p_top, { name = biome.alt_wallnode, param2 = walldir })
                end
                return
            end

            local currentsurface = minetest.get_node(pos).name

            if biome_lib.default_water_nodes[currentsurface] and
                    #minetest.find_nodes_in_area(
                        {x=pos.x, y=pos.y-biome.depth_max-1, z=pos.z},
                        vector.new(pos),
                        biome_lib.default_wet_surfaces
                    ) == 0 then
                return -- On water but no ground nearby
            end

            local rnd = math.random(1, biome.spawn_plants_count)
            local plant_to_spawn = biome.spawn_plants[rnd]
            local fdir = biome.facedir
            if biome.random_facedir then
                fdir = math.random(biome.random_facedir[1],biome.random_facedir[2])
            end
            if type(biome.spawn_plants) == "string" then
                assert(loadstring(biome.spawn_plants.."(...)"))(pos)
            elseif not biome.spawn_on_side and not biome.spawn_on_bottom and not biome.spawn_replace_node then
                if n_top.name == "air" then
                    minetest.swap_node(p_top, { name = plant_to_spawn, param2 = fdir })
                end
            elseif biome.spawn_replace_node then
                minetest.swap_node(pos, { name = plant_to_spawn, param2 = fdir })

            elseif biome.spawn_on_side then
                local onside = biome_lib:find_open_side(pos)
                if onside then
                    minetest.swap_node(onside.newpos, { name = plant_to_spawn, param2 = onside.facedir })
                end
            elseif biome.spawn_on_bottom then
                if minetest.get_node({x=pos.x, y=pos.y-1, z=pos.z}).name == "air" then
                    minetest.swap_node({x=pos.x, y=pos.y-1, z=pos.z}, { name = plant_to_spawn, param2 = fdir} )
                end
            end
        end
    })
end

-- Function to decide how to replace a plant - either grow it, replace it with
-- a tree, run a function, or die with an error.

function biome_lib:replace_object(pos, replacement, grow_function, walldir, seeddiff)
    local growtype = type(grow_function)
    if growtype == "table" then
        minetest.swap_node(pos, biome_lib.air)
        biome_lib:grow_tree(pos, grow_function)
        return
    elseif growtype == "function" then
        local perlin_fertile_area = minetest.get_perlin(seeddiff, perlin_octaves, perlin_persistence, perlin_scale)
        local fertility, temperature, _ = get_biome_data(pos, perlin_fertile_area)
        grow_function(pos, fertility, temperature, walldir)
        return
    elseif growtype == "string" then
        local perlin_fertile_area = minetest.get_perlin(seeddiff, perlin_octaves, perlin_persistence, perlin_scale)
        local fertility, temperature, _ = get_biome_data(pos, perlin_fertile_area)
        assert(loadstring(grow_function.."(...)"))(pos, fertility, temperature, walldir)
        return
    elseif growtype == "nil" then
        minetest.swap_node(pos, { name = replacement, param2 = walldir})
        return
    elseif growtype ~= "nil" and growtype ~= "string" and growtype ~= "table" then
        error("Invalid grow function "..dump(grow_function).." used on object at ("..dump(pos)..")")
    end
end

dofile(biome_lib.modpath .. "/search_functions.lua")
assert(loadfile(biome_lib.modpath .. "/growth.lua"))(time_scale)

-- Check for infinite stacks

if minetest.get_modpath("unified_inventory") or not minetest.settings:get_bool("creative_mode") then
    biome_lib.expect_infinite_stacks = false
else
    biome_lib.expect_infinite_stacks = true
end

-- read a field from a node's definition

function biome_lib:get_nodedef_field(nodename, fieldname)
    if not minetest.registered_nodes[nodename] then
        return nil
    end
    return minetest.registered_nodes[nodename][fieldname]
end

if DEBUG then
    biome_lib.last_count = 0

    function biome_lib.show_pending_block_count()
        if biome_lib.last_count ~= #biome_lib.block_log then
            biome_lib:dbg("Pending block count: "..#biome_lib.block_log)
            biome_lib.last_count = #biome_lib.block_log
        end
        minetest.after(1, biome_lib.show_pending_block_count)
    end

    biome_lib.show_pending_block_count()

    minetest.after(0, function()
        print("Registered a total of "..(#biome_lib.surfaceslist_aircheck)+(#biome_lib.surfaceslist_no_aircheck).." surface types to be evaluated, spread")
        print("across "..#biome_lib.actionslist_aircheck.." actions with air-checking and "..#biome_lib.actionslist_no_aircheck.." actions without.")
    end)

end

print("[Biome Lib] Loaded")