-- ===================================================================

local function is_empty (s)
    if (s == nil) or (s == '') then return true end
    return false
end

-- ===================================================================

local                             disable_multispawn  =
    minetest.setting_getbool    ("disable_multispawn" )

local                             engine_spawn        =
    minetest.setting_getbool    ("engine_spawn"       )

local                             mg_name             =
    minetest.get_mapgen_setting ("mg_name"            )

local                          static_spawn_point     =
    minetest.settings:get    ("static_spawn_point"    )

local                          static_spawnpoint      =
    minetest.settings:get    ("static_spawnpoint"     )

-- ===================================================================

if     is_empty (static_spawn_point) then
                 static_spawn_point = static_spawnpoint
end

if not is_empty (static_spawn_point) then
    disable_multispawn = true
end

-- ===================================================================

if  mg_name == "v6"                   or
    mg_name == "singlenode"           or
    not is_empty (static_spawn_point) or
    engine_spawn then
    return
end

if not disable_multispawn and #spawnpoints.list > 0 then
    return
end

-- ===================================================================

-- Parameters
-------------

-- Resolution of search grid in nodes.
local res = 64
-- Number of points checked in the square search grid (edge * edge).
local checks = 128 * 128
-- Starting point for biome checks. This also sets the y co-ordinate for all
-- points checked, so the suitable biomes must be active at this y.
local pos = {x = 0, y = 8, z = 0}

-- Table of suitable biomes

local biome_ids = {
    minetest.get_biome_id ("taiga"               ) ,
    minetest.get_biome_id ("coniferous_forest"   ) ,
    minetest.get_biome_id ("deciduous_forest"    ) ,
    minetest.get_biome_id ("glacier"             ) ,
    minetest.get_biome_id ("stone_grassland"     ) ,
    minetest.get_biome_id ("sandstone_grassland" ) ,
    minetest.get_biome_id ("grassland"           ) ,
    minetest.get_biome_id ("desert"              ) ,
    minetest.get_biome_id ("rainforest"          ) ,
    minetest.get_biome_id ("savanna"             ) ,
}

-- End of parameters
--------------------

-- Direction table

local dirs = {
    {x = 0, y = 0, z = 1},
    {x = -1, y = 0, z = 0},
    {x = 0, y = 0, z = -1},
    {x = 1, y = 0, z = 0},
}

-- Initial variables

local edge_len = 1
local edge_dist = 0
local dir_step = 0
local dir_ind = 1
local searched = false
local success = false
local spawn_pos = {}

--Functions
-----------

-- Get next position on square search spiral

local function next_pos()
    if edge_dist == edge_len then
        edge_dist = 0
        dir_ind = dir_ind + 1
        if dir_ind == 5 then
            dir_ind = 1
        end
        dir_step = dir_step + 1
        edge_len = math.floor(dir_step / 2) + 1
    end

    local dir = dirs[dir_ind]
    local move = vector.multiply(dir, res)

    edge_dist = edge_dist + 1

    return vector.add(pos, move)
end

-- Spawn position search

local function search()
    for iter = 1, checks do
        local biome_data = minetest.get_biome_data(pos)
        -- Sometimes biome_data is nil
        local biome = biome_data and biome_data.biome
        for id_ind = 1, #biome_ids do
            local biome_id = biome_ids[id_ind]
            if biome == biome_id then
                local spawn_y = minetest.get_spawn_level(pos.x, pos.z)
                if spawn_y then
                    spawn_pos = {x = pos.x, y = spawn_y, z = pos.z}
                    return true
                end
            end
        end

        pos = next_pos()
    end

    return false
end

-- On new player spawn and player respawn

-- Search for spawn position once per server session. If successful, store
-- position and reposition players, otherwise leave them at engine spawn
-- position.

local function on_spawn(player)
    if not searched then
        success = search()
        searched = true
    end
    if success then
        player:set_pos(spawn_pos)
    end
end

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

local                          enable_bed_respawn  =
    minetest.setting_getbool ("enable_bed_respawn" )

if enable_bed_respawn == nil then
   enable_bed_respawn = true
end

minetest.register_on_respawnplayer(function(player)
    -- Avoid respawn conflict with beds mod
    if beds and enable_bed_respawn and
            beds.spawn[player:get_player_name()] then
        return
    end

    on_spawn(player)
    return true
end)