--nothing--
local grass = "nc_terrain:dirt_with_grass"
local dirt = "nc_terrain:dirt"
local tree = "nc_tree:eggcorn_planted"
local stone = "nc_terrain:stone"
local queue = {}

local function maxval(octaves,persistence,scale)
  local m = scale
  local poc = scale
  if octaves > 1 then
    for n=2,octaves do
      poc = poc*persistence
      m=m+poc
    end
  end
  return m
end

local function island(pos,r)
  local x,y,z = pos.x,pos.y,pos.z
  minetest.emerge_area({x=x-r,y=y-r,z=z-r},{x=x+r,y=y+r,z=z+r},function(bp,act,crem)
    if crem > 0 then
      return
    end
    local n = 0
    local c = 0
    local cm = (r*2+1)^3
    local function geto(x,y,z)
      local dist = (x*x+y*y+z*z)^0.5
      local uvdist = (y+r)/(r*2)
      local hdist = (x*x+z*z)^0.5
      local uhdist = (math.max(0,r-hdist)/r)^((1-uvdist)^3*5)
      local udist = math.max(0,r-dist)/r
      local m = ((math.max(r-(hdist),0)/r)^0.1*(uhdist^2))-uhdist*uvdist^3
      return m
    end
    local grasses = {}
    for x=-r,r do
      for z=-r,r do
        for y=-r,r do
          local xx,yy,zz = pos.x+x,pos.y+y,pos.z+z
          local o,o2 = geto(x,y,z),geto(x,y+1,z)
          local oc = (o > 0.4)
          local oc2 = o2 > 0.4
          local og = (o > 0.6)
          if oc then
            n=n+1
            local nam = dirt
            if not og and not oc2 then
              nam = grass
              table.insert(grasses,{x=xx,y=yy,z=zz})
            end
            if og then
              nam = stone
            end
            minetest.set_node({x=xx,y=yy,z=zz},{name=nam})
          else
            n=n+0.01
          end
          if n > 1000 then
            n=0
            --coroutine.yield()
          end
        end
      end
    end
    for n=1,4 do
      if #grasses > 1 then
        local n = math.random(1,#grasses)
        local v = table.remove(grasses,n)
        minetest.set_node(v,{name=tree})
      end
    end
  end)
end
local f = math.floor
local function spawn_island(name,pos)
  local ref = minetest.get_player_by_name(name)
  pos = {x=f(pos.x),y=f(pos.y),z=f(pos.z)}
  island(pos,16,name)
  ref:set_pos({x=pos.x,y=pos.y+256,z=pos.z})
end
local store = minetest.get_mod_storage()
local function pid(x,z)
  return "i"..x.."_"..z
end
local function checkpos(x,z)
  if store:get_string(pid(x,z)) == "" then
    return true
  end
end
local function gen_island_pos(name)
  local x,z = 0,0
  local ok = checkpos(x,z)
  while not ok do
    x,z = x+math.random(-1,1),z+math.random(-1,1)
    ok = checkpos(x,z)
  end
  store:set_string(pid(x,z),name)
  local range = {min={x=x*128-64,y=256-64,z=z*128-64},max={x=x*128+64,y=256+64,z=z*128+64}}
  local ip = {x=x*128+math.random(-32,32),y=256,z=z*128+math.random(-32,32)}
  spawn_island(name,ip)
  return pid(x,z),ip,range
end
local updrate = 0.5
local to_upd = updrate
minetest.register_globalstep(function(dt)
  for f,_ in pairs(queue) do
    local ok,err = coroutine.resume(f)
    if not ok then
      print(err)
      queue[f]=nil
    end
  end
  to_upd = to_upd-dt
  if to_upd <= 0 then
    to_upd = to_upd+updrate
    for k,ref in pairs(minetest.get_connected_players()) do
      local p = ref:get_pos()
      if p.y < 0 then
        ref:set_hp(ref:get_hp()-2,{reason="set_hp"})
        if p.y < -128 then
          local meta = ref:get_meta()
          local pos = minetest.string_to_pos(meta:get_string("islandpos"))
          if pos then
            pos.y=pos.y+256
            ref:set_pos(pos)
          end
        end
      end
    end
  end
end)

minetest.register_chatcommand("reset",{
  description = "Reset your island",
  func = function(name,param)
    local ref = minetest.get_player_by_name(name)
    local meta = ref:get_meta()
    local r = meta:get_string("islandrange")
    r = minetest.deserialize(r)
    minetest.emerge_area(r.min,r.max,function(bp,act,crem)
      if crem > 0 then
        return
      end
      local ref = minetest.get_player_by_name(name)
      local meta = ref:get_meta()
      local pos = minetest.string_to_pos(meta:get_string("islandpos"))
      if pos then
        local r = meta:get_string("islandrange")
        r = minetest.deserialize(r)
        print("PREVM")
        air_c = minetest.get_content_id("air")
        local vm = VoxelManip(r.min,r.max)
        local rmi,rma = vm:get_emerged_area()
        local var = VoxelArea:new{MinEdge=rmi,MaxEdge=rma}
        local d = vm:get_data()
        for x=r.min.x,r.max.x do
          for y=r.min.y,r.max.y do
            for z=r.min.z,r.max.z do
              local i = var:index(x,y,z)
              d[i] = air_c
            end
          end
        end
        vm:set_data(d)
        print("PREWRITE")
        vm:write_to_map()
        print("POSTVM")
        spawn_island(name,pos)
      end
    end)
  end
})

minetest.register_on_joinplayer(function(ref)
  local meta = ref:get_meta()
  local name = ref:get_player_name()
  if meta:get_string("island") == "" then
    local p,ip,r = gen_island_pos(name)
    meta:set_string("island",p)
    meta:set_string("islandpos",minetest.pos_to_string(ip))
    meta:set_string("islandrange",minetest.serialize(r))
  end
end)