rspawn = {}
rspawn.playerspawns = {}

local mpath = minetest.get_modpath("rspawn")

-- Water level, plus one to ensure we are above the sea.
local water_level = tonumber(minetest.settings:get("water_level", "1") )+1
local radial_step = 16

local static_spawnpoint = minetest.setting_get_pos("static_spawnpoint") or {x=0, y=50, z=0}

rspawn.adminname = minetest.settings:get("name", "singleplayer")
rspawn.spawnanywhere = minetest.settings:get_bool("spawn_anywhere", true)
rspawn.bedspawn = minetest.setting_getbool("enable_bed_respawn", true)

dofile(mpath.."/src/data.lua")
dofile(mpath.."/src/commands.lua")

rspawn:spawnload()

local function forceload_operate(pos1, pos2, handler)
    local i,j,k

    for i=pos1.x,pos2.x,16 do
        for j=pos1.y,pos2.y,16 do
            for k=pos1.z,pos2.z,16 do
                handler({x=i,y=j,z=k})
            end
        end
    end
end

local function forceload_blocks_in(pos1, pos2)
    forceload_operate(pos1, pos2, minetest.forceload_block)
end

local function forceload_free_blocks_in(pos1, pos2)
    forceload_operate(pos1, pos2, minetest.forceload_free_block)
end

local function daylight_above(min_daylight, pos)
    local level = minetest.get_node_light(pos, 0.5)
    return min_daylight <= level
end

function rspawn:newspawn(pos, radius)
    -- Given a seed position and a radius, find an exact spawn location
    --   that is walkable and with 2 air nodes above it

    if not radius then
        radius = radial_step
    end

    if radius > 4*radial_step then
        minetest.debug("__ No valid spawnable location around "..minetest.pos_to_string(pos))
        return
    end

    minetest.debug("Trying somewhere around "..minetest.pos_to_string(pos))

    local breadth = radius/2
    local altitude = radius*2

    local pos1 = {x=pos.x-breadth, y=pos.y, z=pos.z-breadth}
    local pos2 = {x=pos.x+breadth, y=pos.y+altitude, z=pos.z+breadth}

    minetest.debug("Searching "..minetest.pos_to_string(pos1).." to "..minetest.pos_to_string(pos2))

    minetest.emerge_area(pos1, pos2)
    forceload_blocks_in(pos1, pos2)

    local airnodes = minetest.find_nodes_in_area(pos1, pos2, {"air"})
    local validnodes = {}

    minetest.debug("Found "..tostring(#airnodes).." air nodes within "..tostring(radius))
    for _,anode in pairs(airnodes) do
        local under = minetest.get_node( {x=anode.x, y=anode.y-1, z=anode.z} ).name
        local over = minetest.get_node( {x=anode.x, y=anode.y+1, z=anode.z} ).name
        under = minetest.registered_nodes[under]
        over = minetest.registered_nodes[over]

        if under.walkable
         and not over.walkable
         and not minetest.is_protected(anode, rspawn.adminname)
         and daylight_above(7, anode) then
            validnodes[#validnodes+1] = anode
        end
    end

    if #validnodes > 0 then
        minetest.log("info", "New spawn point found with radius "..tostring(radius))
        forceload_free_blocks_in(pos1, pos2)
        return validnodes[math.random(1,#validnodes)]
    end

    local pos = rspawn:newspawn(pos, radius+radial_step)
    if not pos then
        -- Nothing found, do cleanup with this largest forceloaded area
        forceload_free_blocks_in(pos1, pos2)
    end
    return pos
end

function rspawn:genpos()
    -- Generate a random position, and derive a new spawn position
    local pos = static_spawnpoint

    if rspawn.spawnanywhere then
        pos = {
            x = math.random(-30000,30000),
            y = math.random(water_level, water_level+10),
            z = math.random(-30000,30000),
        }
    end

    return pos
end

function rspawn:set_new_playerspawn(player, args)
    local newpos
    if args == "here" then
        newpos = player:get_pos()
    elseif args then
        newpos = minetest.string_to_pos(args)
    end

    if not newpos then
        newpos = rspawn:genpos()
    end

    local spawnpos = rspawn:newspawn(newpos)
    local name = player:get_player_name()

    if spawnpos then
        rspawn.playerspawns[name] = spawnpos
        rspawn:spawnsave()
        return spawnpos
    end
end

local function confirm_new_spawn(name, newpos)
    minetest.chat_send_player(name, "New spawn set at "..minetest.pos_to_string(newpos))
    minetest.get_player_by_name(name):setpos(rspawn.playerspawns[name])
end

function rspawn:double_set_new_playerspawn(player, attempts)
    local cpos = minetest.pos_to_string(rspawn:genpos())
    local name = player:get_player_name()
    attempts = attempts or 1

    minetest.chat_send_player(name, tostring(attempts)..": Searching for a suitable spawn around "..cpos)

    local newpos = rspawn:set_new_playerspawn(player, cpos)

    if not newpos then
        -- Repeat only after some time: give the server time to get through previous emerge calls
        minetest.after(4,function()
            -- Second attempt at the same location - emerge calls should have yielded
            --   map data to work with
            newpos = rspawn:set_new_playerspawn(player, cpos)

            if not newpos then
                if attempts > 0 then
                    -- Repeat the process at a new location
                    rspawn:double_set_new_playerspawn(player, attempts - 1)
                else
                    minetest.chat_send_player(name, "! Could not identify suitable spawn location (try again?)")
                end
            else
                confirm_new_spawn(name, newpos)
            end
        end)
    else
        confirm_new_spawn(name, newpos)
    end
end

minetest.register_on_joinplayer(function(player)
    -- Use the recursive mode - it is not acceptable for a player
    --   not to receive a randomized spawn
    minetest.after(1,function()
        if not rspawn.playerspawns[player:get_player_name()] then
            rspawn:double_set_new_playerspawn(player, 10)
        end
    end)
end)

minetest.register_on_respawnplayer(function(player)
    local name = player:get_player_name()
    if rspawn.bedspawn == true then
        local pos = beds.spawn[name]
        if pos then
            player:setpos(pos)
            return true
        end
    end

    -- And if no bed, nor bed spwawning not active:
    player:setpos(rspawn.playerspawns[name])
    return true
end)