exchange.chest = {}
exchange.chest.formspec = {
    main = "size[8,9]"..
        "list[current_name;pl1;0,0;3,4;]"..
        "list[current_name;pl2;5,0;3,4;]"..
        "list[current_player;main;0,5;8,4;]",
    pl1 = {
        start = "button[3,1;1,1;pl1_start;Start]",
        player = function(name) return "label[3,0;"..name.."]" end,
        accept1 = "button[3,1;1,1;pl1_accept1;Confirm]"..
                "button[3,2;1,1;pl1_cancel;Cancel]",
        accept2 = "button[3,1;1,1;pl1_accept2;Exchange]"..
                "button[3,2;1,1;pl1_cancel;Cancel]",
    },
    pl2 = {
        start = "button[4,1;1,1;pl2_start;Start]",
        player = function(name) return "label[4,0;"..name.."]" end,
        accept1 = "button[4,1;1,1;pl2_accept1;Confirm]"..
                "button[4,2;1,1;pl2_cancel;Cancel]",
        accept2 = "button[4,1;1,1;pl2_accept2;Exchange]"..
                "button[4,2;1,1;pl2_cancel;Cancel]",
    },
}

exchange.chest.check_privilege = function(listname,playername,meta)
    if listname == "pl1" then
        if playername ~= meta:get_string("pl1") then
            return false
        elseif meta:get_int("pl1step") ~= 1 then
            return false
        end
    end
    if listname == "pl2" then
        if playername ~= meta:get_string("pl2") then
            return false
        elseif meta:get_int("pl2step") ~= 1 then
            return false
        end
    end
    return true
end

exchange.chest.update_formspec = function(meta)
    formspec = exchange.chest.formspec.main
    pl_formspec = function (n)
        if meta:get_int(n.."step")==0 then
            formspec = formspec .. exchange.chest.formspec[n].start
        else
            formspec = formspec .. exchange.chest.formspec[n].player(meta:get_string(n))
            if meta:get_int(n.."step") == 1 then
                formspec = formspec .. exchange.chest.formspec[n].accept1
            elseif meta:get_int(n.."step") == 2 then
                formspec = formspec .. exchange.chest.formspec[n].accept2
            end
        end
    end
    pl_formspec("pl1") pl_formspec("pl2")
    meta:set_string("formspec",formspec)
end

exchange.chest.give_inventory = function(inv,list,playername)
    player = minetest.env:get_player_by_name(playername)
    if player then
        for k,v in ipairs(inv:get_list(list)) do
            player:get_inventory():add_item("main",v)
            inv:remove_item(list,v)
        end
    end
end

exchange.chest.cancel = function(meta)
    exchange.chest.give_inventory(meta:get_inventory(),"pl1",meta:get_string("pl1"))
    exchange.chest.give_inventory(meta:get_inventory(),"pl2",meta:get_string("pl2"))
    meta:set_string("pl1","")
    meta:set_string("pl2","")
    meta:set_int("pl1step",0)
    meta:set_int("pl2step",0)
end

exchange.chest.exchange = function(meta)
    exchange.chest.give_inventory(meta:get_inventory(),"pl1",meta:get_string("pl2"))
    exchange.chest.give_inventory(meta:get_inventory(),"pl2",meta:get_string("pl1"))
    meta:set_string("pl1","")
    meta:set_string("pl2","")
    meta:set_int("pl1step",0)
    meta:set_int("pl2step",0)
end

minetest.register_node("exchange:chest", {
    description = "Exchange chest",
    tiles = {"exchange_chest_top.png", "default_chest_top.jpg", "exchange_chest_side.png"},
    groups = {snappy=2,choppy=2,oddly_breakable_by_hand=2},
    sounds = default.node_sound_wood_defaults(),
    on_construct = function(pos)
        local meta = minetest.env:get_meta(pos)
        meta:set_string("infotext", "Exchange chest")
        meta:set_string("pl1","")
        meta:set_string("pl2","")
        exchange.chest.update_formspec(meta)
        local inv = meta:get_inventory()
        inv:set_size("pl1", 3*4)
        inv:set_size("pl2", 3*4)
    end,
    on_receive_fields = function(pos, formname, fields, sender)
        local meta = minetest.env:get_meta(pos)
        pl_receive_fields = function(n)
            if fields[n.."_start"] and meta:get_string(n) == "" then
                meta:set_string(n,sender:get_player_name())
            end
            if meta:get_string(n) == "" then
                meta:set_int(n.."step",0)
            elseif meta:get_int(n.."step")==0 then
                meta:set_int(n.."step",1)
            end
            if sender:get_player_name() == meta:get_string(n) then
                if meta:get_int(n.."step")==1 and fields[n.."_accept1"] then
                    meta:set_int(n.."step",2)
                end
                if meta:get_int(n.."step")==2 and fields[n.."_accept2"] then
                    meta:set_int(n.."step",3)
                    if n == "pl1" and meta:get_int("pl2step") == 3 then exchange.chest.exchange(meta) end
                    if n == "pl2" and meta:get_int("pl1step") == 3 then exchange.chest.exchange(meta) end
                end
                if fields[n.."_cancel"] then exchange.chest.cancel(meta) end
            end
        end
        pl_receive_fields("pl1") pl_receive_fields("pl2")
        -- End
        exchange.chest.update_formspec(meta)
    end,
    allow_metadata_inventory_move = function(pos, from_list, from_index, to_list, to_index, count, player)
        local meta = minetest.env:get_meta(pos)
        if not exchange.chest.check_privilege(from_list,player:get_player_name(),meta) then return 0 end
        if not exchange.chest.check_privilege(to_list,player:get_player_name(),meta) then return 0 end
        return count
    end,
    allow_metadata_inventory_put = function(pos, listname, index, stack, player)
        local meta = minetest.env:get_meta(pos)
        if not exchange.chest.check_privilege(listname,player:get_player_name(),meta) then return 0 end
        return stack:get_count()
    end,
    allow_metadata_inventory_take = function(pos, listname, index, stack, player)
        local meta = minetest.env:get_meta(pos)
        if not exchange.chest.check_privilege(listname,player:get_player_name(),meta) then return 0 end
        return stack:get_count()
    end,
})

minetest.register_craft({
    output = 'exchange:chest',
    recipe = {
        {"group:wood","default:steel_ingot","group:wood"},
        {"group:wood","default:steel_ingot","group:wood"},
        {"group:wood","group:wood","group:wood"},
    }
})