local GUIs = {};
local currentOpenedGUI = nil;
local customOpenedGUI = nil;

function attachGUI (entityName, options)
    GUIs[entityName] = options;
end

-- Returns a entity ID from name and position
function getEntityID(entity)
    return entity.name .. "["..entity.position.x..","..entity.position.y.."]";
end

function checkAndSpawnGUI (entity)
    if (entity ~= nil) then
        local options = GUIs[entity.name];
        if (options ~= nil) then
            local entityID = getEntityID(entity)
            local newEntity = { name= game.player.opened.name, position= game.player.opened.position};

            -- TODO: Set variables on new entity so it appears to be the same entity...

            game.player.gui.center.add{type="frame", name=entityID, caption=options.title, direction= "vertical"};

            game.player.gui.center[entityID].add{type="flow", direction="horizontal", name="guiContent" };


            game.player.gui.center[entityID].add{type="flow", direction="horizontal", name="titlebar" };

            game.player.gui.center[entityID].add{type="button", name="close", caption="Close" };

            options["onopen"](game.player.gui.center[entityID]["guiContent"], newEntity);

            customOpenedGUI = {opts=options, guiName=entityID, entity= newEntity};

            game.player.opened.destroy();
            game.createentity(newEntity);
        end
    end
end

function recurseFind (GUI, name)
    if (GUI.name == name) then
     return true;
    else
        if (GUI.childrennames ~= nil) then
            for k,v in pairs(GUI.childrennames) do
                if (recurseFind(v, name) == true) then
                    return true;
                end
            end
        end
    end
    return false;
end

game.onload(function()
    game.onevent(defines.events.ontick, function ()
        if (game.player.opened ~= nil and currentOpenedGUI ~= getEntityID(game.player.opened)) then
            currentOpenedGUI = getEntityID(game.player.opened);
            checkAndSpawnGUI(game.player.opened);
        end
    end);
    game.onevent(defines.events.onguiclick, function (event)
        local element = event.element;
        if customOpenedGUI ~= nil then
            local customGUIWindow = game.player.gui.center[customOpenedGUI.guiName];
            if (element.name == "close") then
                customOpenedGUI.opts.onclose(customGUIWindow["guiContent"], customOpenedGUI.entity);
                customGUIWindow.destroy();
                customGUIWindow = nil;
                currentOpenedGUI = nil;
            else
                local isPartOfCustomGUI = recurseFind(customGUIWindow, element.name);
                if (isPartOfCustomGUI) then
                    customOpenedGUI.opts.onclick(element, customOpenedGUI.entity);
                end
            end
        end
    end);
end);



attachGUI("stone-furnace", { title = "Stone Furnace",
                             onopen = function (gui, entity)

                             end,
                             onclose = function (gui, entity)

                             end,
                             onclick = function (guiElement, entity)

                             end});