local gui = {};

function gui.formspec(args)
    local data = string.format("formspec_version[%d] size[%f,%f]", args.version or 3, args.w, args.h);

    if args.bg then
        data = data .. gui.bg9 {
            skin = args.bg,
            fullsize = true,
        };
    end

    for _,element in ipairs(args) do
        data = data .. element;
    end

    return data;
end

function gui.animated_image(args)
    return string.format("animated_image[%f,%f;%f,%f;%s;%s;%d;%d]",
                         args.x, args.y,
                         args.w, args.h,
                         args.id or "",
                         args.animation.texture .. ".png",
                         args.animation.frame_count,
                         args.animation.frame_duration);
end

function gui.bg9(args)
    return string.format("background9[%f,%f;%f,%f;%s;%s;%s]",
                          args.x or 0, args.y or 0,
                          args.w or 1 * (args.size or 1), args.h or 1 * (args.size or 1),
                          args.skin.texture .. ".png",
                          args.fullsize or false,
                          tostring(args.skin.radius));
end

function gui.button(args)
    if args.disabled then
        return string.format("button[%f,%f;%f,%f;disabled_button;%s]", args.x, args.y, args.w, args.h, args.text);
    end

    local data = string.format("button[%f,%f;%f,%f;%s;%s]", args.x, args.y, args.w, args.h, args.id, args.text);

    if args.tooltip then
        data = data .. gui.tooltip {
            id = args.id,
            text = args.tooltip
        };
    end

    return data;
end

function gui.container(args)
    local data = string.format("container[%f,%f]", args.x, args.y);

    if args.bg then
        data = data .. gui.bg9 {
            x = 0,
            y = 0,
            w = args.w,
            h = args.h,

            skin = args.bg,
        };
    end

    for _,element in ipairs(args) do
        data = data .. element;
    end

    return data .. "container_end[]";
end

function gui.image(args)
    return string.format("image[%f,%f;%f,%f;%s]", args.x, args.y, args.w, args.h, args.image);
end

function gui.image_button(args)
    local data = string.format("image_button[%f,%f;%f,%f;%s;%s;%s]",
                                args.x, args.y,
                                args.w, args.h,
                                args.image,
                                args.id,
                                args.text or "");

    if args.tooltip then
        data = data .. gui.tooltip {
            id = args.id,
            text = args.tooltip
        };
    end

    return data;
end

function gui.inventory(args)
    local data = "";

    if args.bg then
        for i = 0,args.w - 1 do
            for j = 0,args.h - 1 do
                data = data .. gui.bg9 {
                    x = args.x + (i * 1.25),
                    y = args.y + (j * 1.25),

                    skin = args.bg,
                };
            end
        end
    end

    data = data .. string.format("list[%s;%s;%f,%f;%f,%f;]", args.location, args.id, args.x, args.y, args.w, args.h);

    if args.tooltip then
        data = data .. gui.tooltip {
            x = args.x,
            y = args.y,
            w = args.w,
            h = args.h,
            text = args.tooltip,
        };
    end

    return data;
end

function gui.label(args)
    if args.textcolor then
        return string.format("label[%f,%f;%s%s]",
                             args.x,
                             args.y,
                             minetest.get_color_escape_sequence(args.textcolor),
                             args.text);
    end

    return string.format("label[%f,%f;%s]", args.x, args.y, args.text);
end

function gui.style_internal(selector, properties)
    local data = "[" .. selector;
    for name,value in pairs(properties) do
        data = data .. string.format(";%s=%s", name, tostring(value));
    end
    return data .. "]";
end

function gui.style(args)
    return "style" .. gui.style_internal(args.selector, args.properties);
end

function gui.style_type(args)
    return "style_type" .. gui.style_internal(args.selector, args.properties);
end

function gui.tooltip(args)
    if args.id then
        return string.format("tooltip[%s;%s]", args.id, args.text);
    else
        return string.format("tooltip[%f,%f;%f,%f;%s]", args.x, args.y, args.w, args.h, args.text);
    end
end

return gui;