export function extend(...objects)
{
    objects = objects.filter(x => exists(x))

    if (objects.length === 0)
    {
        return
    }

    if (objects.length === 1)
    {
        return objects[0]
    }

    const to   = objects[0]
    const from = objects[1]

    if (objects.length > 2)
    {
        const last = objects.pop()
        const intermediary_result = extend.apply(this, objects)
        return extend(intermediary_result, last)
    }

    for (let key of Object.keys(from))
    {
        if (is_object(from[key]))
        {
            if (!is_object(to[key]))
            {
                to[key] = {}
            }

            extend(to[key], from[key])
        }
        else if (Array.isArray(from[key]))
        {
            if (!Array.isArray(to[key]))
            {
                to[key] = []
            }

            to[key] = to[key].concat(clone(from[key]))
        }
        else
        {
            to[key] = from[key]
        }
    }

    return to
}

export function merge()
{
    const parameters = Array.prototype.slice.call(arguments, 0)
    parameters.unshift({})
    return extend.apply(this, parameters)
}

export function clone(object)
{
    if (is_object(object))
    {
        return merge({}, object)
    }
    else if (Array.isArray(object))
    {
        return object.map(x => clone(x))
    }
    else
    {
        return object
    }
}