class GraphQL::Relay::ArrayConnection

def cursor_from_node(item)
  idx = starting_offset + sliced_nodes.find_index(item) + 1
  Base64.strict_encode64(idx.to_s)
end

def has_next_page
  !!(first && sliced_nodes.count > limit)
end

def has_previous_page
  !!(last && starting_offset > 0)
end

def index_from_cursor(cursor)
  Base64.decode64(cursor).to_i
end

def limit
  @limit ||= begin
    limit_from_arguments = if first
      first
    else
      if previous_offset < 0
        previous_offset + (last ? last : 0)
      else
        last
      end
    end
    [limit_from_arguments, max_page_size].compact.min
  end
end

def paged_nodes
  @paged_nodes ||= begin
    items = sliced_nodes
    if limit
      items.first(limit)
    else
      items
    end
  end
end

def previous_offset
  @previous_offset ||= if after
    index_from_cursor(after)
  elsif before
    prev_page_size = [max_page_size, last].compact.min || 0
    index_from_cursor(before) - prev_page_size - 1
  else
    0
  end
end

def sliced_nodes
  @sliced_nodes ||= nodes[starting_offset..-1]
end

def starting_offset
  @starting_offset = if before
    [previous_offset, 0].max
  else
    previous_offset
  end
end