class Middleman::Extensions::RelativeAssets

def asset_path(kind, source, options={})
  super(kind, source, app.extensions[:relative_assets].mark_as_relative(super, options, current_resource))
end

def asset_url(path, prefix='', options={})
  super(path, prefix, app.extensions[:relative_assets].mark_as_relative(super, options, current_resource))
end

def initialize(app, options_hash={}, &block)
  super
  return if options[:helpers_only]
  app.rewrite_inline_urls id: :relative_assets,
                          url_extensions: options.exts || app.config[:asset_extensions],
                          source_extensions: options.sources,
                          ignore: options.ignore,
                          rewrite_ignore: options.rewrite_ignore,
                          proc: method(:rewrite_url)
end

def mark_as_relative(file_path, opts, current_resource)
  result = opts.dup
  valid_exts = options.sources
  return result unless current_resource
  return result unless valid_exts.include?(current_resource.ext)
  rewrite_ignores = Array(options.rewrite_ignore || [])
  path = current_resource.destination_path
  return result if rewrite_ignores.any? do |i|
    ::Middleman::Util.path_match(i, path) || ::Middleman::Util.path_match(i, "/#{path}")
  end
  return result if Array(options.ignore || []).any? do |r|
    ::Middleman::Util.should_ignore?(r, file_path)
  end
  result[:relative] = true unless result.key?(:relative)
  result
end

def rewrite_url(asset_path, dirpath, request_path)
  uri = ::Middleman::Util.parse_uri(asset_path)
  return if uri.path[0..0] != '/'
  relative_path = uri.host.nil?
  full_asset_path = if relative_path
    dirpath.join(asset_path).to_s
  else
    asset_path
  end
  current_dir = Pathname(request_path).dirname
  result = Pathname(full_asset_path).relative_path_from(current_dir).to_s
  result
end