module Sprockets::Server

def call(env)

environment for `"foo/bar.js"`.
A request for `"/assets/foo/bar.js"` will search your

end
run Sprockets::Environment.new
map "/assets" do

in the path.
Mapping your environment at a url prefix will serve all assets

headers, and body.
`env` Hash and returns a three item tuple with the status code,
`call` implements the Rack 1.x specification which accepts an 
def call(env)
  start_time = Time.now.to_f
  time_elapsed = lambda { ((Time.now.to_f - start_time) * 1000).to_i }
  if env['REQUEST_METHOD'] != 'GET'
    return method_not_allowed_response
  end
  msg = "Served asset #{env['PATH_INFO']} -"
  # Extract the path from everything after the leading slash
  path = Rack::Utils.unescape(env['PATH_INFO'].to_s.sub(/^\//, ''))
  # Strip fingerprint
  if fingerprint = path_fingerprint(path)
    path = path.sub("-#{fingerprint}", '')
  end
  # URLs containing a `".."` are rejected for security reasons.
  if forbidden_request?(path)
    return forbidden_response
  end
  # Look up the asset.
  options = {}
  options[:pipeline] = :self if body_only?(env)
  asset = find_asset(path, options)
  # 2.x/3.x compatibility hack. Just ignore fingerprints on ?body=1 requests.
  # 3.x/4.x prefers strong validation of fingerprint to body contents, but
  # 2.x just ignored it.
  if asset && parse_asset_uri(asset.uri)[1][:pipeline] == "self"
    fingerprint = nil
  end
  if fingerprint
    if_match = fingerprint
  elsif env['HTTP_IF_MATCH']
    if_match = env['HTTP_IF_MATCH'][/^"(\w+)"$/, 1]
  end
  if env['HTTP_IF_NONE_MATCH']
    if_none_match = env['HTTP_IF_NONE_MATCH'][/^"(\w+)"$/, 1]
  end
  if asset.nil?
    status = :not_found
  elsif fingerprint && asset.etag != fingerprint
    status = :not_found
  elsif if_match && asset.etag != if_match
    status = :precondition_failed
  elsif if_none_match && asset.etag == if_none_match
    status = :not_modified
  else
    status = :ok
  end
  case status
  when :ok
    logger.info "#{msg} 200 OK (#{time_elapsed.call}ms)"
    ok_response(asset, env)
  when :not_modified
    logger.info "#{msg} 304 Not Modified (#{time_elapsed.call}ms)"
    not_modified_response(env, if_none_match)
  when :not_found
    logger.info "#{msg} 404 Not Found (#{time_elapsed.call}ms)"
    not_found_response
  when :precondition_failed
    logger.info "#{msg} 412 Precondition Failed (#{time_elapsed.call}ms)"
    precondition_failed_response
  end
rescue Exception => e
  logger.error "Error compiling asset #{path}:"
  logger.error "#{e.class.name}: #{e.message}"
  case File.extname(path)
  when ".js"
    # Re-throw JavaScript asset exceptions to the browser
    logger.info "#{msg} 500 Internal Server Error\n\n"
    return javascript_exception_response(e)
  when ".css"
    # Display CSS asset exceptions in the browser
    logger.info "#{msg} 500 Internal Server Error\n\n"
    return css_exception_response(e)
  else
    raise
  end
end