class Rack::URLMap

def call(env)
  path        = env[PATH_INFO]
  script_name = env[SCRIPT_NAME]
  http_host   = env[HTTP_HOST]
  server_name = env[SERVER_NAME]
  server_port = env[SERVER_PORT]
  is_same_server = casecmp?(http_host, server_name) ||
                   casecmp?(http_host, "#{server_name}:#{server_port}")
  is_host_known = @known_hosts.include? http_host
  @mapping.each do |host, location, match, app|
    unless casecmp?(http_host, host) \
        || casecmp?(server_name, host) \
        || (!host && is_same_server) \
        || (!host && !is_host_known) # If we don't have a matching host, default to the first without a specified host
      next
    end
    next unless m = match.match(path.to_s)
    rest = m[1]
    next unless !rest || rest.empty? || rest[0] == ?/
    env[SCRIPT_NAME] = (script_name + location)
    env[PATH_INFO] = rest
    return app.call(env)
  end
  [404, { CONTENT_TYPE => "text/plain", "x-cascade" => "pass" }, ["Not Found: #{path}"]]
ensure
  env[PATH_INFO]   = path
  env[SCRIPT_NAME] = script_name
end

def casecmp?(v1, v2)
  # if both nil, or they're the same string
  return true if v1 == v2
  # if either are nil... (but they're not the same)
  return false if v1.nil?
  return false if v2.nil?
  # otherwise check they're not case-insensitive the same
  v1.casecmp(v2).zero?
end

def initialize(map = {})
  remap(map)
end

def remap(map)
  @known_hosts = Set[]
  @mapping = map.map { |location, app|
    if location =~ %r{\Ahttps?://(.*?)(/.*)}
      host, location = $1, $2
      @known_hosts << host
    else
      host = nil
    end
    unless location[0] == ?/
      raise ArgumentError, "paths need to start with /"
    end
    location = location.chomp('/')
    match = Regexp.new("^#{Regexp.quote(location).gsub('/', '/+')}(.*)", Regexp::NOENCODING)
    [host, location, match, app]
  }.sort_by do |(host, location, _, _)|
    [host ? -host.size : Float::INFINITY, -location.size]
  end
end