module YARD::Server::HTTPUtils

def parse_header(raw)
  header = Hash.new([].freeze)
  field = nil
  raw.each_line{|line|
    case line
    when /^([A-Za-z0-9!\#$%&'*+\-.^_`|~]+):\s*(.*?)\s*\z/om
      field, value = $1, $2
      field.downcase!
      header[field] = [] unless header.has_key?(field)
      header[field] << value
    when /^\s+(.*?)\s*\z/om
      value = $1
      unless field
        raise HTTPStatus::BadRequest, "bad header '#{line}'."
      end
      header[field][-1] << " " << value
    else
      raise HTTPStatus::BadRequest, "bad header '#{line}'."
    end
  }
  header.each{|key, values|
    values.each(&:strip!)
  }
  header
end