class Download
  class Error < Exception ; end
  
  attr_accessor :source, :content_type
  
  def initialize(source, file_path)
    @source = source
    @file_path = file_path
  end

  # Downloads to @file_path
  def download!
    http_get_streaming(@source) do |response|
      self.content_type = response["Content-Type"]
      File.open(@file_path, "wb") do |out|
        response.read_body(out)
      end
    end
    @source = fix_image_board_sources(@source)
  end

# private
  def handle_pixiv(source, headers)
    if source =~ /pixiv\.net/
      headers["Referer"] = "http://www.pixiv.net"

      # Don't download the small version
      if source =~ %r!(/img/.+?/.+?)_m.+$!
        match = $1
        source.sub!(match + "_m", match)
      end
    end
  
    source
  end

  def http_get_streaming(source, options = {})
    max_size = options[:max_size] || Danbooru.config.max_file_size
    max_size = nil if max_size == 0 # unlimited
    limit = 4

    while true
      url = URI.parse(source)

      unless url.is_a?(URI::HTTP)
        raise Error.new("URL must be HTTP")
      end

      Net::HTTP.start(url.host, url.port) do |http|
        http.read_timeout = 10
        headers = {
          "User-Agent" => "#{Danbooru.config.safe_app_name}/#{Danbooru.config.version}"
        }
        source = handle_pixiv(source, headers)
        http.request_get(url.request_uri, headers) do |res|
          case res
          when Net::HTTPSuccess then
            if max_size
              len = res["Content-Length"]
              raise Error.new("File is too large (#{len} bytes)") if len && len.to_i > max_size
            end
            yield(res)
            return

          when Net::HTTPRedirection then
            if limit == 0 then
              raise Error.new("Too many redirects")
            end
            source = res["location"]
            limit -= 1

          else
            raise Error.new("HTTP error code: #{res.code} #{res.message}")
          end
        end # http.request_get
      end # http.start
    end # while
  end # def

  def fix_image_board_sources(source)
    if source =~ /\/src\/\d{12,}|urnc\.yi\.org|yui\.cynthia\.bne\.jp/
      "Image board"
    else
      source
    end
  end
end