require 'net/http'
require 'stringio'
require 'time'
require 'uri'

require 'rubygems'

##
# RemoteFetcher handles the details of fetching gems and gem information from
# a remote source.

class Gem::RemoteFetcher

  include Gem::UserInteraction

  ##
  # A FetchError exception wraps up the various possible IO and HTTP failures
  # that could happen while downloading from the internet.

  class FetchError < Gem::Exception

    ##
    # The URI which was being accessed when the exception happened.

    attr_accessor :uri

    def initialize(message, uri)
      super message
      @uri = uri
    end

    def to_s # :nodoc:
      "#{super} (#{uri})"
    end

  end

  @fetcher = nil

  ##
  # Cached RemoteFetcher instance.

  def self.fetcher
    @fetcher ||= self.new Gem.configuration[:http_proxy]
  end

  ##
  # Initialize a remote fetcher using the source URI and possible proxy
  # information.
  #
  # +proxy+
  # * [String]: explicit specification of proxy; overrides any environment
  #             variable setting
  # * nil: respect environment variables (HTTP_PROXY, HTTP_PROXY_USER,
  #        HTTP_PROXY_PASS)
  # * <tt>:no_proxy</tt>: ignore environment variables and _don't_ use a proxy

  def initialize(proxy)
    Socket.do_not_reverse_lookup = true

    @connections = {}
    @requests = Hash.new 0
    @proxy_uri =
      case proxy
      when :no_proxy then nil
      when nil then get_proxy_from_env
      when URI::HTTP then proxy
      else URI.parse(proxy)
      end
  end

  ##
  # Moves the gem +spec+ from +source_uri+ to the cache dir unless it is
  # already there.  If the source_uri is local the gem cache dir copy is
  # always replaced.

  def download(spec, source_uri, install_dir = Gem.dir)
    if File.writable?(install_dir)
      cache_dir = File.join install_dir, 'cache'
    else
      cache_dir = File.join(Gem.user_dir, 'cache')
    end

    gem_file_name = "#{spec.full_name}.gem"
    local_gem_path = File.join cache_dir, gem_file_name

    FileUtils.mkdir_p cache_dir rescue nil unless File.exist? cache_dir

    source_uri = URI.parse source_uri unless URI::Generic === source_uri
    scheme = source_uri.scheme

    # URI.parse gets confused by MS Windows paths with forward slashes.
    scheme = nil if scheme =~ /^[a-z]$/i

    case scheme
    when 'http', 'https' then
      unless File.exist? local_gem_path then
        begin
          say "Downloading gem #{gem_file_name}" if
            Gem.configuration.really_verbose

          remote_gem_path = source_uri + "gems/#{gem_file_name}"

          gem = Gem::RemoteFetcher.fetcher.fetch_path remote_gem_path
        rescue Gem::RemoteFetcher::FetchError
          raise if spec.original_platform == spec.platform

          alternate_name = "#{spec.original_name}.gem"

          say "Failed, downloading gem #{alternate_name}" if
            Gem.configuration.really_verbose

          remote_gem_path = source_uri + "gems/#{alternate_name}"

          gem = Gem::RemoteFetcher.fetcher.fetch_path remote_gem_path
        end

        File.open local_gem_path, 'wb' do |fp|
          fp.write gem
        end
      end
    when nil, 'file' then # TODO test for local overriding cache
      begin
        FileUtils.cp source_uri.to_s, local_gem_path
      rescue Errno::EACCES
        local_gem_path = source_uri.to_s
      end

      say "Using local gem #{local_gem_path}" if
        Gem.configuration.really_verbose
    else
      raise Gem::InstallError, "unsupported URI scheme #{source_uri.scheme}"
    end

    local_gem_path
  end

  ##
  # Downloads +uri+ and returns it as a String.

  def fetch_path(uri, mtime = nil, head = false)
    data = open_uri_or_path uri, mtime, head
    data = Gem.gunzip data if data and not head and uri.to_s =~ /gz$/
    data
  rescue FetchError
    raise
  rescue Timeout::Error
    raise FetchError.new('timed out', uri)
  rescue IOError, SocketError, SystemCallError => e
    raise FetchError.new("#{e.class}: #{e}", uri)
  end

  ##
  # Returns the size of +uri+ in bytes.

  def fetch_size(uri) # TODO: phase this out
    response = fetch_path(uri, nil, true)

    response['content-length'].to_i
  end

  def escape(str)
    return unless str
    URI.escape(str)
  end

  def unescape(str)
    return unless str
    URI.unescape(str)
  end

  ##
  # Returns an HTTP proxy URI if one is set in the environment variables.

  def get_proxy_from_env
    env_proxy = ENV['http_proxy'] || ENV['HTTP_PROXY']

    return nil if env_proxy.nil? or env_proxy.empty?

    uri = URI.parse env_proxy

    if uri and uri.user.nil? and uri.password.nil? then
      # Probably we have http_proxy_* variables?
      uri.user = escape(ENV['http_proxy_user'] || ENV['HTTP_PROXY_USER'])
      uri.password = escape(ENV['http_proxy_pass'] || ENV['HTTP_PROXY_PASS'])
    end

    uri
  end

  ##
  # Normalize the URI by adding "http://" if it is missing.

  def normalize_uri(uri)
    (uri =~ /^(https?|ftp|file):/) ? uri : "http://#{uri}"
  end

  ##
  # Creates or an HTTP connection based on +uri+, or retrieves an existing
  # connection, using a proxy if needed.

  def connection_for(uri)
    net_http_args = [uri.host, uri.port]

    if @proxy_uri then
      net_http_args += [
        @proxy_uri.host,
        @proxy_uri.port,
        @proxy_uri.user,
        @proxy_uri.password
      ]
    end

    connection_id = net_http_args.join ':'
    @connections[connection_id] ||= Net::HTTP.new(*net_http_args)
    connection = @connections[connection_id]

    if uri.scheme == 'https' and not connection.started? then
      require 'net/https'
      connection.use_ssl = true
      connection.verify_mode = OpenSSL::SSL::VERIFY_NONE
    end

    connection.start unless connection.started?

    connection
  end

  ##
  # Read the data from the (source based) URI, but if it is a file:// URI,
  # read from the filesystem instead.

  def open_uri_or_path(uri, last_modified = nil, head = false, depth = 0)
    raise "block is dead" if block_given?

    return open(get_file_uri_path(uri)) if file_uri? uri

    uri = URI.parse uri unless URI::Generic === uri
    raise ArgumentError, 'uri is not an HTTP URI' unless URI::HTTP === uri

    fetch_type = head ? Net::HTTP::Head : Net::HTTP::Get
    response   = request uri, fetch_type, last_modified

    case response
    when Net::HTTPOK, Net::HTTPNotModified then
      head ? response : response.body
    when Net::HTTPMovedPermanently, Net::HTTPFound, Net::HTTPSeeOther,
         Net::HTTPTemporaryRedirect then
      raise FetchError.new('too many redirects', uri) if depth > 10

      open_uri_or_path(response['Location'], last_modified, head, depth + 1)
    else
      raise FetchError.new("bad response #{response.message} #{response.code}", uri)
    end
  end

  ##
  # Performs a Net::HTTP request of type +request_class+ on +uri+ returning
  # a Net::HTTP response object.  request maintains a table of persistent
  # connections to reduce connect overhead.

  def request(uri, request_class, last_modified = nil)
    request = request_class.new uri.request_uri

    unless uri.nil? || uri.user.nil? || uri.user.empty? then
      request.basic_auth uri.user, uri.password
    end

    ua = "RubyGems/#{Gem::RubyGemsVersion} #{Gem::Platform.local}"
    ua << " Ruby/#{RUBY_VERSION} (#{RUBY_RELEASE_DATE}"
    ua << " patchlevel #{RUBY_PATCHLEVEL}" if defined? RUBY_PATCHLEVEL
    ua << ")"

    request.add_field 'User-Agent', ua
    request.add_field 'Connection', 'keep-alive'
    request.add_field 'Keep-Alive', '30'

    if last_modified then
      last_modified = last_modified.utc
      request.add_field 'If-Modified-Since', last_modified.rfc2822
    end

    connection = connection_for uri

    retried = false
    bad_response = false

    begin
      @requests[connection.object_id] += 1
      response = connection.request request
      say "#{request.method} #{response.code} #{response.message}: #{uri}" if
        Gem.configuration.really_verbose
    rescue Net::HTTPBadResponse
      reset connection

      raise FetchError.new('too many bad responses', uri) if bad_response

      bad_response = true
      retry
    # HACK work around EOFError bug in Net::HTTP
    # NOTE Errno::ECONNABORTED raised a lot on Windows, and make impossible
    # to install gems.
    rescue EOFError, Errno::ECONNABORTED, Errno::ECONNRESET
      requests = @requests[connection.object_id]
      say "connection reset after #{requests} requests, retrying" if
        Gem.configuration.really_verbose

      raise FetchError.new('too many connection resets', uri) if retried

      reset connection

      retried = true
      retry
    end

    response
  end

  ##
  # Resets HTTP connection +connection+.

  def reset(connection)
    @requests.delete connection.object_id

    connection.finish
    connection.start
  end

  ##
  # Checks if the provided string is a file:// URI.

  def file_uri?(uri)
    uri =~ %r{\Afile://}
  end

  ##
  # Given a file:// URI, returns its local path.

  def get_file_uri_path(uri)
    uri.sub(%r{\Afile://}, '')
  end

end