# File lib/mechanize.rb, line 109
    def inherited(child)
      child.html_parser ||= html_parser
      child.log ||= log
      super
    end

# File lib/mechanize.rb, line 116
  def initialize
    # attr_accessors
    @cookie_jar     = CookieJar.new
    @log            = nil
    @open_timeout   = nil
    @read_timeout   = nil
    @user_agent     = AGENT_ALIASES['Mechanize']
    @watch_for_set  = nil
    @history_added  = nil
    @ca_file        = nil # OpenSSL server certificate file

    # callback for OpenSSL errors while verifying the server certificate
    # chain, can be used for debugging or to ignore errors by always
    # returning _true_
    @verify_callback = nil
    @cert           = nil # OpenSSL Certificate
    @key            = nil # OpenSSL Private Key
    @pass           = nil # OpenSSL Password
    @redirect_ok    = true # Should we follow redirects?
    @gzip_enabled   = true

    # attr_readers
    @history        = Mechanize::History.new
    @pluggable_parser = PluggableParser.new

    # Auth variables
    @user           = nil # Auth User
    @password       = nil # Auth Password
    @digest         = nil # DigestAuth Digest
    @auth_hash      = {}  # Keep track of urls for sending auth
    @request_headers= {}  # A hash of request headers to be used

    # Proxy settings
    @proxy_addr     = nil
    @proxy_pass     = nil
    @proxy_port     = nil
    @proxy_user     = nil

    @conditional_requests = true

    @follow_meta_refresh  = false
    @redirection_limit    = 20

    # Connection Cache & Keep alive
    @connection_cache = {}
    @keep_alive_time  = 300
    @keep_alive       = true

    @scheme_handlers  = Hash.new { |h,k|
      h[k] = lambda { |link, page|
        raise UnsupportedSchemeError.new(k)
      }
    }
    @scheme_handlers['http']      = lambda { |link, page| link }
    @scheme_handlers['https']     = @scheme_handlers['http']
    @scheme_handlers['relative']  = @scheme_handlers['http']
    @scheme_handlers['file']      = @scheme_handlers['http']

    @pre_connect_hook = Chain::PreConnectHook.new
    @post_connect_hook = Chain::PostConnectHook.new

    @html_parser = self.class.html_parser

    yield self if block_given?
  end

# File lib/mechanize.rb, line 213
  def auth(user, password)
    @user       = user
    @password   = password
  end

# File lib/mechanize.rb, line 320
  def back
    @history.pop
  end

# File lib/mechanize.rb, line 311
  def click(link)
    referer = link.page rescue referer = nil
    href = link.respond_to?(:href) ? link.href :
      (link['href'] || link['src'])
    get(:url => href, :referer => (referer || current_page()))
  end

# File lib/mechanize.rb, line 208
  def cookies
    @cookie_jar.to_a
  end

# File lib/mechanize.rb, line 408
  def current_page
    @history.last
  end

# File lib/mechanize.rb, line 280
  def delete(url, query_params = {}, options = {})
    page = head(url, query_params, options.merge({:verb => :delete}))
    add_to_history(page)
    page
  end

# File lib/mechanize.rb, line 220
  def get(options, parameters = [], referer = nil)
    verb = :get

    unless options.is_a? Hash
      url = options
      unless parameters.respond_to?(:each) # FIXME: Remove this in 0.8.0
        referer = parameters
        parameters = []
      end
    else
      raise ArgumentError.new("url must be specified") unless url = options[:url]
      parameters = options[:params] || []
      referer    = options[:referer]
      headers    = options[:headers]
      verb       = options[:verb] || verb
    end

    unless referer
      if url.to_s =~ /^http/
        referer = Page.new(nil, {'content-type'=>'text/html'})
      else
        referer = current_page || Page.new(nil, {'content-type'=>'text/html'})
      end
    end

    # FIXME: Huge hack so that using a URI as a referer works.  I need to
    # refactor everything to pass around URIs but still support
    # Mechanize::Page#base
    unless referer.is_a?(Mechanize::File)
      referer = referer.is_a?(String) ?
      Page.new(URI.parse(referer), {'content-type' => 'text/html'}) :
        Page.new(referer, {'content-type' => 'text/html'})
    end

    # fetch the page
    page = fetch_page(  :uri      => url,
                        :referer  => referer,
                        :headers  => headers || {},
                        :verb     => verb,
                        :params   => parameters
                        )
    add_to_history(page)
    yield page if block_given?
    page
  end

# File lib/mechanize.rb, line 305
  def get_file(url)
    get(url).body
  end

# File lib/mechanize.rb, line 291
  def head(url, query_params = {}, options = {})
    options = {
      :uri      => url,
      :headers  => {},
      :params   => query_params,
      :verb     => :head
    }.merge(options)
    # fetch the page
    page = fetch_page(options)
    yield page if block_given?
    page
  end

# File lib/mechanize.rb, line 185
  def log; self.class.log end

# File lib/mechanize.rb, line 184
  def log=(l); self.class.log = l end

# File lib/mechanize.rb, line 183
  def max_history; @history.max_size end

# File lib/mechanize.rb, line 182
  def max_history=(length); @history.max_size = length end

# File lib/mechanize.rb, line 334
  def post(url, query={}, headers={})
    if query.is_a?(String)
      return request_with_entity(:post, url, query, :headers => headers)
    end
    node = {}
    # Create a fake form
    class << node
      def search(*args); []; end
    end
    node['method'] = 'POST'
    node['enctype'] = 'application/x-www-form-urlencoded'

    form = Form.new(node)
    query.each { |k,v|
      if v.is_a?(IO)
        form.enctype = 'multipart/form-data'
        ul = Form::FileUpload.new({'name' => k.to_s},::File.basename(v.path))
        ul.file_data = v.read
        form.file_uploads << ul
      else
        form.fields << Form::Field.new({'name' => k.to_s},v)
      end
    }
    post_form(url, form, headers)
  end

# File lib/mechanize.rb, line 191
  def post_connect_hooks
    @post_connect_hook.hooks
  end

# File lib/mechanize.rb, line 187
  def pre_connect_hooks
    @pre_connect_hook.hooks
  end

# File lib/mechanize.rb, line 271
  def put(url, entity, options = {})
    request_with_entity(:put, url, entity, options)
  end

# File lib/mechanize.rb, line 382
  def request_with_entity(verb, url, entity, options={})
    cur_page = current_page || Page.new( nil, {'content-type'=>'text/html'})

    options = {
      :uri      => url,
      :referer  => cur_page,
      :headers  => {},
    }.update(options)

    headers = {
      'Content-Type' => 'application/octet-stream',
      'Content-Length' => entity.size.to_s,
    }.update(options[:headers])

    options.update({
                     :verb => verb,
                     :params => [entity],
                     :headers => headers,
                   })

    page = fetch_page(options)
    add_to_history(page)
    page
  end

# File lib/mechanize.rb, line 197
  def set_proxy(addr, port, user = nil, pass = nil)
    @proxy_addr, @proxy_port, @proxy_user, @proxy_pass = addr, port, user, pass
  end

# File lib/mechanize.rb, line 366
  def submit(form, button=nil, headers={})
    form.add_button_to_query(button) if button
    case form.method.upcase
    when 'POST'
      post_form(form.action, form, headers)
    when 'GET'
      get(  :url      => form.action.gsub(/\?[^\?]*$/, ''),
            :params   => form.build_query,
            :headers  => headers,
            :referer  => form.page
            )
    else
      raise "unsupported method: #{form.method.upcase}"
    end
  end

# File lib/mechanize.rb, line 427
  def transact
    history_backup = @history.dup
    begin
      yield self
    ensure
      @history = history_backup
    end
  end

# File lib/mechanize.rb, line 203
  def user_agent_alias=(al)
    self.user_agent = AGENT_ALIASES[al] || raise("unknown agent alias")
  end

# File lib/mechanize.rb, line 413
  def visited?(url)
    ! visited_page(url).nil?
  end

# File lib/mechanize.rb, line 418
  def visited_page(url)
    if url.respond_to? :href
      url = url.href
    end
    @history.visited_page(resolve(url))
  end

# File lib/mechanize.rb, line 638
  def add_to_history(page)
    @history.push(page, resolve(page.uri))
    history_added.call(page) if history_added
  end

# File lib/mechanize.rb, line 470
  def fetch_page(params)
    options = {
      :request    => nil,
      :response   => nil,
      :connection => nil,
      :referer    => current_page(),
      :uri        => nil,
      :verb       => :get,
      :agent      => self,
      :redirects  => 0,
      :params     => [],
      :headers    => {},
    }.merge(params)

    before_connect = Chain.new([
                                Chain::URIResolver.new(@scheme_handlers),
                                Chain::ParameterResolver.new,
                                Chain::RequestResolver.new,
                                Chain::ConnectionResolver.new(
                                                              @connection_cache,
                                                              @keep_alive,
                                                              @proxy_addr,
                                                              @proxy_port,
                                                              @proxy_user,
                                                              @proxy_pass
                                                              ),
                                Chain::SSLResolver.new(@ca_file, @verify_callback, @cert, @key, @pass),
                                Chain::AuthHeaders.new(@auth_hash, @user, @password, @digest),
                                Chain::HeaderResolver.new(
                                                          @keep_alive,
                                                          @keep_alive_time,
                                                          @cookie_jar,
                                                          @user_agent,
                                                          @gzip_enabled,
                                                          @request_headers
                                                          ),
                                Chain::CustomHeaders.new,
                                @pre_connect_hook,
                               ])
    before_connect.handle(options)

    uri           = options[:uri]
    request       = options[:request]
    cur_page      = options[:referer]
    request_data  = options[:params]
    redirects     = options[:redirects]
    http_obj      = options[:connection]

    # Add If-Modified-Since if page is in history
    if( (page = visited_page(uri)) && page.response['Last-Modified'] )
      request['If-Modified-Since'] = page.response['Last-Modified']
    end if(@conditional_requests)

    http_obj.mu_lock
    # Specify timeouts if given
    http_obj.open_timeout = @open_timeout if @open_timeout
    http_obj.read_timeout = @read_timeout if @read_timeout
    http_obj.start unless http_obj.started?

    # Log specified headers for the request
    log.info("#{ request.class }: #{ request.path }") if log
    request.each_header do |k, v|
      log.debug("request-header: #{ k } => #{ v }")
    end if log

    # Send the request
    attempts = 0
    begin
      response = http_obj.request(request, *request_data) { |r|
        connection_chain = Chain.new([
                                      Chain::ResponseReader.new(r),
                                      Chain::BodyDecodingHandler.new,
                                     ])
        connection_chain.handle(options)
      }
    rescue EOFError, Errno::ECONNRESET, Errno::EPIPE => x
      log.error("Rescuing EOF error") if log
      http_obj.finish
      raise x if attempts >= 2
      request.body = nil
      http_obj.start
      attempts += 1
      retry
    end

    after_connect = Chain.new([
                               @post_connect_hook,
                               Chain::ResponseBodyParser.new(@pluggable_parser, @watch_for_set),
                               Chain::ResponseHeaderHandler.new(@cookie_jar, @connection_cache),
                              ])
    after_connect.handle(options)
    http_obj.mu_unlock

    res_klass = options[:res_klass]
    response_body = options[:response_body]
    page = options[:page]

    log.info("status: #{ page.code }") if log

    if follow_meta_refresh
      redirect_uri  = nil
      referer       = page
      if (page.respond_to?(:meta) && (redirect = page.meta.first))
        redirect_uri = redirect.uri.to_s
        sleep redirect.node['delay'].to_f
        referer = Page.new(nil, {'content-type'=>'text/html'})
      elsif refresh = response['refresh']
        delay, redirect_uri = Page::Meta.parse(refresh, uri)
        raise StandardError, "Invalid refresh http header" unless delay
        if redirects + 1 > redirection_limit
          raise RedirectLimitReachedError.new(page, redirects)
        end
        sleep delay.to_f
      end
      if redirect_uri
        @history.push(page, page.uri)
        return fetch_page(
                          :uri        => redirect_uri,
                          :referer    => referer,
                          :params     => [],
                          :verb       => :get,
                          :redirects  => redirects + 1
                          )
      end
    end

    return page if res_klass <= Net::HTTPSuccess

    if res_klass == Net::HTTPNotModified
      log.debug("Got cached page") if log
      return visited_page(uri) || page
    elsif res_klass <= Net::HTTPRedirection
      return page unless follow_redirect?
      log.info("follow redirect to: #{ response['Location'] }") if log
      from_uri  = page.uri
      raise RedirectLimitReachedError.new(page, redirects) if redirects + 1 > redirection_limit
      redirect_verb = options[:verb] == :head ? :head : :get
      page = fetch_page(  :uri => response['Location'].to_s,
                          :referer => page,
                          :params  => [],
                          :verb => redirect_verb,
                          :redirects => redirects + 1
                          )
      @history.push(page, from_uri)
      return page
    elsif res_klass <= Net::HTTPUnauthorized
      raise ResponseCodeError.new(page) unless @user || @password
      raise ResponseCodeError.new(page) if @auth_hash.has_key?(uri.host)
      if response['www-authenticate'] =~ /Digest/i
        @auth_hash[uri.host] = :digest
        if response['server'] =~ /Microsoft-IIS/
          @auth_hash[uri.host] = :iis_digest
        end
        @digest = response['www-authenticate']
      else
        @auth_hash[uri.host] = :basic
      end
      return fetch_page(  :uri      => uri,
                          :referer  => cur_page,
                          :verb     => request.method.downcase.to_sym,
                          :params   => request_data,
                          :headers  => options[:headers]
                          )
    end

    raise ResponseCodeError.new(page), "Unhandled response", caller
  end

# File lib/mechanize.rb, line 448
  def post_form(url, form, headers = {})
    cur_page = form.page || current_page ||
      Page.new( nil, {'content-type'=>'text/html'})

    request_data = form.request_data

    log.debug("query: #{ request_data.inspect }") if log

    # fetch the page
    page = fetch_page(  :uri      => url,
                        :referer  => cur_page,
                        :verb     => :post,
                        :params   => [request_data],
                        :headers  => {
                          'Content-Type'    => form.enctype,
                          'Content-Length'  => request_data.size.to_s,
                        }.merge(headers))
    add_to_history(page)
    page
  end

# File lib/mechanize.rb, line 440
  def resolve(url, referer = current_page())
    hash = { :uri => url, :referer => referer }
    chain = Chain.new([
                       Chain::URIResolver.new(@scheme_handlers)
                      ]).handle(hash)
    hash[:uri].to_s
  end