text: """Context class."""
  
  import History
  import Reader
  import string
  import grailutil
  import time
  import math
  import urllib
  import regsub
  
  from Cursors import *
  from grailbase.uricontext import URIContext
  from urlparse import urljoin, urlparse, urlunparse, urldefrag
  
  
  VALID_TARGET_STARTS = string.letters + '_'
  
  # TBD: horrible hack.  search down for reason. -bwarsaw
  LAST_CONTEXT = None
  
  
  class Context(URIContext):
  
      """Context for browsing operations.
      
      RATIONALE: After much thinking we uncovered the need for a
      separate object to hold the browsing context.  This contains items
      like the history stack (for the back/forward commands), the loaded
      URL (for the reload command), the base URL (for interpreting
      relative links), and probably more.  These used to be stored in
      the browser object, but when introducing frames, each frame will
      need its own context.  Storing the context in the viewer won't
      work either: table cells will be implemented as viewer objects,
      but share their browsing context with the containing frame.
  
      Resorting to viewer subclasses, some of which would maintain their
      own context and some of which wouldn't, would require overriding
      the anchor operations (which need the context) of the context-less
      viewers.  Having a pointer to a context object in all viewers
      makes this much simpler.
  
      """
  
      def __init__(self, viewer, browser):
          URIContext.__init__(self)
          self.viewer = viewer
          self.browser = browser
          self.history = History.History()
          self.history_dialog = None
          self.app = browser.app
          self.root = self.browser.root   # XXX Really a Toplevel instance
          self.readers = []
          self.page = None
          self.future = -1
          self.source = None
          self._target = None
          self.last_status_update = 0.0   # Time when last status update was done
          self.next_status_update = None  # ID of next scheduled status update
          self.show_source = 0
          self.applet_group = None
          self.notifications = []         # callbacks when no readers left
          self.image_maps = {}            # For ImageMap
          self.set_headers({})
          self.set_postdata(None)
          self.local_api_handlers = {}    # This pages local API handlers
  
      def register_notification(self, callback):
          if callback not in self.notifications:
              self.notifications.append(callback)
  
      def unregister_notification(self, callback):
          if callback in self.notifications:
              self.notifications.remove(callback)
  
      def notify(self):
          for callback in self.notifications:
              callback(self)
  
      def clear_reset(self):
          self.viewer.clear_reset()
          if self.on_top():
              self.browser.clear_reset()
          self.set_url("")
  
      def on_top(self):
          return self.browser.context is self
  
      def set_headers(self, headers):
          self.__headers = headers
  
      def get_headers(self):
          return self.__headers
  
      def set_postdata(self, data=None):
          self.__postdata = data
  
      def get_postdata(self):
          return self.__postdata
  
      # Load URL, base URL and target
  
      def set_url(self, url, baseurl=None, target=None, histify=1):
          """Set loaded URL, base URL and target for the current page.
  
          The loaded URL is what this page was loaded from; the base URL
          is used to calculate relative links, and defaults to the
          loaded URL.  The target is the default viewer name
          where followed links will appear, and defaults to this viewer.
  
          HISTIFY flag, if true, adds the URL to the history stack.
  
          """
          if url and histify:
              # don't lose title if we have one:
              title, when = self.app.global_history.lookup_url(url)
              self.app.global_history.remember_url(url, title or '')
              if not self.page:
                  self.page = History.PageInfo(url)
                  self.history.append_page(self.page)
              else:
                  self.page.set_url(url)
                  self.page.set_title("") # Will be reset from fresh HTML
                  self.history.refresh()
          else:
              if self.future >= 0:
                  self.page = self.history.page(self.future)
                  self.future = -1
              else:
                  self.page = None
          URIContext.set_url(self, url, baseurl=baseurl)
          self._target = target
          if self.on_top():
              self.browser.set_url(self.get_url())
          self.applet_group = None
  
      def set_baseurl(self, baseurl=None, target=None):
          """Set the base URL and target for the current page.
  
          The base URL is taken relative to the existing base URL.
  
          """
          URIContext.set_baseurl(self, baseurl)
          if target:
              self._target = target
  
      def get_target(self):
          """Return the default target for this page (which may be None)."""
          return self._target
  
      def follow(self, url, target="", histify=1, scrollpos=None):
          """Follow a link, given by a relative URL.
  
          If the relative URL is a fragment id (#name) on the current
          URL, scroll there; otherwise, do a full load of a new page.
  
          """
  
          newurl, frag = urldefrag(url)
          current, f = urldefrag(self.get_url())
          if newurl == current:
              # XXX This is not correct if we got here through a POST.
              context = self.find_window_target(target)
              if context is self:
                  self.follow_local_fragment(url, newurl, frag, histify)
                  return
          self.load(self.get_baseurl(url), target=(target or self._target),
                    scrollpos=scrollpos)
  
      def follow_local_fragment(self, url, newurl, frag, histify):
          if self.readers:
              self.readers[-1].fragment = frag
          if frag:
              self.viewer.scroll_to(frag)
          else:
              self.viewer.scroll_to_position(self.page.scrollpos())
              self.viewer.clear_selection()
          self.viewer.remove_temp_tag(histify=1)
          baseurl = self.get_baseurl(url)
          page = self.page
          self.page = None # triggers set_url() to update history
          self.set_url(baseurl, histify=histify)
          if self.future >= 0:
              self.page = self.history.page(self.future)
              self.future = -1
          self.page.set_title(page.title())
          self.history.refresh()
          self.browser.set_title(page.title())
  
      # Misc
  
      def get_formdata(self):
          return self.page and self.page.formdata()
  
      # Message interfaces
  
      def message(self, string=""):
          self.viewer.message(string)
      enter = message                     # XXX ImageMap backward compatibility
  
      def message_clear(self):
          self.new_reader_status()
      leave = message_clear               # XXX ImageMap backward compatibility
  
      def new_reader_status(self):
          if self.app.iostatuspanel:
              self.app.iostatuspanel.update()
          now = time.time()
          seconds = math.floor(now)
          if self.last_status_update == seconds:
              if self.next_status_update:
                  return
              self.next_status_update = self.browser.root.after(
                  1000 - int(1000*(now%1.0)),
                  self.new_reader_status)
              return
          self.last_status_update = seconds
          self.next_status_update = None
          if self.readers:
              nr = len(self.readers)
              nw = 0
              if nr == 1:
                  message = str(self.readers[0])
              else:
                  nbytes = 0
                  maxbytes = 0
                  cached = 0
                  for reader in self.readers:
                      nbytes = nbytes + reader.nbytes
                      if reader.message == "waiting for socket":
                          nw = nw + 1
                      if reader.maxbytes > 0 and maxbytes >= 0:
                          maxbytes = maxbytes + reader.maxbytes
                      else:
                          maxbytes = -1
                      if reader.api.iscached():
                          cached = cached + 1
                  if maxbytes > 0:
                      percent = nbytes*100/maxbytes
                      message = "%d%% of %s read" % (
                          percent, grailutil.nicebytes(maxbytes))
                  else:
                      message = "%s read" % grailutil.nicebytes(nbytes)
                  if cached == nr:
                      message = message + " (all cached)"
                  elif cached:
                      message = message + " (%d cached)" % cached
                  message = "%d streams, %d active: %s" % (nr, nr - nw, message)
          elif self.on_top():
              message = ""
          elif self.get_url():
              message = "URL: %s" % self.get_url()
          else:
              message = "empty"
          self.message(message)
  
      def error_dialog(self, exception, msg):
          if self.app:
              self.app.error_dialog(exception, msg, root=self.root)
          else:
              print "ERROR:", msg
  
      def set_title(self, title):
          if not title:
              title, when = self.app.global_history.lookup_url(self.get_url())
              title = title or ''
          self.app.global_history.remember_url(self.get_url(), title)
          if self.on_top():
              self.browser.set_title(title)
          if self.page:
              self.page.set_title(title)
              self.history.refresh()
  
      # Handle (a)synchronous images
  
      def get_image(self, src):
          image = self.get_async_image(src)
          if image:
              if not image.load_synchronously(self):
                  image = None
          return image
  
      def get_async_image(self, src, reload=0, width=0, height=0):
          # check out the request
          if not src: return None
          url = self.get_baseurl(src)
          if not url: return None
          if not self.app.load_images: return None
  
          # try loading from the cache
          image = self.app.get_cached_image((url, width, height))
          if image and (not reload or image.is_reloading()):
              if not image.loaded:
                  image.start_loading(self)
              return image
  
          # it's not in the cache.
          from AsyncImage import AsyncImage
          try:
              image = AsyncImage(self, url, reload, width=width, height=height,
                                 master=self.root)
          except IOError, msg:
              image = None
          if image:
              self.app.set_cached_image(
                  image.get_cache_key(), image, self.viewer)
              if self.app.load_images:
                  image.start_loading(self)
          return image
  
      # Navigation/history commands
  
      def go_back(self, event=None):
          if not self.load_from_history(self.history.peek(-1)):
              if self.viewer.parent:
                  # Remove any local API handlers
                  self.viewer.parent.context.remove_local_api_handlers()
                  # go out one level:
                  self.viewer.parent.context.go_back(event)
              else:
                  self.root.bell()
  
      def go_forward(self, event=None):
          self.load_from_history(self.history.peek(+1))
  
      def reload_page(self):
          self.load_from_history(self.history.peek(0), reload=1)
  
      def load_from_history(self, (future, page), reload=0):
          if not page:
              return 0
          self.future = future
          if not reload:
              self.follow(page.url(), histify=0, scrollpos=page.scrollpos(),
                          target="_self")
          else:
              self.load(page.url(), reload=reload, scrollpos=page.scrollpos(),
                        target="_self")
          return 1
  
      def show_history_dialog(self):
          if not self.history_dialog:
              self.history_dialog = History.HistoryDialog(self, self.history)
              self.history.set_dialog(self.history_dialog)
          else:
              self.history_dialog.show()
  
      def clone_history_from(self, other):
          self.history = other.history.clone()
          self.future, page = self.history.peek()
          if page:
              self.load(page.url(), scrollpos=page.scrollpos())
  
      # Internals handle loading pages
  
      def save_page_state(self, reload=0):
          if not self.page: return
          # Save page scroll position
          self.page.set_scrollpos(self.viewer.scrollpos())
          # Save form contents even if reloading
          formdata = []
          if hasattr(self, 'forms'):
              for fi in self.forms:
                  formdata.append(fi.get())
              # remove the attribute
              del self.forms
          self.page.set_formdata(formdata)
  
      def read_page(self, url, method, params, show_source=0, reload=0,
                    scrollpos=None, data=None):
          # TBD: this is a horrid hack used so that
          # mailtoAPI.mailto_access can get at the URL of the page that
          # the user has clicked off of. -baw
          self.set_postdata(data)
          global LAST_CONTEXT
          LAST_CONTEXT = self
          from Reader import Reader
          Reader(self, url, method, params, show_source, reload, data, scrollpos)
  
      # Applet Protocol Handler interface
      
      def set_local_api(self, name, klass):
          """Install a local protocol handler"""
          if name[-3:] <> "API":
              raise IOError, "Invalid name (%s) for protocol handler"
          self.local_api_handlers[name] = klass
  
      def get_local_api(self, url, method, params):
          """get a local handler instance"""
          scheme, resturl = urllib.splittype(url)
          if not scheme:
              raise IOError, ("protocol error",
                              "no scheme identifier in URL", url)
          scheme = string.lower(scheme)
          sanitized = regsub.gsub("[^a-zA-Z0-9]", "_", scheme)
          modname = sanitized + "API"
          try:
              klass  = self.local_api_handlers[modname]
          except KeyError:
              return None
          handler = klass(resturl, method, params)
          handler._url_ = url # To keep BaseReader happy
          return handler
  
      def remove_local_api_handlers(self):
          """Remove any local handlers from the current context"""
          if self.local_api_handlers:
              self.local_api_handlers = {}
  
  
      # External user commands
  
      def save_document(self, *relurls):
          """Save document to a file.
  
          Returns true if the x-fer was initiated; allows histification.
          """
          # File/Save As...
          url = apply(self.get_baseurl, relurls)
          if url == self.get_url() and self.busycheck(): return 0
          import FileDialog, os
          fd = FileDialog.SaveFileDialog(self.root)
          # give it a default filename on which save within the
          # current directory
          import urllib
          if urllib.splittype(url)[0] == "data":
              default = ""
          else:
              urlasfile = string.splitfields(url, '/')
              default = urlasfile[-1]
              # strip trailing query
              i = string.find(default, '?')
              if i > 0: default = default[:i]
              # strip trailing fragment
              i = string.rfind(default, '#')
              if i > 0: default = default[:i]
              # maybe bogus assumption?
              if not default: default = 'index.html'
          file = fd.go(default=default, key="save")
          if not file: return 0
          #
          SavingReader(self, url, 'GET', {}, 0, 0, filename=file)
          self.message_clear()
          return 1
  
      def print_document(self):
          # File/Print...
          if self.busycheck(): return
          import PrintDialog
          PrintDialog.PrintDialog(self,
                                  self.get_url(),
                                  self.get_title())
  
      def view_source(self):
          from Browser import Browser
          browser = Browser(self.app.root, self.app, height=24)
          browser.context.load(self.get_url(), show_source=1)
  
      # Externals for loading pages
  
      def load(self, url, method='GET', params={},
               show_source=0, reload=0, scrollpos=None,
               target="", source=None):
          # Update state of current page, in case we re-visit it via the
          # history mechanism.
          if not source:
              source = self.viewer
          if self.source and self.source is not source:
              self.source.remove_temp_tag()
          self.source = source
          context = self.find_window_target(target)
          if context is not self:
              context.load(url, method, params, show_source,
                           reload, scrollpos, "_self", source)
              return
          self.stop()
          self.save_page_state()
          # Start loading a new URL into the window
          self.message("Loading %s" % url)
          if reload:
              show_source = self.show_source
          else:
              self.show_source = show_source
          try:
              self.read_page(url, method, params,
                             show_source=show_source, reload=reload,
                             scrollpos=scrollpos)
              self.show_source = show_source
          except IOError, msg:
              self.error_dialog(IOError, msg)
              self.message_clear()
              if self.source:
                  self.source.remove_temp_tag()
                  self.source = None
  
      def find_window_target(self, target):
          """Return a context gotten from the target; by default self."""
          context = None
          if target and target[0] not in VALID_TARGET_STARTS:
              target = ""
          if target == self.viewer.name:
              target = ""
          if target:
              if target[0] == "_":
                  if target == "_blank":
                      newbrowser = self.browser.new_command()
                      context = newbrowser.context
                  elif target == "_self":
                      pass
                  elif target == "_parent":
                      parentviewer = self.viewer.find_parentviewer()
                      context = parentviewer and parentviewer.context
                  elif target == "_top":
                      context = self.browser.context
                  target = ""
              else:
                  # First try to find the target in the current browser
                  viewer = self.browser.context.viewer.find_subviewer(target)
                  if not viewer:
                      # Try to find another browser with this name
                      for browser in self.app.browsers:
                          if browser.viewer.name == target:
                              viewer = browser.viewer
                              break
                  if not viewer:
                      # Try to find a frame inside other browsers
                      for browser in self.app.browsers:
                          if browser is self.browser: continue
                          viewer = browser.context.viewer.find_subviewer(target)
                          if viewer:
                              break
                  if not viewer:
                      # Create a new browser with this name
                      newbrowser = self.browser.new_command()
                      viewer = newbrowser.context.viewer
                      viewer.name = target # XXX Naughty ;-)
                  context = viewer.context
          if context and context is not self:
              context.source = self.source
              self.source = None
          return context or self
  
      def post(self, url, data="", params={}, target=""):
          # Post form data
          context = self.find_window_target(target)
          if context is not self:
              context.post(url, data, params, target)
              return
          self.stop()
          self.save_page_state()
          url = self.get_baseurl(url)
          method = 'POST'
          self.message("Posting to %s" % url)
          try:
              self.read_page(url, method, params, reload=1, data=data)
          except IOError, msg:
              self.error_dialog(IOError, msg)
              self.message_clear()
  
      # Externals for managing list of active readers
  
      def addreader(self, reader):
          self.readers.append(reader)
          if self.on_top():
              self.browser.allowstop()
          self.new_reader_status()
  
      def rmreader(self, reader):
          if reader in self.readers:
              self.readers.remove(reader)
          if not self.readers:
              if self.on_top():
                  self.browser.clearstop()
              if self.source:
                  self.source.remove_temp_tag(histify=1)
                  self.source = None
              self.notify()
          self.new_reader_status()
  
      def busy(self):
          return not not self.readers
  
      def busycheck(self):
          if self.readers:
              self.error_dialog('Busy',
                  "Please wait until the transfer is done (or stop it)")
              return 1
          return 0
  
      def stop(self):
          for reader in self.readers[:]:
              reader.kill()
  
      # Page interface
  
      def get_title(self):
          url = self.get_url()
          title, when = self.app.global_history.lookup_url(url)
          if not title:
              title = self.page and self.page.title() or url
          return title
  
  
  
  
  class SimpleContext(Context):
      # this can be used when interactive updates are not desired
      def new_reader_status(self): pass
      def on_top(self): return 0
  
  
  
  class SavingReader(Reader.Reader):
      def __init__(self, context, url, *args, **kw):
          self.__filename = kw['filename']
          del kw['filename']
          apply(Reader.Reader.__init__, (self, context, '') + args, kw)
          context.rmreader(self)
          self.url = url
          self.restart(url)
  
      def handle_meta(self, errcode, errmsg, headers):
          if not self.handle_meta_prelim(errcode, errmsg, headers):
              return
          # now save:
          self.stop()
          try:
              self.save_file = open(self.__filename, "wb")
          except IOError, msg:
              self.context.error_dialog(IOError, msg)
              return
          #
          # add to history without destroying any title already known:
          #
          history = grailutil.get_grailapp().global_history
          title, when = history.lookup_url(self.url)
          history.remember_url(self.url, title or '')
          #
          Reader.TransferDisplay(self.last_context, self.__filename, self)
  