Implement support for resultsets returned in multiple pages

2 files changed, 80 insertions, 20 deletions

diff --git a/GetIABooksActivity.py b/GetIABooksActivity.py
index 0ffaebf..4a08207 100755
--- a/GetIABooksActivity.py
+++ b/GetIABooksActivity.py
@@ -247,6 +247,8 @@ class GetIABooksActivity(activity.Activity):
             
         self.list_scroller = gtk.ScrolledWindow(hadjustment=None, vadjustment=None)
         self.list_scroller.set_policy(gtk.POLICY_AUTOMATIC, gtk.POLICY_AUTOMATIC)
+        vadjustment = self.list_scroller.get_vadjustment()
+        vadjustment.connect('value-changed', self.__vadjustment_value_changed_cb)
         self.list_scroller.add(self.listview)
         
         self.progressbar = gtk.ProgressBar() #TODO: Add a way to cancel download
@@ -268,6 +270,9 @@ class GetIABooksActivity(activity.Activity):
 
     def can_close(self):
         self._lang_code_handler.close()
+        if self.queryresults is not None:
+            self.queryresults.cancel()
+            self.queryresults = None
         return True
 
     def selection_cb(self, widget):
@@ -328,16 +333,16 @@ class GetIABooksActivity(activity.Activity):
         textbuffer = self.textview.get_buffer()
         textbuffer.set_text(_('Performing lookup, please wait...'))
 
-        self.queryresults.connect('completed', self.__query_completed_cb)
+        self.queryresults.connect('updated', self.__query_updated_cb)
 
-    def __query_completed_cb(self, query):
+    def __query_updated_cb(self, query, midway):
         self.listview.populate(self.queryresults)
 
         textbuffer = self.textview.get_buffer()
-        if len(self.queryresults) > 0:
-            textbuffer.set_text('')
-        else:
+        if len(self.queryresults) == 0:
             textbuffer.set_text(_('Sorry, no books could be found.'))
+        elif not midway:
+            textbuffer.set_text('')
 
     def __source_changed_cb(self, widget):
         search_terms = self._books_toolbar.get_search_terms()
@@ -346,6 +351,22 @@ class GetIABooksActivity(activity.Activity):
         else:
             self.find_books(search_terms)
 
+    def __vadjustment_value_changed_cb(self, vadjustment):
+
+        if not self.queryresults.is_ready():
+            return
+        try:
+            # Use various tricks to update resultset as user scrolls down
+            if ((vadjustment.props.upper - vadjustment.props.lower) > 1000 \
+                and (vadjustment.props.upper - vadjustment.props.value - \
+                vadjustment.props.page_size)/(vadjustment.props.upper - \
+                vadjustment.props.lower) < 0.3) or ((vadjustment.props.upper \
+                - vadjustment.props.value - vadjustment.props.page_size) < 200):
+                if self.queryresults.has_next():
+                    self.queryresults.update_with_next()
+        finally:
+            return
+
     def get_book(self):
         self._books_toolbar.enable_button(False)
         self.progressbar.show()
diff --git a/opds.py b/opds.py
index 0f20b37..389ee78 100644
--- a/opds.py
+++ b/opds.py
@@ -16,6 +16,7 @@
 # along with this program; if not, write to the Free Software
 # Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 
+import logging
 
 import feedparser
 import threading
@@ -23,6 +24,8 @@ import os
 
 import gobject
 
+_logger = logging.getLogger('get-ia-books-activity')
+
 _FEEDBOOKS_URI = 'http://feedbooks.com/books/search.atom?query='
 _INTERNETARCHIVE_URI = 'http://bookserver.archive.org/catalog/opensearch?q='
 
@@ -31,19 +34,22 @@ _REL_OPDS_ACQUISTION = u'http://opds-spec.org/acquisition'
 gobject.threads_init()
 
 class DownloadThread(threading.Thread):
-    def __init__(self, obj):
+    def __init__(self, obj, midway):
         threading.Thread.__init__ (self)
+        self.midway = midway
         self.obj = obj
         self.stopthread = threading.Event()
 
     def _download(self):
-        if not self.obj.is_local():
+        if not self.obj.is_local() and self.midway == False:
             feedobj = feedparser.parse(self.obj._uri + self.obj._queryterm.replace(' ', '+'))
         else:
             feedobj = feedparser.parse(self.obj._uri)
 
+        for entry in feedobj['entries']:
+            self.obj._booklist.append(Book(entry))
         self.obj._feedobj = feedobj
-        self.obj.emit('completed')
+        self.obj.emit('updated', self.midway)
         self.obj._ready = True
         
         return False
@@ -129,9 +135,9 @@ class Book(object):
 
 class QueryResult(gobject.GObject):
     __gsignals__ = {
-        'completed': (gobject.SIGNAL_RUN_FIRST,
+        'updated': (gobject.SIGNAL_RUN_FIRST,
                           gobject.TYPE_NONE,
-                          ([])),
+                          ([gobject.TYPE_BOOLEAN])),
     }
     def __init__(self, uri, queryterm):
         gobject.GObject.__init__(self)
@@ -139,16 +145,45 @@ class QueryResult(gobject.GObject):
         self._uri = uri
         self._queryterm = queryterm
         self._feedobj = None
+        self._next_uri = ''
         self._ready = False
 
+        self._booklist = []
+
         self.threads = []
-        
-        d_thread = DownloadThread(self)
+        self._start_download()
+       
+    def _start_download(self, midway = False):
+        d_thread = DownloadThread(self, midway)
         self.threads.append(d_thread)
         d_thread.start()
 
     def __len__(self):
-        return len(self._feedobj['entries'])
+        return len(self._booklist)
+
+    def has_next(self):
+        '''
+        Returns True if more result pages are 
+        available for the resultset
+        '''
+        if not self._feedobj['feed'].has_key('links'):
+            return False
+        for link in self._feedobj['feed']['links']:
+            if link['rel'] == u'next':
+                self._next_uri = link['href']
+                return True
+
+        return False
+
+    def update_with_next(self):
+        '''
+        Updates the booklist with the next resultset
+        '''
+        if len(self._next_uri) > 0:
+            self._ready = False
+            self._uri = self._next_uri
+            self.cancel() #XXX: Is this needed ?
+            self._start_download(midway = True)
 
     def cancel(self):
         '''
@@ -157,18 +192,22 @@ class QueryResult(gobject.GObject):
         for d_thread in self.threads:
             d_thread.stop()
 
-
     def get_book_n(self, n):
-        return Book(self._feedobj['entries'][n])
+        '''
+        Gets the n-th book
+        '''
+        return self._booklist[n]
 
     def get_book_list(self):
-        ret = []
-        for entry in self._feedobj['entries']:
-            ret.append(Book(entry))
-
-        return ret
+        '''
+        Gets the entire booklist
+        '''
+        return self._booklist
 
     def is_ready(self):
+        '''
+        Returns False if a query is in progress
+        '''
         return self._ready
 
     def is_local(self):