add hardest cards plugin

hardest.py

@@ -0,0 +1,48 @@
+# -*- coding: utf-8 -*-
+# Copyright: Damien Elmes <anki@ichi2.net>
+# License: GNU GPL, version 3 or later; http://www.gnu.org/copyleft/gpl.html
+#
+# This simple plugin shows you the hardest cards in the defined time (default
+# last 30 minutes).
+#
+
+from PyQt4.QtGui import *
+from PyQt4.QtCore import *
+from ankiqt import mw
+import time
+
+# last 30 minutes
+MINUTES = 30
+# limit to maximum of 10 cards
+MAXCARDS = 10
+
+def onHardest():
+    data = mw.deck.s.all("""
+select question, cnt from (
+select cardId, count() as cnt from reviewHistory where time > :t
+and ease = 1 group by cardId), cards where cardId = id order by cnt desc limit :d""",
+                         t=time.time() - 60*MINUTES, d=MAXCARDS)
+
+    s = "<h1>Hardest Cards</h1><table>"
+    for (q, cnt) in data:
+        s += "<tr><td>%s</td><td>failed %d times</td></tr>" % (q, cnt)
+    # show dialog
+    diag = QDialog(mw.app.activeWindow())
+    diag.setWindowTitle("Anki")
+    layout = QVBoxLayout(diag)
+    diag.setLayout(layout)
+    text = QTextEdit()
+    text.setReadOnly(True)
+    text.setHtml(s)
+    layout.addWidget(text)
+    box = QDialogButtonBox(QDialogButtonBox.Close)
+    layout.addWidget(box)
+    mw.connect(box, SIGNAL("rejected()"), diag, SLOT("reject()"))
+    diag.setMinimumHeight(400)
+    diag.setMinimumWidth(500)
+    diag.exec_()
+
+a = QAction(mw)
+a.setText("Show Hardest Cards")
+mw.mainWin.menuTools.addAction(a)
+mw.connect(a, SIGNAL("triggered()"), onHardest)