+    def populate_dc(self):
+        from librarian.parser import WLDocument
+        wldoc = WLDocument.from_file(self.xml_file.path)
+        self.dc = wldoc.book_info.to_dict()
+        self.type = self.dc["type"]
+        assert self.type in ('appendix', 'course', 'synthetic', 'project', 'added', 'added-var'), \
+            u"Unknown lesson type: %s" % self.type
+        self.save()
+
+        courses = set()
+        for identifier in wldoc.book_info.curriculum:
+            identifier = (identifier or "").replace(' ', '')
+            if not identifier:
+                continue
+            try:
+                curr = Curriculum.objects.get(identifier__iexact=identifier)
+            except Curriculum.DoesNotExist:
+                logging.warn('Unknown curriculum course %s in lesson %s' % (identifier, self.slug))
+                pass
+            else:
+                courses.add(curr.course)
+        self.curriculum_courses = courses
+
+    def populate_description(self, wldoc=None, infile=None):
+        if wldoc is None:
+            wldoc = self.wldocument(infile)
+        if self.type == 'project':
+            lookup = u'Zadanie'
+        else:
+            lookup = u'Pomysł na lekcję'
+        for header in wldoc.edoc.findall('.//naglowek_rozdzial'):
+            if (header.text or '').strip() == lookup:
+                from lxml import etree
+                self.description = etree.tostring(
+                    header.getnext(), method='text', encoding='unicode').strip()
+                self.save()
+                return
+
+    def wldocument(self, infile=None):
+        from librarian import IOFile
+        from librarian.parser import WLDocument
+        from .publish import OrmDocProvider
+
+        if infile is None:
+            infile = IOFile.from_filename(self.xml_file.path)
+            for att in self.attachment_set.all():
+                infile.attachments["%s.%s" % (att.slug, att.ext)] = \
+                    IOFile.from_filename(att.file.path)
+        return WLDocument(infile, provider=OrmDocProvider())
+
+    def build_html(self, infile=None):
+        from .publish import HtmlFormat
+        wldoc = self.wldocument(infile)
+        html = HtmlFormat(wldoc).build()
+        self.html_file.save("%s.html" % self.slug, File(open(html.get_filename())))
+
+    def build_pdf(self, student=False):
+        from .publish import PdfFormat
+        # PDF uses document with attachments already saved as media,
+        # otherwise sorl.thumbnail complains about SuspiciousOperations.
+        wldoc = self.wldocument()
+        if student:
+            pdf = PdfFormat(wldoc).build()
+            self.student_pdf.save("%s.pdf" % self.slug, File(open(pdf.get_filename())))
+        else:
+            pdf = PdfFormat(wldoc, teacher=True).build()
+            self.pdf.save("%s.pdf" % self.slug, File(open(pdf.get_filename())))
+
+    def add_to_zip(self, zipf, student=False, prefix=''):
+        pdf = self.student_pdf if student else self.pdf
+        if pdf:
+            zipf.write(pdf.path, "%s%s%s.pdf" % (prefix, self.slug, "_student" if student else ""))
+            for attachment in self.attachment_set.all():
+                zipf.write(attachment.file.path, u"%smaterialy/%s.%s" % (prefix, attachment.slug, attachment.ext))
+            zipf.write(self.xml_file.path, "%spliki-zrodlowe/%s.xml" % (prefix, self.slug))
+
+    def build_package(self, student=False):
+        from StringIO import StringIO
+        import zipfile
+        from django.core.files.base import ContentFile
+        buff = StringIO()
+        zipf = zipfile.ZipFile(buff, 'w', zipfile.ZIP_STORED)
+        self.add_to_zip(zipf, student)
+        zipf.close()
+        fieldname = "student_package" if student else "package"
+        getattr(self, fieldname).save(
+            "%s%s.zip" % (self.slug, "_student" if student else ""),
+            ContentFile(buff.getvalue()))
+
+    def get_syntetic(self):
+        if self.section is None:
+            return None
+        return self.section.syntetic_lesson(self.level)
+
+    def get_other_level(self):
+        if self.section is None:
+            return None
+        other_levels = self.section.lesson_set.exclude(level=self.level)
+        if other_levels.exists():
+            return other_levels[0].level
+
+    def get_previous(self):
+        if self.section is None:
+            return None
+        try:
+            return self.section.lesson_set.filter(
+                type=self.type, level=self.level,
+                order__lt=self.order).order_by('-order')[0]
+        except IndexError:
+            return None
+
+    def get_next(self):
+        if self.section is None:
+            return None
+        try:
+            return self.section.lesson_set.filter(
+                type=self.type, level=self.level,
+                order__gt=self.order).order_by('order')[0]
+        except IndexError:
+            return None
+
+    def requires_internet(self):
+        return 'internet' in self.dc.get('requires', [])
+