url links to zip packages

[wolnelektury.git] / apps / catalogue / utils.py

diff --git a/apps/catalogue/utils.py b/apps/catalogue/utils.py
index 02e5b6d..369656e 100644 (file)
--- a/apps/catalogue/utils.py
+++ b/apps/catalogue/utils.py
@@ -2,6 +2,8 @@
 # This file is part of Wolnelektury, licensed under GNU Affero GPLv3 or later.
 # Copyright © Fundacja Nowoczesna Polska. See NOTICE for more information.
 #
+from __future__ import with_statement
+
 import random
 import time
 from base64 import urlsafe_b64encode
@@ -9,6 +11,11 @@ from base64 import urlsafe_b64encode
 from django.core.files.uploadedfile import UploadedFile
 from django.utils.hashcompat import sha_constructor
 from django.conf import settings
+from celery.task import task
+from os import mkdir, path, unlink
+from errno import EEXIST, ENOENT
+from fcntl import flock, LOCK_EX
+from zipfile import ZipFile
 
 from librarian import DocProvider
 
@@ -49,13 +56,77 @@ class ExistingFile(UploadedFile):
 
 
 class BookImportDocProvider(DocProvider):
-    """ used for joined EPUBs """
+    """Used for joined EPUB and PDF files."""
 
     def __init__(self, book):
         self.book = book
-        
+
     def by_slug(self, slug):
         if slug == self.book.slug:
             return self.book.xml_file
         else:
-            return Book.objects.get(slug=slug).xml_file
+            return type(self.book).objects.get(slug=slug).xml_file
+
+
+class LockFile(object):
+    """
+    A file lock monitor class; createas an ${objname}.lock
+    file in directory dir, and locks it exclusively.
+    To be used in 'with' construct.
+    """
+    def __init__(self, dir, objname):
+        self.lockname = path.join(dir, objname + ".lock")
+
+    def __enter__(self):
+        self.lock = open(self.lockname, 'w')
+        flock(self.lock, LOCK_EX)
+
+    def __exit__(self, *err):
+        try:
+            unlink(self.lockname)
+        except OSError as oe:
+            if oe.errno != oe.EEXIST:
+                raise oe
+        self.lock.close()
+
+
+def create_zip(paths, zip_slug):
+    """
+    Creates a zip in MEDIA_ROOT/zip directory containing files from path.
+    Resulting archive filename is ${zip_slug}.zip
+    Returns it's path relative to MEDIA_ROOT (no initial slash)
+    """
+    # directory to store zip files
+    zip_path = path.join(settings.MEDIA_ROOT, 'zip')
+
+    try:
+        mkdir(zip_path)
+    except OSError as oe:
+        if oe.errno != EEXIST:
+            raise oe
+    zip_filename = zip_slug + ".zip"
+
+    with LockFile(zip_path, zip_slug):
+        if not path.exists(path.join(zip_path, zip_filename)):
+            with ZipFile(path.join(zip_path, zip_filename), 'w') as zipf:
+                for p in paths:
+                    zipf.write(p, path.basename(p))
+
+        return 'zip/' + zip_filename
+
+
+def remove_zip(zip_slug):
+    """
+    removes the ${zip_slug}.zip file from zip store.
+    """
+    zip_file = path.join(settings.MEDIA_ROOT, 'zip', zip_slug + '.zip')
+    try:
+        unlink(zip_file)
+    except OSError as oe:
+        if oe.errno != ENOENT:
+            raise oe
+
+
+@task
+def create_zip_task(*args):
+    return create_zip(*args)