From cf3553175ff5adb09881d79314c6e4162104bc70 Mon Sep 17 00:00:00 2001
From: I-Al-Istannen <i-al-istannen@users.noreply.github.com>
Date: Thu, 27 Feb 2020 14:51:29 +0100
Subject: [PATCH] Add OS_Exams synchronizer

---
 PFERD/__init__.py |  2 ++
 PFERD/os_exams.py | 85 +++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 87 insertions(+)
 create mode 100644 PFERD/os_exams.py

diff --git a/PFERD/__init__.py b/PFERD/__init__.py
index fd85843..a0e924c 100644
--- a/PFERD/__init__.py
+++ b/PFERD/__init__.py
@@ -6,6 +6,7 @@ from .norbert import *
 from .tgi import *
 from .tgi_jimbo import *
 from .ti import *
+from .os_exams import *
 from .utils import *
 
 __all__ = ["STYLE", "FORMAT", "DATE_FORMAT", "FORMATTER", "enable_logging"]
@@ -17,6 +18,7 @@ __all__ += tgi.__all__
 __all__ += tgi_jimbo.__all__
 __all__ += ti.__all__
 __all__ += utils.__all__
+__all__ += os_exams.__all__
 
 STYLE = "{"
 FORMAT = "[{levelname:<7}] {message}"
diff --git a/PFERD/os_exams.py b/PFERD/os_exams.py
new file mode 100644
index 0000000..45b3881
--- /dev/null
+++ b/PFERD/os_exams.py
@@ -0,0 +1,85 @@
+# Operating systems Exams
+
+import getpass
+import logging
+import pathlib
+import re
+
+import bs4
+import requests
+
+from .organizer import Organizer
+from .utils import stream_to_path, PrettyLogger
+
+__all__ = ["OsExams"]
+logger = logging.getLogger(__name__)
+pretty = PrettyLogger(logger)
+
+class OsExams:
+    BASE_URL = "https://os.itec.kit.edu/deutsch/1556.php"
+    LINK_RE = re.compile(
+            r"^http://os.itec.kit.edu/downloads_own/sysarch-exam-assandsols"
+            r".*/(.*\.pdf)$"
+            )
+
+    _credentials = None
+
+    def __init__(self, base_path):
+        self.base_path = base_path
+
+        self._session = requests.Session()
+
+    def synchronize(self, to_dir, transform=lambda x: x):
+        pretty.starting_synchronizer(to_dir, "OsExams")
+
+        sync_path = pathlib.Path(self.base_path, to_dir)
+
+        orga = Organizer(self.base_path, sync_path)
+        orga.clean_temp_dir()
+
+        self._crawl(orga, transform)
+
+        orga.clean_sync_dir()
+        orga.clean_temp_dir()
+
+    def _crawl(self, orga, transform):
+        url = self.BASE_URL
+        r = self._session.get(url)
+        soup = bs4.BeautifulSoup(r.text, "html.parser")
+
+        for found in soup.find_all("a", href=self.LINK_RE):
+            url = found["href"]
+            filename = re.match(self.LINK_RE, url).group(1).replace("/", ".")
+            logger.debug(f"Found file {filename} at {url}")
+
+            old_path = pathlib.PurePath(filename)
+            new_path = transform(old_path)
+            if new_path is None:
+                continue
+            logger.debug(f"Transformed from {old_path} to {new_path}")
+
+            temp_path = orga.temp_file()
+            self._download(url, temp_path)
+            orga.add_file(temp_path, new_path)
+
+    def _download(self, url, to_path):
+        while True:
+            username, password = self._get_credentials()
+            with self._session.get(url, stream=True, auth=(username, password)) as r:
+                if r.ok:
+                    stream_to_path(r, to_path)
+                    return
+                else:
+                    print("Incorrect credentials.")
+                    self._reset_credentials()
+
+    def _get_credentials(self):
+        if self._credentials is None:
+            print("Please enter OS credentials.")
+            username = getpass.getpass(prompt="Username: ")
+            password = getpass.getpass(prompt="Password: ")
+            self._credentials = (username, password)
+        return self._credentials
+
+    def _reset_credentials(self):
+        self._credentials = None