Refactor calvin.py

calvin/calvin.py

@@ -8,109 +8,112 @@
 import mimetypes
 
 
-CALVIN_URL = r'http://www.gocomics.com/calvinandhobbes/'
-
-IMAGE_REGEX = re.compile(r'(http://cdn.svcs.c2.uclick.com/c2/\w{32})\?width')
-
-DATE_REGEX = re.compile(r'Calvin and Hobbes Comic Strip, (\w+ \d{1,2}, \d{4})')
-
-DATE_FORMAT='%Y-%m-%d'
+CALVIN = {
+    'url': r'http://www.gocomics.com/calvinandhobbes/',
+    'image': re.compile(r'(http://cdn.svcs.c2.uclick.com/c2/\w{32})\?width'),
+    'date': re.compile(r'Calvin and Hobbes Comic Strip, (\w+ \d{1,2}, \d{4})'),
+}
 
-HEADERS = {
+REQUEST_HEADRES = {
     'User-Agent': r'Mozilla/5.0 (X11; Linux i686; rv:9.0.1) Gecko/20100101 Firefox/9.0.1',
 }
 
 
-def parse_date(text, default=None):
-    return datetime.datetime.strptime(text, DATE_FORMAT).date() if text is not None else default
+class CalvinError(Exception):
+    pass
 
-def input_interval():
-    _, start, end, *_ = sys.argv + [None, None]
-    today = datetime.date.today()
-    return parse_date(start, today), parse_date(end, today)
+class SaveError(Exception):
+    pass
 
-def date_range(start, end):
-    for i in range(start.toordinal(), end.toordinal() + 1):
-        yield datetime.date.fromordinal(i)
+class NotAvailable(Exception):
+    pass
 
-def read_url(url):
-    request = urllib.request.Request(url=url, headers=HEADERS)
-    with urllib.request.urlopen(request) as response:
-        return response.read(), response.getheader('Content-Type')
+class Skip(Exception):
+    pass
 
-def read_page(date):
-    content, _ = read_url(CALVIN_URL+date.strftime('%Y/%m/%d'))
-    return content.decode()
 
-def comic_date(page):
-    match = DATE_REGEX.search(page)
-    return datetime.datetime.strptime(match.group(1), '%B %d, %Y').date() if match else None
+def date(text):
+    return datetime.datetime.strptime(text, '%Y-%m-%d')
 
-def image_url(page):
-    match = IMAGE_REGEX.search(page)
-    return match.group(1) if match else None
+def replay():
+    log_state = {}
+    with open('log', 'r') as log:
+        for line in log:
+            date_text, url, ext = line.split()
+            log_state[date(date_text)] = date_text + ext if ext != 'None' else None
+    return open('log', 'a'), log_state
 
-def save_image(url, date):
-    content, content_type = read_url(url)
-    ext = (['.unknown'] + mimetypes.guess_all_extensions(content_type))[-1]
-    fname = date.strftime(DATE_FORMAT) + ext
-    if os.path.exists(fname):
-        return
-    with open(fname, 'wb') as file:
+def read(url):
+    global REQUEST_HEADERS
+    request = urllib.request.Request(url=url, headers=REQUEST_HEADRES)
+    with urllib.request.urlopen(request) as response:
+        content_type = response.getheader('Content-Type')
+        ext = ([None] + mimetypes.guess_all_extensions(content_type))[-1]
+        return response.read(), content_type, ext
+
+def find(date):
+    page = read(CALVIN['url'] + date.strftime('%Y/%m/%d'))[0].decode()
+    date_match = CALVIN['date'].search(page)
+    if not date_match:
+        raise CalvinError('No date')
+    page_date = datetime.datetime.strptime(date_match.group(1), '%B %d, %Y').date()
+    if page_date != date:
+        raise NotAvailable
+    image_match = CALVIN['image'].search(page)
+    if not image_match:
+        raise CalvinError('No image')
+    image_url = image_match.group(1)
+    return image_url
+
+def save(image_url, date):
+    (content, content_type, ext) = read(image_url)
+    path = date.strftime('%Y-%m-%d') + (ext or '')
+    if os.path.exists(path):
+        raise SaveError('File exists')
+    with open(path, 'wb') as file:
         file.write(content)
     return ext
 
-
-# replay log
-with open('log', 'r') as LOG:
-    LOG_STATE = {}
-    for line in LOG:
-        text_date, url, ext = line.split()
-        LOG_STATE[parse_date(text_date)] = text_date + ext if ext != 'None' else None
-
-# reopen log
-LOG = open('log', 'a')
-
-
-def got_date(date):
-    print(date, end=' ')
-    sys.stdout.flush()
-
-def got_already():
-    print('skip')
-
-def got_no_image(date):
-    if date in LOG_STATE and LOG_STATE[date] is not None:
-        print(date, None, None, file=LOG)
-    print('None')
-
-def got_url():
-    print('.', end='')
-    sys.stdout.flush()
-
-def got_image(date, url, ext):
-    if not ext:
-        print(' file exists')
+def proceed(date, log_state):
+    if date not in log_state:
         return
-    print(date, url, ext, file=LOG)
-    print(' ok')
+    if not log_state[date]:
+        raise NotAvailable
+    if log_state[date] and os.path.exists(log_state[date]):
+            raise Skip
+
+def download(last, end, log):
+    log_file, log_state = log
+    for ord in range(last.toordinal() + 1, end.toordinal() + 1):
+        date = datetime.date.fromordinal(ord)
+        date_text = date.strftime('%Y-%m-%d')
+        print(date_text, end=' ')
+        sys.stdout.flush() # it'd be nice if the reporter was contextmanager
+        try:
+            proceed(date, log_state)
+            image_url = find(date)
+            ext = save(image_url, date)
+            print(date_text, image_url, ext, file=log_file)
+            print('ok')
+        except CalvinError as e:
+            print(e)
+        except SaveError as e:
+            print(e)
+        except NotAvailable:
+            print(date_text, None, None, file=log_file)
+            print('na')
+        except Skip:
+            print('--')
+
+
+def main():
+    log = replay()
+    today = datetime.date.today()
+    last_entry = max(log[1].keys()) if log[1] else today
+    download(last_entry, today, log)
 
 
 if __name__ == '__main__':
-    start, end = input_interval()
-    for date in date_range(start, end):
-        got_date(date)
-        if date in LOG_STATE and LOG_STATE[date] and os.path.exists(LOG_STATE[date]):
-            got_already()
-            continue
-        page = read_page(date)
-        url = image_url(page)
-        if url is None or comic_date(page) != date:
-            got_no_image(date)
-            continue
-        got_url()
-        ext = save_image(url, date)
-        got_image(date, url, ext)
-
+    main()
 
 # vim: et sw=4 sts=4