feat: Add function to make api calls

Author: Mukundan314

codeforces/__init__.py

@@ -1 +1,2 @@
 from . import error
+from . import api

codeforces/api.py

@@ -0,0 +1,55 @@
+import time
+import os
+import json
+import random
+import hashlib
+import urllib.request
+import urllib.error
+import urllib.parse
+from . import error
+
+
+__all__ = ['call']
+
+
+CODEFORCES_API_URL = "https://codeforces.com/api/"
+
+
+def __generate_api_sig(method, args, secret):
+    rand = "%06d" % random.randint(0, 999999)
+    url_args = urllib.parse.urlencode(sorted(args.items()))
+    return rand + hashlib.sha512(
+        ("%s/%s?%s#%s" % (rand, method, url_args, secret)).encode('utf-8')
+    ).hexdigest()
+
+
+def call(method, key=None, secret=None, **kargs):
+    """call a Codeforces API method"""
+    args = kargs.copy()
+
+    if (key is not None) and (secret is not None):
+        args['time'] = int(time.time())
+        args['apiKey'] = key
+        args['apiSig'] = __generate_api_sig(method, args, secret)
+
+    url_args = urllib.parse.urlencode(args)
+    url = os.path.join(CODEFORCES_API_URL, "%s?%s" % (method, url_args))
+
+    try:
+        with urllib.request.urlopen(url) as res:
+            data = json.loads(res.read().decode('utf-8'))
+    except urllib.error.HTTPError as err:
+        if err.code == 400:
+            data = json.loads(err.read())
+        elif err.code == 404:
+            data = {'status': 'FAILED', 'comment': "%s: No such method" % method}
+        elif (err.code in (429, 503)):
+            time.sleep(1)
+            return call(method, key, secret, **kargs)
+        else:
+            raise
+
+    if data['status'] == 'FAILED':
+        raise error.CodeforcesAPIError(data['comment'], method, kargs)
+
+    return data['result']