From 0306dd29e220a34980aa332da61de34cd3dbbece Mon Sep 17 00:00:00 2001
From: Andreas Kloeckner <inform@tiker.net>
Date: Mon, 11 Sep 2017 17:29:15 -0500
Subject: [PATCH] Towards HTTP API call rules

---
 course/utils.py      | 58 ++++++++++++++++++++++++++++++++++++++++++++
 course/validation.py | 16 ++++++++++++
 requirements.txt     |  5 ++--
 3 files changed, 77 insertions(+), 2 deletions(-)

diff --git a/course/utils.py b/course/utils.py
index 8133a79f..af903128 100644
--- a/course/utils.py
+++ b/course/utils.py
@@ -147,6 +147,59 @@ class FlowSessionGradingRule(FlowSessionRuleBase):
         self.bonus_points = bonus_points
 
 
+def _eval_http_rule(rule, participation, flow_id):
+    get_parameters = {}
+
+    from relate.utils import struct_to_dict
+    for key, value in six.iteritems(struct_to_dict(rule.get_parameters)):
+        if value[0] == "literal":
+            _, get_value = value
+        elif value[0] == "field":
+            _, field_name = value
+            if field_name == "email":
+                get_value = participation.user.email
+            elif field_name == "institutional_id":
+                get_value = participation.user.institutional_id
+            else:
+                raise ValueError("invalid field name '%s'" % field_name)
+        else:
+            raise ValueError("invalid GET parameter type '%s'" % value[0])
+
+        get_parameters[key] = str(get_value)
+
+    # TODO: caching
+    # TODO: documentation
+
+    import requests
+    try:
+        r = requests.get(rule.url, params=get_parameters)
+        r.raise_for_status()
+    except requests.exceptions.RequestException as e:
+        return False
+
+    try:
+        response_json = r.json()
+    except ValueError:
+        return False
+
+    for key, value in six.iteritems(struct_to_dict(rule.response)):
+        json_value = response_json.get(key)
+        if value[0] == "required_value":
+            _, req_value = value
+
+            if json_value != req_value:
+                return False
+
+        elif value[0] == "cache_until":
+            pass
+            # TODO
+
+        else:
+            raise ValueError("invalid response processing directive '%s'" % value[0])
+
+    return True
+
+
 def _eval_generic_conditions(
         rule,  # type: Any
         course,  # type: Course
@@ -182,6 +235,11 @@ def _eval_generic_conditions(
         if login_exam_ticket.exam.flow_id != flow_id:
             return False
 
+    if hasattr(rule, "if_http_api_call"):
+        if not _eval_http_rule(
+                rule.if_external_http, participation, flow_id):
+            return False
+
     return True
 
 
diff --git a/course/validation.py b/course/validation.py
index 76c1739a..5496d2c6 100644
--- a/course/validation.py
+++ b/course/validation.py
@@ -554,6 +554,17 @@ def validate_flow_group(vctx, location, grp):
 
 # {{{ flow rules
 
+def validate_http_api_call_rule(vctx, location, http_rule):
+    validate_struct(
+            vctx, location, http_rule,
+            required_attrs=[
+                ("url", str),
+                ("get_parameters", Struct),
+                ("cache_for_max_seconds", int),
+                ("response", Struct),
+                ])
+
+
 def validate_session_start_rule(vctx, location, nrule, tags):
     validate_struct(
             vctx, location, nrule,
@@ -569,6 +580,8 @@ def validate_session_start_rule(vctx, location, nrule, tags):
                 ("if_has_session_tagged", (six.string_types, type(None))),
                 ("if_has_fewer_sessions_than", int),
                 ("if_has_fewer_tagged_sessions_than", int),
+                ("if_external_http", Struct),
+
                 ("if_signed_in_with_matching_exam_ticket", bool),
                 ("tag_session", (six.string_types, type(None))),
                 ("may_start_new_session", bool),
@@ -605,6 +618,9 @@ def validate_session_start_rule(vctx, location, nrule, tags):
             validate_identifier(vctx, "%s: if_has_session_tagged" % location,
                     nrule.if_has_session_tagged)
 
+    if hasattr(nrule, "if_http_api_call"):
+        validate_http_api_call_rule(vctx, location, nrule.if_external_http)
+
     if not hasattr(nrule, "may_start_new_session"):
         vctx.add_warning(
                 location+", rules",
diff --git a/requirements.txt b/requirements.txt
index 3a5dbd32..7a598fc4 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -40,8 +40,7 @@ paramiko
 git+https://github.com/inducer/django-bootstrap3-datetimepicker.git
 
 # For in-class instant messaging
-# dnspython  # Py2
-dnspython3  # Py3
+dnspython
 # Py2 broken was broken in 1.3.1
 git+https://github.com/fritzy/SleekXMPP.git@6e27f28c854ce4ae1d9f0cc8ee407bda8de97d3b
 
@@ -112,4 +111,6 @@ typing
 # For unittest by mock (only required for Py2)
 # mock
 
+requests
+
 # vim: foldmethod=marker
-- 
GitLab