Add a hint service for Prolog

1 files changed, 21 insertions, 0 deletions

diff --git a/server/prolog_session.py b/server/prolog_session.py
index ff44a56..d83d62d 100644
--- a/server/prolog_session.py
+++ b/server/prolog_session.py
@@ -88,6 +88,27 @@ class PrologSession(object):
             prolog.engine.destroy(self._engine_id)
             self._engine_id = None
 
+    def hint(self, user_id, problem_id, program):
+        language, problem_group, problem = Problem.identifier(problem_id)
+
+        # If compilation fails just return compiler messages.
+        engine_id, output = prolog.engine.create(code=program)
+        if engine_id is not None:
+            prolog.engine.destroy(engine_id)
+        if 'error' in map(operator.itemgetter(0), output):
+            errors_msg = '\n'.join(['{}: {}'.format(m_type, m_text) for m_type, m_text in output])
+            return [{'id': 'syntax_error', 'args': {'messages': errors_msg}}]
+
+        # Otherwise try problem-specific hints.
+        problem_module = problems.load_problem(language, problem_group, problem, 'common')
+        if hasattr(problem_module, 'hint'):
+            hints = problem_module.hint(program)
+            if hints:
+                return hints
+
+        # Finally return a generic "try thinking a bit" message.
+        return [{'id': 'no_hint'}]
+
     def test(self, user_id, problem_id, program):
         language, problem_group, problem = Problem.identifier(problem_id)
         problem_module = problems.load_problem(language, problem_group, problem, 'common')