From 29892da19ae7c1b2777f48bce4674262d2a19cef Mon Sep 17 00:00:00 2001
From: Timotej Lazar <timotej.lazar@araneo.org>
Date: Fri, 28 Aug 2015 17:44:51 +0200
Subject: Add a hint service for Prolog

---
 server/problems.py       |  3 +++
 server/prolog_session.py | 21 +++++++++++++++++++++
 server/user_session.py   |  8 +++++++-
 3 files changed, 31 insertions(+), 1 deletion(-)

(limited to 'server')

diff --git a/server/problems.py b/server/problems.py
index f54237d..fed9e77 100644
--- a/server/problems.py
+++ b/server/problems.py
@@ -36,6 +36,9 @@ def load_module(fullname):
                 raise
         return mod
 
+def load_language(language, tail_module):
+    return load_module('{0}.{1}'.format(language, tail_module))
+
 def load_problem(language, problem_group, problem, tail_module):
     return load_module('{0}.problems.{1}.{2}.{3}'.format(language, problem_group, problem, tail_module))
 
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')
diff --git a/server/user_session.py b/server/user_session.py
index a463903..8b76e0a 100644
--- a/server/user_session.py
+++ b/server/user_session.py
@@ -66,6 +66,12 @@ class UserSession(object):
 
     def get_problem_data(self, language, problem_group, problem):
         mod = problems.load_problem(language, problem_group, problem, 'en')
+        mod_language = problems.load_language(language, 'en')
+
+        # Get generic and problem-specific hints.
+        hint = dict(mod_language.hint)
+        hint.update(mod.hint)
+
         conn = db.get_connection()
         try:
             cur = conn.cursor()
@@ -76,7 +82,7 @@ class UserSession(object):
                 result = {
                     'language': {'id': row[0], 'identifier': language, 'name': row[1]},
                     'problem_group': {'id': row[2], 'identifier': problem_group, 'name': row[3]},
-                    'problem': {'id': problem_id, 'identifier': problem, 'name': row[5], 'slug': mod.slug, 'description': mod.description, 'hint': mod.hint}
+                    'problem': {'id': problem_id, 'identifier': problem, 'name': row[5], 'slug': mod.slug, 'description': mod.description, 'hint': hint}
                 }
                 cur.execute("select content from solution where problem_id = %s and codeq_user_id = %s", (problem_id, self.uid))
                 row = cur.fetchone()
-- 
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