1 files changed, 134 insertions, 0 deletions
diff --git a/prolog/engine.py b/prolog/engine.py
new file mode 100644
index 0000000..af79535
--- /dev/null
+++ b/prolog/engine.py
@@ -0,0 +1,134 @@
+#!/usr/bin/python3
+
+import collections
+import http.client
+import json
+import re
+import urllib
+
+# Create a new pengine. If query is given: run it, destroy the engine and
+# return the reply. Otherwise, return the ID of the new pengine.
+def create(code=''):
+    opts = {'format': 'json-s', 'destroy': True, 'src_text': code}
+    reply, messages = request('POST', '/pengine/create', body=json.dumps(opts))
+
+    if reply['event'] != 'create' or 'error' in messages:
+        raise Exception('\n'.join(messages['error']))
+
+    return reply['id']
+
+def create_and_ask(code, query):
+    opts = {'format': 'json-s', 'destroy': True, 'src_text': code, 'ask': query}
+    reply, messages = request('POST', '/pengine/create', body=json.dumps(opts))
+
+    if reply['event'] != 'create' or 'error' in messages:
+        raise Exception('\n'.join(messages['error']))
+
+    return reply['answer']['data']
+
+def ask(engine, query):
+    return send(engine, 'ask(({}),[])'.format(query))
+
+def next(engine, n=1):
+    return send(engine, 'next({})'.format(n))
+
+def stop(engine):
+    return send(engine, 'stop')
+
+def destroy(engine):
+    return send(engine, 'destroy')
+
+def send(engine, event):
+    params = urllib.parse.urlencode({
+        'id': engine,
+        'event': event,
+        'format': 'json-s'})
+    reply, messages = request('GET', '/pengine/send?' + params)
+    return reply
+
+# Return the main reply and pull potential output replies.
+address, port = 'localhost', 3030  # TODO put this somewhere sane
+def request(method, path, body=None):
+    headers = {'Content-Type': 'application/json;charset=utf-8'}
+    messages = collections.defaultdict(list)
+    try:
+        conn = http.client.HTTPConnection(address, port, timeout=10)
+        conn.request(method, path, body, headers=headers)
+        while True:
+            response = conn.getresponse()
+            if response.status != http.client.OK:
+                raise Exception('server returned {}'.format(response.status))
+
+            reply = json.loads(response.read().decode('utf-8'))
+            if reply['event'] == 'output':
+                msg_type, msg_data = get_message(reply)
+                messages[msg_type].append(msg_data)
+
+                # Request next reply.
+                params = urllib.parse.urlencode({
+                    'id': reply['id'],
+                    'format': 'json-s'})
+                conn.request('GET', '/pengine/pull_response?' + params, headers=headers)
+            else:
+                return reply, messages
+    finally:
+        conn.close()
+
+# Strip boilerplate from Prolog messages … ugly.
+def get_message(reply):
+    match = re.match(r'.*<pre class="[^"]*">(.*)</pre>.*',
+                     reply['data'], flags=re.DOTALL)
+    data = match.group(1).strip()
+    message = ''
+    if reply['message'] == 'error':
+        if 'location' in reply:
+            loc = reply['location']
+            message += 'near line ' + str(loc['line'])
+            if 'ch' in loc:
+                message += ', character ' + str(loc['ch'])
+            message += ': '
+
+        if reply.get('code') == 'syntax_error':
+            match = re.match(r'^.*Syntax error: (.*)$', data, flags=re.DOTALL)
+            message += match.group(1)
+        elif reply.get('code') == 'permission_error':
+            match = re.match(r'^.*(No permission [^\n]*)', data, flags=re.DOTALL)
+            message += match.group(1)
+        elif reply.get('code') == 'type_error':
+            match = re.match(r'^.*(Type error: [^\n]*)', data, flags=re.DOTALL)
+            message += match.group(1)
+        else:
+            message += data
+
+    # Replace anonymous variable names with _.
+    message = re.sub(r'_G[0-9]*', '_', message)
+    return reply['message'], message
+
+# Test whether [code] is a correct solution for problem [name]. Runs all tests
+# and returns a list of results. Raises an exception on error.
+def test_all(name, code):
+    reply = create_and_ask(code=code, query="run_tests({}, Results)".format(name))
+
+    if reply['event'] != 'success':
+        raise Exception('testing procedure failed')
+
+    results = re.findall(r'(?:success|failure)\([^)]*\)', reply['data'][0]['Results'])
+    n_total = len(results)
+    n_passed = len([r for r in results if r.startswith('success')])
+    return n_passed, n_total
+
+# Test whether [code] is a correct solution for problem [name]. Returns a bool
+# and stops on first failure.
+def test(name, code):
+    try:
+        reply = create_and_ask(code=code, query='run_tests({})'.format(name))
+        return reply['event'] == 'success'
+    except Exception as ex:
+        return False
+
+# Basic sanity check.
+if __name__ == '__main__':
+    engine = PrologEngine(code='dup([],[]). dup([H|T],[H,H|TT]) :- dup(T,TT).')
+    print('engine id is ' + engine.id)
+    print(engine.ask("run_tests({}, Result)".format('dup/2')))
+    engine.destroy()