Use json-html format for Prolog replies

The only way to get residuals in CLP queries.

1 files changed, 27 insertions, 6 deletions

diff --git a/prolog/engine.py b/prolog/engine.py
index 50282d4..96191ae 100644
--- a/prolog/engine.py
+++ b/prolog/engine.py
@@ -5,12 +5,16 @@ import http.client
 import json
 import re
 import urllib
+import xml.etree.ElementTree
+
+def strip_html(html_str):
+    return ''.join(xml.etree.ElementTree.fromstring(html_str).itertext())
 
 # Create a new pengine, initialize it with [code] and return Prolog's reply.
 # The engine is destroyed after answering one query. If [query] is given, the
 # first answer is returned and the engine destroyed.
 def create(code='', query=''):
-    opts = {'format': 'json-s', 'destroy': True, 'src_text': code}
+    opts = {'format': 'json-html', 'destroy': True, 'src_text': code}
     if query:
         opts['ask'] = query
     reply, messages = request('POST', '/pengine/create', body=json.dumps(opts))
@@ -39,7 +43,7 @@ def send(engine, event):
     params = urllib.parse.urlencode({
         'id': engine,
         'event': event,
-        'format': 'json-s'})
+        'format': 'json-html'})
     reply, messages = request('GET', '/pengine/send?' + params)
     return reply
 
@@ -64,7 +68,7 @@ def request(method, path, body=None):
                 # Request next reply.
                 params = urllib.parse.urlencode({
                     'id': reply['id'],
-                    'format': 'json-s'})
+                    'format': 'json-html'})
                 conn.request('GET', '/pengine/pull_response?' + params, headers=headers)
             else:
                 return reply, messages
@@ -73,9 +77,7 @@ def request(method, path, body=None):
 
 # 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()
+    data = strip_html(reply['data']).strip()
     message = ''
     if reply['message'] == 'error':
         if 'location' in reply:
@@ -100,6 +102,25 @@ def get_message(reply):
     message = re.sub(r'_G[0-9]*', '_', message)
     return reply['message'], message
 
+# Return the value of variable [name] in the JSON object returned by Prolog.
+def get_var(data, name):
+    for binding in data['variables']:
+        if name in binding['variables']:
+            return strip_html(binding['value'])
+    return None
+
+# Return a string describing variable bindings and residuals in the JSON object
+# returned by Prolog.
+def pretty_vars(data):
+    result = []
+    for binding in data['variables']:
+        var_list = binding['variables']
+        value = binding['value']
+        result.append(' = '.join(var_list) + ' = ' + strip_html(value))
+    if 'residuals' in data:
+        result += [strip_html(b) for b in data['residuals']]
+    return ',\n'.join(result)
+
 # Basic sanity check.
 if __name__ == '__main__':
     engine = create(code='dup([],[]). dup([H|T],[H,H|TT]) :- dup(T,TT).')['id']