Support reverse proxy subdirectory

Closes #19

cps/web.py

@@ -32,7 +32,44 @@ except ImportError, e:
     use_generic_pdf_cover = True
 from shutil import copyfile
 
+class ReverseProxied(object):
+    '''Wrap the application in this middleware and configure the 
+    front-end server to add these headers, to let you quietly bind 
+    this to a URL other than / and to an HTTP scheme that is 
+    different than what is used locally.
+
+    Code courtesy of: http://flask.pocoo.org/snippets/35/
+
+    In nginx:
+    location /myprefix {
+        proxy_pass http://127.0.0.1:8083;
+        proxy_set_header Host $host;
+        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+        proxy_set_header X-Scheme $scheme;
+        proxy_set_header X-Script-Name /myprefix;
+        }
+    '''
+    def __init__(self, app):
+        self.app = app
+
+    def __call__(self, environ, start_response):
+        script_name = environ.get('HTTP_X_SCRIPT_NAME', '')
+        if script_name:
+            environ['SCRIPT_NAME'] = script_name
+            path_info = environ['PATH_INFO']
+            if path_info.startswith(script_name):
+                environ['PATH_INFO'] = path_info[len(script_name):]
+
+        scheme = environ.get('HTTP_X_SCHEME', '')
+        if scheme:
+            environ['wsgi.url_scheme'] = scheme
+        server = environ.get('HTTP_X_FORWARDED_SERVER', '')
+        if server:
+            environ['HTTP_HOST'] = server
+        return self.app(environ, start_response)
+
 app = (Flask(__name__))
+app.wsgi_app = ReverseProxied(app.wsgi_app)
 
 formatter = logging.Formatter(
     "[%(asctime)s] {%(pathname)s:%(lineno)d} %(levelname)s - %(message)s")