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+# (c) 2005 Ian Bicking and contributors; written for Paste (http://pythonpaste.org)
+# Licensed under the MIT license: http://www.opensource.org/licenses/mit-license.php
+"""
+An application that proxies WSGI requests to a remote server.
+
+TODO:
+
+* Send ``Via`` header?  It's not clear to me this is a Via in the
+  style of a typical proxy.
+
+* Other headers or metadata?  I put in X-Forwarded-For, but that's it.
+
+* Signed data of non-HTTP keys?  This would be for things like
+  REMOTE_USER.
+
+* Something to indicate what the original URL was?  The original host,
+  scheme, and base path.
+
+* Rewriting ``Location`` headers?  mod_proxy does this.
+
+* Rewriting body?  (Probably not on this one -- that can be done with
+  a different middleware that wraps this middleware)
+
+* Example::  
+    
+    use = egg:Paste#proxy
+    address = http://server3:8680/exist/rest/db/orgs/sch/config/
+    allowed_request_methods = GET
+  
+"""
+
+import httplib
+import urlparse
+import urllib
+
+from paste import httpexceptions
+from paste.util.converters import aslist
+
+# Remove these headers from response (specify lower case header
+# names):
+filtered_headers = (     
+    'transfer-encoding',
+    'connection',
+    'keep-alive',
+    'proxy-authenticate',
+    'proxy-authorization',
+    'te',
+    'trailers',
+    'upgrade',
+)
+
+class Proxy(object):
+
+    def __init__(self, address, allowed_request_methods=(),
+                 suppress_http_headers=()):
+        self.address = address
+        self.parsed = urlparse.urlsplit(address)
+        self.scheme = self.parsed[0].lower()
+        self.host = self.parsed[1]
+        self.path = self.parsed[2]
+        self.allowed_request_methods = [
+            x.lower() for x in allowed_request_methods if x]
+        
+        self.suppress_http_headers = [
+            x.lower() for x in suppress_http_headers if x]
+
+    def __call__(self, environ, start_response):
+        if (self.allowed_request_methods and 
+            environ['REQUEST_METHOD'].lower() not in self.allowed_request_methods):
+            return httpexceptions.HTTPBadRequest("Disallowed")(environ, start_response)
+
+        if self.scheme == 'http':
+            ConnClass = httplib.HTTPConnection
+        elif self.scheme == 'https':
+            ConnClass = httplib.HTTPSConnection
+        else:
+            raise ValueError(
+                "Unknown scheme for %r: %r" % (self.address, self.scheme))
+        conn = ConnClass(self.host)
+        headers = {}
+        for key, value in environ.items():
+            if key.startswith('HTTP_'):
+                key = key[5:].lower().replace('_', '-')
+                if key == 'host' or key in self.suppress_http_headers:
+                    continue
+                headers[key] = value
+        headers['host'] = self.host
+        if 'REMOTE_ADDR' in environ:
+            headers['x-forwarded-for'] = environ['REMOTE_ADDR']
+        if environ.get('CONTENT_TYPE'):
+            headers['content-type'] = environ['CONTENT_TYPE']
+        if environ.get('CONTENT_LENGTH'):
+            if environ['CONTENT_LENGTH'] == '-1':
+                # This is a special case, where the content length is basically undetermined
+                body = environ['wsgi.input'].read(-1)
+                headers['content-length'] = str(len(body))
+            else:
+                headers['content-length'] = environ['CONTENT_LENGTH'] 
+                length = int(environ['CONTENT_LENGTH'])
+                body = environ['wsgi.input'].read(length)
+        else:
+            body = ''
+            
+        path_info = urllib.quote(environ['PATH_INFO'])
+        if self.path:            
+            request_path = path_info
+            if request_path and request_path[0] == '/':
+                request_path = request_path[1:]
+                
+            path = urlparse.urljoin(self.path, request_path)
+        else:
+            path = path_info
+        if environ.get('QUERY_STRING'):
+            path += '?' + environ['QUERY_STRING']
+            
+        conn.request(environ['REQUEST_METHOD'],
+                     path,
+                     body, headers)
+        res = conn.getresponse()
+        headers_out = parse_headers(res.msg)
+        
+        status = '%s %s' % (res.status, res.reason)
+        start_response(status, headers_out)
+        # @@: Default?
+        length = res.getheader('content-length')
+        if length is not None:
+            body = res.read(int(length))
+        else:
+            body = res.read()
+        conn.close()
+        return [body]
+
+def make_proxy(global_conf, address, allowed_request_methods="",
+               suppress_http_headers=""):
+    """
+    Make a WSGI application that proxies to another address:
+    
+    ``address``
+        the full URL ending with a trailing ``/``
+        
+    ``allowed_request_methods``:
+        a space seperated list of request methods (e.g., ``GET POST``)
+        
+    ``suppress_http_headers``
+        a space seperated list of http headers (lower case, without
+        the leading ``http_``) that should not be passed on to target
+        host
+    """
+    allowed_request_methods = aslist(allowed_request_methods)
+    suppress_http_headers = aslist(suppress_http_headers)
+    return Proxy(
+        address,
+        allowed_request_methods=allowed_request_methods,
+        suppress_http_headers=suppress_http_headers)
+
+
+class TransparentProxy(object):
+
+    """
+    A proxy that sends the request just as it was given, including
+    respecting HTTP_HOST, wsgi.url_scheme, etc.
+
+    This is a way of translating WSGI requests directly to real HTTP
+    requests.  All information goes in the environment; modify it to
+    modify the way the request is made.
+
+    If you specify ``force_host`` (and optionally ``force_scheme``)
+    then HTTP_HOST won't be used to determine where to connect to;
+    instead a specific host will be connected to, but the ``Host``
+    header in the request will remain intact.
+    """
+
+    def __init__(self, force_host=None,
+                 force_scheme='http'):
+        self.force_host = force_host
+        self.force_scheme = force_scheme
+
+    def __repr__(self):
+        return '<%s %s force_host=%r force_scheme=%r>' % (
+            self.__class__.__name__,
+            hex(id(self)),
+            self.force_host, self.force_scheme)
+
+    def __call__(self, environ, start_response):
+        scheme = environ['wsgi.url_scheme']
+        if self.force_host is None:
+            conn_scheme = scheme
+        else:
+            conn_scheme = self.force_scheme
+        if conn_scheme == 'http':
+            ConnClass = httplib.HTTPConnection
+        elif conn_scheme == 'https':
+            ConnClass = httplib.HTTPSConnection
+        else:
+            raise ValueError(
+                "Unknown scheme %r" % scheme)
+        if 'HTTP_HOST' not in environ:
+            raise ValueError(
+                "WSGI environ must contain an HTTP_HOST key")
+        host = environ['HTTP_HOST']
+        if self.force_host is None:
+            conn_host = host
+        else:
+            conn_host = self.force_host
+        conn = ConnClass(conn_host)
+        headers = {}
+        for key, value in environ.items():
+            if key.startswith('HTTP_'):
+                key = key[5:].lower().replace('_', '-')
+                headers[key] = value
+        headers['host'] = host
+        if 'REMOTE_ADDR' in environ and 'HTTP_X_FORWARDED_FOR' not in environ:
+            headers['x-forwarded-for'] = environ['REMOTE_ADDR']
+        if environ.get('CONTENT_TYPE'):
+            headers['content-type'] = environ['CONTENT_TYPE']
+        if environ.get('CONTENT_LENGTH'):
+            length = int(environ['CONTENT_LENGTH'])
+            body = environ['wsgi.input'].read(length)
+            if length == -1:
+                environ['CONTENT_LENGTH'] = str(len(body))
+        elif 'CONTENT_LENGTH' not in environ:
+            body = ''
+            length = 0
+        else:
+            body = ''
+            length = 0
+        
+        path = (environ.get('SCRIPT_NAME', '')
+                + environ.get('PATH_INFO', ''))
+        path = urllib.quote(path)
+        if 'QUERY_STRING' in environ:
+            path += '?' + environ['QUERY_STRING']
+        conn.request(environ['REQUEST_METHOD'],
+                     path, body, headers)
+        res = conn.getresponse()
+        headers_out = parse_headers(res.msg)
+                
+        status = '%s %s' % (res.status, res.reason)
+        start_response(status, headers_out)
+        # @@: Default?
+        length = res.getheader('content-length')
+        if length is not None:
+            body = res.read(int(length))
+        else:
+            body = res.read()
+        conn.close()
+        return [body]
+
+def parse_headers(message):
+    """
+    Turn a Message object into a list of WSGI-style headers.
+    """
+    headers_out = []        
+    for full_header in message.headers:
+        if not full_header:            
+            # Shouldn't happen, but we'll just ignore
+            continue                     
+        if full_header[0].isspace():
+            # Continuation line, add to the last header
+            if not headers_out:                        
+                raise ValueError(
+                    "First header starts with a space (%r)" % full_header)
+            last_header, last_value = headers_out.pop()                   
+            value = last_value + ' ' + full_header.strip()
+            headers_out.append((last_header, value))      
+            continue                                
+        try:        
+            header, value = full_header.split(':', 1)
+        except:                                      
+            raise ValueError("Invalid header: %r" % full_header)
+        value = value.strip()                                   
+        if header.lower() not in filtered_headers:
+            headers_out.append((header, value))   
+    return headers_out
+
+def make_transparent_proxy(
+    global_conf, force_host=None, force_scheme='http'):
+    """
+    Create a proxy that connects to a specific host, but does
+    absolutely no other filtering, including the Host header.
+    """
+    return TransparentProxy(force_host=force_host,
+                            force_scheme=force_scheme)