From 820e9555153193700a8d536f2f1fe0cef56f452a Mon Sep 17 00:00:00 2001
From: Andrew Godwin <andrew@aeracode.org>
Date: Fri, 11 Mar 2016 10:20:17 -0800
Subject: [PATCH] Change ASGI spec regarding headers.

---
 channels/handler.py | 22 ++++++++++++++++------
 channels/message.py |  6 ++++++
 docs/asgi.rst       | 15 ++++++++-------
 3 files changed, 30 insertions(+), 13 deletions(-)

diff --git a/channels/handler.py b/channels/handler.py
index a32d1af..42fe00e 100644
--- a/channels/handler.py
+++ b/channels/handler.py
@@ -58,16 +58,26 @@ class AsgiRequest(http.HttpRequest):
         if self.message.get('server', None):
             self.META['SERVER_NAME'] = self.message['server'][0]
             self.META['SERVER_PORT'] = self.message['server'][1]
+        # Handle old style-headers for a transition period
+        if "headers" in self.message and isinstance(self.message['headers'], dict):
+            self.message['headers'] = [
+                (x.encode("latin1"), y) for x, y in
+                self.message['headers'].items()
+            ]
         # Headers go into META
-        for name, value in self.message.get('headers', {}).items():
+        for name, value in self.message.get('headers', []):
+            name = name.decode("latin1")
             if name == "content-length":
                 corrected_name = "CONTENT_LENGTH"
             elif name == "content-type":
                 corrected_name = "CONTENT_TYPE"
             else:
                 corrected_name = 'HTTP_%s' % name.upper().replace("-", "_")
-            # HTTPbis say only ASCII chars are allowed in headers
-            self.META[corrected_name] = value.decode("ascii")
+            # HTTPbis say only ASCII chars are allowed in headers, but we latin1 just in case
+            value = value.decode("latin1")
+            if corrected_name in self.META:
+                value = self.META[corrected_name] + "," + value.decode("latin1")
+            self.META[corrected_name] = value
         # Pull out request encoding if we find it
         if "CONTENT_TYPE" in self.META:
             _, content_params = cgi.parse_header(self.META["CONTENT_TYPE"])
@@ -212,13 +222,13 @@ class AsgiHandler(base.BaseHandler):
         # compliant clients that want things like Content-Type correct. Ugh.
         response_headers = []
         for header, value in response.items():
-            if isinstance(header, six.binary_type):
-                header = header.decode("latin1")
+            if isinstance(header, six.text_type):
+                header = header.encode("ascii")
             if isinstance(value, six.text_type):
                 value = value.encode("latin1")
             response_headers.append(
                 (
-                    six.text_type(header),
+                    six.binary_type(header),
                     six.binary_type(value),
                 )
             )
diff --git a/channels/message.py b/channels/message.py
index 5830fdd..15e3891 100644
--- a/channels/message.py
+++ b/channels/message.py
@@ -30,5 +30,11 @@ class Message(object):
     def __getitem__(self, key):
         return self.content[key]
 
+    def __setitem__(self, key, value):
+        self.content[key] = value
+
+    def __contains__(self, key):
+        return key in self.content
+
     def get(self, key, default=None):
         return self.content.get(key, default)
diff --git a/docs/asgi.rst b/docs/asgi.rst
index 085f6fd..2a5f9a7 100644
--- a/docs/asgi.rst
+++ b/docs/asgi.rst
@@ -454,11 +454,11 @@ Keys:
   is mounted at; same as ``SCRIPT_NAME`` in WSGI. Optional, defaults
   to ``""``.
 
-* ``headers``: Dict of ``{name: value}``, where ``name`` is the lowercased
-  HTTP header name as unicode string and ``value`` is the header value as a byte
-  string. If multiple headers with the same name are received, they should
-  be concatenated into a single header as per RFC 7230. Header names containing
-  underscores should be discarded by the server. Optional, defaults to ``{}``.
+* ``headers``: A list of ``[name, value]`` pairs, where ``name`` is the
+  byte string header name, and ``value`` is the byte string
+  header value. Order should be preserved from the original HTTP request;
+  duplicates are possible and must be preserved in the message as received.
+  Header names must be lowercased.
 
 * ``body``: Body of the request, as a byte string. Optional, defaults to ``""``.
   If ``body_channel`` is set, treat as start of body and concatenate
@@ -514,8 +514,9 @@ Keys:
   or left as empty string if no default found.
 
 * ``headers``: A list of ``[name, value]`` pairs, where ``name`` is the
-  unicode string header name, and ``value`` is the byte string
-  header value. Order should be preserved in the HTTP response.
+  byte string header name, and ``value`` is the byte string
+  header value. Order should be preserved in the HTTP response. Header names
+  must be lowercased.
 
 * ``content``: Byte string of HTTP body content.
   Optional, defaults to empty string.