Generate valid chunked response when returning short circuit answer (#1001)

Prior to this change, this code would return a malformed HTTP response
with a chunk size, then HTTP header, then body, then the final chunk
size, final chunk then zero.

This changes the code to return the header before returning the code.
Furthermore, it does not count the size of the header in the first chunk
size.

Author: dmjb

src/codegate/providers/copilot/provider.py

@@ -111,19 +111,29 @@ class HttpResponse:
     headers: List[str]
     body: Optional[bytes] = None
 
-    def reconstruct(self) -> bytes:
-        """Reconstruct HTTP response from stored details"""
+    def reconstruct_headers(self) -> bytes:
+        """
+        Reconstruct the HTTP header of the response.
+        """
         headers = "\r\n".join(self.headers)
         status_line = f"{self.version} {self.status_code} {self.reason}\r\n"
         header_block = f"{status_line}{headers}\r\n\r\n"
+        return header_block.encode("utf-8")
 
-        # Convert header block to bytes and combine with body
-        result = header_block.encode("utf-8")
+    def reconstruct_body(self) -> bytes:
+        """
+        Reconstruct the body of the response.
+        """
+        result = b""
         if self.body:
             result += self.body
-
+            result += b"\n\n"
         return result
 
+    def reconstruct(self) -> bytes:
+        """Reconstruct HTTP response from stored details"""
+        return self.reconstruct_headers() + self.reconstruct_body()
+
 
 def extract_path(full_path: str) -> str:
     """Extract clean path from full URL or path string"""
@@ -387,8 +397,12 @@ async def _forward_data_to_target(self, data: bytes) -> None:
                 # request to the target
                 self.target_transport.close()
 
-                # Send the shortcut response data in a chunk
-                chunk = pipeline_output.reconstruct()
+                # Send the HTTP headers
+                # Note that this representation ends with \r\n\r\n
+                self.transport.write(pipeline_output.reconstruct_headers())
+
+                # Encode the body, send its length, then the data
+                chunk = pipeline_output.reconstruct_body()
                 chunk_size = hex(len(chunk))[2:] + "\r\n"
                 self.transport.write(chunk_size.encode())
                 self.transport.write(chunk)