[Chat window] Expose chat window and add enable_internal_features que…

…ry in chat url (#2941)

# Description

Please add an informative description that covers that changes made by
the pull request and link all relevant issues.

# All Promptflow Contribution checklist:
- [ ] **The pull request does not introduce [breaking changes].**
- [ ] **CHANGELOG is updated for new features, bug fixes or other
significant changes.**
- [ ] **I have read the [contribution guidelines](../CONTRIBUTING.md).**
- [ ] **Create an issue and link to the pull request to get dedicated
review from promptflow team. Learn more: [suggested
workflow](../CONTRIBUTING.md#suggested-workflow).**

## General Guidelines and Best Practices
- [ ] Title of the pull request is clear and informative.
- [ ] There are a small number of commits, each of which have an
informative message. This means that previously merged commits do not
appear in the history of the PR. For more information on cleaning up the
commits in your PR, [see this
page](https://github.com/Azure/azure-powershell/blob/master/documentation/development-docs/cleaning-up-commits.md).

### Testing Guidelines
- [ ] Pull request includes test coverage for the included changes.

src/promptflow-devkit/promptflow/_cli/_pf/_flow.py

@@ -51,6 +51,7 @@
 
 DEFAULT_CONNECTION = "open_ai_connection"
 DEFAULT_DEPLOYMENT = "gpt-35-turbo"
+PF_CHAT_UI_ENABLE_STREAMLIT = "pf_chat_ui_enable_streamlit"
 logger = get_cli_sdk_logger()
 
 
@@ -479,25 +480,9 @@ def _build_inputs_for_flow_test(args):
 
 def _test_flow_multi_modal(args, pf_client):
     """Test flow with multi modality mode."""
-    from promptflow._sdk._load_functions import load_flow
-
-    if Configuration.get_instance().is_internal_features_enabled():
-        from promptflow._sdk._tracing import _invoke_pf_svc
-
-        # Todo: use base64 encode for now, will consider whether need use encryption or use db to store flow path info
-        def generate_url(flow_path, port):
-            encrypted_flow_path = encrypt_flow_path(flow_path)
-            query_params = urlencode({"flow": encrypted_flow_path})
-            return urlunparse(("http", f"127.0.0.1:{port}", "/v1.0/ui/chat", "", query_params, ""))
+    if str(os.getenv(PF_CHAT_UI_ENABLE_STREAMLIT, "false")).lower() == "true":
+        from promptflow._sdk._load_functions import load_flow
 
-        pfs_port = _invoke_pf_svc()
-        flow_path_dir, flow_path_file = resolve_flow_path(args.flow)
-        flow_path = str(flow_path_dir / flow_path_file)
-        chat_page_url = generate_url(flow_path, pfs_port)
-        print(f"You can begin chat flow on {chat_page_url}")
-        if not args.skip_open_browser:
-            webbrowser.open(chat_page_url)
-    else:
         if is_flex_flow(flow_path=args.flow):
             error = ValueError("Only support dag yaml in streamlit ui.")
             raise UserErrorException(
@@ -521,6 +506,25 @@ def generate_url(flow_path, port):
             main_script_path = os.path.join(temp_dir, "main.py")
             logger.info("Start streamlit with main script generated at: %s", main_script_path)
             pf_client.flows._chat_with_ui(script=main_script_path, skip_open_browser=args.skip_open_browser)
+    else:
+        from promptflow._sdk._tracing import _invoke_pf_svc
+
+        # Todo: use base64 encode for now, will consider whether need use encryption or use db to store flow path info
+        def generate_url(flow_path, port):
+            encrypted_flow_path = encrypt_flow_path(flow_path)
+            query_dict = {"flow": encrypted_flow_path}
+            if Configuration.get_instance().is_internal_features_enabled():
+                query_dict.update({"enable_internal_features": "true"})
+            query_params = urlencode(query_dict)
+            return urlunparse(("http", f"127.0.0.1:{port}", "/v1.0/ui/chat", "", query_params, ""))
+
+        pfs_port = _invoke_pf_svc()
+        flow_path_dir, flow_path_file = resolve_flow_path(args.flow)
+        flow_path = str(flow_path_dir / flow_path_file)
+        chat_page_url = generate_url(flow_path, pfs_port)
+        print(f"You can begin chat flow on {chat_page_url}")
+        if not args.skip_open_browser:
+            webbrowser.open(chat_page_url)
 
 
 def _test_flow_interactive(args, pf_client, inputs, environment_variables):