handoff fixes

backend/tests/test_handoff_threading.py

@@ -0,0 +1,82 @@
+"""Integration-style tests for Human Handoff → Customer RFC threading."""
+
+from bson import ObjectId
+
+from app.services.external_reply_service import (
+    build_external_reply_plan,
+    internet_message_id_of,
+)
+from app.services.mail_sender import build_message, sign_message
+from types import SimpleNamespace
+
+
+def test_handoff_bridge_first_reply_threads_against_customer_a():
+    customer_a_id = "<CAHabc123@mail.gmail.com>"
+    customer_a = {
+        "_id": ObjectId(),
+        "internet_message_id": customer_a_id,
+        "message_id": customer_a_id,
+        "message_scope": "EXTERNAL",
+        "direction": "inbound",
+        "references": [],
+        "subject": "fresh test",
+    }
+    plan = build_external_reply_plan(
+        parent_external_message=customer_a,
+        body_text="human said B",
+        recipients=["091rabbytes@gmail.com"],
+    )
+    assert plan.threading.in_reply_to == customer_a_id
+    assert plan.threading.references == [customer_a_id]
+    assert plan.threading.in_reply_to != "<H2@gmail.com>"
+    assert "<H1@gentic.email>" not in plan.threading.references
+
+
+def test_lowercased_stored_id_recovered_via_raw_headers():
+    customer_a_id = "<CAHabc123@mail.gmail.com>"
+    parent = {
+        "_id": ObjectId(),
+        "internet_message_id": "<cahabc123@mail.gmail.com>",
+        "message_id": "<cahabc123@mail.gmail.com>",
+        "raw_headers": {"message_id": customer_a_id},
+        "references": [],
+        "subject": "fresh test",
+    }
+    plan = build_external_reply_plan(
+        parent_external_message=parent,
+        body_text="human said B",
+        recipients=["customer@gmail.com"],
+        parent_internet_id_override=internet_message_id_of(parent),
+    )
+    assert plan.threading.in_reply_to == customer_a_id
+    assert plan.threading.references == [customer_a_id]
+
+
+def test_signed_mime_preserves_threading_headers():
+    customer_a_id = "<CAHabc123@mail.gmail.com>"
+    message = build_message(
+        sender="suyash@gentic.email",
+        recipients=["091rabbytes@gmail.com"],
+        cc=[],
+        subject="Re: fresh test",
+        body_text="human said B",
+        body_html=None,
+        in_reply_to=customer_a_id,
+        references=[customer_a_id],
+        message_id="<B@gentic.email>",
+    )
+    domain = SimpleNamespace(
+        domain_name="gentic.email",
+        dkim_selector="agmail",
+        dkim_private_key="private-key",
+    )
+    from unittest.mock import patch
+
+    with patch(
+        "app.services.mail_sender.dkim.sign",
+        return_value=b"DKIM-Signature: test\r\n",
+    ):
+        signed = sign_message(message, domain)
+
+    assert f"In-Reply-To: {customer_a_id}".encode() in signed
+    assert f"References: {customer_a_id}".encode() in signed