"""Regression guard for issue #1428 — the "x" on a chat output did nothing when
no model/API was selected.

deleteMessage() bailed at `if (!sessionId) return;`. An output shown before a
model is picked has no session and no persisted rows, so the early-out meant the
"x" never even removed the bubble from the DOM. The delete now falls through to
DOM removal when there's no session / no DB ids.

chat.js pulls in browser globals so it can't run under node; guard at the source.
"""
import re
from pathlib import Path

SRC = Path(__file__).resolve().parent.parent / "static/js/chat.js"


def _delete_message_body() -> str:
    text = SRC.read_text(encoding="utf-8")
    start = text.index("export async function deleteMessage(")
    rest = text[start:]
    m = re.search(r"\n  export (async )?function ", rest[1:])
    return rest[: m.start() + 1] if m else rest


def test_delete_does_not_early_return_on_missing_session():
    body = _delete_message_body()
    # The bug was an unconditional early-out when no session existed.
    assert not re.search(r"if\s*\(\s*!sessionId\s*\)\s*return\s*;", body), (
        "deleteMessage must not early-return on a missing session (#1428)"
    )
    # The DOM-removal fallback must also fire when there's no session.
    assert re.search(r"!msgIds\.length\s*\|\|\s*!sessionId", body), (
        "DOM-removal fallback should cover the no-session case"
    )