"""Regression tests for the truncated-response repetition guard (#86581).

A truncated response (``finish_reason=length``) dominated by verbatim
repeated text must NOT be continued: the continuation nudge would stitch the
pathological fragment into the final response (the #86581 incident delivered
60,698 chars as 31 Discord messages).  The turn aborts with a clear
user-facing error instead, mirroring the existing thinking-budget guard.
"""

from __future__ import annotations

from types import SimpleNamespace
from unittest.mock import MagicMock, patch

import pytest

from hermes_constants import FINISH_REASON_LENGTH, PARTIAL_STREAM_STUB_ID

# The exact sentence from the #86581 incident.
_INCIDENT_ECHO = "好，你幫我更改成 Google Gemini 4 31B。"


@pytest.fixture()
def loop_agent():
    from run_agent import AIAgent

    with (
        patch("run_agent.get_tool_definitions", return_value=[]),
        patch("run_agent.check_toolset_requirements", return_value={}),
        patch("run_agent.OpenAI"),
    ):
        a = AIAgent(
            api_key="test-key-1234567890",
            base_url="https://openrouter.ai/api/v1",
            quiet_mode=True,
            skip_context_files=True,
            skip_memory=True,
        )
        a.client = MagicMock()
        a._cached_system_prompt = "You are helpful."
        a._use_prompt_caching = False
        a.compression_enabled = False
        a.save_trajectories = False
        return a


def _stub(content):
    from tests.run_agent.test_run_agent import _mock_assistant_msg

    return SimpleNamespace(
        id=PARTIAL_STREAM_STUB_ID,
        model="test/model",
        choices=[SimpleNamespace(
            index=0,
            message=_mock_assistant_msg(content=content),
            finish_reason=FINISH_REASON_LENGTH,
        )],
        usage=None,
    )


def _run(agent, message):
    with (
        patch.object(agent, "_persist_session"),
        patch.object(agent, "_save_trajectory"),
        patch.object(agent, "_cleanup_task_resources"),
    ):
        return agent.run_conversation(message)


class TestContinuationRepetitionGuard:
    def test_repetition_dominated_truncation_aborts(self, loop_agent):
        echo = _INCIDENT_ECHO * 2000
        loop_agent.client.chat.completions.create.side_effect = [_stub(echo)]

        result = _run(loop_agent, "write me a long report")

        assert result["completed"] is False
        assert result["partial"] is True
        assert "Repetition" in (result["final_response"] or "")
        # The pathological fragment must NOT be appended to the history.
        assert not any(
            isinstance(m, dict) and m.get("_length_continuation_fragment")
            for m in result["messages"]
        )
        # Exactly one API call — no continuation was attempted.
        assert loop_agent.client.chat.completions.create.call_count == 1

    def test_legit_truncation_still_continues(self, loop_agent):
        # Ordinary short truncated fragments still get continuation retries.
        loop_agent.client.chat.completions.create.side_effect = [
            _stub("part one "), _stub("part two "),
            _stub("part three "), _stub("part four."),
        ]

        result = _run(loop_agent, "write me a long report")

        assert result["partial"] is True
        assert loop_agent.client.chat.completions.create.call_count == 4