"""Regression coverage for provider-safe transient context compression."""

from langchain_core.messages import AIMessage, HumanMessage, SystemMessage, ToolMessage

from deerflow.agents.middlewares.summarization_middleware import _ensure_latest_human_message


def test_compression_restores_latest_human_turn_when_only_tool_tail_remains():
    user = HumanMessage(content="请分析这份材料", id="user-1")
    source = [
        user,
        AIMessage(content="", id="ai-1"),
        ToolMessage(content="检索结果", tool_call_id="call-1", id="tool-1"),
    ]
    compressed = [SystemMessage(content="internal summary"), *source[1:]]

    result = _ensure_latest_human_message(source, compressed)

    assert result[0].type == "system"
    assert result[1] is user
    assert [message.type for message in result[2:]] == ["ai", "tool"]


def test_compression_does_not_duplicate_human_turn_already_in_tail():
    user = HumanMessage(content="继续", id="user-1")
    compressed = [SystemMessage(content="internal summary"), user]

    result = _ensure_latest_human_message([user], compressed)

    assert result == compressed