"""会话树 fork 单元与端点测试（T-M1，采纳 pi 会话树 id/parentId 设计）。"""
import pytest

pytest.importorskip("fastapi")
pytest.importorskip("httpx")

from fastapi.testclient import TestClient

import gateway.agent as ag
import gateway.api as ga
from gateway.agent import AgentSession, SessionStore


def _mk_turn(rid: str, task: str) -> dict:
    return {"request_id": rid, "task": task, "response": f"ans-{rid}",
            "state": "done", "tool_calls": [], "tokens": 10,
            "error": None, "ts": 0.0}


def test_fork_copies_turns_and_keeps_lineage(tmp_path):
    """值拷贝历史轮次 + 记录 parent_id/fork_point 血统。"""
    store = SessionStore(root=tmp_path / "sessions")
    src = store.create("源会话", "ws")
    src.data["turns"] = [_mk_turn("t1", "任务一"), _mk_turn("t2", "任务二")]
    store.save(src)

    forked = store.fork(src.data["id"], turn_index=0, title="分叉A")
    assert forked is not None
    assert forked.data["id"] != src.data["id"]
    assert forked.data["parent_id"] == src.data["id"]
    assert forked.data["fork_point"] == 0
    assert [t["request_id"] for t in forked.data["turns"]] == ["t1"]
    # 原会话不变
    assert len(store.get(src.data["id"]).data["turns"]) == 2


def test_fork_default_takes_all_turns(tmp_path):
    """缺省 turn_index = 全部已完结轮次。"""
    store = SessionStore(root=tmp_path / "sessions")
    src = store.create("源", "ws")
    src.data["turns"] = [_mk_turn("t1", "a"), _mk_turn("t2", "b")]
    store.save(src)
    forked = store.fork(src.data["id"])
    assert len(forked.data["turns"]) == 2
    assert forked.data["fork_point"] == 1


def test_fork_out_of_range_returns_none(tmp_path):
    """turn_index 越界 / 源会话不存在 -> None（端点映射 404）。"""
    store = SessionStore(root=tmp_path / "sessions")
    src = store.create("源", "ws")
    src.data["turns"] = [_mk_turn("t1", "a")]
    store.save(src)
    assert store.fork(src.data["id"], turn_index=5) is None
    assert store.fork(src.data["id"], turn_index=-2) is None
    assert store.fork("as-not-exist") is None


def test_fork_is_deep_copy(tmp_path):
    """fork 后修改新会话不影响原会话（值拷贝语义）。"""
    store = SessionStore(root=tmp_path / "sessions")
    src = store.create("源", "ws")
    src.data["turns"] = [_mk_turn("t1", "a")]
    store.save(src)
    forked = store.fork(src.data["id"])
    forked.data["turns"][0]["task"] = "被篡改"
    forked.data["turns"].append(_mk_turn("t2", "新轮"))
    assert store.get(src.data["id"]).data["turns"][0]["task"] == "a"
    assert len(store.get(src.data["id"]).data["turns"]) == 1


def test_old_sessions_without_lineage_fields_compatible(tmp_path):
    """旧数据无 parent_id/fork_point 字段自然兼容（dict.get 语义，零迁移）。"""
    store = SessionStore(root=tmp_path / "sessions")
    sess = AgentSession({"id": "as-legacy", "title": "旧", "turns": []})
    store.save(sess)
    assert store.get("as-legacy").data.get("parent_id", "") == ""


def test_fork_endpoint(tmp_path, monkeypatch):
    """POST /agent/sessions/{sid}/fork：端到端 200 + 404。"""
    ag.reset_session_store()
    monkeypatch.setattr(ag, "_session_store", SessionStore(root=tmp_path / "sessions"))
    store = ag._session_store
    src = store.create("源", "ws")
    src.data["turns"] = [_mk_turn("t1", "a")]
    store.save(src)

    client = TestClient(ga.app)
    r = client.post(f"/agent/sessions/{src.data['id']}/fork",
                    json={"turn_index": 0, "title": "端点分叉"})
    assert r.status_code == 200
    data = r.json()
    assert data["parent_id"] == src.data["id"]
    assert data["title"] == "端点分叉"

    r404 = client.post("/agent/sessions/as-not-exist/fork", json={})
    assert r404.status_code == 404