"""backend/session.py 单元测试 — 会话 CRUD + 原子写入。

覆盖:
  - 创建/加载/保存/删除/列出
  - 原子写入（tempfile + os.replace）
  - 边界情况（不存在会话、损坏 JSON、空名称自动填充）
"""

import json
import os
import sys
import tempfile
import time
from pathlib import Path

import pytest

sys.path.insert(0, str(Path(__file__).parent.parent))

from backend.session import (
    create_session,
    load_session,
    save_session,
    get_session_state,
    list_all_sessions,
    delete_session,
    generate_session_id,
    SESSIONS_DIR,
)


@pytest.fixture
def temp_sessions_dir(monkeypatch):
    with tempfile.TemporaryDirectory(prefix="test_sessions_") as tmpdir:
        monkeypatch.setattr("backend.session.SESSIONS_DIR", Path(tmpdir))
        yield Path(tmpdir)


# ── create_session ──────────────────────────────────────────────

class TestCreateSession:
    def test_creates_with_defaults(self, temp_sessions_dir):
        s = create_session()
        assert len(s["session_id"]) == 12
        assert "新建报表" in s["session_name"]
        assert s["created_at"]
        assert s["updated_at"]

    def test_custom_name(self, temp_sessions_dir):
        s = create_session(name="测试报表")
        assert s["session_name"] == "测试报表"

    def test_agent_state_preserved(self, temp_sessions_dir):
        s = create_session(agent_state={"current_jrxml": "<x/>"})
        assert s["agent_state"]["current_jrxml"] == "<x/>"

    def test_session_id_injected_into_agent_state(self, temp_sessions_dir):
        s = create_session()
        assert s["agent_state"]["session_id"] == s["session_id"]

    def test_persists_json_to_disk(self, temp_sessions_dir):
        s = create_session(name="磁盘测试")
        fp = temp_sessions_dir / f"{s['session_id']}.json"
        assert fp.exists()
        loaded = json.loads(fp.read_text("utf-8"))
        assert loaded["session_name"] == "磁盘测试"

    def test_unique_ids_no_collision(self, temp_sessions_dir):
        ids = {generate_session_id() for _ in range(100)}
        assert len(ids) == 100

    def test_creates_sessions_dir_if_missing(self, temp_sessions_dir):
        nested = temp_sessions_dir / "nested" / "sub"
        import backend.session as mod

        monkeypatch = pytest.MonkeyPatch()
        monkeypatch.setattr(mod, "SESSIONS_DIR", nested)
        s = create_session()
        assert nested.exists()
        assert (nested / f"{s['session_id']}.json").exists()


# ── load_session ────────────────────────────────────────────────

class TestLoadSession:
    def test_returns_none_for_missing(self, temp_sessions_dir):
        assert load_session("nonexistent_id") is None

    def test_loads_existing(self, temp_sessions_dir):
        created = create_session(name="加载测试")
        loaded = load_session(created["session_id"])
        assert loaded["session_name"] == "加载测试"
        assert loaded["session_id"] == created["session_id"]

    def test_load_includes_agent_state(self, temp_sessions_dir):
        created = create_session(agent_state={"field_count": 5})
        loaded = load_session(created["session_id"])
        assert loaded["agent_state"]["field_count"] == 5


# ── save_session ────────────────────────────────────────────────

class TestSaveSession:
    def test_updates_name_and_state(self, temp_sessions_dir):
        created = create_session(name="原始")
        save_session(created["session_id"], {"new_key": True}, session_name="更新")
        loaded = load_session(created["session_id"])
        assert loaded["session_name"] == "更新"
        assert loaded["agent_state"]["new_key"] is True

    def test_preserves_created_at(self, temp_sessions_dir):
        created = create_session()
        original = created["created_at"]
        save_session(created["session_id"], {"x": 1})
        assert load_session(created["session_id"])["created_at"] == original

    def test_updates_updated_at(self, temp_sessions_dir):
        created = create_session()
        time.sleep(0.01)
        save_session(created["session_id"], {"x": 1})
        loaded = load_session(created["session_id"])
        assert loaded["updated_at"] != created["updated_at"]

    def test_atomic_write_produces_valid_json(self, temp_sessions_dir):
        created = create_session()
        save_session(created["session_id"], {"data": "x" * 1000})
        fp = temp_sessions_dir / f"{created['session_id']}.json"
        data = json.loads(fp.read_text("utf-8"))
        assert data["agent_state"]["data"] == "x" * 1000

    def test_auto_generates_name_when_empty(self, temp_sessions_dir):
        created = create_session(name="")
        save_session(created["session_id"], {"x": 1})
        assert load_session(created["session_id"])["session_name"]

    def test_keeps_existing_name_when_not_provided(self, temp_sessions_dir):
        created = create_session(name="原名")
        save_session(created["session_id"], {"x": 1})
        assert load_session(created["session_id"])["session_name"] == "原名"

    def test_fills_missing_created_at(self, temp_sessions_dir):
        sid = "test_no_created"
        fp = temp_sessions_dir / f"{sid}.json"
        fp.write_text(
            json.dumps({"session_id": sid, "session_name": "旧数据"}), "utf-8"
        )
        save_session(sid, {"x": 1})
        assert load_session(sid)["created_at"]


# ── get_session_state ───────────────────────────────────────────

class TestGetSessionState:
    def test_none_for_missing(self, temp_sessions_dir):
        assert get_session_state("missing") is None

    def test_returns_all_keys(self, temp_sessions_dir):
        created = create_session(name="状态测试")
        state = get_session_state(created["session_id"])
        for key in ("session_id", "session_name", "agent_state", "created_at", "updated_at"):
            assert key in state


# ── list_all_sessions ───────────────────────────────────────────

class TestListAllSessions:
    def test_empty_when_no_sessions(self, temp_sessions_dir):
        assert list_all_sessions() == []

    def test_lists_all_created(self, temp_sessions_dir):
        s1 = create_session(name="A")
        s2 = create_session(name="B")
        ids = {s["session_id"] for s in list_all_sessions()}
        assert s1["session_id"] in ids
        assert s2["session_id"] in ids

    def test_summary_excludes_agent_state(self, temp_sessions_dir):
        create_session(agent_state={"secret": True})
        result = list_all_sessions()
        assert "agent_state" not in result[0]

    def test_sorted_by_mtime_desc(self, temp_sessions_dir):
        s1 = create_session(name="先")
        time.sleep(0.02)
        s2 = create_session(name="后")
        assert list_all_sessions()[0]["session_id"] == s2["session_id"]

    def test_skips_corrupt_json(self, temp_sessions_dir):
        (temp_sessions_dir / "bad.json").write_text("{not json}", "utf-8")
        create_session(name="正常")
        assert len(list_all_sessions()) == 1


# ── delete_session ──────────────────────────────────────────────

class TestDeleteSession:
    def test_returns_false_for_missing(self, temp_sessions_dir):
        assert delete_session("ghost_id") is False

    def test_returns_true_and_removes(self, temp_sessions_dir):
        created = create_session()
        assert delete_session(created["session_id"]) is True
        assert load_session(created["session_id"]) is None

    def test_file_is_removed_from_disk(self, temp_sessions_dir):
        created = create_session()
        fp = temp_sessions_dir / f"{created['session_id']}.json"
        assert fp.exists()
        delete_session(created["session_id"])
        assert not fp.exists()