"""游标校验契约测试（文档 §3.8 游标分页、§16.1 "非法游标返回 400 INVALID_CURSOR"）。

覆盖三层：
1. `parse_cursor` 纯函数的合法/非法取值边界（真源是记录 ID 列类型与"边界必须唯一可解释"）；
2. HTTP 层：非法游标返回 `400 INVALID_CURSOR` 统一错误信封，合法游标照常透传；
3. 判定顺序：认证先于游标校验（未带令牌仍是 401，不因参数非法而变成 400），
   管理面的权限闸门先于游标校验（未授权是 403，且游标校验早于任何数据库访问）。

全部进程内调用，不连数据库：非法游标在数据访问之前就被拒绝，合法路径用替身 Service。
"""

from collections.abc import AsyncIterator
from typing import Any

import pytest
from fastapi import Request
from fastapi.testclient import TestClient

from app.api.dependencies.auth import build_request_context
from app.api.dependencies.database import get_session
from app.core.contracts import RequestContext
from app.core.cursor import MAX_CURSOR_VALUE, parse_cursor
from app.core.errors import ForbiddenAgentError, InvalidCursorError
from app.main import create_app

MESSAGES = "/api/v1/conversations/session-1/messages"
ADMIN_RELEASES = "/api/v1/admin/config-releases"
ADMIN_AUDIT = "/api/v1/admin/audit-records"

# 全部必须被拒绝：非整数、负数、零、浮点、带符号、十六进制、超 BIGINT 上界、
# 内嵌空白、Unicode 数字（`str.isdigit()` 对最后两者为真，是容易漏掉的分支）。
INVALID_CURSORS = [
    "abc", "-1", "0", "1.5", "+5", "0x10", "1e3", "1 2",
    str(MAX_CURSOR_VALUE + 1), "9" * 25, "１", "١٢",
]


def fake_session() -> Any:
    """替身 session：合法路径用替身 Service，根本不会被使用。"""
    return object()


async def override_session() -> AsyncIterator[Any]:
    yield fake_session()


def authenticated_app(
    monkeypatch: pytest.MonkeyPatch, *, permissions: tuple[str, ...] = ("conversation:read",),
    roles: tuple[str, ...] = ("customer",),
) -> TestClient:
    application = create_app()

    async def context(request: Request) -> RequestContext:
        built = RequestContext(user_id="9001", trace_id="trace-cursor",
                              roles=roles, permissions=permissions)
        request.state.request_context = built
        return built

    application.dependency_overrides[build_request_context] = context
    application.dependency_overrides[get_session] = override_session
    return TestClient(application)


# --- 1. 纯函数边界 ---------------------------------------------------------

@pytest.mark.parametrize("raw,expected", [("1", 1), ("42", 42), (" 42 ", 42),
                                          (str(MAX_CURSOR_VALUE), MAX_CURSOR_VALUE)])
def test_valid_cursor_is_parsed_into_boundary(raw: str, expected: int) -> None:
    assert parse_cursor(raw) == expected


@pytest.mark.parametrize("raw", [None, "", "   "])
def test_absent_cursor_means_first_page(raw: str | None) -> None:
    """不带游标（`?cursor=` 空值或纯空白）表示第一页。

    空值不是"非法值"而是"未翻页"的常见写法：把它判 400 会让正常客户端在最后一页
    突然失败，因此这里与"缺参数"同义；真正的非法取值走下面的用例。
    """
    assert parse_cursor(raw) is None


@pytest.mark.parametrize("raw", INVALID_CURSORS)
def test_invalid_cursor_reports_document_code(raw: str) -> None:
    with pytest.raises(InvalidCursorError) as excinfo:
        parse_cursor(raw)

    assert excinfo.value.code == "INVALID_CURSOR"
    assert excinfo.value.status_code == 400
    assert excinfo.value.message  # 必须说明原因，不能是空消息


def test_invalid_cursor_message_explains_reason_without_echoing_input() -> None:
    with pytest.raises(InvalidCursorError) as excinfo:
        parse_cursor("token-<script>")

    assert "十进制数字" in excinfo.value.message
    assert "token-<script>" not in excinfo.value.message  # 不回显客户端可控内容


# --- 2. HTTP 层 ------------------------------------------------------------

@pytest.mark.parametrize("raw", ["abc", "-1", "0", "1.5", "99999999999999999999"])
def test_messages_rejects_invalid_cursor_with_envelope(
    monkeypatch: pytest.MonkeyPatch, raw: str
) -> None:
    with authenticated_app(monkeypatch) as client:
        response = client.get(MESSAGES, params={"cursor": raw})

    assert response.status_code == 400
    body = response.json()
    assert set(body) == {"error", "meta"}
    assert body["error"]["code"] == "INVALID_CURSOR"
    assert body["error"]["retryable"] is False  # 文档 §3.6：该码不可重试
    assert body["error"]["field_errors"] == []
    assert body["meta"]["trace_id"] == "trace-cursor"


def test_messages_forwards_valid_cursor_to_service(monkeypatch: pytest.MonkeyPatch) -> None:
    captured: dict[str, Any] = {}

    class RecordingService:
        def __init__(self, session: Any) -> None:
            del session

        async def messages(
            self, session_id: str, context: RequestContext, limit: int, before: int | None = None
        ) -> dict[str, object]:
            captured.update(session_id=session_id, limit=limit, before=before)
            return {"data": []}

    monkeypatch.setattr("app.api.controllers.conversations.ConversationService", RecordingService)
    with authenticated_app(monkeypatch) as client:
        response = client.get(MESSAGES, params={"cursor": "42", "limit": "5"})

    assert response.status_code == 200
    assert captured == {"session_id": "session-1", "limit": 5, "before": 42}


def test_messages_without_cursor_keeps_first_page_behaviour(
    monkeypatch: pytest.MonkeyPatch
) -> None:
    captured: dict[str, Any] = {}

    class RecordingService:
        def __init__(self, session: Any) -> None:
            del session

        async def messages(
            self, session_id: str, context: RequestContext, limit: int, before: int | None = None
        ) -> dict[str, object]:
            captured.update(before=before, session_id=session_id)
            return {"data": []}

    monkeypatch.setattr("app.api.controllers.conversations.ConversationService", RecordingService)
    with authenticated_app(monkeypatch) as client:
        response = client.get(MESSAGES)

    assert response.status_code == 200
    assert captured["before"] is None  # 合法无游标请求行为不变


def test_authentication_precedes_cursor_validation() -> None:
    """未带令牌 + 非法游标：必须先 401，不能因为参数非法先漏出 400。"""
    application = create_app()
    with TestClient(application) as client:
        response = client.get(MESSAGES, params={"cursor": "abc"})

    assert response.status_code == 401
    assert response.json()["error"]["code"] == "AUTHENTICATION_REQUIRED"


# --- 3. 管理面：权限先于游标，游标先于数据库 ------------------------------

def test_admin_permission_precedes_cursor_validation(monkeypatch: pytest.MonkeyPatch) -> None:
    class DenyingAuth:
        @staticmethod
        async def require(context: RequestContext, permission: str, *, admin: bool = False) -> None:
            del context, permission, admin
            raise ForbiddenAgentError("缺少操作权限")

    monkeypatch.setattr("app.service.admin_service.AuthorizationService", DenyingAuth)
    with authenticated_app(monkeypatch, permissions=("config:read",), roles=("admin",)) as client:
        response = client.get(ADMIN_RELEASES, params={"cursor": "abc"})

    assert response.status_code == 403
    assert response.json()["error"]["code"] == "AGENT_PERMISSION_DENIED"


@pytest.mark.parametrize("path", [ADMIN_RELEASES, ADMIN_AUDIT])
def test_admin_invalid_cursor_fails_before_database_access(
    monkeypatch: pytest.MonkeyPatch, path: str
) -> None:
    class AllowingAuth:
        @staticmethod
        async def require(context: RequestContext, permission: str, *, admin: bool = False) -> None:
            del context, permission, admin

    def exploding_factory() -> Any:
        raise AssertionError("非法游标不应触发任何数据库访问")

    monkeypatch.setattr("app.service.admin_service.AuthorizationService", AllowingAuth)
    monkeypatch.setattr("app.service.admin_service.SessionFactory", exploding_factory)
    with authenticated_app(monkeypatch, permissions=("config:read", "audit:read"),
                           roles=("admin",)) as client:
        response = client.get(path, params={"cursor": "-7"})

    assert response.status_code == 400
    assert response.json()["error"]["code"] == "INVALID_CURSOR"