ForcePilot/backend/package/yuxi/external_systems/integrations/servicenow/operations.py

"""ServiceNow discover / preview_tools / create_tools handler 实现。

handler 签名遵循 ``OperationHandler`` 协议：
``(source_type: str, system_config: dict[str, Any]) -> Awaitable[Any]``。

handler 内部职责：
1. 从 ``system_config`` 提取 ``base_url`` / ``api_version`` / ``_resolved_token`` 等
2. 构建 ``auth_headers``（token 由 use_cases 层注入到 ``system_config["_resolved_token"]``）
3. 构造带 429 退避的 ``request_fn``，注入到生成器 payload
4. 调用 ``ServiceNowSourceGenerator.generate(payload)``

429 退避分层（见设计文档 §6.2 / §8.2）：
- discover/preview/create 阶段：本模块 ``_request_with_retry`` 实现（解析 Retry-After）
- 运行时工具执行：通过工具 ``retry_policy.retry_status_codes: [429]`` 配置
"""

from __future__ import annotations

import asyncio
from collections.abc import Awaitable, Callable
from typing import TYPE_CHECKING, Any

from yuxi.external_systems.exceptions import (
    AuthError,
    DomainValidationError,
    ExecutionError,
    RateLimitExceededError,
)
from yuxi.external_systems.integrations.schemas import GeneratedToolsDraft
from yuxi.external_systems.integrations.servicenow.error_extractor import (
    map_servicenow_error,
)
from yuxi.external_systems.integrations.servicenow.generators import (
    ServiceNowSourceGenerator,
)

if TYPE_CHECKING:
    import httpx

# discover/preview/create 阶段 429 退避参数
_RETRY_MAX_ATTEMPTS = 5
_RETRY_BASE_DELAY = 1.0

# ServiceNow 通用请求头（除 Authorization 外）
_SERVICENOW_HEADERS: dict[str, str] = {
    "Accept": "application/json",
}


def _build_auth_headers(system_config: dict[str, Any]) -> dict[str, str]:
    """从 system_config 提取 token，构建 ServiceNow 请求头。

    system_config 中 token 由 use_cases 层通过 ``token_manager.get_token`` 预处理后
    注入到 ``system_config["_resolved_token"]["access_token"]``。handler 不自行换取
    token——token 获取是 use_cases 层的职责。
    """
    token_info = system_config.get("_resolved_token")
    if not isinstance(token_info, dict) or not token_info.get("access_token"):
        raise AuthError("servicenow: system_config 缺少 _resolved_token，use_cases 层未注入 token")
    access_token = token_info["access_token"]
    headers = dict(_SERVICENOW_HEADERS)
    headers["Authorization"] = f"Bearer {access_token}"
    headers["Content-Type"] = "application/json"
    return headers


def _resolve_base_url(system_config: dict[str, Any]) -> str:
    """从 system_config 提取 base_url，支持 instance 动态拼接。"""
    connection_config = system_config.get("connection_config") or {}
    base_url = connection_config.get("base_url")
    instance = connection_config.get("instance")
    if not base_url and instance:
        base_url = f"https://{instance}.service-now.com"
    if not base_url:
        raise DomainValidationError("servicenow: system_config.connection_config.base_url 或 instance 至少需填写一项")
    return str(base_url)


def _resolve_api_version(system_config: dict[str, Any]) -> str | None:
    """从 system_config 提取 api_version。"""
    connection_config = system_config.get("connection_config") or {}
    return connection_config.get("api_version")


def _resolve_tables(system_config: dict[str, Any]) -> list[str] | None:
    """从 system_config.discovery_options.tables 提取待生成的表名列表。"""
    discovery_options = system_config.get("discovery_options") or {}
    return discovery_options.get("tables")


async def _request_with_retry(
    method: str,
    url: str,
    headers: dict[str, str],
    *,
    max_retries: int = _RETRY_MAX_ATTEMPTS,
    base_delay: float = _RETRY_BASE_DELAY,
) -> httpx.Response:
    """handler 内部 HTTP 调用的 429 退避（仅用于 discover/preview/create 阶段）。

    优先使用响应头 ``Retry-After``，否则指数退避（``base_delay * 2 ** attempt``）。
    运行时工具执行的 429 退避由框架 executor + 工具 retry_policy 处理，
    不在此函数范围内。

    非 2xx 响应（非 429）通过 ``map_servicenow_error`` 转换为 ExternalSystemError 子类。
    网络层异常（超时 / 连接错误）转换为 ``ExecutionError``。
    """
    import httpx

    try:
        async with httpx.AsyncClient() as client:
            last_response: httpx.Response | None = None
            for attempt in range(max_retries + 1):
                response = await client.request(method, url, headers=headers)
                if response.status_code != 429:
                    last_response = response
                    break
                if attempt == max_retries:
                    retry_after_header = response.headers.get("Retry-After", "60")
                    try:
                        retry_after = int(retry_after_header)
                    except ValueError:
                        retry_after = 60
                    raise RateLimitExceededError(
                        f"ServiceNow 限流，已重试 {max_retries} 次仍失败: {url}",
                        retry_after=retry_after,
                        limit_type="qps",
                    )
                # 优先使用 Retry-After 头，否则指数退避
                retry_after_header = response.headers.get("Retry-After")
                if retry_after_header:
                    try:
                        delay = float(retry_after_header)
                    except ValueError:
                        delay = base_delay * (2**attempt)
                else:
                    delay = base_delay * (2**attempt)
                await asyncio.sleep(delay)
    except httpx.RequestError as exc:
        raise ExecutionError(f"ServiceNow 网络请求失败: {exc}") from exc

    assert last_response is not None
    if last_response.is_success:
        return last_response
    # 非 2xx：解析错误 body 并映射为 ExternalSystemError 子类
    try:
        error_body = last_response.json()
    except Exception:
        error_body = {"error": {"message": last_response.text}}
    raise map_servicenow_error(last_response.status_code, error_body)


def _make_request_fn() -> Callable[[str, str, dict[str, str]], Awaitable[httpx.Response]]:
    """构造带 429 退避的 request_fn，供 ServiceNowMetadataClient 使用。"""

    async def request_fn(method: str, url: str, headers: dict[str, str]) -> httpx.Response:
        return await _request_with_retry(method, url, headers)

    return request_fn


def _build_generator_payload(system_config: dict[str, Any]) -> dict[str, Any]:
    """从 system_config 构造生成器 payload。

    生成器 payload 是 system_config 的子集，包含：
    - base_url: str
    - auth_headers: dict[str, str]
    - auth_config: dict — 透传到工具的 auth_config 字段
    - auth_type: str — 透传到工具的 auth_type 字段
    - api_version: str | None
    - tables: list[str] | None
    - request_fn: 带 429 退避的 HTTP 请求函数
    """
    return {
        "base_url": _resolve_base_url(system_config),
        "auth_headers": _build_auth_headers(system_config),
        "auth_config": system_config.get("auth_config") or {},
        "auth_type": system_config.get("auth_type", "oauth2_client_credentials"),
        "api_version": _resolve_api_version(system_config),
        "tables": _resolve_tables(system_config),
        "request_fn": _make_request_fn(),
    }


async def discover_servicenow(
    source_type: str,
    system_config: dict[str, Any],
) -> list[dict[str, Any]]:
    """discover handler：发现 ServiceNow 实例可用表（sys_db_object）。

    Returns:
        表摘要列表，每项含 ``name`` / ``label``。
    """
    from yuxi.external_systems.integrations.servicenow.metadata_discovery import (
        ServiceNowMetadataClient,
    )

    base_url = _resolve_base_url(system_config)
    auth_headers = _build_auth_headers(system_config)
    request_fn = _make_request_fn()
    client = ServiceNowMetadataClient(
        base_url=base_url,
        auth_headers=auth_headers,
        request_fn=request_fn,
    )
    options = system_config.get("discovery_options") or {}
    tables = await client.list_tables(
        include_patterns=options.get("include_patterns"),
        exclude_patterns=options.get("exclude_patterns"),
    )
    return [{"name": t["name"], "label": t.get("label", t["name"])} for t in tables]


async def preview_servicenow_tools(
    source_type: str,
    system_config: dict[str, Any],
) -> list[dict[str, Any]]:
    """preview_tools handler：预览将生成的工具列表（不持久化）。

    Returns:
        工具预览列表，每项为 ExternalToolCreateInput 兼容的 dict 摘要。
    """
    payload = _build_generator_payload(system_config)
    generator = ServiceNowSourceGenerator()
    tools = await generator.generate(payload)
    return [{"slug": t["slug"], "name": t["name"], "description": t["description"]} for t in tools]


async def create_servicenow_tools(
    source_type: str,
    system_config: dict[str, Any],
) -> GeneratedToolsDraft:
    """create_tools handler：生成工具草稿（不直接持久化）。

    Returns:
        GeneratedToolsDraft，由 use_cases 层统一持久化。
    """
    payload = _build_generator_payload(system_config)
    generator = ServiceNowSourceGenerator()
    tool_configs = await generator.generate(payload)
    return GeneratedToolsDraft(tool_configs=tool_configs, override_existing=False)