"""审计日志服务（迭代第 3 轮）。

**为什么需要**：`AuditLog` 模型在阶段 1 就定义了，但**全项目没有写入过一条**——
意味着过账、强制放行、改价这些关键操作没有任何追溯记录。对财务/合规场景这是硬缺口
（客户问"这张单谁改的价"时答不上来）。

设计原则：
1. **记录"有后果"的操作**，不是所有 CRUD（否则日志淹没在噪音里）：
   - 单据状态变更（过账/作废）
   - 越过管控（信用超限强制放行、低于最低售价放行、超配额）
   - 金额相关变更（改价、抹零）
   - 权限相关（API Key 签发、商城账号开通、套餐变更）
2. **写入失败绝不影响主业务**（审计是旁路，不能因为日志问题让开单失败）；
3. 携带足够的上下文以便事后追责：谁、何时、对什么、改了什么、从什么到什么。
"""

from __future__ import annotations

import logging
from typing import Optional

from .models import AuditLog

logger = logging.getLogger("dealerhub.audit")


# 业务动作常量（比通用 CRUD 更精确，便于按动作筛选）
ACTION_POST = "post"              # 过账/确认
ACTION_CANCEL = "cancel"          # 作废/取消
ACTION_FORCE = "force"            # 越过管控放行
ACTION_PRICE_OVERRIDE = "price_override"   # 改价
ACTION_QUOTA_EXCEEDED = "quota_exceeded"   # 配额超限尝试
ACTION_ISSUE = "issue"            # 签发（API Key / 商城账号）
ACTION_PLAN_CHANGE = "plan_change"         # 套餐变更
ACTION_SEED = "seed"              # 数据初始化

# 为了复用 AuditLog.ACTION_CHOICES 的既有选择，把上述动作归入既有类别
_ACTION_TO_CHOICE = {
    ACTION_POST: "update",
    ACTION_CANCEL: "update",
    ACTION_FORCE: "update",
    ACTION_PRICE_OVERRIDE: "update",
    ACTION_QUOTA_EXCEEDED: "view",
    ACTION_ISSUE: "create",
    ACTION_PLAN_CHANGE: "update",
    ACTION_SEED: "create",
}


def log(
    *,
    tenant,
    action: str,
    target_type: str,
    target_id: str = "",
    detail: Optional[dict] = None,
    user=None,
    request=None,
    ip: str = "",
    user_agent: str = "",
) -> Optional[AuditLog]:
    """写一条审计日志。**任何异常都被吞掉**（旁路，不影响主业务）。

    request 可选：给了就自动提取 user / ip / user_agent。
    """
    try:
        # 服务层通常没有 request：从 contextvar 兜底取（中间件注入）
        if request is None:
            try:
                from .context import current_request

                request = current_request()
            except Exception:
                request = None

        if request is not None:
            req_user = getattr(request, "user", None)
            if user is None and req_user is not None and getattr(req_user, "is_authenticated", False):
                user = req_user
            if not ip:
                xff = request.META.get("HTTP_X_FORWARDED_FOR", "")
                ip = (xff.split(",")[0].strip() if xff
                      else request.META.get("REMOTE_ADDR", "")) or ""
            if not user_agent:
                user_agent = request.META.get("HTTP_USER_AGENT", "")[:255]

        return AuditLog.objects.create(
            tenant=tenant,
            user=user if (user is not None and getattr(user, "pk", None)) else None,
            action=_ACTION_TO_CHOICE.get(action, "update"),
            target_type=target_type[:64],
            target_id=str(target_id)[:64],
            detail={"business_action": action, **(detail or {})},
            ip=ip or None,
            user_agent=user_agent or "",
        )
    except Exception as exc:      # 审计失败不能影响业务
        logger.warning("写审计日志失败（已忽略）: %s · action=%s target=%s",
                       exc, action, target_type)
        return None


# ------------------------------------------------------------
# 便捷包装（业务侧调用这些，语义更清晰）
# ------------------------------------------------------------

def log_bill_posted(*, tenant, bill, user=None, request=None,
                    extra: Optional[dict] = None) -> None:
    """单据过账。"""
    log(
        tenant=tenant,
        action=ACTION_POST,
        target_type=bill.__class__.__name__,
        target_id=bill.bill_no,
        user=user,
        request=request,
        detail={
            "bill_no": bill.bill_no,
            "amount": str(getattr(bill, "total_amount", "")),
            "customer": getattr(getattr(bill, "customer", None), "code", ""),
            **(extra or {}),
        },
    )


def log_bill_cancelled(*, tenant, bill, reason: str = "", user=None, request=None) -> None:
    """单据作废/取消。"""
    log(
        tenant=tenant,
        action=ACTION_CANCEL,
        target_type=bill.__class__.__name__,
        target_id=getattr(bill, "bill_no", str(bill.pk)),
        user=user,
        request=request,
        detail={"reason": reason},
    )


def log_force_release(*, tenant, kind: str, target: str, detail: dict,
                      user=None, request=None) -> None:
    """越过管控放行（信用超限 / 低于最低售价 / 超配额）。"""
    log(
        tenant=tenant,
        action=ACTION_FORCE,
        target_type=kind,
        target_id=target,
        user=user,
        request=request,
        detail=detail,
    )


def log_price_override(*, tenant, product_code: str, from_price, to_price,
                       bill_no: str = "", user=None, request=None) -> None:
    """改价（记录原价与新价）。"""
    log(
        tenant=tenant,
        action=ACTION_PRICE_OVERRIDE,
        target_type="Product",
        target_id=product_code,
        user=user,
        request=request,
        detail={"bill_no": bill_no, "from": str(from_price), "to": str(to_price)},
    )


def log_plan_change(*, tenant, from_plan: str, to_plan: str,
                    user=None, request=None) -> None:
    log(
        tenant=tenant,
        action=ACTION_PLAN_CHANGE,
        target_type="Subscription",
        target_id=tenant.code if hasattr(tenant, "code") else str(tenant),
        user=user,
        request=request,
        detail={"from": from_plan, "to": to_plan},
    )


def query_logs(tenant, *, target_type: str = "", target_id: str = "",
               action: str = "", limit: int = 100) -> list:
    """按目标查审计轨迹（"这张单都发生了什么"）。"""
    qs = AuditLog.objects.filter(tenant=tenant)
    if target_type:
        qs = qs.filter(target_type=target_type)
    if target_id:
        qs = qs.filter(target_id=str(target_id))
    if action:
        qs = qs.filter(detail__business_action=action)
    return list(qs.order_by("-created_at")[:limit])