"""Standard library queries and administrator maintenance."""

from __future__ import annotations

import hashlib
import math
from datetime import UTC, datetime
from typing import Any

from sqlalchemy import func, or_, select
from sqlalchemy.ext.asyncio import AsyncSession

from app.core.exceptions import AppException
from app.models.entities import OperationAudit, StandardRule, UserAccount
from app.schemas.standards import (
    StandardCategoryCount,
    StandardRuleCreate,
    StandardRuleDetail,
    StandardRuleListData,
    StandardRuleSummary,
    StandardRuleUpdate,
)


class StandardLibraryService:
    categories = ("内料", "包材", "包装", "法规")

    def __init__(self, session: AsyncSession) -> None:
        self.session = session

    async def list(
        self,
        *,
        keyword: str | None = None,
        category: str = "all",
        status: str = "启用",
        page: int = 1,
        page_size: int = 20,
    ) -> StandardRuleListData:
        filters = self._filters(keyword=keyword, category=category, status=status)
        total = int(await self.session.scalar(select(func.count()).select_from(StandardRule).where(*filters)) or 0)
        statement = (
            select(StandardRule)
            .where(*filters)
            .order_by(StandardRule.category_lv1, StandardRule.id)
            .offset((page - 1) * page_size)
            .limit(page_size)
        )
        rows = list(await self.session.scalars(statement))
        category_counts = await self._category_counts(keyword=keyword, status=status)
        return StandardRuleListData(
            items=[self.to_summary(row) for row in rows],
            total=total,
            page=page,
            page_size=page_size,
            total_pages=math.ceil(total / page_size) if total else 0,
            category_counts=category_counts,
        )

    async def get(self, rule_id: int) -> StandardRuleDetail:
        row = await self.session.get(StandardRule, rule_id)
        if row is None:
            raise AppException("标准条目不存在", code=404, status_code=404)
        return self.to_detail(row)

    async def create(self, payload: StandardRuleCreate, user: UserAccount) -> StandardRuleDetail:
        row = StandardRule(
            **payload.model_dump(),
            import_fingerprint=self._manual_fingerprint(payload),
            updated_at=datetime.now(UTC),
        )
        self.session.add(row)
        await self.session.flush()
        await self._audit(user, "standard.create", row.id)
        return self.to_detail(row)

    async def update(self, rule_id: int, payload: StandardRuleUpdate, user: UserAccount) -> StandardRuleDetail:
        row = await self.session.get(StandardRule, rule_id)
        if row is None:
            raise AppException("标准条目不存在", code=404, status_code=404)
        for key, value in payload.model_dump(exclude_unset=True).items():
            setattr(row, key, value)
        row.updated_at = datetime.now(UTC)
        await self._audit(user, "standard.update", row.id, {"fields": list(payload.model_fields_set)})
        await self.session.flush()
        return self.to_detail(row)

    async def _category_counts(self, *, keyword: str | None, status: str) -> list[StandardCategoryCount]:
        filters = self._filters(keyword=keyword, category="all", status=status)
        rows = await self.session.execute(
            select(StandardRule.category_lv1, func.count())
            .where(*filters)
            .group_by(StandardRule.category_lv1)
        )
        counts = dict(rows.all())
        return [
            StandardCategoryCount(category=category, count=int(counts.get(category, 0)))
            for category in self.categories
        ]

    @staticmethod
    def _filters(*, keyword: str | None, category: str, status: str) -> list[Any]:
        filters: list[Any] = []
        if category != "all":
            if category not in StandardLibraryService.categories:
                raise AppException("无效的标准类目", code=422, status_code=422)
            filters.append(StandardRule.category_lv1 == category)
        if status != "all":
            if status not in {"启用", "停用"}:
                raise AppException("无效的标准状态", code=422, status_code=422)
            filters.append(StandardRule.status == status)
        if keyword and keyword.strip():
            pattern = f"%{keyword.strip()}%"
            filters.append(
                or_(
                    StandardRule.category_lv1.ilike(pattern),
                    StandardRule.category_lv2.ilike(pattern),
                    StandardRule.category_lv3.ilike(pattern),
                    StandardRule.risk_point.ilike(pattern),
                    StandardRule.judge_standard.ilike(pattern),
                    StandardRule.regulation.ilike(pattern),
                )
            )
        return filters

    async def _audit(self, user: UserAccount, action: str, rule_id: int, metadata: dict | None = None) -> None:
        self.session.add(
            OperationAudit(
                actor_user_id=user.id,
                actor_emp_no=user.emp_no,
                action=action,
                resource_type="standard_rule",
                resource_id=str(rule_id),
                audit_metadata=metadata or {},
            )
        )

    @staticmethod
    def _manual_fingerprint(payload: StandardRuleCreate) -> str:
        content = "\x1f".join(str(value or "") for value in payload.model_dump().values())
        return hashlib.sha256(f"manual\x1f{content}".encode()).hexdigest()

    @staticmethod
    def to_summary(row: StandardRule) -> StandardRuleSummary:
        return StandardRuleSummary.model_validate(row, from_attributes=True)

    @staticmethod
    def to_detail(row: StandardRule) -> StandardRuleDetail:
        return StandardRuleDetail.model_validate(row, from_attributes=True)