from datetime import datetime
from typing import List, Optional

from redis.asyncio import Redis
from sqlalchemy import select, case
from sqlalchemy.ext.asyncio import AsyncSession

from app.utils.search import apply_keyword_search_stmt
from app.utils.pagination import paginate
from app.core.biz_exception import NotFoundError, PermissionDeniedError, BizLogicError
from app.models.user import VasUser
from app.models.order import VasOrder
from app.models.vas_task import VasTask
from app.models.payment import VasPayment
from app.models.ticket import VasTicket
from app.models.ticket_message import VasTicketMessage
from app.schemas.ticket import VasTicketCreate
from app.services.notification_service import NotificationService
from app.services.webhook_service import WebhookService

class TicketService:

    @staticmethod
    async def create(
        db: AsyncSession,
        data: VasTicketCreate,
        current_user: VasUser,
        redis_client: Redis
    ):
        ticket = VasTicket(
            **data.dict(),
            user_id=current_user.id,
            status="pending",
            created_at=datetime.utcnow(),
            updated_at=datetime.utcnow(),
        )

        db.add(ticket)
        await db.commit()
        await db.refresh(ticket)
        
        formatted_time = ticket.created_at.strftime('%Y-%m-%d %H:%M') + " (UTC)"
        await NotificationService.post_message(
            db=db,
            channel="email",
            payload={
                "template_id": "ticket_created",
                "receiver": current_user.email,
                "payload": {
                    "app_name": "TextSkin",
                    "username": current_user.email,
                    "ticket_id": ticket.id,
                    "ticket_type": ticket.type,
                    "ticket_url": "https://text.skin/dashboard",
                    "created_at": formatted_time
                }
            },
        )

        return ticket

    @staticmethod
    async def update_status(
        db: AsyncSession,
        ticket_id: int,
        status: str,
        comment: str,
        admin_id: str,
    ) -> VasTicket:

        result = await db.execute(
            select(VasTicket)
            .where(VasTicket.id == ticket_id)
            .with_for_update()
        )
        ticket = result.scalar_one_or_none()

        if not ticket:
            raise NotFoundError("Ticket not exist")

        ticket.status = status
        ticket.admin_comment = comment
        ticket.updated_at = datetime.utcnow()

        db.add(
            VasTicketMessage(
                ticket_id=ticket.id,
                sender_type="admin",
                sender_id=str(admin_id),
                content=comment,
                created_at=datetime.utcnow(),
            )
        )

        if status == "resolved":
            await TicketService._handle_resolution(db, ticket)

        elif status == "rejected":
            await TicketService._handle_rejection(db, ticket)

        await db.commit()
        await db.refresh(ticket)
        return ticket

    # =========================
    # 工单解决逻辑
    # =========================
    @staticmethod
    async def _handle_resolution(
        db: AsyncSession,
        ticket: VasTicket,
    ) -> None:

        if not ticket.order_id:
            return

        result = await db.execute(
            select(VasOrder)
            .where(VasOrder.id == ticket.order_id)
            .with_for_update()
        )
        order = result.scalar_one_or_none()
        if not order:
            return

        # ---------- 退款 ----------
        if ticket.type == "refund":
            order.status = "closed"

            pay_res = await db.execute(
                select(VasPayment).where(
                    VasPayment.order_id == order.id,
                    VasPayment.status.in_(["succeeded", "late_paid"]),
                )
            )
            payment = pay_res.scalar_one_or_none()
            if payment:
                payment.status = "refunded"
                payment.refunded_at = datetime.utcnow()
                payment.refund_reason = ticket.reason

            task_res = await db.execute(
                select(VasTask).where(
                    VasTask.order_id == order.id,
                    VasTask.status.in_(["pending", "grabbed", "running", "pause", "completed"]),
                )
            )
            for task in task_res.scalars().all():
                task.status = "cancelled"

    # =========================
    # 工单拒绝逻辑
    # =========================
    @staticmethod
    async def _handle_rejection(
        db: AsyncSession,
        ticket: VasTicket,
    ) -> None:

        if not ticket.order_id:
            return

        result = await db.execute(
            select(VasOrder)
            .where(VasOrder.id == ticket.order_id)
            .with_for_update()
        )
        order = result.scalar_one_or_none()
        if not order:
            return

        # if ticket.type == "refund" and order.status == "refund_pending":
        #     order.status = "paid"

    @staticmethod
    async def add_message(
        db: AsyncSession,
        ticket_id: int,
        sender_type: str,   # "user" | "admin" | "system"
        sender_id: Optional[str] = None,
        content: str = "",
        attachments: Optional[dict] = None,
    ):
        ticket = await db.get(VasTicket, ticket_id)
        if not ticket:
            raise NotFoundError("Ticket not exist")

        message = VasTicketMessage(
            ticket_id=ticket_id,
            sender_type=sender_type,
            sender_id=sender_id,
            content=content,
            attachments=attachments,
            created_at=datetime.utcnow(),
        )

        db.add(message)
        ticket.updated_at = datetime.utcnow()

        await db.commit()
        await db.refresh(message)
        return message

    @staticmethod
    async def list_messages(
        db: AsyncSession,
        ticket_id: int,
        page: int = 1,
        size: int = 20,
    ):
        # 校验 ticket 是否存在
        exists = await db.scalar(
            select(VasTicket.id).where(VasTicket.id == ticket_id)
        )
        if not exists:
            raise NotFoundError("Ticket not exist")

        stmt = (
            select(VasTicketMessage)
            .where(VasTicketMessage.ticket_id == ticket_id)
            .order_by(VasTicketMessage.created_at.desc())
        )

        return await paginate(db, stmt, page, size)

    @staticmethod
    async def list_by_user(
        db: AsyncSession,
        user_id: str,
        page: int = 1,
        size: int = 20,
        keyword: Optional[str] = None,
    ):
        stmt = select(VasTicket).where(VasTicket.user_id == user_id)

        stmt = apply_keyword_search_stmt(
            stmt=stmt,
            model=VasTicket,
            keyword=keyword,
            fields=["order_id", "user_id", "reason", "admin_comment"],
        )

        stmt = stmt.order_by(VasTicket.id.desc())

        return await paginate(db, stmt, page, size)

    @staticmethod
    async def list_all(
        db: AsyncSession,
        page: int = 1,
        size: int = 20,
        keyword: Optional[str] = None,
    ):
        stmt = select(VasTicket)

        # 关键词搜索
        stmt = apply_keyword_search_stmt(
            stmt=stmt,
            model=VasTicket,
            keyword=keyword,
            fields=["order_id", "user_id", "reason", "admin_comment"],
        )

        # 排序：未解决优先 ('pending','info_required') -> 0, 已解决 ('resolved','rejected') -> 1
        stmt = stmt.order_by(
            case(
                (VasTicket.status.in_(["pending", "info_required"]), 0),
                else_=1
            ),
            VasTicket.id.desc()
        )

        return await paginate(db, stmt, page, size)