# =============================================================================
# 企微IT智能服务台 — 分层排队服务
# =============================================================================
# 说明：实现三段排序的排队位置计算和平台统计
#
# 排队三段排序（决策 C1/C2）：
#   段1（VIP）：is_vip = true，不受信息梳理影响
#   段2（已梳理）：is_vip = false AND info_locked = true
#   段3（待梳理）：is_vip = false AND info_locked = false
#
# 段内排序：queue_priority DESC → urgency_score DESC → created_at ASC
# 插队规则（决策 C4）：queue_priority = min(答题数//3, 2)，上限2
# =============================================================================

import logging
from datetime import datetime, timezone
from typing import Any, Dict, List, Optional, Tuple

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

from app.models.conversation import Conversation
from app.models.quiz import EmployeePoints

logger = logging.getLogger(__name__)

# 预估每个排队者的服务时间（秒），用于计算预估等待时间
ESTIMATED_SERVICE_TIME_SEC = 300  # 5分钟/人


class QueueService:
    """分层排队服务。

    提供排队位置计算、平台统计、坐席端看板数据等功能。
    """

    # ======================================================================
    # 段位判定
    # ======================================================================

    @staticmethod
    def _determine_segment(conversation: Conversation) -> str:
        """判定会话属于哪个排队段位。

        Args:
            conversation: 会话对象

        Returns:
            str: "vip" / "completed" / "incomplete"
        """
        if conversation.is_vip:
            return "vip"
        elif conversation.info_locked:
            return "completed"
        else:
            return "incomplete"

    # ======================================================================
    # 排队位置计算
    # ======================================================================

    async def calculate_queue_position(
        self, db: AsyncSession, conversation: Conversation
    ) -> Dict[str, Any]:
        """计算指定会话的排队位置（三段排序）。

        排序逻辑：
        1. VIP段排最前
        2. 已梳理(info_locked=true)段排第二
        3. 待梳理(info_locked=false)段排最后
        4. 同段内：queue_priority DESC → urgency_score DESC → created_at ASC

        Args:
            db: 数据库会话
            conversation: 要计算位置的会话

        Returns:
            Dict: {position, segment, ahead_count, estimated_wait_sec}
        """
        segment = self._determine_segment(conversation)
        ahead_count = 0

        # ---- 计算更高段的人数 ----
        if segment != "vip":
            # 当前不是VIP段 → 所有VIP都排前面
            vip_count = await db.scalar(
                select(func.count(Conversation.id)).where(
                    Conversation.status == "queued",
                    Conversation.is_vip == True,  # noqa: E712
                )
            )
            ahead_count += vip_count or 0

        if segment == "incomplete":
            # 当前是待梳理段 → 已梳理段也排前面
            completed_count = await db.scalar(
                select(func.count(Conversation.id)).where(
                    Conversation.status == "queued",
                    Conversation.is_vip == False,  # noqa: E712
                    Conversation.info_locked == True,  # noqa: E712
                )
            )
            ahead_count += completed_count or 0

        # ---- 计算同段内排在前面的人数 ----
        same_segment_ahead = await self._count_same_segment_ahead(db, conversation, segment)
        ahead_count += same_segment_ahead

        position = ahead_count + 1
        estimated_wait = position * ESTIMATED_SERVICE_TIME_SEC

        # 中文段位名称（前端展示用）
        segment_labels = {
            "vip": "VIP优先",
            "completed": "已梳理",
            "incomplete": "待梳理",
        }

        return {
            "position": position,
            "segment": segment,
            "segment_label": segment_labels.get(segment, segment),
            "ahead_count": ahead_count,
            "estimated_wait_sec": estimated_wait,
            "estimated_wait_text": self._format_wait_time(estimated_wait),
            "queue_priority": conversation.queue_priority,
        }

    async def _count_same_segment_ahead(
        self, db: AsyncSession, conversation: Conversation, segment: str
    ) -> int:
        """计算同段内排在当前会话前面的排队人数。

        段内排序规则：queue_priority DESC → urgency_score DESC → created_at ASC

        Args:
            db: 数据库会话
            conversation: 当前会话
            segment: 当前段位

        Returns:
            int: 同段内排在前面的人数
        """
        # 构建同段条件
        conditions = [
            Conversation.status == "queued",
            Conversation.id != conversation.id,  # 排除自己
        ]

        if segment == "vip":
            conditions.append(Conversation.is_vip == True)  # noqa: E712
        elif segment == "completed":
            conditions.append(Conversation.is_vip == False)  # noqa: E712
            conditions.append(Conversation.info_locked == True)  # noqa: E712
        else:  # incomplete
            conditions.append(Conversation.is_vip == False)  # noqa: E712
            conditions.append(Conversation.info_locked == False)  # noqa: E712

        # 同段内排在前面的条件：
        # 1. queue_priority 更高
        # 2. 或 queue_priority 相同且 urgency_score 更高
        # 3. 或 queue_priority 和 urgency_score 都相同且 created_at 更早
        ahead_conditions = or_(
            Conversation.queue_priority > conversation.queue_priority,
            and_(
                Conversation.queue_priority == conversation.queue_priority,
                Conversation.urgency_score > conversation.urgency_score,
            ),
            and_(
                Conversation.queue_priority == conversation.queue_priority,
                Conversation.urgency_score == conversation.urgency_score,
                Conversation.created_at < conversation.created_at,
            ),
        )

        count = await db.scalar(
            select(func.count(Conversation.id)).where(
                *conditions, ahead_conditions
            )
        )
        return count or 0

    # ======================================================================
    # 平台统计
    # ======================================================================

    async def get_platform_stats(self, db: AsyncSession) -> Dict[str, int]:
        """获取平台统计数据（决策 C5）。

        total_active = ai_handling + queued + serving
        queued = 排队中人数
        serving = 服务中人数

        Args:
            db: 数据库会话

        Returns:
            Dict: {total_active, queued, serving, ai_handling}
        """
        # 总活跃 = ai_handling + queued + serving
        total_active = await db.scalar(
            select(func.count(Conversation.id)).where(
                Conversation.status.in_(["ai_handling", "queued", "serving"])
            )
        )

        queued = await db.scalar(
            select(func.count(Conversation.id)).where(
                Conversation.status == "queued"
            )
        )

        serving = await db.scalar(
            select(func.count(Conversation.id)).where(
                Conversation.status == "serving"
            )
        )

        ai_handling = await db.scalar(
            select(func.count(Conversation.id)).where(
                Conversation.status == "ai_handling"
            )
        )

        return {
            "total_active": total_active or 0,
            "queued": queued or 0,
            "serving": serving or 0,
            "ai_handling": ai_handling or 0,
        }

    async def get_queue_segment_stats(self, db: AsyncSession) -> Dict[str, int]:
        """获取排队分段统计（坐席端看板用）。

        Returns:
            Dict: {vip_count, completed_count, incomplete_count, total_queued}
        """
        # VIP段
        vip_count = await db.scalar(
            select(func.count(Conversation.id)).where(
                Conversation.status == "queued",
                Conversation.is_vip == True,  # noqa: E712
            )
        )

        # 已梳理段
        completed_count = await db.scalar(
            select(func.count(Conversation.id)).where(
                Conversation.status == "queued",
                Conversation.is_vip == False,  # noqa: E712
                Conversation.info_locked == True,  # noqa: E712
            )
        )

        # 待梳理段
        incomplete_count = await db.scalar(
            select(func.count(Conversation.id)).where(
                Conversation.status == "queued",
                Conversation.is_vip == False,  # noqa: E712
                Conversation.info_locked == False,  # noqa: E712
            )
        )

        total_queued = (vip_count or 0) + (completed_count or 0) + (incomplete_count or 0)

        return {
            "vip_count": vip_count or 0,
            "completed_count": completed_count or 0,
            "incomplete_count": incomplete_count or 0,
            "total_queued": total_queued,
        }

    # ======================================================================
    # 综合排队状态（H5端 queue/status API）
    # ======================================================================

    async def get_comprehensive_status(
        self, db: AsyncSession, conversation: Conversation
    ) -> Dict[str, Any]:
        """获取综合排队状态：排队位置+段位+平台统计+答题状态+积分。

        供 GET /api/h5/queue/status API调用。

        Args:
            db: 数据库会话
            conversation: 当前会话

        Returns:
            Dict: 综合状态数据
        """
        # 1. 排队位置（仅排队中时计算）
        if conversation.status == "queued":
            queue_info = await self.calculate_queue_position(db, conversation)
        else:
            queue_info = {
                "position": 0,
                "segment": self._determine_segment(conversation),
                "segment_label": "非排队中",
                "ahead_count": 0,
                "estimated_wait_sec": 0,
                "estimated_wait_text": "—",
                "queue_priority": conversation.queue_priority,
            }

        # 2. 平台统计
        platform_stats = await self.get_platform_stats(db)

        # 3. 积分信息
        points_info = await self._get_employee_points(db, conversation.employee_id)

        # 4. 插队信息
        quiz_answered = conversation.queue_priority * 3 if conversation.queue_priority > 0 else 0
        max_quiz_for_jump = 6  # 2位×3题=6题
        remaining_for_next_jump = 3 - (quiz_answered % 3) if quiz_answered < max_quiz_for_jump else 0

        return {
            "conversation_status": conversation.status,
            "queue": queue_info,
            "platform": platform_stats,
            "points": points_info,
            "quiz": {
                "answered_in_session": quiz_answered,
                "queue_priority": conversation.queue_priority,
                "max_priority": 2,
                "remaining_for_next_jump": remaining_for_next_jump,
                "can_jump_more": conversation.queue_priority < 2,
            },
            "info_locked": conversation.info_locked,
        }

    # ======================================================================
    # 坐席端排队看板
    # ======================================================================

    async def get_agent_dashboard(self, db: AsyncSession) -> Dict[str, Any]:
        """获取坐席端排队看板数据。

        Returns:
            Dict: {segment_stats, platform_stats, queue_list}
        """
        segment_stats = await self.get_queue_segment_stats(db)
        platform_stats = await self.get_platform_stats(db)

        # 获取排队列表（按三段排序）
        queue_list = await self._get_sorted_queue_list(db, limit=50)

        return {
            "segments": segment_stats,
            "platform": platform_stats,
            "queue_list": queue_list,
        }

    async def _get_sorted_queue_list(
        self, db: AsyncSession, limit: int = 50
    ) -> List[Dict[str, Any]]:
        """获取按三段排序的排队列表。

        Returns:
            List[Dict]: 排队会话列表
        """
        # 查询所有排队中的会话，按段位+段内排序
        # 段位排序：VIP(0) > 已梳理(1) > 待梳理(2)
        segment_order = case(
            (Conversation.is_vip == True, 0),  # noqa: E712
            (Conversation.info_locked == True, 1),  # noqa: E712
            else_=2,
        )

        stmt = (
            select(Conversation)
            .where(Conversation.status == "queued")
            .order_by(
                segment_order,
                Conversation.queue_priority.desc(),
                Conversation.urgency_score.desc(),
                Conversation.created_at.asc(),
            )
            .limit(limit)
        )

        result = await db.execute(stmt)
        conversations = result.scalars().all()

        # 转为前端需要的列表格式
        queue_list = []
        for conv in conversations:
            segment = self._determine_segment(conv)
            queue_list.append({
                "conversation_id": conv.id,
                "employee_name": conv.employee_name,
                "department": conv.department,
                "employee_id": conv.employee_id,
                "segment": segment,
                "segment_label": {
                    "vip": "VIP优先",
                    "completed": "已梳理",
                    "incomplete": "待梳理",
                }.get(segment, segment),
                "urgency_score": conv.urgency_score,
                "queue_priority": conv.queue_priority,
                "info_locked": conv.info_locked,
                "is_vip": conv.is_vip,
                "last_message_summary": conv.last_message_summary,
                "created_at": conv.created_at.isoformat() if conv.created_at else None,
                "waiting_seconds": int(
                    (datetime.now(timezone.utc) - conv.created_at).total_seconds()
                ) if conv.created_at else 0,
            })

        return queue_list

    # ======================================================================
    # 辅助方法
    # ======================================================================

    async def _get_employee_points(
        self, db: AsyncSession, employee_id: str
    ) -> Dict[str, Any]:
        """获取员工积分信息。

        Args:
            db: 数据库会话
            employee_id: 员工ID

        Returns:
            Dict: {total_points, level, answered_count, correct_count}
        """
        result = await db.execute(
            select(EmployeePoints).where(EmployeePoints.employee_id == employee_id)
        )
        points = result.scalar_one_or_none()

        if points:
            return {
                "total_points": points.total_points,
                "level": points.level,
                "answered_count": points.answered_count,
                "correct_count": points.correct_count,
            }
        else:
            return {
                "total_points": 0,
                "level": "IT小白",
                "answered_count": 0,
                "correct_count": 0,
            }

    @staticmethod
    def _format_wait_time(seconds: int) -> str:
        """将秒数格式化为人类可读的等待时间文本。

        Args:
            seconds: 秒数

        Returns:
            str: 如"约5分钟"、"约1小时30分钟"
        """
        if seconds <= 0:
            return "即将接通"
        minutes = seconds // 60
        if minutes < 1:
            return f"约{seconds}秒"
        elif minutes < 60:
            return f"约{minutes}分钟"
        else:
            hours = minutes // 60
            remaining_minutes = minutes % 60
            if remaining_minutes == 0:
                return f"约{hours}小时"
            return f"约{hours}小时{remaining_minutes}分钟"


# 单例
_queue_service: Optional[QueueService] = None


def get_queue_service() -> QueueService:
    """获取 QueueService 单例。"""
    global _queue_service
    if _queue_service is None:
        _queue_service = QueueService()
    return _queue_service