import asyncio
import logging

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

from app.db.models import ClassMembership, Notification, User
from app.services.email_service import send_class_notification_email

logger = logging.getLogger(__name__)


EMAIL_VISUALS: dict[str, dict[str, str | None]] = {
    "announcement": {
        "eyebrow": "Announcement",
        "action_label": "查看公告",
        "summary_prefix": "公告摘要",
    },
    "timeline": {
        "eyebrow": "Class Feed",
        "action_label": "查看动态",
        "summary_prefix": "动态摘要",
    },
    "vote": {
        "eyebrow": "Voting Open",
        "action_label": "立即投票",
        "summary_prefix": "投票说明",
    },
    "schedule": {
        "eyebrow": "Schedule Update",
        "action_label": "查看排期",
        "summary_prefix": "时间信息",
    },
    "assignment": {
        "eyebrow": "Assignment Posted",
        "action_label": "查看作业",
        "summary_prefix": "作业说明",
    },
    "resource": {
        "eyebrow": "Resource Added",
        "action_label": "查看资源",
        "summary_prefix": "资源说明",
    },
    "fund": {
        "eyebrow": "Fund Update",
        "action_label": "查看班费",
        "summary_prefix": "账务说明",
    },
}


def _build_email_meta(type_: str, email_body: str | None) -> tuple[str, str | None, str | None]:
    visual = EMAIL_VISUALS.get(type_, {})
    eyebrow = str(visual.get("eyebrow") or "Class Update")
    action_label = visual.get("action_label")
    summary_prefix = visual.get("summary_prefix")

    if not email_body:
        return eyebrow, action_label, None

    summary_html = email_body
    if summary_prefix:
        summary_html = f"<strong>{summary_prefix}：</strong>{email_body}"
    return eyebrow, action_label, summary_html


async def create_notification(
    db: AsyncSession,
    user_id: int,
    type: str,
    title: str,
    content: str | None = None,
    related_id: int | None = None,
) -> Notification:
    notification = Notification(
        user_id=user_id,
        type=type,
        title=title,
        content=content,
        related_id=related_id,
    )
    db.add(notification)
    await db.commit()
    await db.refresh(notification)
    return notification


async def create_notifications_for_class(
    db: AsyncSession,
    class_id: int,
    type: str,
    title: str,
    content: str | None = None,
    related_id: int | None = None,
    exclude_user_id: int | None = None,
    email_subject: str | None = None,
    email_body: str | None = None,
    email_action_path: str | None = None,
):
    """Create in-app notifications + send email for all active users in a class."""
    result = await db.execute(
        select(User.id, User.email)
        .join(ClassMembership, ClassMembership.user_id == User.id)
        .where(
            ClassMembership.class_id == class_id,
            User.status == "approved",
        )
    )
    rows = result.all()

    emails: list[str] = []
    for uid, email in rows:
        notification = Notification(
            user_id=uid,
            type=type,
            title=title,
            content=content,
            related_id=related_id,
        )
        db.add(notification)
        emails.append(email)

    await db.commit()

    # Send email notification in background (fire-and-forget)
    if email_subject and emails:
        from app.config import settings
        action_url = f"{settings.frontend_url}{email_action_path}" if email_action_path else None
        eyebrow, action_label, summary_html = _build_email_meta(type, email_body or content or "")
        asyncio.create_task(
            _safe_send_emails(
                emails,
                email_subject,
                title,
                email_body or content or "",
                action_url,
                eyebrow,
                action_label,
                summary_html,
            )
        )


async def _safe_send_emails(
    emails: list[str],
    subject: str,
    title: str,
    body: str,
    action_url: str | None,
    eyebrow: str,
    action_label: str | None,
    summary_html: str | None,
):
    """Fire-and-forget email sending with error logging."""
    try:
        await send_class_notification_email(
            emails,
            subject,
            title,
            body,
            action_url,
            eyebrow=eyebrow,
            action_label=action_label,
            summary_html=summary_html,
        )
    except Exception as e:
        logger.error(f"Failed to send class notification emails: {e}")


async def list_notifications(
    db: AsyncSession, user_id: int, page: int = 1, page_size: int = 20
) -> tuple[list[Notification], int]:
    total_result = await db.execute(
        select(func.count(Notification.id)).where(Notification.user_id == user_id)
    )
    total = total_result.scalar() or 0

    result = await db.execute(
        select(Notification)
        .where(Notification.user_id == user_id)
        .order_by(Notification.created_at.desc())
        .offset((page - 1) * page_size)
        .limit(page_size)
    )
    notifications = list(result.scalars().all())
    return notifications, total


async def get_unread_count(db: AsyncSession, user_id: int) -> int:
    result = await db.execute(
        select(func.count(Notification.id)).where(
            Notification.user_id == user_id,
            Notification.is_read == False,
        )
    )
    return result.scalar() or 0


async def mark_as_read(db: AsyncSession, notification_id: int, user_id: int) -> bool:
    result = await db.execute(
        update(Notification)
        .where(Notification.id == notification_id, Notification.user_id == user_id)
        .values(is_read=True)
    )
    await db.commit()
    return result.rowcount > 0


async def mark_all_as_read(db: AsyncSession, user_id: int) -> int:
    result = await db.execute(
        update(Notification)
        .where(Notification.user_id == user_id, Notification.is_read == False)
        .values(is_read=True)
    )
    await db.commit()
    return result.rowcount