import json
from datetime import datetime

from sqlalchemy import select, func
from sqlalchemy.ext.asyncio import AsyncSession
from sqlalchemy.orm import selectinload

from app.db.models import Timeline, User
from app.schemas.timeline import TimelineCreate, TimelineUpdate
from app.services.notification_service import create_notifications_for_class


async def create_timeline(
    db: AsyncSession, class_id: int, author_id: int, data: TimelineCreate
) -> Timeline:
    post = Timeline(
        class_id=class_id,
        author_id=author_id,
        title=data.title,
        content=data.content,
    )
    db.add(post)
    await db.commit()
    await db.refresh(post)

    # Send notifications + email to class members
    content_preview = (data.content[:100] + "...") if data.content and len(data.content) > 100 else (data.content or "")
    await create_notifications_for_class(
        db, class_id, "timeline", f"新大事件: {data.title}",
        content=content_preview,
        related_id=post.id,
        email_subject=f"HKU ICB - 新大事件: {data.title}",
        email_body=f"<p>{content_preview}</p>" if content_preview else None,
        email_action_path="/timeline",
    )

    return post


async def update_timeline(
    db: AsyncSession, post: Timeline, data: TimelineUpdate
) -> Timeline:
    for field, value in data.model_dump(exclude_unset=True).items():
        setattr(post, field, value)
    await db.commit()
    await db.refresh(post)
    return post


async def delete_timeline(db: AsyncSession, post: Timeline):
    await db.delete(post)
    await db.commit()


async def get_timeline_by_id(db: AsyncSession, post_id: int) -> Timeline | None:
    result = await db.execute(select(Timeline).where(Timeline.id == post_id))
    return result.scalar_one_or_none()


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

    result = await db.execute(
        select(Timeline)
        .options(selectinload(Timeline.author))
        .where(Timeline.class_id == class_id)
        .order_by(Timeline.created_at.desc())
        .offset((page - 1) * page_size)
        .limit(page_size)
    )
    posts = list(result.scalars().all())
    return posts, total


async def add_images_to_timeline(db: AsyncSession, post: Timeline, urls: list[str]):
    existing = post.get_image_urls_list()
    existing.extend(urls)
    post.set_image_urls_list(existing)
    await db.commit()
    await db.refresh(post)