from __future__ import annotations

from typing import Optional

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

from models.ghost_content import Post, PostLike


async def toggle_post_like(
    session: AsyncSession,
    user_id: int,
    post_id: int,
) -> tuple[bool, Optional[str]]:
    """
    Toggle a post like for a given user using soft deletes.
    Returns (liked_state, error_message).
    - If error_message is not None, an error occurred.
    - liked_state indicates whether post is now liked (True) or unliked (False).
    """

    # Verify post exists
    post_exists = await session.scalar(
        select(Post.id).where(Post.id == post_id, Post.deleted_at.is_(None))
    )
    if not post_exists:
        return False, "Post not found"

    # Check if like exists (not deleted)
    existing = await session.scalar(
        select(PostLike).where(
            PostLike.user_id == user_id,
            PostLike.post_id == post_id,
            PostLike.deleted_at.is_(None),
        )
    )

    if existing:
        # Unlike: soft delete the like
        await session.execute(
            update(PostLike)
            .where(
                PostLike.user_id == user_id,
                PostLike.post_id == post_id,
                PostLike.deleted_at.is_(None),
            )
            .values(deleted_at=func.now())
        )
        return False, None
    else:
        # Like: add a new like
        new_like = PostLike(
            user_id=user_id,
            post_id=post_id,
        )
        session.add(new_like)
        return True, None