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

from app.models import ChoreHistory, FinancialAuditLog, Item, UserGroup, User
from app.schemas.activity import Activity, ActivityEventType, ActivityUser

async def get_group_activity(db: AsyncSession, group_id: int, limit: int, cursor: int = None) -> list[Activity]:
    
    queries = []

    chore_history_stmt = (
        select(ChoreHistory)
        .where(ChoreHistory.group_id == group_id)
        .options(selectinload(ChoreHistory.changed_by_user))
    )
    if cursor:
        chore_history_stmt = chore_history_stmt.where(ChoreHistory.timestamp < datetime.fromtimestamp(cursor))
    queries.append(chore_history_stmt)
    
    # FinancialAuditLog has group_id through joins, which is complex. For now, we assume a direct or easy link.
    # This might need refinement based on actual relationships.
    # This is a placeholder as FinancialAuditLog doesn't have a direct group_id.
    # We will need to join through expenses/settlements, etc.
    # For now, this part will return empty.

    items_stmt = (
        select(Item)
        .join(Item.list)
        .where(text("lists.group_id = :group_id"))
        .params(group_id=group_id)
        .options(selectinload(Item.added_by_user), selectinload(Item.completed_by_user))
    )
    if cursor:
        items_stmt = items_stmt.where(Item.created_at < datetime.fromtimestamp(cursor))
    queries.append(items_stmt)
    
    results = []
    for q in queries:
        res = await db.execute(q)
        results.extend(res.scalars().all())

    activities = []
    for item in results:
        if isinstance(item, ChoreHistory):
            if item.event_type.value == 'completed':
                user = item.changed_by_user
                activities.append(Activity(
                    id=f"chore_history-{item.id}",
                    event_type=ActivityEventType.CHORE_COMPLETED,
                    timestamp=item.timestamp,
                    user=ActivityUser(id=user.id, name=user.name),
                    details={"chore_name": item.event_data.get("name", "Unknown chore")},
                    message=f"{user.name or 'User'} completed '{item.event_data.get('name', 'a chore')}'."
                ))
        elif isinstance(item, Item):
             user = item.added_by_user
             activities.append(Activity(
                 id=f"item-added-{item.id}",
                 event_type=ActivityEventType.ITEM_ADDED,
                 timestamp=item.created_at,
                 user=ActivityUser(id=user.id, name=user.name),
                 details={"item_name": item.name, "list_id": item.list_id},
                 message=f"{user.name or 'User'} added '{item.name}' to a list."
             ))
             if item.is_complete and item.completed_by_user:
                 c_user = item.completed_by_user
                 activities.append(Activity(
                     id=f"item-completed-{item.id}",
                     event_type=ActivityEventType.ITEM_COMPLETED,
                     timestamp=item.updated_at, # This is an approximation
                     user=ActivityUser(id=c_user.id, name=c_user.name),
                     details={"item_name": item.name, "list_id": item.list_id},
                     message=f"{c_user.name or 'User'} purchased '{item.name}'."
                 ))

    activities.sort(key=lambda x: x.timestamp, reverse=True)
    
    return activities[:limit]