homeschool/backend/app/routers/sessions.py

from datetime import date

from fastapi import APIRouter, Depends, HTTPException, status
from sqlalchemy.ext.asyncio import AsyncSession
from sqlalchemy import select
from sqlalchemy.orm import selectinload

from app.dependencies import get_db, get_current_user
from app.models.child import Child
from app.models.schedule import ScheduleBlock, ScheduleTemplate
from app.models.subject import Subject  # noqa: F401 — needed for selectinload chain
from app.models.session import DailySession, TimerEvent
from app.models.user import User
from app.schemas.session import DailySessionOut, SessionStart, TimerAction
from app.websocket.manager import manager

router = APIRouter(prefix="/api/sessions", tags=["sessions"])


async def _broadcast_session(db: AsyncSession, session: DailySession) -> None:
    """Build a snapshot dict and broadcast it to all connected TVs for this child."""
    blocks = []
    day_start_time = None
    day_end_time = None

    if session.template_id:
        blocks_result = await db.execute(
            select(ScheduleBlock)
            .where(ScheduleBlock.template_id == session.template_id)
            .options(selectinload(ScheduleBlock.subject).selectinload(Subject.options))
            .order_by(ScheduleBlock.time_start)
        )
        blocks = [
            {
                "id": b.id,
                "subject_id": b.subject_id,
                "subject": {
                    "id": b.subject.id,
                    "name": b.subject.name,
                    "color": b.subject.color,
                    "icon": b.subject.icon,
                    "options": [{"id": o.id, "text": o.text, "order_index": o.order_index}
                                for o in b.subject.options],
                } if b.subject else None,
                "time_start": str(b.time_start),
                "time_end": str(b.time_end),
                "duration_minutes": b.duration_minutes,
                "label": b.label,
                "order_index": b.order_index,
            }
            for b in blocks_result.scalars().all()
        ]

        template_result = await db.execute(
            select(ScheduleTemplate).where(ScheduleTemplate.id == session.template_id)
        )
        template = template_result.scalar_one_or_none()
        if template:
            day_start_time = str(template.day_start_time) if template.day_start_time else None
            day_end_time = str(template.day_end_time) if template.day_end_time else None

    # Gather completed block IDs from timer events
    events_result = await db.execute(
        select(TimerEvent).where(
            TimerEvent.session_id == session.id,
            TimerEvent.event_type == "complete",
        )
    )
    completed_ids = [e.block_id for e in events_result.scalars().all() if e.block_id]

    payload = {
        "event": "session_update",
        "session": {
            "id": session.id,
            "child_id": session.child_id,
            "session_date": str(session.session_date),
            "is_active": session.is_active,
            "current_block_id": session.current_block_id,
        },
        "blocks": blocks,
        "completed_block_ids": completed_ids,
        "day_start_time": day_start_time,
        "day_end_time": day_end_time,
    }
    await manager.broadcast(session.child_id, payload)


@router.post("", response_model=DailySessionOut, status_code=status.HTTP_201_CREATED)
async def start_session(
    body: SessionStart,
    current_user: User = Depends(get_current_user),
    db: AsyncSession = Depends(get_db),
):
    # Verify child belongs to user
    child_result = await db.execute(
        select(Child).where(Child.id == body.child_id, Child.user_id == current_user.id)
    )
    child = child_result.scalar_one_or_none()
    if not child:
        raise HTTPException(status_code=404, detail="Child not found")

    # Reset strikes at the start of each new day
    if child.strikes != 0:
        child.strikes = 0
        await manager.broadcast(body.child_id, {"event": "strikes_update", "strikes": 0})

    session_date = body.session_date or date.today()

    # Deactivate any existing active session for this child today
    existing = await db.execute(
        select(DailySession).where(
            DailySession.child_id == body.child_id,
            DailySession.session_date == session_date,
            DailySession.is_active == True,
        )
    )
    for old in existing.scalars().all():
        old.is_active = False

    session = DailySession(
        child_id=body.child_id,
        template_id=body.template_id,
        session_date=session_date,
        is_active=True,
    )
    db.add(session)
    await db.commit()
    await db.refresh(session)

    # Record session start as a timer event so it appears in the activity log
    db.add(TimerEvent(session_id=session.id, block_id=None, event_type="session_start"))
    await db.commit()

    await _broadcast_session(db, session)
    return session


@router.get("/{session_id}", response_model=DailySessionOut)
async def get_session(
    session_id: int,
    current_user: User = Depends(get_current_user),
    db: AsyncSession = Depends(get_db),
):
    result = await db.execute(
        select(DailySession)
        .join(Child)
        .where(DailySession.id == session_id, Child.user_id == current_user.id)
        .options(selectinload(DailySession.current_block))
    )
    session = result.scalar_one_or_none()
    if not session:
        raise HTTPException(status_code=404, detail="Session not found")
    return session


@router.post("/{session_id}/timer", response_model=DailySessionOut)
async def timer_action(
    session_id: int,
    body: TimerAction,
    current_user: User = Depends(get_current_user),
    db: AsyncSession = Depends(get_db),
):
    result = await db.execute(
        select(DailySession)
        .join(Child)
        .where(DailySession.id == session_id, Child.user_id == current_user.id)
        .options(selectinload(DailySession.current_block))
    )
    session = result.scalar_one_or_none()
    if not session:
        raise HTTPException(status_code=404, detail="Session not found")

    # When starting a different block, implicitly pause the previous one so
    # the activity log stays accurate and elapsed time is preserved correctly.
    if body.event_type == "start" and body.block_id is not None:
        prev_block_id = session.current_block_id
        if prev_block_id and prev_block_id != body.block_id:
            db.add(TimerEvent(
                session_id=session.id,
                block_id=prev_block_id,
                event_type="pause",
            ))

    # Update current block if provided
    if body.block_id is not None:
        session.current_block_id = body.block_id

    # Record the timer event
    event = TimerEvent(
        session_id=session.id,
        block_id=body.block_id or session.current_block_id,
        event_type=body.event_type,
    )
    db.add(event)

    # Mark session complete if event is session-level complete
    if body.event_type == "complete" and body.block_id is None:
        session.is_active = False

    await db.commit()
    await db.refresh(session)

    # For 'start' events, compute elapsed from previous intervals so every
    # client (including TV) can restore the correct offset without a cache.
    block_elapsed_seconds = 0
    if body.event_type == "start" and event.block_id:
        tick_result = await db.execute(
            select(TimerEvent)
            .where(
                TimerEvent.session_id == session.id,
                TimerEvent.block_id == event.block_id,
                TimerEvent.event_type.in_(["start", "resume", "pause"]),
                TimerEvent.id != event.id,
            )
            .order_by(TimerEvent.occurred_at)
        )
        tick_events = tick_result.scalars().all()
        last_start_time = None
        for e in tick_events:
            if e.event_type in ("start", "resume"):
                last_start_time = e.occurred_at
            elif e.event_type == "pause" and last_start_time:
                block_elapsed_seconds += int((e.occurred_at - last_start_time).total_seconds())
                last_start_time = None

    # Broadcast the timer event to all TV clients
    ws_payload = {
        "event": body.event_type,
        "session_id": session.id,
        "block_id": event.block_id,
        "current_block_id": session.current_block_id,
        "is_active": session.is_active,
        "block_elapsed_seconds": block_elapsed_seconds,
    }
    await manager.broadcast(session.child_id, ws_payload)

    return session