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.morning_routine import MorningRoutineItem
from app.models.break_activity import BreakActivityItem
from app.models.schedule import ScheduleBlock
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.utils.timer import compute_block_elapsed, compute_break_elapsed
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 = []

    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,
                "break_time_enabled": b.break_time_enabled,
                "break_time_minutes": b.break_time_minutes,
            }
            for b in blocks_result.scalars().all()
        ]

    # 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]

    # Fetch morning routine items via child → user_id
    child_result = await db.execute(select(Child).where(Child.id == session.child_id))
    child = child_result.scalar_one_or_none()
    morning_routine: list[str] = []
    if child:
        routine_result = await db.execute(
            select(MorningRoutineItem)
            .where(MorningRoutineItem.user_id == child.user_id)
            .order_by(MorningRoutineItem.order_index, MorningRoutineItem.id)
        )
        morning_routine = [item.text for item in routine_result.scalars().all()]

    break_activities: list[str] = []
    if child:
        break_result = await db.execute(
            select(BreakActivityItem)
            .where(BreakActivityItem.user_id == child.user_id)
            .order_by(BreakActivityItem.order_index, BreakActivityItem.id)
        )
        break_activities = [item.text for item in break_result.scalars().all()]

    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,
        "morning_routine": morning_routine,
        "break_activities": break_activities,
    }
    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).selectinload(ScheduleBlock.subject))
    )
    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).selectinload(ScheduleBlock.subject))
    )
    session = result.scalar_one_or_none()
    if not session:
        raise HTTPException(status_code=404, detail="Session not found")

    # Break-time events are handled separately — they don't switch blocks or
    # trigger implicit pauses.  Just record the event and broadcast.
    BREAK_EVENTS = {"break_start", "break_pause", "break_resume", "break_reset"}
    if body.event_type in BREAK_EVENTS:
        block_id = body.block_id or session.current_block_id

        # When break starts, implicitly pause the main block timer so elapsed
        # time is captured accurately in the activity log and on page reload.
        if body.event_type == "break_start" and block_id:
            db.add(TimerEvent(
                session_id=session.id,
                block_id=block_id,
                event_type="pause",
            ))

        db.add(TimerEvent(
            session_id=session.id,
            block_id=block_id,
            event_type=body.event_type,
        ))
        await db.commit()
        await db.refresh(session)

        break_elapsed_seconds = 0
        block_elapsed_seconds = 0
        if body.event_type in ("break_start", "break_reset") and block_id:
            break_elapsed_seconds, _ = await compute_break_elapsed(db, session.id, block_id)
        if body.event_type == "break_start" and block_id:
            block_elapsed_seconds, _ = await compute_block_elapsed(db, session.id, block_id)

        ws_payload = {
            "event": body.event_type,
            "session_id": session.id,
            "block_id": block_id,
            "current_block_id": session.current_block_id,
            "is_active": session.is_active,
            "break_elapsed_seconds": break_elapsed_seconds,
            "block_elapsed_seconds": block_elapsed_seconds,
        }
        await manager.broadcast(session.child_id, ws_payload)
        return session

    # When switching to a different block (start / select / reset), implicitly
    # pause the previous block so the activity log stays accurate.
    prev_block_id = None
    prev_block_elapsed_seconds = 0
    if body.event_type in ("start", "select", "reset") 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",
            ))
            # Autoflush means the implicit pause above is visible to the helper.
            prev_block_elapsed_seconds, _ = await compute_block_elapsed(
                db, session.id, prev_block_id
            )

    # 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 / select / reset, compute elapsed for the new block so every
    # client can restore the correct offset without a local cache.
    block_elapsed_seconds = 0
    if body.event_type in ("start", "select", "reset") and event.block_id:
        block_elapsed_seconds, _ = await compute_block_elapsed(
            db, session.id, event.block_id
        )

    # 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,
        "is_paused": body.event_type == "select",
        "block_elapsed_seconds": block_elapsed_seconds,
        "prev_block_id": prev_block_id,
        "prev_block_elapsed_seconds": prev_block_elapsed_seconds,
    }
    await manager.broadcast(session.child_id, ws_payload)

    return session