"""Availability routes for admin to manage booking availability."""
from datetime import date, timedelta

from fastapi import APIRouter, Depends, HTTPException, Query
from sqlalchemy import select, delete, and_
from sqlalchemy.ext.asyncio import AsyncSession

from auth import require_permission
from database import get_db
from models import User, Availability, Permission
from schemas import (
    TimeSlot,
    AvailabilityDay,
    AvailabilityResponse,
    SetAvailabilityRequest,
    CopyAvailabilityRequest,
)
from shared_constants import MAX_ADVANCE_DAYS


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


def _get_date_range_bounds() -> tuple[date, date]:
    """Get the valid date range for availability (tomorrow to +30 days)."""
    today = date.today()
    min_date = today + timedelta(days=1)  # Tomorrow
    max_date = today + timedelta(days=MAX_ADVANCE_DAYS)
    return min_date, max_date


def _validate_date_in_range(d: date, min_date: date, max_date: date) -> None:
    """Validate a date is within the allowed range."""
    if d < min_date:
        raise HTTPException(
            status_code=400,
            detail=f"Cannot set availability for past dates. Earliest allowed: {min_date}",
        )
    if d > max_date:
        raise HTTPException(
            status_code=400,
            detail=f"Cannot set availability more than {MAX_ADVANCE_DAYS} days ahead. Latest allowed: {max_date}",
        )


@router.get("", response_model=AvailabilityResponse)
async def get_availability(
    from_date: date = Query(..., alias="from", description="Start date (inclusive)"),
    to_date: date = Query(..., alias="to", description="End date (inclusive)"),
    db: AsyncSession = Depends(get_db),
    _current_user: User = Depends(require_permission(Permission.MANAGE_AVAILABILITY)),
) -> AvailabilityResponse:
    """Get availability slots for a date range."""
    if from_date > to_date:
        raise HTTPException(
            status_code=400,
            detail="'from' date must be before or equal to 'to' date",
        )
    
    # Query availability in range
    result = await db.execute(
        select(Availability)
        .where(and_(Availability.date >= from_date, Availability.date <= to_date))
        .order_by(Availability.date, Availability.start_time)
    )
    slots = result.scalars().all()
    
    # Group by date
    days_dict: dict[date, list[TimeSlot]] = {}
    for slot in slots:
        if slot.date not in days_dict:
            days_dict[slot.date] = []
        days_dict[slot.date].append(TimeSlot(
            start_time=slot.start_time,
            end_time=slot.end_time,
        ))
    
    # Convert to response format
    days = [
        AvailabilityDay(date=d, slots=days_dict[d])
        for d in sorted(days_dict.keys())
    ]
    
    return AvailabilityResponse(days=days)


@router.put("", response_model=AvailabilityDay)
async def set_availability(
    request: SetAvailabilityRequest,
    db: AsyncSession = Depends(get_db),
    _current_user: User = Depends(require_permission(Permission.MANAGE_AVAILABILITY)),
) -> AvailabilityDay:
    """Set availability for a specific date. Replaces any existing availability."""
    min_date, max_date = _get_date_range_bounds()
    _validate_date_in_range(request.date, min_date, max_date)
    
    # Validate slots don't overlap
    sorted_slots = sorted(request.slots, key=lambda s: s.start_time)
    for i in range(len(sorted_slots) - 1):
        if sorted_slots[i].end_time > sorted_slots[i + 1].start_time:
            raise HTTPException(
                status_code=400,
                detail=f"Time slots overlap: {sorted_slots[i].end_time} > {sorted_slots[i + 1].start_time}",
            )
    
    # Validate each slot's end_time > start_time
    for slot in request.slots:
        if slot.end_time <= slot.start_time:
            raise HTTPException(
                status_code=400,
                detail=f"Slot end time must be after start time: {slot.start_time} - {slot.end_time}",
            )
    
    # Delete existing availability for this date
    await db.execute(
        delete(Availability).where(Availability.date == request.date)
    )
    
    # Create new availability slots
    for slot in request.slots:
        availability = Availability(
            date=request.date,
            start_time=slot.start_time,
            end_time=slot.end_time,
        )
        db.add(availability)
    
    await db.commit()
    
    return AvailabilityDay(date=request.date, slots=request.slots)


@router.post("/copy", response_model=AvailabilityResponse)
async def copy_availability(
    request: CopyAvailabilityRequest,
    db: AsyncSession = Depends(get_db),
    _current_user: User = Depends(require_permission(Permission.MANAGE_AVAILABILITY)),
) -> AvailabilityResponse:
    """Copy availability from one day to multiple target days."""
    min_date, max_date = _get_date_range_bounds()
    
    # Validate source date is in range (for consistency, though DB query would fail anyway)
    _validate_date_in_range(request.source_date, min_date, max_date)
    
    # Validate target dates
    for target_date in request.target_dates:
        _validate_date_in_range(target_date, min_date, max_date)
    
    # Get source availability
    result = await db.execute(
        select(Availability)
        .where(Availability.date == request.source_date)
        .order_by(Availability.start_time)
    )
    source_slots = result.scalars().all()
    
    if not source_slots:
        raise HTTPException(
            status_code=400,
            detail=f"No availability found for source date {request.source_date}",
        )
    
    # Copy to each target date
    copied_days: list[AvailabilityDay] = []
    for target_date in request.target_dates:
        if target_date == request.source_date:
            continue  # Skip copying to self
        
        # Delete existing availability for target date
        await db.execute(
            delete(Availability).where(Availability.date == target_date)
        )
        
        # Copy slots
        target_slots: list[TimeSlot] = []
        for source_slot in source_slots:
            new_availability = Availability(
                date=target_date,
                start_time=source_slot.start_time,
                end_time=source_slot.end_time,
            )
            db.add(new_availability)
            target_slots.append(TimeSlot(
                start_time=source_slot.start_time,
                end_time=source_slot.end_time,
            ))
        
        copied_days.append(AvailabilityDay(date=target_date, slots=target_slots))
    
    await db.commit()
    
    return AvailabilityResponse(days=copied_days)