from fastapi import APIRouter, Depends, HTTPException
from sqlalchemy.ext.asyncio import AsyncSession
from sqlalchemy import select, delete
from typing import List, Dict, Any, Optional
from datetime import datetime, timedelta
from ..core.dependencies import get_current_active_user
from ..db.database import get_db
from ..db.models import Event, User
from pydantic import BaseModel

router = APIRouter()

class RecurringEventCreate(BaseModel):
    title: str
    description: str
    start_time: datetime
    end_time: datetime
    recurrence_pattern: str
    recurrence_end_date: Optional[datetime] = None
    attendees: List[str] = []
    reminder_minutes: int = 30

class RecurringEventUpdate(BaseModel):
    title: Optional[str] = None
    description: Optional[str] = None
    start_time: Optional[datetime] = None
    end_time: Optional[datetime] = None
    attendees: Optional[List[str]] = None
    reminder_minutes: Optional[int] = None

@router.post("/recurring-events")
async def create_recurring_event(
    event_data: RecurringEventCreate,
    current_user: User = Depends(get_current_active_user),
    db: AsyncSession = Depends(get_db)
) -> List[Dict[str, Any]]:
    """Create a new recurring event"""
    if event_data.recurrence_pattern not in ["daily", "weekly", "monthly", "yearly"]:
        raise HTTPException(
            status_code=400,
            detail="Invalid recurrence pattern. Must be one of: daily, weekly, monthly, yearly"
        )

    if event_data.start_time >= event_data.end_time:
        raise HTTPException(
            status_code=400,
            detail="End time must be after start time"
        )

    events = []
    current_start = event_data.start_time
    current_end = event_data.end_time
    duration = event_data.end_time - event_data.start_time
    sequence_number = 0

    while True:
        if event_data.recurrence_end_date and current_start > event_data.recurrence_end_date:
            break

        event = Event(
            user_id=current_user.id,
            title=event_data.title,
            description=event_data.description,
            start_time=current_start,
            end_time=current_end,
            attendees=event_data.attendees,
            reminder_minutes=event_data.reminder_minutes,
            is_recurring=True,
            recurrence_pattern=event_data.recurrence_pattern,
            sequence_number=sequence_number,
            status="scheduled"
        )
        db.add(event)
        events.append(event)

        # Calculate next occurrence
        sequence_number += 1
        if event_data.recurrence_pattern == "daily":
            current_start += timedelta(days=1)
        elif event_data.recurrence_pattern == "weekly":
            current_start += timedelta(weeks=1)
        elif event_data.recurrence_pattern == "monthly":
            # Add one month (approximately)
            if current_start.month == 12:
                current_start = current_start.replace(year=current_start.year + 1, month=1)
            else:
                current_start = current_start.replace(month=current_start.month + 1)
        elif event_data.recurrence_pattern == "yearly":
            current_start = current_start.replace(year=current_start.year + 1)

        current_end = current_start + duration

    await db.commit()
    
    # Refresh all events to get their IDs
    for event in events:
        await db.refresh(event)

    return events

@router.put("/recurring-events/{event_id}")
async def update_recurring_event(
    event_id: int,
    event_update: RecurringEventUpdate,
    update_future: bool = True,
    current_user: User = Depends(get_current_active_user),
    db: AsyncSession = Depends(get_db)
) -> List[Dict[str, Any]]:
    """Update a recurring event and optionally its future occurrences"""
    update_data = event_update.dict(exclude_unset=True)
    if not update_data:
        raise HTTPException(status_code=400, detail="No update data provided")

    # Get the original event
    stmt = select(Event).where(
        Event.id == event_id,
        Event.user_id == current_user.id
    )
    result = await db.execute(stmt)
    event = result.scalar_one_or_none()

    if not event:
        raise HTTPException(
            status_code=404,
            detail="Event not found or you don't have permission to update it"
        )

    updated_events = [event]

    # Update future occurrences if requested
    if update_future and event.is_recurring:
        future_stmt = select(Event).where(
            Event.recurrence_group == event.recurrence_group,
            Event.sequence_number > event.sequence_number,
            Event.user_id == current_user.id
        )
        future_result = await db.execute(future_stmt)
        future_events = future_result.scalars().all()
        
        for future_event in future_events:
            for field, value in update_data.items():
                setattr(future_event, field, value)
            updated_events.append(future_event)

    await db.commit()
    return updated_events

@router.delete("/recurring-events/{event_id}")
async def delete_recurring_event(
    event_id: int,
    delete_future: bool = True,
    current_user: User = Depends(get_current_active_user),
    db: AsyncSession = Depends(get_db)
) -> Dict[str, bool]:
    """Delete a recurring event and optionally its future occurrences"""
    stmt = select(Event).where(
        Event.id == event_id,
        Event.user_id == current_user.id
    )
    result = await db.execute(stmt)
    event = result.scalar_one_or_none()

    if not event:
        raise HTTPException(
            status_code=404,
            detail="Event not found or you don't have permission to delete it"
        )

    if delete_future and event.is_recurring:
        delete_stmt = delete(Event).where(
            Event.recurrence_group == event.recurrence_group,
            Event.sequence_number >= event.sequence_number,
            Event.user_id == current_user.id
        )
        await db.execute(delete_stmt)
    else:
        await db.delete(event)

    await db.commit()
    return {"success": True}

@router.get("/recurring-events/upcoming")
async def get_upcoming_recurring_events(
    days: int = 30,
    current_user: User = Depends(get_current_active_user),
    db: AsyncSession = Depends(get_db)
) -> List[Dict[str, Any]]:
    """Get upcoming recurring events for the next N days"""
    if days <= 0 or days > 365:
        raise HTTPException(
            status_code=400,
            detail="Days parameter must be between 1 and 365"
        )

    end_date = datetime.utcnow() + timedelta(days=days)
    stmt = select(Event).where(
        Event.user_id == current_user.id,
        Event.start_time <= end_date,
        Event.is_recurring == True
    ).order_by(Event.start_time)
    
    result = await db.execute(stmt)
    return result.scalars().all()