from fastapi import APIRouter, Depends, HTTPException, status
from fastapi.responses import StreamingResponse
from sqlalchemy.orm import Session
from sqlalchemy import select, func, and_, desc
from datetime import date, datetime, timedelta
from typing import Dict, Any, List
import asyncio
import json

from app.core.database import get_db
from app.core import security
from app.core.security import RoleCheckerSSE
from app.core import event_bus
from app.crud import crud
from app.schemas import schemas
from app.models import models

router = APIRouter()

checker_view = security.RoleChecker(["Super Admin", "Admin", "HR"])

@router.get("/dashboard-summary")
def get_dashboard_summary(
    db: Session = Depends(get_db),
    current_user: models.User = Depends(checker_view)
):
    today = date.today()
    
    # 1. Total Employees
    total_employees = db.query(func.count(models.Employee.id)).filter(models.Employee.status == "Active").scalar() or 0
    
    # 2. Present Today (Status = Present or Late or Half Day)
    present_today = db.query(func.count(models.Attendance.id)).filter(
        and_(
            models.Attendance.date == today,
            models.Attendance.status.in_(["Present", "Late", "Half Day"])
        )
    ).scalar() or 0
    
    # 3. Late Today
    late_today = db.query(func.count(models.Attendance.id)).filter(
        and_(
            models.Attendance.date == today,
            models.Attendance.status == "Late"
        )
    ).scalar() or 0
    
    # 4. Checked Out
    checked_out_today = db.query(func.count(models.Attendance.id)).filter(
        and_(
            models.Attendance.date == today,
            models.Attendance.check_out.isnot(None)
        )
    ).scalar() or 0
    
    # 5. Absent Today
    # Active employees minus present today
    absent_today = max(0, total_employees - present_today)
    
    # 6. Attendance Rate
    attendance_percentage = (present_today / total_employees * 100) if total_employees > 0 else 0.0
    
    return {
        "total_employees": total_employees,
        "present_today": present_today,
        "absent_today": absent_today,
        "late_today": late_today,
        "checked_out_today": checked_out_today,
        "attendance_percentage": round(attendance_percentage, 1)
    }

@router.get("/attendance-trends")
def get_attendance_trends(
    days: int = 7,
    db: Session = Depends(get_db),
    current_user: models.User = Depends(checker_view)
):
    """
    Returns daily stats for the last N days (date, present, late, absent) for ECharts.
    """
    end_date = date.today()
    start_date = end_date - timedelta(days=days - 1)
    
    # Generate list of dates
    date_list = [start_date + timedelta(days=i) for i in range(days)]
    
    # Get total active employees
    total_active = db.query(func.count(models.Employee.id)).filter(models.Employee.status == "Active").scalar() or 0
    
    trends = []
    for d in date_list:
        present = db.query(func.count(models.Attendance.id)).filter(
            and_(
                models.Attendance.date == d,
                models.Attendance.status.in_(["Present", "Late", "Half Day"])
            )
        ).scalar() or 0
        
        late = db.query(func.count(models.Attendance.id)).filter(
            and_(
                models.Attendance.date == d,
                models.Attendance.status == "Late"
            )
        ).scalar() or 0
        
        absent = max(0, total_active - present)
        
        trends.append({
            "date": d.isoformat(),
            "present": present,
            "late": late,
            "absent": absent
        })
        
    return trends

@router.get("/department-distribution")
def get_department_distribution(
    db: Session = Depends(get_db),
    current_user: models.User = Depends(checker_view)
):
    """
    Returns employee and attendance counts by department for ECharts.
    """
    today = date.today()
    departments = db.query(models.Department).all()
    
    dist = []
    for dept in departments:
        # Total active in dept
        total_in_dept = db.query(func.count(models.Employee.id)).filter(
            and_(
                models.Employee.department_id == dept.id,
                models.Employee.status == "Active"
            )
        ).scalar() or 0
        
        # Present today in dept
        present_in_dept = db.query(func.count(models.Attendance.id)).join(models.Employee).filter(
            and_(
                models.Employee.department_id == dept.id,
                models.Attendance.date == today,
                models.Attendance.status.in_(["Present", "Late", "Half Day"])
            )
        ).scalar() or 0
        
        dist.append({
            "id": dept.id,
            "department": dept.name,
            "code": dept.code,
            "total_employees": total_in_dept,
            "present_today": present_in_dept
        })
        
    return dist

@router.get("/recent-activity", response_model=List[schemas.AttendanceLogOut])
def get_recent_activity(
    limit: int = 10,
    db: Session = Depends(get_db),
    current_user: models.User = Depends(checker_view)
):
    """
    Returns latest kiosk scan logs for the dashboard tickfeed.
    """
    cutoff = datetime.utcnow() - timedelta(hours=24)
    return db.query(models.AttendanceLog).filter(models.AttendanceLog.timestamp >= cutoff).order_by(desc(models.AttendanceLog.timestamp)).limit(limit).all()


@router.get("/live-stream")
async def live_stream(
    current_user: models.User = Depends(RoleCheckerSSE(["Super Admin", "Admin", "HR"]))
):
    """
    Real-time Server-Sent Events (SSE) feed of kiosk scans.
    """
    async def event_generator():
        queue = event_bus.subscribe()
        try:
            while True:
                # Wait for next event published to the bus
                event_data = await queue.get()
                # Yield standard SSE formatted message
                yield f"data: {json.dumps(event_data)}\n\n"
        except asyncio.CancelledError:
            # Client disconnected
            pass
        finally:
            event_bus.unsubscribe(queue)

    return StreamingResponse(event_generator(), media_type="text/event-stream")