src/app/api/v1/reports.py

"""
REPORTS Endpoints

Provides structured data generation and CSV exports for:
- SLA Compliance
- User Performance
- Financial Summaries
- Inventory Usage
"""
from fastapi import APIRouter, Depends, HTTPException, status
from fastapi.responses import StreamingResponse
from sqlalchemy.orm import Session
from datetime import datetime
from typing import Any

from app.api.deps import get_db, get_current_user
from app.models.user import User
from app.schemas.report import (
    ReportFilter, 
    ReportResponse, 
    ReportMetaData, 
    ReportFormat
)
from app.services.report_service import ReportService
from app.core.permissions import require_permission

router = APIRouter()

@router.post("/generate", response_model=ReportResponse)
@require_permission("view_reports")
async def generate_report(
    filters: ReportFilter,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user)
) -> Any:
    """
    Generate a JSON report for visualization/tables.
    
    **Report Types:**
    - `sla_compliance`: Tickets vs Due Dates
    - `user_performance`: Aggregated timesheet stats
    - `financial_summary`: Revenue & Expenses ledger
    - `inventory_usage`: Items installed/consumed
    
    **Performance:**
    - Designed for sub-2 second response times.
    - Uses aggregated warehouse tables (Timesheets) where possible.
    """
    try:
        data = ReportService.generate_report_data(db, filters, current_user)
        
        return ReportResponse(
            meta=ReportMetaData(
                generated_at=datetime.utcnow(),
                record_count=len(data),
                filters_applied=filters.model_dump(),
                report_type=filters.report_type
            ),
            data=data
        )
    except Exception as e:
        raise HTTPException(
            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
            detail=f"Report generation failed: {str(e)}"
        )


@router.post("/export")
@require_permission("export_reports")
async def export_report(
    filters: ReportFilter,
    format: ReportFormat = ReportFormat.CSV,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user)
):
    """
    Generate and download a report file (CSV).
    
    Designed to work with the same filters as the `/generate` endpoint.
    Returns a File Download stream.
    """
    if format != ReportFormat.CSV:
        raise HTTPException(
            status_code=status.HTTP_400_BAD_REQUEST,
            detail="Only CSV export is currently supported."
        )

    try:
        # 1. Generate Data
        data = ReportService.generate_report_data(db, filters, current_user)
        
        # 2. Convert to CSV Stream
        csv_file = ReportService.generate_csv_export(data)
        
        # 3. Create Filename
        timestamp = datetime.now().strftime("%Y%m%d_%H%M")
        filename = f"{filters.report_type}_{timestamp}.csv"
        
        return StreamingResponse(
            csv_file,
            media_type="text/csv",
            headers={"Content-Disposition": f"attachment; filename={filename}"}
        )

    except Exception as e:
        raise HTTPException(
            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
            detail=f"Export failed: {str(e)}"
        )