"""
Export API - Data Export Endpoints

Endpoints for exporting entity data to CSV/Excel.

Available entities: tickets, customers, subscriptions, field_agents, sales_orders

Authorization:
- platform_admin, client_admin, contractor_admin: Full access
- project_manager, sales_manager, dispatcher: Project-scoped access
- field_agent, sales_agent: No access
"""
from fastapi import APIRouter, Depends, HTTPException, status
from fastapi.responses import StreamingResponse
from sqlalchemy.orm import Session
from typing import List
import logging
from datetime import datetime

from app.api.deps import get_db, get_current_user
from app.models.user import User
from app.schemas.export import (
    ExportRequest,
    AvailableColumnsResponse,
    ColumnMetadata
)
from app.services.export_service import ExportService
from app.config.export_columns import get_available_columns

router = APIRouter()
logger = logging.getLogger(__name__)


# ============================================
# GET AVAILABLE COLUMNS
# ============================================

@router.get("/{entity}/columns", response_model=AvailableColumnsResponse)
async def get_available_export_columns(
    entity: str,
    current_user: User = Depends(get_current_user)
):
    """
    Get list of available columns for export.
    
    Returns column metadata including:
    - key: Column identifier for API requests
    - label: Human-readable header
    - requires_join: Whether column needs database join (affects performance)
    
    Available entities:
    - tickets: Work orders/tickets
    - customers: Customer records
    - subscriptions: Active service subscriptions
    - field_agents: Field agent users
    - sales_orders: Sales orders
    
    Authorization: project_manager+, dispatcher+, admins
    """
    # Check authorization
    if not ExportService.can_user_export(current_user):
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="You do not have permission to export data"
        )
    
    # Get columns for entity
    columns_data = get_available_columns(entity)
    
    if not columns_data:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail=f"Entity '{entity}' not found or has no exportable columns"
        )
    
    # Convert to schema
    columns = [ColumnMetadata(**col_data) for col_data in columns_data]
    
    return AvailableColumnsResponse(
        entity=entity,
        columns=columns
    )


# ============================================
# EXPORT DATA
# ============================================

@router.post("/{entity}/export")
async def export_entity_data(
    entity: str,
    request: ExportRequest,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user)
):
    """
    Export entity data to CSV/Excel.
    
    Request body:
    - columns: List of column keys to export (get from /columns endpoint)
    - filters: Optional filters to apply (project_id, status, etc.)
    - format: Export format ('csv' or 'excel')
    
    Response: File download
    
    Limits:
    - Max file size: 1MB
    - If file exceeds limit, reduce columns or add filters
    
    Example filters:
    - tickets: project_id, status, priority, ticket_type, region_id
    - customers: client_id, is_active, region_id
    - subscriptions: project_id, status, service_type, region_id
    - field_agents: contractor_id, is_active, status
    - sales_orders: project_id, status, is_processed, region_id
    
    Authorization: project_manager+, dispatcher+, admins
    """
    try:
        # Ensure entity in request matches path parameter
        if request.entity != entity:
            raise HTTPException(
                status_code=status.HTTP_400_BAD_REQUEST,
                detail=f"Entity mismatch: path='{entity}', body='{request.entity}'"
            )
        
        # Call export service
        file_buffer = ExportService.export_entity(
            db=db,
            entity=request.entity,
            columns=request.columns,
            filters=request.filters,
            format=request.format,
            current_user=current_user,
            calculated_fields=request.calculated_fields,
            aggregations=request.aggregations,
            group_by=request.group_by
        )
        
        # Prepare filename
        timestamp = datetime.utcnow().strftime('%Y%m%d_%H%M%S')
        filename = f"{entity}_export_{timestamp}.{request.format}"
        
        # Determine media type
        if request.format == 'csv':
            media_type = 'text/csv'
        elif request.format == 'excel':
            media_type = 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet'
        else:
            media_type = 'application/octet-stream'
        
        # Return file as streaming response
        return StreamingResponse(
            file_buffer,
            media_type=media_type,
            headers={
                'Content-Disposition': f'attachment; filename="{filename}"',
                'Content-Length': str(file_buffer.getbuffer().nbytes)
            }
        )
    
    except HTTPException:
        raise
    except Exception as e:
        logger.error(f"Export failed: {str(e)}")
        raise HTTPException(
            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
            detail=f"Export failed: {str(e)}"
        )


# ============================================
# EXPORT PRESETS (Future Feature)
# ============================================

@router.get("/{entity}/presets")
async def get_export_presets(
    entity: str,
    current_user: User = Depends(get_current_user)
):
    """
    Get saved export presets for entity.
    
    Presets are pre-configured column selections for common export scenarios.
    
    Example presets for tickets:
    - basic: id, ticket_name, status, priority, customer_name
    - detailed: All fields
    - analytics: status, priority, created_at, completed_at, sla_violated
    
    Future feature: Currently returns empty list.
    
    Authorization: project_manager+, dispatcher+, admins
    """
    # Check authorization
    if not ExportService.can_user_export(current_user):
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="You do not have permission to export data"
        )
    
    # TODO: Implement saved presets (future feature)
    return {
        "entity": entity,
        "presets": []
    }