feat(T06): Verkaufsmodul + Rechtsdokumente + DATEV-Export + Sales UI

backend/app/services/datev_service.py

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+"""DATEV export service: create exports, list exports, generate CSV."""
+
+from __future__ import annotations
+
+import os
+import uuid
+from datetime import date
+from decimal import Decimal
+from typing import Any
+
+from sqlalchemy import and_, func, select
+from sqlalchemy.ext.asyncio import AsyncSession
+from sqlalchemy.orm import selectinload
+
+from app.models.datev_export import DATEVExport
+from app.models.sale import Sale
+from app.utils.datev import generate_datev_csv, validate_datev_csv
+
+
+async def create_export(
+    db: AsyncSession,
+    start_date: date,
+    end_date: date,
+    output_dir: str = "/tmp/datev_exports",
+) -> DATEVExport:
+    """Create a DATEV export for the given date range.
+
+    Queries all completed sales within the date range, generates a CSV file,
+    and stores the export record.
+
+    Args:
+        db: Async session.
+        start_date: Start of the date range (inclusive).
+        end_date: End of the date range (inclusive).
+        output_dir: Directory to save the CSV file.
+
+    Returns:
+        DATEVExport model instance.
+    """
+    # Query completed sales within date range
+    stmt = (
+        select(Sale)
+        .options(
+            selectinload(Sale.vehicle),
+            selectinload(Sale.buyer),
+            selectinload(Sale.seller),
+        )
+        .where(
+            and_(
+                Sale.sale_date >= start_date,
+                Sale.sale_date <= end_date,
+                Sale.status == "completed",
+            )
+        )
+        .order_by(Sale.sale_date.asc())
+    )
+    result = await db.execute(stmt)
+    sales = list(result.scalars().all())
+
+    # Generate CSV content
+    csv_content = generate_datev_csv(sales)
+
+    # Calculate total amount
+    total_amount = sum(
+        (s.sale_price or Decimal("0")) for s in sales
+    )
+
+    # Save CSV file
+    os.makedirs(output_dir, exist_ok=True)
+    export_id = uuid.uuid4()
+    file_path = os.path.join(output_dir, f"datev_export_{export_id}.csv")
+    with open(file_path, "w", encoding="utf-8") as f:
+        f.write(csv_content)
+
+    # Create export record
+    export = DATEVExport(
+        id=export_id,
+        start_date=start_date,
+        end_date=end_date,
+        file_path=file_path,
+        total_amount=total_amount,
+    )
+    db.add(export)
+    await db.flush()
+    await db.refresh(export)
+
+    return export
+
+
+async def list_exports(
+    db: AsyncSession,
+    page: int = 1,
+    page_size: int = 20,
+) -> tuple[list[DATEVExport], int]:
+    """List DATEV exports with pagination.
+
+    Returns (exports, total_count).
+    """
+    count_stmt = select(func.count(DATEVExport.id))
+    total_result = await db.execute(count_stmt)
+    total = total_result.scalar_one()
+
+    data_stmt = (
+        select(DATEVExport)
+        .order_by(DATEVExport.created_at.desc())
+        .offset((page - 1) * page_size)
+        .limit(page_size)
+    )
+    result = await db.execute(data_stmt)
+    exports = list(result.scalars().all())
+
+    return exports, total
+
+
+async def get_export_csv(db: AsyncSession, export_id: uuid.UUID) -> tuple[str, bytes] | None:
+    """Get the CSV content for a DATEV export.
+
+    Args:
+        db: Async session.
+        export_id: Export ID.
+
+    Returns:
+        Tuple of (filename, csv_bytes) or None if export not found.
+    """
+    stmt = select(DATEVExport).where(DATEVExport.id == export_id)
+    result = await db.execute(stmt)
+    export = result.scalar_one_or_none()
+
+    if export is None:
+        return None
+
+    if export.file_path and os.path.exists(export.file_path):
+        with open(export.file_path, "r", encoding="utf-8") as f:
+            csv_content = f.read()
+    else:
+        # Regenerate from sales if file is missing
+        sales_stmt = (
+            select(Sale)
+            .options(selectinload(Sale.vehicle))
+            .where(
+                and_(
+                    Sale.sale_date >= export.start_date,
+                    Sale.sale_date <= export.end_date,
+                    Sale.status == "completed",
+                )
+            )
+            .order_by(Sale.sale_date.asc())
+        )
+        sales_result = await db.execute(sales_stmt)
+        sales = list(sales_result.scalars().all())
+        csv_content = generate_datev_csv(sales)
+
+    filename = f"datev_export_{export.id}.csv"
+    return filename, csv_content.encode("utf-8")