feat: Implement supplier invoice case traceability and purchase line classification

app/billing/backend/supplier_invoices.py

@@ -22,6 +22,121 @@ import re
 logger = logging.getLogger(__name__)
 router = APIRouter()
 
+_PURCHASE_CASE_TYPE = "indkøb"
+
+
+def _resolve_procurement_customer_id() -> int:
+    """Find customer used for internally-owned procurement cases."""
+    configured_id = getattr(settings, "PROCUREMENT_CASE_CUSTOMER_ID", None)
+    if configured_id:
+        row = execute_query_single(
+            "SELECT id FROM customers WHERE id = %s AND is_active = true",
+            (configured_id,)
+        )
+        if row:
+            return int(row["id"])
+
+    bmc_row = execute_query_single(
+        """
+        SELECT id
+        FROM customers
+        WHERE is_active = true
+          AND LOWER(name) LIKE %s
+        ORDER BY CASE WHEN LOWER(name) LIKE %s THEN 0 ELSE 1 END, id
+        LIMIT 1
+        """,
+        ("%bmc%", "%bmc networks%")
+    )
+    if bmc_row:
+        return int(bmc_row["id"])
+
+    fallback = execute_query_single(
+        "SELECT id FROM customers WHERE is_active = true ORDER BY id LIMIT 1"
+    )
+    if fallback:
+        return int(fallback["id"])
+
+    raise ValueError("No active customer available for procurement case creation")
+
+
+def _ensure_case_for_supplier_invoice(
+    invoice_id: int,
+    invoice_number: str,
+    vendor_name: Optional[str],
+    total_amount,
+    currency: Optional[str],
+    file_id: Optional[int] = None,
+) -> Optional[int]:
+    """Create and link a procurement case if missing for a supplier invoice."""
+    existing = execute_query_single(
+        "SELECT sag_id FROM supplier_invoices WHERE id = %s",
+        (invoice_id,)
+    )
+    if not existing:
+        return None
+
+    current_sag_id = existing.get("sag_id")
+    if current_sag_id:
+        return int(current_sag_id)
+
+    customer_id = _resolve_procurement_customer_id()
+    vendor_label = (vendor_name or "Ukendt leverandør").strip()
+    currency_label = (currency or "DKK").strip()
+    amount_label = f"{Decimal(total_amount or 0):.2f}"
+
+    case_title = f"Leverandørfaktura {invoice_number} - {vendor_label}"
+    case_description = (
+        "Auto-oprettet fra leverandørfaktura\n"
+        f"Faktura: {invoice_number}\n"
+        f"Leverandør: {vendor_label}\n"
+        f"Beløb: {amount_label} {currency_label}\n"
+        f"Invoice ID: {invoice_id}\n"
+        f"Fil ID: {file_id or '-'}"
+    )
+
+    case_row = execute_query_single(
+        """
+        INSERT INTO sag_sager (titel, beskrivelse, type, status, customer_id)
+        VALUES (%s, %s, %s, %s, %s)
+        RETURNING id
+        """,
+        (case_title, case_description, _PURCHASE_CASE_TYPE, "åben", customer_id)
+    )
+    if not case_row:
+        return None
+
+    sag_id = int(case_row["id"])
+
+    execute_update(
+        "UPDATE supplier_invoices SET sag_id = %s WHERE id = %s",
+        (sag_id, invoice_id)
+    )
+
+    try:
+        execute_update(
+            """
+            INSERT INTO sag_kommentarer (sag_id, forfatter, indhold, er_system_besked)
+            VALUES (%s, %s, %s, %s)
+            """,
+            (
+                sag_id,
+                "Invoice Bot",
+                (
+                    "🔗 Automatisk oprettet fra leverandørfaktura\n"
+                    f"Faktura: {invoice_number}\n"
+                    f"Leverandør: {vendor_label}\n"
+                    f"Beløb: {amount_label} {currency_label}\n"
+                    f"Invoice ID: {invoice_id}"
+                ),
+                True,
+            ),
+        )
+    except Exception as comment_error:
+        logger.warning("⚠️ Could not create case comment for supplier invoice %s: %s", invoice_id, comment_error)
+
+    logger.info("✅ Linked supplier invoice %s to SAG-%s", invoice_id, sag_id)
+    return sag_id
+
 
 def _smart_extract_lines(text: str) -> List[Dict]:
     """
@@ -957,7 +1072,7 @@ async def create_invoice_from_extraction(file_id: int):
         if not extraction:
             raise HTTPException(status_code=404, detail="Ingen extraction fundet for denne fil")
         
-        extraction_data = extraction[0]
+        extraction_data = extraction
         
         # Check if vendor is matched
         if not extraction_data['vendor_matched_id']:
@@ -975,7 +1090,7 @@ async def create_invoice_from_extraction(file_id: int):
             raise HTTPException(status_code=400, detail="Faktura er allerede oprettet fra denne extraction")
         
         # Get extraction lines
-        lines = execute_query_single(
+        lines = execute_query(
             """SELECT * FROM extraction_lines 
                WHERE extraction_id = %s 
                ORDER BY line_number""",
@@ -1037,6 +1152,15 @@ async def create_invoice_from_extraction(file_id: int):
             )
         )
 
+        sag_id = _ensure_case_for_supplier_invoice(
+            invoice_id=invoice_id,
+            invoice_number=invoice_number,
+            vendor_name=extraction.get("vendor_name"),
+            total_amount=extraction_data.get("total_amount"),
+            currency=extraction_data.get("currency"),
+            file_id=file_id,
+        )
+        
         # Create invoice lines
         if lines:
             for line in lines:
@@ -1067,6 +1191,7 @@ async def create_invoice_from_extraction(file_id: int):
         return {
             "status": "success",
             "invoice_id": invoice_id,
+            "sag_id": sag_id,
             "invoice_number": invoice_number,
             "vendor_name": extraction['vendor_name'],
             "total_amount": extraction['total_amount'],
@@ -3089,6 +3214,15 @@ async def create_invoice_from_file(file_id: int, vendor_id: int) -> int:
             )
         )
 
+        _ensure_case_for_supplier_invoice(
+            invoice_id=invoice_id,
+            invoice_number=f"PENDING-{file_id}",
+            vendor_name=None,
+            total_amount=0,
+            currency="DKK",
+            file_id=file_id,
+        )
+        
         logger.info(f"✅ Created minimal invoice {invoice_id} for file {file_id}, vendor {vendor_id}")
         return invoice_id
         

app/modules/sag/backend/router.py

@@ -2240,6 +2240,73 @@ async def get_case_calendar_events(sag_id: int, include_children: bool = True):
 # VAREKØB & SALG - CRUD (Case-linked sale items)
 # ============================================================================
 
+_PURCHASE_PURPOSE_VALUES = {
+    "salg",
+    "lager",
+    "asset",
+    "intern_brug",
+    "retur_reklamation",
+    "projekt_omkostning",
+}
+
+
+def _normalize_purchase_purpose(value: Optional[object], item_type: str) -> Optional[str]:
+    if item_type != "purchase":
+        return None
+
+    if value is None:
+        return None
+
+    normalized = str(value).strip().lower()
+    if not normalized:
+        return None
+
+    if normalized not in _PURCHASE_PURPOSE_VALUES:
+        allowed = ", ".join(sorted(_PURCHASE_PURPOSE_VALUES))
+        raise HTTPException(status_code=400, detail=f"purchase_purpose must be one of: {allowed}")
+
+    return normalized
+
+
+def _resolve_purchase_traceability(
+    supplier_invoice_id_value: Optional[object],
+    supplier_invoice_line_id_value: Optional[object],
+) -> tuple[Optional[int], Optional[int]]:
+    supplier_invoice_id = _coerce_optional_int(supplier_invoice_id_value, "supplier_invoice_id")
+    supplier_invoice_line_id = _coerce_optional_int(supplier_invoice_line_id_value, "supplier_invoice_line_id")
+
+    if supplier_invoice_line_id is not None and supplier_invoice_id is None:
+        line_row = execute_query_single(
+            "SELECT supplier_invoice_id FROM supplier_invoice_lines WHERE id = %s",
+            (supplier_invoice_line_id,)
+        )
+        if not line_row:
+            raise HTTPException(status_code=400, detail="Invalid supplier_invoice_line_id")
+        supplier_invoice_id = int(line_row["supplier_invoice_id"])
+
+    if supplier_invoice_id is not None:
+        invoice_exists = execute_query_single(
+            "SELECT id FROM supplier_invoices WHERE id = %s",
+            (supplier_invoice_id,)
+        )
+        if not invoice_exists:
+            raise HTTPException(status_code=400, detail="Invalid supplier_invoice_id")
+
+    if supplier_invoice_line_id is not None:
+        line_exists = execute_query_single(
+            "SELECT id, supplier_invoice_id FROM supplier_invoice_lines WHERE id = %s",
+            (supplier_invoice_line_id,)
+        )
+        if not line_exists:
+            raise HTTPException(status_code=400, detail="Invalid supplier_invoice_line_id")
+        if supplier_invoice_id is not None and int(line_exists["supplier_invoice_id"]) != supplier_invoice_id:
+            raise HTTPException(
+                status_code=400,
+                detail="supplier_invoice_line_id does not belong to supplier_invoice_id",
+            )
+
+    return supplier_invoice_id, supplier_invoice_line_id
+
 @router.get("/sag/{sag_id}/sale-items")
 async def list_sale_items(sag_id: int):
     """List sale items for a case."""
@@ -2290,27 +2357,68 @@ async def create_sale_item(sag_id: int, data: dict):
         if status not in ("draft", "confirmed", "cancelled"):
             raise HTTPException(status_code=400, detail="status must be draft, confirmed, or cancelled")
 
-        query = """
+        has_purchase_columns = table_has_column("sag_salgsvarer", "purchase_purpose")
-            INSERT INTO sag_salgsvarer
+        purchase_purpose = None
-                (sag_id, type, description, quantity, unit, unit_price, amount, currency, status, line_date, external_ref, product_id)
+        supplier_invoice_id = None
-            VALUES
+        supplier_invoice_line_id = None
-                (%s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s)
+        if has_purchase_columns:
-            RETURNING *
+            purchase_purpose = _normalize_purchase_purpose(data.get("purchase_purpose"), item_type)
-        """
+            supplier_invoice_id, supplier_invoice_line_id = _resolve_purchase_traceability(
-        params = (
+                data.get("supplier_invoice_id"),
-            sag_id,
+                data.get("supplier_invoice_line_id"),
-            item_type,
+            )
-            description,
+            if item_type != "purchase":
-            data.get("quantity"),
+                supplier_invoice_id = None
-            data.get("unit"),
+                supplier_invoice_line_id = None
-            data.get("unit_price"),
+
-            amount,
+        if has_purchase_columns:
-            data.get("currency", "DKK"),
+            query = """
-            status,
+                INSERT INTO sag_salgsvarer
-            data.get("line_date"),
+                    (sag_id, type, description, quantity, unit, unit_price, amount, currency, status, line_date, external_ref, product_id,
-            data.get("external_ref"),
+                     purchase_purpose, supplier_invoice_id, supplier_invoice_line_id)
-            data.get("product_id"),
+                VALUES
-        )
+                    (%s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s)
+                RETURNING *
+            """
+            params = (
+                sag_id,
+                item_type,
+                description,
+                data.get("quantity"),
+                data.get("unit"),
+                data.get("unit_price"),
+                amount,
+                data.get("currency", "DKK"),
+                status,
+                data.get("line_date"),
+                data.get("external_ref"),
+                data.get("product_id"),
+                purchase_purpose,
+                supplier_invoice_id,
+                supplier_invoice_line_id,
+            )
+        else:
+            query = """
+                INSERT INTO sag_salgsvarer
+                    (sag_id, type, description, quantity, unit, unit_price, amount, currency, status, line_date, external_ref, product_id)
+                VALUES
+                    (%s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s)
+                RETURNING *
+            """
+            params = (
+                sag_id,
+                item_type,
+                description,
+                data.get("quantity"),
+                data.get("unit"),
+                data.get("unit_price"),
+                amount,
+                data.get("currency", "DKK"),
+                status,
+                data.get("line_date"),
+                data.get("external_ref"),
+                data.get("product_id"),
+            )
         result = execute_query(query, params)
         if result:
             logger.info("✅ Sale item created for case %s", sag_id)
@@ -2349,7 +2457,7 @@ async def update_sale_item(sag_id: int, item_id: int, updates: dict):
     """Update a sale item for a case."""
     try:
         check = execute_query(
-            "SELECT id FROM sag_salgsvarer WHERE id = %s AND sag_id = %s",
+            "SELECT id, type FROM sag_salgsvarer WHERE id = %s AND sag_id = %s",
             (item_id, sag_id)
         )
         if not check:
@@ -2367,10 +2475,18 @@ async def update_sale_item(sag_id: int, item_id: int, updates: dict):
             "line_date",
             "external_ref",
             "product_id",
+            "purchase_purpose",
+            "supplier_invoice_id",
+            "supplier_invoice_line_id",
         ]
 
         set_clauses = []
         params = []
+        has_purchase_columns = table_has_column("sag_salgsvarer", "purchase_purpose")
+        current_type = (check[0].get("type") or "sale").lower()
+        next_type = current_type
+        if "type" in updates:
+            next_type = (updates.get("type") or "").lower()
 
         for field in allowed_fields:
             if field in updates:
@@ -2386,10 +2502,56 @@ async def update_sale_item(sag_id: int, item_id: int, updates: dict):
                         raise HTTPException(status_code=400, detail="status must be draft, confirmed, or cancelled")
                     set_clauses.append("status = %s")
                     params.append(value)
+                elif field == "purchase_purpose":
+                    if not has_purchase_columns:
+                        continue
+                    value = _normalize_purchase_purpose(updates.get(field), next_type)
+                    set_clauses.append("purchase_purpose = %s")
+                    params.append(value)
+                elif field in ("supplier_invoice_id", "supplier_invoice_line_id"):
+                    # handled together below to keep consistency between IDs
+                    continue
                 else:
                     set_clauses.append(f"{field} = %s")
                     params.append(updates[field])
 
+        if has_purchase_columns and (
+            "supplier_invoice_id" in updates
+            or "supplier_invoice_line_id" in updates
+            or next_type != current_type
+        ):
+            raw_supplier_invoice_id = updates.get("supplier_invoice_id") if "supplier_invoice_id" in updates else None
+            raw_supplier_invoice_line_id = updates.get("supplier_invoice_line_id") if "supplier_invoice_line_id" in updates else None
+
+            if "supplier_invoice_id" not in updates or "supplier_invoice_line_id" not in updates:
+                current_refs = execute_query_single(
+                    "SELECT supplier_invoice_id, supplier_invoice_line_id FROM sag_salgsvarer WHERE id = %s AND sag_id = %s",
+                    (item_id, sag_id)
+                ) or {}
+                if "supplier_invoice_id" not in updates:
+                    raw_supplier_invoice_id = current_refs.get("supplier_invoice_id")
+                if "supplier_invoice_line_id" not in updates:
+                    raw_supplier_invoice_line_id = current_refs.get("supplier_invoice_line_id")
+
+            supplier_invoice_id, supplier_invoice_line_id = _resolve_purchase_traceability(
+                raw_supplier_invoice_id,
+                raw_supplier_invoice_line_id,
+            )
+
+            if next_type != "purchase":
+                supplier_invoice_id = None
+                supplier_invoice_line_id = None
+
+            set_clauses.append("supplier_invoice_id = %s")
+            params.append(supplier_invoice_id)
+            set_clauses.append("supplier_invoice_line_id = %s")
+            params.append(supplier_invoice_line_id)
+
+        if has_purchase_columns and next_type != "purchase":
+            if "purchase_purpose" not in updates:
+                set_clauses.append("purchase_purpose = %s")
+                params.append(None)
+
         if not set_clauses:
             raise HTTPException(status_code=400, detail="No valid fields to update")
 

app/modules/sag/templates/detail.html

@@ -6024,6 +6024,7 @@
                                         <th>Enhed</th>
                                         <th>Enhedspris</th>
                                         <th>Linjesum</th>
+                                        <th>Formål</th>
                                         <th>Kilde-sag</th>
                                         <th>Status</th>
                                         <th class="text-end pe-4">Handlinger</th>
@@ -6031,7 +6032,7 @@
                                 </thead>
                                 <tbody id="saleItemsPurchaseBody">
                                     <tr>
-                                        <td colspan="9" class="text-center py-4 text-muted">Indlæser indkøbslinjer...</td>
+                                        <td colspan="10" class="text-center py-4 text-muted">Indlæser indkøbslinjer...</td>
                                     </tr>
                                 </tbody>
                             </table>
@@ -7282,6 +7283,20 @@
 
         let saleItemsCache = [];
 
+        const purchasePurposeLabels = {
+            salg: 'Salg',
+            lager: 'Lager',
+            asset: 'Asset',
+            intern_brug: 'Intern brug',
+            retur_reklamation: 'Retur/reklamation',
+            projekt_omkostning: 'Projektomkostning'
+        };
+
+        function purchasePurposeLabel(value) {
+            if (!value) return '-';
+            return purchasePurposeLabels[value] || value;
+        }
+
         async function loadVarekobSalg() {
             try {
                 const res = await fetch(`/api/v1/sag/${salesCaseId}/varekob-salg?include_subcases=true`);
@@ -7323,9 +7338,10 @@
             const salesItems = items.filter(item => (item.type || '').toLowerCase() !== 'purchase');
             const purchaseItems = items.filter(item => (item.type || '').toLowerCase() === 'purchase');
 
-            const renderRows = (list) => {
+            const renderRows = (list, isPurchase) => {
                 if (!list.length) {
-                    return '<tr><td colspan="9" class="text-center py-4 text-muted">Ingen linjer</td></tr>';
+                    const columns = isPurchase ? 10 : 9;
+                    return `<tr><td colspan="${columns}" class="text-center py-4 text-muted">Ingen linjer</td></tr>`;
                 }
 
                 return list.map(item => {
@@ -7334,6 +7350,9 @@
                     const sourceBadge = isSubcase
                         ? `<span class="badge bg-warning text-dark ms-2">Under-sag</span>`
                         : `<span class="badge bg-light text-dark border ms-2">Denne sag</span>`;
+                    const purposeCell = isPurchase
+                        ? `<td><span class="badge bg-info-subtle text-dark border">${purchasePurposeLabel(item.purchase_purpose)}</span></td>`
+                        : '';
                     return `
                         <tr>
                             <td class="ps-4">${item.line_date || '-'}</td>
@@ -7342,6 +7361,7 @@
                             <td>${item.unit || '-'}</td>
                             <td>${item.unit_price != null ? formatCurrency(item.unit_price) : '-'}</td>
                             <td class="fw-bold">${formatCurrency(item.amount)}</td>
+                            ${purposeCell}
                             <td>${item.source_sag_titel || '-'}${sourceBadge}</td>
                             <td><span class="badge bg-light text-dark border">${statusLabel}</span></td>
                             <td class="text-end pe-4">
@@ -7355,8 +7375,8 @@
                 }).join('');
             };
 
-            salesBody.innerHTML = renderRows(salesItems);
+            salesBody.innerHTML = renderRows(salesItems, false);
-            purchaseBody.innerHTML = renderRows(purchaseItems);
+            purchaseBody.innerHTML = renderRows(purchaseItems, true);
 
             const salesSum = salesItems.reduce((sum, item) => sum + Number(item.amount || 0), 0);
             const purchaseSum = purchaseItems.reduce((sum, item) => sum + Number(item.amount || 0), 0);
@@ -7400,10 +7420,30 @@
             document.getElementById('sale_amount').value = item?.amount ?? '';
             document.getElementById('sale_currency').value = item?.currency || 'DKK';
             document.getElementById('sale_external_ref').value = item?.external_ref || '';
+            document.getElementById('sale_purchase_purpose').value = item?.purchase_purpose || '';
+            document.getElementById('sale_supplier_invoice_id').value = item?.supplier_invoice_id || '';
+            document.getElementById('sale_supplier_invoice_line_id').value = item?.supplier_invoice_line_id || '';
+
+            togglePurchaseFields();
 
             new bootstrap.Modal(document.getElementById('saleItemModal')).show();
         }
 
+        function togglePurchaseFields() {
+            const type = document.getElementById('sale_type').value;
+            const purchaseFields = document.getElementById('sale_purchase_fields');
+            if (!purchaseFields) return;
+
+            if (type === 'purchase') {
+                purchaseFields.classList.remove('d-none');
+            } else {
+                purchaseFields.classList.add('d-none');
+                document.getElementById('sale_purchase_purpose').value = '';
+                document.getElementById('sale_supplier_invoice_id').value = '';
+                document.getElementById('sale_supplier_invoice_line_id').value = '';
+            }
+        }
+
         function openSaleItemModalById(itemId) {
             const item = saleItemsCache.find((entry) => entry.id === itemId);
             openSaleItemModal(item || null);
@@ -7429,9 +7469,18 @@
                 unit_price: document.getElementById('sale_unit_price').value || null,
                 amount: document.getElementById('sale_amount').value,
                 currency: document.getElementById('sale_currency').value || 'DKK',
-                external_ref: document.getElementById('sale_external_ref').value || null
+                external_ref: document.getElementById('sale_external_ref').value || null,
+                purchase_purpose: document.getElementById('sale_purchase_purpose').value || null,
+                supplier_invoice_id: document.getElementById('sale_supplier_invoice_id').value || null,
+                supplier_invoice_line_id: document.getElementById('sale_supplier_invoice_line_id').value || null
             };
 
+            if (payload.type !== 'purchase') {
+                payload.purchase_purpose = null;
+                payload.supplier_invoice_id = null;
+                payload.supplier_invoice_line_id = null;
+            }
+
             if (!payload.description || !payload.amount) {
                 alert('Beskrivelse og linjesum er påkrævet.');
                 return;
@@ -7470,8 +7519,10 @@
         document.addEventListener('DOMContentLoaded', function() {
             const qtyInput = document.getElementById('sale_quantity');
             const priceInput = document.getElementById('sale_unit_price');
+            const typeInput = document.getElementById('sale_type');
             if (qtyInput) qtyInput.addEventListener('input', updateSaleAmount);
             if (priceInput) priceInput.addEventListener('input', updateSaleAmount);
+            if (typeInput) typeInput.addEventListener('change', togglePurchaseFields);
             loadVarekobSalg();
         });
     </script>
@@ -8769,6 +8820,30 @@
                                 <label class="form-label">Reference</label>
                                 <input type="text" class="form-control" id="sale_external_ref" placeholder="Valgfri reference">
                             </div>
+                            <div class="col-12 d-none" id="sale_purchase_fields">
+                                <div class="row g-3">
+                                    <div class="col-md-4">
+                                        <label class="form-label">Indkøbsformål</label>
+                                        <select class="form-select" id="sale_purchase_purpose">
+                                            <option value="">Vælg formål</option>
+                                            <option value="salg">Salg</option>
+                                            <option value="lager">Lager</option>
+                                            <option value="asset">Asset</option>
+                                            <option value="intern_brug">Intern brug</option>
+                                            <option value="retur_reklamation">Retur/reklamation</option>
+                                            <option value="projekt_omkostning">Projektomkostning</option>
+                                        </select>
+                                    </div>
+                                    <div class="col-md-4">
+                                        <label class="form-label">Leverandørfaktura ID</label>
+                                        <input type="number" class="form-control" id="sale_supplier_invoice_id" min="1" step="1" placeholder="Fx 1254">
+                                    </div>
+                                    <div class="col-md-4">
+                                        <label class="form-label">Fakturalinje ID</label>
+                                        <input type="number" class="form-control" id="sale_supplier_invoice_line_id" min="1" step="1" placeholder="Fx 8921">
+                                    </div>
+                                </div>
+                            </div>
                         </div>
                     </form>
                 </div>

migrations/169_supplier_invoice_case_traceability.sql

@@ -0,0 +1,47 @@
+-- Migration 169: Supplier invoice -> case traceability and purchase line classification
+-- Created: 2026-04-12
+
+-- Link supplier invoices to cases for procurement workflow
+ALTER TABLE supplier_invoices
+ADD COLUMN IF NOT EXISTS sag_id INTEGER REFERENCES sag_sager(id) ON DELETE SET NULL;
+
+CREATE INDEX IF NOT EXISTS idx_supplier_invoices_sag_id
+ON supplier_invoices(sag_id);
+
+-- Add explicit purchase line classification + invoice traceability on case purchase lines
+ALTER TABLE sag_salgsvarer
+ADD COLUMN IF NOT EXISTS purchase_purpose VARCHAR(50),
+ADD COLUMN IF NOT EXISTS supplier_invoice_id INTEGER REFERENCES supplier_invoices(id) ON DELETE SET NULL,
+ADD COLUMN IF NOT EXISTS supplier_invoice_line_id INTEGER REFERENCES supplier_invoice_lines(id) ON DELETE SET NULL;
+
+DO $$
+BEGIN
+    IF NOT EXISTS (
+        SELECT 1
+        FROM pg_constraint
+        WHERE conname = 'chk_sag_salgsvarer_purchase_purpose'
+    ) THEN
+        ALTER TABLE sag_salgsvarer
+        ADD CONSTRAINT chk_sag_salgsvarer_purchase_purpose
+        CHECK (
+            purchase_purpose IS NULL
+            OR purchase_purpose IN (
+                'salg',
+                'lager',
+                'asset',
+                'intern_brug',
+                'retur_reklamation',
+                'projekt_omkostning'
+            )
+        );
+    END IF;
+END $$;
+
+CREATE INDEX IF NOT EXISTS idx_sag_salgsvarer_purchase_purpose
+ON sag_salgsvarer(purchase_purpose);
+
+CREATE INDEX IF NOT EXISTS idx_sag_salgsvarer_supplier_invoice_id
+ON sag_salgsvarer(supplier_invoice_id);
+
+CREATE INDEX IF NOT EXISTS idx_sag_salgsvarer_supplier_invoice_line_id
+ON sag_salgsvarer(supplier_invoice_line_id);