Merge pull request 'feature/balance_by_item' (#220) from feature/balance_by_item into development

Reviewed-on: ADUANASOFT/anexo76#220

backend/api/v1/modules/a76/clients_and_providers/service.py

@@ -185,6 +185,7 @@ class ClientProviderService:
                     db_address = ClientProviderAddress(
                         client_id=client.id,
                         tenant_id=tenant_id,
+                        company_id=company_id,
                         **client_data.address.model_dump(exclude_unset=True),
                     )
                     db.add(db_address)
@@ -199,6 +200,7 @@ class ClientProviderService:
                     db_programs = ClientProviderPrograms(
                         client_id=client.id,
                         tenant_id=tenant_id,
+                        company_id=company_id,
                         **client_data.programs.model_dump(exclude_unset=True),
                     )
                     db.add(db_programs)

backend/api/v1/modules/a76/invoices/exports/process/main_process.py

@@ -46,7 +46,7 @@ def _process_with_discharge(
     AFIJO, DONAC, SCRAP, REEXP, VEMEX.
     """
     assign_no_discharges_series(db, lines, errors)
-    review_class(db, invoice, lines, invoice.tenant_id, invoice.company_id, errors)
+    review_class(db, lines, errors)
     review_exchange_rate(db, invoice, errors)
     assign_values(db, invoice, lines, invoice.tenant_id, invoice.company_id, errors)
 
@@ -201,4 +201,4 @@ def main_process(db: Session, invoice: InvoiceHeader, tenant_id: str, company_id
     # invoice.status and totals are set inside finalize_invoice_no_discharge / termina_ac_o_lp_normal
     db.flush()
 
-    return {"status": "ok", "invoice_id": str(invoice.id)}
+    return {"status": "success", "invoice_id": str(invoice.id)}

backend/api/v1/modules/a76/invoices/exports/process/pre_validators.py

@@ -1,5 +1,5 @@
 from sqlalchemy import func
-from sqlalchemy.orm import Session
+from sqlalchemy.orm import Session, joinedload
 from api.v1.modules.a76.invoices.models import InvoiceHeader, InvoiceStatus
 from api.v1.modules.a76.items.models import LineItem
 from api.v1.modules.a76.general_catalogs.fractions.warning_fractions.models import WarningFraction
@@ -47,7 +47,7 @@ def pre_validators(db: Session, invoice: InvoiceHeader, tenant_id: str, company_
                 code="NOT_FOUND",
                 value=invoice.compliance_mx.shipped_to_id,
             )
-        if not shipped_to_exists.address.country:
+        if not shipped_to_exists.address or not shipped_to_exists.address.country:
             errors.add_error(
                 field="compliance_mx.shipped_to_id",
                 message="El Destinatario no tiene capturado el pais.",
@@ -100,11 +100,16 @@ def pre_validators(db: Session, invoice: InvoiceHeader, tenant_id: str, company_
         )
         
     # Advertencias para las fracciones y su horario
-    lines = db.query(LineItem).filter(
-        LineItem.invoice_id == invoice.id,
-        LineItem.tenant_id == tenant_id,
-        LineItem.company_id == company_id,
-    ).all()
+    lines = (
+        db.query(LineItem)
+        .options(joinedload(LineItem.fa_data))
+        .filter(
+            LineItem.invoice_id == invoice.id,
+            LineItem.tenant_id == tenant_id,
+            LineItem.company_id == company_id,
+        )
+        .all()
+    )
                 
     return lines
     

backend/api/v1/modules/a76/invoices/exports/process/sub_process/compare_balances.py

@@ -139,6 +139,7 @@ def compare_balances(
 
             entry.quantity_used  += consume
             lot.available_qty    -= consume
+            lot.consumed_qty     += consume
 
         # ── Check if the entry was fully satisfied ────────────────────────────
         if entry.quantity_used < entry.quantity:

backend/api/v1/modules/a76/invoices/exports/process/sub_process/discharge_types.py

@@ -21,7 +21,11 @@ class AvailableLot:
     import_item_line_id : a76.item_lines.id of the import line (the lot)
     import_invoice_id   : a76.invoice_header.id of the import invoice
     part_number_id      : denormalized from the import line
-    available_qty       : net balance available  (QSaldo:Cantidad)
+    available_qty       : net balance available  (QSaldo:Cantidad); mutated by
+                          compare_balances() as quantity is distributed
+    consumed_qty        : how much was actually taken from this lot by
+                          compare_balances(); used by register_discharge_ledger
+                          to create the exact BalanceMovement amount
     value_me            : USD value of the full lot (for proportional calc)
     value_mn            : MXN value of the full lot (for proportional calc)
     order_peps          : PEPS ordering key — lower = older = consumed first
@@ -33,6 +37,7 @@ class AvailableLot:
     value_me: Optional[Decimal]
     value_mn: Optional[Decimal]
     order_peps: int
+    consumed_qty: Decimal = field(default_factory=Decimal)
 
 
 @dataclass

backend/api/v1/modules/a76/invoices/exports/process/sub_process/download_balance_collector.py

@@ -66,7 +66,7 @@ def collect_lines_to_discharge(
     """
     to_discharge: List[DownloadEntry] = []
 
-    discharge_lines = [line for line in lines if line.discharge]
+    discharge_lines = [line for line in lines if line.fa_data and line.fa_data.discharge]
 
     if not discharge_lines:
         return to_discharge

backend/api/v1/modules/a76/invoices/exports/process/sub_process/fill_available_balances.py

@@ -200,7 +200,7 @@ def fill_available_balances(
             continue
 
         # Status 'NA' == not processed (Clarion: Estatus = 'NA')
-        if import_invoice.status == InvoiceStatus.UNPROCESSED:
+        if import_invoice.status == InvoiceStatus.PENDING:
             errors.add_error(
                 field=f"line[{entry.export_line}].import_invoice",
                 message=f"La Factura de Importación: '{entry.import_invoice}' está Desactualizada.",

backend/api/v1/modules/a76/invoices/exports/process/sub_process/finalize_invoice.py

@@ -23,6 +23,7 @@ from sqlalchemy.orm import Session
 
 from .register_import_discharge import register_import_discharge
 from .register_discharge_series import register_discharge_series
+from .register_discharge_ledger import register_discharge_ledger
 
 if TYPE_CHECKING:
     from .discharge_types import DownloadEntry
@@ -274,6 +275,9 @@ def finalize_invoice_with_discharge(
             generate_definitive_import(db, invoice, errors)
 
         if to_discharge:
+            # Write BalanceMovement (CONSUMPTION) + DischargeHeader + DischargeDetail
+            register_discharge_ledger(db, invoice, to_discharge)
+            # Update quantity_returned / value_returned on the import lines
             register_import_discharge(db, invoice, to_discharge)
             register_discharge_series(db, invoice, to_discharge)
 

backend/api/v1/modules/a76/invoices/exports/process/sub_process/register_discharge_ledger.py

@@ -0,0 +1,239 @@
+"""
+register_discharge_ledger
+=========================
+Creates the full Annex-24 discharge record for one export invoice:
+
+  1. ONE  DischargeHeader  (one per export event)
+  2. N    BalanceMovement   rows (type=CONSUMPTION, one per lot consumed)
+  3. N    DischargeDetail   rows (one per export-line × import-lot pair),
+         each referencing its BalanceMovement (design rule 3)
+
+Design rules from a24.balance_movement (preserved here):
+  1. NEVER update existing balance_movement rows — only INSERT.
+  2. Balance = SUM of movements.
+  3. Every DischargeDetail.movement_id MUST reference a BalanceMovement row.
+  4. order_peps = movement.id  (set after flush, globally monotonic).
+"""
+
+import datetime
+import logging
+from decimal import Decimal
+from typing import List, Optional
+
+from sqlalchemy.orm import Session
+
+from api.v1.modules.a76.invoices.models import InvoiceHeader
+from api.v1.modules.a24.balance_movements.models import BalanceMovement, MovementType
+from api.v1.modules.a24.discharges.models import (
+    DischargeDetail,
+    DischargeHeader,
+    DischargeStatus,
+    DischargeType,
+)
+from api.v1.modules.a76.invoices.models import InvoiceHeader as A76InvoiceHeader
+from api.v1.modules.a76.items.models import LineItem
+from .discharge_types import DownloadEntry, AvailableLot
+
+logger = logging.getLogger(__name__)
+
+
+# ---------------------------------------------------------------------------
+# Helpers
+# ---------------------------------------------------------------------------
+
+def _discharge_type_for_invoice(invoice: InvoiceHeader) -> DischargeType:
+    mapping = {
+        "AFIJO": DischargeType.TEMPORARY,
+        "DONAC": DischargeType.TEMPORARY,
+        "SCRAP": DischargeType.WASTE_SCRAP,
+        "REEXP": DischargeType.DEFINITIVE,
+        "VEMEX": DischargeType.DEFINITIVE,
+    }
+    return mapping.get(invoice.invoice_type or "", DischargeType.TEMPORARY)
+
+
+def _export_date(invoice: InvoiceHeader) -> datetime.date:
+    d = invoice.invoice_date
+    return d.date() if hasattr(d, "date") else d
+
+
+def _proportional_value(
+    consume: Decimal,
+    lot_consumed_total: Decimal,
+    lot_value: Optional[Decimal],
+) -> Optional[Decimal]:
+    """Returns the proportional value for *consume* units out of *lot_consumed_total*."""
+    if not lot_value or lot_consumed_total <= 0:
+        return None
+    return (consume / lot_consumed_total) * lot_value
+
+
+def _proportional_qty(consume: Decimal, base_qty: Optional[Decimal], base_total: Optional[Decimal]) -> Optional[Decimal]:
+    """
+    Proratea un valor (peso/valor) en proporción a lo consumido.
+    - consume: cantidad consumida del lote
+    - base_qty: valor total del lote (ej. peso neto total del lote)
+    - base_total: cantidad total del lote (ej. quantity del lote)
+    """
+    if base_qty is None:
+        return None
+    if base_total is None or base_total <= 0:
+        return None
+    return (consume / base_total) * base_qty
+
+
+# ---------------------------------------------------------------------------
+# Public entry point
+# ---------------------------------------------------------------------------
+
+def register_discharge_ledger(
+    db: Session,
+    export_invoice: InvoiceHeader,
+    to_discharge: List[DownloadEntry],
+) -> Optional[DischargeHeader]:
+    """
+    Persists the complete Annex-24 discharge record for *export_invoice*.
+
+    Expects that compare_balances() has already run and populated
+    ``lot.consumed_qty`` for every lot that was drawn from.
+
+    Returns the created DischargeHeader, or None if nothing was discharged.
+    """
+    # Only process entries that actually consumed something
+    active = [e for e in to_discharge if e.quantity_used > Decimal(0)]
+    if not active:
+        return None
+
+    op_date = _export_date(export_invoice)
+    discharge_type = _discharge_type_for_invoice(export_invoice)
+
+    # Caches to avoid N+1 queries in loops
+    export_line_cache: dict[int, LineItem] = {}
+    import_line_cache: dict[int, LineItem] = {}
+    import_invoice_number_cache: dict[int, str] = {}
+
+    # ── 1. DischargeHeader ────────────────────────────────────────────────
+    header = DischargeHeader(
+        tenant_id=export_invoice.tenant_id,
+        company_id=export_invoice.company_id,
+        source_invoice_id=export_invoice.id,
+        discharge_type=discharge_type,
+        status=DischargeStatus.APPLIED,
+        discharge_date=op_date,
+    )
+    db.add(header)
+    db.flush()  # get header.id
+
+    total_movements = 0
+
+    for entry in active:
+        export_line_id: Optional[int] = entry.line_item_id
+
+        export_line_obj: Optional[LineItem] = None
+        if export_line_id:
+            export_line_obj = export_line_cache.get(export_line_id)
+            if export_line_obj is None:
+                export_line_obj = db.get(LineItem, export_line_id)
+                if export_line_obj is not None:
+                    export_line_cache[export_line_id] = export_line_obj
+
+        # Only iterate lots that were actually consumed
+        consumed_lots: List[AvailableLot] = [
+            lot for lot in entry.available_lots if lot.consumed_qty > Decimal(0)
+        ]
+
+        for lot in consumed_lots:
+            consume = lot.consumed_qty
+
+            # Load import-line object for denormalized customs/weights fields
+            import_line_obj = import_line_cache.get(lot.import_item_line_id)
+            if import_line_obj is None:
+                import_line_obj = db.get(LineItem, lot.import_item_line_id)
+                if import_line_obj is not None:
+                    import_line_cache[lot.import_item_line_id] = import_line_obj
+
+            # Import invoice number (for origin_import_invoice in DischargeDetail)
+            origin_import_invoice: Optional[str] = None
+            if lot.import_invoice_id:
+                origin_import_invoice = import_invoice_number_cache.get(lot.import_invoice_id)
+                if origin_import_invoice is None:
+                    inv = db.get(A76InvoiceHeader, lot.import_invoice_id)
+                    origin_import_invoice = inv.invoice_number if inv else None
+                    if origin_import_invoice:
+                        import_invoice_number_cache[lot.import_invoice_id] = origin_import_invoice
+
+            # ── 2. BalanceMovement (CONSUMPTION) ──────────────────────────
+            # Proportional value: consume / lot_consumed_total × lot_value
+            # lot_consumed_total == consume for single-lot entries (most cases)
+            value_me = _proportional_value(consume, consume, lot.value_me)
+            value_mn = _proportional_value(consume, consume, lot.value_mn)
+
+            movement = BalanceMovement(
+                tenant_id=export_invoice.tenant_id,
+                company_id=export_invoice.company_id,
+                import_invoice_id=lot.import_invoice_id,
+                import_item_line_id=lot.import_item_line_id,
+                part_number_id=lot.part_number_id,
+                movement_type=MovementType.CONSUMPTION,
+                quantity=consume,
+                value_me=value_me,
+                value_mn=value_mn,
+                source_invoice_id=export_invoice.id,
+                source_item_line_id=export_line_id,
+                order_peps=0,   # placeholder — set after flush (rule 4)
+                operation_date=op_date,
+                notes=(
+                    f"Descarga por factura de exportación "
+                    f"{export_invoice.invoice_number}"
+                ),
+            )
+            db.add(movement)
+            db.flush()  # get movement.id
+            movement.order_peps = movement.id  # rule 4: monotonic
+
+            # ── 3. DischargeDetail ─────────────────────────────────────────
+            # Denormalized fields expected by reports:
+            imp_cust = import_line_obj.customs if import_line_obj else None
+            imp_qty = import_line_obj.quantity if import_line_obj else None
+            imp_total_qty = imp_qty.quantity if imp_qty else None
+
+            net_weight = _proportional_qty(consume, imp_qty.net_weight if imp_qty else None, imp_total_qty)
+            gross_weight = _proportional_qty(consume, imp_qty.gross_weight if imp_qty else None, imp_total_qty)
+
+            detail = DischargeDetail(
+                tenant_id=export_invoice.tenant_id,
+                company_id=export_invoice.company_id,
+                discharge_header_id=header.id,
+                export_item_line_id=export_line_id,
+                import_item_line_id=lot.import_item_line_id,
+                movement_id=movement.id,
+                quantity_discharged=consume,
+                unit_of_measure=entry.unit_of_measure or None,
+                value_me=value_me,
+                value_mn=value_mn,
+                net_weight=net_weight,
+                gross_weight=gross_weight,
+                tariff_fraction=imp_cust.fraction if imp_cust else None,
+                fraction_type=imp_cust.fraction_type if imp_cust else None,
+                ad_valorem=imp_cust.advalorem if imp_cust else None,
+                country_of_origin=imp_cust.origin_country if imp_cust else None,
+                sector=imp_cust.sector if imp_cust else None,
+                procedence=entry.origin_procedure or None,
+                part_number=entry.part_number or None,
+                export_part_number=(
+                    export_line_obj.part_info.part_number
+                    if export_line_obj and export_line_obj.part_info and export_line_obj.part_info.part_number
+                    else None
+                ),
+                origin_import_invoice=origin_import_invoice,
+            )
+            db.add(detail)
+            total_movements += 1
+
+    logger.info(
+        "register_discharge_ledger: invoice=%s header_id=%s details=%d",
+        export_invoice.invoice_number,
+        header.id,
+        total_movements,
+    )
+    return header

backend/api/v1/modules/a76/items/models.py

@@ -24,7 +24,10 @@ if TYPE_CHECKING:
     from api.v1.modules.a24.fa.fa_item_lines.models import FaLineItem
     from api.v1.modules.a76.parts.models import Part
     from api.v1.modules.a76.invoices.models import InvoiceHeader
-    from api.v1.modules.a76.general_catalogs.identifiers.models import IdentifierDetail
+
+# Imported at runtime so SQLAlchemy's mapper registry can resolve the class name
+# used in the relationship string below.
+from api.v1.modules.a76.general_catalogs.identifiers.models import IdentifierDetail
 
 # ============================================================================
 # CORE ENTITIES

backend/api/v1/modules/a76/items/routes.py

@@ -3,7 +3,8 @@ API Endpoints for Items management
 Handles CRUD operations for Item with one-to-many relationships to LineItems
 """
 
-from typing import Dict, Any, Optional
+import datetime
+from typing import Dict, Any, List, Optional
 from fastapi import APIRouter, Depends, HTTPException, Query, Path, status
 from sqlalchemy.orm import Session
 
@@ -191,6 +192,39 @@ async def get_items_by_invoice(
         skip=skip,
         limit=limit
     )
+@router.get("/invoice/{invoice_id}/items-with-balance", response_model=List[dict])
+async def get_items_with_balance(
+    invoice_id: int = Path(..., description="Import Invoice ID"),
+    company_id: int = Query(..., description="Company ID"),
+    as_of_date: Optional[datetime.date] = Query(
+        None,
+        description=(
+            "Cut-off date for balance calculation.  Only consumptions on or "
+            "before this date are subtracted (CALCULA_SALDO_FECHA_EXPO logic)."
+        ),
+    ),
+    db: Session = Depends(get_core_db),
+    current_user: Dict[str, Any] = Depends(get_current_user),
+):
+    """
+    Returns every line of the given import invoice with its available balance
+    from the a24.balance_movement ledger.
+
+    Each item in the response includes:
+    - id, line_number, part_number, class_code, unit_of_measure_code
+    - quantity        : original imported quantity
+    - available_balance : net balance still available for export discharge
+    - has_balance     : true when available_balance > 0
+
+    Use ``as_of_date`` to restrict consumption movements to a specific date
+    (pass the export invoice date so that future discharges are not counted).
+    """
+    tenant_id = validate_access_to_resource(db, company_id, current_user)
+    service = ItemService()
+    return service.get_lines_with_balance(db, invoice_id, tenant_id, company_id, as_of_date)
+
+
+# ============================================================================
 # STATISTICS & UTILITIES
 # ============================================================================
 

backend/api/v1/modules/a76/items/service.py

@@ -12,10 +12,12 @@ After refactoring: LineItem is the main entity, representing a single line item
 There is no intermediate Item entity anymore. Each LineItem belongs directly to an InvoiceHeader.
 """
 
+import datetime
 import logging
+from decimal import Decimal
 from typing import Optional, List, Tuple
 from fastapi import HTTPException
-from sqlalchemy import and_, or_
+from sqlalchemy import and_, case, func, or_, select
 from sqlalchemy.exc import IntegrityError
 from sqlalchemy.orm import Session, joinedload
 
@@ -41,6 +43,7 @@ from .series.models import Serie
 from api.v1.modules.a76.invoices.models import InvoiceHeader
 from api.v1.modules.a76.parts.models import Part
 from api.v1.modules.a76.general_catalogs.identifiers.models import IdentifierDetail
+from api.v1.modules.a24.balance_movements.models import BalanceMovement, NEGATIVE_MOVEMENTS
 
 logger = logging.getLogger(__name__)
 
@@ -372,10 +375,11 @@ class ItemService:
             errors.raise_if_errors("Error al crear el item - invoice_id es requerido")
 
         invoice = invoice_exists_by_id(
-            db, item_data.invoice_id, tenant_id, company_id, errors
+            db, item_data.invoice_id, tenant_id, company_id, None
         )
 
         if not invoice:
+            errors.add_error("invoice_id", "La factura no existe", code="NOT_FOUND", value=str(item_data.invoice_id))
             errors.raise_if_errors("Error al encontra la factura para el item")
         if not invoice_processed(db, item_data.invoice_id, tenant_id, company_id, errors):
             errors.raise_if_errors("Error al crear el item - la factura ya fue actualizada, no se pueden agregar items")
@@ -511,9 +515,10 @@ class ItemService:
         errors = ErrorCollector()
 
         invoice = invoice_exists_by_id(
-            db, item_data.invoice_id, tenant_id, company_id, errors
+            db, item_data.invoice_id, tenant_id, company_id, None
         )
         if not invoice:
+            errors.add_error("invoice_id", "La factura no existe", code="NOT_FOUND", value=str(item_data.invoice_id))
             errors.raise_if_errors("Error al encontra la factura para el item")
 
         # Lock invoice
@@ -684,3 +689,125 @@ class ItemService:
             db.rollback()
             logger.error(f"Error deleting item: {e}")
             raise HTTPException(status_code=500, detail="Error deleting item")
+
+    @staticmethod
+    def get_lines_with_balance(
+        db: Session,
+        invoice_id: int,
+        tenant_id: int,
+        company_id: int,
+        as_of_date: Optional[datetime.date] = None,
+    ) -> List[dict]:
+        """
+        Returns every line of an import invoice together with its current
+        available balance calculated from the a24.balance_movement ledger.
+
+        Lines with balance <= 0 are included but marked as unavailable so
+        the frontend can grey them out / disable them.
+
+        Parameters
+        ----------
+        as_of_date : optional cut-off date.  Only negative movements
+                     (consumptions, etc.) on or before this date are counted,
+                     mirroring the CALCULA_SALDO_FECHA_EXPO Clarion logic.
+                     If None, all movements are counted (no date restriction).
+        """
+        lines: List[LineItem] = (
+            db.query(LineItem)
+            .filter(
+                LineItem.invoice_id == invoice_id,
+                LineItem.tenant_id == tenant_id,
+                LineItem.company_id == company_id,
+            )
+            .options(
+                joinedload(LineItem.quantity),
+                joinedload(LineItem.description),
+                joinedload(LineItem.part_info),
+                joinedload(LineItem.class_info),
+                joinedload(LineItem.unit_of_measure_info),
+                joinedload(LineItem.fa_data),
+                joinedload(LineItem.invoice),
+            )
+            .order_by(LineItem.line_number)
+            .all()
+        )
+
+        result = []
+        for line in lines:
+            available_balance = ItemService._compute_balance(db, line.id, as_of_date)
+            qty = line.quantity
+            desc = line.description
+            fa = line.fa_data
+            inv = line.invoice
+
+            # Count subitems (lines that reference this line as parent via subitem_number)
+            subitem_count = 0
+            if fa and fa.contains_subitems:
+                from api.v1.modules.a24.fa.fa_item_lines.models import FaLineItem as FaModel
+                subitem_count = (
+                    db.query(func.count(LineItem.id))
+                    .join(FaModel, FaModel.id == LineItem.id)
+                    .filter(
+                        LineItem.invoice_id == invoice_id,
+                        LineItem.tenant_id == tenant_id,
+                        FaModel.is_subitem == True,
+                        FaModel.subitem_number == line.line_number,
+                    )
+                    .scalar() or 0
+                )
+
+            result.append({
+                "id": line.id,
+                "line_number": line.line_number,
+                # Invoice info
+                "invoice_number": inv.invoice_number if inv else None,
+                "invoice_date": inv.invoice_date.isoformat() if inv and inv.invoice_date else None,
+                "invoice_status": inv.status if inv and inv.status else None,
+                # Part / class
+                "part_number": line.part_info.part_number if line.part_info else None,
+                "class_code": line.class_info.class_code if line.class_info else None,
+                "description_spanish": desc.description_spanish if desc else None,
+                "unit_of_measure_code": line.unit_of_measure_info.code if line.unit_of_measure_info else None,
+                # Quantities
+                "quantity": float(qty.quantity) if qty and qty.quantity is not None else None,
+                "quantity_returned_temp": float(qty.quantity_returned_temp) if qty and qty.quantity_returned_temp is not None else None,
+                "quantity_returned": float(qty.quantity_returned) if qty and qty.quantity_returned is not None else None,
+                # Balance
+                "available_balance": float(available_balance),
+                "has_balance": available_balance > Decimal(0),
+                # FA / subitem info
+                "is_subitem": fa.is_subitem if fa else None,
+                "contains_subitems": fa.contains_subitems if fa else None,
+                "subitem_count": subitem_count,
+            })
+        return result
+
+    @staticmethod
+    def _compute_balance(
+        db: Session,
+        item_line_id: int,
+        as_of_date: Optional[datetime.date],
+    ) -> Decimal:
+        """Net available balance for one import line from the ledger."""
+        sign_expr = case(
+            (BalanceMovement.movement_type.in_(NEGATIVE_MOVEMENTS), Decimal(-1)),
+            else_=Decimal(1),
+        )
+        if as_of_date is not None:
+            date_filter = case(
+                (
+                    BalanceMovement.movement_type.in_(NEGATIVE_MOVEMENTS),
+                    BalanceMovement.operation_date <= as_of_date,
+                ),
+                else_=True,
+            )
+        else:
+            date_filter = True  # type: ignore[assignment]
+
+        result = db.execute(
+            select(func.sum(sign_expr * BalanceMovement.quantity)).where(
+                BalanceMovement.import_item_line_id == item_line_id,
+                date_filter,
+            )
+        ).scalar()
+        return Decimal(str(result or 0))

backend/core/celery_app.py

@@ -64,6 +64,7 @@ celery_app.conf.update(
         "api.v1.modules.core.help_center.tasks",
         "api.v1.modules.a76.invoices.imports.process.task",
         "api.v1.modules.a76.invoices.imports.revert.task",
+        "api.v1.modules.a76.invoices.exports.process.task",
     ]  # Ruta al módulo donde están las tareas
 )
 

frontend/src/lib/api/dashboard/a76/items.ts

@@ -299,5 +299,52 @@ export const itemsApi = {
             company_id: companyId.toString()
         });
         return api.delete(`/v1/a76/items/${itemId}/?${params.toString()}`);
+    },
+
+    /**
+     * Lista las líneas de una factura de importación con su saldo disponible.
+     * Solo las líneas con has_balance = true tienen mercancía disponible para descarga.
+     *
+     * @param invoiceId  - ID de la factura de importación
+     * @param companyId  - ID de la empresa
+     * @param asOfDate   - Fecha corte opcional (ISO: "YYYY-MM-DD").
+     *                     Pasa la fecha de la factura de exportación para que
+     *                     los consumos futuros no se descuenten del saldo.
+     */
+    listByInvoiceWithBalance: (
+        invoiceId: number,
+        companyId: number,
+        asOfDate?: string
+    ) => {
+        const params = new URLSearchParams({ company_id: companyId.toString() });
+        if (asOfDate) params.append('as_of_date', asOfDate);
+        return api.get<ImportLineWithBalance[]>(
+            `/v1/a76/items/invoice/${invoiceId}/items-with-balance?${params.toString()}`
+        );
     }
 };
+
+export interface ImportLineWithBalance {
+    id: number;
+    line_number: number;
+    // Invoice info
+    invoice_number?: string;
+    invoice_date?: string;
+    invoice_status?: string;
+    // Part / class
+    part_number?: string;
+    class_code?: string;
+    description_spanish?: string;
+    unit_of_measure_code?: string;
+    // Quantities
+    quantity?: number;
+    quantity_returned_temp?: number;
+    quantity_returned?: number;
+    // Balance
+    available_balance: number;
+    has_balance: boolean;
+    // FA / subitem
+    is_subitem?: boolean;
+    contains_subitems?: boolean;
+    subitem_count?: number;
+}

frontend/src/lib/components/dashboard/invoices/edit/InvoiceSelectorModal.svelte

@@ -7,17 +7,19 @@
 	import { companyStore } from '$lib/stores/company.svelte';
 	import { toast } from 'svelte-sonner';
 
+	interface Props {
+		open: boolean;
+		regimen?: string;
+		operationType?: 'imp' | 'exp';
+		onSelect: (invoice: Invoice) => void;
+	}
+
 	let {
 		open = $bindable(false),
 		regimen = 'Temporal',
 		operationType = 'imp' as 'imp' | 'exp',
 		onSelect
-	}: {
-		open: boolean;
-		regimen?: string;
-		operationType?: 'imp' | 'exp';
-		onSelect: (invoice: Invoice) => void;
-	} = $props();
+	}: Props = $props();
 
 	let invoices = $state<Invoice[]>([]);
 	let loading = $state(false);

frontend/src/lib/components/dashboard/invoices/edit/items/fa/item-sheet-fa.svelte

@@ -11,7 +11,7 @@
     import { Loader2, Package, Save, X, FileText, Folder } from 'lucide-svelte';
     import type { Invoice } from '$lib/api/dashboard/a76/invoices';
     import { invoicesApi } from '$lib/api/dashboard/a76/invoices';
-    import { itemsApi, type Item } from '$lib/api/dashboard/a76/items';
+    import { itemsApi, type Item, type ImportLineWithBalance } from '$lib/api/dashboard/a76/items';
     import { companyStore } from '$lib/stores/company.svelte';
     
     // Child components
@@ -68,6 +68,9 @@
             if (editingItem.fa_data.omit_annex31 === undefined) {
                 editingItem.fa_data.omit_annex31 = false;
             }
+            if (editingItem.fa_data.discharge === undefined) {
+                editingItem.fa_data.discharge = false;
+            }
         }
     });
 
@@ -78,7 +81,7 @@
     let showImportLinePicker = $state(false);
     let selectedImportInvoiceId = $state<number | null>(null);
     let selectedExportInvoiceId = $state<number | null>(null);
-    let importInvoiceLines = $state<Item[]>([]);
+    let importInvoiceLines = $state<ImportLineWithBalance[]>([]);
     let exportInvoiceLines = $state<Item[]>([]);
     let loadingImportLines = $state(false);
     let loadingExportLines = $state(false);
@@ -88,8 +91,13 @@
         if (!companyId) return;
         loadingImportLines = true;
         try {
-            const res = await itemsApi.listByInvoice(invoiceId, companyId);
-            importInvoiceLines = res.data?.items ?? [];
+            // Pass the export invoice date so consumption movements after that
+            // date are not subtracted from the available balance.
+            const asOfDate = invoice?.invoice_date
+                ? invoice.invoice_date.split('T')[0]
+                : undefined;
+            const res = await itemsApi.listByInvoiceWithBalance(invoiceId, companyId, asOfDate);
+            importInvoiceLines = res.data ?? [];
         } catch {
             importInvoiceLines = [];
         } finally {
@@ -334,7 +342,7 @@
                                         value={editingItem.fa_data?.search_type || ''}
                                         onValueChange={(v) => {
                                             editingItem.fa_data = editingItem.fa_data || {};
-                                            editingItem.fa_data.search_type = v ?? undefined;
+                                            editingItem.fa_data.search_type = v ?? 'Factura';
                                         }}
                                     >
                                         <Select.Trigger id="fa_rep_search_type" class="h-8 text-sm">
@@ -345,6 +353,7 @@
                                         <Select.Content>
                                             <Select.Item value="Factura">Factura</Select.Item>
                                             <Select.Item value="NumParte">NumParte</Select.Item>
+                                            <Select.Item value="Clase">Clase</Select.Item>
                                         </Select.Content>
                                     </Select.Root>
                                 </div>
@@ -630,25 +639,111 @@
 
 <!-- Diálogo para elegir línea (Impo) -->
 <Dialog.Root bind:open={showImportLinePicker}>
-    <Dialog.Content class="max-w-sm">
+    <Dialog.Content class="max-w-4xl">
         <Dialog.Header>
-            <Dialog.Title class="text-sm">Seleccionar línea</Dialog.Title>
+            <Dialog.Title class="text-sm">Seleccionar línea de importación</Dialog.Title>
+            <p class="text-xs text-muted-foreground mt-0.5">
+                Solo se muestran líneas con saldo disponible
+            </p>
         </Dialog.Header>
-        <div class="max-h-[280px] overflow-y-auto py-2">
-            {#each importInvoiceLines as lineItem}
-                {@const num = lineItem.line_number ?? lineItem.id}
-                <button
-                    type="button"
-                    class="w-full px-3 py-2 text-left text-sm hover:bg-muted rounded-md"
-                    onclick={() => {
-                        editingItem.fa_data = editingItem.fa_data || {};
-                        editingItem.fa_data.search_line = typeof num === 'number' ? num : undefined;
-                        showImportLinePicker = false;
-                    }}
-                >
-                    Línea {num}
-                </button>
-            {/each}
+        <!-- overflow-x on a wrapper that does NOT also do overflow-y.
+             The inner div handles vertical scroll so sticky columns work
+             independently from the horizontal scrollbar. -->
+        <div class="overflow-x-auto">
+            <div class="overflow-y-auto max-h-[500px]">
+            {#if importInvoiceLines.every(l => !l.has_balance)}
+                <p class="px-3 py-8 text-xs text-muted-foreground text-center">
+                    No hay líneas con saldo disponible en esta factura.
+                </p>
+            {:else}
+                <table class="text-xs border-collapse" style="min-width: max-content; width: 100%;">
+                    <thead class="sticky top-0 z-20">
+                        <tr class="border-b border-border bg-muted">
+                            <!-- sticky cols 1-3: left offsets match td widths below -->
+                            <th class="sticky left-0 z-20 bg-muted px-2 py-2 text-left font-semibold text-muted-foreground whitespace-nowrap w-[48px]">Línea</th>
+                            <th class="sticky left-[48px] z-20 bg-muted px-2 py-2 text-left font-semibold text-muted-foreground whitespace-nowrap w-[120px]">Factura</th>
+                            <th class="sticky left-[168px] z-20 bg-muted px-2 py-2 text-left font-semibold text-muted-foreground whitespace-nowrap w-[88px]">Fecha</th>
+                            <th class="px-2 py-2 text-left font-semibold text-muted-foreground whitespace-nowrap">Num. Parte</th>
+                            <th class="px-2 py-2 text-left font-semibold text-muted-foreground whitespace-nowrap">Clase</th>
+                            <th class="px-2 py-2 text-left font-semibold text-muted-foreground whitespace-nowrap w-[180px]">Descripción</th>
+                            <th class="px-2 py-2 text-right font-semibold text-muted-foreground whitespace-nowrap">Cant. Imp.</th>
+                            <th class="px-2 py-2 text-right font-semibold text-muted-foreground whitespace-nowrap">Ret. Temp.</th>
+                            <th class="px-2 py-2 text-right font-semibold text-muted-foreground whitespace-nowrap">Ret. Def.</th>
+                            <th class="px-2 py-2 text-right font-semibold text-muted-foreground whitespace-nowrap">Saldo Disp.</th>
+                            <th class="px-2 py-2 text-center font-semibold text-muted-foreground whitespace-nowrap">Estatus</th>
+                            <th class="px-2 py-2 text-center font-semibold text-muted-foreground whitespace-nowrap">Sub.</th>
+                        </tr>
+                    </thead>
+                    <tbody class="divide-y divide-border">
+                        {#each importInvoiceLines as lineItem}
+                            {#if lineItem.has_balance}
+                                <tr
+                                    class="hover:bg-muted/50 cursor-pointer transition-colors group"
+                                    onclick={() => {
+                                        editingItem.fa_data = editingItem.fa_data || {};
+                                        editingItem.fa_data.search_line = lineItem.line_number;
+                                        showImportLinePicker = false;
+                                    }}
+                                >
+                                    <td class="sticky left-0 z-10 bg-background group-hover:bg-muted/50 px-2 py-1.5 font-semibold text-primary whitespace-nowrap w-[48px]">{lineItem.line_number}</td>
+                                    <td class="sticky left-[48px] z-10 bg-background group-hover:bg-muted/50 px-2 py-1.5 font-mono whitespace-nowrap w-[120px]">{lineItem.invoice_number ?? '-'}</td>
+                                    <td class="sticky left-[168px] z-10 bg-background group-hover:bg-muted/50 px-2 py-1.5 text-muted-foreground whitespace-nowrap w-[88px]">
+                                        {lineItem.invoice_date ? lineItem.invoice_date.slice(0, 10) : '-'}
+                                    </td>
+                                    <td class="px-2 py-1.5 font-mono whitespace-nowrap">{lineItem.part_number ?? '-'}</td>
+                                    <td class="px-2 py-1.5 whitespace-nowrap">{lineItem.class_code ?? '-'}</td>
+                                    <td class="px-2 py-1.5 w-[180px] max-w-[180px] truncate text-muted-foreground" title={lineItem.description_spanish ?? ''}>
+                                        {lineItem.description_spanish ?? '-'}
+                                    </td>
+                                    <td class="px-2 py-1.5 text-right tabular-nums whitespace-nowrap">
+                                        {lineItem.quantity != null ? lineItem.quantity.toLocaleString('es-MX', { maximumFractionDigits: 4 }) : '-'}
+                                        <span class="text-muted-foreground">{lineItem.unit_of_measure_code ?? ''}</span>
+                                    </td>
+                                    <td class="px-2 py-1.5 text-right tabular-nums whitespace-nowrap text-amber-600 dark:text-amber-400">
+                                        {lineItem.quantity_returned_temp != null ? lineItem.quantity_returned_temp.toLocaleString('es-MX', { maximumFractionDigits: 4 }) : '-'}
+                                    </td>
+                                    <td class="px-2 py-1.5 text-right tabular-nums whitespace-nowrap text-blue-600 dark:text-blue-400">
+                                        {lineItem.quantity_returned != null ? lineItem.quantity_returned.toLocaleString('es-MX', { maximumFractionDigits: 4 }) : '-'}
+                                    </td>
+                                    <td class="px-2 py-1.5 text-right tabular-nums font-semibold whitespace-nowrap text-emerald-600 dark:text-emerald-400">
+                                        {lineItem.available_balance.toLocaleString('es-MX', { maximumFractionDigits: 4 })}
+                                        <span class="font-normal text-muted-foreground">{lineItem.unit_of_measure_code ?? ''}</span>
+                                    </td>
+                                    <td class="px-2 py-1.5 text-center whitespace-nowrap">
+                                        {#if lineItem.invoice_status === 'processed'}
+                                            <span class="inline-flex items-center rounded-full bg-emerald-100 dark:bg-emerald-900/40 px-1.5 py-0.5 text-[10px] font-medium text-emerald-700 dark:text-emerald-300">
+                                                Procesada
+                                            </span>
+                                        {:else if lineItem.invoice_status === 'reversed'}
+                                            <span class="inline-flex items-center rounded-full bg-red-100 dark:bg-red-900/40 px-1.5 py-0.5 text-[10px] font-medium text-red-700 dark:text-red-300">
+                                                Revertida
+                                            </span>
+                                        {:else}
+                                            <span class="inline-flex items-center rounded-full bg-zinc-100 dark:bg-zinc-800 px-1.5 py-0.5 text-[10px] font-medium text-zinc-600 dark:text-zinc-400">
+                                                {lineItem.invoice_status ?? 'Pendiente'}
+                                            </span>
+                                        {/if}
+                                    </td>
+                                    <td class="px-2 py-1.5 text-center whitespace-nowrap">
+                                        {#if lineItem.is_subitem}
+                                            <span class="inline-flex items-center rounded-full bg-purple-100 dark:bg-purple-900/40 px-1.5 py-0.5 text-[10px] font-medium text-purple-700 dark:text-purple-300">
+                                                Sub
+                                            </span>
+                                        {:else if lineItem.contains_subitems}
+                                            <span class="inline-flex items-center rounded-full bg-indigo-100 dark:bg-indigo-900/40 px-1.5 py-0.5 text-[10px] font-medium text-indigo-700 dark:text-indigo-300" title="{lineItem.subitem_count} subpartida(s)">
+                                                {lineItem.subitem_count ?? 0} sub
+                                            </span>
+                                        {:else}
+                                            <span class="text-muted-foreground">—</span>
+                                        {/if}
+                                    </td>
+                                </tr>
+                            {/if}
+                        {/each}
+                    </tbody>
+                </table>
+            {/if}
+            </div>
         </div>
     </Dialog.Content>
 </Dialog.Root>

frontend/src/lib/components/ui/select/select-root.svelte

@@ -5,11 +5,21 @@
 	import { selectSearchContextKey, type SelectSearchContext } from './select-search-context';
 	import { type WithoutChild } from '$lib/utils.js';
 
+	// SelectPrimitive.RootProps is a discriminated union (single | multiple).
+	// Spreading a discriminated union collapses conflicting members (e.g. onValueChange) to `never`.
+	// We widen the props type so callers can pass either variant without hitting `never`.
+	// eslint-disable-next-line @typescript-eslint/no-explicit-any
+	type SelectRootProps = Omit<WithoutChild<SelectPrimitive.RootProps>, 'value' | 'onValueChange'> & {
+		type?: 'single' | 'multiple';
+		value?: string | string[];
+		onValueChange?: (value: any) => void;
+	};
+
 	let {
 		children,
 		value = $bindable(),
 		...restProps
-	}: WithoutChild<SelectPrimitive.RootProps> = $props();
+	}: SelectRootProps = $props();
 
 	let open = $state(false);
 	const query = writable('');