# app/api/v1/admin/letzshop.py
"""
Admin API endpoints for Letzshop marketplace integration.

Provides admin-level management of:
- Per-vendor Letzshop credentials
- Connection testing
- Sync triggers and status
- Order overview
"""

import logging

from fastapi import APIRouter, Depends, Path, Query
from sqlalchemy.orm import Session

from app.api.deps import get_current_admin_api
from app.core.database import get_db
from app.exceptions import ResourceNotFoundException, ValidationException
from app.services.letzshop import (
    CredentialsNotFoundError,
    LetzshopClientError,
    LetzshopCredentialsService,
    LetzshopOrderService,
    OrderNotFoundError,
    VendorNotFoundError,
)
from models.database.user import User
from models.schema.letzshop import (
    FulfillmentOperationResponse,
    LetzshopConnectionTestRequest,
    LetzshopConnectionTestResponse,
    LetzshopCredentialsCreate,
    LetzshopCredentialsResponse,
    LetzshopCredentialsUpdate,
    LetzshopJobItem,
    LetzshopJobsListResponse,
    LetzshopOrderListResponse,
    LetzshopOrderResponse,
    LetzshopSuccessResponse,
    LetzshopSyncTriggerRequest,
    LetzshopSyncTriggerResponse,
    LetzshopVendorListResponse,
    LetzshopVendorOverview,
)

router = APIRouter(prefix="/letzshop")
logger = logging.getLogger(__name__)


# ============================================================================
# Helper Functions
# ============================================================================


def get_order_service(db: Session) -> LetzshopOrderService:
    """Get order service instance."""
    return LetzshopOrderService(db)


def get_credentials_service(db: Session) -> LetzshopCredentialsService:
    """Get credentials service instance."""
    return LetzshopCredentialsService(db)


# ============================================================================
# Vendor Overview
# ============================================================================


@router.get("/vendors", response_model=LetzshopVendorListResponse)
def list_vendors_letzshop_status(
    skip: int = Query(0, ge=0),
    limit: int = Query(100, ge=1, le=1000),
    configured_only: bool = Query(
        False, description="Only show vendors with Letzshop configured"
    ),
    db: Session = Depends(get_db),
    current_admin: User = Depends(get_current_admin_api),
):
    """
    List all vendors with their Letzshop integration status.

    Shows which vendors have Letzshop configured, sync status, and pending orders.
    """
    order_service = get_order_service(db)
    vendor_overviews, total = order_service.list_vendors_with_letzshop_status(
        skip=skip,
        limit=limit,
        configured_only=configured_only,
    )

    return LetzshopVendorListResponse(
        vendors=[LetzshopVendorOverview(**v) for v in vendor_overviews],
        total=total,
        skip=skip,
        limit=limit,
    )


# ============================================================================
# Credentials Management
# ============================================================================


@router.get(
    "/vendors/{vendor_id}/credentials",
    response_model=LetzshopCredentialsResponse,
)
def get_vendor_credentials(
    vendor_id: int = Path(..., description="Vendor ID"),
    db: Session = Depends(get_db),
    current_admin: User = Depends(get_current_admin_api),
):
    """Get Letzshop credentials for a vendor (API key is masked)."""
    order_service = get_order_service(db)
    creds_service = get_credentials_service(db)

    try:
        vendor = order_service.get_vendor_or_raise(vendor_id)
    except VendorNotFoundError:
        raise ResourceNotFoundException("Vendor", str(vendor_id))

    try:
        credentials = creds_service.get_credentials_or_raise(vendor_id)
    except CredentialsNotFoundError:
        raise ResourceNotFoundException(
            "LetzshopCredentials",
            str(vendor_id),
            message=f"Letzshop credentials not configured for vendor {vendor.name}",
        )

    return LetzshopCredentialsResponse(
        id=credentials.id,
        vendor_id=credentials.vendor_id,
        api_key_masked=creds_service.get_masked_api_key(vendor_id),
        api_endpoint=credentials.api_endpoint,
        auto_sync_enabled=credentials.auto_sync_enabled,
        sync_interval_minutes=credentials.sync_interval_minutes,
        last_sync_at=credentials.last_sync_at,
        last_sync_status=credentials.last_sync_status,
        last_sync_error=credentials.last_sync_error,
        created_at=credentials.created_at,
        updated_at=credentials.updated_at,
    )


@router.post(
    "/vendors/{vendor_id}/credentials",
    response_model=LetzshopCredentialsResponse,
)
def create_or_update_vendor_credentials(
    vendor_id: int = Path(..., description="Vendor ID"),
    credentials_data: LetzshopCredentialsCreate = ...,
    db: Session = Depends(get_db),
    current_admin: User = Depends(get_current_admin_api),
):
    """Create or update Letzshop credentials for a vendor."""
    order_service = get_order_service(db)
    creds_service = get_credentials_service(db)

    try:
        vendor = order_service.get_vendor_or_raise(vendor_id)
    except VendorNotFoundError:
        raise ResourceNotFoundException("Vendor", str(vendor_id))

    credentials = creds_service.upsert_credentials(
        vendor_id=vendor_id,
        api_key=credentials_data.api_key,
        api_endpoint=credentials_data.api_endpoint,
        auto_sync_enabled=credentials_data.auto_sync_enabled,
        sync_interval_minutes=credentials_data.sync_interval_minutes,
    )
    db.commit()

    logger.info(
        f"Admin {current_admin.email} updated Letzshop credentials for vendor {vendor.name}"
    )

    return LetzshopCredentialsResponse(
        id=credentials.id,
        vendor_id=credentials.vendor_id,
        api_key_masked=creds_service.get_masked_api_key(vendor_id),
        api_endpoint=credentials.api_endpoint,
        auto_sync_enabled=credentials.auto_sync_enabled,
        sync_interval_minutes=credentials.sync_interval_minutes,
        last_sync_at=credentials.last_sync_at,
        last_sync_status=credentials.last_sync_status,
        last_sync_error=credentials.last_sync_error,
        created_at=credentials.created_at,
        updated_at=credentials.updated_at,
    )


@router.patch(
    "/vendors/{vendor_id}/credentials",
    response_model=LetzshopCredentialsResponse,
)
def update_vendor_credentials(
    vendor_id: int = Path(..., description="Vendor ID"),
    credentials_data: LetzshopCredentialsUpdate = ...,
    db: Session = Depends(get_db),
    current_admin: User = Depends(get_current_admin_api),
):
    """Partially update Letzshop credentials for a vendor."""
    order_service = get_order_service(db)
    creds_service = get_credentials_service(db)

    try:
        vendor = order_service.get_vendor_or_raise(vendor_id)
    except VendorNotFoundError:
        raise ResourceNotFoundException("Vendor", str(vendor_id))

    try:
        credentials = creds_service.update_credentials(
            vendor_id=vendor_id,
            api_key=credentials_data.api_key,
            api_endpoint=credentials_data.api_endpoint,
            auto_sync_enabled=credentials_data.auto_sync_enabled,
            sync_interval_minutes=credentials_data.sync_interval_minutes,
        )
        db.commit()
    except CredentialsNotFoundError:
        raise ResourceNotFoundException(
            "LetzshopCredentials",
            str(vendor_id),
            message=f"Letzshop credentials not configured for vendor {vendor.name}",
        )

    return LetzshopCredentialsResponse(
        id=credentials.id,
        vendor_id=credentials.vendor_id,
        api_key_masked=creds_service.get_masked_api_key(vendor_id),
        api_endpoint=credentials.api_endpoint,
        auto_sync_enabled=credentials.auto_sync_enabled,
        sync_interval_minutes=credentials.sync_interval_minutes,
        last_sync_at=credentials.last_sync_at,
        last_sync_status=credentials.last_sync_status,
        last_sync_error=credentials.last_sync_error,
        created_at=credentials.created_at,
        updated_at=credentials.updated_at,
    )


@router.delete(
    "/vendors/{vendor_id}/credentials",
    response_model=LetzshopSuccessResponse,
)
def delete_vendor_credentials(
    vendor_id: int = Path(..., description="Vendor ID"),
    db: Session = Depends(get_db),
    current_admin: User = Depends(get_current_admin_api),
):
    """Delete Letzshop credentials for a vendor."""
    order_service = get_order_service(db)
    creds_service = get_credentials_service(db)

    try:
        vendor = order_service.get_vendor_or_raise(vendor_id)
    except VendorNotFoundError:
        raise ResourceNotFoundException("Vendor", str(vendor_id))

    deleted = creds_service.delete_credentials(vendor_id)
    if not deleted:
        raise ResourceNotFoundException(
            "LetzshopCredentials",
            str(vendor_id),
            message=f"Letzshop credentials not configured for vendor {vendor.name}",
        )
    db.commit()

    logger.info(
        f"Admin {current_admin.email} deleted Letzshop credentials for vendor {vendor.name}"
    )

    return LetzshopSuccessResponse(success=True, message="Letzshop credentials deleted")


# ============================================================================
# Connection Testing
# ============================================================================


@router.post(
    "/vendors/{vendor_id}/test",
    response_model=LetzshopConnectionTestResponse,
)
def test_vendor_connection(
    vendor_id: int = Path(..., description="Vendor ID"),
    db: Session = Depends(get_db),
    current_admin: User = Depends(get_current_admin_api),
):
    """Test the Letzshop connection for a vendor using stored credentials."""
    order_service = get_order_service(db)
    creds_service = get_credentials_service(db)

    try:
        order_service.get_vendor_or_raise(vendor_id)
    except VendorNotFoundError:
        raise ResourceNotFoundException("Vendor", str(vendor_id))

    success, response_time_ms, error = creds_service.test_connection(vendor_id)

    return LetzshopConnectionTestResponse(
        success=success,
        message="Connection successful" if success else "Connection failed",
        response_time_ms=response_time_ms,
        error_details=error,
    )


@router.post("/test", response_model=LetzshopConnectionTestResponse)
def test_api_key(
    test_request: LetzshopConnectionTestRequest,
    db: Session = Depends(get_db),
    current_admin: User = Depends(get_current_admin_api),
):
    """Test a Letzshop API key without saving it."""
    creds_service = get_credentials_service(db)

    success, response_time_ms, error = creds_service.test_api_key(
        api_key=test_request.api_key,
        api_endpoint=test_request.api_endpoint,
    )

    return LetzshopConnectionTestResponse(
        success=success,
        message="Connection successful" if success else "Connection failed",
        response_time_ms=response_time_ms,
        error_details=error,
    )


# ============================================================================
# Order Management
# ============================================================================


@router.get(
    "/vendors/{vendor_id}/orders",
    response_model=LetzshopOrderListResponse,
)
def list_vendor_letzshop_orders(
    vendor_id: int = Path(..., description="Vendor ID"),
    skip: int = Query(0, ge=0),
    limit: int = Query(50, ge=1, le=200),
    sync_status: str | None = Query(None, description="Filter by sync status"),
    db: Session = Depends(get_db),
    current_admin: User = Depends(get_current_admin_api),
):
    """List Letzshop orders for a vendor."""
    order_service = get_order_service(db)

    try:
        order_service.get_vendor_or_raise(vendor_id)
    except VendorNotFoundError:
        raise ResourceNotFoundException("Vendor", str(vendor_id))

    orders, total = order_service.list_orders(
        vendor_id=vendor_id,
        skip=skip,
        limit=limit,
        sync_status=sync_status,
    )

    # Get order stats for all statuses
    stats = order_service.get_order_stats(vendor_id)

    return LetzshopOrderListResponse(
        orders=[
            LetzshopOrderResponse(
                id=order.id,
                vendor_id=order.vendor_id,
                letzshop_order_id=order.letzshop_order_id,
                letzshop_shipment_id=order.letzshop_shipment_id,
                letzshop_order_number=order.letzshop_order_number,
                letzshop_state=order.letzshop_state,
                customer_email=order.customer_email,
                customer_name=order.customer_name,
                total_amount=order.total_amount,
                currency=order.currency,
                local_order_id=order.local_order_id,
                sync_status=order.sync_status,
                last_synced_at=order.last_synced_at,
                sync_error=order.sync_error,
                confirmed_at=order.confirmed_at,
                rejected_at=order.rejected_at,
                tracking_set_at=order.tracking_set_at,
                tracking_number=order.tracking_number,
                tracking_carrier=order.tracking_carrier,
                inventory_units=order.inventory_units,
                created_at=order.created_at,
                updated_at=order.updated_at,
            )
            for order in orders
        ],
        total=total,
        skip=skip,
        limit=limit,
        stats=stats,
    )


@router.post(
    "/vendors/{vendor_id}/sync",
    response_model=LetzshopSyncTriggerResponse,
)
def trigger_vendor_sync(
    vendor_id: int = Path(..., description="Vendor ID"),
    sync_request: LetzshopSyncTriggerRequest = LetzshopSyncTriggerRequest(),
    db: Session = Depends(get_db),
    current_admin: User = Depends(get_current_admin_api),
):
    """
    Trigger a sync operation for a vendor.

    This imports new orders from Letzshop.
    """
    order_service = get_order_service(db)
    creds_service = get_credentials_service(db)

    try:
        vendor = order_service.get_vendor_or_raise(vendor_id)
    except VendorNotFoundError:
        raise ResourceNotFoundException("Vendor", str(vendor_id))

    # Verify credentials exist
    try:
        creds_service.get_credentials_or_raise(vendor_id)
    except CredentialsNotFoundError:
        raise ValidationException(
            f"Letzshop credentials not configured for vendor {vendor.name}"
        )

    # Import orders using the client
    try:
        with creds_service.create_client(vendor_id) as client:
            shipments = client.get_unconfirmed_shipments()
            logger.info(
                f"Letzshop sync for vendor {vendor_id}: "
                f"fetched {len(shipments)} unconfirmed shipments from API"
            )

            orders_imported = 0
            orders_updated = 0
            errors = []

            for shipment in shipments:
                try:
                    # Check if order already exists
                    existing = order_service.get_order_by_shipment_id(
                        vendor_id, shipment["id"]
                    )

                    if existing:
                        # Update existing order
                        order_service.update_order_from_shipment(existing, shipment)
                        orders_updated += 1
                    else:
                        # Create new order
                        order_service.create_order(vendor_id, shipment)
                        orders_imported += 1

                except Exception as e:
                    errors.append(
                        f"Error processing shipment {shipment.get('id')}: {e}"
                    )

            db.commit()

            # Update sync status
            creds_service.update_sync_status(
                vendor_id,
                "success" if not errors else "partial",
                "; ".join(errors) if errors else None,
            )

            return LetzshopSyncTriggerResponse(
                success=True,
                message=f"Sync completed: {orders_imported} imported, {orders_updated} updated",
                orders_imported=orders_imported,
                orders_updated=orders_updated,
                errors=errors,
            )

    except LetzshopClientError as e:
        creds_service.update_sync_status(vendor_id, "failed", str(e))
        return LetzshopSyncTriggerResponse(
            success=False,
            message=f"Sync failed: {e}",
            errors=[str(e)],
        )


# ============================================================================
# Jobs (Unified view of imports, exports, and syncs)
# ============================================================================


@router.get(
    "/vendors/{vendor_id}/jobs",
    response_model=LetzshopJobsListResponse,
)
def list_vendor_letzshop_jobs(
    vendor_id: int = Path(..., description="Vendor ID"),
    job_type: str | None = Query(None, description="Filter: import, export, order_sync"),
    status: str | None = Query(None, description="Filter by status"),
    skip: int = Query(0, ge=0),
    limit: int = Query(20, ge=1, le=100),
    db: Session = Depends(get_db),
    current_admin: User = Depends(get_current_admin_api),
):
    """
    Get unified list of Letzshop-related jobs for a vendor.
    Combines product imports, exports, and order syncs.
    """
    order_service = get_order_service(db)

    try:
        order_service.get_vendor_or_raise(vendor_id)
    except VendorNotFoundError:
        raise ResourceNotFoundException("Vendor", str(vendor_id))

    # Use service layer for database queries
    jobs_data, total = order_service.list_letzshop_jobs(
        vendor_id=vendor_id,
        job_type=job_type,
        status=status,
        skip=skip,
        limit=limit,
    )

    # Convert dict data to Pydantic models
    jobs = [LetzshopJobItem(**job) for job in jobs_data]

    return LetzshopJobsListResponse(jobs=jobs, total=total)


# ============================================================================
# Historical Import
# ============================================================================


@router.post(
    "/vendors/{vendor_id}/import-history",
)
def import_historical_orders(
    vendor_id: int = Path(..., description="Vendor ID"),
    state: str = Query("confirmed", description="Shipment state to import"),
    max_pages: int | None = Query(None, ge=1, le=100, description="Max pages to fetch"),
    match_products: bool = Query(True, description="Match EANs to local products"),
    db: Session = Depends(get_db),
    current_admin: User = Depends(get_current_admin_api),
):
    """
    Import historical orders from Letzshop.

    Fetches all shipments with the specified state (default: confirmed)
    and imports them into the database. Supports pagination and EAN matching.

    Returns statistics on imported/updated/skipped orders and product matching.
    """
    order_service = get_order_service(db)
    creds_service = get_credentials_service(db)

    try:
        vendor = order_service.get_vendor_or_raise(vendor_id)
    except VendorNotFoundError:
        raise ResourceNotFoundException("Vendor", str(vendor_id))

    # Verify credentials exist
    try:
        creds_service.get_credentials_or_raise(vendor_id)
    except CredentialsNotFoundError:
        raise ValidationException(
            f"Letzshop credentials not configured for vendor {vendor.name}"
        )

    # Fetch all shipments with pagination
    try:
        with creds_service.create_client(vendor_id) as client:
            logger.info(
                f"Starting historical import for vendor {vendor_id}, state={state}, max_pages={max_pages}"
            )

            shipments = client.get_all_shipments_paginated(
                state=state,
                page_size=50,
                max_pages=max_pages,
            )

            logger.info(f"Fetched {len(shipments)} {state} shipments from Letzshop")

            # Import shipments
            stats = order_service.import_historical_shipments(
                vendor_id=vendor_id,
                shipments=shipments,
                match_products=match_products,
            )

            db.commit()

            # Update sync status
            creds_service.update_sync_status(
                vendor_id,
                "success",
                None,
            )

            logger.info(
                f"Historical import completed: {stats['imported']} imported, "
                f"{stats['updated']} updated, {stats['skipped']} skipped"
            )

            return {
                "success": True,
                "message": f"Historical import completed: {stats['imported']} imported, {stats['updated']} updated",
                "statistics": stats,
            }

    except LetzshopClientError as e:
        creds_service.update_sync_status(vendor_id, "failed", str(e))
        raise ValidationException(f"Letzshop API error: {e}")


@router.get(
    "/vendors/{vendor_id}/import-summary",
)
def get_import_summary(
    vendor_id: int = Path(..., description="Vendor ID"),
    db: Session = Depends(get_db),
    current_admin: User = Depends(get_current_admin_api),
):
    """
    Get summary statistics for imported Letzshop orders.

    Returns total orders, unique customers, and breakdowns by state/locale/country.
    """
    order_service = get_order_service(db)

    try:
        order_service.get_vendor_or_raise(vendor_id)
    except VendorNotFoundError:
        raise ResourceNotFoundException("Vendor", str(vendor_id))

    summary = order_service.get_historical_import_summary(vendor_id)

    return {
        "success": True,
        "summary": summary,
    }


# ============================================================================
# Fulfillment Operations (Admin)
# ============================================================================


@router.post(
    "/vendors/{vendor_id}/orders/{order_id}/confirm",
    response_model=FulfillmentOperationResponse,
)
def confirm_order(
    vendor_id: int = Path(..., description="Vendor ID"),
    order_id: int = Path(..., description="Order ID"),
    db: Session = Depends(get_db),
    current_admin: User = Depends(get_current_admin_api),
):
    """
    Confirm all inventory units for a Letzshop order.

    Sends confirmInventoryUnits mutation with isAvailable=true for all items.
    """
    order_service = get_order_service(db)
    creds_service = get_credentials_service(db)

    try:
        order = order_service.get_order_or_raise(vendor_id, order_id)
    except OrderNotFoundError:
        raise ResourceNotFoundException("LetzshopOrder", str(order_id))

    # Get inventory unit IDs from order
    if not order.inventory_units:
        return FulfillmentOperationResponse(
            success=False,
            message="No inventory units found in order",
        )

    inventory_unit_ids = [u.get("id") for u in order.inventory_units if u.get("id")]

    if not inventory_unit_ids:
        return FulfillmentOperationResponse(
            success=False,
            message="No inventory unit IDs found in order",
        )

    try:
        with creds_service.create_client(vendor_id) as client:
            result = client.confirm_inventory_units(inventory_unit_ids)

            if not result.get("inventoryUnits"):
                error_messages = [
                    e.get("message", "Unknown error")
                    for e in result.get("errors", [])
                ]
                return FulfillmentOperationResponse(
                    success=False,
                    message="Some inventory units could not be confirmed",
                    errors=error_messages,
                )

            # Update order status
            order_service.mark_order_confirmed(order)
            db.commit()

            return FulfillmentOperationResponse(
                success=True,
                message=f"Confirmed {len(inventory_unit_ids)} inventory units",
                confirmed_units=[u.get("id") for u in result.get("inventoryUnits", [])],
            )

    except LetzshopClientError as e:
        return FulfillmentOperationResponse(success=False, message=str(e))


@router.post(
    "/vendors/{vendor_id}/orders/{order_id}/reject",
    response_model=FulfillmentOperationResponse,
)
def reject_order(
    vendor_id: int = Path(..., description="Vendor ID"),
    order_id: int = Path(..., description="Order ID"),
    db: Session = Depends(get_db),
    current_admin: User = Depends(get_current_admin_api),
):
    """
    Decline all inventory units for a Letzshop order.

    Sends confirmInventoryUnits mutation with isAvailable=false for all items.
    """
    order_service = get_order_service(db)
    creds_service = get_credentials_service(db)

    try:
        order = order_service.get_order_or_raise(vendor_id, order_id)
    except OrderNotFoundError:
        raise ResourceNotFoundException("LetzshopOrder", str(order_id))

    # Get inventory unit IDs from order
    if not order.inventory_units:
        return FulfillmentOperationResponse(
            success=False,
            message="No inventory units found in order",
        )

    inventory_unit_ids = [u.get("id") for u in order.inventory_units if u.get("id")]

    if not inventory_unit_ids:
        return FulfillmentOperationResponse(
            success=False,
            message="No inventory unit IDs found in order",
        )

    try:
        with creds_service.create_client(vendor_id) as client:
            result = client.reject_inventory_units(inventory_unit_ids)

            if not result.get("inventoryUnits"):
                error_messages = [
                    e.get("message", "Unknown error")
                    for e in result.get("errors", [])
                ]
                return FulfillmentOperationResponse(
                    success=False,
                    message="Some inventory units could not be declined",
                    errors=error_messages,
                )

            # Update order status
            order_service.mark_order_rejected(order)
            db.commit()

            return FulfillmentOperationResponse(
                success=True,
                message=f"Declined {len(inventory_unit_ids)} inventory units",
            )

    except LetzshopClientError as e:
        return FulfillmentOperationResponse(success=False, message=str(e))


@router.post(
    "/vendors/{vendor_id}/orders/{order_id}/items/{item_id}/confirm",
    response_model=FulfillmentOperationResponse,
)
def confirm_single_item(
    vendor_id: int = Path(..., description="Vendor ID"),
    order_id: int = Path(..., description="Order ID"),
    item_id: str = Path(..., description="Inventory Unit ID"),
    db: Session = Depends(get_db),
    current_admin: User = Depends(get_current_admin_api),
):
    """
    Confirm a single inventory unit in an order.

    Sends confirmInventoryUnits mutation with isAvailable=true for one item.
    """
    order_service = get_order_service(db)
    creds_service = get_credentials_service(db)

    try:
        order = order_service.get_order_or_raise(vendor_id, order_id)
    except OrderNotFoundError:
        raise ResourceNotFoundException("LetzshopOrder", str(order_id))

    try:
        with creds_service.create_client(vendor_id) as client:
            result = client.confirm_inventory_units([item_id])

            if not result.get("inventoryUnits"):
                error_messages = [
                    e.get("message", "Unknown error")
                    for e in result.get("errors", [])
                ]
                return FulfillmentOperationResponse(
                    success=False,
                    message="Failed to confirm item",
                    errors=error_messages,
                )

            # Update local inventory unit state
            order_service.update_inventory_unit_state(order, item_id, "confirmed_available")
            db.commit()

            return FulfillmentOperationResponse(
                success=True,
                message="Item confirmed",
                confirmed_units=[item_id],
            )

    except LetzshopClientError as e:
        return FulfillmentOperationResponse(success=False, message=str(e))


@router.post(
    "/vendors/{vendor_id}/orders/{order_id}/items/{item_id}/decline",
    response_model=FulfillmentOperationResponse,
)
def decline_single_item(
    vendor_id: int = Path(..., description="Vendor ID"),
    order_id: int = Path(..., description="Order ID"),
    item_id: str = Path(..., description="Inventory Unit ID"),
    db: Session = Depends(get_db),
    current_admin: User = Depends(get_current_admin_api),
):
    """
    Decline a single inventory unit in an order.

    Sends confirmInventoryUnits mutation with isAvailable=false for one item.
    """
    order_service = get_order_service(db)
    creds_service = get_credentials_service(db)

    try:
        order = order_service.get_order_or_raise(vendor_id, order_id)
    except OrderNotFoundError:
        raise ResourceNotFoundException("LetzshopOrder", str(order_id))

    try:
        with creds_service.create_client(vendor_id) as client:
            result = client.reject_inventory_units([item_id])

            if not result.get("inventoryUnits"):
                error_messages = [
                    e.get("message", "Unknown error")
                    for e in result.get("errors", [])
                ]
                return FulfillmentOperationResponse(
                    success=False,
                    message="Failed to decline item",
                    errors=error_messages,
                )

            # Update local inventory unit state
            order_service.update_inventory_unit_state(order, item_id, "confirmed_unavailable")
            db.commit()

            return FulfillmentOperationResponse(
                success=True,
                message="Item declined",
            )

    except LetzshopClientError as e:
        return FulfillmentOperationResponse(success=False, message=str(e))