feat: implement 20ft container weight-pairing validation

- Added ContainerValidationService to handle 20ft weight-pairing logic.
- Introduced validate20ftWeightPairing utility function to check weight differences.
- Updated BookingPricingService to include overweight line details and pairing errors in price response.
- Enhanced BookingTransitionService to reject submissions with unpairable 20ft containers.
- Created ShipmentValidation interface for pre-submit validation of container contracts.
- Integrated shipment validation into the contract booking process, providing warnings for overweight containers and hard blocks for pairing errors.
- Updated front-end components to display validation results and prevent submission when errors are present.

apps/edr-freight-web/portal/src/constants/URLS.ts

@@ -126,6 +126,8 @@ export const URL_CONSTANTS = {
       `/api/contracts/${id}/clearance/documents`,
     CLEARANCE_DUTY_SLIP: (id: string) => `/api/contracts/${id}/clearance/duty-slip`,
     BOOKINGS: (id: string) => `/api/contracts/${id}/bookings`,
+    VALIDATE_SHIPMENT: (id: string) =>
+      `/api/contracts/${id}/validate-shipment`,
     MILESTONES: (id: string) => `/api/contracts/${id}/milestones`,
     BOOKING_MILESTONES: (bookingId: string) =>
       `/api/contracts/bookings/${bookingId}/milestones`,

apps/edr-freight-web/portal/src/pages/contracts/NewShipmentPage.tsx

@@ -22,6 +22,7 @@ import {
 } from "@mantine/core";
 import {
   AlertCircle,
+  AlertTriangle,
   CalendarDays,
   CheckCircle2,
   ChevronLeft,
@@ -34,6 +35,7 @@ import {
 import type { Freight } from "@edr/types";
 import { OperationDatePicker } from "@edr/ui-common";
 import { api } from "@/services/api";
+import type { ShipmentValidation } from "@/services/contracts.service";
 import {
   SelectField,
   StepCard,
@@ -149,6 +151,8 @@ function NewShipmentBookingForm({
     mode: "onChange",
   });
 
+  const isContainerContract = contract.freightType === "CONTAINER";
+
   const submitMutation = useMutation({
     mutationFn: (dto: Freight.CreateBookingUnderContractDto) =>
       api.contracts.createBookingUnderContract.call({ id: contractId, dto }),
@@ -161,6 +165,14 @@ function NewShipmentBookingForm({
     },
   });
 
+  // Pre-submit validation (container contracts only): warns on overweight
+  // containers and HARD-BLOCKS on 20ft wagon-pairing errors. Runs each time the
+  // price modal opens so re-reviewing after an edit re-checks.
+  const validateMutation = useMutation({
+    mutationFn: (dto: Freight.CreateBookingUnderContractDto) =>
+      api.contracts.validateShipment.call({ id: contractId, dto }),
+  });
+
   function buildDto(
     values: ShipmentFormValues,
   ): Freight.CreateBookingUnderContractDto {
@@ -207,13 +219,22 @@ function NewShipmentBookingForm({
     };
   }
 
-  // Submit validates the whole form, then opens the price modal for confirmation.
+  // Submit validates the whole form, then opens the price modal for
+  // confirmation. For container contracts we also run the server-side shipment
+  // validation (overweight warnings + 20ft pairing hard-blocks) so the modal
+  // can surface them before the booking is created.
   const handleReview = form.handleSubmit((values) => {
     setPendingValues(values);
+    if (isContainerContract) {
+      validateMutation.reset();
+      validateMutation.mutate(buildDto(values));
+    }
   });
 
   const handleConfirm = () => {
     if (!pendingValues) return;
+    // Guard: never let a booking with unresolved 20ft pairing errors submit.
+    if ((validateMutation.data?.pairingErrors.length ?? 0) > 0) return;
     submitMutation.mutate(buildDto(pendingValues));
   };
 
@@ -221,6 +242,7 @@ function NewShipmentBookingForm({
   const handleReject = () => {
     if (submitMutation.isPending) return;
     setPendingValues(null);
+    validateMutation.reset();
   };
 
   const routes = contract.routes ?? [];
@@ -323,6 +345,8 @@ function NewShipmentBookingForm({
         contract={contract}
         values={pendingValues}
         loading={submitMutation.isPending}
+        validation={validateMutation.data ?? null}
+        validationLoading={validateMutation.isPending}
         onConfirm={handleConfirm}
         onReject={handleReject}
       />
@@ -334,12 +358,16 @@ function PriceConfirmModal({
   contract,
   values,
   loading,
+  validation,
+  validationLoading,
   onConfirm,
   onReject,
 }: {
   contract: Freight.IContract;
   values: ShipmentFormValues | null;
   loading: boolean;
+  validation: ShipmentValidation | null;
+  validationLoading: boolean;
   onConfirm: () => void;
   onReject: () => void;
 }) {
@@ -348,6 +376,11 @@ function PriceConfirmModal({
     [contract, values],
   );
 
+  const overweightLines = validation?.overweightLines ?? [];
+  const pairingErrors = validation?.pairingErrors ?? [];
+  const hasPairingBlock = pairingErrors.length > 0;
+  const confirmDisabled = loading || validationLoading || hasPairingBlock;
+
   return (
     <Modal
       opened={Boolean(values)}
@@ -376,6 +409,60 @@ function PriceConfirmModal({
     >
       {total ? (
         <Stack gap="md">
+          {validationLoading && (
+            <Group gap={8} c="dimmed">
+              <Loader size="xs" color="edr-green" />
+              <Text fz="sm" c="dimmed">
+                Checking container weights and wagon pairing…
+              </Text>
+            </Group>
+          )}
+
+          {hasPairingBlock && (
+            <Alert
+              color="red"
+              variant="light"
+              radius="md"
+              icon={<AlertCircle size={16} />}
+              title="Cannot create booking — 20ft wagon pairing"
+            >
+              <Stack gap={6}>
+                {pairingErrors.map((msg, i) => (
+                  <Text key={i} fz="sm" c="red.8">
+                    {msg}
+                  </Text>
+                ))}
+                <Text fz="xs" c="red.7" mt={2}>
+                  Adjust the 20ft container weights or quantities so pairs differ
+                  by no more than 10 tons.
+                </Text>
+              </Stack>
+            </Alert>
+          )}
+
+          {overweightLines.length > 0 && (
+            <Alert
+              color="yellow"
+              variant="light"
+              radius="md"
+              icon={<AlertTriangle size={16} />}
+              title="Overweight containers"
+            >
+              <Stack gap={6}>
+                {overweightLines.map((line, i) => (
+                  <Text key={i} fz="sm" c="#9A5B00">
+                    {line.containerTypeCode}: {line.totalVgmTons}t exceeds limit{" "}
+                    {line.maxAllowedTons}t (+{line.excessTons}t overweight)
+                  </Text>
+                ))}
+                <Text fz="xs" c="#9A5B00" mt={2}>
+                  An overweight surcharge applies. You can still submit, or go
+                  back and adjust weights.
+                </Text>
+              </Stack>
+            </Alert>
+          )}
+
           <Paper withBorder radius={16} p="lg" style={{ borderColor: "#E6ECF2" }}>
             <Stack gap={10}>
               {total.lines.map((line, i) => (
@@ -442,6 +529,7 @@ function PriceConfirmModal({
               leftSection={<CheckCircle2 size={16} />}
               onClick={onConfirm}
               loading={loading}
+              disabled={confirmDisabled}
             >
               Confirm &amp; book
             </Button>

apps/edr-freight-web/portal/src/services/api.ts

@@ -24,6 +24,7 @@ import {
   ContractDocuments,
   GenerateContractPriceResponse,
   SubmitContractResponse,
+  ShipmentValidation,
 } from "./contracts.service";
 import type { BookingDocuments } from "@/pages/bookings/new-booking-form/schema";
 import {
@@ -462,6 +463,13 @@ export const api = {
       contractsService.createBookingUnderContract(id, dto),
     ),
 
+    validateShipment: endpoint<
+      { id: string; dto: Freight.CreateBookingUnderContractDto },
+      ShipmentValidation
+    >("contracts", "validateShipment", ({ id, dto }) =>
+      contractsService.validateShipment(id, dto),
+    ),
+
     getContractMilestones: endpoint<
       { id: string },
       Freight.IClearanceMilestone[]

apps/edr-freight-web/portal/src/services/contracts.service.ts

@@ -33,6 +33,25 @@ export interface SubmitContractResponse {
   message?: string;
 }
 
+/** A container line whose total VGM exceeds the weight-limit rule. */
+export interface OverweightLine {
+  containerTypeCode: string;
+  totalVgmTons: number;
+  maxAllowedTons: number;
+  excessTons: number;
+}
+
+/**
+ * Pre-submit validation for a shipment booking under a CONTAINER contract.
+ * `overweightLines` are WARNINGS only (an overweight surcharge applies — the
+ * customer may still submit); `pairingErrors` are HARD BLOCKS (20ft containers
+ * that cannot be balanced onto wagons) and must prevent booking.
+ */
+export interface ShipmentValidation {
+  overweightLines: OverweightLine[];
+  pairingErrors: string[];
+}
+
 export interface ContractListFilter {
   status?: string;
   statuses?: string;
@@ -285,6 +304,20 @@ export const contractsService = {
     return data.data.booking ?? data.data;
   },
 
+  /**
+   * Pre-submit validation of a shipment booking (same DTO as
+   * `createBookingUnderContract`). Returns overweight warnings and hard-block
+   * 20ft wagon-pairing errors so the customer can be warned/blocked before the
+   * booking is created.
+   */
+  validateShipment: async (
+    id: string,
+    dto: Freight.CreateBookingUnderContractDto,
+  ): Promise<ShipmentValidation> => {
+    const { data } = await client.post(C.VALIDATE_SHIPMENT(id), dto);
+    return data.data ?? data;
+  },
+
   // ── Milestones ──
   getContractMilestones: async (
     id: string,