import { useMemo } from 'react';
import { useNavigate } from 'react-router-dom';
import { Badge, Button, Card, Group, Tabs, Text } from '@mantine/core';
import { CreditCard, Eye, Truck, TrainFront } from 'lucide-react';
import { DataTable, type ColumnDef } from '@edr/ui-common';

import { PageContainer, PageHeader } from '@/components/page';
import {
  InventoryWorkbench,
  VisualEmptyState,
  formatNumber,
} from '@/components/warehouses';
import { LoadToTrainPanel } from '@/components/warehouses/LoadToTrainPanel';
import { useMutation, useQuery } from '@tanstack/react-query';

import { api } from '@/services/api';
import { useToast } from '@/hooks/use-toast';
import type { WarehouseInventoryItem } from '@/types/warehouse';

const isPaid = (item: WarehouseInventoryItem) => item.booking?.status === 'PAID';

/**
 * Loading Queue — manage inventory through the loading workflow.
 * Tabs:
 *   - Ready to Load: READY_FOR_LOADING + booking PAID (can Mark as Loaded)
 *   - Pending Payment: READY_FOR_LOADING + booking not PAID (no Load action)
 *   - Loaded Inventory: LOADED (can Dispatch)
 *   - Dispatch Queue: LOADED (can Dispatch)
 */
export default function LoadingQueuePage() {
  const navigate = useNavigate();
  const { toast } = useToast();
  const autoLoad = useMutation(api.warehouses.autoLoadReady.mutationOptions());
  const { data: readyData, isLoading: readyLoading } = useQuery(
    api.warehouses.listInventory.queryOptions({
      input: { filter: { status: 'READY_FOR_LOADING' } },
    }),
  );
  const { data: loadedData, isLoading: loadedLoading } = useQuery(
    api.warehouses.listInventory.queryOptions({ input: { filter: { status: 'LOADED' } } }),
  );

  const handleAutoLoad = async () => {
    try {
      const r = await autoLoad.mutateAsync();
      toast({
        title: 'Auto-load complete',
        description: `Loaded ${r.loadedCount} PAID item(s); skipped ${r.skippedCount} (unpaid stay pending).`,
      });
    } catch {
      toast({ variant: 'destructive', title: 'Auto-load failed' });
    }
  };

  const readyItems = readyData ?? [];
  const loadedItems = loadedData ?? [];

  const paidItems = useMemo(() => readyItems.filter(isPaid), [readyItems]);
  const unpaidItems = useMemo(() => readyItems.filter((i) => !isPaid(i)), [readyItems]);

  return (
    <PageContainer>
      <PageHeader
        title="Loading Queue"
        subtitle="Manage bookings and inventory through the loading workflow."
        action={
          <Button
            leftSection={<Truck size={16} />}
            loading={autoLoad.isPending}
            onClick={handleAutoLoad}
          >
            Auto Load Ready Items
          </Button>
        }
      />

      <Card>
        <Tabs defaultValue="ready">
            <Tabs.List>
              <Tabs.Tab
                value="ready"
                leftSection={
                  <Badge size="xs" color="edr-green">
                    {paidItems.length}
                  </Badge>
                }
              >
                Ready to Load
              </Tabs.Tab>
              <Tabs.Tab
                value="pending"
                leftSection={
                  <Badge size="xs" color="orange">
                    {unpaidItems.length}
                  </Badge>
                }
              >
                Pending Payment
              </Tabs.Tab>
              <Tabs.Tab
                value="loaded"
                leftSection={
                  <Badge size="xs" color="teal">
                    {loadedItems.length}
                  </Badge>
                }
              >
                Loaded Inventory
              </Tabs.Tab>
              <Tabs.Tab
                value="dispatch"
                leftSection={
                  <Badge size="xs" color="blue">
                    {loadedItems.length}
                  </Badge>
                }
              >
                Dispatch Queue
              </Tabs.Tab>
              <Tabs.Tab value="load-train" leftSection={<TrainFront size={14} />}>
                Load to Train
              </Tabs.Tab>
            </Tabs.List>

            {/* Ready to Load — PAID bookings, can be marked Loaded */}
            <Tabs.Panel value="ready" pt="md">
              {!readyLoading && paidItems.length === 0 ? (
                <VisualEmptyState
                  variant="wagon"
                  title="Nothing ready to load"
                  description="Paid bookings marked Ready For Loading appear here, ready to load onto a wagon."
                />
              ) : (
                <InventoryWorkbench items={paidItems} isLoading={readyLoading} />
              )}
            </Tabs.Panel>

            {/* Pending Payment — unpaid bookings, read-only (no Load action) */}
            <Tabs.Panel value="pending" pt="md">
              {!readyLoading && unpaidItems.length === 0 ? (
                <VisualEmptyState
                  variant="cargo"
                  title="No unpaid bookings"
                  description="Ready-for-loading items whose booking is not yet PAID appear here."
                />
              ) : (
                <PendingPaymentTable items={unpaidItems} onNavigate={navigate} />
              )}
            </Tabs.Panel>

            {/* Loaded Inventory — LOADED items, can Dispatch */}
            <Tabs.Panel value="loaded" pt="md">
              {!loadedLoading && loadedItems.length === 0 ? (
                <VisualEmptyState
                  variant="container"
                  title="No loaded inventory yet"
                  description="Items loaded onto a wagon appear here, ready to dispatch."
                />
              ) : (
                <InventoryWorkbench items={loadedItems} isLoading={loadedLoading} />
              )}
            </Tabs.Panel>

            {/* Dispatch Queue — LOADED items awaiting departure */}
            <Tabs.Panel value="dispatch" pt="md">
              {!loadedLoading && loadedItems.length === 0 ? (
                <VisualEmptyState
                  variant="train"
                  title="Nothing to dispatch"
                  description="Loaded items appear here, ready to mark as dispatched."
                />
              ) : (
                <InventoryWorkbench items={loadedItems} isLoading={loadedLoading} />
              )}
            </Tabs.Panel>

            {/* Load to Train — per-train arrived containers/cargoes, multiselect → load onto wagons */}
            <Tabs.Panel value="load-train" pt="md">
              <LoadToTrainPanel />
            </Tabs.Panel>
        </Tabs>
      </Card>
    </PageContainer>
  );
}

interface PendingPaymentTableProps {
  items: WarehouseInventoryItem[];
  onNavigate: (path: string) => void;
}

/** Read-only view of unpaid ready-for-loading items. No Mark-as-Loaded action. */
function PendingPaymentTable({ items, onNavigate }: PendingPaymentTableProps) {
  const columns: ColumnDef<WarehouseInventoryItem>[] = [
    {
      id: 'booking',
      header: 'Booking',
      cell: ({ row }) => (
        <Text fw={600} size="sm">
          {row.original.booking?.reference ?? row.original.bookingId?.slice(0, 8) ?? '—'}
        </Text>
      ),
    },
    { id: 'warehouse', header: 'Warehouse', cell: ({ row }) => row.original.warehouse?.code ?? '—' },
    { id: 'zone', header: 'Zone', cell: ({ row }) => row.original.zone?.code ?? '—' },
    { id: 'weight', header: 'Weight (kg)', cell: ({ row }) => formatNumber(row.original.weight) },
    {
      id: 'payment',
      header: 'Payment',
      cell: ({ row }) => (
        <Badge color="orange" variant="light" size="sm">
          {row.original.booking?.status ?? row.original.booking?.paymentStatus ?? 'UNPAID'}
        </Badge>
      ),
    },
    {
      id: 'actions',
      header: '',
      cell: ({ row }) => {
        const item = row.original;
        return (
          <Group gap="xs" justify="flex-end" wrap="nowrap" onClick={(e) => e.stopPropagation()}>
            <Button
              size="compact-xs"
              variant="light"
              color="gray"
              leftSection={<Eye size={14} />}
              disabled={!item.bookingId}
              onClick={() => item.bookingId && onNavigate(`/dashboard/booking-requests/${item.bookingId}`)}
            >
              Booking
            </Button>
            <Button
              size="compact-xs"
              variant="light"
              leftSection={<CreditCard size={14} />}
              disabled={!item.bookingId}
              onClick={() => item.bookingId && onNavigate(`/dashboard/booking-requests/${item.bookingId}`)}
            >
              Payment
            </Button>
          </Group>
        );
      },
    },
  ];

  return (
    <DataTable
      columns={columns}
      data={items}
      status="success"
      emptyMessage="No unpaid items."
      containerClassName="border-0 shadow-none"
    />
  );
}