import {
  Alert,
  Badge,
  Button,
  Group,
  Loader,
  NumberInput,
  Paper,
  Select,
  SimpleGrid,
  Stack,
  Table,
  Text,
  Tooltip,
} from "@mantine/core";
import { useMutation, useQuery } from "@tanstack/react-query";
import { isAxiosError } from "axios";
import { AlertTriangle, Lock, MapPin } from "lucide-react";
import { useMemo, useState } from "react";

import { useToast } from "@/hooks/use-toast";
import { api } from "@/services/api";
import type { ScheduleWagonYardRow } from "@/services/trainBuilder.service";

/**
 * Schedule yards tab: where THIS departure plans to board each consist wagon,
 * side by side with where the wagon physically stands (the train builder's
 * truth). Booking capacity per origin reads the plan; dispatch refuses to
 * leave until plan and physical yards agree. Edits are queued locally and
 * saved in one PATCH.
 */

const parseError = (error: unknown, fallback: string) => {
  if (isAxiosError(error)) {
    const message = error.response?.data?.message;
    if (Array.isArray(message)) return message.join(", ");
    if (typeof message === "string") return message;
  }
  return fallback;
};

interface Props {
  scheduleId: string;
  canEdit: boolean;
}

export function ScheduleWagonYardPanel({ scheduleId, canEdit }: Props) {
  const { toast } = useToast();
  const query = useQuery(
    api.trainScheduling.scheduleWagonYards.queryOptions({ input: { scheduleId } }),
  );
  const save = useMutation(api.trainScheduling.updateScheduleWagonYards.mutationOptions());
  const data = query.data;

  /** wagonId → yardId queued but not yet saved. */
  const [pending, setPending] = useState<Record<string, string>>({});
  const [bulkType, setBulkType] = useState<string | null>(null);
  const [bulkFrom, setBulkFrom] = useState<string | null>(null);
  const [bulkTo, setBulkTo] = useState<string | null>(null);
  const [bulkCount, setBulkCount] = useState<number | string>(1);

  const editable = Boolean(canEdit && data?.editable);
  const pickupStops = useMemo(() => (data?.stops ?? []).filter((s) => s.pickup), [data]);
  const yardOptions = pickupStops.map((s) => ({ value: s.yardId, label: s.label }));
  const yardLabel = (id: string | null) =>
    (data?.stops ?? []).find((s) => s.yardId === id)?.label ??
    data?.wagons.find((w) => w.plannedYardId === id)?.plannedYardLabel ??
    data?.wagons.find((w) => w.physicalYardId === id)?.physicalYardLabel ??
    id ??
    "—";

  const effectiveYard = (w: ScheduleWagonYardRow) => pending[w.id] ?? w.plannedYardId;

  const perStop = useMemo(
    () =>
      (data?.stops ?? []).map((s) => ({
        ...s,
        planned: (data?.wagons ?? []).filter((w) => (pending[w.id] ?? w.plannedYardId) === s.yardId)
          .length,
      })),
    [data, pending],
  );
  const typeOptions = useMemo(() => {
    const seen = new Map<string, string>();
    for (const w of data?.wagons ?? []) seen.set(w.wagonType.id, w.wagonType.code);
    return [...seen].map(([value, label]) => ({ value, label }));
  }, [data]);

  const pendingCount = Object.keys(pending).length;

  const queueBulk = () => {
    if (!data || !bulkFrom || !bulkTo || bulkFrom === bulkTo) return;
    const n = Number(bulkCount) || 0;
    const picked = data.wagons
      .filter(
        (w) =>
          !w.locked &&
          effectiveYard(w) === bulkFrom &&
          (!bulkType || w.wagonType.id === bulkType),
      )
      .slice(0, n);
    if (!picked.length) {
      toast({ title: "No free wagons match", variant: "destructive" });
      return;
    }
    setPending((prev) => {
      const next = { ...prev };
      for (const w of picked) {
        if (w.plannedYardId === bulkTo) delete next[w.id];
        else next[w.id] = bulkTo;
      }
      return next;
    });
  };

  const handleSave = async () => {
    if (!pendingCount) return;
    try {
      const result = await save.mutateAsync({
        scheduleId,
        payload: {
          moves: Object.entries(pending).map(([wagonId, yardId]) => ({ wagonId, yardId })),
        },
      });
      setPending({});
      toast({
        title: `Schedule yards updated — ${pendingCount} wagon(s) re-planned`,
        description: result.warnings.length ? result.warnings.join(" ") : undefined,
        variant: result.warnings.length ? "destructive" : undefined,
      });
    } catch (err) {
      toast({
        title: "Update failed",
        description: parseError(err, "Could not update the schedule's wagon yards"),
        variant: "destructive",
      });
    }
  };

  if (query.isLoading) return <Loader size="sm" />;
  if (query.isError || !data) {
    return (
      <Alert color="red" icon={<AlertTriangle size={16} />}>
        {parseError(
          query.error,
          "This schedule has no wagon yard plan (not created from a built train).",
        )}
      </Alert>
    );
  }

  return (
    <Stack gap="md">
      <Alert color="blue" icon={<MapPin size={16} />} variant="light">
        <b>Planned</b> = where this departure boards the wagon (what customers can book per
        origin). <b>Physical</b> = where the wagon stands now (train builder). Dispatch is blocked
        until every wagon stands at its planned yard.
        {data.misaligned > 0 ? (
          <Text component="span" c="orange" fw={600}>
            {" "}
            {data.misaligned} wagon(s) currently misaligned.
          </Text>
        ) : null}
      </Alert>

      <SimpleGrid cols={{ base: 2, sm: 3, md: Math.min(5, Math.max(2, perStop.length)) }}>
        {perStop.map((s) => (
          <Paper key={s.yardId} withBorder p="sm" radius="md">
            <Group justify="space-between" mb={4}>
              <Text fw={600} size="sm">
                {s.label}
              </Text>
              {!s.pickup ? (
                <Badge size="xs" color="gray" variant="light">
                  destination
                </Badge>
              ) : null}
            </Group>
            <Group gap="xs">
              <Badge color="edr-green" variant="filled">
                Planned {s.planned}
              </Badge>
              <Badge color={s.physical === s.planned ? "gray" : "orange"} variant="light">
                Physical {s.physical}
              </Badge>
            </Group>
          </Paper>
        ))}
      </SimpleGrid>

      {editable ? (
        <Paper withBorder p="sm" radius="md">
          <Group align="end" gap="sm" wrap="wrap">
            <NumberInput
              label="Move"
              min={1}
              max={data.wagons.length}
              value={bulkCount}
              onChange={setBulkCount}
              w={90}
            />
            <Select
              label="Wagon type"
              placeholder="Any"
              clearable
              data={typeOptions}
              value={bulkType}
              onChange={setBulkType}
              w={140}
            />
            <Select label="From" data={yardOptions} value={bulkFrom} onChange={setBulkFrom} w={170} />
            <Select label="To" data={yardOptions} value={bulkTo} onChange={setBulkTo} w={170} />
            <Button
              variant="light"
              onClick={queueBulk}
              disabled={!bulkFrom || !bulkTo || bulkFrom === bulkTo}
            >
              Queue
            </Button>
          </Group>
        </Paper>
      ) : null}

      <Table striped highlightOnHover withTableBorder>
        <Table.Thead>
          <Table.Tr>
            <Table.Th>#</Table.Th>
            <Table.Th>Wagon</Table.Th>
            <Table.Th>Type</Table.Th>
            <Table.Th>Physical yard</Table.Th>
            <Table.Th>Planned yard (this schedule)</Table.Th>
            <Table.Th>Status</Table.Th>
          </Table.Tr>
        </Table.Thead>
        <Table.Tbody>
          {data.wagons.map((w) => {
            const planned = effectiveYard(w);
            const changed = w.id in pending;
            return (
              <Table.Tr key={w.id} bg={changed ? "var(--mantine-color-yellow-light)" : undefined}>
                <Table.Td>{w.sequenceNumber ?? "—"}</Table.Td>
                <Table.Td>
                  <Text fw={600} size="sm">
                    {w.wagonNumber}
                  </Text>
                </Table.Td>
                <Table.Td>{w.wagonType.code}</Table.Td>
                <Table.Td>{w.physicalYardLabel ?? "No yard"}</Table.Td>
                <Table.Td>
                  {editable && !w.locked ? (
                    <Select
                      size="xs"
                      data={yardOptions}
                      value={planned}
                      onChange={(v) =>
                        setPending((prev) => {
                          const next = { ...prev };
                          if (!v || v === w.plannedYardId) delete next[w.id];
                          else next[w.id] = v;
                          return next;
                        })
                      }
                      w={180}
                    />
                  ) : (
                    <Group gap={4}>
                      <Text size="sm">{yardLabel(planned)}</Text>
                      {w.locked ? (
                        <Tooltip label={w.lockReason ?? "Locked"}>
                          <Lock size={14} />
                        </Tooltip>
                      ) : null}
                    </Group>
                  )}
                </Table.Td>
                <Table.Td>
                  {planned === w.physicalYardId ? (
                    <Badge color="teal" variant="light" size="sm">
                      Aligned
                    </Badge>
                  ) : (
                    <Badge color="orange" variant="light" size="sm">
                      Needs move
                    </Badge>
                  )}
                </Table.Td>
              </Table.Tr>
            );
          })}
        </Table.Tbody>
      </Table>

      {editable ? (
        <Group justify="flex-end">
          <Text size="sm" c="dimmed">
            {pendingCount} pending change(s)
          </Text>
          <Button variant="default" onClick={() => setPending({})} disabled={!pendingCount}>
            Discard
          </Button>
          <Button
            onClick={() => void handleSave()}
            loading={save.isPending}
            disabled={!pendingCount}
          >
            Save plan
          </Button>
        </Group>
      ) : null}
    </Stack>
  );
}