import { Badge, Group, Pagination, Paper, Stack, Text, ThemeIcon, Timeline } from "@mantine/core";
import { useQuery } from "@tanstack/react-query";
import {
  ArrowLeftRight,
  History,
  MapPin,
  MessageSquare,
  Minus,
  Plus,
  TrainFront,
  User,
} from "lucide-react";
import { useState } from "react";

import { api } from "@/services/api";
import type { TrainHistoryEntry } from "@/services/trainBuilder.service";

const PAGE_SIZE = 20;

const ACTION_META: Record<
  TrainHistoryEntry["action"],
  { label: string; color: string; icon: typeof Plus }
> = {
  ADD: { label: "Wagon attached", color: "edr-green", icon: Plus },
  REMOVE: { label: "Wagon detached", color: "red", icon: Minus },
  SWITCH: { label: "Wagon switched", color: "blue", icon: ArrowLeftRight },
};

/**
 * "History" tab of the train-builder detail page: every wagon ever attached,
 * detached or switched on this built train — builder edits and trip events
 * (real cuts, mid-route couples, consist adjustments) alike, newest first.
 */
export default function TrainHistoryPanel({ trainId }: { trainId: string }) {
  const [page, setPage] = useState(1);
  const historyQuery = useQuery(
    api.trainBuilder.history.queryOptions({
      input: { id: trainId, page, pageSize: PAGE_SIZE },
      enabled: Boolean(trainId),
      // Keep the previous page on screen while the next one loads.
      placeholderData: (prev) => prev,
    }),
  );
  const entries = historyQuery.data?.items ?? [];
  const totalPages = Math.max(1, historyQuery.data?.meta.totalPages ?? 1);
  const total = historyQuery.data?.meta.total ?? 0;

  return (
    <Paper radius="xl" p="lg" withBorder>
      <Stack gap="lg">
        <Group gap="md" align="center" wrap="nowrap">
          <ThemeIcon size={44} radius="md" variant="light" color="edr-green">
            <History size={22} />
          </ThemeIcon>
          <Stack gap={2}>
            <Text fw={700} fz="lg">
              Wagon history
            </Text>
            <Text size="sm" c="dimmed">
              Who attached, detached or switched which wagon on this train — from
              the builder and from its trips — newest first, with the reason
              given for detaching off a scheduled run.
            </Text>
          </Stack>
        </Group>

        {historyQuery.isLoading ? (
          <Text size="sm" c="dimmed" ta="center" py="md">
            Loading history…
          </Text>
        ) : entries.length === 0 ? (
          <Text size="sm" c="dimmed" ta="center" py="md">
            No wagon changes recorded yet for this train.
          </Text>
        ) : (
          <Timeline bulletSize={26} lineWidth={2} color="edr-green">
            {entries.map((entry) => {
              const meta = ACTION_META[entry.action] ?? ACTION_META.ADD;
              const Icon = meta.icon;
              return (
                <Timeline.Item
                  key={entry.id}
                  bullet={<Icon size={13} />}
                  color={meta.color}
                  title={
                    <Group gap="xs" wrap="nowrap">
                      <Badge size="sm" variant="light" color={meta.color}>
                        {meta.label}
                      </Badge>
                      {entry.subject ? (
                        <Text size="sm" fw={600} ff="monospace">
                          {entry.subject}
                        </Text>
                      ) : null}
                      {entry.scheduleReference ? (
                        <Badge
                          size="sm"
                          variant="light"
                          color="blue"
                          leftSection={<TrainFront size={10} />}
                        >
                          {entry.scheduleReference}
                        </Badge>
                      ) : (
                        <Badge size="sm" variant="light" color="gray">
                          Builder
                        </Badge>
                      )}
                    </Group>
                  }
                >
                  <Group gap="md" mt={2}>
                    <Text size="xs" c="dimmed">
                      {new Date(entry.occurredAt).toLocaleString()}
                    </Text>
                    {entry.yardLabel ? (
                      <Group gap={4} wrap="nowrap">
                        <MapPin size={12} />
                        <Text size="xs" c="dimmed">
                          at {entry.yardLabel}
                        </Text>
                      </Group>
                    ) : null}
                    {entry.actor ? (
                      <Group gap={4} wrap="nowrap">
                        <User size={12} />
                        <Text size="xs" c="dimmed">
                          {entry.actor}
                        </Text>
                      </Group>
                    ) : null}
                  </Group>
                  {entry.reason ? (
                    <Group gap={4} wrap="nowrap" align="flex-start" mt={4}>
                      <MessageSquare
                        size={12}
                        style={{ flexShrink: 0, marginTop: 3 }}
                      />
                      <Text size="xs" c="dimmed" style={{ fontStyle: "italic" }}>
                        {entry.reason}
                      </Text>
                    </Group>
                  ) : null}
                </Timeline.Item>
              );
            })}
          </Timeline>
        )}

        {totalPages > 1 ? (
          <Group justify="space-between">
            <Text size="xs" c="dimmed">
              {total} change(s)
            </Text>
            <Pagination size="sm" value={page} onChange={setPage} total={totalPages} />
          </Group>
        ) : null}
      </Stack>
    </Paper>
  );
}