import { useEffect, useMemo, useState, useRef } from "react";
import axios from "axios";
import { Card, CardBody, Listbox, ListboxItem, type Selection } from "@heroui/react";
import { useTranslation } from "react-i18next";
import { useLanguageStore } from "@/stores/languageStore";
import { useContestStore, type ContestSummary } from "@/stores/contestStore";
import { useContestRefreshStore } from "@/stores/contestRefreshStore";
import { useNavigate } from "react-router-dom";
import RoundsOverview from "./RoundsOverview";

type ContestItem = ContestSummary & {
  description?: string | null;
};

type PaginatedResponse<T> = {
  data: T[];
};

type ContestsOverviewProps = {
  /** Zobraz pouze aktivní závody. Default: false */
  onlyActive?: boolean;
  /** Zahrnout testovací závody. Default: false */
  showTests?: boolean;
  className?: string;
};

export default function ContestsOverview({ onlyActive = false, showTests = false, className }: ContestsOverviewProps) {
  const { t } = useTranslation("common");
  const locale = useLanguageStore((s) => s.locale);
  const refreshKey = useContestRefreshStore((s) => s.refreshKey);
  const navigate = useNavigate();

  const [items, setItems] = useState<ContestItem[]>([]);
  const [loading, setLoading] = useState(true);
  const [error, setError] = useState<string | null>(null);
  const [selectedKeys, setSelectedKeys] = useState<Selection>(new Set(["none"]));
  const lastFetchKey = useRef<string | null>(null);

  const setSelectedContest = useContestStore((s) => s.setSelectedContest);
  const clearSelection = useContestStore((s) => s.clearSelection);
  const selectedContest = useContestStore((s) => s.selectedContest);

  // sync se store
  useEffect(() => {
    if (selectedContest) {
      setSelectedKeys(new Set([String(selectedContest.id)]));
    } else {
      setSelectedKeys(new Set(["none"]));
    }
  }, [selectedContest]);

  useEffect(() => {
    let active = true;
    const fetchKey = `${locale}-${refreshKey}`;

    // pokud už máme data pro tento klíč a seznam není prázdný, nefetchuj
    if (lastFetchKey.current === fetchKey && items.length > 0) {
      setLoading(false);
      return;
    }
    lastFetchKey.current = fetchKey;

    (async () => {
      try {
        setLoading(true);
        setError(null);

        const res = await axios.get<PaginatedResponse<ContestItem> | ContestItem[]>(
          "/api/contests",
          {
            withCredentials: true,
            headers: { Accept: "application/json" },
            params: {
              lang: locale,
              only_active: onlyActive ? 1 : 0,
              include_tests: showTests ? 1 : 0,
            },
          }
        );

        if (!active) return;

        const data = Array.isArray(res.data)
          ? res.data
          : (res.data as PaginatedResponse<ContestItem>).data;

        setItems(data);
      } catch {
        if (!active) return;
        setError(t("unable_to_load_contests") ?? "Nepodařilo se načíst seznam závodů.");
      } finally {
        if (active) setLoading(false);
      }
    })();

    return () => {
      active = false;
    };
  }, [locale, t, refreshKey, items.length, onlyActive, showTests]);

  const visibleItems = useMemo(() => items, [items]);

  const isSelected = (id: string | number) => {
    if (selectedKeys === "all") return false;
    return Array.from(selectedKeys).some((k) => String(k) === String(id));
  };

  const handleSelectionChange = (keys: Selection) => {
    setSelectedKeys(keys);
    if (keys === "all") return;

    const id = Array.from(keys)[0];
    if (!id || id === "none") {
      clearSelection();
      setSelectedKeys(new Set(["none"]));
      navigate("/contests");
      return;
    }

    if (selectedContest && String(selectedContest.id) === String(id)) {
      return;
    }

    const selected = visibleItems.find((c) => String(c.id) === String(id));
    if (selected) {
      setSelectedContest(selected);
      navigate(`/contests/${selected.id}`);
    }
  };

  return (
    <Card className={className}>
      <CardBody className="p-0">
        {loading ? (
          <div className="p-4">{t("contests_loading") ?? "Načítám závody…"}</div>
        ) : error ? (
          <div className="p-4 text-sm text-red-600">{error}</div>
        ) : visibleItems.length === 0 ? (
          <div className="p-4">{t("contests_empty") ?? "Žádné závody nejsou k dispozici."}</div>
        ) : (
          <Listbox
            aria-label="Contests overview"
            selectionMode="single"
            selectedKeys={selectedKeys}
            onSelectionChange={handleSelectionChange}
            variant="flat"
            color="primary"
            shouldHighlightOnFocus={true}
          >
            <ListboxItem key="none" textValue="None">
              <div className="flex flex-col">
                <span className="font-semibold text-sm">
                  {t("contest_index_page") ?? "Přehled závodů"}
                </span>
              </div>
            </ListboxItem>
            {visibleItems.map((item) => (
              <ListboxItem key={item.id} textValue={item.name}>
                <div className="flex flex-col">
                  <span
                    className={`text-sm ${isSelected(item.id) ? "font-semibold text-primary" : "font-medium"}`}
                  >
                    {item.name}
                  </span>
                  <span
                    className={`text-xs line-clamp-2 ${
                      isSelected(item.id) ? "text-primary-500" : "text-foreground-500"
                    }`}
                  >
                    {item.description || "—"}
                  </span>
                </div>
              </ListboxItem>
            ))}
          </Listbox>
        )}
      </CardBody>
    </Card>
  );
}