import { useEffect, useMemo, useState } from "react";
import { Link, useParams } from "react-router-dom";
import { ApiError, getRaceById } from "../api";
import { formatDistance, formatRaceDate, getPaceLabel, getRaceStatusLabel } from "../lib";
import type { Race } from "../api";

function getErrorMessage(error: unknown): string {
  if (error instanceof ApiError) {
    return error.message;
  }
  return "Не удалось загрузить карточку старта.";
}

export function RaceDetailsPage(): JSX.Element {
  const { raceId } = useParams<{ raceId: string }>();
  const [race, setRace] = useState<Race | null>(null);
  const [isLoading, setIsLoading] = useState<boolean>(true);
  const [errorMessage, setErrorMessage] = useState<string | null>(null);

  useEffect(() => {
    let isMounted = true;

    async function loadRace(): Promise<void> {
      if (!raceId) {
        setErrorMessage("Не найден идентификатор старта.");
        setIsLoading(false);
        return;
      }

      try {
        const item = await getRaceById(raceId);
        if (!isMounted) {
          return;
        }
        setRace(item);
        setErrorMessage(null);
      } catch (error) {
        if (!isMounted) {
          return;
        }
        setErrorMessage(getErrorMessage(error));
      } finally {
        if (isMounted) {
          setIsLoading(false);
        }
      }
    }

    void loadRace();
    return () => {
      isMounted = false;
    };
  }, [raceId]);

  const paceLabel = useMemo(() => {
    if (!race || race.status !== "completed") {
      return null;
    }
    return getPaceLabel(race.finishTime, race.distanceKm);
  }, [race]);

  if (isLoading) {
    return (
      <section className="page page--race-details" aria-busy="true">
        <h1 className="page__title">Карточка старта</h1>
        <p className="page__subtitle">Загружаем данные старта...</p>
      </section>
    );
  }

  if (errorMessage || !race) {
    return (
      <section className="page page--race-details" role="alert">
        <h1 className="page__title">Карточка старта</h1>
        <p className="page__subtitle page__subtitle--error">{errorMessage ?? "Старт не найден."}</p>
        <Link className="page-link" to="/races">
          Вернуться к списку стартов
        </Link>
      </section>
    );
  }

  const isCompleted = race.status === "completed";

  return (
    <section className="page page--race-details">
      <div className="race-details-header">
        <div className="race-details-header__main">
          <h1 className="page__title">{race.title}</h1>
          <p className="page__subtitle">
            {formatRaceDate(race.date)} · {formatDistance(race.distanceKm)}
          </p>
        </div>
        <span
          className={
            isCompleted
              ? "race-card__status race-card__status--completed"
              : "race-card__status race-card__status--planned"
          }
        >
          {getRaceStatusLabel(race.status)}
        </span>
      </div>

      <div className="race-details-grid">
        <article className="race-details-card">
          <h2 className="race-details-card__title">Основная информация</h2>
          <dl className="race-details-meta">
            <div className="race-details-meta__item">
              <dt className="race-details-meta__key">Дата</dt>
              <dd className="race-details-meta__value">{formatRaceDate(race.date)}</dd>
            </div>
            <div className="race-details-meta__item">
              <dt className="race-details-meta__key">Дистанция</dt>
              <dd className="race-details-meta__value">{formatDistance(race.distanceKm)}</dd>
            </div>
            <div className="race-details-meta__item">
              <dt className="race-details-meta__key">Статус</dt>
              <dd className="race-details-meta__value">{getRaceStatusLabel(race.status)}</dd>
            </div>
          </dl>
        </article>

        <article className="race-details-card">
          <h2 className="race-details-card__title">Completed-метрики</h2>
          {isCompleted ? (
            <dl className="race-details-meta">
              <div className="race-details-meta__item">
                <dt className="race-details-meta__key">Время</dt>
                <dd className="race-details-meta__value">{race.finishTime ?? "время не указано"}</dd>
              </div>
              <div className="race-details-meta__item">
                <dt className="race-details-meta__key">Темп</dt>
                <dd className="race-details-meta__value">{paceLabel ?? "не удалось вычислить"}</dd>
              </div>
              <div className="race-details-meta__item">
                <dt className="race-details-meta__key">Стартовый номер</dt>
                <dd className="race-details-meta__value">{race.bibNumber ?? "не указан"}</dd>
              </div>
            </dl>
          ) : (
            <p className="race-details-card__empty">
              Метрики появятся после завершения старта и ввода результата.
            </p>
          )}
        </article>
      </div>

      <article className="race-details-card race-details-card--notes">
        <h2 className="race-details-card__title">Заметки</h2>
        <p className="race-details-card__notes">{race.notes?.trim() ? race.notes : "Заметок пока нет."}</p>
      </article>

      <Link className="page-link" to="/races">
        Назад к календарю стартов
      </Link>
    </section>
  );
}