// Vanilla History API routing, no router dependency (see the routes issue). The URL
// is the source of truth: every route is derived from `location`, never from
// state passed to pushState, so a manually edited or copy-pasted URL works.

export type Route =
  | { kind: "library" }
  | { kind: "queues" }
  | { kind: "settings" }
  | { kind: "search"; query: string }
  | { kind: "movie"; movieId: number }
  | { kind: "releases"; movieId: number }
  | { kind: "series"; seriesId: number }
  | { kind: "seasonReleases"; seriesId: number; seasonNumber: number }
  | { kind: "episodeReleases"; episodeId: number };

export function parseRoute(url: URL): Route {
  const segments = url.pathname.split("/").filter(Boolean);
  if (segments.length === 1 && segments[0] === "queues") {
    return { kind: "queues" };
  }
  if (segments.length === 1 && segments[0] === "settings") {
    return { kind: "settings" };
  }
  if (segments.length === 1 && segments[0] === "search") {
    const query = url.searchParams.get("q") ?? "";
    return query === "" ? { kind: "library" } : { kind: "search", query };
  }
  if (segments.length === 2 && segments[0] === "movies") {
    const movieId = Number(segments[1]);
    if (Number.isInteger(movieId) && movieId > 0) {
      return { kind: "movie", movieId };
    }
  }
  if (segments.length === 3 && segments[0] === "movies" && segments[2] === "releases") {
    const movieId = Number(segments[1]);
    if (Number.isInteger(movieId) && movieId > 0) {
      return { kind: "releases", movieId };
    }
  }
  if (segments.length === 2 && segments[0] === "series") {
    const seriesId = Number(segments[1]);
    if (Number.isInteger(seriesId) && seriesId > 0) {
      return { kind: "series", seriesId };
    }
  }
  if (
    segments.length === 5 &&
    segments[0] === "series" &&
    segments[2] === "seasons" &&
    segments[4] === "releases"
  ) {
    const seriesId = Number(segments[1]);
    const seasonNumber = Number(segments[3]);
    if (
      Number.isInteger(seriesId) &&
      seriesId > 0 &&
      Number.isInteger(seasonNumber) &&
      seasonNumber >= 0
    ) {
      return { kind: "seasonReleases", seriesId, seasonNumber };
    }
  }
  if (segments.length === 3 && segments[0] === "episodes" && segments[2] === "releases") {
    const episodeId = Number(segments[1]);
    if (Number.isInteger(episodeId) && episodeId > 0) {
      return { kind: "episodeReleases", episodeId };
    }
  }
  // §9.7: the library is the homepage — "/" and every unrecognised path land here
  return { kind: "library" };
}

export function routePath(route: Route): string {
  switch (route.kind) {
    case "library":
      return "/";
    case "queues":
      return "/queues";
    case "settings":
      return "/settings";
    case "search":
      return `/search?q=${encodeURIComponent(route.query)}`;
    case "movie":
      return `/movies/${route.movieId}`;
    case "releases":
      return `/movies/${route.movieId}/releases`;
    case "series":
      return `/series/${route.seriesId}`;
    case "seasonReleases":
      return `/series/${route.seriesId}/seasons/${route.seasonNumber}/releases`;
    case "episodeReleases":
      return `/episodes/${route.episodeId}/releases`;
  }
}

export function currentRoute(): Route {
  return parseRoute(new URL(location.href));
}

/**
 * Updates the URL to `route`. `replace: true` rewrites the current entry
 * instead of pushing one — used for search-as-you-type, so every keystroke
 * doesn't add a back-stack entry.
 */
export function navigate(route: Route, options: { replace?: boolean } = {}) {
  const path = routePath(route);
  if (location.pathname + location.search === path) {
    if (options.replace) {
      history.replaceState(null, "", path);
    }
    return;
  }
  if (options.replace) {
    history.replaceState(null, "", path);
  } else {
    history.pushState(null, "", path);
  }
}