smov/src/backend/helpers/subs.ts

import { list } from "subsrt-ts";

import { proxiedFetch } from "@/backend/helpers/fetch";
import { convertSubtitlesToSrt } from "@/components/player/utils/captions";
import { CaptionListItem } from "@/stores/player/slices/source";
import { SimpleCache } from "@/utils/cache";

import {
  isExtensionActiveCached,
  sendExtensionRequest,
} from "../extension/messaging";

export const subtitleTypeList = list().map((type) => `.${type}`);
const downloadCache = new SimpleCache<string, string>();
downloadCache.setCompare((a, b) => a === b);
const expirySeconds = 24 * 60 * 60;

/**
 * Always returns SRT
 */
export async function downloadCaption(
  caption: CaptionListItem,
): Promise<string> {
  const cached = downloadCache.get(caption.url);
  if (cached) return cached;

  let data: string | undefined;
  if (caption.needsProxy) {
    if (isExtensionActiveCached()) {
      const extensionResponse = await sendExtensionRequest({
        url: caption.url,
        method: "GET",
      });
      if (
        !extensionResponse?.success ||
        typeof extensionResponse.response.body !== "string"
      ) {
        throw new Error("failed to get caption data from extension");
      }

      data = extensionResponse.response.body;
    } else {
      data = await proxiedFetch<string>(caption.url, { responseType: "text" });
    }
  } else {
    data = await fetch(caption.url).then((v) => v.text());
  }
  if (!data) throw new Error("failed to get caption data");

  const output = convertSubtitlesToSrt(data);
  downloadCache.set(caption.url, output, expirySeconds);
  return output;
}