wip: untested implementation

TODO @synzr setting up something like vpn and test this

src/modules/processing/services/nicovideo.js

@@ -1,4 +1,128 @@
-// TODO @synzr implement nicovideo
-export default function nicovideo() {
-  return { error: "ErrorEmptyDownload" };
+import { genericUserAgent } from "../../config.js";
+import HLS from "hls-parser";
+import util from "node:util";
+
+const NICOVIDEO_EMBED_URL = "https://embed.nicovideo.jp/watch/%s";
+const NICOVIDEO_GUEST_API_URL =
+  //                                              frontend is embed player
+  "https://www.nicovideo.jp/api/watch/v3_guest/%s?_frontendId=70&_frontendVersion=0&actionTrackId=%s";
+const NICOVIDEO_HLS_API_URL =
+  "https://nvapi.nicovideo.jp/v1/watch/%s/access-rights/hls?actionTrackId=%s";
+
+const ACTION_TRACK_ID_REGEXP =
+  /"actionTrackId":"[A-Za-z0-9]+_[0-9]+"/;
+
+// working
+async function getActionTrackId(id) {
+  const page = await fetch(util.format(NICOVIDEO_EMBED_URL, id), {
+    headers: { "user-agent": genericUserAgent },
+  }).then((response) => response.text());
+
+  if (!ACTION_TRACK_ID_REGEXP.test(page)) {
+    throw new Error(); // we can't fetch the embed page
+  }
+
+  const actionTrackId = page
+    // getting the regexp results
+    .match(ACTION_TRACK_ID_REGEXP)
+    .shift()
+    // getting the actionTrackId field's value
+    .split(":"")
+    .pop()
+    // cleaning from double quotation mark
+    .replaceAll(""", "");
+
+  return actionTrackId;
+}
+
+// not tested
+async function fetchGuestData(id, actionTrackId) {
+  const data = await fetch(
+    util.format(NICOVIDEO_GUEST_API_URL, id, actionTrackId),
+    {
+      headers: { "user-agent": genericUserAgent },
+    }
+  ).then((response) => response.json());
+
+  if (data?.meta?.status !== 200) {
+    console.debug("fetchGuestData():", data)
+    throw new Error();
+  }
+
+  const { videos, audios, accessRightKey } = data.data.media.domand;
+
+  // getting the HQ audio
+  const { id: audioId } = audios
+    .filter((audio) => audio.isAvailable)
+    .sort((firstAudio, secondAudio) => firstAudio.bitrate - secondAudio.bitrate)
+    .pop();
+
+  return {
+    accessRightKey,
+    outputs: videos
+      .filter((video) => video.isAvailable)
+      .map((video) => [video.id, audioId]),
+  };
+}
+
+// not tested
+async function fetchContentURL(id, actionTrackId, accessRightKey, outputs) {
+  const data = await fetch(
+    util.format(NICOVIDEO_HLS_API_URL, id, actionTrackId),
+    {
+      method: "POST",
+      headers: {
+        "user-agent": genericUserAgent,
+        "content-type": "application/json; charset=utf-8",
+        "x-access-right-key": accessRightKey,
+      },
+      body: JSON.stringify({ outputs }),
+    }
+  ).then((response) => response.json());
+
+  if (data?.meta?.status !== 201) {
+    throw new Error();
+  }
+
+  return data.data.contentURL;
+}
+
+// not tested
+async function getHighestQualityHLS(contentURL) {
+  const hls = await fetch(contentURL)
+    .then((response) => response.text())
+    .then((response) => HLS.parse(response));
+
+  const highestQualityHLS = hls.variants
+    .sort((firstVariant, secondVariant) => {
+      const firstVariantPixels =
+        firstVariant.resolution.width * firstVariant.resolution.height;
+      const secondVariantPixels =
+        secondVariant.resolution.width * secondVariant.resolution.height;
+
+      return firstVariantPixels - secondVariantPixels;
+    })
+    .pop();
+
+  return highestQualityHLS;
+}
+
+export default async function nicovideo({ id }) {
+  try {
+    const actionTrackId = await getActionTrackId(id);
+    const highestQualityHLS = await fetchGuestData(actionTrackId)
+      .then(({ accessRightKey, outputs }) =>
+        fetchContentURL(id, actionTrackId, accessRightKey, outputs)
+      )
+      .then((contentURL) => getHighestQualityHLS(contentURL));
+
+    return {
+      urls: highestQualityHLS,
+      isM3U8: true,
+      // TODO @synzr get video information from embed page props
+      filenameAttributes: { service: "niconico", id },
+    };
+  } catch (error) {
+    return { error: "ErrorEmptyDownload" };
+  }
 }