ugoira-builder.js

import { exec } from 'child_process';
import { createHash } from 'crypto';
import { resolve } from 'path';
import { unlink, writeFile } from 'fs/promises';
import JSZip from 'jszip';
import LogMessageOrError from './log.js';

const TEMP_FOLDER = process.env.TEMP || '/tmp/';

const UGOIRA_FILE_EXTENSION = 'mp4';
/** @type {import('../types/social-post').Media['type']} */
const UGOIRA_MEDIA_FILETYPE = 'gif';

/**
 * Builds video sequence from Ugoira
 * @param {import('../types/pixiv-ugoira-meta').UgoiraMeta} ugoiraMeta
 * @param {ArrayBuffer} sourceZip
 * @returns {Promise<import('../types/social-post').Media>}
 */
const UgoiraBuilder = (ugoiraMeta, sourceZip) =>
  new JSZip()
    .loadAsync(sourceZip)
    .then(async (zipAsObject) => {
      /** @type {{ [filename: string]: number }} */
      const ugoiraDelays = {};
      ugoiraMeta.body.frames.forEach((frame) => {
        ugoiraDelays[frame.file] = frame.delay;
      });

      const hash = createHash('md5').update(`${ugoiraMeta.body.originalSrc}_${Date.now()}`).digest('hex');
      const outputFilename = `socialpicker_${hash}_output.${UGOIRA_FILE_EXTENSION}`;
      const outputFilepath = resolve(TEMP_FOLDER, outputFilename);

      /** @type {{ filename: string, tempFilename: string, tempFilepath: string }[]} */
      const storedFiles = [];

      // eslint-disable-next-line no-restricted-syntax, guard-for-in
      for (const filename in zipAsObject.files) {
        const fileAsObject = zipAsObject.files[filename];
        const tempFilename = `socialpicker_${hash}_${filename.replace(/[^\w.]/g, '')}`;
        const tempFilepath = resolve(TEMP_FOLDER, tempFilename);

        // eslint-disable-next-line no-await-in-loop
        const unzipWriteResult = await fileAsObject
          .async('nodebuffer')
          .then((fileAsBuffer) => writeFile(tempFilepath, fileAsBuffer))
          .catch((e) => Promise.resolve(new Error(`Cannot unzip/write file ${filename}: ${e}`)));

        if (unzipWriteResult instanceof Error) throw unzipWriteResult;

        storedFiles.push({ filename, tempFilename, tempFilepath });
      }

      const listFilename = `socialpicker_${hash}_list.txt`;
      const listFilepath = resolve(TEMP_FOLDER, listFilename);
      const listContent = storedFiles
        .map(
          (storedFile) =>
            `file '${storedFile.tempFilename}'\nduration ${((ugoiraDelays[storedFile.filename] || 100) / 1000).toFixed(
              3
            )}`
        )
        .join('\n');

      return writeFile(listFilepath, listContent)
        .then(
          () =>
            new Promise((ffmpegResolve, ffmpegReject) => {
              const ffmpegProcess = exec(
                `ffmpeg -f concat -i "${listFilename}" -vf format=yuv420p "${outputFilename}"`,
                { cwd: TEMP_FOLDER },
                (error, _stdout, stderr) => {
                  if (error || stderr) {
                    ffmpegProcess.kill();
                    ffmpegReject(error || new Error(stderr));
                  }
                }
              );

              ffmpegProcess.on('error', (e) => ffmpegReject(e));
              ffmpegProcess.on('exit', () => ffmpegResolve());
            })
        )
        .then(() => {
          unlink(listFilepath).catch(() => {});
          storedFiles.forEach((storedFile) => unlink(storedFile.tempFilepath).catch(() => {}));

          /** @type {import('../types/social-post').Media} */
          const ugoiraBuilt = {
            type: UGOIRA_MEDIA_FILETYPE,
            externalUrl: ugoiraMeta.body.originalSrc,
            original: ugoiraMeta.body.originalSrc,
            otherSources: { zip: ugoiraMeta.body.originalSrc },
            filetype: UGOIRA_FILE_EXTENSION,
            filename: outputFilepath,
            fileCallback: () => {
              unlink(outputFilepath).catch(() => {});
            },
          };

          return Promise.resolve(ugoiraBuilt);
        });
    })
    .catch((e) => LogMessageOrError('UgoiraBuilder error:', e));

export default UgoiraBuilder;