aniplay-api/src/libs/findBestMatchingTitle.ts

function findBestMatch(mainString: string, targets: string[]): string | null {
  if (targets.length === 0) {
    return null;
  }
  if (targets.length === 1) {
    return targets[0];
  }

  let bestMatch = targets[0];
  let highestScore = stringMatchingAlgorithm(mainString, bestMatch);

  for (let i = 1; i < targets.length; i++) {
    const currentScore = stringMatchingAlgorithm(mainString, targets[i]);
    if (currentScore === 1) {
      bestMatch = targets[i];
      break;
    }

    if (currentScore > highestScore) {
      highestScore = currentScore;
      bestMatch = targets[i];
    }
  }

  return bestMatch;
}

type Title = {
  english: string;
  userPreferred: string;
};

export const findBestMatchingTitle = (
  title: Partial<Title>,
  titlesToSearch: Partial<Title>[],
): { title: string | null; score: number } => {
  const { english, userPreferred } = title;

  let match;
  let expectedSuffix = "";
  if ((match = english?.match(/my hero academia.+([0-9])$/))) {
    expectedSuffix = match[1];
  }

  const userPreferredBestMatch = userPreferred
    ? findBestMatch(
        userPreferred,
        titlesToSearch
          .map((title) => title.userPreferred?.toLowerCase())
          .filter(
            (title) =>
              title !== undefined &&
              (!expectedSuffix || title.endsWith(expectedSuffix)),
          ),
      )
    : null;
  const englishBestMatch = english
    ? findBestMatch(
        english,
        titlesToSearch
          .map((title) => title.english?.toLowerCase())
          .filter(
            (title) =>
              title !== undefined &&
              (!expectedSuffix || title.endsWith(expectedSuffix)),
          ),
      )
    : null;

  const userPreferredScore = userPreferredBestMatch
    ? stringMatchingAlgorithm(userPreferred!, userPreferredBestMatch)
    : 0;
  const englishScore = englishBestMatch
    ? stringMatchingAlgorithm(english!, englishBestMatch)
    : 0;

  console.log(title.english, englishScore);
  console.log(title.userPreferred, userPreferredScore);
  if (userPreferredScore >= englishScore) {
    console.log("User preferred", userPreferredBestMatch);
    return { title: userPreferredBestMatch, score: userPreferredScore };
  } else {
    console.log("English", englishBestMatch);
    return { title: englishBestMatch, score: englishScore };
  }
};

function stringMatchingAlgorithm(s1: string, s2: string): number {
  // current implementation is the Jaro-Winkler algorithm
  // copied from https://discord.com/channels/987492554486452315/1273988465222090783/1273988465222090783
  const m = s1.length;
  const n = s2.length;

  if (m === 0 && n === 0) return 1.0;
  if (m === 0 || n === 0) return 0.0;

  const matchDistance = Math.floor(Math.max(m, n) / 2) - 1;
  const s1Matches = new Array(m).fill(false);
  const s2Matches = new Array(n).fill(false);

  let matches = 0;
  let transpositions = 0;
  for (let i = 0; i < m; i++) {
    const start = Math.max(0, i - matchDistance);
    const end = Math.min(n - 1, i + matchDistance);

    for (let j = start; j <= end; j++) {
      if (s2Matches[j]) continue;
      if (s1[i] !== s2[j]) continue;
      s1Matches[i] = true;
      s2Matches[j] = true;
      matches++;
      break;
    }
  }

  if (matches === 0) return 0.0;

  let k = 0;
  for (let i = 0; i < m; i++) {
    if (!s1Matches[i]) continue;
    while (!s2Matches[k]) k++;
    if (s1[i] !== s2[k]) transpositions++;
    k++;
  }

  transpositions /= 2;

  const jaro =
    (matches / m + matches / n + (matches - transpositions) / matches) / 3;

  const prefix = Math.min(
    4,
    [...s1].findIndex((ch, i) => s1[i] !== s2[i]),
  );
  const p = 0.1;

  return jaro + prefix * p * (1 - jaro);
}