/**
 * Returns a number determining how similiar the second string is to the first (0-1)
 * @param first The first string
 * @param second The second string
 * @returns Similarity determiner
 */
export function stringSimilarity(first: string, second: string) {
    first = first.replace(/\s+/g, '');
    second = second.replace(/\s+/g, '');

    if (first === second) return 1;
    if (first.length < 2 || second.length < 2) return 0;

    let firstBigrams = new Map();
    for (let i = 0; i < first.length - 1; i++) {
        const bigram = first.substring(i, i + 2);
        const count = firstBigrams.has(bigram)
            ? firstBigrams.get(bigram) + 1
            : 1;

        firstBigrams.set(bigram, count);
    }

    let intersectionSize = 0;
    for (let i = 0; i < second.length - 1; i++) {
        const bigram = second.substring(i, i + 2);
        const count = firstBigrams.has(bigram) ? firstBigrams.get(bigram) : 0;

        if (count > 0) {
            firstBigrams.set(bigram, count - 1);
            intersectionSize++;
        }
    }

    return (2.0 * intersectionSize) / (first.length + second.length - 2);
}