@nftgo/gorarity/dist/mjs/rarity-ranker.js

An algorithm to calculate rarity of NFT(how special it is), based on Jaccard Distance.

import { Scorer } from './scoring';
import { TokenFeatureExtractor } from './scoring/token-feature-extractor';
export class RarityRanker {
    static defaultScorer = new Scorer();
    constructor() { }
    /**
     * @description Ranks tokens in the collection with the default scorer implementation.
     * @param collection
     * @param scorer
     * @returns Array of TokenRarity objects with score, rank and token information sorted by rank.
     */
    static rankCollection(collection, scorer = RarityRanker.defaultScorer) {
        if (!collection || !collection.tokens || collection.tokens.length === 0)
            return [];
        const tokens = collection.tokens;
        const scores = scorer.scoreTokens(collection, tokens);
        if (scores.length !== tokens.length) {
            throw new Error(`dimension of scores doesn't match dimension of tokens`);
        }
        const tokenRarities = [];
        for (let idx = 0; idx < tokens.length; idx++) {
            const tokenFeatures = TokenFeatureExtractor.extractUniqueTraitCount(collection, tokens[idx]);
            tokenRarities.push({
                token: tokens[idx],
                score: scores[idx],
                tokenFeatures: tokenFeatures,
                rank: 0, // Prefill
            });
        }
        return RarityRanker.setRarityRanks(tokenRarities);
    }
    /**
     * @description Set the ranking of token according to it's rarity socre.
     * @param tokenRarities Unordered array of tokens with rarity score information
     * @returns Ordered array of tokens sorted by score descending
     */
    static setRarityRanks(tokenRarities) {
        tokenRarities.sort((a, b) => b.score - a.score);
        let rank = 0;
        let preScore = -1;
        let i = 0;
        for (const tokenRarity of tokenRarities) {
            if (tokenRarity.score !== preScore) {
                rank = i + 1;
                preScore = tokenRarity.score;
            }
            tokenRarity.rank = rank;
            i++;
        }
        return tokenRarities;
    }
}