gecko-dev/browser/components/tabbrowser/SmartTabGrouping.sys.mjs

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

import { XPCOMUtils } from "resource://gre/modules/XPCOMUtils.sys.mjs";
import { createEngine } from "chrome://global/content/ml/EngineProcess.sys.mjs";
import {
  cosSim,
  KeywordExtractor,
} from "chrome://global/content/ml/NLPUtils.sys.mjs";

import {
  computeCentroidFrom2DArray,
  computeRandScore,
  euclideanDistance,
  getAccuracyStats,
  kmeansPlusPlus,
  silhouetteCoefficients,
} from "chrome://global/content/ml/ClusterAlgos.sys.mjs";

const lazy = {};

ChromeUtils.defineESModuleGetters(lazy, {
  NLP: "resource://gre/modules/NLP.sys.mjs",
  MLEngineParent: "resource://gre/actors/MLEngineParent.sys.mjs",
  MultiProgressAggregator: "chrome://global/content/ml/Utils.sys.mjs",
  Progress: "chrome://global/content/ml/Utils.sys.mjs",
});

const LATEST_MODEL_REVISION = "latest";

// Methods for suggesting tabs that are similar to current tab
export const SUGGEST_OTHER_TABS_METHODS = {
  KMEANS_WITH_ANCHOR: "KMEANS_WITH_ANCHOR",
  NEAREST_NEIGHBOR: "NEAREST_NEIGHBOR",
  LOGISTIC_REGRESSION: "LOGISTIC_REGRESSION",
};

XPCOMUtils.defineLazyPreferenceGetter(
  lazy,
  "suggestOtherTabsMethod",
  "browser.tabs.groups.smart.suggestOtherTabsMethod"
);

XPCOMUtils.defineLazyPreferenceGetter(
  lazy,
  "topicModelRevision",
  "browser.tabs.groups.smart.topicModelRevision"
);

XPCOMUtils.defineLazyPreferenceGetter(
  lazy,
  "embeddingModelRevision",
  "browser.tabs.groups.smart.embeddingModelRevision"
);

XPCOMUtils.defineLazyPreferenceGetter(
  lazy,
  "nearestNeighborThresholdInt",
  "browser.tabs.groups.smart.nearestNeighborThresholdInt"
);

const EMBED_TEXT_KEY = "combined_text";
export const CLUSTER_METHODS = {
  KMEANS: "KMEANS",
};

// Methods for finding similar items for an existing cluster
export const ANCHOR_METHODS = {
  DRIFT: "DRIFT", // We let k-means clustering run, and find the cluster with the most anchor items
  FIXED: "FIXED", // We always group with the anchor items in the 0 cluster, and never let them be reassinged
};

// Methods for finding ignoring other groups that were already grouped
export const PREGROUPED_HANDLING_METHODS = {
  EXCLUDE: "EXCLUDE", // We let k-means clustering run, and find the cluster with the most anchor items
  IGNORE: "IGNORE", // We always group with the anchor items in the 0 cluster, and never let them be reassinged
};

const EXPECTED_TOPIC_MODEL_OBJECTS = 6;
const EXPECTED_EMBEDDING_MODEL_OBJECTS = 4;

export const DIM_REDUCTION_METHODS = {};
const MISSING_ANCHOR_IN_CLUSTER_PENALTY = 0.2;
const MAX_NN_GROUPED_TABS = 4;
const MAX_SUGGESTED_TABS = 10;

const DISSIMILAR_TAB_LABEL = "none";
const ADULT_TAB_LABEL = "adult content";
const LABELS_TO_EXCLUDE = [DISSIMILAR_TAB_LABEL, ADULT_TAB_LABEL];

const ML_TASK_FEATURE_EXTRACTION = "feature-extraction";
const ML_TASK_TEXT2TEXT = "text2text-generation";

const LABEL_REASONS = {
  DEFAULT: "DEFAULT",
  LOW_CONFIDENCE: "LOW_CONFIDENCE",
  EXCLUDE: "EXCLUDE",
  ERROR: "ERROR",
};

const SMART_TAB_GROUPING_CONFIG = {
  embedding: {
    dtype: "q8",
    timeoutMS: 2 * 60 * 1000, // 2 minutes
    taskName: ML_TASK_FEATURE_EXTRACTION,
    featureId: "smart-tab-embedding",
  },
  topicGeneration: {
    dtype: "q8",
    timeoutMS: 2 * 60 * 1000, // 2 minutes
    taskName: ML_TASK_TEXT2TEXT,
    featureId: "smart-tab-topic",
  },
  dataConfig: {
    titleKey: "label",
    descriptionKey: "description",
  },
  clustering: {
    dimReductionMethod: null, // Not completed.
    clusterImplementation: CLUSTER_METHODS.KMEANS,
    clusteringTriesPerK: 3,
    anchorMethod: ANCHOR_METHODS.FIXED,
    pregroupedHandlingMethod: PREGROUPED_HANDLING_METHODS.EXCLUDE,
    pregroupedSilhouetteBoost: 2, // Relative weight of the cluster's score and all other cluster's combined
    suggestOtherTabsMethod: SUGGEST_OTHER_TABS_METHODS.NEAREST_NEIGHBOR,
  },
};

// these parameters were generated by training a logistic regression
// model on synthetic data. see https://github.com/mozilla/smart-tab-grouping
// for more info
const LOGISTIC_REGRESSION_PARAMS = {
  TITLE_WITH_GROUP_NAME: {
    GROUP_SIMILARITY_WEIGHT: 6.76420017,
    TITLE_SIMILARITY_WEIGHT: 2.95779555,
    INTERCEPT: -3.06862155,
    THRESHOLD: 0.45,
  },
  TITLE_ONLY: {
    GROUP_SIMILARITY_WEIGHT: 0,
    TITLE_SIMILARITY_WEIGHT: 2.50596721,
    INTERCEPT: -0.54293376,
    THRESHOLD: 0.6,
  },
};

const TAB_URLS_TO_EXCLUDE = [
  "about:newtab",
  "about:home",
  "about:privatebrowsing",
  "chrome://browser/content/blanktab.html",
  "about:firefoxview",
];

/**
 * For a given set of clusters represented by indices, returns the index of the cluster
 * that has the most anchor items inside it.
 *
 * An anhor item is an index that represents the index to a tab that is already grouped and in
 * the cluster we're interested in finding more items for.
 *
 * @param {number[][]} groupIndices - Array of clusters represented as arrays of indices.
 * @param {number[]} anchorItems - Array of anchor item indices.
 * @returns {{anchorClusterIndex: number, numAnchorItemsInCluster: number}} Index of best cluster and the number of anchor items.
 */
export function getBestAnchorClusterInfo(groupIndices, anchorItems) {
  const anchorItemSet = new Set(anchorItems);
  const numItemsList = groupIndices.map(g =>
    g.reduce(
      (cur, itemIndex) => (anchorItemSet.has(itemIndex) ? cur + 1 : cur),
      0
    )
  );
  const anchorClusterIndex = numItemsList.indexOf(Math.max(...numItemsList));
  const numAnchorItemsInCluster = numItemsList[anchorClusterIndex];
  return { anchorClusterIndex, numAnchorItemsInCluster };
}

export class SmartTabGroupingManager {
  /**
   * Creates the SmartTabGroupingManager object.
   * @param {object} config configuration options
   */
  constructor(config) {
    this.config = config || SMART_TAB_GROUPING_CONFIG;
  }

  /**
   *
   * @param {MLEngine} engine the engine to check
   * @return {boolean} true if the engine has not been initialized or closed
   */
  static isEngineClosed(engine) {
    return !engine || engine?.engineStatus === "closed";
  }

  /**
   * Initializes the embedding engine by running a test request
   * This helps remove the init latency
   */
  async initEmbeddingEngine() {
    if (!SmartTabGroupingManager.isEngineClosed(this.embeddingEngine)) {
      return;
    }
    try {
      this.embeddingEngine = await this._createMLEngine(this.config.embedding);
      const request = {
        args: ["Test"],
        options: { pooling: "mean", normalize: true },
      };
      this.embeddingEngine.run(request);
    } catch (e) {}
  }

  /**
   * Generates suggested tabs for an existing or provisional group
   * @param {object} group active group we are adding tabs to
   * @param {array} tabs list of tabs from gbrowser, some of which may be grouped in other groups
   * @returns a list of suggested new tabs. If no new tabs are suggested an empty list is returned.
   */
  async smartTabGroupingForGroup(group, tabs) {
    // Add tabs to suggested group
    const groupTabs = group.tabs;
    const allTabs = tabs.filter(tab => {
      // Don't include tabs already pinned
      if (tab.pinned) {
        return false;
      }
      if (!tab?.linkedBrowser?.currentURI?.spec) {
        return false;
      }
      return true;
    });

    // find tabs that are part of the group
    const groupIndices = groupTabs
      .map(a => allTabs.indexOf(a))
      .filter(a => a >= 0);

    // find tabs that are part of other groups
    const alreadyGroupedIndices = allTabs
      .map((t, i) => (t.group ? i : -1))
      .filter(a => a >= 0);

    let suggestedTabs;
    switch (lazy.suggestOtherTabsMethod) {
      case SUGGEST_OTHER_TABS_METHODS.KMEANS_WITH_ANCHOR:
        suggestedTabs = await this.generateClusters(
          allTabs,
          null,
          null,
          null,
          groupIndices,
          alreadyGroupedIndices
        ).then(clusters => {
          if (!clusters) {
            return [];
          }
          const targetCluster = clusters.clusterRepresentations.find(c =>
            groupTabs.some(g => c.tabs.includes(g))
          );
          if (targetCluster) {
            // Return only tabs not already grouped
            return targetCluster.tabs.filter(t => !t.group);
          }
          return [];
        });
        break;
      case SUGGEST_OTHER_TABS_METHODS.LOGISTIC_REGRESSION:
        suggestedTabs = await this.findSimilarTabsLogisticRegression({
          allTabs,
          groupedIndices: groupIndices,
          alreadyGroupedIndices,
          groupLabel: group?.label,
        });
        break;
      case SUGGEST_OTHER_TABS_METHODS.NEAREST_NEIGHBOR:
      default:
        // find nearest neighbors to current group
        suggestedTabs = await this.findNearestNeighbors({
          allTabs,
          groupedIndices: groupIndices,
          alreadyGroupedIndices,
          groupLabel: group?.label,
        });
    }
    return suggestedTabs.slice(0, MAX_SUGGESTED_TABS);
  }

  /**
   * Get tabs that need to be included in suggestions
   * @param {array} allTabs all tabs that are part of the window
   * @param {array} groupedIndices indices of tabs that are already part of the group
   * @param {array} alreadyGroupedIndices indices of tabs that are part of other groups
   * @returns {array} tabs indices to be considered for suggestions
   */
  getTabsToSuggest(allTabs, groupedIndices, alreadyGroupedIndices) {
    // tabs to be excluded
    // indices of all tabs that should be excluded (with duplicates)
    const tabURLIndicesToExclude = allTabs
      .map((at, index) => (TAB_URLS_TO_EXCLUDE.includes(at.url) ? index : -1))
      .filter(index => index !== -1);
    const excludedTabIndices = [
      ...groupedIndices,
      ...alreadyGroupedIndices,
      ...tabURLIndicesToExclude,
    ];

    // tabs to be included
    return allTabs
      .map((_, index) => index)
      .filter(i => !excludedTabIndices.includes(i));
  }

  /*
   * Generates similar tabs a grouped list of tabs
   * @param {array} allTabs all tabs that are part of the window
   * @param {array} groupedIndices indices of tabs that are already part of the group
   * @param {array} alreadyGroupedIndices indices of tabs that are part of other groups
   * @param {string} groupLabel name of group if present
   * @param {number} threshold for nearest neighbor similarity
   * @returns a list of suggested tabs that are similar to the groupedIndices tabs
   */
  async findNearestNeighbors({
    allTabs,
    groupedIndices,
    alreadyGroupedIndices,
    groupLabel = "",
    thresholdMills = lazy.nearestNeighborThresholdInt,
    precomputedEmbeddings = [],
    depth = 0,
  }) {
    // get embeddings for all the tabs
    const tabData = await this._prepareTabData(allTabs);
    let embeddings = precomputedEmbeddings;
    if (precomputedEmbeddings.length === 0) {
      embeddings = await this._generateEmbeddings(
        tabData.map((td, index) => {
          let text = SmartTabGroupingManager.preprocessText(td[EMBED_TEXT_KEY]);
          // augment with group name if it's present
          if (groupLabel && groupedIndices.includes(index)) {
            text = `${groupLabel.slice(0, 100)}. ${text}`;
          }
          return text;
        })
      );
    }

    // tabs that need to be assigned after filtering
    const tabsToAssignIndices = this.getTabsToSuggest(
      tabData,
      groupedIndices,
      alreadyGroupedIndices
    );

    let closestTabs = [];
    const similarTabsIndices = [];
    for (let i = 0; i < tabsToAssignIndices.length; i++) {
      let closestScore = null;
      for (
        let j = 0;
        j < Math.min(groupedIndices.length, MAX_NN_GROUPED_TABS);
        j++
      ) {
        const cosineSim = cosSim(
          embeddings[tabsToAssignIndices[i]],
          embeddings[groupedIndices[j]]
        );
        if (!closestScore || cosineSim > closestScore) {
          closestScore = cosineSim;
        }
      }
      // threshold could also be set via a nimbus experiment, in which case
      // it will be an int <= 1000
      if (closestScore > thresholdMills / 1000) {
        closestTabs.push([allTabs[tabsToAssignIndices[i]], closestScore]);
        similarTabsIndices.push(tabsToAssignIndices[i]);
      }
    }
    closestTabs.sort((a, b) => b[1] - a[1]);
    closestTabs = closestTabs.map(t => t[0]);
    // recurse once if the initial call only had a single tab
    // and we found at least 1 similar tab - this improves recall
    if (groupedIndices.length === 1 && !!closestTabs.length && depth === 1) {
      const recurseSimilarTabs = await this.findNearestNeighbors({
        allTabs,
        groupedIndices: similarTabsIndices,
        alreadyGroupedIndices: alreadyGroupedIndices.concat(groupedIndices),
        groupLabel,
        thresholdMills,
        precomputedEmbeddings: embeddings,
        depth: depth - 1,
      });
      closestTabs = closestTabs.concat(recurseSimilarTabs);
    }
    return closestTabs;
  }

  /**
   * Calculates the average similarity between the anchor embeddings and the candidate embeddings
   * @param {list[Number]} anchorEmbeddings title embeddings for the anchor tabs
   * @param {list[Number]} candidateEmbeddings title embeddings for the candidate tabs
   */
  getAverageSimilarity(anchorEmbeddings, candidateEmbeddings) {
    let averageSimilarities = [];
    for (let candidate_embedding of candidateEmbeddings) {
      let averageSimilarity = 0;
      for (let anchor_embedding of anchorEmbeddings) {
        averageSimilarity += cosSim(candidate_embedding, anchor_embedding);
      }
      averageSimilarities.push(averageSimilarity / anchorEmbeddings.length);
    }
    return averageSimilarities;
  }

  /**
   * Calculates the sigmoid value of the input
   *
   * @param {Number} z
   * @return {Number}
   */
  sigmoid(z) {
    return 1 / (1 + Math.exp(-z));
  }

  /**
   * Calculates the probability using the linear combination of the parameters
   *
   * @param {Number} groupSimilarity how similar a candidate tab is to the group name
   * @param {Number} titleSimilarity how similar a candidate tab is to the anchors
   * @param {Object} params the logistic regression weights assigned to each parameter
   * @return {Number}
   */
  calculateProbability(groupSimilarity, titleSimilarity, params) {
    return this.sigmoid(
      groupSimilarity * params.GROUP_SIMILARITY_WEIGHT +
        titleSimilarity * params.TITLE_SIMILARITY_WEIGHT +
        params.INTERCEPT
    );
  }

  /**
   * Calculates the probabilities given two lists of the same length
   *
   * @param {list[Number]} groupSimilarities cosine similarity between the candidate tabs and the group name
   * @param {list[Number]} titleSimilarities average cosine similarity between the candidate tabs and anchors
   * @return {list[Number]} probabilities for each candidate tab
   */
  calculateAllProbabilities(groupSimilarities, titleSimilarities) {
    const hasGroupSimilarity = Boolean(groupSimilarities);
    let probabilities = [];
    for (let i = 0; i < titleSimilarities.length; i++) {
      probabilities.push(
        this.calculateProbability(
          hasGroupSimilarity ? groupSimilarities[i] : 0,
          titleSimilarities[i],
          hasGroupSimilarity
            ? LOGISTIC_REGRESSION_PARAMS.TITLE_WITH_GROUP_NAME
            : LOGISTIC_REGRESSION_PARAMS.TITLE_ONLY
        )
      );
    }
    return probabilities;
  }

  /**
   * Generates similar tabs to a grouped list of tabs using a logistic regression "model"
   *
   * @param {array} allTabs all tabs that are part of the window
   * @param {array} groupedIndices indices of tabs that are already part of the group
   * @param {array} alreadyGroupedIndices indices of tabs that are part of other groups
   * @param {string} groupLabel name of group if present
   */
  async findSimilarTabsLogisticRegression({
    allTabs,
    groupedIndices,
    alreadyGroupedIndices,
    groupLabel = "",
  }) {
    const tabData = await this._prepareTabData(allTabs);
    const candidateIndices = this.getTabsToSuggest(
      tabData,
      groupedIndices,
      alreadyGroupedIndices
    );

    const candidateTabsData = candidateIndices.map(ci => allTabs[ci]);
    const candidateTabsPrep = await this._prepareTabData(candidateTabsData);

    const anchorTabsPrep = groupedIndices
      .map(gi => tabData[gi])
      .slice(0, MAX_NN_GROUPED_TABS);

    // generate embeddings for both anchor and candidate titles
    const titleEmbeddings = await this._generateEmbeddings(
      anchorTabsPrep
        .concat(candidateTabsPrep)
        .map(tab => SmartTabGroupingManager.preprocessText(tab[EMBED_TEXT_KEY]))
    );

    let groupEmbedding;
    let groupSimilarities;
    if (groupLabel) {
      groupEmbedding = await this._generateEmbeddings([groupLabel]);
      // calculate similarity between the group and the candidate tabs if group name is present
      groupSimilarities = this.getAverageSimilarity(
        groupEmbedding,
        titleEmbeddings.slice(anchorTabsPrep.length)
      );
    }

    // calculate the similarity between the anchors and candidate titles
    const titleSimilarities = this.getAverageSimilarity(
      titleEmbeddings.slice(0, anchorTabsPrep.length),
      titleEmbeddings.slice(anchorTabsPrep.length)
    );

    const candidateProbabilities = this.calculateAllProbabilities(
      groupSimilarities,
      titleSimilarities
    );

    // get proper params depending on group name availability
    const probabilityThreshold = groupEmbedding
      ? LOGISTIC_REGRESSION_PARAMS.TITLE_WITH_GROUP_NAME.THRESHOLD
      : LOGISTIC_REGRESSION_PARAMS.TITLE_ONLY.THRESHOLD;

    return (
      candidateTabsData
        // combine candidate tabs with corresponding probabilities
        .map((ct, index) => ({
          ct,
          prob: candidateProbabilities[index],
        }))
        // only keep those that are within the probability threshold
        .filter(item => item.prob >= probabilityThreshold)
        // ensure the highest probability candidates come first in the list
        .sort((a, b) => b.prob - a.prob)
        // keep the tabs only
        .map(item => item.ct)
    );
  }

  /**
   * This function will terminate a grouping or label generation in progress
   * It is currently not implemented.
   */
  terminateProcess() {
    // TODO - teminate AI processes, This method will be
    // called when tab grouping panel is closed.
  }

  /**
   * Changes the clustering method. Must be one of supported methods.
   * @param {string} method Name of method
   */
  setClusteringMethod(method) {
    if (!(method in CLUSTER_METHODS)) {
      throw new Error(`Clustering method ${method} not supported`);
    }
    this.config.clustering.clusterImplementation = method;
  }

  /**
   * Set the technique for clustering when certain tabs are already assigned to groups
   *
   * @param {string} method which is one of ANCHOR_METHODS
   */
  setAnchorMethod(method) {
    if (!(method in ANCHOR_METHODS)) {
      throw new Error(`Clustering anchor method ${method} not supported`);
    }
    this.config.clustering.anchorMethod = method;
  }

  setSilBoost(boost) {
    this.config.clustering.pregroupedSilhouetteBoost = boost;
  }

  /**
   * Sets method to reduce dimensionality of embeddings prior to clustering
   * @param {string} method Name of method
   */
  setDimensionReductionMethod(method) {
    if (method && !(method in DIM_REDUCTION_METHODS)) {
      throw new Error(`Dimension reduction method ${method} not supported`);
    }
    this.config.clustering.dimReductionMethod = method;
  }

  /**
   * Sets the field name of the title of a page to be used when clustering or generating embeddings
   * This is useful when clustering test data that is not a tab object
   * @param {string} titleKey KEY FOR THE TITLE
   */
  setDataTitleKey(titleKey) {
    this.config.dataConfig.titleKey = titleKey;
  }

  /**
   * Logs to the appropriate place for debugging. Console for now
   * @param {string} msg Message to log
   * @param {boolean} useDescription Whether to add description to the final text
   */
  log(_msg) {}

  /**
   * Prepares data to be used by the ml models
   * @param {Object[]} tabList list of tabs in the current window
   * @param {boolean} useDescription whether we should combined the title and description
   * @return {Promise<*[Object]>}
   * @private
   */
  async _prepareTabData(tabList, useDescription = false) {
    const titleKey = this.config.dataConfig.titleKey;
    const descriptionKey = this.config.dataConfig.descriptionKey;
    const structuredData = [];
    for (let tab of tabList) {
      const description =
        useDescription && descriptionKey && tab[descriptionKey];

      let textToEmbed;
      if (description) {
        textToEmbed = tab[titleKey] + " " + description;
      } else {
        textToEmbed = tab[titleKey] || "Unknown";
      }

      structuredData.push({
        [EMBED_TEXT_KEY]: textToEmbed,
        title: tab[titleKey],
        description,
        url: tab?.linkedBrowser?.currentURI?.spec,
      });
    }
    return structuredData;
  }

  /**
   * Get updated config for the ml engine
   *
   * @param {object} initData
   * @param {string} featureId
   * @return {*}
   */
  static getUpdatedInitData(initData, featureId) {
    // we're setting a specific modelRevision through about:config or Nimbus
    if (
      featureId === SMART_TAB_GROUPING_CONFIG.topicGeneration.featureId &&
      lazy.topicModelRevision !== LATEST_MODEL_REVISION
    ) {
      initData.modelRevision = lazy.topicModelRevision;
    } else if (
      featureId === SMART_TAB_GROUPING_CONFIG.embedding.featureId &&
      lazy.embeddingModelRevision !== LATEST_MODEL_REVISION
    ) {
      initData.modelRevision = lazy.embeddingModelRevision;
    }
    return initData;
  }

  /**
   * Creates an ML engine for a given config.
   * @param {*} engineConfig
   * @param {function} progressCallback
   * @returns MLEngine
   */
  async _createMLEngine(engineConfig, progressCallback) {
    const {
      featureId,
      engineId,
      dtype,
      taskName,
      timeoutMS,
      modelId,
      modelRevision,
    } = engineConfig;
    let initData = {
      featureId,
      engineId,
      dtype,
      taskName,
      timeoutMS,
      modelId,
      modelRevision,
    };

    initData = SmartTabGroupingManager.getUpdatedInitData(initData, featureId);
    return await createEngine(initData, progressCallback);
  }

  /**
   * Generates embeddings from a list of tab data structures
   * @param  tabList List of tabs with label (title) and description keys
   * @returns {Promise<*[]>} List of embeddings (2d array)
   * @private
   */
  async _generateEmbeddings(textToEmbedList) {
    const inputData = {
      inputArgs: textToEmbedList,
      runOptions: {
        pooling: "mean",
        normalize: true,
      },
    };

    if (SmartTabGroupingManager.isEngineClosed(this.embeddingEngine)) {
      this.embeddingEngine = await this._createMLEngine(this.config.embedding);
    }
    const request = {
      args: [inputData.inputArgs],
      options: inputData.runOptions,
    };
    return await this.embeddingEngine.run(request);
  }

  /**
   * Clusters in desired methods
   * based on the config of the class
   * @param tabList List of tabs as array
   * @param docEmbeddings Precomputed embeddings for the Tab as two dimensional array
   * @param k Desired number of clusters. Tries a range of sizes if 0.
   * @param {function} randomFunc Optional seeded random number generator for testing
   * @returns {SmartTabGroupingResult}
   * @private
   */
  _clusterEmbeddings({
    tabs,
    embeddings,
    k,
    randomFunc,
    anchorIndices,
    alreadyGroupedIndices = [],
  }) {
    let allItems;

    const freezeAnchorsInZeroCluster =
      anchorIndices &&
      this.config.clustering.anchorMethod == ANCHOR_METHODS.FIXED;

    const dimReductionMethod = this.config.clustering.dimReductionMethod;
    switch (dimReductionMethod) {
      default:
        //  Dimensionality reduction support is landing very soon.
        break;
    }
    k = k || 0;
    let startK = k;
    let endK = k + 1;
    if (!k) {
      startK = 2;
      // Find a reasonable max # of clusters
      endK =
        Math.min(
          Math.floor(Math.log(embeddings.length) * 2.0),
          embeddings.length
        ) + 1;
    }
    let bestResult;
    let bestResultSilScore = -100.0;
    let bestResultCenterCluster = 0;

    const clusteringMethod = this.config.clustering.clusterImplementation;
    const clusteringTriesPerK = this.config.clustering.clusteringTriesPerK;
    for (let curK = startK; curK < endK; curK++) {
      let bestItemsForK;
      let bestInertiaForK = 500000000000;
      for (let j = 0; j < clusteringTriesPerK; j++) {
        switch (clusteringMethod) {
          case CLUSTER_METHODS.KMEANS:
            allItems = kmeansPlusPlus({
              data: embeddings,
              k: curK,
              maxIterations: 0,
              randomFunc,
              anchorIndices,
              preassignedIndices:
                this.config.clustering.pregroupedHandlingMethod ===
                PREGROUPED_HANDLING_METHODS.EXCLUDE
                  ? alreadyGroupedIndices
                  : [],
              freezeAnchorsInZeroCluster,
            });
            break;
          default:
            throw Error("Clustering implementation not supported");
        }
        const tempResult = new SmartTabGroupingResult({
          indices: allItems,
          embeddings,
          config: this.config,
        });
        const inertia = tempResult.getCentroidInertia();
        if (inertia < bestInertiaForK) {
          bestInertiaForK = inertia;
          bestItemsForK = tempResult;
        }
      }
      const silScores = silhouetteCoefficients(
        embeddings,
        bestItemsForK.indices
      );

      if (
        freezeAnchorsInZeroCluster &&
        this.config.clustering.pregroupedSilhouetteBoost > 0
      ) {
        // Boost silhouette score of target cluster when we are grouping around an existing cluster
        // pregroupedSilhouetteBoost indicates the relative weight of the cluster's score and all other cluster's combined
        silScores[0] *= this.config.clustering.pregroupedSilhouetteBoost;
      }

      let avgSil = silScores.reduce((p, c) => p + c, 0) / silScores.length;
      let curAnchorCluster = 0;
      if (anchorIndices && !freezeAnchorsInZeroCluster) {
        const { anchorClusterIndex, numAnchorItemsInCluster } =
          getBestAnchorClusterInfo(bestItemsForK.indices, anchorIndices);
        curAnchorCluster = anchorClusterIndex;
        const penalty =
          (MISSING_ANCHOR_IN_CLUSTER_PENALTY *
            (anchorIndices.length - numAnchorItemsInCluster)) /
          anchorIndices.length;
        avgSil -= penalty;
      }
      if (avgSil > bestResultSilScore) {
        bestResultSilScore = avgSil;
        bestResult = bestItemsForK.indices;
        bestResultCenterCluster = curAnchorCluster;
      }
    }
    const result = new SmartTabGroupingResult({
      indices: bestResult,
      tabs,
      embeddings,
      config: this.config,
    });
    if (anchorIndices) {
      result.setAnchorClusterIndex(
        freezeAnchorsInZeroCluster ? 0 : bestResultCenterCluster
      ); // In our k-means clustering implementation anchor cluster is always first
      if (!freezeAnchorsInZeroCluster) {
        result.adjustClusterForAnchors(anchorIndices);
      }
    }
    return result;
  }

  /**
   * Generate a label for tabs in a group created by the user
   *
   * @param tabs tabs that are currently in the group
   * @param otherTabs tabs in the window not part of the group
   * @return {Promise<null|string|string|*>}
   */
  async getPredictedLabelForGroup(tabs, otherTabs) {
    const clusters = this.createStaticCluster(tabs);
    const otherClusters = this.createStaticCluster(otherTabs);
    let predictedLabel;
    try {
      // function below modifies "clusters" object
      await this.generateGroupLabels(clusters, otherClusters);
      predictedLabel = clusters.clusterRepresentations[0].predictedTopicLabel;
    } catch (e) {
      this.labelReason = LABEL_REASONS.ERROR;
      predictedLabel = "";
    }
    return predictedLabel;
  }

  /**
   * Generates clusters for a given list of tabs using precomputed embeddings or newly generated ones.
   *
   * @param {Object[]} tabList - List of tab objects to be clustered.
   * @param {number[][]} [precomputedEmbeddings] - Precomputed embeddings for tab titles and descriptions.
   * @param {number} numClusters - Number of clusters to form.
   * @param {Function} randFunc - Random function used for clustering initialization.
   * @param {number[]} [anchorIndices=[]] - Indices of anchor tabs that should be prioritized in clustering.
   * @param {number[]} [alreadyGroupedIndices=[]] - Indices of tabs that are already assigned to groups.
   * @returns {SmartTabGroupingResult} - The best clustering result based on centroid inertia.
   */
  async generateClusters(
    tabList,
    precomputedEmbeddings,
    numClusters,
    randFunc,
    anchorIndices = [],
    alreadyGroupedIndices = []
  ) {
    numClusters = numClusters ?? 0;
    const structuredData = await this._prepareTabData(tabList);

    // embeddings for title and description
    if (precomputedEmbeddings) {
      this.docEmbeddings = precomputedEmbeddings;
    } else {
      this.docEmbeddings = await this._generateEmbeddings(
        structuredData.map(a => a[EMBED_TEXT_KEY])
      );
    }
    let bestResultCluster;
    let bestResultDistance = 50000000.0;

    const NUM_RUNS = 1;
    for (let i = 0; i < NUM_RUNS; i++) {
      const curResult = this._clusterEmbeddings({
        tabs: tabList,
        embeddings: this.docEmbeddings,
        k: numClusters,
        randomFunc: randFunc,
        anchorIndices,
        alreadyGroupedIndices,
      });
      const distance = curResult.getCentroidInertia();
      if (distance < bestResultDistance) {
        bestResultDistance = distance;
        bestResultCluster = curResult;
      }
    }
    return bestResultCluster;
  }

  /**
   * Create static cluster from a list of tabs. A single tab is Ok. Returns null for 0 tabs
   * @param tabs
   * @returns {SmartTabGroupingResult} groupingResult
   */
  createStaticCluster(tabs) {
    if (!tabs) {
      return null;
    }

    return new SmartTabGroupingResult({
      indices: [Array.from({ length: tabs.length }, (_, i) => i)],
      tabs,
      config: this.config,
    });
  }

  /***
   * Utility function that loads all required engines for Smart Tab Grouping and any dependent models
   * @param {(progress: { percentage: number }) => void} progressCallback callback function to call.
   * Callback passes a dict with percentage indicating best effort 0.0-100.0 progress in model download.
   */
  async preloadAllModels(progressCallback) {
    let previousProgress = -1;
    const expectedObjects =
      EXPECTED_TOPIC_MODEL_OBJECTS + EXPECTED_EMBEDDING_MODEL_OBJECTS;
    // TODO - Find a way to get these fields. Add as a transformers js callback or within remotesettings

    const UPDATE_THRESHOLD_PERCENTAGE = 0.5;
    const ONE_MB = 1024 * 1024;
    const START_THRESHOLD_BYTES = ONE_MB * 0.2;

    const mutliProgressAggregator = new lazy.MultiProgressAggregator({
      progressCallback: ({ progress, totalLoaded, metadata }) => {
        if (totalLoaded < START_THRESHOLD_BYTES) {
          progress = 0.0;
        } else {
          const numObjSeen = metadata.totalObjectsSeen || 0;
          if (numObjSeen > 0 && numObjSeen < expectedObjects) {
            // When starting to download we may still be getting configs and not have all the data
            progress *= numObjSeen / expectedObjects;
          }
          if (progress > 100) {
            progress = 100;
          }
        }
        if (
          Math.abs(previousProgress - progress) > UPDATE_THRESHOLD_PERCENTAGE
        ) {
          // Update only once changes are above a threshold to avoid throttling the UI with events.
          progressCallback({
            percentage: progress,
          });
          previousProgress = progress;
        }
      },
      watchedTypes: [
        lazy.Progress.ProgressType.DOWNLOAD,
        lazy.Progress.ProgressType.LOAD_FROM_CACHE,
      ],
    });

    const [topicEngine, embeddingEngine] = await Promise.all([
      this._createMLEngine(
        this.config.topicGeneration,
        mutliProgressAggregator?.aggregateCallback.bind(
          mutliProgressAggregator
        ) || null
      ),
      this._createMLEngine(
        this.config.embedding,
        mutliProgressAggregator?.aggregateCallback.bind(
          mutliProgressAggregator
        ) || null
      ),
    ]);
    this.topicEngine = topicEngine;
    this.embeddingEngine = embeddingEngine;
  }

  /**
   * Generate model input from keywords and documents
   * @param {string []} keywords
   * @param {string []} documents
   */
  createModelInput(keywords, documents) {
    if (!keywords || keywords.length === 0) {
      return `Topic from keywords: titles: \n${documents.join(" \n")}`;
    }
    return `Topic from keywords: ${keywords.join(", ")}. titles: \n${documents.join(" \n")}`;
  }

  /**
   * One artifact of the LLM output is that sometimes words are duplicated
   * This function cuts the phrase when it sees the first duplicate word.
   * Handles simple singluar / plural duplicates (-s only).
   * @param {string} phrase Input phrase
   * @returns {string} phrase cut before any duplicate word
   */
  static cutAtDuplicateWords(phrase) {
    if (!phrase.length) {
      return phrase;
    }
    const wordsSet = new Set();
    const wordList = phrase.split(" ");
    for (let i = 0; i < wordList.length; i++) {
      let baseWord = wordList[i].toLowerCase();
      if (baseWord.length > 3) {
        if (baseWord.slice(-1) === "s") {
          baseWord = baseWord.slice(0, -1);
        }
      }
      if (wordsSet.has(baseWord)) {
        // We are seeing a baseWord word. Exit with just the words so far and don't
        // add any new words
        return wordList.slice(0, i).join(" ");
      }
      wordsSet.add(baseWord);
    }
    return phrase; // return original phrase
  }

  /**
   * Removes trailing domain-related text such as '... - Mail' or '... | News'
   * If there's not enough information remaining after, we keep the text as is
   * @param {string} text tab title with potential domain information
   * @return {string}
   */
  static preprocessText(text) {
    // Matches 'xyz - Domain' or 'xyz | Domain'
    // with a space before and after delimiter
    // or if there are multiple delimiters next to each other
    const delimiters = /(?<=\s)[|–-]+(?=\s)/;
    const splitText = text.split(delimiters);

    // ensure there's enough info without the last element
    const hasEnoughInfo =
      !!splitText.length && splitText.slice(0, -1).join(" ").length > 5;

    // domain related texts are usually shorter, this takes care of the most common cases
    const isPotentialDomainInfo =
      splitText.length > 1 && splitText[splitText.length - 1].length < 20;

    // If both conditions are met, remove the last chunk, filter out empty strings,
    // join on space, trim, and lowercase
    if (hasEnoughInfo && isPotentialDomainInfo) {
      return splitText
        .slice(0, -1) // everything except the last element
        .map(t => t.trim())
        .filter(Boolean) // remove empty strings
        .join(" ") // join with spaces
        .trim(); // remove leading/trailing spaces
    }

    // Otherwise, just return the text
    return text;
  }

  /**
   * Postprocessing of raw output from Topic Model ML Engine
   * @param {string | undefined} topic Raw topic phrase from topic model or undefined in case of an error
   */
  processTopicModelResult(topic) {
    let basicResult = (topic || "").trim();
    if (!basicResult) {
      this.labelReason = LABEL_REASONS.LOW_CONFIDENCE;
    }
    if (LABELS_TO_EXCLUDE.includes(basicResult.toLowerCase())) {
      this.labelReason = LABEL_REASONS.EXCLUDE;
      return "";
    }
    return SmartTabGroupingManager.cutAtDuplicateWords(basicResult);
  }

  /**
   * Add titles to a cluster in a SmartTabGroupingResult using generative tehniques
   * Currently this function only works with a single target group, and a separate
   * item that represents all other ungrouped tabs.
   *
   * In the future this may be updated to more generally find labels for a set of clusters.
   * @param {SmartTabGroupingResult} groupingResult The cluster we are generating the label for
   * @param {SmartTabGroupingResult} otherGroupingResult A 'made up' cluster representing all other tabs in the window
   */
  async generateGroupLabels(groupingResult, otherGroupingResult = null) {
    const { keywords, documents } =
      groupingResult.getRepresentativeDocsAndKeywords(
        otherGroupingResult
          ? otherGroupingResult.getRepresentativeDocuments()
          : []
      );
    const inputArgs = this.createModelInput(
      keywords ? keywords[0] : [],
      documents
    );
    const requestInfo = {
      inputArgs,
      runOptions: {
        max_length: 6,
      },
    };

    if (SmartTabGroupingManager.isEngineClosed(this.topicEngine)) {
      this.topicEngine = await this._createMLEngine(
        this.config.topicGeneration
      );
    }
    const request = {
      args: [requestInfo.inputArgs],
      options: requestInfo.runOptions,
    };
    const genLabelResults = await this.topicEngine.run(request);
    genLabelResults.forEach((genResult, genResultIndex) => {
      groupingResult.clusterRepresentations[
        genResultIndex
      ].predictedTopicLabel = this.processTopicModelResult(
        genResult.generated_text
      );
    });
  }

  getLabelReason() {
    return this.labelReason || LABEL_REASONS.DEFAULT;
  }

  /**
   * Generates glean metrics for ml smart tab label / topic.
   * This is currently called when the user saves or cancels the "suggest label" flow.
   *
   * @param {string} action "save" or "cancel"
   * @param {number} numTabsInGroup Number of tabs used to generate the label
   * @param {string} mlLabel ML generated label for the tab group
   * @param {string} userLabel User saved label for the tab group
   * @param {string} id The id of the group
   */
  async handleLabelTelemetry({
    action,
    numTabsInGroup,
    mlLabel,
    userLabel,
    id = "",
  }) {
    const { [ML_TASK_TEXT2TEXT]: topicEngineConfig } =
      await this.getEngineConfigs();
    const labelReason = this.getLabelReason();
    Glean.tabgroup.smartTabTopic.record({
      action,
      tabs_in_group: numTabsInGroup,
      ml_label_length: (mlLabel || "").length,
      user_label_length: (userLabel || "").length,
      levenshtein_distance: lazy.NLP.levenshtein(
        userLabel || "",
        mlLabel || ""
      ),
      model_revision: topicEngineConfig.modelRevision || "",
      id,
      label_reason: labelReason,
    });
    this.labelReason = LABEL_REASONS.DEFAULT;
  }

  /**
   * Generates glean metrics for ml smart tab label / topic.
   * This is currently called when the user saves or cancels the "suggest other tabs" flow
   *
   * @param {string} action "save" or "cancel"
   * @param {number} numTabsInWindow Number of tabs in the current window
   * @param {number} numTabsInGroup Number of tabs in the current group
   * @param {number} numTabsSuggested Number of tabs suggested by the model
   * @param {number} numTabsApproved Number of tabs approved by the user
   * @param {number} numTabsRemoved Number of tabs removed by the user
   * @param {string} id The id of the group
   */
  async handleSuggestTelemetry({
    action,
    numTabsInWindow,
    numTabsInGroup,
    numTabsSuggested,
    numTabsApproved,
    numTabsRemoved,
    id = "",
  }) {
    const { [ML_TASK_FEATURE_EXTRACTION]: embeddingEngineConfig } =
      await this.getEngineConfigs();
    Glean.tabgroup.smartTabSuggest.record({
      action,
      tabs_in_window: numTabsInWindow,
      tabs_in_group: numTabsInGroup,
      tabs_suggested: numTabsSuggested,
      tabs_approved: numTabsApproved,
      tabs_removed: numTabsRemoved,
      model_revision: embeddingEngineConfig.modelRevision || "",
      id,
    });
  }

  /**
   * Gets config that engine was initialized with
   *
   * @return {Promise<{"[ML_TASK_TEXT2TEXT]", "[ML_TASK_FEATURE_EXTRACTION]"}>}
   */
  async getEngineConfigs() {
    if (!this.topicEngineConfig) {
      this.topicEngineConfig = await lazy.MLEngineParent.getInferenceOptions(
        this.config.topicGeneration.featureId,
        this.config.topicGeneration.taskName
      );
    }
    if (!this.embeddingEngineConfig) {
      this.embeddingEngineConfig =
        await lazy.MLEngineParent.getInferenceOptions(
          this.config.embedding.featureId,
          this.config.embedding.taskName
        );
    }
    return {
      [ML_TASK_TEXT2TEXT]: this.topicEngineConfig,
      [ML_TASK_FEATURE_EXTRACTION]: this.embeddingEngineConfig,
    };
  }
}

export class SmartTabGroupingResult {
  #anchorClusterIndex = -1; // Index of cluster that has original items we're building clustering around, when building around an existing item.

  /**
   * Creates a result from indices and complete tab and embedding lists.
   * This may create some extra data for management later
   * @param indices indices of clusters (eg [[2,4], [1], [3]]_
   * @param tabItems 1D array of tabs
   * @param embeddingItems Two dimensional array of embeddings
   * @param config Cluster config
   */
  constructor({ indices = [], tabs, embeddings, config }) {
    this.embeddingItems = embeddings;
    this.config = config;
    this.indices = indices.filter(subArray => !!subArray.length); // Cleanup any empty clusters
    this.tabItems = tabs;
    this._buildClusterRepresentations();
  }

  /**
   * Builds list of ClusterRepresentations
   */
  _buildClusterRepresentations() {
    this.clusterRepresentations = this.indices.map(subClusterIndices => {
      const tabItemsMapped =
        this.tabItems && subClusterIndices.map(idx => this.tabItems[idx]);
      const embeddingItemsMapped =
        this.embeddingItems &&
        subClusterIndices.map(idx => this.embeddingItems[idx]);
      return new ClusterRepresentation({
        tabs: tabItemsMapped,
        embeddings: embeddingItemsMapped,
        config: this.config,
      });
    });
  }

  /**
   * Returns a list of documents for each cluster. Currently it is a list of documents picked
   * in no particular order.
   * @return {[strings]} Title and description that represent the cluster. (If no docs are in the class, then titles are returned)
   */
  getRepresentativeDocuments() {
    if (!this.documents) {
      this.documents = this.tabItems.map(
        t => t[this.config.dataConfig.titleKey]
      );
    }
    // set a limit of 10 for now
    return this.documents.slice(0, 10);
  }

  /**
   * Returns the keywords and documents for the cluster, computing if needed
   * Does not return keywods if only one document is passed to the function.
   * @param{string[]} otherDocuments other clusters that we'll compare against
   * @return keywords and documents that represent the cluster
   */
  getRepresentativeDocsAndKeywords(otherDocuments = []) {
    this.documents = this.getRepresentativeDocuments();
    if (!this.keywords) {
      const joinedDocs = this.documents.slice(0, 3).join(" ");
      const otherDocs = otherDocuments.join(" ");
      if (this.documents.length > 1) {
        const keywordExtractor = new KeywordExtractor();
        this.keywords = keywordExtractor.fitTransform([joinedDocs, otherDocs]);
      } else {
        this.keywords = [];
      }
    }
    return { keywords: this.keywords, documents: this.documents };
  }

  setAnchorClusterIndex(index) {
    this.#anchorClusterIndex = index;
  }

  /**
   * Get the cluster we originally are grouping around (finding additinoal item)
   * @returns ClusterRepresentation
   */
  getAnchorCluster() {
    if (this.#anchorClusterIndex === -1) {
      return null;
    }
    return this.clusterRepresentations[this.#anchorClusterIndex];
  }

  /**
   *   Given the indices that we were clustering around, make sure they are are all in the target grouping
   *   Our generic k-means clustering might have them in separate groups
   */
  adjustClusterForAnchors(anchorIndices) {
    if (!anchorIndices.length) {
      return;
    }
    const anchorSet = new Set(anchorIndices);
    for (let i = 0; i < this.indices.length; i++) {
      if (i === this.#anchorClusterIndex) {
        continue;
      }
      this.indices[i] = this.indices[i].filter(item => {
        if (anchorSet.has(item)) {
          this.indices[this.#anchorClusterIndex].push(item);
          return false;
        }
        return true;
      });
    }
    this._buildClusterRepresentations();
  }

  /**
   * Prints information about the cluster
   */
  printClusters() {
    for (let cluster of this.clusterRepresentations) {
      cluster.print();
    }
  }

  /**
   * Computes the inertia of the cluster which is the sum of square total distance.
   * @returns {number}
   */
  getCentroidInertia() {
    let runningTotalDistance = 0;
    this.clusterRepresentations.forEach(rep => {
      runningTotalDistance += rep.computeTotalSquaredCentroidDistance();
    });
    return runningTotalDistance;
  }

  /**
   * Converts a cluster representation to a flat list of tabs, with clusterID key in each
   * tab representing the id of the cluster it was part of.
   * @returns {[Object]}
   */
  _flatMapItemsInClusters() {
    return this.clusterRepresentations.reduce((result, clusterRep) => {
      const annotatedTabs = clusterRep.tabs.map(a => {
        let c = {};
        Object.assign(c, a);
        c.clusterID = clusterRep.clusterID;
        return c;
      });
      return result.concat(annotatedTabs);
    }, []);
  }

  /**
   * Get rand score which describes the accuracy versus a user labeled
   * annotation on the dataset. Requires the dataset to be labeled.
   * @param labelKey Key in the tabs that represent a unique label ID for the cluster.
   * @returns {number} The rand score.
   */
  getRandScore(labelKey = "annotatedLabel") {
    const combinedItems = this._flatMapItemsInClusters();
    return computeRandScore(combinedItems, "clusterID", labelKey);
  }

  /**
   * Get accuracy for a specific cluster
   * @param labelKey Key in the tabs that represent a unique label ID for the cluster.
   * @param clusterValue is the cluster we are comparing
   * @returns {number} The rand score.
   */
  getAccuracyStatsForCluster(labelKey = "annotatedLabel", clusterValue) {
    const combinedItems = this._flatMapItemsInClusters();

    let keyClusterId = combinedItems.find(
      a => a[labelKey] === clusterValue
    ).clusterID;

    let truePositives = 0,
      trueNegatives = 0,
      falseNegatives = 0,
      falsePositives = 0;

    combinedItems.forEach(item => {
      const sameLabel = item[labelKey] === clusterValue;
      const sameCluster = item.clusterID === keyClusterId;
      if (sameLabel && sameCluster) {
        truePositives++;
      }
      if (!sameLabel && !sameCluster) {
        trueNegatives++;
      }
      if (sameLabel && !sameCluster) {
        falseNegatives++;
      }
      if (!sameLabel && sameCluster) {
        falsePositives++;
      }
    });
    return getAccuracyStats({
      truePositives,
      trueNegatives,
      falsePositives,
      falseNegatives,
    });
  }
}

/**
 * Utility function to generate a random ID string
 * @param len Length of the string
 * @returns {string}
 */
function genHexString(len) {
  const hex = "0123456789ABCDEF";
  let output = "";
  for (let i = 0; i < len; ++i) {
    output += hex.charAt(Math.floor(Math.random() * hex.length));
  }
  return output;
}

class EmbeddingCluster {
  constructor({ tabs, embeddings, centroid }) {
    this.embeddings = embeddings;
    this.centroid =
      centroid || (embeddings && computeCentroidFrom2DArray(this.embeddings));
    this.tabs = tabs;
  }

  /**
   * @returns total sum euclidan squared distance of each item from cluster's centroid
   */
  computeTotalSquaredCentroidDistance() {
    let totalDistance = 0;
    if (this.embeddings.length === 0) {
      return 0;
    }
    this.embeddings.forEach(embedding => {
      totalDistance += euclideanDistance(this.centroid, embedding, true);
    });
    return totalDistance;
  }

  /**
   * Returns number of items in the cluster
   * @returns {int}
   */
  numItems() {
    return this.tabs.length;
  }
}

/**
 * Represents a single cluster with additional saved metadata
 */
export class ClusterRepresentation extends EmbeddingCluster {
  constructor({ tabs, embeddings, centroid, config }) {
    super({ tabs, embeddings, centroid });
    this.config = config;
    this.predictedTopicLabel = null;
    this.annotatedTopicLabel = null;
    this.userEditedTopicLabel = null;
    this.representativeText = null;
    this.keywords = null;
    this.documents = null;
    this.clusterID = genHexString(10);
  }

  /**
   * Returns the representative text for a cluster, computing it if needed
   */
  getRepresentativeText() {
    if (!this.representativeText) {
      this.representativeText = this._generateRepresentativeText();
    }
    return this.representativeText;
  }

  /**
   * Returns representative text for a cluster.
   * For this in initial implementation it simply returns title from a few tabs
   * @returns {string}
   * @private
   */
  _generateRepresentativeText() {
    let text = "";
    const titleKey = this.config.dataConfig.titleKey;
    for (const tab of this.tabs.slice(0, 3)) {
      text += `\n${tab[titleKey]}`;
    }
    return text;
  }

  print() {
    // Add console log for debugging
  }
}