125 lines
3.7 KiB
TypeScript
125 lines
3.7 KiB
TypeScript
import { stemmer } from "https://esm.sh/porter-stemmer@0.9.1";
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import { KV, KvKey } from "$sb/types.ts";
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export type Document = {
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id: string;
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text: string;
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};
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export interface BatchKVStore {
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batchSet(kvs: KV[]): Promise<void>;
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batchDel(keys: KvKey[]): Promise<void>;
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query(options: { prefix: KvKey }): Promise<KV[]>;
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}
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type ResultObject = {
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score: number;
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id: string;
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};
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export class SimpleSearchEngine {
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private stopWords = ["and", "or", "the", "a", "an"];
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constructor(
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public index: BatchKVStore,
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// public reverseIndex: BatchKVStore,
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) {
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}
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// Tokenize text into words
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private tokenize(text: string): string[] {
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return text.toLowerCase().split(/[^\p{L}]+/u);
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}
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// Remove stop words from array of words
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private removeStopWords(words: string[]): string[] {
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return words.filter((word) =>
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word.length > 2 &&
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!this.stopWords.includes(word) && /^\p{L}+$/u.test(word)
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);
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}
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// Basic stemming function
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private stem(word: string): string {
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return stemmer(word);
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}
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// Index an array of documents
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public async indexDocument(document: Document): Promise<void> {
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const updateIndexMap = new Map<string, number>(); // word!id -> count
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const updateReverseIndexMap = new Map<string, boolean>(); // id!word -> true
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const pageContent = this.tokenize(document.text);
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const pageName = this.tokenize(document.id);
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const words = [...pageContent, ...pageName];
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const filteredWords = this.removeStopWords(words);
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const stemmedWords = filteredWords.map((word) => this.stem(word));
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// Get the current IDs for these stemmed words
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// const uniqueStemmedWords = [...new Set(stemmedWords)];
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for (const stemmedWord of stemmedWords) {
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const key = `${stemmedWord}!${document.id}`;
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const revKey = `${document.id}!${stemmedWord}`;
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const currentFreq = updateIndexMap.get(key) || 0;
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updateIndexMap.set(key, currentFreq + 1);
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updateReverseIndexMap.set(revKey, true);
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}
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// console.log("updateIndexMap", updateIndexMap);
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await this.index.batchSet(
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[...updateIndexMap.entries()].map((
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[key, value],
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) => ({ key: ["fts", ...key.split("!")], value: value })),
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);
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await this.index.batchSet(
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[...updateReverseIndexMap.entries()].map((
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[key, value],
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) => ({ key: ["fts_rev", ...key.split("!")], value: value })),
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);
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}
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// Search for a phrase and return document ids sorted by match count
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public async search(phrase: string): Promise<ResultObject[]> {
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const words = this.tokenize(phrase);
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const filteredWords = this.removeStopWords(words);
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const stemmedWords = filteredWords.map((word) => this.stem(word));
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// const wordIdsArray: string[][] = await this.index.get(stemmedWords);
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const matchCounts: Map<string, number> = new Map(); // pageName -> count
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for (const stemmedWord of stemmedWords) {
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const entries = await this.index.query({ prefix: ["fts", stemmedWord] });
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for (const { key, value } of entries) {
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const id = key[2];
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if (matchCounts.has(id)) {
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matchCounts.set(id, matchCounts.get(id)! + value);
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} else {
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matchCounts.set(id, value);
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}
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}
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}
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const results = Array.from(matchCounts.entries()).map(
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([id, score]) => ({ id, score }),
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);
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return results.sort((a, b) => b.score - a.score);
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}
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// Delete a document from the index
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public async deleteDocument(documentId: string): Promise<void> {
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const words = await this.index.query({
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prefix: ["fts_rev", documentId],
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});
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const keysToDelete: KvKey[] = [];
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for (const { key } of words) {
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const word = key[2];
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keysToDelete.push(["fts", word, documentId]);
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keysToDelete.push(key);
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}
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await this.index.batchDel(keysToDelete);
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}
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}
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