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import { neo4jService } from '../../database/Neo4jService';
/**
* Query Expansion - Expands user query with synonyms and related terms
*/
export class QueryExpander {
private synonymMap: Map<string, string[]> = new Map([
['find', ['search', 'locate', 'discover', 'retrieve']],
['show', ['display', 'present', 'reveal', 'demonstrate']],
['create', ['make', 'build', 'generate', 'construct']],
['delete', ['remove', 'erase', 'eliminate', 'destroy']],
['update', ['modify', 'change', 'alter', 'revise']],
]);
/**
* Expand query with synonyms and related terms
*/
async expandQuery(query: string): Promise<string[]> {
const words = query.toLowerCase().split(/\s+/);
const expandedTerms = new Set<string>([query]);
// Add synonyms
words.forEach(word => {
const synonyms = this.synonymMap.get(word);
if (synonyms) {
synonyms.forEach(syn => {
const expandedQuery = query.replace(new RegExp(word, 'gi'), syn);
expandedTerms.add(expandedQuery);
});
}
});
// Add semantic variations using Neo4j graph
try {
await neo4jService.connect();
// Find related concepts in the graph
const relatedConcepts = await neo4jService.runQuery(
`MATCH (n:Entity)
WHERE toLower(n.name) CONTAINS $query OR toLower(n.content) CONTAINS $query
MATCH (n)-[:RELATED_TO|SIMILAR_TO]-(related)
RETURN DISTINCT related.name as concept
LIMIT 5`,
{ query: query.toLowerCase() }
);
relatedConcepts.forEach(record => {
if (record.concept) {
expandedTerms.add(`${query} ${record.concept}`);
}
});
await neo4jService.disconnect();
} catch (error) {
console.warn('Query expansion from graph failed:', error);
}
return Array.from(expandedTerms);
}
/**
* Extract key phrases from query
*/
extractKeyPhrases(query: string): string[] {
// Simple n-gram extraction (2-3 words)
const words = query.toLowerCase().split(/\s+/);
const phrases: string[] = [];
// Bigrams
for (let i = 0; i < words.length - 1; i++) {
phrases.push(`${words[i]} ${words[i + 1]}`);
}
// Trigrams
for (let i = 0; i < words.length - 2; i++) {
phrases.push(`${words[i]} ${words[i + 1]} ${words[i + 2]}`);
}
return phrases;
}
}
/**
* Result Re-ranker - Re-ranks search results using multiple signals
*/
export class ResultReRanker {
/**
* Re-rank results using multiple scoring signals
*/
async rerank(
query: string,
results: Array<{ id: string; content: string; score: number; metadata?: any }>,
options: {
useRecency?: boolean;
usePopularity?: boolean;
useSemanticSimilarity?: boolean;
} = {}
): Promise<Array<{ id: string; content: string; score: number; metadata?: any }>> {
const scoredResults = await Promise.all(
results.map(async result => {
let finalScore = result.score;
// Recency boost
if (options.useRecency && result.metadata?.createdAt) {
const age = Date.now() - new Date(result.metadata.createdAt).getTime();
const daysSinceCreation = age / (1000 * 60 * 60 * 24);
const recencyBoost = Math.exp(-daysSinceCreation / 30); // Decay over 30 days
finalScore *= (1 + recencyBoost * 0.2);
}
// Popularity boost (based on connections in graph)
if (options.usePopularity) {
try {
await neo4jService.connect();
const connections = await neo4jService.getNodeRelationships(result.id);
const popularityBoost = Math.min(connections.length / 10, 1); // Cap at 10 connections
finalScore *= (1 + popularityBoost * 0.3);
await neo4jService.disconnect();
} catch (error) {
// Ignore errors
}
}
// Exact match boost
if (result.content.toLowerCase().includes(query.toLowerCase())) {
finalScore *= 1.5;
}
return { ...result, score: finalScore };
})
);
// Sort by final score
return scoredResults.sort((a, b) => b.score - a.score);
}
/**
* Diversify results to avoid redundancy
*/
diversify(
results: Array<{ id: string; content: string; score: number }>,
maxSimilarity: number = 0.8
): Array<{ id: string; content: string; score: number }> {
const diversified: typeof results = [];
for (const result of results) {
// Check if too similar to already selected results
const tooSimilar = diversified.some(selected => {
const similarity = this.computeTextSimilarity(result.content, selected.content);
return similarity > maxSimilarity;
});
if (!tooSimilar) {
diversified.push(result);
}
// Stop if we have enough diverse results
if (diversified.length >= 10) break;
}
return diversified;
}
private computeTextSimilarity(text1: string, text2: string): number {
const words1 = new Set(text1.toLowerCase().split(/\s+/));
const words2 = new Set(text2.toLowerCase().split(/\s+/));
const intersection = new Set([...words1].filter(x => words2.has(x)));
const union = new Set([...words1, ...words2]);
return intersection.size / union.size; // Jaccard similarity
}
}
/**
* Hybrid Search - Combines keyword and semantic search
*/
export class HybridSearch {
private queryExpander = new QueryExpander();
private reRanker = new ResultReRanker();
/**
* Perform hybrid search combining multiple strategies
*/
async search(
query: string,
options: {
limit?: number;
useQueryExpansion?: boolean;
useReranking?: boolean;
useDiversification?: boolean;
} = {}
): Promise<Array<{ id: string; content: string; score: number; metadata?: any }>> {
const limit = options.limit || 10;
let queries = [query];
// Query expansion
if (options.useQueryExpansion) {
queries = await this.queryExpander.expandQuery(query);
}
// Execute searches for all query variations
const allResults = new Map<string, any>();
for (const q of queries) {
const results = await graphMemoryService.searchEntities(q, limit * 2);
results.forEach((result, index) => {
const existing = allResults.get(result.id);
// Use position as pseudo-score (lower index = higher relevance)
const resultWithScore = { ...result, content: result.name, score: 1 / (index + 1) };
if (!existing || resultWithScore.score > existing.score) {
allResults.set(result.id, resultWithScore);
}
});
}
let results = Array.from(allResults.values());
// Re-ranking
if (options.useReranking) {
results = await this.reRanker.rerank(query, results, {
useRecency: true,
usePopularity: true,
});
}
// Diversification
if (options.useDiversification) {
results = this.reRanker.diversify(results);
}
return results.slice(0, limit);
}
}
export const queryExpander = new QueryExpander();
export const resultReRanker = new ResultReRanker();
export const hybridSearch = new HybridSearch();
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