@adonis-agora/agent/dist/src/rag/http-reranker.js

Governed, durable-backed AI agent (chat + tool-calling + governance) for AdonisJS — part of the Agora ecosystem.

import { errorMessageOf, HttpModelError } from './openai-embeddings.js';
/**
 * A cross-encoder {@link Reranker} behind an HTTP `/rerank` endpoint — the Cohere-style contract
 * most providers and self-hosted servers share. Compose it with `RerankingRetriever`:
 *
 * ```ts
 * const reranker = new HttpReranker({ url: 'https://api.cohere.com/v2/rerank', model: 'rerank-v3.5', apiKey });
 * const retriever = new RerankingRetriever(hybrid, reranker, { fetchTopK: 30 });
 * ```
 *
 * Reads `results: [{ index, relevance_score }]` (Cohere, Jina), `data: [{ index, relevance_score }]`
 * (Voyage) and a bare `[{ index, score }]` (TEI). Each passage keeps its fields and takes the new
 * score; the list is re-sorted and cut to `topK`. Indices the server invents are ignored.
 */
export class HttpReranker {
    options;
    format;
    doFetch;
    constructor(options) {
        this.options = options;
        this.format = options.format ?? 'auto';
        this.doFetch = options.fetch ?? fetch;
    }
    async rerank(query, passages, options = {}) {
        if (passages.length === 0) {
            return [];
        }
        const topK = options.topK ?? passages.length;
        const documents = passages.map((passage) => passage.text);
        const response = await this.doFetch(this.options.url, {
            method: 'POST',
            headers: {
                'content-type': 'application/json',
                ...(this.options.apiKey ? { authorization: `Bearer ${this.options.apiKey}` } : {}),
                ...this.options.headers,
            },
            body: JSON.stringify({
                ...(this.options.model !== undefined ? { model: this.options.model } : {}),
                query,
                ...(this.format !== 'tei' ? { documents, top_n: topK } : {}),
                ...(this.format !== 'cohere' ? { texts: documents } : {}),
            }),
            signal: AbortSignal.timeout(this.options.timeoutMs ?? 30_000),
        });
        const body = await response.text();
        if (!response.ok) {
            throw new HttpModelError(response.status, `Rerank request failed (${response.status}): ${errorMessageOf(body)}`);
        }
        const items = itemsOf(body);
        if (items === undefined) {
            throw new HttpModelError(502, 'Rerank response has no results');
        }
        const seen = new Set();
        const reranked = [];
        for (const item of items) {
            const index = item.index;
            const passage = typeof index === 'number' ? passages[index] : undefined;
            if (passage === undefined || seen.has(index)) {
                continue;
            }
            seen.add(index);
            reranked.push({ ...passage, score: Number(item.relevance_score ?? item.score ?? 0) });
        }
        reranked.sort((a, b) => b.score - a.score);
        return reranked.slice(0, topK);
    }
}
function itemsOf(body) {
    let json;
    try {
        json = JSON.parse(body);
    }
    catch {
        return undefined;
    }
    if (Array.isArray(json)) {
        return json;
    }
    const wrapped = json;
    const items = wrapped?.results ?? wrapped?.data;
    return Array.isArray(items) ? items : undefined;
}
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