agentfootprint/dist/esm/influence-core/cache.js

The explainable agent framework — backtrack a wrong answer to the exact context that caused it (evidence, not guesses). Built on footprintjs.

/**
 * Fast, deterministic, browser-safe content hash (FNV-1a, two 32-bit
 * lanes + length qualifier → "len-xxxxxxxxyyyyyyyy"). Non-cryptographic
 * — cache keying only.
 */
export function contentHash(text) {
    let h1 = 0x811c9dc5; // FNV offset basis
    let h2 = 0xcbf29ce4; // second lane, different seed
    for (let i = 0; i < text.length; i++) {
        const c = text.charCodeAt(i);
        h1 = Math.imul(h1 ^ c, 0x01000193); // FNV prime
        h2 = Math.imul(h2 ^ c, 0x01000197); // distinct odd prime
    }
    const lane1 = (h1 >>> 0).toString(16).padStart(8, '0');
    const lane2 = (h2 >>> 0).toString(16).padStart(8, '0');
    return `${text.length.toString(36)}-${lane1}${lane2}`;
}
const DEFAULT_MAX_ENTRIES = 1024;
/**
 * Wrap an embedder with a bounded, content-hash-keyed LRU cache.
 * See module docs for keying, bounds, and concurrency semantics.
 */
export class EmbeddingCache {
    dimensions;
    inner;
    maxEntries;
    /** LRU store — Map iteration order is recency (refreshed on hit). */
    vectors = new Map();
    /** Single-flight joins — promises live here until settled. */
    inflight = new Map();
    hits = 0;
    misses = 0;
    evictions = 0;
    constructor(inner, options = {}) {
        const maxEntries = options.maxEntries ?? DEFAULT_MAX_ENTRIES;
        if (!Number.isInteger(maxEntries) || maxEntries <= 0) {
            throw new Error(`EmbeddingCache: maxEntries must be a positive integer (got ${maxEntries})`);
        }
        this.inner = inner;
        this.maxEntries = maxEntries;
        this.dimensions = inner.dimensions;
    }
    async embed(args) {
        const key = contentHash(args.text);
        const cached = this.vectors.get(key);
        if (cached !== undefined) {
            this.hits += 1;
            this.refresh(key, cached);
            return cached.slice();
        }
        const joined = this.inflight.get(key);
        if (joined !== undefined) {
            this.hits += 1; // coalesced — no extra inner call
            return (await joined).slice();
        }
        this.misses += 1;
        const promise = this.inner.embed(args);
        this.inflight.set(key, promise);
        try {
            const vector = await promise;
            this.store(key, vector);
            return vector.slice();
        }
        finally {
            // Settled either way; rejections are never cached.
            this.inflight.delete(key);
        }
    }
    async embedBatch(args) {
        const { texts, signal } = args;
        const out = new Array(texts.length);
        // Partition into cache hits and misses (deduplicating within the
        // batch — the same text twice embeds once).
        const missTexts = [];
        const missSlots = new Map(); // key → output indices
        for (let i = 0; i < texts.length; i++) {
            const key = contentHash(texts[i]);
            const cached = this.vectors.get(key);
            if (cached !== undefined) {
                this.hits += 1;
                this.refresh(key, cached);
                out[i] = cached.slice();
                continue;
            }
            const slots = missSlots.get(key);
            if (slots !== undefined) {
                this.hits += 1; // in-batch duplicate — one inner embed serves both
                slots.push(i);
                continue;
            }
            this.misses += 1;
            missSlots.set(key, [i]);
            missTexts.push(texts[i]);
        }
        if (missTexts.length > 0) {
            const vectors = this.inner.embedBatch
                ? await this.inner.embedBatch({ texts: missTexts, ...(signal ? { signal } : {}) })
                : await this.embedSequential(missTexts, signal);
            let v = 0;
            for (const [key, slots] of missSlots) {
                const vector = vectors[v++];
                this.store(key, vector);
                for (const slot of slots)
                    out[slot] = vector.slice();
            }
        }
        return out;
    }
    /** Visible cache health (bounded honesty — see module docs). */
    stats() {
        return {
            size: this.vectors.size,
            maxEntries: this.maxEntries,
            hits: this.hits,
            misses: this.misses,
            evictions: this.evictions,
        };
    }
    /** Drop all cached vectors. Stats counters are preserved. */
    clear() {
        this.vectors.clear();
    }
    refresh(key, vector) {
        // Map insertion order doubles as the LRU order.
        this.vectors.delete(key);
        this.vectors.set(key, vector);
    }
    store(key, vector) {
        // Defensive copy in — callers can't mutate the cached vector.
        this.vectors.set(key, vector.slice());
        while (this.vectors.size > this.maxEntries) {
            const oldest = this.vectors.keys().next().value;
            this.vectors.delete(oldest);
            this.evictions += 1;
        }
    }
    async embedSequential(texts, signal) {
        const vectors = [];
        for (const text of texts) {
            vectors.push(await this.inner.embed({ text, ...(signal ? { signal } : {}) }));
        }
        return vectors;
    }
}
/** Factory sugar — `embeddingCache(embedder)` reads like the built-ins. */
export function embeddingCache(inner, options = {}) {
    return new EmbeddingCache(inner, options);
}
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