perf-lens/dist/ai/cache.js

AI-powered frontend performance optimizer

import crypto from 'crypto';
import fs from 'fs';
import path from 'path';
/** Bump whenever prompts change in a way that should invalidate cached analyses. */
export const PROMPT_VERSION = 2;
const CACHE_FILE = '.perflens-cache.json';
/**
 * Result cache: content hash of a batch -> findings. Unchanged files cost
 * nothing on re-scan. Persisted as one JSON file in the project root (gitignored).
 */
// ponytail: whole-batch key; per-file caching if batch churn hurts hit rate
export class AnalysisCache {
    constructor(baseDir, enabled = true) {
        this.enabled = enabled;
        this.entries = {};
        this.file = path.join(baseDir, CACHE_FILE);
        if (enabled && fs.existsSync(this.file)) {
            try {
                this.entries = JSON.parse(fs.readFileSync(this.file, 'utf-8'));
            }
            catch {
                this.entries = {};
            }
        }
    }
    key(model, fileContents) {
        const hash = crypto.createHash('sha256');
        hash.update(`${model}\n${PROMPT_VERSION}\n`);
        for (const file of Object.keys(fileContents).sort()) {
            hash.update(file);
            hash.update('\0');
            hash.update(fileContents[file]);
            hash.update('\0');
        }
        return hash.digest('hex');
    }
    get(key) {
        return this.enabled ? this.entries[key] : undefined;
    }
    set(key, findings) {
        if (!this.enabled)
            return;
        this.entries[key] = findings;
        try {
            fs.writeFileSync(this.file, JSON.stringify(this.entries));
        }
        catch {
            // cache persistence is best-effort
        }
    }
}