/**
 * Benchmark — lightweight performance profiling.
 *
 * Usage:
 *   import { Benchmark } from "@systems/benchmark";
 *
 *   const bench = Benchmark.start("vote");
 *   // ... do work ...
 *   bench.mark("resolveUser");   // logs: [vote] resolveUser: 12ms
 *   // ... more work ...
 *   bench.mark("updatePoll");    // logs: [vote] updatePoll: 145ms
 *   bench.end();                 // logs: [vote] total: 157ms
 *
 *   // One-liner:
 *   const result = await Benchmark.measure("vote", async () => {
 *     return await doSomething();
 *   });
 */

 import { Logger, logLevel } from "@systems/logger";

 const log = Logger.for("benchmark");
 
 // ─── Active benchmark instance ────────────────────────────────────────────────
 
 export interface BenchmarkInstance {
   /** Log time since last mark (or start). */
   mark(label: string): void;
   /** Log total time since start. */
   end(): number;
 }
 
 function createBenchmark(name: string, enabled: boolean): BenchmarkInstance {
   let last = Date.now();
   const t0 = last;
 
   return {
     mark(label: string): void {
       if (!enabled) return;
       const now   = Date.now();
       const delta = now - last;
       last = now;
       log.debug(`[${name}] ${label}: ${delta}ms`);
     },
 
     end(): number {
       const total = Date.now() - t0;
       if (enabled) log.debug(`[${name}] total: ${total}ms`);
       return total;
     },
   };
 }
 
 // ─── Namespace ────────────────────────────────────────────────────────────────
 
 // Only profile when LOG_LEVEL=debug
 const _enabled = () => logLevel() === "DEBUG";
 
 export const Benchmark = {
   /**
    * Start a named benchmark.
    * Only active when LOG_LEVEL=debug — zero overhead in production.
    */
   start(name: string): BenchmarkInstance {
     return createBenchmark(name, _enabled());
   },
 
   /**
    * Measure and return the result of an async function.
    */
   async measure<T>(name: string, fn: () => Promise<T>): Promise<T> {
     const bench = Benchmark.start(name);
     try {
       const result = await fn();
       bench.end();
       return result;
     } catch (err) {
       bench.end();
       throw err;
     }
   },
 };