package com.ankurm.jackson3.beyond;

import tools.jackson.core.json.JsonFactory;
import tools.jackson.core.util.JsonRecyclerPools;
import tools.jackson.core.util.RecyclerPool;
import tools.jackson.databind.json.JsonMapper;

import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

/**
 * BEYOND THE POSTS — the performance knob the comparison post names but never measures.
 *
 * Jackson 3 changed the default buffer RecyclerPool. The post says to restore the 2.x
 * thread-local pool if you see a regression. Whether that helps depends entirely on your
 * concurrency profile, so this measures it on the machine you are actually running on
 * instead of asserting a winner.
 *
 * Indicative timings, not JMH. Run it a few times; the numbers move.
 */
public class Y06RecyclerPoolTuning {

    public record Payload(long id, String name, List<String> tags, double amount) { }

    private static final int ITERATIONS = 40_000;

    public static void main(String[] args) throws Exception {
        System.out.println("default pool : "
                + JsonRecyclerPools.defaultPool().getClass().getSimpleName());
        System.out.println("cores        : " + Runtime.getRuntime().availableProcessors());
        System.out.println();

        for (int threads : new int[] { 1, 8 }) {
            System.out.println("--- " + threads + " thread(s), " + ITERATIONS + " round-trips each ---");
            run(threads, "threadLocalPool   (2.x default)", JsonRecyclerPools.threadLocalPool());
            run(threads, "concurrentDeque   (3.x default)", JsonRecyclerPools.newConcurrentDequePool());
            run(threads, "nonRecyclingPool  (no reuse)   ", JsonRecyclerPools.nonRecyclingPool());
            System.out.println();
        }
    }

    private static void run(int threads, String label, RecyclerPool<?> pool) throws Exception {
        @SuppressWarnings({ "unchecked", "rawtypes" })
        JsonFactory factory = JsonFactory.builder().recyclerPool((RecyclerPool) pool).build();
        JsonMapper mapper = JsonMapper.builder(factory).build();

        Payload sample = new Payload(1L, "example", List.of("a", "b", "c"), 12.5);
        for (int i = 0; i < 2_000; i++) {                      // warm up
            mapper.readValue(mapper.writeValueAsString(sample), Payload.class);
        }

        ExecutorService pooled = Executors.newFixedThreadPool(threads);
        long start = System.nanoTime();
        var tasks = java.util.stream.IntStream.range(0, threads)
                .<Callable<Void>>mapToObj(t -> () -> {
                    for (int i = 0; i < ITERATIONS; i++) {
                        mapper.readValue(mapper.writeValueAsString(sample), Payload.class);
                    }
                    return null;
                }).toList();
        for (var future : pooled.invokeAll(tasks)) future.get();
        long ms = (System.nanoTime() - start) / 1_000_000;
        pooled.shutdown();

        System.out.printf("  %-34s %5d ms%n", label, ms);
    }
}