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package io.quarkus.agroal.runtime;

import org.jboss.threads.JBossThread;

import io.agroal.api.cache.Acquirable;
import io.agroal.api.cache.ConnectionCache;
import io.netty.util.concurrent.FastThreadLocal;
import io.netty.util.concurrent.FastThreadLocalThread;

class QuarkusNettyConnectionCache implements ConnectionCache {

    final FastThreadLocal connectionCache = new FastThreadLocal<>();

    @Override
    public Acquirable get() {
        Thread thread = Thread.currentThread();
        if (thread instanceof FastThreadLocalThread || thread instanceof JBossThread) {
            //we only want to cache on threads that we control the lifecycle
            //which are the vert.x and potentially jboss threads
            //JBossThread still works with FastThreadLocal, it is just slower, and for most apps
            //this will not be used anyway, as we use VertThread pretty much everywhere if
            //Vert.x is present
            Acquirable acquirable = connectionCache.get();
            return acquirable != null && acquirable.acquire() ? acquirable : null;
        }
        return null;
    }

    @Override
    public void put(Acquirable acquirable) {
        Thread thread = Thread.currentThread();
        if (thread instanceof FastThreadLocalThread || thread instanceof JBossThread) {
            connectionCache.set(acquirable);
        }
    }

    @Override
    public void reset() {
        // Do our best to release memory. In fact `io.agroal.pool.ConnectionPool` calls
        // this method in `housingkeepingExecutor` thread only, so business threads still
        // hold references to `ConnectionHandler` objects.
        connectionCache.remove();

        // `FastThreadLocalThread` uses an array and increasing index for `FastThreadLocal`, the thread
        // local variables will *never* be expunged until the thread exits, so `FastThreadLocal` instance
        // musn't be created again.
        //
        // For other non-`FastThreadLocalThread` threads, `FastThreadLocal` actually uses static
        // `java.lang.ThreadLocal`, it's useless to create fresh `FastThreadLocal` instance.
        //
        // In summary, this connection cache always holds `ConnectionHandler` instances in thread local
        // variables even after the underlying JDBC connections close, this does leak some memory.

        //connectionCache = new FastThreadLocal<>();
    }
}