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/*
 * Copyright (c) 2022, 2024 Contributors to the Eclipse Foundation
 * Copyright (c) 1997, 2020 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0, which is available at
 * http://www.eclipse.org/legal/epl-2.0.
 *
 * This Source Code may also be made available under the following Secondary
 * Licenses when the conditions for such availability set forth in the
 * Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
 * version 2 with the GNU Classpath Exception, which is available at
 * https://www.gnu.org/software/classpath/license.html.
 *
 * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 */

package com.sun.enterprise.resource.pool;

import com.sun.appserv.connectors.internal.api.PoolingException;
import com.sun.enterprise.resource.AssocWithThreadResourceHandle;
import com.sun.enterprise.resource.ResourceHandle;
import com.sun.enterprise.resource.ResourceSpec;
import com.sun.enterprise.resource.allocator.ResourceAllocator;
import com.sun.enterprise.resource.pool.datastructure.DataStructureFactory;
import com.sun.enterprise.resource.pool.resizer.AssocWithThreadPoolResizer;
import com.sun.enterprise.resource.pool.resizer.Resizer;

import jakarta.transaction.Transaction;

import java.util.Hashtable;

import org.glassfish.resourcebase.resources.api.PoolInfo;

/**
 * Associates a resource with the thread. When the same thread is used again, it checks whether the resource associated
 * with the thread can serve the request.
 *
 * @author Aditya Gore, Jagadish Ramu
 */
public class AssocWithThreadResourcePool extends ConnectionPool {

    private ThreadLocal localResource = new ThreadLocal<>();

    public AssocWithThreadResourcePool(PoolInfo poolInfo, Hashtable env) throws PoolingException {
        super(poolInfo, env);
    }

    @Override
    protected void initializePoolDataStructure() throws PoolingException {
        dataStructure = DataStructureFactory.getDataStructure("com.sun.enterprise.resource.pool.datastructure.ListDataStructure",
                dataStructureParameters, maxPoolSize, this);
    }

    /**
     * Prefetch is called to check whether there there is a free resource is already associated with the thread Only when
     * prefetch is unable to find a resource, normal routine (getUnenlistedResource) will happen.
     *
     * @param spec ResourceSpec
     * @param alloc ResourceAllocator
     * @param tran Transaction
     * @return ResourceHandle resource associated with the thread, if any
     */
    @Override
    protected ResourceHandle prefetch(ResourceSpec spec, ResourceAllocator alloc, Transaction tran) {
        AssocWithThreadResourceHandle ar = localResource.get();
        if (ar != null) {
            // synch on ar and do a quick-n-dirty check to see if the local
            // resource is usable at all
            synchronized (ar.lock) {
                if ((ar.getThreadId() != Thread.currentThread().getId()) || ar.hasConnectionErrorOccurred() || ar.isDirty()
                        || !ar.isAssociated()) {
                    // we were associated with someone else or resource error
                    // occurred or resource was disassociated and used by some one else. So evict
                    // NOTE: We do not setAssociated to false here since someone
                    // else has associated this resource to themself. Also, if
                    // the eviction is because of a resourceError, the resource is
                    // not going to be used anyway.

                    localResource.remove();
                    return null;
                }

                if (ar.getResourceState().isFree() && ar.getResourceState().isUnenlisted()) {
                    if (matchConnections) {
                        if (!alloc.matchConnection(ar)) {
                            // again, since the credentials of the caller don't match
                            // evict from ThreadLocal
                            // also, mark the resource as unassociated and make this resource
                            // potentially usable
                            localResource.remove();
                            ar.setAssociated(false);
                            if (poolLifeCycleListener != null) {
                                poolLifeCycleListener.connectionNotMatched();
                            }
                            return null;
                        }
                        if (poolLifeCycleListener != null) {
                            poolLifeCycleListener.connectionMatched();
                        }
                    }

                    if (!isConnectionValid(ar, alloc)) {
                        localResource.remove();
                        ar.setAssociated(false);
                        // disassociating the connection from the thread.
                        // validation failure will mark the connectionErrorOccurred flag
                        // and the connection will be removed whenever it is retrieved again
                        // from the pool.
                        return null;
                    }

                    setResourceStateToBusy(ar);
                    if (maxConnectionUsage_ > 0) {
                        ar.incrementUsageCount();
                    }
                    if (poolLifeCycleListener != null) {
                        poolLifeCycleListener.connectionUsed(ar.getId());
                        // Decrement numConnFree
                        poolLifeCycleListener.decrementNumConnFree();

                    }
                    return ar;
                }
            }
        }

        return null;
    }

    @Override
    protected Resizer initializeResizer() {
        return new AssocWithThreadPoolResizer(poolInfo, dataStructure, this, this, preferValidateOverRecreate);
    }

    /**
     * to associate a resource with the thread
     *
     * @param h ResourceHandle
     */
    private void setInThreadLocal(AssocWithThreadResourceHandle h) {
        if (h != null) {
            synchronized (h.lock) {
                h.setThreadId(Thread.currentThread().getId());
                h.setAssociated(true);
                localResource.set(h);
            }
        }
    }

    /**
     * check whether the resource is unused
     *
     * @param h ResourceHandle
     * @return boolean representing resource usefullness
     */
    @Override
    protected boolean isResourceUnused(ResourceHandle h) {
        if (h instanceof AssocWithThreadResourceHandle) {
            return h.getResourceState().isFree() && !((AssocWithThreadResourceHandle) h).isAssociated();
        } else {
            return h.getResourceState().isFree();
        }
    }

    // this is the RI getResource() with some modifications
    /**
     * return resource in free list. If none is found, returns null
     */
    @Override
    protected ResourceHandle getUnenlistedResource(ResourceSpec spec, ResourceAllocator alloc, Transaction tran) throws PoolingException {

        ResourceHandle result;
        result = super.getUnenlistedResource(spec, alloc, tran);

        // It is possible that Resizer might have marked the resource for recycle
        // and hence we should not use this resource.
        if (result != null) {
            synchronized (result.lock) {
                if (dataStructure.getAllResources().contains(result) && ((AssocWithThreadResourceHandle) result).isDirty()) {
                    // Remove the resource and set to null
                    dataStructure.removeResource(result);
                    result = null;
                }
            }
        }
        // If we came here, that's because free doesn't have anything
        // to offer us. This could be because:
        // 1. All free resources are associated
        // 2. There are no free resources
        // 3. We cannot create anymore free resources
        // Handle case 1 here

        // DISASSOCIATE
        if (result == null) {
            synchronized (this) {

                for (ResourceHandle resource : dataStructure.getAllResources()) {
                    synchronized (resource.lock) {
                        // though we are checking resources from within the free list,
                        // we could have a situation where the resource was free upto
                        // this point, put just before we entered the synchronized block,
                        // the resource "h" got used by the thread that was associating it
                        // so we need to check for isFree also

                        if (resource.getResourceState().isUnenlisted() && resource.getResourceState().isFree()
                                && !(((AssocWithThreadResourceHandle) resource).isDirty())) {
                            if (!matchConnection(resource, alloc) || resource.hasConnectionErrorOccurred()) {
                                continue;
                            }
                            result = resource;
                            setResourceStateToBusy(result);
                            ((AssocWithThreadResourceHandle) result).setAssociated(false);

                            break;
                        }
                    }
                }
            }
        }

        if (localResource.get() == null) {
            if (result instanceof AssocWithThreadResourceHandle) {
                setInThreadLocal((AssocWithThreadResourceHandle) result);
            }
        }

        return result;
    }

    /**
     * return the resource back to pool only if it is not associated with the thread.
     *
     * @param h ResourceHandle
     */
    @Override
    protected synchronized void freeUnenlistedResource(ResourceHandle h) {
        if (this.cleanupResource(h)) {
            if (h instanceof AssocWithThreadResourceHandle) {
                // Only when resource handle usage count is more than maxConnUsage
                if (maxConnectionUsage_ > 0 && h.getUsageCount() >= maxConnectionUsage_) {
                    performMaxConnectionUsageOperation(h);
                } else {

                    if (!((AssocWithThreadResourceHandle) h).isAssociated()) {
                        dataStructure.returnResource(h);
                    }
                    // update monitoring data
                    if (poolLifeCycleListener != null) {
                        poolLifeCycleListener.decrementConnectionUsed(h.getId());
                        poolLifeCycleListener.incrementNumConnFree(false, steadyPoolSize);
                    }
                }
                // for both the cases of free.add and maxConUsageOperation, a free resource is added.
                // Hence notify waiting threads
                notifyWaitingThreads();
            }
        }
    }

    /**
     * destroys the resource
     *
     * @param resourceHandle resource to be destroyed
     */
    @Override
    public void deleteResource(ResourceHandle resourceHandle) {
        try {
            super.deleteResource(resourceHandle);
        } finally {
            // Note: here we are using the connectionErrorOccurred flag to indicate
            // that this resource is no longer usable. This flag would be checked while
            // getting from ThreadLocal
            // The main intention of marking this is to handle the case where
            // failAllConnections happens
            // Note that setDirty only happens here - i.e during destroying of a
            // resource

            if (resourceHandle instanceof AssocWithThreadResourceHandle) {
                synchronized (resourceHandle.lock) {
                    ((AssocWithThreadResourceHandle) resourceHandle).setDirty();
                }
            }
        }
    }
}