/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.jasper.runtime;

import java.io.IOException;

import jakarta.servlet.Servlet;
import jakarta.servlet.ServletContext;
import jakarta.servlet.ServletRequest;
import jakarta.servlet.ServletResponse;
import jakarta.servlet.jsp.JspApplicationContext;
import jakarta.servlet.jsp.JspEngineInfo;
import jakarta.servlet.jsp.JspFactory;
import jakarta.servlet.jsp.PageContext;

import org.apache.jasper.Constants;

/**
 * Implementation of JspFactory.
 */
public class JspFactoryImpl extends JspFactory {

    /**
     * Creates a new JspFactoryImpl instance with default pool size settings.
     */
    public JspFactoryImpl() {
        super();
    }

    private final ThreadLocal<PageContextPool> localPool = new ThreadLocal<>();
    private int poolSize = -1;

    @Override
    public PageContext getPageContext(Servlet servlet, ServletRequest request, ServletResponse response,
            String errorPageURL, boolean needsSession, int bufferSize, boolean autoflush) {

        PageContext pc;
        if (poolSize > 0) {
            PageContextPool pool = localPool.get();
            if (pool == null) {
                pool = new PageContextPool(poolSize);
                localPool.set(pool);
            }
            pc = pool.get();
            if (pc == null) {
                pc = new PageContextImpl();
            }
        } else {
            pc = new PageContextImpl();
        }

        try {
            pc.initialize(servlet, request, response, errorPageURL, needsSession, bufferSize, autoflush);
        } catch (IOException ignore) {
            // Implementation never throws IOE but can't change the signature
            // since it is part of the JSP API
        }

        return pc;
    }

    @Override
    public void releasePageContext(PageContext pc) {
        if (pc == null) {
            return;
        }

        pc.release();
        if (poolSize > 0 && (pc instanceof PageContextImpl)) {
            localPool.get().put(pc);
        }
    }

    @Override
    public JspEngineInfo getEngineInfo() {
        return new JspEngineInfo() {
            @Override
            public String getSpecificationVersion() {
                return Constants.SPEC_VERSION;
            }
        };
    }

    /**
     * Sets the size of the PageContext pool. A value greater than 0 enables pooling.
     *
     * @param poolSize the desired pool size
     */
    public void setPoolSize(int poolSize) {
        this.poolSize = poolSize;
    }

    private static final class PageContextPool {

        private final PageContext[] pool;

        private int current = -1;

        PageContextPool(int poolSize) {
            this.pool = new PageContext[poolSize];
        }

        public void put(PageContext o) {
            if (current < (pool.length - 1)) {
                current++;
                pool[current] = o;
            }
        }

        public PageContext get() {
            PageContext item = null;
            if (current >= 0) {
                item = pool[current];
                current--;
            }
            return item;
        }

    }

    @Override
    public JspApplicationContext getJspApplicationContext(final ServletContext context) {
        return JspApplicationContextImpl.getInstance(context);
    }
}