/*
 * 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.compiler;

import java.io.File;
import java.io.FileNotFoundException;
import java.net.URISyntaxException;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.atomic.AtomicInteger;

import jakarta.servlet.ServletContext;
import jakarta.servlet.ServletException;

import org.apache.jasper.JspCompilationContext;
import org.apache.jasper.Options;
import org.apache.jasper.runtime.ExceptionUtils;
import org.apache.jasper.servlet.JspServletWrapper;
import org.apache.jasper.util.FastRemovalDequeue;
import org.apache.juli.logging.Log;
import org.apache.juli.logging.LogFactory;


/**
 * Class for tracking JSP compile time file dependencies when the >%@include file="..."%< directive is used. A
 * background thread periodically checks the files a JSP page is dependent upon. If a dependent file changes the JSP
 * page which included it is recompiled. Only used if a web application context is a directory.
 *
 * @author Glenn L. Nielsen
 */
public final class JspRuntimeContext {

    /**
     * Logger
     */
    private final Log log = LogFactory.getLog(JspRuntimeContext.class); // must not be static

    /**
     * Counts how many times the webapp's JSPs have been reloaded.
     */
    private final AtomicInteger jspReloadCount = new AtomicInteger(0);

    /**
     * Counts how many times JSPs have been unloaded in this webapp.
     */
    private final AtomicInteger jspUnloadCount = new AtomicInteger(0);

    // ----------------------------------------------------------- Constructors

    /**
     * Create a JspRuntimeContext for a web application context. Loads in any previously generated dependencies from
     * file.
     *
     * @param context ServletContext for web application
     * @param options The main Jasper options
     */
    public JspRuntimeContext(ServletContext context, Options options) {

        this.context = context;
        this.options = options;

        // Get the parent class loader
        ClassLoader loader = Thread.currentThread().getContextClassLoader();
        if (loader == null) {
            loader = this.getClass().getClassLoader();
        }

        if (log.isTraceEnabled()) {
            if (loader != null) {
                log.trace(Localizer.getMessage("jsp.message.parent_class_loader_is", loader.toString()));
            } else {
                log.trace(Localizer.getMessage("jsp.message.parent_class_loader_is", "<none>"));
            }
        }

        parentClassLoader = loader;
        classpath = initClassPath();

        if (context instanceof org.apache.jasper.servlet.JspCServletContext) {
            return;
        }

        // If this web application context is running from a
        // directory, start the background compilation thread
        String appBase = context.getRealPath("/");
        if (!options.getDevelopment() && appBase != null && options.getCheckInterval() > 0) {
            lastCompileCheck = System.currentTimeMillis();
        }

        if (options.getMaxLoadedJsps() > 0) {
            jspQueue = new FastRemovalDequeue<>(options.getMaxLoadedJsps());
            if (log.isTraceEnabled()) {
                log.trace(Localizer.getMessage("jsp.message.jsp_queue_created", "" + options.getMaxLoadedJsps(),
                        context.getContextPath()));
            }
        }

        /* Init parameter is in seconds, locally we use milliseconds */
        jspIdleTimeout = options.getJspIdleTimeout() * 1000L;
    }

    // ----------------------------------------------------- Instance Variables

    /**
     * This web applications ServletContext
     */
    private final ServletContext context;
    private final Options options;
    private final ClassLoader parentClassLoader;
    private final String classpath;
    private volatile long lastCompileCheck = -1L;
    private volatile long lastJspQueueUpdate = System.currentTimeMillis();
    /* JSP idle timeout in milliseconds */
    private long jspIdleTimeout;

    /**
     * Maps JSP pages to their JspServletWrapper's
     */
    private final Map<String,JspServletWrapper> jsps = new ConcurrentHashMap<>();

    /**
     * Keeps JSP pages ordered by last access.
     */
    private FastRemovalDequeue<JspServletWrapper> jspQueue = null;

    /**
     * Map of class name to associated source map. This is maintained here as multiple JSPs can depend on the same file
     * (included JSP, tag file, etc.) so a web application scoped Map is required.
     */
    private final Map<String,SmapStratum> smaps = new ConcurrentHashMap<>();

    /**
     * Flag that indicates if a background compilation check is in progress.
     */
    private volatile boolean compileCheckInProgress = false;


    // ------------------------------------------------------ Public Methods

    /**
     * Add a new JspServletWrapper.
     *
     * @param jspUri JSP URI
     * @param jsw    Servlet wrapper for JSP
     */
    public void addWrapper(String jspUri, JspServletWrapper jsw) {
        jsps.put(jspUri, jsw);
    }

    /**
     * Get an already existing JspServletWrapper.
     *
     * @param jspUri JSP URI
     *
     * @return JspServletWrapper for JSP
     */
    public JspServletWrapper getWrapper(String jspUri) {
        return jsps.get(jspUri);
    }

    /**
     * Remove a JspServletWrapper.
     *
     * @param jspUri JSP URI of JspServletWrapper to remove
     */
    public void removeWrapper(String jspUri) {
        jsps.remove(jspUri);
    }

    /**
     * Push a newly compiled JspServletWrapper into the queue at first execution of jsp. Destroy any JSP that has been
     * replaced in the queue.
     *
     * @param jsw Servlet wrapper for jsp.
     *
     * @return an unloadHandle that can be pushed to front of queue at later execution times.
     */
    public FastRemovalDequeue<JspServletWrapper>.Entry push(JspServletWrapper jsw) {
        if (log.isTraceEnabled()) {
            log.trace(Localizer.getMessage("jsp.message.jsp_added", jsw.getJspUri(), context.getContextPath()));
        }
        FastRemovalDequeue<JspServletWrapper>.Entry entry = jspQueue.push(jsw);
        JspServletWrapper replaced = entry.getReplaced();
        if (replaced != null) {
            if (log.isTraceEnabled()) {
                log.trace(Localizer.getMessage("jsp.message.jsp_removed_excess", replaced.getJspUri(),
                        context.getContextPath()));
            }
            unloadJspServletWrapper(replaced);
            entry.clearReplaced();
        }
        return entry;
    }

    /**
     * Push unloadHandle for JspServletWrapper to front of the queue.
     *
     * @param unloadHandle the unloadHandle for the jsp.
     */
    public void makeYoungest(FastRemovalDequeue<JspServletWrapper>.Entry unloadHandle) {
        if (log.isTraceEnabled()) {
            JspServletWrapper jsw = unloadHandle.getContent();
            log.trace(Localizer.getMessage("jsp.message.jsp_queue_update", jsw.getJspUri(), context.getContextPath()));
        }
        jspQueue.moveFirst(unloadHandle);
    }

    /**
     * Returns the number of JSPs for which JspServletWrappers exist, i.e., the number of JSPs that have been loaded
     * into the webapp.
     *
     * @return The number of JSPs that have been loaded into the webapp
     */
    public int getJspCount() {
        return jsps.size();
    }

    /**
     * Get the parent ClassLoader.
     *
     * @return ClassLoader parent
     */
    public ClassLoader getParentClassLoader() {
        return parentClassLoader;
    }

    /**
     * Process a "destroy" event for this web application context.
     */
    public void destroy() {
        for (JspServletWrapper jspServletWrapper : jsps.values()) {
            jspServletWrapper.destroy();
        }
    }

    /**
     * Increments the JSP reload counter.
     */
    public void incrementJspReloadCount() {
        jspReloadCount.incrementAndGet();
    }

    /**
     * Resets the JSP reload counter.
     *
     * @param count Value to which to reset the JSP reload counter
     */
    public void setJspReloadCount(int count) {
        jspReloadCount.set(count);
    }

    /**
     * Gets the current value of the JSP reload counter.
     *
     * @return The current value of the JSP reload counter
     */
    public int getJspReloadCount() {
        return jspReloadCount.intValue();
    }

    /**
     * Gets the number of JSPs that are in the JSP limiter queue
     *
     * @return The number of JSPs (in the webapp with which this JspServlet is associated) that are in the JSP limiter
     *             queue
     */
    public int getJspQueueLength() {
        if (jspQueue != null) {
            return jspQueue.getSize();
        }
        return -1;
    }

    /**
     * Gets the number of JSPs that have been unloaded.
     *
     * @return The number of JSPs (in the webapp with which this JspServlet is associated) that have been unloaded
     */
    public int getJspUnloadCount() {
        return jspUnloadCount.intValue();
    }


    /**
     * Method used by background thread to check the JSP dependencies registered with this class for JSPs.
     */
    public void checkCompile() {

        if (lastCompileCheck < 0) {
            // Checking was disabled
            return;
        }
        long now = System.currentTimeMillis();
        if (now > (lastCompileCheck + (options.getCheckInterval() * 1000L))) {
            lastCompileCheck = now;
        } else {
            return;
        }

        List<JspServletWrapper> wrappersToReload = new ArrayList<>();
        // Tell JspServletWrapper to ignore the reload attribute while this
        // check is in progress. See BZ 62603.
        compileCheckInProgress = true;

        Object[] wrappers = jsps.values().toArray();
        for (Object wrapper : wrappers) {
            JspServletWrapper jsw = (JspServletWrapper) wrapper;
            JspCompilationContext ctxt = jsw.getJspEngineContext();
            // Sync on JspServletWrapper when calling ctxt.compile()
            synchronized (jsw) {
                try {
                    ctxt.compile();
                    if (jsw.getReload()) {
                        wrappersToReload.add(jsw);
                    }
                } catch (FileNotFoundException ex) {
                    ctxt.incrementRemoved();
                } catch (Throwable t) {
                    ExceptionUtils.handleThrowable(t);
                    jsw.getServletContext().log(Localizer.getMessage("jsp.error.backgroundCompilationFailed"), t);
                }
            }
        }

        // See BZ 62603.
        // OK to process reload flag now.
        compileCheckInProgress = false;
        // Ensure all servlets and tags that need to be reloaded, are reloaded.
        for (JspServletWrapper jsw : wrappersToReload) {
            // Triggers reload
            try {
                if (jsw.isTagFile()) {
                    // Although this is a public method, all other paths to this
                    // method use this sync, and it is required to prevent race
                    // conditions during the reload.
                    synchronized (this) {
                        jsw.loadTagFile();
                    }
                } else {
                    jsw.getServlet();
                }
            } catch (ServletException e) {
                jsw.getServletContext().log(Localizer.getMessage("jsp.error.reload"), e);
            }
        }
    }

    public boolean isCompileCheckInProgress() {
        return compileCheckInProgress;
    }

    /**
     * @return the classpath that is passed off to the Java compiler.
     */
    public String getClassPath() {
        return classpath;
    }

    /**
     * @return Last time the update background task has run
     */
    public long getLastJspQueueUpdate() {
        return lastJspQueueUpdate;
    }


    public Map<String,SmapStratum> getSmaps() {
        return smaps;
    }


    public Options getOptions() {
        return options;
    }

    // -------------------------------------------------------- Private Methods

    /**
     * Method used to initialize classpath for compiles.
     *
     * @return the compilation classpath
     */
    private String initClassPath() {

        StringBuilder cpath = new StringBuilder();

        if (parentClassLoader instanceof URLClassLoader) {
            URL[] urls = ((URLClassLoader) parentClassLoader).getURLs();

            for (URL url : urls) {
                // Tomcat can use URLs other than file URLs. However, a protocol
                // other than file: will generate a bad file system path, so
                // only add file: protocol URLs to the classpath.

                if (url.getProtocol().equals("file")) {
                    try {
                        // Need to decode the URL, primarily to convert %20
                        // sequences back to spaces
                        String decoded = url.toURI().getPath();
                        cpath.append(decoded).append(File.pathSeparator);
                    } catch (URISyntaxException e) {
                        log.warn(Localizer.getMessage("jsp.warning.classpathUrl"), e);
                    }
                }
            }
        }

        cpath.append(options.getScratchDir()).append(File.pathSeparator);

        String cp = (String) context.getAttribute(options.getServletClasspathAttribute());
        if (cp == null || cp.isEmpty()) {
            cp = options.getClassPath();
        }

        String path = cpath.toString() + cp;

        if (log.isTraceEnabled()) {
            log.trace("Compilation classpath initialized: " + path);
        }
        return path;
    }


    private void unloadJspServletWrapper(JspServletWrapper jsw) {
        removeWrapper(jsw.getJspUri());
        synchronized (jsw) {
            jsw.destroy();
        }
        jspUnloadCount.incrementAndGet();
    }


    /**
     * Method used by background thread to check if any JSPs should be unloaded.
     */
    public void checkUnload() {

        if (log.isTraceEnabled()) {
            int queueLength = -1;
            if (jspQueue != null) {
                queueLength = jspQueue.getSize();
            }
            log.trace(Localizer.getMessage("jsp.message.jsp_unload_check", context.getContextPath(), "" + jsps.size(),
                    "" + queueLength));
        }
        long now = System.currentTimeMillis();
        if (jspIdleTimeout > 0) {
            long unloadBefore = now - jspIdleTimeout;
            Object[] wrappers = jsps.values().toArray();
            for (Object wrapper : wrappers) {
                JspServletWrapper jsw = (JspServletWrapper) wrapper;
                synchronized (jsw) {
                    if (jsw.getLastUsageTime() < unloadBefore) {
                        if (log.isTraceEnabled()) {
                            log.trace(Localizer.getMessage("jsp.message.jsp_removed_idle", jsw.getJspUri(),
                                    context.getContextPath(), "" + (now - jsw.getLastUsageTime())));
                        }
                        if (jspQueue != null) {
                            jspQueue.remove(jsw.getUnloadHandle());
                        }
                        unloadJspServletWrapper(jsw);
                    }
                }
            }
        }
        lastJspQueueUpdate = now;
    }
}