/**
 * Copyright 2010 JogAmp Community. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification, are
 * permitted provided that the following conditions are met:
 *
 *    1. Redistributions of source code must retain the above copyright notice, this list of
 *       conditions and the following disclaimer.
 *
 *    2. Redistributions in binary form must reproduce the above copyright notice, this list
 *       of conditions and the following disclaimer in the documentation and/or other materials
 *       provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY JogAmp Community ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
 * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL JogAmp Community OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * The views and conclusions contained in the software and documentation are those of the
 * authors and should not be interpreted as representing official policies, either expressed
 * or implied, of JogAmp Community.
 */

package com.jogamp.common.util;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.Closeable;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.security.AccessControlContext;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.lang.reflect.Constructor;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
import java.nio.ByteBuffer;

import jogamp.common.Debug;
import jogamp.common.os.AndroidUtils;
import jogamp.common.os.PlatformPropsImpl;

import com.jogamp.common.net.AssetURLContext;
import com.jogamp.common.nio.Buffers;
import com.jogamp.common.os.MachineDescription;
import com.jogamp.common.os.Platform;

public class IOUtil {
    public static final boolean DEBUG = Debug.debug("IOUtil");
    
    /** Std. temporary directory property key <code>java.io.tmpdir</code> */
    public static final String java_io_tmpdir_propkey = "java.io.tmpdir";
    public static final String user_home_propkey = "user.home";
    private static final String XDG_CACHE_HOME_envkey = "XDG_CACHE_HOME";

    /** Subdirectory within platform's temporary root directory where all JogAmp related temp files are being stored: {@code jogamp} */ 
    public static final String tmpSubDir = "jogamp";
    
    private IOUtil() {}
    
    /** 
     * Since usage of {@link java.io.FileOutputStream} is considered security critical,
     * we need to check it's availability for each use.
     * <p>
     * In case a SecurityManager is installed, privileged access is required.
     * </p>
     *     
     * @return the constructor of {@link java.io.FileOutputStream} if available and 
     *         no SecurityManager is installed or privileged access is granted. 
     *         Otherwise null.
     *          
     */
    private static final Constructor<?> getFOSCtor() {
        Constructor<?> _fosCtor;
        Throwable _t;
        try {
            _fosCtor = ReflectionUtil.getConstructor("java.io.FileOutputStream", new Class<?>[] { File.class }, IOUtil.class.getClassLoader());
            _t = null;
        } catch (Throwable t) {
            _fosCtor = null;
            _t = t;
        }
        if(DEBUG) { 
            System.err.println("IOUtil: java.io.FileOutputStream available: "+(null != _fosCtor));
            if(null!=_t) {
                _t.printStackTrace();
            }
        }
        return _fosCtor;
    }
        
    /***
     * 
     * STREAM COPY STUFF
     *  
     */
    
    /**
     * Copy the specified URL resource to the specified output file. The total
     * number of bytes written is returned. Both streams are closed upon completion.
     * 
     * @param conn the open URLConnection 
     * @param outFile the destination
     * @return
     * @throws IOException
     */
    public static int copyURLConn2File(URLConnection conn, File outFile) throws IOException {
        conn.connect();  // redundant     

        int totalNumBytes = 0;
        InputStream in = new BufferedInputStream(conn.getInputStream());
        try {
            totalNumBytes = copyStream2File(in, outFile, conn.getContentLength());
        } finally {
            in.close();
        }
        return totalNumBytes;
    }

    /**
     * Copy the specified input stream to the specified output file. The total
     * number of bytes written is returned. Both streams are closed upon completion.
     * 
     * @param in the source 
     * @param outFile the destination
     * @param totalNumBytes informal number of expected bytes, maybe used for user feedback while processing. -1 if unknown 
     * @return
     * @throws IOException
     */
    public static int copyStream2File(InputStream in, File outFile, int totalNumBytes) throws IOException {
        OutputStream out = new BufferedOutputStream(new FileOutputStream(outFile));
        try {
            totalNumBytes = copyStream2Stream(in, out, totalNumBytes);
        } finally {
            out.close();
        }
        return totalNumBytes;
    }

    /**
     * Copy the specified input stream to the specified output stream. The total
     * number of bytes written is returned.
     * 
     * @param in the source 
     * @param out the destination
     * @param totalNumBytes informal number of expected bytes, maybe used for user feedback while processing. -1 if unknown 
     * @return
     * @throws IOException
     */
    public static int copyStream2Stream(InputStream in, OutputStream out, int totalNumBytes) throws IOException {
        final byte[] buf = new byte[Platform.getMachineDescription().pageSizeInBytes()];
        int numBytes = 0;
        while (true) {
            int count;
            if ((count = in.read(buf)) == -1) {
                break;
            }
            out.write(buf, 0, count);
            numBytes += count;
        }
        return numBytes;
    }

    /**
     * Copy the specified input stream to a byte array, which is being returned.
     */
    public static byte[] copyStream2ByteArray(InputStream stream) throws IOException {
        // FIXME: Shall enforce a BufferedInputStream ?
        if( !(stream instanceof BufferedInputStream) ) {
            stream = new BufferedInputStream(stream);
        }
        int totalRead = 0;
        int avail = stream.available();
        byte[] data = new byte[avail];
        int numRead = 0;
        do {
            if (totalRead + avail > data.length) {
                final byte[] newData = new byte[totalRead + avail];
                System.arraycopy(data, 0, newData, 0, totalRead);
                data = newData;
            }
            numRead = stream.read(data, totalRead, avail);
            if (numRead >= 0) {
                totalRead += numRead;
            }
            avail = stream.available();
        } while (avail > 0 && numRead >= 0);

        // just in case the announced avail > totalRead
        if (totalRead != data.length) {
            final byte[] newData = new byte[totalRead];
            System.arraycopy(data, 0, newData, 0, totalRead);
            data = newData;
        }
        return data;
    }

    /**
     * Copy the specified input stream to a NIO ByteBuffer w/ native byte order, which is being returned.
     * <p>The implementation creates the ByteBuffer w/ {@link #copyStream2ByteArray(InputStream)}'s returned byte array.</p>
     */
    public static ByteBuffer copyStream2ByteBuffer(InputStream stream) throws IOException {
        // FIXME: Shall enforce a BufferedInputStream ?
        if( !(stream instanceof BufferedInputStream) ) {
            stream = new BufferedInputStream(stream);
        }
        int avail = stream.available();
        final MachineDescription machine = Platform.getMachineDescription(); 
        ByteBuffer data = Buffers.newDirectByteBuffer( machine.pageAlignedSize(avail) );
        byte[] chunk = new byte[machine.pageSizeInBytes()];
        int chunk2Read = Math.min(machine.pageSizeInBytes(), avail);
        int numRead = 0;
        do {
            if (avail > data.remaining()) {
                final ByteBuffer newData = Buffers.newDirectByteBuffer(
                                               machine.pageAlignedSize(data.position() + avail) );
                newData.put(data);
                data = newData;
            }
            
            numRead = stream.read(chunk, 0, chunk2Read);
            if (numRead >= 0) {
                data.put(chunk, 0, numRead);
            }
            avail = stream.available();
            chunk2Read = Math.min(machine.pageSizeInBytes(), avail);
        } while (avail > 0 && numRead >= 0);

        data.flip();
        return data;
    }

    /***
     * 
     * RESOURCE / FILE NAME STUFF
     *  
     */
    
    /**
     * 
     * @param path
     * @param startWithSlash
     * @param endWithSlash
     * @return
     * @throws RuntimeException if final path is empty or has no parent directory available while resolving <code>../</code> 
     */
    public static String slashify(String path, boolean startWithSlash, boolean endWithSlash) throws RuntimeException {
        String p = path.replace('\\', '/'); // unify file seperator     
        if (startWithSlash && !p.startsWith("/")) {
            p = "/" + p;
        }
        if (endWithSlash && !p.endsWith("/")) {
            p = p + "/";
        }
        try {
            return cleanPathString(p);
        } catch (MalformedURLException e) {
            throw new RuntimeException(e);
        }        
    }
    
    /** Using the proper advertised conversion via File -> URI -> URL */
    public static URL toURL(File file) throws MalformedURLException {
        return file.toURI().toURL();
    }
    
    /** Using the simple conversion via File -> URL, assuming proper characters. */
    public static URL toURLSimple(File file) throws MalformedURLException {
        return new URL("file", "", slashify(file.getAbsolutePath(), true, file.isDirectory()));        
    }
    
    public static URL toURLSimple(String protocol, String file, boolean isDirectory) throws MalformedURLException {
        return new URL(protocol, "", slashify(file, true, isDirectory));        
    }
    
    /**
     * Returns the lowercase suffix of the given file name (the text
     * after the last '.' in the file name). Returns null if the file
     * name has no suffix. Only operates on the given file name;
     * performs no I/O operations.
     *
     * @param file name of the file
     * @return lowercase suffix of the file name
     * @throws NullPointerException if file is null
     */

    public static String getFileSuffix(File file) {
        return getFileSuffix(file.getName());
    }

    /**
     * Returns the lowercase suffix of the given file name (the text
     * after the last '.' in the file name). Returns null if the file
     * name has no suffix. Only operates on the given file name;
     * performs no I/O operations.
     *
     * @param filename name of the file
     * @return lowercase suffix of the file name
     * @throws NullPointerException if filename is null
     */
    public static String getFileSuffix(String filename) {
        int lastDot = filename.lastIndexOf('.');
        if (lastDot < 0) {
            return null;
        }
        return toLowerCase(filename.substring(lastDot + 1));
    }

    /***
     * @param file
     * @param allowOverwrite
     * @return outputStream The resulting output stream
     * @throws IOException if the file already exists and <code>allowOverwrite</code> is false, 
     *                     the class {@link java.io.FileOutputStream} is not accessible or
     *                     the user does not have sufficient rights to access the local filesystem. 
     */
    public static FileOutputStream getFileOutputStream(File file, boolean allowOverwrite) throws IOException {
        final Constructor<?> fosCtor = getFOSCtor();
        if(null == fosCtor) {
            throw new IOException("Cannot open file (" + file + ") for writing, FileOutputStream feature not available.");
        }
        if (file.exists() && !allowOverwrite) {
            throw new IOException("File already exists (" + file + ") and overwrite=false");
        }
        try {
            return (FileOutputStream) fosCtor.newInstance(new Object[] { file });
        } catch (Exception e) {
            throw new IOException("error opening " + file + " for write. ", e);
        }
    }
    
    public static String getClassFileName(String clazzBinName) throws IOException {
        // or return clazzBinName.replace('.', File.separatorChar) + ".class"; ?            
        return clazzBinName.replace('.', '/') + ".class";            
    }
    
    /**
     * @param clazzBinName com.jogamp.common.util.cache.TempJarCache 
     * @param cl
     * @return jar:file:/usr/local/projects/JOGL/gluegen/build-x86_64/gluegen-rt.jar!/com/jogamp/common/util/cache/TempJarCache.class
     * @throws IOException
     */
    public static URL getClassURL(String clazzBinName, ClassLoader cl) throws IOException {
        return cl.getResource(getClassFileName(clazzBinName));
    }
        
    /**
     * Returns the basename of the given fname w/o directory part
     */
    public static String getBasename(String fname) {
        fname = slashify(fname, false, false);
        int lios = fname.lastIndexOf('/');  // strip off dirname
        if(lios>=0) {
            fname = fname.substring(lios+1);
        }
        return fname;
    }
    
    /**
     * Returns unified '/' dirname including the last '/'
     */
    public static String getDirname(String fname) {
        fname = slashify(fname, false, false);
        int lios = fname.lastIndexOf('/');  // strip off dirname
        if(lios>=0) {
            fname = fname.substring(0, lios+1);
        }
        return fname;
    }
    
    private static String toLowerCase(String arg) {
        if (arg == null) {
            return null;
        }

        return arg.toLowerCase();
    }
    
    /***
     * 
     * RESOURCE LOCATION STUFF
     *  
     */
    
    /**
     * Locating a resource using {@link #getResource(String, ClassLoader)}:
     * <ul>
     *   <li><i>relative</i>: <code>context</code>'s package name-path plus <code>resourcePath</code> via <code>context</code>'s ClassLoader. 
     *       This allows locations relative to JAR- and other URLs. 
     *       The <code>resourcePath</code> may start with <code>../</code> to navigate to parent folder.</li>
     *   <li><i>absolute</i>: <code>context</code>'s ClassLoader and the <code>resourcePath</code> as is (filesystem)</li>
     * </ul>
     *
     * <p>
     * Returns the resolved and open URLConnection or null if not found.
     * </p>
     * 
     * @see #getResource(String, ClassLoader)
     * @see ClassLoader#getResource(String)
     * @see ClassLoader#getSystemResource(String)
     */
    public static URLConnection getResource(Class<?> context, String resourcePath) {
        if(null == resourcePath) {
            return null;
        }        
        ClassLoader contextCL = (null!=context)?context.getClassLoader():IOUtil.class.getClassLoader();
        URLConnection conn = null;
        if(null != context) {
            // scoping the path within the class's package            
            final String className = context.getName().replace('.', '/');
            final int lastSlash = className.lastIndexOf('/');
            if (lastSlash >= 0) {
                conn = getResource(className.substring(0, lastSlash + 1) + resourcePath, contextCL);
            }
            if(DEBUG) {
                System.err.println("IOUtil: found <"+resourcePath+"> within class package: "+(null!=conn));
            }
        } else if(DEBUG) {
            System.err.println("IOUtil: null context");
        }
        if(null == conn) {
            conn = getResource(resourcePath, contextCL);
            if(DEBUG) {
                System.err.println("IOUtil: found <"+resourcePath+"> by classloader: "+(null!=conn));
            }
        }
        return conn;
    }

    /**
     * Locating a resource using the ClassLoader's facilities.
     * <p>
     * Returns the resolved and connected URLConnection or null if not found.
     * </p>
     *
     * @see ClassLoader#getResource(String)
     * @see ClassLoader#getSystemResource(String)
     * @see URL#URL(String)
     * @see File#File(String)
     */
    public static URLConnection getResource(String resourcePath, ClassLoader cl) {
        if(null == resourcePath) {
            return null;
        }
        if(DEBUG) {
            System.err.println("IOUtil: locating <"+resourcePath+">, has cl: "+(null!=cl));
        }
        if(resourcePath.startsWith(AssetURLContext.asset_protocol_prefix)) {
            try {
                return AssetURLContext.createURL(resourcePath, cl).openConnection();
            } catch (IOException ioe) {
                if(DEBUG) {
                    System.err.println("IOUtil: Catched Exception:");
                    ioe.printStackTrace();
                }
                return null;
            }
        } else {
            try {
                return AssetURLContext.resolve(resourcePath, cl);
            } catch (IOException ioe) {
                if(DEBUG) {
                    System.err.println("IOUtil: Catched Exception:");
                    ioe.printStackTrace();
                }
            }
        }
        return null;
    }

    /**
     * Generates a path for the 'relativeFile' relative to the 'baseLocation'.
     * 
     * @param baseLocation denotes a directory
     * @param relativeFile denotes a relative file to the baseLocation
     */
    public static String getRelativeOf(File baseLocation, String relativeFile) {
        if(null == relativeFile) {
            return null;
        }
        
        if (baseLocation != null) {
            final File file = new File(baseLocation, relativeFile);
            // Handle things on Windows
            return slashify(file.getPath(), false, false);
        }
        return null;
    }

    /**
     * @param path assuming a slashified path beginning with "/" as it's root directory, either denotes a file or directory.
     * @return parent of path
     * @throws MalformedURLException if path is empty or has parent no directory available 
     */
    public static String getParentOf(String path) throws MalformedURLException {
        final int pl = null!=path ? path.length() : 0;
        if(pl == 0) {
            throw new MalformedURLException("path is empty <"+path+">");
        }
        
        final int e = path.lastIndexOf("/");
        if( e < 0 ) {
            throw new MalformedURLException("path contains no '/' <"+path+">");
        }
        if( e == 0 ) {
            // path is root directory
            throw new MalformedURLException("path has no parents <"+path+">");
        }
        if( e <  pl - 1 ) {
            // path is file, return it's parent directory
            return path.substring(0, e+1);
        }
        final int j = path.lastIndexOf("!") + 1; // '!' Separates JARFile entry -> local start of path 
        // path is a directory ..
        final int p = path.lastIndexOf("/", e-1);
        if( p >= j) {
            return path.substring(0, p+1);
        }
        throw new MalformedURLException("parent of path contains no '/' <"+path+">");
    }
    
    /**
     * @param path assuming a slashified path beginning with "/" as it's root directory, either denotes a file or directory.
     * @return clean path string where <code>../</code> and <code>./</code> is resolved. 
     * @throws MalformedURLException if path is empty or has no parent directory available while resolving <code>../</code>
     */
    public static String cleanPathString(String path) throws MalformedURLException {
        int idx;
        while ( ( idx = path.indexOf("../") ) >= 0 ) {
            path = getParentOf(path.substring(0, idx)) + path.substring(idx+3);
        }
        while ( ( idx = path.indexOf("./") ) >= 0 ) {
            path = path.substring(0, idx) + path.substring(idx+2);
        }
        return path;
    }
    
    /**
     * Generates a path for the 'relativeFile' relative to the 'baseLocation',
     * hence the result is a absolute location.
     * 
     * @param baseLocation denotes a URL to a directory if ending w/ '/', otherwise we assume a file
     * @param relativeFile denotes a relative file to the baseLocation's parent directory
     * @throws MalformedURLException 
     */
    public static URL getRelativeOf(URL baseLocation, String relativeFile) throws MalformedURLException {    
        final String scheme = baseLocation.getProtocol();
        final String auth = baseLocation.getAuthority();
        String path = baseLocation.getPath();
        String query = baseLocation.getQuery();
        String fragment = baseLocation.getRef();
        
        if(!path.endsWith("/")) {
            path = getParentOf(path);
        }
        return compose(scheme, auth, path, relativeFile, query, fragment);
    }
    
    public static URL compose(String scheme, String auth, String path1, String path2, String query, String fragment) throws MalformedURLException {
        StringBuilder sb = new StringBuilder();
        if(null!=scheme) {
            sb.append(scheme);
            sb.append(":");
        }
        if(null!=auth) {
            sb.append("//");
            sb.append(auth);
        }
        if(null!=path1) {
            sb.append(path1);
        }
        if(null!=path2) {
            sb.append(path2);
        }
        if(null!=query) {
            sb.append("?");
            sb.append(query);
        }
        if(null!=fragment) {
            sb.append("#");
            sb.append(fragment);
        }
        return new URL(cleanPathString(sb.toString()));
    }    
    
    /**
     * Returns the connected URLConnection, or null if not url is not available
     */
    public static URLConnection openURL(URL url) {
        return openURL(url, ".");
    }
    
    /**
     * Returns the connected URLConnection, or null if not url is not available
     */
    public static URLConnection openURL(URL url, String dbgmsg) {
        if(null!=url) {
            try {
                final URLConnection c = url.openConnection();
                c.connect(); // redundant
                if(DEBUG) {
                    System.err.println("IOUtil: urlExists("+url+") ["+dbgmsg+"] - true");
                }
                return c;
            } catch (IOException ioe) { 
                if(DEBUG) {
                    System.err.println("IOUtil: urlExists("+url+") ["+dbgmsg+"] - false - "+ioe.getClass().getSimpleName()+": "+ioe.getMessage());
                    ioe.printStackTrace();
                }                
            }
        } else if(DEBUG) {
            System.err.println("IOUtil: no url - urlExists(null) ["+dbgmsg+"]");
        }                
        
        return null;
    }
    
    private static String getShellSuffix() {
        switch(PlatformPropsImpl.OS_TYPE) {
            case WINDOWS:
              return ".bat";
            default:
              return ".sh";
        }
    }
    
    private static boolean getOSHasNoexecFS() {
        switch(PlatformPropsImpl.OS_TYPE) {
            case WINDOWS:
            case OPENKODE:
              return false;
                
            default:
              return true;
        }
    }
    
    /**
     * @see <a href="http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html">Free-Desktop - XDG Base Directory Specification</a>
     */
    private static boolean getOSHasFreeDesktopXDG() {
        switch(PlatformPropsImpl.OS_TYPE) {
            case ANDROID:
            case MACOS:
            case WINDOWS:
            case OPENKODE:
              return false;
                
            default:
              return true;
        }
    }
    
    /**
     * Test whether {@code file} exists and matches the given requirements
     * 
     * @param file
     * @param shallBeDir
     * @param shallBeWritable
     * @return
     */
    public static boolean testFile(File file, boolean shallBeDir, boolean shallBeWritable) {        
        if (!file.exists()) {
            if(DEBUG) {
                System.err.println("IOUtil.testFile: <"+file.getAbsolutePath()+">: does not exist");
            }
            return false;            
        }
        if (shallBeDir && !file.isDirectory()) {
            if(DEBUG) {
                System.err.println("IOUtil.testFile: <"+file.getAbsolutePath()+">: is not a directory");
            }
            return false;
        }
        if (shallBeWritable && !file.canWrite()) {
            if(DEBUG) {
                System.err.println("IOUtil.testFile: <"+file.getAbsolutePath()+">: is not writable");
            }
            return false; 
        }
        return true;
    }

    /**
     * Returns true if the given {@code dir}
     * <ol>
     *   <li>exists, and</li>
     *   <li>is a directory, and</li>
     *   <li>is writeable, and</li>
     *   <li>files can be executed from the directory</li>  
     * </ol>
     *  
     * @throws SecurityException if file creation and process execution is not allowed within the current security context
     * @param dir
     */
    public static boolean testDirExec(File dir)
            throws SecurityException
    {
        if (!testFile(dir, true, true)) {
            return false;            
        }
        if(!getOSHasNoexecFS()) {
            return true;
        }
        
        File exetst;
        try {
            exetst = File.createTempFile("jogamp_exe_tst", getShellSuffix(), dir);
        } catch (SecurityException se) {
            throw se; // fwd Security exception
        } catch (IOException e) {
            if(DEBUG) {
                e.printStackTrace();
            }
            return false;
        }
        int ok = -1;
        if(exetst.setExecutable(true)) {
            try {
                Process pr = Runtime.getRuntime().exec(exetst.getCanonicalPath());
                pr.waitFor() ;
                ok = pr.exitValue();
            } catch (SecurityException se) {
                throw se; // fwd Security exception
            } catch (Throwable t) {
                ok = -2;
                if(DEBUG) {
                    System.err.println("IOUtil.testDirExec: <"+exetst.getAbsolutePath()+">: "+t.getMessage());
                    // t.printStackTrace();
                }
            }
        }
        exetst.delete();
        return 0 == ok;
    }

    private static File testDirImpl(File dir, boolean create, boolean executable) 
            throws SecurityException
    {
        if (create && !dir.exists()) {
            dir.mkdirs();            
        }
        if( executable ) {
            if(testDirExec(dir)) {
                return dir;
            }
        } else if(testFile(dir, true, true)) {
            return dir;            
        }
        return null;
    }
    
    /**
     * Returns the directory {@code dir}, which is processed and tested as described below.
     * <ol>
     *   <li>If {@code create} is {@code true} and the directory does not exist yet, it is created incl. all sub-directories.</li>
     *   <li>If {@code dirName} exists, but is not a directory, {@code null} is being returned.</li>
     *   <li>If the directory does not exist or is not writeable, {@code null} is being returned.</li>
     *   <li>If {@code executable} is {@code true} and files cannot be executed from the directory, {@code null} is being returned.</li>  
     * </ol>
     *  
     * @param dir the directory to process
     * @param create true if the directory shall be created if not existing
     * @param executable true if the user intents to launch executables from the temporary directory, otherwise false.
     * @param acc The security {@link AccessControlContext} to create directories and test <i>executability</i> 
     * @throws SecurityException if file creation and process execution is not allowed within the current security context
     */
    public static File testDir(final File dir, final boolean create, final boolean executable, AccessControlContext acc)
        throws SecurityException
    {
        if( null != acc ) {
            return AccessController.doPrivileged(new PrivilegedAction<File>() {
                public File run() {
                  return testDirImpl(dir, create, executable);
                } }, acc);
        } else {
            return testDirImpl(dir, create, executable);
        }    
    }    
    
    private static boolean isStringSet(String s) { return null != s && 0 < s.length(); } 
    
    /**
     * This methods finds [and creates] an available temporary sub-directory:
     * <pre>
           File tmpBaseDir = null;    
           if(null != testDir(tmpRoot, true, executable)) { // check tmpRoot first
               for(int i = 0; null == tmpBaseDir && i<=9999; i++) {
                   final String tmpDirSuffix = String.format("_%04d", i); // 4 digits for iteration
                   tmpBaseDir = testDir(new File(tmpRoot, tmpSubDirPrefix+tmpDirSuffix), true, executable);
               }
           } else {
               tmpBaseDir = null;
           }
           return tmpBaseDir;
     * </pre>
     * <p>
     * The iteration through [0000-9999] ensures that the code is multi-user save.
     * </p>
     * @param tmpRoot
     * @param executable
     * @param tmpDirPrefix
     * @return a temporary directory, writable by this user
     * @throws SecurityException
     */
    private static File getSubTempDir(File tmpRoot, String tmpSubDirPrefix, boolean executable)
        throws SecurityException
    {
       File tmpBaseDir = null;    
       if(null != testDirImpl(tmpRoot, true /* create */, executable)) { // check tmpRoot first
           for(int i = 0; null == tmpBaseDir && i<=9999; i++) {
               final String tmpDirSuffix = String.format("_%04d", i); // 4 digits for iteration
               tmpBaseDir = testDirImpl(new File(tmpRoot, tmpSubDirPrefix+tmpDirSuffix), true /* create */, executable);
           }
       } else {
           tmpBaseDir = null;
       }
       return tmpBaseDir;
    }
        
    private static File getTempDirImpl(boolean executable)
        throws SecurityException, RuntimeException
    {        
        if(!tempRootSet) { // volatile: ok
            synchronized(IOUtil.class) {
                if(!tempRootSet) {
                    tempRootSet = true;
                    {
                        final File ctxTempDir = AndroidUtils.getTempRoot(); // null if ( !Android || no android-ctx )
                        if(null != ctxTempDir) {
                            tempRootNoexec = getSubTempDir(ctxTempDir, tmpSubDir, false /* executable, see below */);
                            tempRootExec = tempRootNoexec; // FIXME: Android temp root is always executable (?)
                            return tempRootExec;
                        }
                    }
                    
                    final String java_io_tmpdir = PropertyAccess.getProperty(java_io_tmpdir_propkey, false, null);
                    final String user_home = PropertyAccess.getProperty(user_home_propkey, false, null);
                    
                    final String xdg_cache_home;
                    {
                        String _xdg_cache_home;
                        if( getOSHasFreeDesktopXDG() ) { 
                            _xdg_cache_home = System.getenv(XDG_CACHE_HOME_envkey);
                            if( !isStringSet(_xdg_cache_home) && isStringSet(user_home) ) {
                                _xdg_cache_home = user_home + File.separator + ".cache" ; // default
                            }                           
                        } else {
                            _xdg_cache_home = null;
                        }
                        xdg_cache_home = _xdg_cache_home;
                    }
                    
                    // 1) java.io.tmpdir/jogamp
                    if( null == tempRootExec && isStringSet(java_io_tmpdir) ) {
                        tempRootExec = getSubTempDir(new File(java_io_tmpdir), tmpSubDir, true /* executable */);
                    }
                    
                    // 2) $XDG_CACHE_HOME/jogamp
                    if(null == tempRootExec && isStringSet(xdg_cache_home)) {
                        tempRootExec = getSubTempDir(new File(xdg_cache_home), tmpSubDir, true /* executable */);                        
                    }
                    
                    // 3) $HOME/.jogamp
                    if(null == tempRootExec && isStringSet(user_home)) {                        
                        tempRootExec = getSubTempDir(new File(user_home), "." + tmpSubDir, true /* executable */);
                    }                    
                    
                    
                    if(null != tempRootExec) {
                        tempRootNoexec = tempRootExec;
                    } else {
                        // 1) java.io.tmpdir/jogamp
                        if( null == tempRootNoexec && isStringSet(java_io_tmpdir) ) {
                            tempRootNoexec = getSubTempDir(new File(java_io_tmpdir), tmpSubDir, false /* executable */);
                        }
                        
                        // 2) $XDG_CACHE_HOME/jogamp
                        if(null == tempRootNoexec && isStringSet(xdg_cache_home)) {
                            tempRootNoexec = getSubTempDir(new File(xdg_cache_home), tmpSubDir, false /* executable */);                        
                        }
                        
                        // 3) $HOME/.jogamp
                        if(null == tempRootNoexec && isStringSet(user_home)) {                        
                            tempRootNoexec = getSubTempDir(new File(user_home), "." + tmpSubDir, false /* executable */);
                        }                                            
                    }
                    
                    if(DEBUG) {
                        System.err.println("IOUtil.getTempRoot(): temp dirs: exec: "+tempRootExec.getAbsolutePath()+", noexec: "+tempRootNoexec.getAbsolutePath());
                    }
                }
            }
        }
        final File r = executable ? tempRootExec : tempRootNoexec ;
        if(null == r) {
            throw new RuntimeException("Could not determine a temporary directory");
        }
        return r;
    }
    private static File tempRootExec = null; // writeable and executable
    private static File tempRootNoexec = null; // writeable, maybe executable
    private static volatile boolean tempRootSet = false;
    
    /**
     * Returns a platform independent writable directory for temporary files
     * consisting of the platform's {@code temp-root} + {@link #tmpSubDir}, 
     * e.g. {@code /tmp/jogamp_0000/}. 
     * <p>
     * On standard Java the {@code temp-root} folder is specified by <code>java.io.tempdir</code>.
     * </p> 
     * <p>
     * On Android the {@code temp-root} folder is relative to the applications local folder 
     * (see {@link Context#getDir(String, int)}) is returned, if
     * the Android application/activity has registered it's Application Context
     * via {@link jogamp.common.os.android.StaticContext.StaticContext#init(Context, ClassLoader) StaticContext.init(..)}.
     * This allows using the temp folder w/o the need for <code>sdcard</code>
     * access, which would be the <code>java.io.tempdir</code> location on Android!
     * </p>
     * <p>
     * In case {@code temp-root} is the users home folder,
     * a dot is being prepended to {@link #tmpSubDir}, i.e.: {@code /home/user/.jogamp_0000/}. 
     * </p>
     * @param executable true if the user intents to launch executables from the temporary directory, otherwise false.
     * @param acc The security {@link AccessControlContext} to access properties, environment vars, create directories and test <i>executability</i> 
     * @throws SecurityException if access to <code>java.io.tmpdir</code> is not allowed within the current security context
     * @throws RuntimeException if no temporary directory could be determined
     *  
     * @see PropertyAccess#getProperty(String, boolean, java.security.AccessControlContext)
     * @see Context#getDir(String, int)
     */
    public static File getTempDir(final boolean executable, AccessControlContext acc)
        throws SecurityException, RuntimeException
    {
        if( null != acc ) {
            return AccessController.doPrivileged(new PrivilegedAction<File>() {
                public File run() {
                  return getTempDirImpl(executable);
                } }, acc);
        } else {
            return getTempDirImpl(executable);
        }    
    }    
     
    /**
     * Utilizing {@link File#createTempFile(String, String, File)} using
     * {@link #getTempRoot(AccessControlContext, boolean)} as the directory parameter, ie. location 
     * of the root temp folder.
     * 
     * @see File#createTempFile(String, String)
     * @see File#createTempFile(String, String, File)
     * @see #getTempRoot(AccessControlContext, boolean)
     * 
     * @param prefix
     * @param suffix
     * @param executable true if the temporary root folder needs to hold executable files, otherwise false.
     * @return
     * @throws IllegalArgumentException
     * @throws IOException
     * @throws SecurityException
     */
    public static File createTempFile(String prefix, String suffix, boolean executable, AccessControlContext acc) 
        throws IllegalArgumentException, IOException, SecurityException 
    {        
        return File.createTempFile( prefix, suffix, getTempDir(executable, acc) );
    }

    public static void close(Closeable stream, boolean throwRuntimeException) throws RuntimeException {
        if(null != stream) {
            try {
                stream.close();
            } catch (IOException e) {
                if(throwRuntimeException) {
                    throw new RuntimeException(e);
                } else if(DEBUG) {
                    System.err.println("Catched Exception: ");
                    e.printStackTrace();
                }
            }
        }        
    }
}