//
// Getdown - application installer, patcher and launcher
// Copyright (C) 2004-2018 Getdown authors
// https://github.com/threerings/getdown/blob/master/LICENSE

package com.threerings.getdown.util;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.PrintStream;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.Locale;

import javax.xml.bind.DatatypeConverter;

import java.security.MessageDigest;

import static com.threerings.getdown.Log.log;

/**
 * Useful routines for launching Java applications from within other Java
 * applications.
 */
public class LaunchUtil
{
    /** The directory into which a local VM installation should be unpacked. */
    public static final String LOCAL_JAVA_DIR = "jre";

    /**
     * Writes a <code>version.txt</code> file into the specified application directory and
     * attempts to relaunch Getdown in that directory which will cause it to upgrade to the newly
     * specified version and relaunch the application.
     *
     * @param appdir the directory in which the application is installed.
     * @param getdownJarName the name of the getdown jar file in the application directory. This is
     * probably <code>getdown-pro.jar</code> or <code>getdown-retro-pro.jar</code> if you are using
     * the results of the standard build.
     * @param newVersion the new version to which Getdown will update when it is executed.
     *
     * @return true if the relaunch succeeded, false if we were unable to relaunch due to being on
     * Windows 9x where we cannot launch subprocesses without waiting around for them to exit,
     * reading their stdout and stderr all the while. If true is returned, the application may exit
     * after making this call as it will be upgraded and restarted. If false is returned, the
     * application should tell the user that they must restart the application manually.
     *
     * @exception IOException thrown if we were unable to create the <code>version.txt</code> file
     * in the supplied application directory. If the version.txt file cannot be created, restarting
     * Getdown will not cause the application to be upgraded, so the application will have to
     * resort to telling the user that it is in a bad way.
     */
    public static boolean updateVersionAndRelaunch (
            File appdir, String getdownJarName, String newVersion)
        throws IOException
    {
        // create the file that instructs Getdown to upgrade
        File vfile = new File(appdir, "version.txt");
        try (PrintStream ps = new PrintStream(new FileOutputStream(vfile))) {
            ps.println(newVersion);
        }

        // make sure that we can find our getdown.jar file and can safely launch children
        File pro = new File(appdir, getdownJarName);
        if (mustMonitorChildren() || !pro.exists()) {
            return false;
        }

        // do the deed
        String[] args = new String[] {
            getJVMPath(appdir), "-jar", pro.toString(), appdir.getPath()
        };
        log.info("Running " + StringUtil.join(args, "\n  "));
        try {
            Runtime.getRuntime().exec(args, null);
            return true;
        } catch (IOException ioe) {
            log.warning("Failed to run getdown", ioe);
            return false;
        }
    }

    /**
     * Reconstructs the path to the JVM used to launch this process.
     */
    public static String getJVMPath (File appdir)
    {
        return getJVMPath(appdir, false);
    }

    /**
     * Reconstructs the path to the JVM used to launch this process.
     *
     * @param windebug if true we will use java.exe instead of javaw.exe on Windows.
     */
    public static String getJVMPath (File appdir, boolean windebug)
    {
        // first look in our application directory for an installed VM
        String vmpath = checkJVMPath(new File(appdir, LOCAL_JAVA_DIR).getAbsolutePath(), windebug);
        if (vmpath == null && isMacOS()) {
			vmpath = checkJVMPath(new File(appdir, LOCAL_JAVA_DIR + "/Contents/Home").getAbsolutePath(), windebug);
        }

        // then fall back to the VM in which we're already running
        if (vmpath == null) {
            vmpath = checkJVMPath(System.getProperty("java.home"), windebug);
        }

        // then throw up our hands and hope for the best
        if (vmpath == null) {
            log.warning("Unable to find java [appdir=" + appdir +
                        ", java.home=" + System.getProperty("java.home") + "]!");
            vmpath = "java";
        }

        // Oddly, the Mac OS X specific java flag -Xdock:name will only work if java is launched
        // from /usr/bin/java, and not if launched by directly referring to <java.home>/bin/java,
        // even though the former is a symlink to the latter! To work around this, see if the
        // desired jvm is in fact pointed to by /usr/bin/java and, if so, use that instead.
        if (isMacOS()) {
            try {
                File localVM = new File("/usr/bin/java").getCanonicalFile();
                if (localVM.equals(new File(vmpath).getCanonicalFile())) {
                    vmpath = "/usr/bin/java";
                }
            } catch (IOException ioe) {
                log.warning("Failed to check Mac OS canonical VM path.", ioe);
            }
        }

        return vmpath;
    }

    private static String _getMD5FileChecksum (File file) {
    	// check md5 digest
    	String algo = "MD5";
    	String checksum = "";
    	try {
    		MessageDigest md = MessageDigest.getInstance(algo);
    		md.update(Files.readAllBytes(Paths.get(file.getAbsolutePath())));
    		byte[] digest = md.digest();
    		checksum = DatatypeConverter.printHexBinary(digest).toUpperCase(Locale.ROOT);
    	} catch (Exception e) {
    		System.out.println("Couldn't create "+algo+" digest of "+file.getPath());
    	}
    	return checksum;
    }
    
    /**
     * Upgrades Getdown by moving an installation managed copy of the Getdown jar file over the
     * non-managed copy (which would be used to run Getdown itself).
     *
     * <p> If the upgrade fails for a variety of reasons, warnings are logged but no other actions
     * are taken. There's not much else one can do other than try again next time around.
     */
    public static void upgradeGetdown (File oldgd, File curgd, File newgd)
    {
        // we assume getdown's jar file size changes with every upgrade, this is not guaranteed,
        // but in reality it will, and it allows us to avoid pointlessly upgrading getdown every
        // time the client is updated which is unnecessarily flirting with danger
        if (!newgd.exists())
        {
            return;
        }
        
        if (newgd.length() == curgd.length()) {
        	if (_getMD5FileChecksum(newgd).equals(_getMD5FileChecksum(curgd)))
        	{
				return;
        	}
        }

        log.info("Updating Getdown with " + newgd + "...");

        // clear out any old getdown
        if (oldgd.exists()) {
            FileUtil.deleteHarder(oldgd);
        }

        // now try updating using renames
        if (!curgd.exists() || curgd.renameTo(oldgd)) {
            if (newgd.renameTo(curgd)) {
                FileUtil.deleteHarder(oldgd); // yay!
                try {
                    // copy the moved file back to getdown-dop-new.jar so that we don't end up
                    // downloading another copy next time
                    FileUtil.copy(curgd, newgd);
                } catch (IOException e) {
                    log.warning("Error copying updated Getdown back: " + e);
                }
                return;
            }

            log.warning("Unable to renameTo(" + oldgd + ").");
            // try to unfuck ourselves
            if (!oldgd.renameTo(curgd)) {
                log.warning("Oh God, why dost thee scorn me so.");
            }
        }

        // that didn't work, let's try copying it
        log.info("Attempting to upgrade by copying over " + curgd + "...");
        try {
            FileUtil.copy(newgd, curgd);
        } catch (IOException ioe) {
            log.warning("Mayday! Brute force copy method also failed.", ioe);
        }
    }

    /**
     * Returns true if, on this operating system, we have to stick around and read the stderr from
     * our children processes to prevent them from filling their output buffers and hanging.
     */
    public static boolean mustMonitorChildren ()
    {
        String osname = System.getProperty("os.name", "").toLowerCase(Locale.ROOT);
        return (osname.indexOf("windows 98") != -1 || osname.indexOf("windows me") != -1);
    }

    /**
     * Returns true if we're running in a JVM that identifies its operating system as Windows.
     */
    public static final boolean isWindows () { return _isWindows; }

    /**
     * Returns true if we're running in a JVM that identifies its operating system as MacOS.
     */
    public static final boolean isMacOS () { return _isMacOS; }

    /**
     * Returns true if we're running in a JVM that identifies its operating system as Linux.
     */
    public static final boolean isLinux () { return _isLinux; }

    /**
     * Check if a symlink (or file) points to a JVM
     */
    private static boolean checkJVMSymlink(String testBin)
    {
      File testBinFile = new File(testBin);
      if (!testBinFile.exists())
      {
        return false;
      }
      File targetFile = null;
      try
      {
        targetFile = testBinFile.getCanonicalFile();
      } catch (IOException e)
      {
        return false;
      }
      if (targetFile != null && ("java".equals(targetFile.getName())
            || "java.exe".equals(targetFile.getName())))
      {
        return true;
      }
      return false;
    }

    /**
     * Checks whether a Java Virtual Machine can be located in the supplied path.
     */
    protected static String checkJVMPath (String vmhome, boolean windebug)
    {
        String vmbase = vmhome + File.separator + "bin" + File.separator;
        String appName = System.getProperty("channel.app_name", "Jalview");
        String vmpath = vmbase + appName;
        if (checkJVMSymlink(vmpath)) {
          return vmpath;
        }
        vmpath = vmbase + "Jalview";
        if (checkJVMSymlink(vmpath)) {
          return vmpath;
        }
        vmpath = vmbase + "java";
        if (new File(vmpath).exists()) {
            return vmpath;
        }

        if (!windebug) {
            vmpath = vmbase + "javaw.exe";
            if (new File(vmpath).exists()) {
                return vmpath;
            }
        }

        vmpath = vmbase + "java.exe";
        if (new File(vmpath).exists()) {
            return vmpath;
        }

        return null;
    }

    /** Flag indicating that we're on Windows; initialized when this class is first loaded. */
    protected static boolean _isWindows;
    /** Flag indicating that we're on MacOS; initialized when this class is first loaded. */
    protected static boolean _isMacOS;
    /** Flag indicating that we're on Linux; initialized when this class is first loaded. */
    protected static boolean _isLinux;

    static {
        try {
            String osname = System.getProperty("os.name");
            osname = (osname == null) ? "" : osname;
            _isWindows = (osname.indexOf("Windows") != -1);
            _isMacOS = (osname.indexOf("Mac OS") != -1 ||
                        osname.indexOf("MacOS") != -1);
            _isLinux = (osname.indexOf("Linux") != -1);
        } catch (Exception e) {
            // can't grab system properties; we'll just pretend we're not on any of these OSes
        }
    }
}