Copyright (c) 2010, 2017 IBM Corporation and others.
This program and the accompanying materials
are made available under the terms of the Eclipse Public License 2.0
which accompanies this distribution, and is available at
https://www.eclipse.org/legal/epl-2.0/
SPDX-License-Identifier: EPL-2.0
Contributors:
    IBM Corporation - initial API and implementation
    Sergey Prigogin (Google) - ongoing development
/*******************************************************************************
 * Copyright (c) 2010, 2017 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *     Sergey Prigogin (Google) - ongoing development
 *******************************************************************************/
package org.eclipse.core.internal.filesystem.local.unix;

import java.io.File;
import java.net.URL;
import java.nio.charset.StandardCharsets;
import java.util.Enumeration;
import org.eclipse.core.filesystem.EFS;
import org.eclipse.core.filesystem.IFileInfo;
import org.eclipse.core.filesystem.provider.FileInfo;
import org.eclipse.core.internal.filesystem.*;
import org.eclipse.core.internal.filesystem.local.Convert;
import org.eclipse.core.runtime.IStatus;
import org.eclipse.osgi.util.NLS;

public abstract class UnixFileNatives {
	private static final String LIBRARY_NAME = "unixfile_1_0_0"; //$NON-NLS-1$
	private static final int UNICODE_SUPPORTED = 1 << 0;
	private static final int CHFLAGS_SUPPORTED = 1 << 1;
	private static final int ENOENT = 2; // errno value for "No such file or directory"

	private static final boolean usingNatives;
	private static final int libattr;

	static {
		boolean _usingNatives = false;
		int _libattr = 0;
		try {
			System.loadLibrary(LIBRARY_NAME);
			_usingNatives = true;
			initializeStructStatFieldIDs();
			_libattr = libattr();
		} catch (UnsatisfiedLinkError e) {
			if (isLibraryPresent())
				logMissingNativeLibrary(e);
		} finally {
			usingNatives = _usingNatives;
			libattr = _libattr;
		}
	}

	private static boolean isLibraryPresent() {
		String libName = System.mapLibraryName(LIBRARY_NAME);
		Enumeration<URL> entries = FileSystemAccess.findEntries("/", libName, true); //$NON-NLS-1$
		return entries != null && entries.hasMoreElements();
	}

	private static void logMissingNativeLibrary(UnsatisfiedLinkError e) {
		String libName = System.mapLibraryName(LIBRARY_NAME);
		String message = NLS.bind(Messages.couldNotLoadLibrary, libName);
		Policy.log(IStatus.INFO, message, e);
	}

	public static int getSupportedAttributes() {
		if (!usingNatives)
			return -1;
		int ret = EFS.ATTRIBUTE_READ_ONLY | EFS.ATTRIBUTE_EXECUTABLE | EFS.ATTRIBUTE_SYMLINK | EFS.ATTRIBUTE_LINK_TARGET | EFS.ATTRIBUTE_OWNER_READ | EFS.ATTRIBUTE_OWNER_WRITE | EFS.ATTRIBUTE_OWNER_EXECUTE | EFS.ATTRIBUTE_GROUP_READ | EFS.ATTRIBUTE_GROUP_WRITE | EFS.ATTRIBUTE_GROUP_EXECUTE | EFS.ATTRIBUTE_OTHER_READ | EFS.ATTRIBUTE_OTHER_WRITE | EFS.ATTRIBUTE_OTHER_EXECUTE;
		if (isSupported(CHFLAGS_SUPPORTED))
			ret |= EFS.ATTRIBUTE_IMMUTABLE;
		return ret;
	}

	public static FileInfo fetchFileInfo(String fileName) {
		FileInfo info = null;
		byte[] name = fileNameToBytes(fileName);
		StructStat stat = new StructStat();
		if (lstat(name, stat) == 0) {
			if ((stat.st_mode & UnixFileFlags.S_IFMT) == UnixFileFlags.S_IFLNK) {
				if (stat(name, stat) == 0) {
					info = stat.toFileInfo();
				} else {
					info = new FileInfo();
					if (getErrno() != ENOENT)
						info.setError(IFileInfo.IO_ERROR);
				}
				info.setAttribute(EFS.ATTRIBUTE_SYMLINK, true);
				byte target[] = new byte[UnixFileFlags.PATH_MAX];
				int length = readlink(name, target, target.length);
				if (length > 0)
					info.setStringAttribute(EFS.ATTRIBUTE_LINK_TARGET, bytesToFileName(target, length));
			} else
				info = stat.toFileInfo();
		} else {
			info = new FileInfo();
			if (getErrno() != ENOENT)
				info.setError(IFileInfo.IO_ERROR);
		}

		if (info.getName() == null) {
			// If the file system is case insensitive, we don't know the real name of the file.
			// Since obtaining the real name in such situation is pretty expensive, we use the name
			// passed as a parameter, which may differ by case from the real name of the file
			// if the file system is case insensitive.
			File file = new File(fileName);
			info.setName(file.getName());
		}
		return info;
	}

	public static boolean putFileInfo(String fileName, IFileInfo info, int options) {
		int code = 0;
		byte[] name = fileNameToBytes(fileName);
		if (name == null)
			return false;

		// In case uchg flag is to be removed do it before calling chmod
		if (!info.getAttribute(EFS.ATTRIBUTE_IMMUTABLE) && isSupported(CHFLAGS_SUPPORTED)) {
			StructStat stat = new StructStat();
			if (stat(name, stat) == 0) {
				long flags = stat.st_flags;
				flags &= ~UnixFileFlags.SF_IMMUTABLE;
				flags &= ~UnixFileFlags.UF_IMMUTABLE;
				code |= chflags(name, (int) flags);
			}
		}

		// Change permissions
		int mode = 0;
		if (info.getAttribute(EFS.ATTRIBUTE_OWNER_READ))
			mode |= UnixFileFlags.S_IRUSR;
		if (info.getAttribute(EFS.ATTRIBUTE_OWNER_WRITE))
			mode |= UnixFileFlags.S_IWUSR;
		if (info.getAttribute(EFS.ATTRIBUTE_OWNER_EXECUTE))
			mode |= UnixFileFlags.S_IXUSR;
		if (info.getAttribute(EFS.ATTRIBUTE_GROUP_READ))
			mode |= UnixFileFlags.S_IRGRP;
		if (info.getAttribute(EFS.ATTRIBUTE_GROUP_WRITE))
			mode |= UnixFileFlags.S_IWGRP;
		if (info.getAttribute(EFS.ATTRIBUTE_GROUP_EXECUTE))
			mode |= UnixFileFlags.S_IXGRP;
		if (info.getAttribute(EFS.ATTRIBUTE_OTHER_READ))
			mode |= UnixFileFlags.S_IROTH;
		if (info.getAttribute(EFS.ATTRIBUTE_OTHER_WRITE))
			mode |= UnixFileFlags.S_IWOTH;
		if (info.getAttribute(EFS.ATTRIBUTE_OTHER_EXECUTE))
			mode |= UnixFileFlags.S_IXOTH;
		code |= chmod(name, mode);

		// In case uchg flag is to be added do it after calling chmod
		if (info.getAttribute(EFS.ATTRIBUTE_IMMUTABLE) && isSupported(CHFLAGS_SUPPORTED)) {
			StructStat stat = new StructStat();
			if (stat(name, stat) == 0) {
				long flags = stat.st_flags;
				flags |= UnixFileFlags.UF_IMMUTABLE;
				code |= chflags(name, (int) flags);
			}
		}
		return code == 0;
	}

	public static boolean isUsingNatives() {
		return usingNatives;
	}

	public static int getErrno() {
		return errno();
	}

	public static int getFlag(String flag) {
		if (!usingNatives)
			return -1;
		return getflag(flag.getBytes(StandardCharsets.US_ASCII));
	}

	private static byte[] fileNameToBytes(String fileName) {
		if (isSupported(UNICODE_SUPPORTED))
			return tounicode(fileName.toCharArray());
		return Convert.toPlatformBytes(fileName);
	}

	private static String bytesToFileName(byte[] buf, int length) {
		if (isSupported(UNICODE_SUPPORTED))
			return new String(buf, 0, length);
		return Convert.fromPlatformBytes(buf, length);
	}

	private static boolean isSupported(int attr) {
		return (libattr & attr) != 0;
	}

	private static final native void initializeStructStatFieldIDs();

	private static final native int chmod(byte[] path, int mode);

	private static final native int chflags(byte[] path, int flags);

	private static final native int stat(byte[] path, StructStat buf);

	private static final native int lstat(byte[] path, StructStat buf);

	private static final native int readlink(byte[] path, byte[] buf, long bufsiz);

	private static final native int errno();

	private static final native int libattr();

	private static final native byte[] tounicode(char[] buf);

	private static final native int getflag(byte[] buf);

}