/*
 * Copyright (c) 1998, 2013, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package java.io;

import java.security.AccessController;
import sun.security.action.GetPropertyAction;


class UnixFileSystem extends FileSystem {

    private final char slash;
    private final char colon;
    private final String javaHome;

    public UnixFileSystem() {
        slash = AccessController.doPrivileged(
            new GetPropertyAction("file.separator")).charAt(0);
        colon = AccessController.doPrivileged(
            new GetPropertyAction("path.separator")).charAt(0);
        javaHome = AccessController.doPrivileged(
            new GetPropertyAction("java.home"));
    }


    /* -- Normalization and construction -- */

    public char getSeparator() {
        return slash;
    }

    public char getPathSeparator() {
        return colon;
    }

    /*
     * A normal Unix path name contains no duplicate slashes and does not end
     * with a slash.  It may be the empty string. Check and normalize the
     * given pathname. The whole pathname string is only iterated once.
     */
    @Override
    public String normalize(String pathname) {
        final int len = pathname.length();
        StringBuilder sb = new StringBuilder(len);
        char prevChar = 0;

        for (int i = 0; i < len; i++) {
            char c = pathname.charAt(i);
            if (c == CHAR_NUL) continue;
            if ((prevChar == '/') && (c == '/')) continue;

            sb.append(c);
            prevChar = c;
        }

        if (prevChar == '/' && sb.length() > 1)
            sb.setLength(sb.length() - 1);

        return sb.toString();
    }

    public int prefixLength(String pathname) {
        if (pathname.length() == 0) return 0;
        return (pathname.charAt(0) == '/') ? 1 : 0;
    }

    public String resolve(String parent, String child) {
        if (child.equals("")) return parent;
        if (child.charAt(0) == '/') {
            if (parent.equals("/")) return child;
            return parent + child;
        }
        if (parent.equals("/")) return parent + child;
        return parent + '/' + child;
    }

    public String getDefaultParent() {
        return "/";
    }

    public String fromURIPath(String path) {
        String p = path;
        if (p.endsWith("/") && (p.length() > 1)) {
            // "/foo/" --> "/foo", but "/" --> "/"
            p = p.substring(0, p.length() - 1);
        }
        return p;
    }


    /* -- Path operations -- */

    public boolean isAbsolute(File f) {
        return (f.getPrefixLength() != 0);
    }

    public String resolve(File f) {
        if (isAbsolute(f)) return f.getPath();
        return resolve(System.getProperty("user.dir"), f.getPath());
    }

    // Caches for canonicalization results to improve startup performance.
    // The first cache handles repeated canonicalizations of the same path
    // name. The prefix cache handles repeated canonicalizations within the
    // same directory, and must not create results differing from the true
    // canonicalization algorithm in canonicalize_md.c. For this reason the
    // prefix cache is conservative and is not used for complex path names.
    private ExpiringCache cache = new ExpiringCache();
    // On Unix symlinks can jump anywhere in the file system, so we only
    // treat prefixes in java.home as trusted and cacheable in the
    // canonicalization algorithm
    private ExpiringCache javaHomePrefixCache = new ExpiringCache();

    public String canonicalize(String path) throws IOException {
        if (!useCanonCaches) {
            return canonicalize0(path);
        } else {
            String res = cache.get(path);
            if (res == null) {
                String dir = null;
                String resDir = null;
                if (useCanonPrefixCache) {
                    // Note that this can cause symlinks that should
                    // be resolved to a destination directory to be
                    // resolved to the directory they're contained in
                    dir = parentOrNull(path);
                    if (dir != null) {
                        resDir = javaHomePrefixCache.get(dir);
                        if (resDir != null) {
                            // Hit only in prefix cache; full path is canonical
                            String filename = path.substring(1 + dir.length());
                            res = resDir + slash + filename;
                            cache.put(dir + slash + filename, res);
                        }
                    }
                }
                if (res == null) {
                    res = canonicalize0(path);
                    cache.put(path, res);
                    if (useCanonPrefixCache &&
                        dir != null && dir.startsWith(javaHome)) {
                        resDir = parentOrNull(res);
                        // Note that we don't allow a resolved symlink
                        // to elsewhere in java.home to pollute the
                        // prefix cache (java.home prefix cache could
                        // just as easily be a set at this point)
                        if (resDir != null && resDir.equals(dir)) {
                            File f = new File(res);
                            if (f.exists() && !f.isDirectory()) {
                                javaHomePrefixCache.put(dir, resDir);
                            }
                        }
                    }
                }
            }
            return res;
        }
    }
    private native String canonicalize0(String path) throws IOException;
    // Best-effort attempt to get parent of this path; used for
    // optimization of filename canonicalization. This must return null for
    // any cases where the code in canonicalize_md.c would throw an
    // exception or otherwise deal with non-simple pathnames like handling
    // of "." and "..". It may conservatively return null in other
    // situations as well. Returning null will cause the underlying
    // (expensive) canonicalization routine to be called.
    static String parentOrNull(String path) {
        if (path == null) return null;
        char sep = File.separatorChar;
        int last = path.length() - 1;
        int idx = last;
        int adjacentDots = 0;
        int nonDotCount = 0;
        while (idx > 0) {
            char c = path.charAt(idx);
            if (c == '.') {
                if (++adjacentDots >= 2) {
                    // Punt on pathnames containing . and ..
                    return null;
                }
            } else if (c == sep) {
                if (adjacentDots == 1 && nonDotCount == 0) {
                    // Punt on pathnames containing . and ..
                    return null;
                }
                if (idx == 0 ||
                    idx >= last - 1 ||
                    path.charAt(idx - 1) == sep) {
                    // Punt on pathnames containing adjacent slashes
                    // toward the end
                    return null;
                }
                return path.substring(0, idx);
            } else {
                ++nonDotCount;
                adjacentDots = 0;
            }
            --idx;
        }
        return null;
    }

    /* -- Attribute accessors -- */

    public native int getBooleanAttributes0(File f);

    public int getBooleanAttributes(File f) {
        int rv = getBooleanAttributes0(f);
        String name = f.getName();
        boolean hidden = (name.length() > 0) && (name.charAt(0) == '.');
        return rv | (hidden ? BA_HIDDEN : 0);
    }

    public native boolean checkAccess(File f, int access);
    public native long getLastModifiedTime(File f);
    public native long getLength(File f);
    public native boolean setPermission(File f, int access, boolean enable, boolean owneronly);

    /* -- File operations -- */

    public native boolean createFileExclusively(String path)
        throws IOException;
    public boolean delete(File f) {
        // Keep canonicalization caches in sync after file deletion
        // and renaming operations. Could be more clever than this
        // (i.e., only remove/update affected entries) but probably
        // not worth it since these entries expire after 30 seconds
        // anyway.
        cache.clear();
        javaHomePrefixCache.clear();
        return delete0(f);
    }
    private native boolean delete0(File f);
    public native String[] list(File f);
    public native boolean createDirectory(File f);
    public boolean rename(File f1, File f2) {
        // Keep canonicalization caches in sync after file deletion
        // and renaming operations. Could be more clever than this
        // (i.e., only remove/update affected entries) but probably
        // not worth it since these entries expire after 30 seconds
        // anyway.
        cache.clear();
        javaHomePrefixCache.clear();
        return rename0(f1, f2);
    }
    private native boolean rename0(File f1, File f2);
    public native boolean setLastModifiedTime(File f, long time);
    public native boolean setReadOnly(File f);


    /* -- Filesystem interface -- */

    public File[] listRoots() {
        try {
            SecurityManager security = System.getSecurityManager();
            if (security != null) {
                security.checkRead("/");
            }
            return new File[] { new File("/") };
        } catch (SecurityException x) {
            return new File[0];
        }
    }

    /* -- Disk usage -- */
    public native long getSpace(File f, int t);

    /* -- Basic infrastructure -- */

    public int compare(File f1, File f2) {
        return f1.getPath().compareTo(f2.getPath());
    }

    public int hashCode(File f) {
        return f.getPath().hashCode() ^ 1234321;
    }


    private static native void initIDs();

    static {
        initIDs();
    }

}