/*
 * Copyright (c) 1998, 2022, 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 pathname contains no duplicate slashes and does not end
       with a slash.  It may be the empty string. */

    /* Normalize the given pathname, whose length is len, starting at the given
       offset; everything before this offset is already normal. */
    private String normalize(String pathname, int len, int off) {
        if (len == 0) return pathname;
        int n = len;
        while ((n > 0) && (pathname.charAt(n - 1) == '/')) n--;
        if (n == 0) return "/";
        StringBuffer sb = new StringBuffer(pathname.length());
        if (off > 0) sb.append(pathname.substring(0, off));
        char prevChar = 0;
        for (int i = off; i < n; i++) {
            char c = pathname.charAt(i);
            if ((prevChar == '/') && (c == '/')) continue;
            sb.append(c);
            prevChar = c;
        }
        return sb.toString();
    }

    /* Check that the given pathname is normal.  If not, invoke the real
       normalizer on the part of the pathname that requires normalization.
       This way we iterate through the whole pathname string only once. */
    public String normalize(String pathname) {
        int n = pathname.length();
        char prevChar = 0;
        for (int i = 0; i < n; i++) {
            char c = pathname.charAt(i);
            if ((prevChar == '/') && (c == '/'))
                return normalize(pathname, n, i - 1);
            prevChar = c;
        }
        if (prevChar == '/') return normalize(pathname, n, n - 1);
        return pathname;
    }

    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);
    }

    @Override
    public boolean isInvalid(File f) {
        return f.getPath().indexOf('\u0000') < 0 ? false : true;
    }

    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();
    }

}
