/*
 * Copyright (c) 2001, 2017, 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.io.File;
import java.nio.file.Path;
import java.util.BitSet;
import java.util.Locale;
import java.util.Properties;
import sun.security.action.GetPropertyAction;

/**
 * Unicode-aware FileSystem for Windows NT/2000.
 *
 * @author Konstantin Kladko
 * @since 1.4
 */
class WinNTFileSystem extends FileSystem {

    private final char slash;
    private final char altSlash;
    private final char semicolon;

    public WinNTFileSystem() {
        Properties props = GetPropertyAction.privilegedGetProperties();
        slash = props.getProperty("file.separator").charAt(0);
        semicolon = props.getProperty("path.separator").charAt(0);
        altSlash = (this.slash == '\\') ? '/' : '\\';
    }

    private boolean isSlash(char c) {
        return (c == '\\') || (c == '/');
    }

    private boolean isLetter(char c) {
        return ((c >= 'a') && (c <= 'z')) || ((c >= 'A') && (c <= 'Z'));
    }

    private String slashify(String p) {
        if ((p.length() > 0) && (p.charAt(0) != slash)) return slash + p;
        else return p;
    }

    /* -- Normalization and construction -- */

    @Override
    public char getSeparator() {
        return slash;
    }

    @Override
    public char getPathSeparator() {
        return semicolon;
    }

    /* 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. */
    @Override
    public String normalize(String path) {
        int n = path.length();
        char slash = this.slash;
        char altSlash = this.altSlash;
        char prev = 0;
        for (int i = 0; i < n; i++) {
            char c = path.charAt(i);
            if (c == altSlash)
                return normalize(path, n, (prev == slash) ? i - 1 : i);
            if ((c == slash) && (prev == slash) && (i > 1))
                return normalize(path, n, i - 1);
            if ((c == ':') && (i > 1))
                return normalize(path, n, 0);
            prev = c;
        }
        if (prev == slash) return normalize(path, n, n - 1);
        return path;
    }

    /* Normalize the given pathname, whose length is len, starting at the given
       offset; everything before this offset is already normal. */
    private String normalize(String path, int len, int off) {
        if (len == 0) return path;
        if (off < 3) off = 0;   /* Avoid fencepost cases with UNC pathnames */
        int src;
        char slash = this.slash;
        StringBuilder sb = new StringBuilder(len);

        if (off == 0) {
            /* Complete normalization, including prefix */
            src = normalizePrefix(path, len, sb);
        } else {
            /* Partial normalization */
            src = off;
            sb.append(path, 0, off);
        }

        /* Remove redundant slashes from the remainder of the path, forcing all
           slashes into the preferred slash */
        while (src < len) {
            char c = path.charAt(src++);
            if (isSlash(c)) {
                while ((src < len) && isSlash(path.charAt(src))) src++;
                if (src == len) {
                    /* Check for trailing separator */
                    int sn = sb.length();
                    if ((sn == 2) && (sb.charAt(1) == ':')) {
                        /* "z:\\" */
                        sb.append(slash);
                        break;
                    }
                    if (sn == 0) {
                        /* "\\" */
                        sb.append(slash);
                        break;
                    }
                    if ((sn == 1) && (isSlash(sb.charAt(0)))) {
                        /* "\\\\" is not collapsed to "\\" because "\\\\" marks
                           the beginning of a UNC pathname.  Even though it is
                           not, by itself, a valid UNC pathname, we leave it as
                           is in order to be consistent with the win32 APIs,
                           which treat this case as an invalid UNC pathname
                           rather than as an alias for the root directory of
                           the current drive. */
                        sb.append(slash);
                        break;
                    }
                    /* Path does not denote a root directory, so do not append
                       trailing slash */
                    break;
                } else {
                    sb.append(slash);
                }
            } else {
                sb.append(c);
            }
        }

        return sb.toString();
    }

    /* A normal Win32 pathname contains no duplicate slashes, except possibly
       for a UNC prefix, and does not end with a slash.  It may be the empty
       string.  Normalized Win32 pathnames have the convenient property that
       the length of the prefix almost uniquely identifies the type of the path
       and whether it is absolute or relative:

           0  relative to both drive and directory
           1  drive-relative (begins with '\\')
           2  absolute UNC (if first char is '\\'),
                else directory-relative (has form "z:foo")
           3  absolute local pathname (begins with "z:\\")
     */
    private int normalizePrefix(String path, int len, StringBuilder sb) {
        int src = 0;
        while ((src < len) && isSlash(path.charAt(src))) src++;
        char c;
        if ((len - src >= 2)
            && isLetter(c = path.charAt(src))
            && path.charAt(src + 1) == ':') {
            /* Remove leading slashes if followed by drive specifier.
               This hack is necessary to support file URLs containing drive
               specifiers (e.g., "file://c:/path").  As a side effect,
               "/c:/path" can be used as an alternative to "c:/path". */
            sb.append(c);
            sb.append(':');
            src += 2;
        } else {
            src = 0;
            if ((len >= 2)
                && isSlash(path.charAt(0))
                && isSlash(path.charAt(1))) {
                /* UNC pathname: Retain first slash; leave src pointed at
                   second slash so that further slashes will be collapsed
                   into the second slash.  The result will be a pathname
                   beginning with "\\\\" followed (most likely) by a host
                   name. */
                src = 1;
                sb.append(slash);
            }
        }
        return src;
    }

    @Override
    public int prefixLength(String path) {
        char slash = this.slash;
        int n = path.length();
        if (n == 0) return 0;
        char c0 = path.charAt(0);
        char c1 = (n > 1) ? path.charAt(1) : 0;
        if (c0 == slash) {
            if (c1 == slash) return 2;  /* Absolute UNC pathname "\\\\foo" */
            return 1;                   /* Drive-relative "\\foo" */
        }
        if (isLetter(c0) && (c1 == ':')) {
            if ((n > 2) && (path.charAt(2) == slash))
                return 3;               /* Absolute local pathname "z:\\foo" */
            return 2;                   /* Directory-relative "z:foo" */
        }
        return 0;                       /* Completely relative */
    }

    @Override
    public String resolve(String parent, String child) {
        int pn = parent.length();
        if (pn == 0) return child;
        int cn = child.length();
        if (cn == 0) return parent;

        String c = child;
        int childStart = 0;
        int parentEnd = pn;

        boolean isDirectoryRelative =
            pn == 2 && isLetter(parent.charAt(0)) && parent.charAt(1) == ':';

        if ((cn > 1) && (c.charAt(0) == slash)) {
            if (c.charAt(1) == slash) {
                /* Drop prefix when child is a UNC pathname */
                childStart = 2;
            } else if (!isDirectoryRelative) {
                /* Drop prefix when child is drive-relative */
                childStart = 1;

            }
            if (cn == childStart) { // Child is double slash
                if (parent.charAt(pn - 1) == slash)
                    return parent.substring(0, pn - 1);
                return parent;
            }
        }

        if (parent.charAt(pn - 1) == slash)
            parentEnd--;

        int strlen = parentEnd + cn - childStart;
        char[] theChars = null;
        if (child.charAt(childStart) == slash || isDirectoryRelative) {
            theChars = new char[strlen];
            parent.getChars(0, parentEnd, theChars, 0);
            child.getChars(childStart, cn, theChars, parentEnd);
        } else {
            theChars = new char[strlen + 1];
            parent.getChars(0, parentEnd, theChars, 0);
            theChars[parentEnd] = slash;
            child.getChars(childStart, cn, theChars, parentEnd + 1);
        }
        return new String(theChars);
    }

    @Override
    public String getDefaultParent() {
        return ("" + slash);
    }

    @Override
    public String fromURIPath(String path) {
        String p = path;
        if ((p.length() > 2) && (p.charAt(2) == ':')) {
            // "/c:/foo" --> "c:/foo"
            p = p.substring(1);
            // "c:/foo/" --> "c:/foo", but "c:/" --> "c:/"
            if ((p.length() > 3) && p.endsWith("/"))
                p = p.substring(0, p.length() - 1);
        } else if ((p.length() > 1) && p.endsWith("/")) {
            // "/foo/" --> "/foo"
            p = p.substring(0, p.length() - 1);
        }
        return p;
    }

    /* -- Path operations -- */

    @Override
    public boolean isAbsolute(File f) {
        int pl = f.getPrefixLength();
        return (((pl == 2) && (f.getPath().charAt(0) == slash))
                || (pl == 3));
    }

    @Override
    public String resolve(File f) {
        String path = f.getPath();
        int pl = f.getPrefixLength();
        if ((pl == 2) && (path.charAt(0) == slash))
            return path;                        /* UNC */
        if (pl == 3)
            return path;                        /* Absolute local */
        if (pl == 0)
            return getUserPath() + slashify(path); /* Completely relative */
        if (pl == 1) {                          /* Drive-relative */
            String up = getUserPath();
            String ud = getDrive(up);
            if (ud != null) return ud + path;
            return up + path;                   /* User dir is a UNC path */
        }
        if (pl == 2) {                          /* Directory-relative */
            String up = getUserPath();
            String ud = getDrive(up);
            if ((ud != null) && path.startsWith(ud))
                return up + slashify(path.substring(2));
            char drive = path.charAt(0);
            String dir = getDriveDirectory(drive);
            String np;
            if (dir != null) {
                /* When resolving a directory-relative path that refers to a
                   drive other than the current drive, insist that the caller
                   have read permission on the result */
                String p = drive + (':' + dir + slashify(path.substring(2)));
                SecurityManager security = System.getSecurityManager();
                try {
                    if (security != null) security.checkRead(p);
                } catch (SecurityException x) {
                    /* Don't disclose the drive's directory in the exception */
                    throw new SecurityException("Cannot resolve path " + path);
                }
                return p;
            }
            return drive + ":" + slashify(path.substring(2)); /* fake it */
        }
        throw new InternalError("Unresolvable path: " + path);
    }

    private String getUserPath() {
        /* For both compatibility and security,
           we must look this up every time */
        return normalize(System.getProperty("user.dir"));
    }

    private String getDrive(String path) {
        int pl = prefixLength(path);
        return (pl == 3) ? path.substring(0, 2) : null;
    }

    private static String[] driveDirCache = new String[26];

    private static int driveIndex(char d) {
        if ((d >= 'a') && (d <= 'z')) return d - 'a';
        if ((d >= 'A') && (d <= 'Z')) return d - 'A';
        return -1;
    }

    private native String getDriveDirectory(int drive);

    private String getDriveDirectory(char drive) {
        int i = driveIndex(drive);
        if (i < 0) return null;
        String s = driveDirCache[i];
        if (s != null) return s;
        s = getDriveDirectory(i + 1);
        driveDirCache[i] = s;
        return s;
    }

    // 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();
    private ExpiringCache prefixCache = new ExpiringCache();

    @Override
    public String canonicalize(String path) throws IOException {
        // If path is a drive letter only then skip canonicalization
        int len = path.length();
        if ((len == 2) &&
            (isLetter(path.charAt(0))) &&
            (path.charAt(1) == ':')) {
            char c = path.charAt(0);
            if ((c >= 'A') && (c <= 'Z'))
                return path;
            return "" + ((char) (c-32)) + ':';
        } else if ((len == 3) &&
                   (isLetter(path.charAt(0))) &&
                   (path.charAt(1) == ':') &&
                   (path.charAt(2) == '\\')) {
            char c = path.charAt(0);
            if ((c >= 'A') && (c <= 'Z'))
                return path;
            return "" + ((char) (c-32)) + ':' + '\\';
        }
        if (!useCanonCaches) {
            return canonicalize0(path);
        } else {
            String res = cache.get(path);
            if (res == null) {
                String dir = null;
                String resDir = null;
                if (useCanonPrefixCache) {
                    dir = parentOrNull(path);
                    if (dir != null) {
                        resDir = prefixCache.get(dir);
                        if (resDir != null) {
                            /*
                             * Hit only in prefix cache; full path is canonical,
                             * but we need to get the canonical name of the file
                             * in this directory to get the appropriate
                             * capitalization
                             */
                            String filename = path.substring(1 + dir.length());
                            res = canonicalizeWithPrefix(resDir, filename);
                            cache.put(dir + File.separatorChar + filename, res);
                        }
                    }
                }
                if (res == null) {
                    res = canonicalize0(path);
                    cache.put(path, res);
                    if (useCanonPrefixCache && dir != null) {
                        resDir = parentOrNull(res);
                        if (resDir != null) {
                            File f = new File(res);
                            if (f.exists() && !f.isDirectory()) {
                                prefixCache.put(dir, resDir);
                            }
                        }
                    }
                }
            }
            return res;
        }
    }

    private native String canonicalize0(String path)
            throws IOException;

    private String canonicalizeWithPrefix(String canonicalPrefix,
            String filename) throws IOException
    {
        return canonicalizeWithPrefix0(canonicalPrefix,
                canonicalPrefix + File.separatorChar + filename);
    }

    // Run the canonicalization operation assuming that the prefix
    // (everything up to the last filename) is canonical; just gets
    // the canonical name of the last element of the path
    private native String canonicalizeWithPrefix0(String canonicalPrefix,
            String pathWithCanonicalPrefix)
            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.
    private static String parentOrNull(String path) {
        if (path == null) return null;
        char sep = File.separatorChar;
        char altSep = '/';
        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;
                }
                if (nonDotCount == 0) {
                    // Punt on pathnames ending in a .
                    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 ||
                    path.charAt(idx - 1) == altSep) {
                    // Punt on pathnames containing adjacent slashes
                    // toward the end
                    return null;
                }
                return path.substring(0, idx);
            } else if (c == altSep) {
                // Punt on pathnames containing both backward and
                // forward slashes
                return null;
            } else if (c == '*' || c == '?') {
                // Punt on pathnames containing wildcards
                return null;
            } else {
                ++nonDotCount;
                adjacentDots = 0;
            }
            --idx;
        }
        return null;
    }

    /* -- Attribute accessors -- */

    @Override
    public native int getBooleanAttributes(File f);

    @Override
    public native boolean checkAccess(File f, int access);

    @Override
    public native long getLastModifiedTime(File f);

    @Override
    public native long getLength(File f);

    @Override
    public native boolean setPermission(File f, int access, boolean enable,
            boolean owneronly);

    /* -- File operations -- */

    @Override
    public native boolean createFileExclusively(String path)
            throws IOException;

    @Override
    public native String[] list(File f);

    @Override
    public native boolean createDirectory(File f);

    @Override
    public native boolean setLastModifiedTime(File f, long time);

    @Override
    public native boolean setReadOnly(File f);

    @Override
    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();
        prefixCache.clear();
        return delete0(f);
    }

    private native boolean delete0(File f);

    @Override
    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();
        prefixCache.clear();
        return rename0(f1, f2);
    }

    private native boolean rename0(File f1, File f2);

    /* -- Filesystem interface -- */

    @Override
    public File[] listRoots() {
        return BitSet
            .valueOf(new long[] {listRoots0()})
            .stream()
            .mapToObj(i -> new File((char)('A' + i) + ":" + slash))
            .filter(f -> access(f.getPath()) && f.exists())
            .toArray(File[]::new);
    }

    private static native int listRoots0();

    private boolean access(String path) {
        try {
            SecurityManager security = System.getSecurityManager();
            if (security != null) security.checkRead(path);
            return true;
        } catch (SecurityException x) {
            return false;
        }
    }

    /* -- Disk usage -- */

    @Override
    public long getSpace(File f, int t) {
        if (f.exists()) {
            return getSpace0(f, t);
        }
        return 0;
    }

    private native long getSpace0(File f, int t);

    /* -- Basic infrastructure -- */

    // Obtain maximum file component length from GetVolumeInformation which
    // expects the path to be null or a root component ending in a backslash
    private native int getNameMax0(String path);

    public int getNameMax(String path) {
        String s = null;
        if (path != null) {
            File f = new File(path);
            if (f.isAbsolute()) {
                Path root = f.toPath().getRoot();
                if (root != null) {
                    s = root.toString();
                    if (!s.endsWith("\\")) {
                        s = s + "\\";
                    }
                }
            }
        }
        return getNameMax0(s);
    }

    @Override
    public int compare(File f1, File f2) {
        return f1.getPath().compareToIgnoreCase(f2.getPath());
    }

    @Override
    public int hashCode(File f) {
        /* Could make this more efficient: String.hashCodeIgnoreCase */
        return f.getPath().toLowerCase(Locale.ENGLISH).hashCode() ^ 1234321;
    }

    private static native void initIDs();

    static {
        initIDs();
    }
}
