/*
 * Copyright (c) 2001, 2025, 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.nio.file.InvalidPathException;
import java.nio.file.Path;
import java.util.BitSet;
import java.util.Locale;
import java.util.Properties;

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

    private static final String LONG_PATH_PREFIX = "\\\\?\\";

    private static final boolean ALLOW_DELETE_READ_ONLY_FILES =
        Boolean.getBoolean("jdk.io.File.allowDeleteReadOnlyFiles");

    private final char slash;
    private final char altSlash;
    private final char semicolon;
    private final String userDir;

    // Whether to enable alternative data streams (ADS) by suppressing
    // checking the path for invalid characters, in particular ":".
    // By default, ADS support is enabled and will be disabled if and
    // only if the property is set, ignoring case, to the string "false".
    private static final boolean ENABLE_ADS;
    static {
        String enableADS = System.getProperty("jdk.io.File.enableADS");
        if (enableADS != null) {
            ENABLE_ADS = !enableADS.equalsIgnoreCase(Boolean.FALSE.toString());
        } else {
            ENABLE_ADS = true;
        }
    }

    // Strip a long path or UNC prefix and return the result.
    // If there is no such prefix, return the parameter passed in.
    private static String stripLongOrUNCPrefix(String path) {
        // if a prefix is present, remove it
        if (path.startsWith(LONG_PATH_PREFIX)) {
            if (path.startsWith("UNC\\", 4)) {
                path = "\\\\" + path.substring(8);
            } else {
                path = path.substring(4);
                // if only "UNC" remains, a trailing "\\" was likely removed
                if (path.equals("UNC")) {
                    path = "\\\\";
                }
            }
        }

        return path;
    }

    private String getPathForWin32Calls(String path) {
        return (path != null && path.isEmpty()) ? getCWD().getPath() : path;
    }

    private File getFileForWin32Calls(File file) {
        return file.getPath().isEmpty() ? getCWD() : file;
    }

    WinNTFileSystem() {
        Properties props = System.getProperties();
        slash = props.getProperty("file.separator").charAt(0);
        semicolon = props.getProperty("path.separator").charAt(0);
        altSlash = (this.slash == '\\') ? '/' : '\\';
        userDir = normalize(props.getProperty("user.dir"));
    }

    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.isEmpty() && 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) {
        path = stripLongOrUNCPrefix(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) {
        assert !path.startsWith(LONG_PATH_PREFIX);

        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) {
        assert !child.startsWith(LONG_PATH_PREFIX);

        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);
        }

        // if present, strip trailing name separator unless after a ':'
        if (theChars.length > 1
            && theChars[theChars.length - 1] == slash
            && theChars[theChars.length - 2] != ':')
            return new String(theChars, 0, theChars.length - 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) {
        String path = f.getPath();
        assert !path.startsWith(LONG_PATH_PREFIX);

        int pl = f.getPrefixLength();
        return (((pl == 2) && (f.getPath().charAt(0) == slash))
                || (pl == 3));
    }

    @Override
    public boolean isInvalid(File f) {
        final String pathname = f.getPath();

        // Invalid if the pathname string contains a null character or if
        // any name in the pathname's name sequence ends with a space
        if (pathname.indexOf('\u0000') >= 0 || pathname.endsWith(" ")
            || pathname.contains(" \\"))
            return true;

        // The remaining checks are irrelevant for alternate data streams (ADS)
        if (ENABLE_ADS)
            return false;

        // Invalid if there is a ":" at a position other than 1, or if there
        // is a ":" at position 1 and the first character is not a letter
        int lastColon = pathname.lastIndexOf(":");
        if (lastColon >= 0 &&
            (lastColon != 1 || !isLetter(pathname.charAt(0))))
            return true;

        // Invalid if the path string cannot be converted to a Path
        try {
            Path path = sun.nio.fs.DefaultFileSystemProvider.theFileSystem().getPath(pathname);
            return false;
        } catch (InvalidPathException ignored) {
        }

        return true;
    }

    @Override
    public String resolve(File f) {
        String path = f.getPath();
        assert !path.startsWith(LONG_PATH_PREFIX);

        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 userDir + slashify(path); /* Completely relative */
        if (pl == 1) {                          /* Drive-relative */
            String up = userDir;
            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 = userDir;
            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);
            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)));
                return p;
            }
            return drive + ":" + slashify(path.substring(2)); /* fake it */
        }
        throw new InternalError("Unresolvable path: " + path);
    }

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

    private static final String[] DRIVE_DIR_CACHE = 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;
        // Updates might not be visible to other threads so there
        // is no guarantee getDriveDirectory(i+1) is called just once
        // for any given value of i.
        String s = DRIVE_DIR_CACHE[i];
        if (s != null) return s;
        s = getDriveDirectory(i + 1);
        DRIVE_DIR_CACHE[i] = s;
        return s;

    }

    @Override
    public String canonicalize(String path) throws IOException {
        assert !path.startsWith(LONG_PATH_PREFIX);

        // 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)) + ':' + '\\';
        }
        String canonicalPath = canonicalize0(path);
        String finalPath = null;
        try {
            finalPath = getFinalPath(canonicalPath);
        } catch (IOException ignored) {
            finalPath = canonicalPath;
        }
        return finalPath;
    }

    private native String canonicalize0(String path)
            throws IOException;

    private String getFinalPath(String path) throws IOException {
        return getFinalPath0(path);
    }

    private native String getFinalPath0(String path)
            throws IOException;


    /* -- Attribute accessors -- */

    @Override
    public int getBooleanAttributes(File f) {
        return getBooleanAttributes0(getFileForWin32Calls(f));
    }
    private native int getBooleanAttributes0(File f);

    @Override
    public boolean checkAccess(File f, int access) {
        return checkAccess0(getFileForWin32Calls(f), access);
    }
    private native boolean checkAccess0(File f, int access);

    @Override
    public long getLastModifiedTime(File f) {
        return getLastModifiedTime0(getFileForWin32Calls(f));
    }
    private native long getLastModifiedTime0(File f);

    @Override
    public long getLength(File f) {
        return getLength0(getFileForWin32Calls(f));
    }
    private native long getLength0(File f);

    @Override
    public boolean setPermission(File f, int access, boolean enable, boolean owneronly) {
        return setPermission0(getFileForWin32Calls(f), access, enable, owneronly);
    }
    private native boolean setPermission0(File f, int access, boolean enable, boolean owneronly);

    /* -- File operations -- */

    @Override
    public boolean createFileExclusively(String path) throws IOException {
        return createFileExclusively0(path);
    }
    private native boolean createFileExclusively0(String path) throws IOException;

    @Override
    public String[] list(File f) {
        return list0(getFileForWin32Calls(f));
    }
    private native String[] list0(File f);

    @Override
    public boolean createDirectory(File f) {
        return createDirectory0(f);
    }
    private native boolean createDirectory0(File f);

    @Override
    public boolean setLastModifiedTime(File f, long time) {
        return setLastModifiedTime0(getFileForWin32Calls(f), time);
    }
    private native boolean setLastModifiedTime0(File f, long time);

    @Override
    public boolean setReadOnly(File f) {
        return setReadOnly0(f);
    }
    private native boolean setReadOnly0(File f);

    @Override
    public boolean delete(File f) {
        return delete0(f, ALLOW_DELETE_READ_ONLY_FILES);
    }
    private native boolean delete0(File f, boolean allowDeleteReadOnlyFiles);

    @Override
    public boolean rename(File f1, File f2) {
        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))
            .toArray(File[]::new);
    }
    private static native int listRoots0();

    /* -- Disk usage -- */

    @Override
    public long getSpace(File f, int t) {
        if (f.exists()) {
            // the value for the number of bytes of free space returned by the
            // native layer is not used here as it represents the number of free
            // bytes not considering quotas, whereas the value returned for the
            // number of usable bytes does respect quotas, and it is required
            // that free space <= total space
            if (t == SPACE_FREE)
                t = SPACE_USABLE;
            return getSpace0(getFileForWin32Calls(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);

    @Override
    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(getPathForWin32Calls(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();
    }
}