/*
 * Copyright (c) 2012, 2014, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 */

package com.sun.javafx.font;

import java.io.File;
import java.io.RandomAccessFile;
import java.io.IOException;
import java.nio.file.Files;
import java.security.AccessController;
import java.security.PrivilegedActionException;
import java.security.PrivilegedExceptionAction;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.Semaphore;
import java.util.concurrent.TimeUnit;

/*
 * Utility class to write sfnt-based font files.
 *
 * To reduce the number of IO operation this class buffers the font header
 * and directory when the API writeHeader() and writeDirectoryEntry() are used.
 */
class FontFileWriter implements FontConstants {
    byte[] header;              // buffer for the header and directory
    int pos;                    // current position for the tables
    int headerPos;              // current buffer position in the header
    int writtenBytes;
    FontTracker tracker;
    File file;
    RandomAccessFile raFile;

    public FontFileWriter() {
        if (!hasTempPermission()) {
            tracker = FontTracker.getTracker();
        }
    }

    protected void setLength(int size) throws IOException {
        if (raFile == null) {
            throw new IOException("File not open");
        }
        checkTracker(size);
        raFile.setLength(size);
    }

    public void seek(int pos) throws IOException {
        if (raFile == null) {
            throw new IOException("File not open");
        }
        if (pos != this.pos) {
            raFile.seek(pos);
            this.pos = pos;
        }
    }

    public File getFile() {
        return file;
    }

    public File openFile() throws PrivilegedActionException {
        pos = 0;
        writtenBytes = 0;
        file = AccessController.doPrivileged(
                (PrivilegedExceptionAction<File>) () -> {
                    try {
                        return Files.createTempFile("+JXF", ".tmp").toFile();
                    } catch (IOException e) {
                        // don't reveal temporary directory location
                        throw new IOException("Unable to create temporary file");
                    }
                }
        );
        if (tracker != null) {
            tracker.add(file);
        }
        raFile = AccessController.doPrivileged(
                (PrivilegedExceptionAction<RandomAccessFile>) () -> new RandomAccessFile(file, "rw")
        );
        if (tracker != null) {
            tracker.set(file, raFile);
        }
        if (PrismFontFactory.debugFonts) {
            System.err.println("Temp file created: " + file.getPath());
        }
        return file;
    }

    public void closeFile() throws IOException {
        if (header != null) {
            raFile.seek(0);
            raFile.write(header);
            header = null;
        }
        if (raFile != null) {
            raFile.close();
            raFile = null;
        }
        if (tracker != null) {
            tracker.remove(file);
        }
    }

    public void deleteFile() {
        if (file != null) {
            if (tracker != null) {
                tracker.subBytes(writtenBytes);
            }
            try {
                closeFile();
            } catch (Exception e) {
            }
            try {
                AccessController.doPrivileged(
                        (PrivilegedExceptionAction<Void>) () -> {
                            file.delete();
                            return null;
                        }
                );
                if (PrismFontFactory.debugFonts) {
                    System.err.println("Temp file delete: " + file.getPath());
                }
            } catch (Exception e) {
            }
            file = null;
            raFile = null;
        }
    }

    public boolean isTracking() {
        return tracker != null;
    }

    private void checkTracker(int size) throws IOException {
        if (tracker != null) {
            if (size < 0 || pos > FontTracker.MAX_FILE_SIZE - size) {
                throw new IOException("File too big.");
            }
            if (tracker.getNumBytes() > FontTracker.MAX_TOTAL_BYTES - size) {
                throw new IOException("Total files too big.");
            }
        }
    }

    private void checkSize(int size) throws IOException {
        if (tracker != null) {
            checkTracker(size);
            tracker.addBytes(size);
            writtenBytes += size;
        }
    }

    private void setHeaderPos(int pos) {
        headerPos = pos;
    }

    /*
     * Write a snft header for the specified format and number of tables.
     */
    public void writeHeader(int format, short numTables) throws IOException {
        int size = TTCHEADERSIZE + (DIRECTORYENTRYSIZE * numTables);
        checkSize(size);
        header = new byte[size];

        /* Spec:
        * searchRange = (maximum power of 2 <= numTables) * 16
        * entrySelector = log2(maximum power of 2 <= numTables)
        * rangeShift = numTables*16-searchRange
        */
        short maxPower2 = numTables;
        maxPower2 |= (maxPower2 >> 1);
        maxPower2 |= (maxPower2 >> 2);
        maxPower2 |= (maxPower2 >> 4);
        maxPower2 |= (maxPower2 >> 8);
        /* at this point maxPower2+1 is the minimum power of 2 > numTables
          maxPower2 & ~(maxPower2>>1) is the maximum power of 2 <= numTables */
        maxPower2 &= ~(maxPower2 >> 1);
        short searchRange = (short)(maxPower2 * 16);
        short entrySelector = 0;
        while (maxPower2 > 1) {
            entrySelector++;
            maxPower2 >>= 1;
        }
        short rangeShift = (short)(numTables * 16 - searchRange);

        setHeaderPos(0);
        writeInt(format);
        writeShort(numTables);
        writeShort(searchRange);
        writeShort(entrySelector);
        writeShort(rangeShift);
    }

    public void writeDirectoryEntry(int index, int tag,
            int checksum, int offset, int length) throws IOException
    {
        setHeaderPos(TTCHEADERSIZE + DIRECTORYENTRYSIZE * index);
        writeInt(tag);
        writeInt(checksum);
        writeInt(offset);
        writeInt(length);
    }

    private void writeInt(int value) throws IOException {
        header[headerPos++] = (byte)((value & 0xFF000000) >> 24);
        header[headerPos++] = (byte)((value & 0x00FF0000) >> 16);
        header[headerPos++] = (byte)((value & 0x0000FF00) >> 8);
        header[headerPos++] = (byte) (value & 0x000000FF);
    }

    private void writeShort(short value) throws IOException {
        header[headerPos++] = (byte)((value & 0xFF00) >> 8);
        header[headerPos++] = (byte)(value & 0xFF);
    }

    public void writeBytes(byte[] buffer) throws IOException {
        writeBytes(buffer, 0, buffer.length);
    }

    public void writeBytes(byte[] buffer, int startPos, int length)
            throws IOException
    {
        checkSize(length);
        raFile.write(buffer, startPos, length);
        pos += length;
    }

    /**
     * Used with the byte count tracker for fonts created from streams.
     * If a thread can create temp files anyway, there is no point in counting
     * font bytes.
     */
    static boolean hasTempPermission() {
        if (System.getSecurityManager() == null) {
            return true;
        }
        File f = null;
        boolean hasPerm = false;
        try {
            f = Files.createTempFile("+JXF", ".tmp").toFile();
            f.delete();
            f = null;
            hasPerm = true;
        } catch (Throwable t) {
            /* inc. any kind of SecurityException */
        }
        return hasPerm;
    }

    /* Like JDK, FX allows untrusted code to create fonts which consume
     * disk resource. We need to place some reasonable limit on the amount
     * that can be consumed to prevent D.O.S type attacks.
     */
    static class FontTracker {
        public static final int MAX_FILE_SIZE = 32 * 1024 * 1024;
        public static final int MAX_TOTAL_BYTES = 10 * MAX_FILE_SIZE;

        static int numBytes;
        static FontTracker tracker;

        public static synchronized FontTracker getTracker() {
            if (tracker == null) {
                tracker = new FontTracker();
            }
            return tracker;
        }

        public synchronized int getNumBytes() {
            return numBytes;
        }

        public synchronized void addBytes(int sz) {
            numBytes += sz;
        }

        public synchronized void subBytes(int sz) {
            numBytes -= sz;
        }

        private static Semaphore cs = null;

        /**
         * Returns a counting semaphore.
         */
        private static synchronized Semaphore getCS() {
            if (cs == null) {
                // Make a semaphore with 5 permits that obeys the first-in first-out
                // granting of permits.
                cs = new Semaphore(5, true);
            }
            return cs;
        }

        public boolean acquirePermit() throws InterruptedException {
            // This does a timed-out wait.
            return getCS().tryAcquire(120, TimeUnit.SECONDS);
        }

        public void releasePermit() {
            getCS().release();
        }

        public void add(File file) {
            TempFileDeletionHook.add(file);
        }

        public void set(File file, RandomAccessFile raf) {
            TempFileDeletionHook.set(file, raf);
        }

        public void remove(File file) {
            TempFileDeletionHook.remove(file);
        }

        /**
         * Helper class for cleanup of temp files created while processing fonts.
         */
        private static class TempFileDeletionHook {
            private static HashMap<File, RandomAccessFile> files =
                new HashMap<File, RandomAccessFile>();

            private static Thread t = null;
            static void init() {
                if (t == null) {
                    // Add a shutdown hook to remove the temp file.
                    java.security.AccessController.doPrivileged(
                            (java.security.PrivilegedAction) () -> {
                                t = new Thread(() -> {
                                    runHooks();
                                });
                                Runtime.getRuntime().addShutdownHook(t);
                                return null;
                            }
                    );
                }
            }

            private TempFileDeletionHook() {}

            static synchronized void add(File file) {
                init();
                files.put(file, null);
            }

            static synchronized void set(File file, RandomAccessFile raf) {
                files.put(file, raf);
            }

            static synchronized void remove(File file) {
                files.remove(file);
            }

            static synchronized void runHooks() {
                if (files.isEmpty()) {
                    return;
                }

                for (Map.Entry<File, RandomAccessFile> entry : files.entrySet())
                {
                    // Close the associated raf, and then delete the file.
                    try {
                        if (entry.getValue() != null) {
                            entry.getValue().close();
                        }
                    } catch (Exception e) {}
                    entry.getKey().delete();
                }
            }
        }
    }
}