/*
 *
 * This file is part of the iText (R) project.
    Copyright (c) 1998-2020 iText Group NV
 * Authors: Bruno Lowagie, Paulo Soares, et al.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License version 3
 * as published by the Free Software Foundation with the addition of the
 * following permission added to Section 15 as permitted in Section 7(a):
 * FOR ANY PART OF THE COVERED WORK IN WHICH THE COPYRIGHT IS OWNED BY
 * ITEXT GROUP. ITEXT GROUP DISCLAIMS THE WARRANTY OF NON INFRINGEMENT
 * OF THIRD PARTY RIGHTS
 *
 * This program 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 Affero General Public License for more details.
 * You should have received a copy of the GNU Affero General Public License
 * along with this program; if not, see http://www.gnu.org/licenses or write to
 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA, 02110-1301 USA, or download the license from the following URL:
 * http://itextpdf.com/terms-of-use/
 *
 * The interactive user interfaces in modified source and object code versions
 * of this program must display Appropriate Legal Notices, as required under
 * Section 5 of the GNU Affero General Public License.
 *
 * In accordance with Section 7(b) of the GNU Affero General Public License,
 * a covered work must retain the producer line in every PDF that is created
 * or manipulated using iText.
 *
 * You can be released from the requirements of the license by purchasing
 * a commercial license. Buying such a license is mandatory as soon as you
 * develop commercial activities involving the iText software without
 * disclosing the source code of your own applications.
 * These activities include: offering paid services to customers as an ASP,
 * serving PDFs on the fly in a web application, shipping iText with a closed
 * source product.
 *
 * For more information, please contact iText Software Corp. at this
 * address: sales@itextpdf.com
 */
package com.itextpdf.text.pdf;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.HashSet;

import com.itextpdf.text.DocumentException;
import com.itextpdf.text.ExceptionConverter;
import com.itextpdf.text.error_messages.MessageLocalization;

/** Subsets a True Type font by removing the unneeded glyphs from
 * the font.
 *
 * @author  Paulo Soares
 */
class TrueTypeFontSubSet {
    static final String tableNamesSimple[] = {"cvt ", "fpgm", "glyf", "head",
        "hhea", "hmtx", "loca", "maxp", "prep"};
    static final String tableNamesCmap[] = {"cmap", "cvt ", "fpgm", "glyf", "head",
        "hhea", "hmtx", "loca", "maxp", "prep"};
    static final String tableNamesExtra[] = {"OS/2", "cmap", "cvt ", "fpgm", "glyf", "head",
        "hhea", "hmtx", "loca", "maxp", "name, prep"};
    static final int entrySelectors[] = {0,0,1,1,2,2,2,2,3,3,3,3,3,3,3,3,4,4,4,4,4};
    static final int TABLE_CHECKSUM = 0;
    static final int TABLE_OFFSET = 1;
    static final int TABLE_LENGTH = 2;
    static final int HEAD_LOCA_FORMAT_OFFSET = 51;

    static final int ARG_1_AND_2_ARE_WORDS = 1;
    static final int WE_HAVE_A_SCALE = 8;
    static final int MORE_COMPONENTS = 32;
    static final int WE_HAVE_AN_X_AND_Y_SCALE = 64;
    static final int WE_HAVE_A_TWO_BY_TWO = 128;


    /** Contains the location of the several tables. The key is the name of
     * the table and the value is an <CODE>int[3]</CODE> where position 0
     * is the checksum, position 1 is the offset from the start of the file
     * and position 2 is the length of the table.
     */
    protected HashMap<String, int[]> tableDirectory;
    /** The file in use.
     */
    protected RandomAccessFileOrArray rf;
    /** The file name.
     */
    protected String fileName;
    protected boolean includeCmap;
    protected boolean includeExtras;
    protected boolean locaShortTable;
    protected int locaTable[];
    protected HashSet<Integer> glyphsUsed;
    protected ArrayList<Integer> glyphsInList;
    protected int tableGlyphOffset;
    protected int newLocaTable[];
    protected byte newLocaTableOut[];
    protected byte newGlyfTable[];
    protected int glyfTableRealSize;
    protected int locaTableRealSize;
    protected byte outFont[];
    protected int fontPtr;
    protected int directoryOffset;

    /** Creates a new TrueTypeFontSubSet
     * @param directoryOffset The offset from the start of the file to the table directory
     * @param fileName the file name of the font
     * @param glyphsUsed the glyphs used
     * @param includeCmap <CODE>true</CODE> if the table cmap is to be included in the generated font
     */
    TrueTypeFontSubSet(String fileName, RandomAccessFileOrArray rf, HashSet<Integer> glyphsUsed, int directoryOffset, boolean includeCmap, boolean includeExtras) {
        this.fileName = fileName;
        this.rf = rf;
        this.glyphsUsed = glyphsUsed;
        this.includeCmap = includeCmap;
        this.includeExtras = includeExtras;
        this.directoryOffset = directoryOffset;
        glyphsInList = new ArrayList<Integer>(glyphsUsed);
    }

    /** Does the actual work of subsetting the font.
     * @throws IOException on error
     * @throws DocumentException on error
     * @return the subset font
     */
    byte[] process() throws IOException, DocumentException {
        try {
            rf.reOpen();
            createTableDirectory();
            readLoca();
            flatGlyphs();
            createNewGlyphTables();
            locaTobytes();
            assembleFont();
            return outFont;
        }
        finally {
            try {
                rf.close();
            }
            catch (Exception e) {
                // empty on purpose
            }
        }
    }

    protected void assembleFont() throws IOException {
        int tableLocation[];
        int fullFontSize = 0;
        String tableNames[];
        if (includeExtras)
            tableNames = tableNamesExtra;
        else {
            if (includeCmap)
                tableNames = tableNamesCmap;
            else
                tableNames = tableNamesSimple;
        }
        int tablesUsed = 2;
        int len = 0;
        for (int k = 0; k < tableNames.length; ++k) {
            String name = tableNames[k];
            if (name.equals("glyf") || name.equals("loca"))
                continue;
            tableLocation = tableDirectory.get(name);
            if (tableLocation == null)
                continue;
            ++tablesUsed;
            fullFontSize += tableLocation[TABLE_LENGTH] + 3 & ~3;
        }
        fullFontSize += newLocaTableOut.length;
        fullFontSize += newGlyfTable.length;
        int ref = 16 * tablesUsed + 12;
        fullFontSize += ref;
        outFont = new byte[fullFontSize];
        fontPtr = 0;
        writeFontInt(0x00010000);
        writeFontShort(tablesUsed);
        int selector = entrySelectors[tablesUsed];
        writeFontShort((1 << selector) * 16);
        writeFontShort(selector);
        writeFontShort((tablesUsed - (1 << selector)) * 16);
        for (int k = 0; k < tableNames.length; ++k) {
            String name = tableNames[k];
            tableLocation = tableDirectory.get(name);
            if (tableLocation == null)
                continue;
            writeFontString(name);
            if (name.equals("glyf")) {
                writeFontInt(calculateChecksum(newGlyfTable));
                len = glyfTableRealSize;
            }
            else if (name.equals("loca")) {
                writeFontInt(calculateChecksum(newLocaTableOut));
                len = locaTableRealSize;
            }
            else {
                writeFontInt(tableLocation[TABLE_CHECKSUM]);
                len = tableLocation[TABLE_LENGTH];
            }
            writeFontInt(ref);
            writeFontInt(len);
            ref += len + 3 & ~3;
        }
        for (int k = 0; k < tableNames.length; ++k) {
            String name = tableNames[k];
            tableLocation = tableDirectory.get(name);
            if (tableLocation == null)
                continue;
            if (name.equals("glyf")) {
                System.arraycopy(newGlyfTable, 0, outFont, fontPtr, newGlyfTable.length);
                fontPtr += newGlyfTable.length;
                newGlyfTable = null;
            }
            else if (name.equals("loca")) {
                System.arraycopy(newLocaTableOut, 0, outFont, fontPtr, newLocaTableOut.length);
                fontPtr += newLocaTableOut.length;
                newLocaTableOut = null;
            }
            else {
                rf.seek(tableLocation[TABLE_OFFSET]);
                rf.readFully(outFont, fontPtr, tableLocation[TABLE_LENGTH]);
                fontPtr += tableLocation[TABLE_LENGTH] + 3 & ~3;
            }
        }
    }

    protected void createTableDirectory() throws IOException, DocumentException {
        tableDirectory = new HashMap<String, int[]>();
        rf.seek(directoryOffset);
        int id = rf.readInt();
        if (id != 0x00010000)
            throw new DocumentException(MessageLocalization.getComposedMessage("1.is.not.a.true.type.file", fileName));
        int num_tables = rf.readUnsignedShort();
        rf.skipBytes(6);
        for (int k = 0; k < num_tables; ++k) {
            String tag = readStandardString(4);
            int tableLocation[] = new int[3];
            tableLocation[TABLE_CHECKSUM] = rf.readInt();
            tableLocation[TABLE_OFFSET] = rf.readInt();
            tableLocation[TABLE_LENGTH] = rf.readInt();
            tableDirectory.put(tag, tableLocation);
        }
    }

    protected void readLoca() throws IOException, DocumentException {
        int tableLocation[];
        tableLocation = tableDirectory.get("head");
        if (tableLocation == null)
            throw new DocumentException(MessageLocalization.getComposedMessage("table.1.does.not.exist.in.2", "head", fileName));
        rf.seek(tableLocation[TABLE_OFFSET] + HEAD_LOCA_FORMAT_OFFSET);
        locaShortTable = rf.readUnsignedShort() == 0;
        tableLocation = tableDirectory.get("loca");
        if (tableLocation == null)
            throw new DocumentException(MessageLocalization.getComposedMessage("table.1.does.not.exist.in.2", "loca", fileName));
        rf.seek(tableLocation[TABLE_OFFSET]);
        if (locaShortTable) {
            int entries = tableLocation[TABLE_LENGTH] / 2;
            locaTable = new int[entries];
            for (int k = 0; k < entries; ++k)
                locaTable[k] = rf.readUnsignedShort() * 2;
        }
        else {
            int entries = tableLocation[TABLE_LENGTH] / 4;
            locaTable = new int[entries];
            for (int k = 0; k < entries; ++k)
                locaTable[k] = rf.readInt();
        }
    }

    protected void createNewGlyphTables() throws IOException {
        newLocaTable = new int[locaTable.length];
        int activeGlyphs[] = new int[glyphsInList.size()];
        for (int k = 0; k < activeGlyphs.length; ++k)
            activeGlyphs[k] = glyphsInList.get(k).intValue();
        Arrays.sort(activeGlyphs);
        int glyfSize = 0;
        for (int k = 0; k < activeGlyphs.length; ++k) {
            int glyph = activeGlyphs[k];
            glyfSize += locaTable[glyph + 1] - locaTable[glyph];
        }
        glyfTableRealSize = glyfSize;
        glyfSize = glyfSize + 3 & ~3;
        newGlyfTable = new byte[glyfSize];
        int glyfPtr = 0;
        int listGlyf = 0;
        for (int k = 0; k < newLocaTable.length; ++k) {
            newLocaTable[k] = glyfPtr;
            if (listGlyf < activeGlyphs.length && activeGlyphs[listGlyf] == k) {
                ++listGlyf;
                newLocaTable[k] = glyfPtr;
                int start = locaTable[k];
                int len = locaTable[k + 1] - start;
                if (len > 0) {
                    rf.seek(tableGlyphOffset + start);
                    rf.readFully(newGlyfTable, glyfPtr, len);
                    glyfPtr += len;
                }
            }
        }
    }

    protected void locaTobytes() {
        if (locaShortTable)
            locaTableRealSize = newLocaTable.length * 2;
        else
            locaTableRealSize = newLocaTable.length * 4;
        newLocaTableOut = new byte[locaTableRealSize + 3 & ~3];
        outFont = newLocaTableOut;
        fontPtr = 0;
        for (int k = 0; k < newLocaTable.length; ++k) {
            if (locaShortTable)
                writeFontShort(newLocaTable[k] / 2);
            else
                writeFontInt(newLocaTable[k]);
        }

    }

    protected void flatGlyphs() throws IOException, DocumentException {
        int tableLocation[];
        tableLocation = tableDirectory.get("glyf");
        if (tableLocation == null)
            throw new DocumentException(MessageLocalization.getComposedMessage("table.1.does.not.exist.in.2", "glyf", fileName));
        Integer glyph0 = Integer.valueOf(0);
        if (!glyphsUsed.contains(glyph0)) {
            glyphsUsed.add(glyph0);
            glyphsInList.add(glyph0);
        }
        tableGlyphOffset = tableLocation[TABLE_OFFSET];
        for (int k = 0; k < glyphsInList.size(); ++k) {
            int glyph = glyphsInList.get(k).intValue();
            checkGlyphComposite(glyph);
        }
    }

    protected void checkGlyphComposite(int glyph) throws IOException {
        int start = locaTable[glyph];
        if (start == locaTable[glyph + 1]) // no contour
            return;
        rf.seek(tableGlyphOffset + start);
        int numContours = rf.readShort();
        if (numContours >= 0)
            return;
        rf.skipBytes(8);
        for(;;) {
            int flags = rf.readUnsignedShort();
            Integer cGlyph = Integer.valueOf(rf.readUnsignedShort());
            if (!glyphsUsed.contains(cGlyph)) {
                glyphsUsed.add(cGlyph);
                glyphsInList.add(cGlyph);
            }
            if ((flags & MORE_COMPONENTS) == 0)
                return;
            int skip;
            if ((flags & ARG_1_AND_2_ARE_WORDS) != 0)
                skip = 4;
            else
                skip = 2;
            if ((flags & WE_HAVE_A_SCALE) != 0)
                skip += 2;
            else if ((flags & WE_HAVE_AN_X_AND_Y_SCALE) != 0)
                skip += 4;
            if ((flags & WE_HAVE_A_TWO_BY_TWO) != 0)
                skip += 8;
            rf.skipBytes(skip);
        }
    }

    /** Reads a <CODE>String</CODE> from the font file as bytes using the Cp1252
     *  encoding.
     * @param length the length of bytes to read
     * @return the <CODE>String</CODE> read
     * @throws IOException the font file could not be read
     */
    protected String readStandardString(int length) throws IOException {
        byte buf[] = new byte[length];
        rf.readFully(buf);
        try {
            return new String(buf, BaseFont.WINANSI);
        }
        catch (Exception e) {
            throw new ExceptionConverter(e);
        }
    }

    protected void writeFontShort(int n) {
        outFont[fontPtr++] = (byte)(n >> 8);
        outFont[fontPtr++] = (byte)n;
    }

    protected void writeFontInt(int n) {
        outFont[fontPtr++] = (byte)(n >> 24);
        outFont[fontPtr++] = (byte)(n >> 16);
        outFont[fontPtr++] = (byte)(n >> 8);
        outFont[fontPtr++] = (byte)n;
    }

    protected void writeFontString(String s) {
        byte b[] = PdfEncodings.convertToBytes(s, BaseFont.WINANSI);
        System.arraycopy(b, 0, outFont, fontPtr, b.length);
        fontPtr += b.length;
    }

    protected int calculateChecksum(byte b[]) {
        int len = b.length / 4;
        int v0 = 0;
        int v1 = 0;
        int v2 = 0;
        int v3 = 0;
        int ptr = 0;
        for (int k = 0; k < len; ++k) {
            v3 += b[ptr++] & 0xff;
            v2 += b[ptr++] & 0xff;
            v1 += b[ptr++] & 0xff;
            v0 += b[ptr++] & 0xff;
        }
        return v0 + (v1 << 8) + (v2 << 16) + (v3 << 24);
    }
}
