/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.fontbox.cmap;

import java.io.IOException;
import java.io.InputStream;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.apache.pdfbox.io.RandomAccessRead;
import org.apache.pdfbox.io.RandomAccessReadBuffer;

/**
 * Parses a CMap stream.
 *
 * @author Ben Litchfield
 */
public class CMapParser
{
    private static final String MARK_END_OF_DICTIONARY = ">>";
    private static final String MARK_END_OF_ARRAY = "]";

    private final byte[] tokenParserByteBuffer = new byte[512];

    private boolean strictMode = false;

    /**
     * Creates a new instance of CMapParser.
     */
    public CMapParser()
    {
    }

    /**
     * Creates a new instance of CMapParser.
     * 
     * @param strictMode activates the strict mode used for inline CMaps
     */
    public CMapParser(boolean strictMode)
    {
        this.strictMode = strictMode;
    }

    /**
     * Parses a predefined CMap.
     *
     * @param name CMap name.
     * @return The parsed predefined CMap as a java object, never null.
     * @throws IOException If the CMap could not be parsed.
     */
    public CMap parsePredefined(String name) throws IOException
    {
        try (RandomAccessRead randomAccessRead = getExternalCMap(name))
        {
            // deactivate strict mode
            strictMode = false;
            return parse(randomAccessRead);
        }
    }

    /**
     * This will parse the stream and create a cmap object.
     *
     * @param randomAccessRead the source of the CMap to be parsed.
     * @return The parsed source as a java object, never null.
     * @throws IOException If there is an error parsing the data.
     */
    public CMap parse(RandomAccessRead randomAccessRead) throws IOException
    {
        CMap result = new CMap();
        Object previousToken = null;
        Object token = parseNextToken(randomAccessRead);
        while (token != null)
        {
            if (token instanceof Operator)
            {
                Operator op = (Operator) token;
                if (op.op.equals("endcmap"))
                {
                    // end of CMap reached, stop reading as there isn't any interesting info anymore
                    break;
                }

                if (op.op.equals("usecmap") && previousToken instanceof LiteralName)
                {
                    parseUsecmap((LiteralName) previousToken, result);
                }
                else if (previousToken instanceof Number)
                {
                    if (op.op.equals("begincodespacerange"))
                    {
                        parseBegincodespacerange((Number) previousToken, randomAccessRead, result);
                    }
                    else if (op.op.equals("beginbfchar"))
                    {
                        parseBeginbfchar((Number) previousToken, randomAccessRead, result);
                    }
                    else if (op.op.equals("beginbfrange"))
                    {
                        parseBeginbfrange((Number) previousToken, randomAccessRead, result);
                    }
                    else if (op.op.equals("begincidchar"))
                    {
                        parseBegincidchar((Number) previousToken, randomAccessRead, result);
                    }
                    else if (op.op.equals("begincidrange") && previousToken instanceof Integer)
                    {
                        parseBegincidrange((Integer) previousToken, randomAccessRead, result);
                    }
                }
            }
            else if (token instanceof LiteralName)
            {
                parseLiteralName((LiteralName) token, randomAccessRead, result);
            }
            previousToken = token;
            token = parseNextToken(randomAccessRead);
        }
        return result;
    }

    private void parseUsecmap(LiteralName useCmapName, CMap result) throws IOException
    {
        try (RandomAccessRead randomAccessRead = getExternalCMap(useCmapName.name))
        {
            CMap useCMap = parse(randomAccessRead);
            result.useCmap(useCMap);
        }
    }

    private void parseLiteralName(LiteralName literal, RandomAccessRead randomAccessRead,
            CMap result) throws IOException
    {
        switch (literal.name)
        {
            case "WMode":
            {
                Object next = parseNextToken(randomAccessRead);
                if (next instanceof Integer)
                {
                    result.setWMode((Integer) next);
                }
                break;
            }
            case "CMapName":
            {
                Object next = parseNextToken(randomAccessRead);
                if (next instanceof LiteralName)
                {
                    result.setName(((LiteralName) next).name);
                }
                break;
            }
            case "CMapVersion":
            {
                Object next = parseNextToken(randomAccessRead);
                if (next instanceof Number)
                {
                    result.setVersion(next.toString());
                }
                else if (next instanceof String)
                {
                    result.setVersion((String) next);
                }
                break;
            }
            case "CMapType":
            {
                Object next = parseNextToken(randomAccessRead);
                if (next instanceof Integer)
                {
                    result.setType((Integer) next);
                }
                break;
            }
            case "Registry":
            {
                Object next = parseNextToken(randomAccessRead);
                if (next instanceof String)
                {
                    result.setRegistry((String) next);
                }
                break;
            }
            case "Ordering":
            {
                Object next = parseNextToken(randomAccessRead);
                if (next instanceof String)
                {
                    result.setOrdering((String) next);
                }
                break;
            }
            case "Supplement":
            {
                Object next = parseNextToken(randomAccessRead);
                if (next instanceof Integer)
                {
                    result.setSupplement((Integer) next);
                }
                break;
            }
            default:
                break;
        }
    }

    /**
     * Throws an IOException if expectedOperatorName not equals operator.op
     *
     * @param operator Instance of operator
     * @param expectedOperatorName Expected name of operator
     * @param rangeName The name of the range in which the operator is expected (without a tilde
     * character), to be used in the exception message.
     * 
     * @throws IOException if expectedOperatorName not equals operator.op
     */
    private void checkExpectedOperator(Operator operator, String expectedOperatorName, String rangeName) throws IOException
    {
        if (!operator.op.equals(expectedOperatorName))
        {
            throw new IOException("Error : ~" + rangeName + " contains an unexpected operator : "
                    + operator.op);
        }
    }

    private void parseBegincodespacerange(Number cosCount, RandomAccessRead randomAccessRead,
            CMap result) throws IOException
    {
        for (int j = 0; j < cosCount.intValue(); j++)
        {
            Object nextToken = parseNextToken(randomAccessRead);
            if (nextToken instanceof Operator)
            {
                checkExpectedOperator((Operator) nextToken, "endcodespacerange", "codespacerange");
                break;
            }
            if (!(nextToken instanceof byte[]))
            {
                throw new IOException("start range missing");
            }
            byte[] startRange = (byte[]) nextToken;
            byte[] endRange = parseByteArray(randomAccessRead);
            try
            {
                result.addCodespaceRange(new CodespaceRange(startRange, endRange));
            }
            catch (IllegalArgumentException ex)
            {
                throw new IOException(ex);
            }
        }
    }

    private void parseBeginbfchar(Number cosCount, RandomAccessRead randomAccessRead,
            CMap result) throws IOException
    {
        for (int j = 0; j < cosCount.intValue(); j++)
        {
            Object nextToken = parseNextToken(randomAccessRead);
            if (nextToken instanceof Operator)
            {
                checkExpectedOperator((Operator) nextToken, "endbfchar", "bfchar");
                break;
            }
            if (!(nextToken instanceof byte[]))
            {
                throw new IOException("input code missing");
            }
            byte[] inputCode = (byte[]) nextToken;
            nextToken = parseNextToken(randomAccessRead);
            if (nextToken instanceof byte[])
            {
                byte[] bytes = (byte[]) nextToken;
                String value = createStringFromBytes(bytes);
                result.addCharMapping(inputCode, value);
            }
            else if (nextToken instanceof LiteralName)
            {
                result.addCharMapping(inputCode, ((LiteralName) nextToken).name);
            }
            else
            {
                throw new IOException("Error parsing CMap beginbfchar, expected{COSString "
                        + "or COSName} and not " + nextToken);
            }
        }
    }

    private void parseBegincidrange(int numberOfLines, RandomAccessRead randomAccessRead,
            CMap result) throws IOException
    {
        for (int n = 0; n < numberOfLines; n++)
        {
            Object nextToken = parseNextToken(randomAccessRead);
            if (nextToken instanceof Operator)
            {
                checkExpectedOperator((Operator) nextToken, "endcidrange", "cidrange");
                break;
            }
            if (!(nextToken instanceof byte[]))
            {
                throw new IOException("start code missing");
            }
            byte[] startCode = (byte[]) nextToken;
            byte[] endCode = parseByteArray(randomAccessRead);
            int mappedCode = parseInteger(randomAccessRead);
            if (startCode.length == endCode.length)
            {
                // some CMaps are using CID ranges to map single values
                if (Arrays.equals(startCode, endCode))
                {
                    result.addCIDMapping(startCode, mappedCode);
                }
                else
                {
                    result.addCIDRange(startCode, endCode, mappedCode);
                }
            }
            else
            {
                throw new IOException(
                        "Error : ~cidrange values must not have different byte lengths");
            }
        }
    }

    private void parseBegincidchar(Number cosCount, RandomAccessRead randomAccessRead,
            CMap result) throws IOException
    {
        for (int j = 0; j < cosCount.intValue(); j++)
        {
            Object nextToken = parseNextToken(randomAccessRead);
            if (nextToken instanceof Operator)
            {
                checkExpectedOperator((Operator) nextToken, "endcidchar", "cidchar");
                break;
            }
            if (!(nextToken instanceof byte[]))
            {
                throw new IOException("input code missing");
            }
            byte[] inputCode = (byte[]) nextToken;
            int mappedCID = parseInteger(randomAccessRead);
            result.addCIDMapping(inputCode, mappedCID);
        }
    }

    private void parseBeginbfrange(Number cosCount, RandomAccessRead randomAccessRead,
            CMap result) throws IOException
    {
        for (int j = 0; j < cosCount.intValue(); j++)
        {
            Object nextToken = parseNextToken(randomAccessRead);
            if (nextToken instanceof Operator)
            {
                checkExpectedOperator((Operator) nextToken, "endbfrange", "bfrange");
                break;
            }
            if (!(nextToken instanceof byte[]))
            {
                throw new IOException("start code missing");
            }
            byte[] startCode = (byte[]) nextToken;
            nextToken = parseNextToken(randomAccessRead);
            if (nextToken instanceof Operator)
            {
                checkExpectedOperator((Operator) nextToken, "endbfrange", "bfrange");
                break;
            }
            if (!(nextToken instanceof byte[]))
            {
                throw new IOException("end code missing");
            }
            byte[] endCode = (byte[]) nextToken;
            int start = CMap.toInt(startCode);
            int end = CMap.toInt(endCode);
            // end has to be bigger than start or equal
            if (end < start)
            {
                // PDFBOX-4550: likely corrupt stream
                break;
            }
            nextToken = parseNextToken(randomAccessRead);
            if (nextToken instanceof List<?>)
            {
                List<byte[]> array = (List<byte[]>) nextToken;
                // ignore empty and malformed arrays
                if (!array.isEmpty() && array.size() >= end - start)
                {
                    addMappingFrombfrange(result, startCode, array);
                }
            }
            // PDFBOX-3807: ignore null
            else if (nextToken instanceof byte[])
            {
                byte[] tokenBytes = (byte[]) nextToken;
                // PDFBOX-3450: ignore <>
                if (tokenBytes.length > 0)
                {
                    // PDFBOX-4720:
                    // some pdfs use the malformed bfrange <0000> <FFFF> <0000>. Add support by adding a identity
                    // mapping for the whole range instead of cutting it after 255 entries
                    // TODO find a more efficient method to represent all values for a identity mapping
                    if (tokenBytes.length == 2 && start == 0 && end == 0xffff
                            && tokenBytes[0] == 0 && tokenBytes[1] == 0)
                    {
                        for (int i = 0; i < 256; i++)
                        {
                            startCode[0] = (byte) i;
                            startCode[1] = 0;
                            tokenBytes[0] = (byte) i;
                            tokenBytes[1] = 0;
                            addMappingFrombfrange(result, startCode, 256, tokenBytes);
                        }
                    }
                    else
                    {
                        addMappingFrombfrange(result, startCode, end - start + 1, tokenBytes);
                    }
                }
            }
        }
    }

    private void addMappingFrombfrange(CMap cmap, byte[] startCode, List<byte[]> tokenBytesList)
    {
        for (byte[] tokenBytes : tokenBytesList)
        {
            String value = createStringFromBytes(tokenBytes);
            cmap.addCharMapping(startCode, value);
            increment(startCode, startCode.length - 1, false);
        }
    }

    private void addMappingFrombfrange(CMap cmap, byte[] startCode, int values,
            byte[] tokenBytes)
    {
        for (int i = 0; i < values; i++)
        {
            String value = createStringFromBytes(tokenBytes);
            cmap.addCharMapping(startCode, value);
            if (!increment(tokenBytes, tokenBytes.length - 1, strictMode))
            {
                // overflow detected -> stop adding further mappings
                break;
            }
            increment(startCode, startCode.length - 1, false);
        }
    }

    /**
     * Returns a RandomAccessRead containing the given "use" CMap.
     *
     * @param name Name of the given "use" CMap resource.
     * @throws IOException if the CMap resource doesn't exist or if there is an error opening it.
     */
    private RandomAccessRead getExternalCMap(String name) throws IOException
    {
        InputStream is = getClass().getResourceAsStream(name);
        if (is == null)
        {
            throw new IOException("Error: Could not find referenced cmap stream " + name);
        }
        return RandomAccessReadBuffer.createBufferFromStream(is);
    }

    private Object parseNextToken(RandomAccessRead randomAccessRead) throws IOException
    {
        int nextByte = randomAccessRead.read();
        // skip whitespace
        while (nextByte == 0x09 || nextByte == 0x20 || nextByte == 0x0D || nextByte == 0x0A)
        {
            nextByte = randomAccessRead.read();
        }
        switch (nextByte)
        {
        case '%':
            return readLine(randomAccessRead, nextByte);
        case '(':
            return readString(randomAccessRead);
        case '>':
            if (randomAccessRead.read() == '>')
            {
                return MARK_END_OF_DICTIONARY;
            }
            else
            {
                throw new IOException("Error: expected the end of a dictionary.");
            }
        case ']':
            return MARK_END_OF_ARRAY;
        case '[':
            return readArray(randomAccessRead);
        case '<':
            return readDictionary(randomAccessRead);
        case '/':
            return readLiteralName(randomAccessRead);
        case -1:
        {
            // EOF returning null
            break;
        }
        case '0':
        case '1':
        case '2':
        case '3':
        case '4':
        case '5':
        case '6':
        case '7':
        case '8':
        case '9':
            return readNumber(randomAccessRead, nextByte);
        default:
            return readOperator(randomAccessRead, nextByte);
        }
        return null;
    }

    private Integer parseInteger(RandomAccessRead randomAccessRead) throws IOException
    {
        Object nextToken = parseNextToken(randomAccessRead);
        if (nextToken == null)
        {
            throw new IOException("expected integer value is missing");
        }
        if (nextToken instanceof Integer)
        {
            return (Integer) nextToken;
        }
        throw new IOException("invalid type for next token");
    }

    private byte[] parseByteArray(RandomAccessRead randomAccessRead) throws IOException
    {
        Object nextToken = parseNextToken(randomAccessRead);
        if (nextToken == null)
        {
            throw new IOException("expected byte[] value is missing");
        }
        if (nextToken instanceof byte[])
        {
            return (byte[]) nextToken;
        }
        throw new IOException("invalid type for next token");
    }

    private List<Object> readArray(RandomAccessRead randomAccessRead) throws IOException
    {
        List<Object> list = new ArrayList<>();
        Object nextToken = parseNextToken(randomAccessRead);
        while (nextToken != null && !MARK_END_OF_ARRAY.equals(nextToken))
        {
            list.add(nextToken);
            nextToken = parseNextToken(randomAccessRead);
        }
        return list;
    }

    private String readString(RandomAccessRead randomAccessRead) throws IOException
    {
        StringBuilder buffer = new StringBuilder();
        int stringByte = randomAccessRead.read();
        while (stringByte != -1 && stringByte != ')')
        {
            buffer.append((char) stringByte);
            stringByte = randomAccessRead.read();
        }
        return buffer.toString();
    }

    private String readLine(RandomAccessRead randomAccessRead, int firstByte) throws IOException
    {
        // header operations, for now return the entire line
        // may need to smarter in the future
        int nextByte = firstByte;
        StringBuilder buffer = new StringBuilder();
        buffer.append((char) nextByte);
        readUntilEndOfLine(randomAccessRead, buffer);
        return buffer.toString();
    }

    private LiteralName readLiteralName(RandomAccessRead randomAccessRead) throws IOException
    {
        StringBuilder buffer = new StringBuilder();
        int stringByte = randomAccessRead.read();

        while (!isWhitespaceOrEOF(stringByte) && !isDelimiter(stringByte))
        {
            buffer.append((char) stringByte);
            stringByte = randomAccessRead.read();
        }
        if (isDelimiter(stringByte))
        {
            randomAccessRead.rewind(1);
        }
        return new LiteralName(buffer.toString());
    }

    private Operator readOperator(RandomAccessRead randomAccessRead, int firstByte)
            throws IOException
    {
        int nextByte = firstByte;
        StringBuilder buffer = new StringBuilder();
        buffer.append((char) nextByte);
        nextByte = randomAccessRead.read();

        // newline separator may be missing in malformed CMap files
        // see PDFBOX-2035
        while (!isWhitespaceOrEOF(nextByte) && !isDelimiter(nextByte)
                && !Character.isDigit(nextByte))
        {
            buffer.append((char) nextByte);
            nextByte = randomAccessRead.read();
        }
        if (isDelimiter(nextByte) || Character.isDigit(nextByte))
        {
            randomAccessRead.rewind(1);
        }
        return new Operator(buffer.toString());
    }
    
    private Number readNumber(RandomAccessRead randomAccessRead, int firstByte) throws IOException
    {
        int nextByte = firstByte;
        StringBuilder buffer = new StringBuilder();
        buffer.append((char) nextByte);
        nextByte = randomAccessRead.read();

        while (!isWhitespaceOrEOF(nextByte)
                && (Character.isDigit((char) nextByte) || nextByte == '.'))
        {
            buffer.append((char) nextByte);
            nextByte = randomAccessRead.read();
        }
        if (nextByte != -1)
        {
            randomAccessRead.rewind(1);
        }
        String value = buffer.toString();
        try
        {
            if (value.indexOf('.') >= 0)
            {
                return Double.valueOf(value);
            }
            else
            {
                return Integer.valueOf(value);
            }
        }
        catch (NumberFormatException ex)
        {
            throw new IOException("Invalid number '" + value + "'", ex);
        }
    }

    private Object readDictionary(RandomAccessRead randomAccessRead) throws IOException
    {
        int theNextByte = randomAccessRead.read();
        if (theNextByte == '<')
        {
            Map<String, Object> result = new HashMap<>();
            // we are reading a dictionary
            Object key = parseNextToken(randomAccessRead);
            while (key instanceof LiteralName &&
                    !MARK_END_OF_DICTIONARY.equals(((LiteralName) key).name))
            {
                Object value = parseNextToken(randomAccessRead);
                result.put(((LiteralName) key).name, value);
                key = parseNextToken(randomAccessRead);
            }
            return result;
        }
        else
        {
            // won't read more than 512 bytes
            int multiplyer = 16;
            int bufferIndex = -1;
            while (theNextByte != -1 && theNextByte != '>')
            {
                // all kind of whitespaces may occur in malformed CMap files
                // see PDFBOX-2035
                if (isWhitespaceOrEOF(theNextByte))
                {
                    // skipping whitespaces
                    theNextByte = randomAccessRead.read();
                    continue;
                }
                int intValue = 0;
                if (theNextByte >= '0' && theNextByte <= '9')
                {
                    intValue = theNextByte - '0';
                }
                else if (theNextByte >= 'A' && theNextByte <= 'F')
                {
                    intValue = 10 + theNextByte - 'A';
                }
                else if (theNextByte >= 'a' && theNextByte <= 'f')
                {
                    intValue = 10 + theNextByte - 'a';
                }
                else
                {
                    throw new IOException("Error: expected hex character and not "
                            + (char) theNextByte + ":" + theNextByte);
                }
                intValue *= multiplyer;
                if (multiplyer == 16)
                {
                    bufferIndex++;
                    if (bufferIndex >= tokenParserByteBuffer.length)
                    {
                        throw new IOException("cmap token ist larger than buffer size "
                                + tokenParserByteBuffer.length);
                    }
                    tokenParserByteBuffer[bufferIndex] = 0;
                    multiplyer = 1;
                }
                else
                {
                    multiplyer = 16;
                }
                tokenParserByteBuffer[bufferIndex] += intValue;
                theNextByte = randomAccessRead.read();
            }
            byte[] finalResult = new byte[bufferIndex + 1];
            System.arraycopy(tokenParserByteBuffer, 0, finalResult, 0, bufferIndex + 1);
            return finalResult;
        }
    }

    private void readUntilEndOfLine(RandomAccessRead randomAccessRead, StringBuilder buf)
            throws IOException
    {
        int nextByte = randomAccessRead.read();
        while (nextByte != -1 && nextByte != 0x0D && nextByte != 0x0A)
        {
            buf.append((char) nextByte);
            nextByte = randomAccessRead.read();
        }
    }

    private static boolean isWhitespaceOrEOF(int aByte)
    {
        switch (aByte)
        {
        case -1:
        case 0x20:
        case 0x0D:
        case 0x0A:
            return true;
        default:
            return false;
        }
    }

    /** Is this a standard PDF delimiter character? */
    private static boolean isDelimiter(int aByte)
    {
        switch (aByte) 
        {
            case '(':
            case ')':
            case '<':
            case '>':
            case '[':
            case ']':
            case '{':
            case '}':
            case '/':
            case '%':
                return true;
            default:
                return false;
        }
    }

    private static boolean increment(byte[] data, int position, boolean useStrictMode)
    {
        if (position > 0 && (data[position] & 0xFF) == 255)
        {
            // PDFBOX-4661: avoid overflow of the last byte, all following values are undefined
            // PDFBOX-5090: strict mode has to be used for CMaps within pdfs
            if (useStrictMode)
            {
                return false;
            }
            data[position] = 0;
            increment(data, position - 1, useStrictMode);
        }
        else
        {
            data[position] = (byte) (data[position] + 1);
        }
        return true;
    }

    private static String createStringFromBytes(byte[] bytes)
    {
        if (bytes.length <= 2)
        {
            return CMapStrings.getMapping(bytes);
        }
        return new String(bytes, StandardCharsets.UTF_16BE);
    }

    /**
     * Internal class.
     */
    private static final class LiteralName
    {
        private final String name;

        private LiteralName(String theName)
        {
            name = theName;
        }
    }

    /**
     * Internal class.
     */
    private static final class Operator
    {
        private final String op;

        private Operator(String theOp)
        {
            op = theOp;
        }
    }
}
