/*
 *  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.codehaus.groovy.runtime;

import groovy.lang.StringWriterIOException;
import groovy.lang.Writable;
import org.apache.groovy.io.StringBuilderWriter;
import org.codehaus.groovy.runtime.typehandling.DefaultTypeTransformation;

import java.io.IOException;
import java.io.Writer;
import java.nio.ByteBuffer;
import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

import static org.codehaus.groovy.runtime.EncodingGroovyMethodsSupport.TRANSLATE_TABLE;
import static org.codehaus.groovy.runtime.EncodingGroovyMethodsSupport.TRANSLATE_TABLE_URLSAFE;

/**
 * This class defines all the encoding/decoding groovy methods which enhance
 * the normal JDK classes when inside the Groovy environment.
 * Static methods are used with the first parameter the destination class.
 */
public class EncodingGroovyMethods {

    private static final char[] T_TABLE = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=".toCharArray();
    private static final char[] T_TABLE_URLSAFE = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_=".toCharArray();
    private static final String CHUNK_SEPARATOR = "\r\n";
    private static final String MD5 = "MD5";
    private static final String SHA_256 = "SHA-256";

    /**
     * Produce a Writable object which writes the Base64 encoding of the byte array.
     * Calling toString() on the result returns the encoding as a String. For more
     * information on Base64 encoding and chunking see <code>RFC 4648</code>.
     *
     * @param data Byte array to be encoded
     * @param chunked whether or not the Base64 encoded data should be MIME chunked
     * @return object which will write the Base64 encoding of the byte array
     * @since 1.5.1
     */
    public static Writable encodeBase64(Byte[] data, final boolean chunked) {
        return encodeBase64(DefaultTypeTransformation.convertToByteArray(data), chunked);
    }

    /**
     * Produce a Writable object which writes the Base64 encoding of the byte array.
     * Calling toString() on the result returns the encoding as a String. For more
     * information on Base64 encoding and chunking see <code>RFC 4648</code>.
     *
     * @param data Byte array to be encoded
     * @return object which will write the Base64 encoding of the byte array
     * @since 1.0
     */
    public static Writable encodeBase64(Byte[] data) {
        return encodeBase64(DefaultTypeTransformation.convertToByteArray(data), false);
    }

    /**
     * Produce a Writable object which writes the Base64 encoding of the byte array.
     * Calling toString() on the result returns the encoding as a String. For more
     * information on Base64 encoding and chunking see <code>RFC 4648</code>.
     *
     * @param data byte array to be encoded
     * @param chunked whether or not the Base64 encoded data should be MIME chunked
     * @return object which will write the Base64 encoding of the byte array
     * @since 1.5.7
     */
    public static Writable encodeBase64(final byte[] data, final boolean chunked) {
        return encodeBase64(data, chunked, false, true);
    }

    private static Writable encodeBase64(final byte[] data, final boolean chunked, final boolean urlSafe, final boolean pad) {
        return new Writable() {
            @Override
            public Writer writeTo(final Writer writer) throws IOException {
                int charCount = 0;
                final int dLimit = (data.length / 3) * 3;
                final char[] table = urlSafe ? T_TABLE_URLSAFE : T_TABLE;
                for (int dIndex = 0; dIndex != dLimit; dIndex += 3) {
                    int d = ((data[dIndex] & 0XFF) << 16) | ((data[dIndex + 1] & 0XFF) << 8) | (data[dIndex + 2] & 0XFF);

                    writer.write(table[d >> 18]);
                    writer.write(table[(d >> 12) & 0X3F]);
                    writer.write(table[(d >> 6) & 0X3F]);
                    writer.write(table[d & 0X3F]);

                    if (chunked && ++charCount == 19) {
                        writer.write(CHUNK_SEPARATOR);
                        charCount = 0;
                    }
                }

                if (dLimit != data.length) {
                    int d = (data[dLimit] & 0XFF) << 16;

                    if (dLimit + 1 != data.length) {
                        d |= (data[dLimit + 1] & 0XFF) << 8;
                    }

                    writer.write(table[d >> 18]);
                    writer.write(table[(d >> 12) & 0X3F]);
                    if (pad) {
                        writer.write((dLimit + 1 < data.length) ? table[(d >> 6) & 0X3F] : '=');
                        writer.write('=');
                    } else {
                        if (dLimit + 1 < data.length) {
                            writer.write(table[(d >> 6) & 0X3F]);
                        }
                    }
                    if (chunked && charCount != 0) {
                        writer.write(CHUNK_SEPARATOR);
                    }
                }

                return writer;
            }

            @Override
            public String toString() {
                Writer buffer = new StringBuilderWriter();

                try {
                    writeTo(buffer);
                } catch (IOException e) {
                    throw new StringWriterIOException(e);
                }

                return buffer.toString();
            }
        };
    }

    /**
     * Produce a Writable object which writes the Base64 encoding of the byte array.
     * Calling toString() on the result returns the encoding as a String. For more
     * information on Base64 encoding and chunking see <code>RFC 4648</code>.
     *
     * @param data byte array to be encoded
     * @return object which will write the Base64 encoding of the byte array
     * @since 1.0
     */
    public static Writable encodeBase64(final byte[] data) {
        return encodeBase64(data, false);
    }

    /**
     * Produce a Writable object which writes the Base64 URL and Filename Safe encoding of the byte array.
     * Calling toString() on the result returns the encoding as a String. For more
     * information on Base64 URL and Filename Safe encoding see <code>RFC 4648 - Section 5
     * Base 64 Encoding with URL and Filename Safe Alphabet</code>.
     * <p>
     * The method omits padding and is equivalent to calling
     * {@link org.codehaus.groovy.runtime.EncodingGroovyMethods#encodeBase64Url(Byte[], boolean)} with a
     * value of {@code false}.
     *
     * @param data Byte array to be encoded
     * @return object which will write the Base64 URL and Filename Safe encoding of the byte array
     * @see org.codehaus.groovy.runtime.EncodingGroovyMethods#encodeBase64Url(Byte[], boolean)
     * @since 2.5.0
     */
    public static Writable encodeBase64Url(Byte[] data) {
        return encodeBase64Url(data, false);
    }

    /**
     * Produce a Writable object which writes the Base64 URL and Filename Safe encoding of the byte array.
     * Calling toString() on the result returns the encoding as a String. For more
     * information on Base64 URL and Filename Safe encoding see <code>RFC 4648 - Section 5
     * Base 64 Encoding with URL and Filename Safe Alphabet</code>.
     *
     * @param data Byte array to be encoded
     * @param pad whether or not the encoded data should be padded
     * @return object which will write the Base64 URL and Filename Safe encoding of the byte array
     * @since 2.5.0
     */
    public static Writable encodeBase64Url(Byte[] data, boolean pad) {
        return encodeBase64Url(DefaultTypeTransformation.convertToByteArray(data), pad);
    }

    /**
     * Produce a Writable object which writes the Base64 URL and Filename Safe encoding of the byte array.
     * Calling toString() on the result returns the encoding as a String. For more
     * information on Base64 URL and Filename Safe encoding see <code>RFC 4648 - Section 5
     * Base 64 Encoding with URL and Filename Safe Alphabet</code>.
     * <p>
     * The method omits padding and is equivalent to calling
     * {@link org.codehaus.groovy.runtime.EncodingGroovyMethods#encodeBase64Url(byte[], boolean)} with a
     * value of {@code false}.
     *
     * @param data Byte array to be encoded
     * @return object which will write the Base64 URL and Filename Safe encoding of the byte array
     * @see org.codehaus.groovy.runtime.EncodingGroovyMethods#encodeBase64Url(byte[], boolean)
     * @since 2.5.0
     */
    public static Writable encodeBase64Url(final byte[] data) {
        return encodeBase64Url(data, false);
    }

    /**
     * Produce a Writable object which writes the Base64 URL and Filename Safe encoding of the byte array.
     * Calling toString() on the result returns the encoding as a String. For more
     * information on Base64 URL and Filename Safe encoding see <code>RFC 4648 - Section 5
     * Base 64 Encoding with URL and Filename Safe Alphabet</code>.
     *
     * @param data Byte array to be encoded
     * @param pad whether or not the encoded data should be padded
     * @return object which will write the Base64 URL and Filename Safe encoding of the byte array
     * @since 2.5.0
     */
    public static Writable encodeBase64Url(final byte[] data, final boolean pad) {
        return encodeBase64(data, false, true, pad);
    }

    /**
     * Decode the String from Base64 into a byte array.
     *
     * @param value the string to be decoded
     * @return the decoded bytes as an array
     * @since 1.0
     */
    public static byte[] decodeBase64(String value) {
        return decodeBase64(value, false);
    }

    /**
     * Decodes a Base64 URL and Filename Safe encoded String into a byte array.
     *
     * @param value the string to be decoded
     * @return the decoded bytes as an array
     * @since 2.5.0
     */
    public static byte[] decodeBase64Url(String value) {
        return decodeBase64(value, true);
    }

    private static byte[] decodeBase64(String value, boolean urlSafe) {
        int byteShift = 4;
        int tmp = 0;
        boolean done = false;
        final StringBuilder buffer = new StringBuilder();
        final byte[] table = urlSafe ? TRANSLATE_TABLE_URLSAFE : TRANSLATE_TABLE;
        for (int i = 0; i != value.length(); i++) {
            final char c = value.charAt(i);
            final int sixBit = (c < 123) ? table[c] : 66;

            if (sixBit < 64) {
                if (done)
                    throw new RuntimeException("= character not at end of base64 value"); // TODO: change this exception type

                tmp = (tmp << 6) | sixBit;

                if (byteShift-- != 4) {
                    buffer.append((char) ((tmp >> (byteShift * 2)) & 0XFF));
                }

            } else if (sixBit == 64) {

                byteShift--;
                done = true;

            } else if (sixBit == 66) {
                // RFC 2045 says that I'm allowed to take the presence of
                // these characters as evidence of data corruption
                // So I will
                throw new RuntimeException("bad character in base64 value"); // TODO: change this exception type
            }

            if (byteShift == 0) byteShift = 4;
        }

        return buffer.toString().getBytes(StandardCharsets.ISO_8859_1);
    }

    /**
     * Produces a Writable that writes the hex encoding of the Byte[]. Calling
     * toString() on this Writable returns the hex encoding as a String. The hex
     * encoding includes two characters for each byte and all letters are lower case.
     *
     * @param data byte array to be encoded
     * @return object which will write the hex encoding of the byte array
     * @see Integer#toHexString(int)
     */
    public static Writable encodeHex(final Byte[] data) {
        return encodeHex(DefaultTypeTransformation.convertToByteArray(data));
    }

    /**
     * Produces a Writable that writes the hex encoding of the byte[]. Calling
     * toString() on this Writable returns the hex encoding as a String. The hex
     * encoding includes two characters for each byte and all letters are lower case.
     *
     * @param data byte array to be encoded
     * @return object which will write the hex encoding of the byte array
     * @see Integer#toHexString(int)
     */
    public static Writable encodeHex(final byte[] data) {
        return new Writable() {
            @Override
            public Writer writeTo(Writer out) throws IOException {
                for (byte datum : data) {
                    // convert byte into unsigned hex string
                    String hexString = Integer.toHexString(datum & 0xFF);

                    // add leading zero if the length of the string is one
                    if (hexString.length() < 2) {
                        out.write("0");
                    }

                    // write hex string to writer
                    out.write(hexString);
                }
                return out;
            }

            @Override
            public String toString() {
                Writer buffer = new StringBuilderWriter();

                try {
                    writeTo(buffer);
                } catch (IOException e) {
                    throw new StringWriterIOException(e);
                }

                return buffer.toString();
            }
        };
    }

    /**
     * Decodes a hex string to a byte array. The hex string can contain either upper
     * case or lower case letters.
     *
     * @param value string to be decoded
     * @return decoded byte array
     * @throws NumberFormatException If the string contains an odd number of characters
     *                               or if the characters are not valid hexadecimal values.
     */
    public static byte[] decodeHex(final String value) {
        // if string length is odd then throw exception
        if (value.length() % 2 != 0) {
            throw new NumberFormatException("odd number of characters in hex string");
        }

        byte[] bytes = new byte[value.length() / 2];
        for (int i = 0; i < value.length(); i += 2) {
            bytes[i / 2] = (byte) Integer.parseInt(value.substring(i, i + 2), 16);
        }

        return bytes;
    }

    /**
     * Calculate md5 of the CharSequence instance
     * @return md5 value
     * @throws NoSuchAlgorithmException if MD5 algorithm not found
     * @since 2.5.0
     */
    public static String md5(CharSequence self) throws NoSuchAlgorithmException {
        return digest(self, MD5);
    }

    /**
     * Calculate md5 of the byte array
     * @return md5 value
     * @throws NoSuchAlgorithmException if MD5 algorithm not found
     * @since 2.5.0
     */
    public static String md5(byte[] self) throws NoSuchAlgorithmException {
        return digest(self, MD5);
    }

    /**
     * Calculate SHA-256 of the CharSequence instance
     * @return SHA-256 value
     * @throws NoSuchAlgorithmException if SHA-256 algorithm not found
     * @since 2.5.3
     */
    public static String sha256(CharSequence self) throws NoSuchAlgorithmException {
        return digest(self, SHA_256);
    }

    /**
     * Calculate SHA-256 of the byte array
     * @return SHA-256 value
     * @throws NoSuchAlgorithmException if SHA-256 algorithm not found
     * @since 2.5.3
     */
    public static String sha256(byte[] self) throws NoSuchAlgorithmException {
        return digest(self, SHA_256);
    }

    /**
     * digest the CharSequence instance
     * @param algorithm the name of the algorithm requested, e.g. MD5, SHA-1, SHA-256, etc.
     * @return digested value
     * @throws NoSuchAlgorithmException if the algorithm not found
     * @since 2.5.0
     * @see MessageDigest#getInstance(java.lang.String)
     */
    public static String digest(CharSequence self, String algorithm) throws NoSuchAlgorithmException {
        final String text = self.toString();

        return digest(text.getBytes(StandardCharsets.UTF_8), algorithm);
    }

    /**
     * digest the byte array
     * @param algorithm the name of the algorithm requested, e.g. MD5, SHA-1, SHA-256, etc.
     * @return digested value
     * @throws NoSuchAlgorithmException if the algorithm not found
     * @since 2.5.0
     * @see MessageDigest#getInstance(java.lang.String)
     */
    public static String digest(byte[] self, String algorithm) throws NoSuchAlgorithmException {
        MessageDigest md = MessageDigest.getInstance(algorithm);
        md.update(ByteBuffer.wrap(self));

        return encodeHex(md.digest()).toString();
    }
}
