package com.fasterxml.jackson.core.io;

import java.util.Arrays;

import com.fasterxml.jackson.core.util.ByteArrayBuilder;
import com.fasterxml.jackson.core.util.TextBuffer;

Helper class used for efficient encoding of JSON String values (including
JSON field names) into Strings or UTF-8 byte arrays.

Note that methods in here are somewhat optimized, but not ridiculously so.
Reason is that conversion method results are expected to be cached so that
these methods will not be hot spots during normal operation.
/**
 * Helper class used for efficient encoding of JSON String values (including
 * JSON field names) into Strings or UTF-8 byte arrays.
 *<p>
 * Note that methods in here are somewhat optimized, but not ridiculously so.
 * Reason is that conversion method results are expected to be cached so that
 * these methods will not be hot spots during normal operation.
 */
public final class JsonStringEncoder
{
    /*
    /**********************************************************************
    /* Constants
    /**********************************************************************
     */

    private final static char[] HC = CharTypes.copyHexChars();

    private final static byte[] HB = CharTypes.copyHexBytes();

    private final static int SURR1_FIRST = 0xD800;
    private final static int SURR1_LAST = 0xDBFF;
    private final static int SURR2_FIRST = 0xDC00;
    private final static int SURR2_LAST = 0xDFFF;

    // 18-Aug-2021, tatu: [core#712] Change to more dynamic allocation; try
    //    to estimate ok initial encoding buffer, switch to segmented for
    //    possible (but rare) big content

    final static int MIN_CHAR_BUFFER_SIZE = 16;
    final static int MAX_CHAR_BUFFER_SIZE = 32000; // use segments beyond
    final static int MIN_BYTE_BUFFER_SIZE = 24;
    final static int MAX_BYTE_BUFFER_SIZE = 32000; // use segments beyond

    /*
    /**********************************************************************
    /* Construction, instance access
    /**********************************************************************
     */

    // Since 2.10 we have stateless singleton and NO fancy ThreadLocal/SofRef caching!!!
    private final static JsonStringEncoder instance = new JsonStringEncoder();
    
    public JsonStringEncoder() { }

    
Factory method for getting an instance; this is either recycled per-thread instance,
or a newly constructed one.
Returns:
Static stateless encoder instance/**
     * Factory method for getting an instance; this is either recycled per-thread instance,
     * or a newly constructed one.
     *
     * @return Static stateless encoder instance
     */
    public static JsonStringEncoder getInstance() {
        return instance;
    }

    /*
    /**********************************************************************
    /* Public API
    /**********************************************************************
     */

    
Method that will escape text contents using JSON standard escaping,
and return results as a character array.
Params:
input – Value String to process
Returns:
JSON-escaped String matching input/**
     * Method that will escape text contents using JSON standard escaping,
     * and return results as a character array.
     *
     * @param input Value String to process
     *
     * @return JSON-escaped String matching {@code input}
     */
    public char[] quoteAsString(String input)
    {
        final int inputLen = input.length();
        char[] outputBuffer = new char[_initialCharBufSize(inputLen)];
        final int[] escCodes = CharTypes.get7BitOutputEscapes();
        final int escCodeCount = escCodes.length;
        int inPtr = 0;
        TextBuffer textBuffer = null;
        int outPtr = 0;
        char[] qbuf = null;

        outer:
        while (inPtr < inputLen) {
            tight_loop:
            while (true) {
                char c = input.charAt(inPtr);
                if (c < escCodeCount && escCodes[c] != 0) {
                    break tight_loop;
                }
                if (outPtr >= outputBuffer.length) {
                    if (textBuffer == null) {
                        textBuffer = TextBuffer.fromInitial(outputBuffer);
                    }
                    outputBuffer = textBuffer.finishCurrentSegment();
                    outPtr = 0;
                }
                outputBuffer[outPtr++] = c;
                if (++inPtr >= inputLen) {
                    break outer;
                }
            }
            // something to escape; 2 or 6-char variant? 
            if (qbuf == null) {
                qbuf = _qbuf();
            }
            char d = input.charAt(inPtr++);
            int escCode = escCodes[d];
            int length = (escCode < 0)
                    ? _appendNumeric(d, qbuf)
                    : _appendNamed(escCode, qbuf);
                    ;
            if ((outPtr + length) > outputBuffer.length) {
                int first = outputBuffer.length - outPtr;
                if (first > 0) {
                    System.arraycopy(qbuf, 0, outputBuffer, outPtr, first);
                }
                if (textBuffer == null) {
                    textBuffer = TextBuffer.fromInitial(outputBuffer);
                }
                outputBuffer = textBuffer.finishCurrentSegment();
                int second = length - first;
                System.arraycopy(qbuf, first, outputBuffer, 0, second);
                outPtr = second;
            } else {
                System.arraycopy(qbuf, 0, outputBuffer, outPtr, length);
                outPtr += length;
            }
        }

        if (textBuffer == null) {
            return Arrays.copyOfRange(outputBuffer, 0, outPtr);
        }
        textBuffer.setCurrentLength(outPtr);
        return textBuffer.contentsAsArray();
    }

    
Overloaded variant of quoteAsString(String). 
Params:
input – Value CharSequence to process
Returns:
JSON-escaped String matching input
Since:
2.10/**
     * Overloaded variant of {@link #quoteAsString(String)}.
     *
     * @param input Value {@link CharSequence} to process
     *
     * @return JSON-escaped String matching {@code input}
     *
     * @since 2.10
     */
    public char[] quoteAsString(CharSequence input)
    {
        // 15-Aug-2019, tatu: Optimize common case as JIT can't get rid of overhead otherwise
        if (input instanceof String) {
            return quoteAsString((String) input);
        }

        TextBuffer textBuffer = null;

        final int inputLen = input.length();
        char[] outputBuffer = new char[_initialCharBufSize(inputLen)];
        final int[] escCodes = CharTypes.get7BitOutputEscapes();
        final int escCodeCount = escCodes.length;
        int inPtr = 0;
        int outPtr = 0;
        char[] qbuf = null;
 
        outer:
        while (inPtr < inputLen) {
            tight_loop:
            while (true) {
                char c = input.charAt(inPtr);
                if (c < escCodeCount && escCodes[c] != 0) {
                    break tight_loop;
                }
                if (outPtr >= outputBuffer.length) {
                    if (textBuffer == null) {
                        textBuffer = TextBuffer.fromInitial(outputBuffer);
                    }
                    outputBuffer = textBuffer.finishCurrentSegment();
                    outPtr = 0;
                }
                outputBuffer[outPtr++] = c;
                if (++inPtr >= inputLen) {
                    break outer;
                }
            }
            // something to escape; 2 or 6-char variant? 
            if (qbuf == null) {
                qbuf = _qbuf();
            }
            char d = input.charAt(inPtr++);
            int escCode = escCodes[d];
            int length = (escCode < 0)
                    ? _appendNumeric(d, qbuf)
                    : _appendNamed(escCode, qbuf);
                    ;
            if ((outPtr + length) > outputBuffer.length) {
                int first = outputBuffer.length - outPtr;
                if (first > 0) {
                    System.arraycopy(qbuf, 0, outputBuffer, outPtr, first);
                }
                if (textBuffer == null) {
                    textBuffer = TextBuffer.fromInitial(outputBuffer);
                }
                outputBuffer = textBuffer.finishCurrentSegment();
                int second = length - first;
                System.arraycopy(qbuf, first, outputBuffer, 0, second);
                outPtr = second;
            } else {
                System.arraycopy(qbuf, 0, outputBuffer, outPtr, length);
                outPtr += length;
            }
        }

        if (textBuffer == null) {
            return Arrays.copyOfRange(outputBuffer, 0, outPtr);
        }
        textBuffer.setCurrentLength(outPtr);
        return textBuffer.contentsAsArray();
    }

    
Method that will quote text contents using JSON standard quoting, and append results to a supplied StringBuilder. Use this variant if you have e.g. a StringBuilder and want to avoid superfluous copying of it. 
Params:
input – Value CharSequence to process
output – StringBuilder to append escaped contents to
Since:
2.8/**
     * Method that will quote text contents using JSON standard quoting,
     * and append results to a supplied {@link StringBuilder}.
     * Use this variant if you have e.g. a {@link StringBuilder} and want to avoid superfluous copying of it.
     *
     * @param input Value {@link CharSequence} to process
     * @param output {@link StringBuilder} to append escaped contents to
     *
     * @since 2.8
     */
    public void quoteAsString(CharSequence input, StringBuilder output)
    {
        final int[] escCodes = CharTypes.get7BitOutputEscapes();
        final int escCodeCount = escCodes.length;
        int inPtr = 0;
        final int inputLen = input.length();
        char[] qbuf = null;

        outer:
        while (inPtr < inputLen) {
            tight_loop:
            while (true) {
                char c = input.charAt(inPtr);
                if (c < escCodeCount && escCodes[c] != 0) {
                    break tight_loop;
                }
                output.append(c);
                if (++inPtr >= inputLen) {
                    break outer;
                }
            }
            // something to escape; 2 or 6-char variant?
            if (qbuf == null) {
                qbuf = _qbuf();
            }
            char d = input.charAt(inPtr++);
            int escCode = escCodes[d];
            int length = (escCode < 0)
                    ? _appendNumeric(d, qbuf)
                    : _appendNamed(escCode, qbuf);
            output.append(qbuf, 0, length);
        }
    }

    
Method that will escape text contents using JSON standard escaping,
encode resulting String as UTF-8 bytes
and return results as a  byte array.
Params:
text – Value String to process
Returns:
UTF-8 encoded bytes of JSON-escaped text/**
     * Method that will escape text contents using JSON standard escaping,
     * encode resulting String as UTF-8 bytes
     * and return results as a  byte array.
     *
     * @param text Value {@link String} to process
     *
     * @return UTF-8 encoded bytes of JSON-escaped {@code text}
     */
    @SuppressWarnings("resource")
    public byte[] quoteAsUTF8(String text)
    {
        int inputPtr = 0;
        int inputEnd = text.length();
        int outputPtr = 0;
        byte[] outputBuffer = new byte[_initialByteBufSize(inputEnd)];
        ByteArrayBuilder bb = null;
        
        main:
        while (inputPtr < inputEnd) {
            final int[] escCodes = CharTypes.get7BitOutputEscapes();

            inner_loop: // ASCII and escapes
            while (true) {
                int ch = text.charAt(inputPtr);
                if (ch > 0x7F || escCodes[ch] != 0) {
                    break inner_loop;
                }
                if (outputPtr >= outputBuffer.length) {
                    if (bb == null) {
                        bb = ByteArrayBuilder.fromInitial(outputBuffer, outputPtr);
                    }
                    outputBuffer = bb.finishCurrentSegment();
                    outputPtr = 0;
                }
                outputBuffer[outputPtr++] = (byte) ch;
                if (++inputPtr >= inputEnd) {
                    break main;
                }
            }
            if (bb == null) {
                bb = ByteArrayBuilder.fromInitial(outputBuffer, outputPtr);
            }
            if (outputPtr >= outputBuffer.length) {
                outputBuffer = bb.finishCurrentSegment();
                outputPtr = 0;
            }
            // Ok, so what did we hit?
            int ch = (int) text.charAt(inputPtr++);
            if (ch <= 0x7F) { // needs quoting
                int escape = escCodes[ch];
                // ctrl-char, 6-byte escape...
                outputPtr = _appendByte(ch, escape, bb, outputPtr);
                outputBuffer = bb.getCurrentSegment();
                continue main;
            }
            if (ch <= 0x7FF) { // fine, just needs 2 byte output
                outputBuffer[outputPtr++] = (byte) (0xc0 | (ch >> 6));
                ch = (0x80 | (ch & 0x3f));
            } else { // 3 or 4 bytes
                // Surrogates?
                if (ch < SURR1_FIRST || ch > SURR2_LAST) { // nope
                    outputBuffer[outputPtr++] = (byte) (0xe0 | (ch >> 12));
                    if (outputPtr >= outputBuffer.length) {
                        outputBuffer = bb.finishCurrentSegment();
                        outputPtr = 0;
                    }
                    outputBuffer[outputPtr++] = (byte) (0x80 | ((ch >> 6) & 0x3f));
                    ch = (0x80 | (ch & 0x3f));
                } else { // yes, surrogate pair
                    if (ch > SURR1_LAST) { // must be from first range
                        _illegal(ch);
                    }
                    // and if so, followed by another from next range
                    if (inputPtr >= inputEnd) {
                        _illegal(ch);
                    }
                    ch = _convert(ch, text.charAt(inputPtr++));
                    if (ch > 0x10FFFF) { // illegal, as per RFC 4627
                        _illegal(ch);
                    }
                    outputBuffer[outputPtr++] = (byte) (0xf0 | (ch >> 18));
                    if (outputPtr >= outputBuffer.length) {
                        outputBuffer = bb.finishCurrentSegment();
                        outputPtr = 0;
                    }
                    outputBuffer[outputPtr++] = (byte) (0x80 | ((ch >> 12) & 0x3f));
                    if (outputPtr >= outputBuffer.length) {
                        outputBuffer = bb.finishCurrentSegment();
                        outputPtr = 0;
                    }
                    outputBuffer[outputPtr++] = (byte) (0x80 | ((ch >> 6) & 0x3f));
                    ch = (0x80 | (ch & 0x3f));
                }
            }
            if (outputPtr >= outputBuffer.length) {
                outputBuffer = bb.finishCurrentSegment();
                outputPtr = 0;
            }
            outputBuffer[outputPtr++] = (byte) ch;
        }
        if (bb == null) {
            return Arrays.copyOfRange(outputBuffer, 0, outputPtr);
        }
        return bb.completeAndCoalesce(outputPtr);
    }

    
Will encode given String as UTF-8 (without any escaping) and return
the resulting byte array.
Params:
text – Value String to process
Returns:
UTF-8 encoded bytes of text (without any escaping)/**
     * Will encode given String as UTF-8 (without any escaping) and return
     * the resulting byte array.
     *
     * @param text Value {@link String} to process
     *
     * @return UTF-8 encoded bytes of {@code text} (without any escaping)
     */
    @SuppressWarnings("resource")
    public byte[] encodeAsUTF8(String text)
    {
        int inputPtr = 0;
        int inputEnd = text.length();
        int outputPtr = 0;
        byte[] outputBuffer = new byte[_initialByteBufSize(inputEnd)];
        int outputEnd = outputBuffer.length;
        ByteArrayBuilder bb = null;

        main_loop:
        while (inputPtr < inputEnd) {
            int c = text.charAt(inputPtr++);

            // first tight loop for ascii
            while (c <= 0x7F) {
                if (outputPtr >= outputEnd) {
                    if (bb == null) {
                        bb = ByteArrayBuilder.fromInitial(outputBuffer, outputPtr);
                    }
                    outputBuffer = bb.finishCurrentSegment();
                    outputEnd = outputBuffer.length;
                    outputPtr = 0;
                }
                outputBuffer[outputPtr++] = (byte) c;
                if (inputPtr >= inputEnd) {
                    break main_loop;
                }
                c = text.charAt(inputPtr++);
            }

            // then multi-byte...
            if (bb == null) {
                bb = ByteArrayBuilder.fromInitial(outputBuffer, outputPtr);
            }
            if (outputPtr >= outputEnd) {
                outputBuffer = bb.finishCurrentSegment();
                outputEnd = outputBuffer.length;
                outputPtr = 0;
            }
            if (c < 0x800) { // 2-byte
                outputBuffer[outputPtr++] = (byte) (0xc0 | (c >> 6));
            } else { // 3 or 4 bytes
                // Surrogates?
                if (c < SURR1_FIRST || c > SURR2_LAST) { // nope
                    outputBuffer[outputPtr++] = (byte) (0xe0 | (c >> 12));
                    if (outputPtr >= outputEnd) {
                        outputBuffer = bb.finishCurrentSegment();
                        outputEnd = outputBuffer.length;
                        outputPtr = 0;
                    }
                    outputBuffer[outputPtr++] = (byte) (0x80 | ((c >> 6) & 0x3f));
                } else { // yes, surrogate pair
                    if (c > SURR1_LAST) { // must be from first range
                        _illegal(c);
                    }
                    // and if so, followed by another from next range
                    if (inputPtr >= inputEnd) {
                        _illegal(c);
                    }
                    c = _convert(c, text.charAt(inputPtr++));
                    if (c > 0x10FFFF) { // illegal, as per RFC 4627
                        _illegal(c);
                    }
                    outputBuffer[outputPtr++] = (byte) (0xf0 | (c >> 18));
                    if (outputPtr >= outputEnd) {
                        outputBuffer = bb.finishCurrentSegment();
                        outputEnd = outputBuffer.length;
                        outputPtr = 0;
                    }
                    outputBuffer[outputPtr++] = (byte) (0x80 | ((c >> 12) & 0x3f));
                    if (outputPtr >= outputEnd) {
                        outputBuffer = bb.finishCurrentSegment();
                        outputEnd = outputBuffer.length;
                        outputPtr = 0;
                    }
                    outputBuffer[outputPtr++] = (byte) (0x80 | ((c >> 6) & 0x3f));
                }
            }
            if (outputPtr >= outputEnd) {
                outputBuffer = bb.finishCurrentSegment();
                outputEnd = outputBuffer.length;
                outputPtr = 0;
            }
            outputBuffer[outputPtr++] = (byte) (0x80 | (c & 0x3f));
        }
        if (bb == null) {
            return Arrays.copyOfRange(outputBuffer, 0, outputPtr);
        }
        return bb.completeAndCoalesce(outputPtr);
    }

    
Overloaded variant of encodeAsUTF8(String). 
Params:
text – Value CharSequence to process
Returns:
UTF-8 encoded bytes of text (without any escaping)
Since:
2.11/**
     * Overloaded variant of {@link #encodeAsUTF8(String)}.
     *
     * @param text Value {@link CharSequence} to process
     *
     * @return UTF-8 encoded bytes of {@code text} (without any escaping)
     *
     * @since 2.11
     */
    @SuppressWarnings("resource")
    public byte[] encodeAsUTF8(CharSequence text)
    {
        int inputPtr = 0;
        int inputEnd = text.length();
        int outputPtr = 0;
        byte[] outputBuffer = new byte[_initialByteBufSize(inputEnd)];
        int outputEnd = outputBuffer.length;
        ByteArrayBuilder bb = null;

        main_loop:
        while (inputPtr < inputEnd) {
            int c = text.charAt(inputPtr++);

            // first tight loop for ascii
            while (c <= 0x7F) {
                if (outputPtr >= outputEnd) {
                    if (bb == null) {
                        bb = ByteArrayBuilder.fromInitial(outputBuffer, outputPtr);
                    }
                    outputBuffer = bb.finishCurrentSegment();
                    outputEnd = outputBuffer.length;
                    outputPtr = 0;
                }
                outputBuffer[outputPtr++] = (byte) c;
                if (inputPtr >= inputEnd) {
                    break main_loop;
                }
                c = text.charAt(inputPtr++);
            }

            // then multi-byte...
            if (bb == null) {
                bb = ByteArrayBuilder.fromInitial(outputBuffer, outputPtr);
            }
            if (outputPtr >= outputEnd) {
                outputBuffer = bb.finishCurrentSegment();
                outputEnd = outputBuffer.length;
                outputPtr = 0;
            }
            if (c < 0x800) { // 2-byte
                outputBuffer[outputPtr++] = (byte) (0xc0 | (c >> 6));
            } else { // 3 or 4 bytes
                // Surrogates?
                if (c < SURR1_FIRST || c > SURR2_LAST) { // nope
                    outputBuffer[outputPtr++] = (byte) (0xe0 | (c >> 12));
                    if (outputPtr >= outputEnd) {
                        outputBuffer = bb.finishCurrentSegment();
                        outputEnd = outputBuffer.length;
                        outputPtr = 0;
                    }
                    outputBuffer[outputPtr++] = (byte) (0x80 | ((c >> 6) & 0x3f));
                } else { // yes, surrogate pair
                    if (c > SURR1_LAST) { // must be from first range
                        _illegal(c);
                    }
                    // and if so, followed by another from next range
                    if (inputPtr >= inputEnd) {
                        _illegal(c);
                    }
                    c = _convert(c, text.charAt(inputPtr++));
                    if (c > 0x10FFFF) { // illegal, as per RFC 4627
                        _illegal(c);
                    }
                    outputBuffer[outputPtr++] = (byte) (0xf0 | (c >> 18));
                    if (outputPtr >= outputEnd) {
                        outputBuffer = bb.finishCurrentSegment();
                        outputEnd = outputBuffer.length;
                        outputPtr = 0;
                    }
                    outputBuffer[outputPtr++] = (byte) (0x80 | ((c >> 12) & 0x3f));
                    if (outputPtr >= outputEnd) {
                        outputBuffer = bb.finishCurrentSegment();
                        outputEnd = outputBuffer.length;
                        outputPtr = 0;
                    }
                    outputBuffer[outputPtr++] = (byte) (0x80 | ((c >> 6) & 0x3f));
                }
            }
            if (outputPtr >= outputEnd) {
                outputBuffer = bb.finishCurrentSegment();
                outputEnd = outputBuffer.length;
                outputPtr = 0;
            }
            outputBuffer[outputPtr++] = (byte) (0x80 | (c & 0x3f));
        }
        if (bb == null) {
            return Arrays.copyOfRange(outputBuffer, 0, outputPtr);
        }
        return bb.completeAndCoalesce(outputPtr);
    }

    /*
    /**********************************************************************
    /* Internal methods
    /**********************************************************************
     */

    private char[] _qbuf() {
        char[] qbuf = new char[6];
        qbuf[0] = '\\';
        qbuf[2] = '0';
        qbuf[3] = '0';
        return qbuf;
    }

    private int _appendNumeric(int value, char[] qbuf) {
        qbuf[1] = 'u';
        // We know it's a control char, so only the last 2 chars are non-0
        qbuf[4] = HC[value >> 4];
        qbuf[5] = HC[value & 0xF];
        return 6;
    }

    private int _appendNamed(int esc, char[] qbuf) {
        qbuf[1] = (char) esc;
        return 2;
    }

    private int _appendByte(int ch, int esc, ByteArrayBuilder bb, int ptr)
    {
        bb.setCurrentSegmentLength(ptr);
        bb.append('\\');
        if (esc < 0) { // standard escape
            bb.append('u');
            if (ch > 0xFF) {
                int hi = (ch >> 8);
                bb.append(HB[hi >> 4]);
                bb.append(HB[hi & 0xF]);
                ch &= 0xFF;
            } else {
                bb.append('0');
                bb.append('0');
            }
            bb.append(HB[ch >> 4]);
            bb.append(HB[ch & 0xF]);
        } else { // 2-char simple escape
            bb.append((byte) esc);
        }
        return bb.getCurrentSegmentLength();
    }

    private static int _convert(int p1, int p2) {
        // Ok, then, is the second part valid?
        if (p2 < SURR2_FIRST || p2 > SURR2_LAST) {
            throw new IllegalArgumentException("Broken surrogate pair: first char 0x"+Integer.toHexString(p1)+", second 0x"+Integer.toHexString(p2)+"; illegal combination");
        }
        return 0x10000 + ((p1 - SURR1_FIRST) << 10) + (p2 - SURR2_FIRST);
    }

    private static void _illegal(int c) {
        throw new IllegalArgumentException(UTF8Writer.illegalSurrogateDesc(c));
    }

    // non-private for unit test access
    static int _initialCharBufSize(int strLen) {
        // char->char won't expand but we need to give some room for escaping
        // like 1/8 (12.5% expansion) but cap addition to something modest
        final int estimated = Math.max(MIN_CHAR_BUFFER_SIZE,
                strLen + Math.min(6 + (strLen >> 3), 1000));
        return Math.min(estimated, MAX_CHAR_BUFFER_SIZE);
    }

    // non-private for unit test access
    static int _initialByteBufSize(int strLen) {
        // char->byte for UTF-8 can expand size by x3 itself, and escaping
        // more... but let's use lower factor of 1.5
        final int doubled = Math.max(MIN_BYTE_BUFFER_SIZE, strLen + 6 + (strLen>>1));
        // but use upper bound for humongous cases (segmented)
        return Math.min(doubled, MAX_BYTE_BUFFER_SIZE);
    }
}