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;

    private final static int INITIAL_CHAR_BUFFER_SIZE = 120;
    private final static int INITIAL_BYTE_BUFFER_SIZE = 200;

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

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

    
Method that will quote text contents using JSON standard quoting,
and return results as a character array
/**
     * Method that will quote text contents using JSON standard quoting,
     * and return results as a character array
     */
    public char[] quoteAsString(String input)
    {
        char[] outputBuffer = new char[INITIAL_CHAR_BUFFER_SIZE];
        final int[] escCodes = CharTypes.get7BitOutputEscapes();
        final int escCodeCount = escCodes.length;
        int inPtr = 0;
        final int inputLen = input.length();
        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). 
Since:
2.10/**
     * Overloaded variant of {@link #quoteAsString(String)}.
     *
     * @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;

        char[] outputBuffer = new char[INITIAL_CHAR_BUFFER_SIZE];
        final int[] escCodes = CharTypes.get7BitOutputEscapes();
        final int escCodeCount = escCodes.length;
        int inPtr = 0;
        final int inputLen = input.length();
        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. 
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.
     *
     * @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);
        }
    }

    
Will quote given JSON String value using standard quoting, encode
results as UTF-8, and return result as a byte array.
/**
     * Will quote given JSON String value using standard quoting, encode
     * results as UTF-8, and return result as a byte array.
     */
    @SuppressWarnings("resource")
    public byte[] quoteAsUTF8(String text)
    {
        int inputPtr = 0;
        int inputEnd = text.length();
        int outputPtr = 0;
        byte[] outputBuffer = new byte[INITIAL_BYTE_BUFFER_SIZE];
        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 quoting), return
resulting byte array.
/**
     * Will encode given String as UTF-8 (without any quoting), return
     * resulting byte array.
     */
    @SuppressWarnings("resource")
    public byte[] encodeAsUTF8(String text)
    {
        int inputPtr = 0;
        int inputEnd = text.length();
        int outputPtr = 0;
        byte[] outputBuffer = new byte[INITIAL_BYTE_BUFFER_SIZE];
        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));
    }
}