/*

 * Copyright (c) 2003, 2019, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package java.lang;

import jdk.internal.math.FloatingDecimal;

import java.util.Arrays;

import java.util.Spliterator;

import java.util.stream.IntStream;

import java.util.stream.StreamSupport;

import static java.lang.String.COMPACT_STRINGS;

import static java.lang.String.UTF16;

import static java.lang.String.LATIN1;

import static java.lang.String.checkIndex;

import static java.lang.String.checkOffset;

/**

 * A mutable sequence of characters.

 * <p>

 * Implements a modifiable string. At any point in time it contains some

 * particular sequence of characters, but the length and content of the

 * sequence can be changed through certain method calls.

 *

 * <p>Unless otherwise noted, passing a {@code null} argument to a constructor

 * or method in this class will cause a {@link NullPointerException} to be

 * thrown.

 *

 * @author      Michael McCloskey

 * @author      Martin Buchholz

 * @author      Ulf Zibis

 * @since       1.5

 */

abstract class AbstractStringBuilder implements Appendable, CharSequence {

    /**

     * The value is used for character storage.

     */

    byte[] value;

    /**

     * The id of the encoding used to encode the bytes in {@code value}.

     */

    byte coder;

    /**

     * The count is the number of characters used.

     */

    int count;

    private static final byte[] EMPTYVALUE = new byte[0];

    /**

     * This no-arg constructor is necessary for serialization of subclasses.

     */

    AbstractStringBuilder() {

        value = EMPTYVALUE;

    }

    /**

     * Creates an AbstractStringBuilder of the specified capacity.

     */

    AbstractStringBuilder(int capacity) {

        if (COMPACT_STRINGS) {

            value = new byte[capacity];

            coder = LATIN1;

        } else {

            value = StringUTF16.newBytesFor(capacity);

            coder = UTF16;

        }

    }

    /**

     * Constructs an AbstractStringBuilder that contains the same characters

     * as the specified {@code String}. The initial capacity of

     * the string builder is {@code 16} plus the length of the

     * {@code String} argument.

     *

     * @param      str   the string to copy.

     */

    AbstractStringBuilder(String str) {

        int length = str.length();

        int capacity = (length < Integer.MAX_VALUE - 16)

                ? length + 16 : Integer.MAX_VALUE;

        final byte initCoder = str.coder();

        coder = initCoder;

        value = (initCoder == LATIN1)

                ? new byte[capacity] : StringUTF16.newBytesFor(capacity);

        append(str);

    }

    /**

     * Constructs an AbstractStringBuilder that contains the same characters

     * as the specified {@code CharSequence}. The initial capacity of

     * the string builder is {@code 16} plus the length of the

     * {@code CharSequence} argument.

     *

     * @param      seq   the sequence to copy.

     */

    AbstractStringBuilder(CharSequence seq) {

        int length = seq.length();

        if (length < 0) {

            throw new NegativeArraySizeException("Negative length: " + length);

        }

        int capacity = (length < Integer.MAX_VALUE - 16)

                ? length + 16 : Integer.MAX_VALUE;

        final byte initCoder;

        if (COMPACT_STRINGS) {

            if (seq instanceof AbstractStringBuilder) {

                initCoder = ((AbstractStringBuilder)seq).getCoder();

            } else if (seq instanceof String) {

                initCoder = ((String)seq).coder();

            } else {

                initCoder = LATIN1;

            }

        } else {

            initCoder = UTF16;

        }

        coder = initCoder;

        value = (initCoder == LATIN1)

                ? new byte[capacity] : StringUTF16.newBytesFor(capacity);

        append(seq);

    }

    /**

     * Compares the objects of two AbstractStringBuilder implementations lexicographically.

     *

     * @since 11

     */

    int compareTo(AbstractStringBuilder another) {

        if (this == another) {

            return 0;

        }

        byte val1[] = value;

        byte val2[] = another.value;

        int count1 = this.count;

        int count2 = another.count;

        if (coder == another.coder) {

            return isLatin1() ? StringLatin1.compareTo(val1, val2, count1, count2)

                              : StringUTF16.compareTo(val1, val2, count1, count2);

        }

        return isLatin1() ? StringLatin1.compareToUTF16(val1, val2, count1, count2)

                          : StringUTF16.compareToLatin1(val1, val2, count1, count2);

    }

    /**

     * Returns the length (character count).

     *

     * @return  the length of the sequence of characters currently

     *          represented by this object

     */

    @Override

    public int length() {

        return count;

    }

    /**

     * Returns the current capacity. The capacity is the amount of storage

     * available for newly inserted characters, beyond which an allocation

     * will occur.

     *

     * @return  the current capacity

     */

    public int capacity() {

        return value.length >> coder;

    }

    /**

     * Ensures that the capacity is at least equal to the specified minimum.

     * If the current capacity is less than the argument, then a new internal

     * array is allocated with greater capacity. The new capacity is the

     * larger of:

     * <ul>

     * <li>The {@code minimumCapacity} argument.

     * <li>Twice the old capacity, plus {@code 2}.

     * </ul>

     * If the {@code minimumCapacity} argument is nonpositive, this

     * method takes no action and simply returns.

     * Note that subsequent operations on this object can reduce the

     * actual capacity below that requested here.

     *

     * @param   minimumCapacity   the minimum desired capacity.

     */

    public void ensureCapacity(int minimumCapacity) {

        if (minimumCapacity > 0) {

            ensureCapacityInternal(minimumCapacity);

        }

    }

    /**

     * For positive values of {@code minimumCapacity}, this method

     * behaves like {@code ensureCapacity}, however it is never

     * synchronized.

     * If {@code minimumCapacity} is non positive due to numeric

     * overflow, this method throws {@code OutOfMemoryError}.

     */

    private void ensureCapacityInternal(int minimumCapacity) {

        // overflow-conscious code

        int oldCapacity = value.length >> coder;

        if (minimumCapacity - oldCapacity > 0) {

            value = Arrays.copyOf(value,

                    newCapacity(minimumCapacity) << coder);

        }

    }

    /**

     * The maximum size of array to allocate (unless necessary).

     * Some VMs reserve some header words in an array.

     * Attempts to allocate larger arrays may result in

     * OutOfMemoryError: Requested array size exceeds VM limit

     */

    private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;

    /**

     * Returns a capacity at least as large as the given minimum capacity.

     * Returns the current capacity increased by the same amount + 2 if

     * that suffices.

     * Will not return a capacity greater than

     * {@code (MAX_ARRAY_SIZE >> coder)} unless the given minimum capacity

     * is greater than that.

     *

     * @param  minCapacity the desired minimum capacity

     * @throws OutOfMemoryError if minCapacity is less than zero or

     *         greater than (Integer.MAX_VALUE >> coder)

     */

    private int newCapacity(int minCapacity) {

        // overflow-conscious code

        int oldCapacity = value.length >> coder;

        int newCapacity = (oldCapacity << 1) + 2;

        if (newCapacity - minCapacity < 0) {

            newCapacity = minCapacity;

        }

        int SAFE_BOUND = MAX_ARRAY_SIZE >> coder;

        return (newCapacity <= 0 || SAFE_BOUND - newCapacity < 0)

            ? hugeCapacity(minCapacity)

            : newCapacity;

    }

    private int hugeCapacity(int minCapacity) {

        int SAFE_BOUND = MAX_ARRAY_SIZE >> coder;

        int UNSAFE_BOUND = Integer.MAX_VALUE >> coder;

        if (UNSAFE_BOUND - minCapacity < 0) { // overflow

            throw new OutOfMemoryError();

        }

        return (minCapacity > SAFE_BOUND)

            ? minCapacity : SAFE_BOUND;

    }

    /**

     * If the coder is "isLatin1", this inflates the internal 8-bit storage

     * to 16-bit <hi=0, low> pair storage.

     */

    private void inflate() {

        if (!isLatin1()) {

            return;

        }

        byte[] buf = StringUTF16.newBytesFor(value.length);

        StringLatin1.inflate(value, 0, buf, 0, count);

        this.value = buf;

        this.coder = UTF16;

    }

    /**

     * Attempts to reduce storage used for the character sequence.

     * If the buffer is larger than necessary to hold its current sequence of

     * characters, then it may be resized to become more space efficient.

     * Calling this method may, but is not required to, affect the value

     * returned by a subsequent call to the {@link #capacity()} method.

     */

    public void trimToSize() {

        int length = count << coder;

        if (length < value.length) {

            value = Arrays.copyOf(value, length);

        }

    }

    /**

     * Sets the length of the character sequence.

     * The sequence is changed to a new character sequence

     * whose length is specified by the argument. For every nonnegative

     * index <i>k</i> less than {@code newLength}, the character at

     * index <i>k</i> in the new character sequence is the same as the

     * character at index <i>k</i> in the old sequence if <i>k</i> is less

     * than the length of the old character sequence; otherwise, it is the

     * null character {@code '\u005Cu0000'}.

     *

     * In other words, if the {@code newLength} argument is less than

     * the current length, the length is changed to the specified length.

     * <p>

     * If the {@code newLength} argument is greater than or equal

     * to the current length, sufficient null characters

     * ({@code '\u005Cu0000'}) are appended so that

     * length becomes the {@code newLength} argument.

     * <p>

     * The {@code newLength} argument must be greater than or equal

     * to {@code 0}.

     *

     * @param      newLength   the new length

     * @throws     IndexOutOfBoundsException  if the

     *               {@code newLength} argument is negative.

     */

    public void setLength(int newLength) {

        if (newLength < 0) {

            throw new StringIndexOutOfBoundsException(newLength);

        }

        ensureCapacityInternal(newLength);

        if (count < newLength) {

            if (isLatin1()) {

                StringLatin1.fillNull(value, count, newLength);

            } else {

                StringUTF16.fillNull(value, count, newLength);

            }

        }

        count = newLength;

    }

    /**

     * Returns the {@code char} value in this sequence at the specified index.

     * The first {@code char} value is at index {@code 0}, the next at index

     * {@code 1}, and so on, as in array indexing.

     * <p>

     * The index argument must be greater than or equal to

     * {@code 0}, and less than the length of this sequence.

     *

     * <p>If the {@code char} value specified by the index is a

     * <a href="Character.html#unicode">surrogate</a>, the surrogate

     * value is returned.

     *

     * @param      index   the index of the desired {@code char} value.

     * @return     the {@code char} value at the specified index.

     * @throws     IndexOutOfBoundsException  if {@code index} is

     *             negative or greater than or equal to {@code length()}.

     */

    @Override

    public char charAt(int index) {

        checkIndex(index, count);

        if (isLatin1()) {

            return (char)(value[index] & 0xff);

        }

        return StringUTF16.charAt(value, index);

    }

    /**

     * Returns the character (Unicode code point) at the specified

     * index. The index refers to {@code char} values

     * (Unicode code units) and ranges from {@code 0} to

     * {@link #length()}{@code  - 1}.

     *

     * <p> If the {@code char} value specified at the given index

     * is in the high-surrogate range, the following index is less

     * than the length of this sequence, and the

     * {@code char} value at the following index is in the

     * low-surrogate range, then the supplementary code point

     * corresponding to this surrogate pair is returned. Otherwise,

     * the {@code char} value at the given index is returned.

     *

     * @param      index the index to the {@code char} values

     * @return     the code point value of the character at the

     *             {@code index}

     * @throws     IndexOutOfBoundsException  if the {@code index}

     *             argument is negative or not less than the length of this

     *             sequence.

     */

    public int codePointAt(int index) {

        int count = this.count;

        byte[] value = this.value;

        checkIndex(index, count);

        if (isLatin1()) {

            return value[index] & 0xff;

        }

        return StringUTF16.codePointAtSB(value, index, count);

    }

    /**

     * Returns the character (Unicode code point) before the specified

     * index. The index refers to {@code char} values

     * (Unicode code units) and ranges from {@code 1} to {@link

     * #length()}.

     *

     * <p> If the {@code char} value at {@code (index - 1)}

     * is in the low-surrogate range, {@code (index - 2)} is not

     * negative, and the {@code char} value at {@code (index -

     * 2)} is in the high-surrogate range, then the

     * supplementary code point value of the surrogate pair is

     * returned. If the {@code char} value at {@code index -

     * 1} is an unpaired low-surrogate or a high-surrogate, the

     * surrogate value is returned.

     *

     * @param     index the index following the code point that should be returned

     * @return    the Unicode code point value before the given index.

     * @throws    IndexOutOfBoundsException if the {@code index}

     *            argument is less than 1 or greater than the length

     *            of this sequence.

     */

    public int codePointBefore(int index) {

        int i = index - 1;

        if (i < 0 || i >= count) {

            throw new StringIndexOutOfBoundsException(index);

        }

        if (isLatin1()) {

            return value[i] & 0xff;

        }

        return StringUTF16.codePointBeforeSB(value, index);

    }

    /**

     * Returns the number of Unicode code points in the specified text

     * range of this sequence. The text range begins at the specified

     * {@code beginIndex} and extends to the {@code char} at

     * index {@code endIndex - 1}. Thus the length (in

     * {@code char}s) of the text range is

     * {@code endIndex-beginIndex}. Unpaired surrogates within

     * this sequence count as one code point each.

     *

     * @param beginIndex the index to the first {@code char} of

     * the text range.

     * @param endIndex the index after the last {@code char} of

     * the text range.

     * @return the number of Unicode code points in the specified text

     * range

     * @throws    IndexOutOfBoundsException if the

     * {@code beginIndex} is negative, or {@code endIndex}

     * is larger than the length of this sequence, or

     * {@code beginIndex} is larger than {@code endIndex}.

     */

    public int codePointCount(int beginIndex, int endIndex) {

        if (beginIndex < 0 || endIndex > count || beginIndex > endIndex) {

            throw new IndexOutOfBoundsException();

        }

        if (isLatin1()) {

            return endIndex - beginIndex;

        }

        return StringUTF16.codePointCountSB(value, beginIndex, endIndex);

    }

    /**

     * Returns the index within this sequence that is offset from the

     * given {@code index} by {@code codePointOffset} code

     * points. Unpaired surrogates within the text range given by

     * {@code index} and {@code codePointOffset} count as

     * one code point each.

     *

     * @param index the index to be offset

     * @param codePointOffset the offset in code points

     * @return the index within this sequence

     * @throws    IndexOutOfBoundsException if {@code index}

     *   is negative or larger then the length of this sequence,

     *   or if {@code codePointOffset} is positive and the subsequence

     *   starting with {@code index} has fewer than

     *   {@code codePointOffset} code points,

     *   or if {@code codePointOffset} is negative and the subsequence

     *   before {@code index} has fewer than the absolute value of

     *   {@code codePointOffset} code points.

     */

    public int offsetByCodePoints(int index, int codePointOffset) {

        if (index < 0 || index > count) {

            throw new IndexOutOfBoundsException();

        }

        return Character.offsetByCodePoints(this,

                                            index, codePointOffset);

    }

    /**

     * Characters are copied from this sequence into the

     * destination character array {@code dst}. The first character to

     * be copied is at index {@code srcBegin}; the last character to

     * be copied is at index {@code srcEnd-1}. The total number of

     * characters to be copied is {@code srcEnd-srcBegin}. The

     * characters are copied into the subarray of {@code dst} starting

     * at index {@code dstBegin} and ending at index:

     * <pre>{@code

     * dstbegin + (srcEnd-srcBegin) - 1

     * }</pre>