/*
 * Copyright (c) 2003, 2016, 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 java.util.stream.IntStream;

/**
 * A mutable sequence of characters. This class provides an API compatible
 * with {@code StringBuilder}, with no need for synchronization. It allows
 * building at most one {@code String} and only in a single thread.
 * If any of the methods of this class is invoked
 * in a thread distinct from the thread that constructed the string builder,
 * an {@code IllegalStateException} is thrown.
 * If any of the methods of this class is invoked after the {@link #toString()}
 * method has already been invoked to construct a {@code String},
 * an {@code IllegalStateException} is thrown.
 * These constraints allow this class to be more optimal than {@code StringBuilder}
 * in case initial capacity of the builder is estimated to the exact
 * length of the built String as no defensive copying of internal array is required.
 *
 * @since 9
 */
public final class OneShotStringBuilder
    extends AbstractStringBuilder
    implements CharSequence
{

    /**
     * Constructs a string builder with no characters in it and an
     * initial capacity of 16 characters.
     */
    public OneShotStringBuilder() {
        super(16);
    }

    /**
     * Constructs a string builder with no characters in it and an
     * initial capacity specified by the {@code capacity} argument.
     *
     * @param      capacity  the initial capacity.
     * @throws     NegativeArraySizeException  if the {@code capacity}
     *               argument is less than {@code 0}.
     */
    public OneShotStringBuilder(int capacity) {
        super(capacity);
    }

    /**
     * Constructs a string builder initialized to the contents of the
     * specified string. The initial capacity of the string builder is
     * {@code 16} plus the length of the string argument.
     *
     * @param   str   the initial contents of the buffer.
     */
    public OneShotStringBuilder(String str) {
        super(str.length() + 16);
        append(str);
    }

    /**
     * Constructs a string builder 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.
     */
    public OneShotStringBuilder(CharSequence seq) {
        this(seq.length() + 16);
        append(seq);
    }

    @Override
    public OneShotStringBuilder append(Object obj) {
        return append(String.valueOf(obj));
    }

    @Override
    public OneShotStringBuilder append(String str) {
        checkUse();
        super.append(str);
        return this;
    }

    /**
     * Appends the specified {@code StringBuffer} to this sequence.
     * <p>
     * The characters of the {@code StringBuffer} argument are appended,
     * in order, to this sequence, increasing the
     * length of this sequence by the length of the argument.
     * If {@code sb} is {@code null}, then the four characters
     * {@code "null"} are appended to this sequence.
     * <p>
     * Let <i>n</i> be the length of this character sequence just prior to
     * execution of the {@code append} method. Then the character at index
     * <i>k</i> in the new character sequence is equal to the character at
     * index <i>k</i> in the old character sequence, if <i>k</i> is less than
     * <i>n</i>; otherwise, it is equal to the character at index <i>k-n</i>
     * in the argument {@code sb}.
     *
     * @param   sb   the {@code StringBuffer} to append.
     * @return  a reference to this object.
     */
    public OneShotStringBuilder append(StringBuffer sb) {
        checkUse();
        super.append(sb);
        return this;
    }

    @Override
    public OneShotStringBuilder append(CharSequence s) {
        checkUse();
        super.append(s);
        return this;
    }

    /**
     * @throws     IndexOutOfBoundsException {@inheritDoc}
     */
    @Override
    public OneShotStringBuilder append(CharSequence s, int start, int end) {
        checkUse();
        super.append(s, start, end);
        return this;
    }

    @Override
    public OneShotStringBuilder append(char[] str) {
        checkUse();
        super.append(str);
        return this;
    }

    /**
     * @throws IndexOutOfBoundsException {@inheritDoc}
     */
    @Override
    public OneShotStringBuilder append(char[] str, int offset, int len) {
        checkUse();
        super.append(str, offset, len);
        return this;
    }

    @Override
    public OneShotStringBuilder append(boolean b) {
        checkUse();
        super.append(b);
        return this;
    }

    @Override
    public OneShotStringBuilder append(char c) {
        checkUse();
        super.append(c);
        return this;
    }

    @Override
    public OneShotStringBuilder append(int i) {
        checkUse();
        super.append(i);
        return this;
    }

    @Override
    public OneShotStringBuilder append(long lng) {
        checkUse();
        super.append(lng);
        return this;
    }

    @Override
    public OneShotStringBuilder append(float f) {
        checkUse();
        super.append(f);
        return this;
    }

    @Override
    public OneShotStringBuilder append(double d) {
        checkUse();
        super.append(d);
        return this;
    }

    @Override
    public OneShotStringBuilder appendCodePoint(int codePoint) {
        checkUse();
        super.appendCodePoint(codePoint);
        return this;
    }

    /**
     * @throws StringIndexOutOfBoundsException {@inheritDoc}
     */
    @Override
    public OneShotStringBuilder delete(int start, int end) {
        checkUse();
        super.delete(start, end);
        return this;
    }

    /**
     * @throws StringIndexOutOfBoundsException {@inheritDoc}
     */
    @Override
    public OneShotStringBuilder deleteCharAt(int index) {
        checkUse();
        super.deleteCharAt(index);
        return this;
    }

    /**
     * @throws StringIndexOutOfBoundsException {@inheritDoc}
     */
    @Override
    public OneShotStringBuilder replace(int start, int end, String str) {
        checkUse();
        super.replace(start, end, str);
        return this;
    }

    /**
     * @throws StringIndexOutOfBoundsException {@inheritDoc}
     */
    @Override
    public OneShotStringBuilder insert(int index, char[] str, int offset,
                                       int len)
    {
        checkUse();
        super.insert(index, str, offset, len);
        return this;
    }

    /**
     * @throws StringIndexOutOfBoundsException {@inheritDoc}
     */
    @Override
    public OneShotStringBuilder insert(int offset, Object obj) {
        checkUse();
        super.insert(offset, obj);
        return this;
    }

    /**
     * @throws StringIndexOutOfBoundsException {@inheritDoc}
     */
    @Override
    public OneShotStringBuilder insert(int offset, String str) {
        checkUse();
        super.insert(offset, str);
        return this;
    }

    /**
     * @throws StringIndexOutOfBoundsException {@inheritDoc}
     */
    @Override
    public OneShotStringBuilder insert(int offset, char[] str) {
        checkUse();
        super.insert(offset, str);
        return this;
    }

    /**
     * @throws IndexOutOfBoundsException {@inheritDoc}
     */
    @Override
    public OneShotStringBuilder insert(int dstOffset, CharSequence s) {
        checkUse();
        super.insert(dstOffset, s);
        return this;
    }

    /**
     * @throws IndexOutOfBoundsException {@inheritDoc}
     */
    @Override
    public OneShotStringBuilder insert(int dstOffset, CharSequence s,
                                       int start, int end)
    {
        checkUse();
        super.insert(dstOffset, s, start, end);
        return this;
    }

    /**
     * @throws StringIndexOutOfBoundsException {@inheritDoc}
     */
    @Override
    public OneShotStringBuilder insert(int offset, boolean b) {
        checkUse();
        super.insert(offset, b);
        return this;
    }

    /**
     * @throws IndexOutOfBoundsException {@inheritDoc}
     */
    @Override
    public OneShotStringBuilder insert(int offset, char c) {
        checkUse();
        super.insert(offset, c);
        return this;
    }

    /**
     * @throws StringIndexOutOfBoundsException {@inheritDoc}
     */
    @Override
    public OneShotStringBuilder insert(int offset, int i) {
        checkUse();
        super.insert(offset, i);
        return this;
    }

    /**
     * @throws StringIndexOutOfBoundsException {@inheritDoc}
     */
    @Override
    public OneShotStringBuilder insert(int offset, long l) {
        checkUse();
        super.insert(offset, l);
        return this;
    }

    /**
     * @throws StringIndexOutOfBoundsException {@inheritDoc}
     */
    @Override
    public OneShotStringBuilder insert(int offset, float f) {
        checkUse();
        super.insert(offset, f);
        return this;
    }

    /**
     * @throws StringIndexOutOfBoundsException {@inheritDoc}
     */
    @Override
    public OneShotStringBuilder insert(int offset, double d) {
        checkUse();
        super.insert(offset, d);
        return this;
    }

    @Override
    public int indexOf(String str) {
        checkUse();
        return super.indexOf(str);
    }

    @Override
    public int indexOf(String str, int fromIndex) {
        checkUse();
        return super.indexOf(str, fromIndex);
    }

    @Override
    public int lastIndexOf(String str) {
        checkUse();
        return super.lastIndexOf(str);
    }

    @Override
    public int lastIndexOf(String str, int fromIndex) {
        checkUse();
        return super.lastIndexOf(str, fromIndex);
    }

    @Override
    public OneShotStringBuilder reverse() {
        checkUse();
        super.reverse();
        return this;
    }

    @Override
    public int length() {
        checkUse();
        return super.length();
    }

    @Override
    public int capacity() {
        checkUse();
        return super.capacity();
    }

    @Override
    public void ensureCapacity(int minimumCapacity) {
        checkUse();
        super.ensureCapacity(minimumCapacity);
    }

    @Override
    public void trimToSize() {
        checkUse();
        super.trimToSize();
    }

    @Override
    public void setLength(int newLength) {
        checkUse();
        super.setLength(newLength);
    }

    @Override
    public char charAt(int index) {
        checkUse();
        return super.charAt(index);
    }

    @Override
    public int codePointAt(int index) {
        checkUse();
        return super.codePointAt(index);
    }

    @Override
    public int codePointBefore(int index) {
        checkUse();
        return super.codePointBefore(index);
    }

    @Override
    public int codePointCount(int beginIndex, int endIndex) {
        checkUse();
        return super.codePointCount(beginIndex, endIndex);
    }

    @Override
    public int offsetByCodePoints(int index, int codePointOffset) {
        checkUse();
        return super.offsetByCodePoints(index, codePointOffset);
    }

    @Override
    public void getChars(int srcBegin, int srcEnd, char[] dst, int dstBegin) {
        checkUse();
        super.getChars(srcBegin, srcEnd, dst, dstBegin);
    }

    @Override
    public void setCharAt(int index, char ch) {
        checkUse();
        super.setCharAt(index, ch);
    }

    @Override
    public String substring(int start) {
        checkUse();
        return super.substring(start);
    }

    @Override
    public CharSequence subSequence(int start, int end) {
        checkUse();
        return super.subSequence(start, end);
    }

    @Override
    public String substring(int start, int end) {
        checkUse();
        return super.substring(start, end);
    }

    @Override
    public IntStream chars() {
        checkUse();
        return super.chars();
    }

    @Override
    public IntStream codePoints() {
        checkUse();
        return super.codePoints();
    }

    @Override
    public String toString() {
        checkUse();
        // take the value array and reset the value to null to make this
        // builder unusable...
        byte[] val = value;
        value = null;
        if (super.length() == super.capacity()) {
            // just pass the array by reference to String constructor if
            // capacity matches desired String length
            return new String(val, coder);
        }
        // else create a copy, don't share the array
        return isLatin1() ? StringLatin1.newString(val, 0, count)
                          : StringUTF16.newString(val, 0, count);
    }

    /**
     * A thread that constructed this instance; all operations are constrained
     * to that thread.
     */
    private final Thread constructingThread = Thread.currentThread();

    private void checkUse() {
        if (constructingThread != Thread.currentThread()) {
            throw new IllegalStateException("Wrong thread");
        }
        if (value == null) {
            throw new IllegalStateException(
                "This builder has already been used once to construct a String");
        }
    }
}