/*
 * Copyright (c) 2003, 2013, 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;


/**
 * A mutable sequence of characters.  This class provides an API compatible
 * with {@code StringBuilder}, but with some additional constraints:
 * <ul>
 * <li>mutating methods can only be invoked in the same thread that constructed
 * the instance. Attempts to invoke them in other threads throw
 * {@code IllegalStateException}
 * </li>
 * <li>once {@link #toString()} has been called (in constructing thread),
 * no mutating methods can be invoked any more, not even in constructing thread.
 * Attempts to invoke them throw {@code IllegalStateException}
 * </li>
 * </ul>
 * <p>This enables optimization where the {@code String} constructed
 * as the final act can reference the character array that was used for building
 * and no additional copying is needed. This optimization is only effective if
 * the {@link #length()} == {@link #capacity()} when {@code toString()} is called.
 *
 * @see StringBuilder
 * @since 1.9
 */
public final class ThreadLocalStringBuilder
    extends AbstractStringBuilder
    implements java.io.Serializable, CharSequence
{
    /** use serialVersionUID for interoperability */
    static final long serialVersionUID = 1L;

    /** the construction thread until toString() is called, then the String */
    private transient Object constructionThreadOrString;

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

    /**
     * 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 ThreadLocalStringBuilder(int capacity) {
        super(capacity);
        constructionThreadOrString = Thread.currentThread();
    }

    /**
     * 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 ThreadLocalStringBuilder(String str) {
        super(str.length() + 16);
        constructionThreadOrString = Thread.currentThread();
        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 ThreadLocalStringBuilder(CharSequence seq) {
        this(seq.length() + 16);
        append(seq);
    }

    /**
     * @throws IllegalStateException if not invoked in thread that constructed
     * this instance or if toString() has already been called.
     */
    private void checkThread() {
        Object o = constructionThreadOrString;
        if (o != Thread.currentThread()) {
            throw new IllegalStateException((o instanceof String)
                ? "toString() has already been called"
                : "Illegal mutating thread"
            );
        }
    }

    /**
     * @throws IllegalStateException if called from non-constructing thread or
     *         {@code toString()} has already been called
     */
    @Override
    public ThreadLocalStringBuilder append(Object obj) {
        checkThread();
        return append(String.valueOf(obj));
    }

    /**
     * @throws IllegalStateException if called from non-constructing thread or
     *         {@code toString()} has already been called
     */
    @Override
    public ThreadLocalStringBuilder append(String str) {
        checkThread();
        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.
     * @throws IllegalStateException if called from non-constructing thread or
     *         {@code toString()} has already been called
     */
    @Override
    public ThreadLocalStringBuilder append(StringBuffer sb) {
        checkThread();
        super.append(sb);
        return this;
    }

    /**
     * @throws IllegalStateException if called from non-constructing thread or
     *         {@code toString()} has already been called
     */
    @Override
    public ThreadLocalStringBuilder append(CharSequence s) {
        checkThread();
        super.append(s);
        return this;
    }

    /**
     * @throws     IndexOutOfBoundsException {@inheritDoc}
     * @throws IllegalStateException if called from non-constructing thread or
     *         {@code toString()} has already been called
     */
    @Override
    public ThreadLocalStringBuilder append(CharSequence s, int start, int end) {
        checkThread();
        super.append(s, start, end);
        return this;
    }

    /**
     * @throws IllegalStateException if called from non-constructing thread or
     *         {@code toString()} has already been called
     */
    @Override
    public ThreadLocalStringBuilder append(char[] str) {
        checkThread();
        super.append(str);
        return this;
    }

    /**
     * @throws IndexOutOfBoundsException {@inheritDoc}
     * @throws IllegalStateException if called from non-constructing thread or
     *         {@code toString()} has already been called
     */
    @Override
    public ThreadLocalStringBuilder append(char[] str, int offset, int len) {
        checkThread();
        super.append(str, offset, len);
        return this;
    }

    /**
     * @throws IllegalStateException if called from non-constructing thread or
     *         {@code toString()} has already been called
     */
    @Override
    public ThreadLocalStringBuilder append(boolean b) {
        checkThread();
        super.append(b);
        return this;
    }

    /**
     * @throws IllegalStateException if called from non-constructing thread or
     *         {@code toString()} has already been called
     */
    @Override
    public ThreadLocalStringBuilder append(char c) {
        checkThread();
        super.append(c);
        return this;
    }

    /**
     * @throws IllegalStateException if called from non-constructing thread or
     *         {@code toString()} has already been called
     */
    @Override
    public ThreadLocalStringBuilder append(int i) {
        checkThread();
        super.append(i);
        return this;
    }

    /**
     * @throws IllegalStateException if called from non-constructing thread or
     *         {@code toString()} has already been called
     */
    @Override
    public ThreadLocalStringBuilder append(long lng) {
        checkThread();
        super.append(lng);
        return this;
    }

    /**
     * @throws IllegalStateException if called from non-constructing thread or
     *         {@code toString()} has already been called
     */
    @Override
    public ThreadLocalStringBuilder append(float f) {
        checkThread();
        super.append(f);
        return this;
    }

    /**
     * @throws IllegalStateException if called from non-constructing thread or
     *         {@code toString()} has already been called
     */
    @Override
    public ThreadLocalStringBuilder append(double d) {
        checkThread();
        super.append(d);
        return this;
    }

    /**
     * @throws IllegalStateException if called from non-constructing thread or
     *         {@code toString()} has already been called
     * @since 1.5
     */
    @Override
    public ThreadLocalStringBuilder appendCodePoint(int codePoint) {
        checkThread();
        super.appendCodePoint(codePoint);
        return this;
    }

    /**
     * @throws StringIndexOutOfBoundsException {@inheritDoc}
     * @throws IllegalStateException if called from non-constructing thread or
     *         {@code toString()} has already been called
     */
    @Override
    public ThreadLocalStringBuilder delete(int start, int end) {
        checkThread();
        super.delete(start, end);
        return this;
    }

    /**
     * @throws StringIndexOutOfBoundsException {@inheritDoc}
     * @throws IllegalStateException if called from non-constructing thread or
     *         {@code toString()} has already been called
     */
    @Override
    public ThreadLocalStringBuilder deleteCharAt(int index) {
        checkThread();
        super.deleteCharAt(index);
        return this;
    }

    /**
     * @throws StringIndexOutOfBoundsException {@inheritDoc}
     * @throws IllegalStateException if called from non-constructing thread or
     *         {@code toString()} has already been called
     */
    @Override
    public ThreadLocalStringBuilder replace(int start, int end, String str) {
        checkThread();
        super.replace(start, end, str);
        return this;
    }

    /**
     * @throws StringIndexOutOfBoundsException {@inheritDoc}
     * @throws IllegalStateException if called from non-constructing thread or
     *         {@code toString()} has already been called
     */
    @Override
    public ThreadLocalStringBuilder insert(int index, char[] str, int offset,
                                int len)
    {
        checkThread();
        super.insert(index, str, offset, len);
        return this;
    }

    /**
     * @throws StringIndexOutOfBoundsException {@inheritDoc}
     * @throws IllegalStateException if called from non-constructing thread or
     *         {@code toString()} has already been called
     */
    @Override
    public ThreadLocalStringBuilder insert(int offset, Object obj) {
        checkThread();
        super.insert(offset, obj);
        return this;
    }

    /**
     * @throws StringIndexOutOfBoundsException {@inheritDoc}
     * @throws IllegalStateException if called from non-constructing thread or
     *         {@code toString()} has already been called
     */
    @Override
    public ThreadLocalStringBuilder insert(int offset, String str) {
        checkThread();
        super.insert(offset, str);
        return this;
    }

    /**
     * @throws StringIndexOutOfBoundsException {@inheritDoc}
     * @throws IllegalStateException if called from non-constructing thread or
     *         {@code toString()} has already been called
     */
    @Override
    public ThreadLocalStringBuilder insert(int offset, char[] str) {
        checkThread();
        super.insert(offset, str);
        return this;
    }

    /**
     * @throws IndexOutOfBoundsException {@inheritDoc}
     * @throws IllegalStateException if called from non-constructing thread or
     *         {@code toString()} has already been called
     */
    @Override
    public ThreadLocalStringBuilder insert(int dstOffset, CharSequence s) {
        checkThread();
        super.insert(dstOffset, s);
        return this;
    }

    /**
     * @throws IndexOutOfBoundsException {@inheritDoc}
     * @throws IllegalStateException if called from non-constructing thread or
     *         {@code toString()} has already been called
     */
    @Override
    public ThreadLocalStringBuilder insert(int dstOffset, CharSequence s,
                                int start, int end)
    {
        checkThread();
        super.insert(dstOffset, s, start, end);
        return this;
    }

    /**
     * @throws StringIndexOutOfBoundsException {@inheritDoc}
     * @throws IllegalStateException if called from non-constructing thread or
     *         {@code toString()} has already been called
     */
    @Override
    public ThreadLocalStringBuilder insert(int offset, boolean b) {
        checkThread();
        super.insert(offset, b);
        return this;
    }

    /**
     * @throws IndexOutOfBoundsException {@inheritDoc}
     * @throws IllegalStateException if called from non-constructing thread or
     *         {@code toString()} has already been called
     */
    @Override
    public ThreadLocalStringBuilder insert(int offset, char c) {
        checkThread();
        super.insert(offset, c);
        return this;
    }

    /**
     * @throws StringIndexOutOfBoundsException {@inheritDoc}
     * @throws IllegalStateException if called from non-constructing thread or
     *         {@code toString()} has already been called
     */
    @Override
    public ThreadLocalStringBuilder insert(int offset, int i) {
        checkThread();
        super.insert(offset, i);
        return this;
    }

    /**
     * @throws StringIndexOutOfBoundsException {@inheritDoc}
     * @throws IllegalStateException if called from non-constructing thread or
     *         {@code toString()} has already been called
     */
    @Override
    public ThreadLocalStringBuilder insert(int offset, long l) {
        checkThread();
        super.insert(offset, l);
        return this;
    }

    /**
     * @throws StringIndexOutOfBoundsException {@inheritDoc}
     * @throws IllegalStateException if called from non-constructing thread or
     *         {@code toString()} has already been called
     */
    @Override
    public ThreadLocalStringBuilder insert(int offset, float f) {
        checkThread();
        super.insert(offset, f);
        return this;
    }

    /**
     * @throws StringIndexOutOfBoundsException {@inheritDoc}
     * @throws IllegalStateException if called from non-constructing thread or
     *         {@code toString()} has already been called
     */
    @Override
    public ThreadLocalStringBuilder insert(int offset, double d) {
        checkThread();
        super.insert(offset, d);
        return this;
    }

    /**
     * @throws IllegalStateException if called from non-constructing thread or
     *         {@code toString()} has already been called
     */
    @Override
    public ThreadLocalStringBuilder reverse() {
        checkThread();
        super.reverse();
        return this;
    }

    /**
     * @throws IllegalStateException if called from non-constructing thread or
     *         {@code toString()} has already been called
     */
    @Override
    public void ensureCapacity(int minimumCapacity) {
        checkThread();
        super.ensureCapacity(minimumCapacity);
    }

    /**
     * @throws IllegalStateException if called from non-constructing thread or
     *         {@code toString()} has already been called
     */
    @Override
    public void trimToSize() {
        checkThread();
        super.trimToSize();
    }

    /**
     * @throws IllegalStateException if called from non-constructing thread or
     *         {@code toString()} has already been called
     */
    @Override
    public void setLength(int newLength) {
        checkThread();
        super.setLength(newLength);
    }

    /**
     * @throws IllegalStateException if called from non-constructing thread or
     *         {@code toString()} has already been called
     */
    @Override
    public void setCharAt(int index, char ch) {
        checkThread();
        super.setCharAt(index, ch);
    }

    /**
     * @throws IllegalStateException if called from non-constructing thread
     *         and {@code toString()} has not been called yet
     */
    @Override
    public String toString() {
        Object o = constructionThreadOrString;
        if (o == Thread.currentThread()) {
            String s = (value.length == count)
                ? new String(value, true) // share the array if of correct length
                : new String(value, 0, count); // don't share the array otherwise
            constructionThreadOrString = s;
            return s;
        }
        if (o instanceof String) { // allow multiple calls to toString()
            return (String) o;
        }
        throw new IllegalStateException("Illegal invoking thread");
    }

    /**
     * Save the state of the {@code StringBuilder} instance to a stream
     * (that is, serialize it).
     *
     * @serialData the number of characters currently stored in the string
     *             builder ({@code int}), followed by the characters in the
     *             string builder ({@code char[]}).   The length of the
     *             {@code char} array may be greater than the number of
     *             characters currently stored in the string builder, in which
     *             case extra characters are ignored.
     */
    private void writeObject(java.io.ObjectOutputStream s)
        throws java.io.IOException {
        s.defaultWriteObject();
        s.writeInt(count);
        s.writeObject(value);
    }

    /**
     * readObject is called to restore the state of the ThreadLocalStringBuilder
     * from a stream.
     */
    private void readObject(java.io.ObjectInputStream s)
        throws java.io.IOException, ClassNotFoundException {
        s.defaultReadObject();
        count = s.readInt();
        value = (char[]) s.readObject();
        constructionThreadOrString = Thread.currentThread();
    }
}