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A minimalistic, GC-free, stream-oriented JSON parser and generator.
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/**
 * MIT License
 *
 * Copyright (c) 2018-2024 Anatoly Gudkov and others.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */
package io.github.green4j.jelly;

import java.io.IOException;

public final class AppendableWriter implements BufferingWriter {
    private final Frame frame = new Frame() {
        @Override
        public void setCharAt(final int index, final char c) {
            frameArray[index] = c;
        }

        @Override
        public char charAt(final int index) {
            return frameArray[index];
        }

        @Override
        public CharSequence subSequence(final int start, final int end) {
            throw new UnsupportedOperationException();
        }

        @Override
        public int length() {
            return Math.abs(frameSize);
        }

        @Override
        public String toString() {
            return new String(frameArray, 0, length());
        }
    };

    private char[] frameArray = new char[32];
    private int frameSize;

    private T output;

    public AppendableWriter() {
    }

    public AppendableWriter(final T output) {
        set(output);
    }

    public void set(final T output) {
        this.output = output;
    }

    public T output() {
        return output;
    }

    @Override
    public Frame append(final int size) {
        assert size > 0;

        try {
            tryPushFrame();
        } catch (final IOException e) {
            throw new RuntimeException(e);
        }
        makeSureFrameSize(size);
        frameSize = -size;
        return frame;
    }

    @Override
    public void append(final char c) {
        assert output != null;

        try {
            tryPushFrame();
            output.append(c);
        } catch (final IOException e) {
            throw new RuntimeException(e);
        }
    }

    @Override
    public void append(final CharSequence data) {
        assert output != null;

        try {
            tryPushFrame();
            output.append(data);
        } catch (final IOException e) {
            throw new RuntimeException(e);
        }
    }

    @Override
    public void append(final CharSequence data, final int start, final int len) {
        assert output != null;

        try {
            tryPushFrame();
            output.append(data, start, start + len);
        } catch (final IOException e) {
            throw new RuntimeException(e);
        }
    }

    @Override
    public void flush() {
        if (output == null) {
            return;
        }
        try {
            tryPushFrame();
        } catch (final IOException e) {
            throw new RuntimeException(e);
        }
    }

    private void tryPushFrame() throws IOException {
        if (frameSize < 0) {
            output.append(frame);
            frameSize = -frameSize;
        }
    }

    private void makeSureFrameSize(final int roomSize) {
        final int delta = frameArray.length - roomSize;
        if (delta < 0) {
            final int newSize = Math.max(roomSize, frameArray.length) << 1;
            final char[] newArray = new char[newSize];
            frameArray = newArray;
        }
    }

    @Override
    public String toString() {
        if (output == null) {
            return "null";
        }
        return output.toString();
    }
}