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package io.keen.client.android;

import org.json.JSONException;
import org.json.JSONObject;

import java.io.IOException;
import java.io.Reader;
import java.io.StringWriter;
import java.io.Writer;
import java.util.Map;

import io.keen.client.java.KeenJsonHandler;

/**
 * Implementation of the {@link io.keen.client.java.KeenJsonHandler} interface using the built-in
 * Android JSON library ({@link org.json.JSONObject}).
 *
 * @author Kevin Litwack ([email protected])
 * @since 2.0.0
 */
class AndroidJsonHandler implements KeenJsonHandler {

    ///// KeenJsonHandler METHODS /////

    /**
     * {@inheritDoc}
     */
    @Override
    public Map readJson(Reader reader) throws IOException {
        if (reader == null) {
            throw new IllegalArgumentException("Reader must not be null");
        }

        String json = readerToString(reader);
        try {
            JSONObject jsonObject = new JSONObject(json);
            return JsonHelper.toMap(jsonObject);
        } catch (JSONException e) {
            throw new IOException(e);
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void writeJson(Writer writer, Map value) throws IOException {
        if (writer == null) {
            throw new IllegalArgumentException("Reader must not be null");
        }

        JSONObject jsonObject = new JSONObject(value);
        writer.write(jsonObject.toString());
        writer.close();
    }

    ///// PRIVATE CONSTANTS /////

    /**
     * The size of the buffer to use when copying a reader to a string.
     */
    private static final int COPY_BUFFER_SIZE = 4 * 1024;

    ///// PRIVATE METHODS /////

    /**
     * Converts a Reader to a String by copying the Reader's contents into a StringWriter via a
     * buffer.
     *
     * @param reader The Reader from which to extract a String.
     * @return The String contained in the Reader.
     * @throws IOException If there is an error reading from the input Reader.
     */
    private static String readerToString(Reader reader) throws IOException {
        StringWriter writer = new StringWriter();
        try {
            char[] buffer = new char[COPY_BUFFER_SIZE];
            while (true) {
                int bytesRead = reader.read(buffer);
                if (bytesRead == -1) {
                    break;
                } else {
                    writer.write(buffer, 0, bytesRead);
                }
            }
            return writer.toString();
        } finally {
            reader.close();
        }
    }

}