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Java streaming client that provides easy-to-use client APIs to connect and subscribe to QuoteMedia's market data streaming services. https://quotemedia.com/
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package com.quotemedia.streamer.client.impl;

import com.fasterxml.jackson.databind.ObjectMapper;
import com.quotemedia.streamer.messages.Encodings;
import com.quotemedia.streamer.messages.MimeTypes;
import com.quotemedia.streamer.messages.control.BaseResponse;
import com.quotemedia.streamer.messages.control.CtrlMessage;
import com.quotemedia.streamer.messages.qmci.QmciWireformat;
import com.quotemedia.streamer.messages.smessage.SMessage;
import org.apache.commons.codec.binary.Base64;

import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.nio.ByteBuffer;
import java.util.HashMap;
import java.util.Map;

import static com.google.common.base.Preconditions.checkNotNull;

public final class TextPayloadDecoder implements PayloadDecoder {
    private final QmciMessageFactory qmci;
    private final ObjectMapper json;
    private final String textencoding;
    private final Map decoders;
    private final Map readers;

    public TextPayloadDecoder(final QmciMessageFactory qmci, final ObjectMapper json) {
        checkNotNull(qmci);
        checkNotNull(json);

        this.qmci = qmci;
        this.json = json;
        this.textencoding = "UTF-8"; // TODO make configurable

        this.decoders = new HashMap<>();
        this.decoders.put(Encodings.NONE_CHAR, new Decode() {
            @Override
            public byte[] decode(final String text) throws UnsupportedEncodingException {
                return text != null ? text.getBytes(textencoding) : null;
            }
        });
        this.decoders.put(Encodings.BASE64_CHAR, new Decode() {
            @Override
            public byte[] decode(final String text) throws UnsupportedEncodingException {
                return text != null ? Base64.decodeBase64(text) : null;
            }
        });

        this.readers = new HashMap<>();
        this.readers.put(MimeTypes.JSON_CHAR, new Read() {
            @Override
            public Object read(final byte[] bytes) throws IOException {
                return bytes != null ? json.readValue(bytes, CtrlMessage.class) : null;
            }
        });
        this.readers.put(MimeTypes.QMCI_CHAR, new Read() {
            @Override
            public Object read(final byte[] bytes) throws IOException {
                return bytes != null ? qmci.create(ByteBuffer.wrap(bytes).order(QmciWireformat.BYTE_ORDER)) : null;
            }
        });
    }

    /**
     * Decodes message payload into an object. If no decoder for payload encoding, or reader for payload mime-type are
     * available {@code null} is returned. This makes backward compatibility maintenance easier.
     * Additional encodings or mime-types sent from server to client will simply be ignored.
     *
     * @param in message to decode
     * @return the decoded object or {@code null} if encoding or mime-type is not supported
     * @throws IOException if something goes wrong during decoding
     */
    @Override
    public final Object decode(final SMessage in) throws IOException {
        if (in == null || in.payload() == null) {
            return null;
        }
        final Decode d = this.decoders.get(in.encoding());
        if (d == null) {
            return null;
        }
        final Read read = this.readers.get(in.mimetype());
        if (read == null) {
            return null;
        }
        final Object decoded = read.read(d.decode(in.payload()));
        if (decoded instanceof BaseResponse) { // @remove 1.0.6
            ((BaseResponse) decoded).setRequestId(in.id());
        }
        return decoded;
    }

    private interface Decode {
        byte[] decode(final String payload) throws UnsupportedEncodingException;
    }

    private interface Read {
        Object read(final byte[] bytes) throws IOException;
    }
}