io.nats.client.impl.ListRequestEngine Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of jnats Show documentation

Client library for working with the NATS messaging system.

The newest version!

// Copyright 2020 The NATS Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at:
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package io.nats.client.impl;

import io.nats.client.JetStreamApiException;
import io.nats.client.Message;
import io.nats.client.api.ApiResponse;

import java.nio.charset.StandardCharsets;

import static io.nats.client.support.ApiConstants.*;
import static io.nats.client.support.JsonValueUtils.readInteger;

class ListRequestEngine extends ApiResponse {

    private static final String OFFSET_JSON_START = "{\"offset\":";

    protected int total = Integer.MAX_VALUE; // so always has the first "at least one more"
    protected int limit = 0;
    protected int lastOffset = 0;

    ListRequestEngine() {
        super();
    }

    ListRequestEngine(Message msg) throws JetStreamApiException {
        super(msg);
        if (hasError()) {
            throw new JetStreamApiException(this);
        }
        total = readInteger(jv, TOTAL, -1);
        limit = readInteger(jv, LIMIT, 0);
        lastOffset = readInteger(jv, OFFSET, 0);
    }

    boolean hasMore() {
        return total > nextOffset();
    }

    private byte[] noFilterJson() {
        return (OFFSET_JSON_START + nextOffset() + "}").getBytes(StandardCharsets.UTF_8);
    }

    byte[] internalNextJson() {
        return hasMore() ? noFilterJson() : null;
    }

    byte[] internalNextJson(String fieldName, String filter) {
        if (hasMore()) {
            if (filter == null) {
                return noFilterJson();
            }
            return (OFFSET_JSON_START + nextOffset()
                    + ",\"" + fieldName + "\":\"" + filter + "\"}").getBytes(StandardCharsets.UTF_8);
        }
        return null;
    }

    int nextOffset() {
        return lastOffset + limit;
    }
}