/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you 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 org.apache.sshd.common.session.filters;

import java.nio.ByteBuffer;
import java.nio.IntBuffer;

import org.apache.sshd.common.random.Random;

/**
 * A {@link Random} instance based on {@link java.util.concurrent.ThreadLocalRandom}.
 */
enum ThreadLocalRandom implements Random {

    INSTANCE;

    ThreadLocalRandom() {
        // Nothing
    }

    @Override
    public String getName() {
        return "ThreadLocalRandom";
    }

    @Override
    public void fill(byte[] bytes, int start, int len) {
        java.util.concurrent.ThreadLocalRandom rnd = java.util.concurrent.ThreadLocalRandom.current();
        int n = len / 4;
        if (n > 0) {
            IntBuffer buf = ByteBuffer.wrap(bytes, start, len).asIntBuffer();
            rnd.ints(n).forEach(buf::put);
        }
        int l = len & 3;
        if (l > 0) {
            int x = rnd.nextInt();
            int pos = start + len - 1;
            for (int i = 0; i < l; i++) {
                bytes[pos - i] = (byte) (x & 0xFF);
                x >>= 8;
            }
        }
    }

    @Override
    public int random(int n) {
        return java.util.concurrent.ThreadLocalRandom.current().nextInt(n);
    }
}
