Copyright 2018 Netflix, Inc.
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.
/**
 * Copyright 2018 Netflix, Inc.
 *
 * 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 com.netflix.concurrency.limits.limiter;

import com.netflix.concurrency.limits.MetricIds;
import com.netflix.concurrency.limits.MetricRegistry;

import java.util.Optional;

public class SimpleLimiter<ContextT> extends AbstractLimiter<ContextT> {
    public static class Builder extends AbstractLimiter.Builder<Builder> {
        public <ContextT> SimpleLimiter<ContextT> build() {
            return new SimpleLimiter<>(this);
        }

        @Override
        protected Builder self() {
            return this;
        }
    }

    public static Builder newBuilder() {
        return new Builder();
    }

    private final MetricRegistry.SampleListener inflightDistribution;

    public SimpleLimiter(AbstractLimiter.Builder<?> builder) {
        super(builder);

        this.inflightDistribution = builder.registry.distribution(MetricIds.INFLIGHT_NAME);
    }

    @Override
    public Optional<Listener> acquire(ContextT context) {
        int currentInFlight = getInflight();
        inflightDistribution.addSample(currentInFlight);
        if (currentInFlight >= getLimit()) {
            return createRejectedListener();
        }
        return Optional.of(createListener());
    }
}