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/*
 * 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.trino.execution;

import com.google.common.annotations.VisibleForTesting;

import java.util.function.Supplier;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkState;
import static java.lang.Long.parseLong;
import static java.lang.Math.multiplyExact;
import static java.lang.Math.toIntExact;
import static java.util.Objects.requireNonNull;

// Based on https://github.com/airlift/units/pull/31, but adapted not to be a value class per https://github.com/trinodb/trino/pull/16303#issuecomment-1730146433
public class ThreadCountParser
{
    private static final String PER_CORE_SUFFIX = "C";
    private static final Supplier AVAILABLE_PROCESSORS = Runtime.getRuntime()::availableProcessors;
    public static final ThreadCountParser DEFAULT = new ThreadCountParser(AVAILABLE_PROCESSORS);

    private final Supplier coreCount;

    @VisibleForTesting
    ThreadCountParser(Supplier coreCount)
    {
        this.coreCount = requireNonNull(coreCount, "coreCount is null");
    }

    public int parse(String value)
    {
        int coreCount = this.coreCount.get();
        checkState(coreCount > 0, "coreCount must be positive");

        long threads;
        if (value.endsWith(PER_CORE_SUFFIX)) {
            long multiplier = parseLong(value.substring(0, value.length() - PER_CORE_SUFFIX.length()).trim());
            checkArgument(multiplier > 0, "Thread multiplier cannot be negative");
            threads = multiplyExact(multiplier, coreCount);
        }
        else {
            threads = parseLong(value);
        }

        checkArgument(threads <= Integer.MAX_VALUE, "Thread count is greater than 2^32 - 1");
        checkArgument(0 <= threads, "Thread count cannot be negative");
        return toIntExact(threads);
    }
}