/*
 * 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
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 *  https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
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 * 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.
 *
 * Other licenses:
 * -----------------------------------------------------------------------------
 * Commercial licenses for this work are available. These replace the above
 * Apache-2.0 license and offer limited warranties, support, maintenance, and
 * commercial database integrations.
 *
 * For more information, please visit: https://www.jooq.org/legal/licensing
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package org.jooq;

import java.util.Arrays;
import java.util.Collection;
import java.util.stream.Collector;

/**
 * An <code>FunctionalInterface</code> that wraps transactional code.
 * <p>
 * Transactional code should not depend on any captured scope, but use the
 * argument {@link Configuration} passed to the {@link #run(Configuration)}
 * method to derive its transaction context.
 * <p>
 * If transactional code needs to depend on captured scope ("context"), then
 * {@link ContextTransactionalCallable} is a better fit.
 *
 * @author Lukas Eder
 */
@FunctionalInterface
public interface TransactionalCallable<T> {

    /**
     * Run the transactional code.
     * <p>
     * If this method completes normally, and this is not a nested transaction,
     * then the transaction will be committed. If this method completes with an
     * exception (any {@link Throwable}), then the transaction is rolled back to
     * the beginning of this <code>TransactionalCallable</code>.
     *
     * @param configuration The <code>Configuration</code> in whose context the
     *            transaction is run.
     * @return The outcome of the transaction.
     * @throws Throwable Any exception that will cause a rollback of the code
     *             contained in this transaction. If this is a nested
     *             transaction, the rollback may be performed only to the state
     *             before executing this <code>TransactionalCallable</code>.
     */
    T run(Configuration configuration) throws Throwable;

    /**
     * Wrap a set of nested {@link TransactionalCallable} objects in a single
     * global {@link TransactionalCallable}, returning the last callable's
     * result.
     */
    @SafeVarargs
    static <T> TransactionalCallable<T> of(TransactionalCallable<T>... callables) {
        return of(Arrays.asList(callables));
    }

    /**
     * Wrap a set of nested {@link TransactionalCallable} objects in a single
     * global {@link TransactionalCallable}, returning the last callable's
     * result.
     */
    static <T> TransactionalCallable<T> of(Collection<? extends TransactionalCallable<T>> callables) {
        return configuration -> {
            T result = null;

            for (TransactionalCallable<T> callable : callables)
                result = configuration.dsl().transactionResult(callable);

            return result;
        };
    }

    /**
     * Wrap a set of nested {@link TransactionalCallable} objects in a single
     * global {@link TransactionalCallable}, collecting the callables' results.
     */
    static <T, R> TransactionalCallable<R> of(TransactionalCallable<T>[] callables, Collector<T, ?, R> collector) {
        return of(Arrays.asList(callables), collector);
    }

    /**
     * Wrap a set of nested {@link TransactionalCallable} objects in a single
     * global {@link TransactionalCallable}, collecting the callables' results.
     */
    static <T, R> TransactionalCallable<R> of(Collection<? extends TransactionalCallable<T>> callables, Collector<T, ?, R> collector) {
        return configuration -> callables.stream().map(configuration.dsl()::transactionResult).collect(collector);
    }
}
