Statement.java

/**
 * Powerunit - A JDK1.8 test framework
 * Copyright (C) 2014 Mathieu Boretti.
 *
 * This file is part of Powerunit
 *
 * Powerunit is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Powerunit is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Powerunit. If not, see <http://www.gnu.org/licenses/>.
 */
package ch.powerunit;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Objects;
import java.util.function.Consumer;

import ch.powerunit.exception.InternalError;

/**
 * Definition of a statement (piece of code that can thrown Throwable).
 * <p>
 * A statement can be used inside test (to isolate a code that must thrown an
 * exception) and are used internally by the framework to compose and execute
 * test sequence element.
 *
 * @author borettim
 * @param <P>
 *            The type of the parameter
 * @param <T>
 *            the exception type
 */
@FunctionalInterface
public interface Statement<P, T extends Throwable> {

    /**
     * Executable code.
     * 
     * @param parameter
     *            A parameter for the statement
     * @throws Throwable
     *             in case of error.
     */
    void run(P parameter) throws Throwable;// should be T, but T seem to produce
                                            // a bug in the compiler

    /**
     * Used to provide a name (for internal use purpose).
     * 
     * @return the string, by default null.
     * @since 0.1.0
     */
    default String getName() {
        return null;
    }

    /**
     * Aggregate this statement and then the following. The second statement is
     * done, even in case of exception in the first one.
     * 
     * @param after
     *            the next statement
     * @return the new statement
     */
    default Statement<P, T> andThenAlways(Statement<P, T> after) {
        Objects.requireNonNull(after);
        return (p) -> {
            try {
                run(p);
            } finally {
                after.run(p);
            }
        };
    }

    /**
     * Aggregate this statement and then the following. The second statement is
     * done except in case of exception in the first one.
     * 
     * @param after
     *            the next statement
     * @return the new statement
     */
    default Statement<P, T> andThenOnlySuccess(Statement<P, T> after) {
        Objects.requireNonNull(after);
        return (p) -> {
            run(p);
            after.run(p);
        };
    }

    /**
     * Build a around statement (do something, then something others, and after
     * one a third statement, event in case of exception.
     * 
     * @param internal
     *            the internal part
     * @param before
     *            the first statement
     * @param after
     *            the last statement, done event in case of exception.
     * @return the new statement.
     * @param <P>
     *            The type of the parameter
     * @param <T>
     *            the exception type
     */
    static <P, T extends Throwable> Statement<P, T> around(
            Statement<P, T> internal, Statement<P, T> before,
            Statement<P, T> after) {
        Objects.requireNonNull(internal);
        Objects.requireNonNull(before);
        Objects.requireNonNull(after);
        return before.andThenOnlySuccess(internal).andThenAlways(after);
    }

    /**
     * Build a statement based on a method-
     * 
     * @param target
     *            the target object
     * @param method
     *            the method
     * @return the new statement.
     * @param <P>
     *            The type of the parameter
     * @param <T>
     *            the exception type
     */
    static <P, T extends Throwable> Statement<P, T> reflectionMethod(
            Object target, Method method) {
        Objects.requireNonNull(target);
        Objects.requireNonNull(method);
        return new Statement<P, T>() {

            @Override
            public void run(P parameter) throws Throwable {
                try {
                    method.invoke(target);
                } catch (InvocationTargetException e) {
                    throw e.getCause();
                } catch (IllegalAccessException | IllegalArgumentException e) {
                    throw new InternalError("Unexpected error "
                            + e.getMessage(), e);
                }
            }

            @Override
            public String getName() {
                return method.getName();
            }
        };
    }

    /**
     * Build a statement based on a method-
     * 
     * @param method
     *            the method
     * @param param
     *            the param
     * @return the new statement.
     * @param <P>
     *            The type of the parameter
     * @param <T>
     *            the exception type
     * @since 0.2.0
     */
    static <P, T extends Throwable> Statement<P, T> reflectionMethod(
            Consumer<Object> method, Object param) {
        Objects.requireNonNull(method);
        return new Statement<P, T>() {

            @Override
            public void run(P parameter) throws Throwable {
                method.accept(param);
            }

            @Override
            public String getName() {
                return "N/A";
            }
        };
    }

}