/*
 * Copyright 2006-2018 the original author or authors.
 *
 * 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
 *
 *      https://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.springframework.batch.core.job.flow.support;

import org.springframework.batch.core.ExitStatus;
import org.springframework.batch.core.job.flow.State;
import org.springframework.batch.support.PatternMatcher;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.StringUtils;

/**
 * Value object representing a potential transition from one {@link State} to
 * another. The originating State name and the next {@link State} to execute are
 * linked by a pattern for the {@link ExitStatus#getExitCode() exit code} of an
 * execution of the originating State.
 *
 * @author Dave Syer
 * @author Michael Minella
 * @author Mahmoud Ben Hassine
 * @since 2.0
 */
public final class StateTransition {

        private final State state;

        private final String pattern;

        private final String next;

        /**
         * @return the pattern the {@link ExitStatus#getExitCode()} will be compared against.
         */
        public String getPattern() {
                return this.pattern;
        }

        /**
         * Create a new end state {@link StateTransition} specification. This
         * transition explicitly goes unconditionally to an end state (i.e. no more
         * executions).
         *
         * @param state the {@link State} used to generate the outcome for this
         * transition
         * @return {@link StateTransition} that was created.
         */
        public static StateTransition createEndStateTransition(State state) {
                return createStateTransition(state, null, null);
        }

        /**
         * Create a new end state {@link StateTransition} specification. This
         * transition explicitly goes to an end state (i.e. no more processing) if
         * the outcome matches the pattern.
         *
         * @param state the {@link State} used to generate the outcome for this
         * transition
         * @param pattern the pattern to match in the exit status of the
         * {@link State}
         * @return {@link StateTransition} that was created.
         */
        public static StateTransition createEndStateTransition(State state, String pattern) {
                return createStateTransition(state, pattern, null);
        }

        /**
         * Convenience method to switch the origin and destination of a transition,
         * creating a new instance.
         *
         * @param stateTransition an existing state transition
         * @param state the new state for the origin
         * @param next the new name for the destination
         *
         * @return {@link StateTransition} that was created.
         */
        public static StateTransition switchOriginAndDestination(StateTransition stateTransition, State state, String next) {
                return createStateTransition(state, stateTransition.pattern, next);
        }

        /**
         * Create a new state {@link StateTransition} specification with a wildcard
         * pattern that matches all outcomes.
         *
         * @param state the {@link State} used to generate the outcome for this
         * transition
         * @param next the name of the next {@link State} to execute
         * @return {@link StateTransition} that was created.
         */
        public static StateTransition createStateTransition(State state, String next) {
                return createStateTransition(state, null, next);
        }

        /**
         * Create a new {@link StateTransition} specification from one {@link State}
         * to another (by name).
         *
         * @param state the {@link State} used to generate the outcome for this
         * transition
         * @param pattern the pattern to match in the exit status of the
         * {@link State} (can be {@code null})
         * @param next the name of the next {@link State} to execute (can be {@code null})
         * @return {@link StateTransition} that was created.
         */
        public static StateTransition createStateTransition(State state, @Nullable String pattern, @Nullable String next) {
                return new StateTransition(state, pattern, next);
        }

        private StateTransition(State state, @Nullable String pattern, @Nullable String next) {
                super();
                if (!StringUtils.hasText(pattern)) {
                        this.pattern = "*";
                }
                else {
                        this.pattern = pattern;
                }

                Assert.notNull(state, "A state is required for a StateTransition");
                if (state.isEndState() && StringUtils.hasText(next)) {
                        throw new IllegalStateException("End state cannot have next: " + state);
                }

                this.next = next;
                this.state = state;
        }

        /**
         * Public getter for the State.
         * @return the State
         */
        public State getState() {
                return state;
        }

        /**
         * Public getter for the next State name.
         * @return the next
         */
        public String getNext() {
                return next;
        }

        /**
         * Check if the provided status matches the pattern, signalling that the
         * next State should be executed.
         *
         * @param status the status to compare
         * @return true if the pattern matches this status
         */
        public boolean matches(String status) {
                return PatternMatcher.match(pattern, status);
        }

        /**
         * Check for a special next State signalling the end of a job.
         *
         * @return true if this transition goes nowhere (there is no next)
         */
        public boolean isEnd() {
                return next == null;
        }

        /*
         * (non-Javadoc)
         *
         * @see java.lang.Object#toString()
         */
        @Override
        public String toString() {
                return String.format("StateTransition: [state=%s, pattern=%s, next=%s]",
                                state == null ? null : state.getName(), pattern, next);
        }

}