/* Status.java
 *
 * Copyright 2009-2012 Comcast Interactive Media, LLC.
 *
 * 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 org.fishwife.jrugged;

/**
 * Various components in the system need to report their status. This <code>enum</code>
 * standardizes on a set of conventions for reporting this. Each {@link Status} has an
 * integer <code>value</code> which can be compared; higher values represent higher levels
 * of functionality. In addition, each {@link Status} has a {@link String}
 * <code>signal</code> which is either GREEN, YELLOW, or RED.
 * <p>
 * The general notion is that the whole system (or a subsystem) should only report GREEN
 * status (UP) if everything is working as designed. When subsystems start to go down, or
 * the current system stops working, status should drop to either YELLOW (DEGRADED) or RED
 * (DOWN), depending on whether service was still available in some form. For example, if
 * a cache subsystem goes down, we might report a YELLOW status because we can attempt to
 * serve without a cache. However, if a required database goes down, we probably need to
 * report a RED status, unable to serve requests.
 * <p>
 * A "rugged" system should be able to accurately (and responsively) report on its status
 * even if it is unable to perform its main functions. This will assist operators in
 * diagnosing the problem; a hung process tells no tales.
 */
public enum Status {
    /** Unrecoverable: we're basically dead for good. */
    FAILED(-2, "RED"),

    /** Being initialized: not yet ready to serve. */
    INIT(-1, "RED"),

    /** Currently unavailable. */
    DOWN(0, "RED"),

    /** Something's wrong, but we can still serve requests. */
    DEGRADED(1, "YELLOW"),

    /** Everything is operating as expected. */
    UP(2, "GREEN"),

    /**
     * This status was introduced in a prior version of JRugged and so is retained for
     * backwards compatibility, but is specific to
     * {@link org.fishwife.jrugged.CircuitBreaker} states and should not be used.
     */
    @Deprecated BYPASS(3, "GREEN");

    private final int value;
    private final String signal;

    Status(final int value, final String signal) {
        this.value = value;
        this.signal = signal;
    }

    /**
     * Returns the current status as an integer. Higher values are for states of higher
     * functionality/availability.
     */
    public int getValue() {
        return value;
    }

    /**
     * Returns the current GREEN/YELLOW/RED dashboard indicator corresponding to this
     * status.
     */
    public String getSignal() {
        return signal;
    }

    /**
     * Returns whether the status indicates a system that is able to serve requests.
     */
    public boolean isAvailable() {
        return value > 0;
    }
}