/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.apache.felix.dependencymanager.impl;

import java.util.List;

import org.apache.felix.dependencymanager.Dependency;

/**
 * Encapsulates the current state of the dependencies of a service. A state is
 * basically an immutable value object.
 * 
 * @author <a href="mailto:dev@felix.apache.org">Felix Project Team</a>
 */
public final class State {
    private static final String[] STATES = { "?", "inactive", "waiting for required", "tracking optional", "bound", "waiting for required (instantiated)" };
    private static final int INACTIVE = 1;
    private static final int WAITING_FOR_REQUIRED = 2;
    private static final int TRACKING_OPTIONAL = 3;
    private static final int BOUND = 4;
    private static final int WAITING_FOR_REQUIRED_INSTANTIATED = 5;
    private final List m_deps;
    private final int m_state;
    private String m_stringValue;
    
    /**
     * Creates a new state instance.
     * 
     * @param deps the dependencies that determine the state
     * @param isActive <code>true</code> if the service is active (started)
     */
    public State(List deps, boolean isActive, boolean isInstantiated, boolean isBound /* unused? */) {
        m_deps = deps;
        // only bother calculating dependencies if we're active
        if (isActive) {
            boolean allRequiredAvailable = true;
            boolean keepInstanceAround = isInstantiated;
            for (int i = 0; i < deps.size(); i++) {
                Dependency dep = (Dependency) deps.get(i);
                if (dep.isRequired()) {
                    if (!dep.isAvailable()) {
                        allRequiredAvailable = false;
                        if (!dep.isInstanceBound()) {
                            keepInstanceAround = false;
                        }
                    }
                }
            }
            if (allRequiredAvailable) {
                if (isInstantiated) {
                    m_state = BOUND;
                }
                else {
                    m_state = TRACKING_OPTIONAL;
                }
            }
            else {
                if (keepInstanceAround) {
                    m_state = WAITING_FOR_REQUIRED_INSTANTIATED;
                }
                else {
                    m_state = WAITING_FOR_REQUIRED;
                }
            }
        }
        else {
            m_state = INACTIVE;
        }
    }
    
    public boolean isInactive() {
        return m_state == INACTIVE;
    }
    
    public boolean isWaitingForRequired() {
        return m_state == WAITING_FOR_REQUIRED;
    }
    
    public boolean isTrackingOptional() {
        return m_state == TRACKING_OPTIONAL;
    }
    
    public boolean isBound() {
        return m_state == BOUND;
    }
    
    public boolean isAllRequiredAvailable() {
        return isTrackingOptional() || isBound();
    }
    
    public boolean isWaitingForRequiredInstantiated() {
        return m_state == WAITING_FOR_REQUIRED_INSTANTIATED;
    }
    
    public List getDependencies() {
        return m_deps;
    }
    
    public synchronized String toString() {
        if (m_stringValue == null) {
            // we only need to determine this once, but we do it lazily
            StringBuffer buf = new StringBuffer();
            buf.append("State[" + STATES[m_state] + "|");
            List deps = m_deps;
            for (int i = 0; i < deps.size(); i++) {
                Dependency dep = (Dependency) deps.get(i);
                buf.append("(" + dep + (dep.isRequired() ? " R" : " O") + (dep.isAvailable() ? " +" : " -") + ")");
            }
            m_stringValue = buf.toString();
        }
        return m_stringValue;
    }
}