package com.cloud.resource;

import java.util.List;
import java.util.Set;

import com.cloud.utils.fsm.StateMachine;

public enum ResourceState {
    Creating,
    Enabled,
    Disabled,
    PrepareForMaintenance,
    ErrorInMaintenance,
    Maintenance,
    Error;

    public enum Event {
        InternalCreated("Resource is created"),
        Enable("Admin enables"),
        Disable("Admin disables"),
        AdminAskMaintenace("Admin asks to enter maintenance"),
        AdminCancelMaintenance("Admin asks to cancel maintenance"),
        InternalEnterMaintenance("Resource enters maintenance"),
        UpdatePassword("Admin updates password of host"),
        UnableToMigrate("Management server migrates VM failed"),
        Error("An internal error happened"),
        DeleteHost("Admin delete a host"),

        /*
         * Below events don't cause resource state to change, they are merely
         * for ClusterManager propagating event from one mgmt server to another
         */
        Unmanaged("Umanage a cluster");

        private final String comment;

        private Event(String comment) {
            this.comment = comment;
        }

        public String getDescription() {
            return this.comment;
        }

        public static Event toEvent(String e) {
            if (Enable.toString().equals(e)) {
                return Enable;
            } else if (Disable.toString().equals(e)) {
                return Disable;
            }

            return null;
        }
    }

    public ResourceState getNextState(Event a) {
        return s_fsm.getNextState(this, a);
    }

    public ResourceState[] getFromStates(Event a) {
        List<ResourceState> from = s_fsm.getFromStates(this, a);
        return from.toArray(new ResourceState[from.size()]);
    }

    public Set<Event> getPossibleEvents() {
        return s_fsm.getPossibleEvents(this);
    }

    public static String[] toString(ResourceState... states) {
        String[] strs = new String[states.length];
        for (int i = 0; i < states.length; i++) {
            strs[i] = states[i].toString();
        }
        return strs;
    }

    protected static final StateMachine<ResourceState, Event> s_fsm = new StateMachine<ResourceState, Event>();
    static {
        s_fsm.addTransition(null, Event.InternalCreated, ResourceState.Enabled);
        s_fsm.addTransition(ResourceState.Creating, Event.InternalCreated, ResourceState.Enabled);
        s_fsm.addTransition(ResourceState.Creating, Event.Error, ResourceState.Error);
        s_fsm.addTransition(ResourceState.Enabled, Event.Enable, ResourceState.Enabled);
        s_fsm.addTransition(ResourceState.Enabled, Event.InternalCreated, ResourceState.Enabled);
        s_fsm.addTransition(ResourceState.Enabled, Event.Disable, ResourceState.Disabled);
        s_fsm.addTransition(ResourceState.Enabled, Event.AdminAskMaintenace, ResourceState.PrepareForMaintenance);
        s_fsm.addTransition(ResourceState.Disabled, Event.Enable, ResourceState.Enabled);
        s_fsm.addTransition(ResourceState.Disabled, Event.Disable, ResourceState.Disabled);
        s_fsm.addTransition(ResourceState.Disabled, Event.InternalCreated, ResourceState.Disabled);
        s_fsm.addTransition(ResourceState.PrepareForMaintenance, Event.InternalEnterMaintenance, ResourceState.Maintenance);
        s_fsm.addTransition(ResourceState.PrepareForMaintenance, Event.AdminCancelMaintenance, ResourceState.Enabled);
        s_fsm.addTransition(ResourceState.PrepareForMaintenance, Event.UnableToMigrate, ResourceState.ErrorInMaintenance);
        s_fsm.addTransition(ResourceState.PrepareForMaintenance, Event.InternalCreated, ResourceState.PrepareForMaintenance);
        s_fsm.addTransition(ResourceState.Maintenance, Event.AdminCancelMaintenance, ResourceState.Enabled);
        s_fsm.addTransition(ResourceState.Maintenance, Event.InternalCreated, ResourceState.Maintenance);
        s_fsm.addTransition(ResourceState.Maintenance, Event.DeleteHost, ResourceState.Disabled);
        s_fsm.addTransition(ResourceState.ErrorInMaintenance, Event.InternalCreated, ResourceState.ErrorInMaintenance);
        s_fsm.addTransition(ResourceState.ErrorInMaintenance, Event.Disable, ResourceState.Disabled);
        s_fsm.addTransition(ResourceState.ErrorInMaintenance, Event.DeleteHost, ResourceState.Disabled);
        s_fsm.addTransition(ResourceState.ErrorInMaintenance, Event.InternalEnterMaintenance, ResourceState.Maintenance);
        s_fsm.addTransition(ResourceState.Error, Event.InternalCreated, ResourceState.Error);
    }
}