package com.c2kernel.persistency;
import com.c2kernel.entity.C2KLocalObject;
import com.c2kernel.persistency.outcome.Outcome;
import com.c2kernel.persistency.outcome.Viewpoint;
import com.c2kernel.process.auth.Authenticator;
import com.c2kernel.utils.Logger;

/** Interface for persistency managers of entities. It allows different kernel objects to be stored in different backend. For instance, 
 * Properties may be stored in LDAP, while Events, Outcomes and Viewpoints could be stored in a relational database. There are old generic
 * query methods, but these are deprecated. The kernel does no analytical querying of the ClusterStorages, only simple gets and puts.
 *
 * Each first-level path under the Item is defined as a Cluster. Different Clusters may be stored in different places.
 * Each ClusterStorage must support {@link #get(Integer, String)} and {@link #getClusterContents(Integer, String)} for clusters they return 
 * {@link #READ} and {@link #READWRITE} from queryClusterSupport
 * and {@link #put(Integer, C2KLocalObject)} and {@link #delete(Integer, String)} for clusters they return {@link #WRITE} and {@link #READWRITE}
 * from {@link #getClusterContents(Integer, String)}.
 * Operations that have notbeen declared as not supported should throw a ClusterStorageException.
 * If a cluster does not exist, get should return null, and delete should return with no action.
*/
public abstract class ClusterStorage {

    /**
     * Constant to return from {@link #queryClusterSupport(String)} for Cluster types this storage does not support.
     */
    public static final short NONE = 0;
    /**
     * Constant to return from {@link #queryClusterSupport(String)} for Cluster types this storage can read from a database but not write. 
     * An example would be pre-existing data in a database that is mapped to Items in some way.
     */
    public static final short READ = 1;
    /**
     * Constant to return from {@link #queryClusterSupport(String)} for Cluster types this storage can write to a database but not read.
     * An example would be a realtime database export of data, which is transformed in an unrecoverable way for use in other systems.
     */
    public static final short WRITE = 2;
    /**
     * Constant to return from {@link #queryClusterSupport(String)} for data stores that CRISTAL may use for both reading and writing for the given Cluster type.
     */
    public static final short READWRITE = 3;

    // Cluster types
    /**
     * The defined path of the root of the CRISTAL Kernel object cluster tree. A zero-length string.
     */
    public static final String ROOT =        "";
    /**
     * The root of the Property object cluster. All Property paths start with this. Defined as "Property". Properties are 
     * stored underneath according to their name e.g. "Property/Name"
     */
    public static final String PROPERTY   =  "Property";
    /**
     * The root of the Collection object cluster. All Collection paths start with this. Defined as "Collection". Collections 
     * are stored underneath by name e.g. "Collection/Composition"
     */    
    public static final String COLLECTION =  "Collection";
    /**
     * The cluster which holds the Item workflow. Defined as "LifeCycle". Holds the workflow inside, which is named "workflow", 
     * hence "LifeCycle/workflow". 
     * @see com.c2kernel.lifecycle.instance.Workflow
     */
    public static final String LIFECYCLE =   "LifeCycle";
    /**
     * This cluster holds all outcomes of this Item. The path to each outcome is "Outcome/<i>Schema Name</i>/<i>Schema Version</i>/<i>Event ID</i>"
     */
	public static final String OUTCOME =     "Outcome";
	/**
	 * This is the cluster that contains all event for this Item. This cluster may be instantiated in a client as a History, which is a
	 * RemoteMap. Events are stored with their ID: "/AuditTrail/<i>Event ID</i>"
	 */
    public static final String HISTORY =     "AuditTrail";
    /**
     * This cluster contains all viewpoints. Its name is defined as "ViewPoint". The paths of viewpoint objects stored here follow this pattern: 
     * "ViewPoint/<i>Schema Name</i>/<i>Viewpoint Name</i>"
     */
	public static final String VIEWPOINT =   "ViewPoint";
	/**
	 * Agents store their persistent jobs in this cluster that have been pushed to them by activities configured to do so. The name is defined as "Job" 
	 * and each new job received is assigned an integer ID one more than the highest already present.
	 */
	public static final String JOB =         "Job";
	
	/**
	 * An array of all currently supported cluster types, for iterative purposes.
	 */
	public static final String[] allClusterTypes = { PROPERTY, COLLECTION, LIFECYCLE, OUTCOME, HISTORY, VIEWPOINT, JOB };

    // connection maintenance
    public abstract void open(Authenticator auth)
    	throws ClusterStorageException;
    public abstract void close()
    	throws ClusterStorageException;

    // introspection
    public abstract short queryClusterSupport(String clusterType);
    public abstract String getName();
    // for addressing queries
    public abstract String getId();


    /** Quickly gets the first string of the slashed path */
    public static String getClusterType(String path) {
        try {
        	if (path == null || path.length() == 0) return ClusterStorage.ROOT;
            int start = path.charAt(0) == '/' ? 1 : 0;
            int end = path.indexOf('/', start + 1);
            if (end == -1) end = path.length();
            return path.substring(start, end);
        } catch (Exception ex) {
        	Logger.error(ex);
            return ClusterStorage.ROOT;
        }
    }

	public static String getPath(C2KLocalObject obj) {
		String root = obj.getClusterType();
		if (root == null) return null; // no storage allowed
		if (obj instanceof Outcome) {
			Outcome oc = (Outcome)obj;
			return root+"/"+oc.getSchemaType()+"/"+oc.getSchemaVersion()+"/"+oc.getName();
		}
		else if (obj instanceof Viewpoint) {
			Viewpoint vp = (Viewpoint)obj;
			return root+"/"+vp.getSchemaName()+"/"+vp.getName();
		}
		else
			return root+"/"+obj.getName();
	}

	/* object manipulation */

    // retrieve object by path
    public abstract C2KLocalObject get(Integer sysKey, String path)
    	throws ClusterStorageException;
    // store object by path
    public abstract void put(Integer sysKey, C2KLocalObject obj)
    	throws ClusterStorageException;
    // delete cluster
    public abstract void delete(Integer sysKey, String path)
    	throws ClusterStorageException;

    // db specific queries
    @Deprecated
     public Object query(Object query)
    	throws ClusterStorageException {
    	throw new ClusterStorageException("Query not supported on this storage");
    }

    @Deprecated
    public String queryToXML(String query, boolean genericFormat)
     throws ClusterStorageException {
     throw new ClusterStorageException("Query not supported on this storage");
    }


    // directory listing
    public abstract String[] getClusterContents(Integer sysKey, String path)
    	throws ClusterStorageException;

}