package org.greenstone.gsdl3.gs3build.metadata;

import java.io.PrintWriter;

import java.util.List;
import java.util.Iterator;
import java.sql.SQLException;
import java.sql.Statement;
import java.sql.ResultSet;

import org.greenstone.gsdl3.gs3build.database.*;

/**
 *  Implement a single namespace
 */

public abstract class METSNamespace
{
    protected String       type;        // the type of the metadata
    protected String       otherType;   // if a non-standard type, then...
    protected String       name;        // e.g. "DC" for Dublin Core
    protected METSLocation location;    // the location of the corresponding file
    protected String       group;       // the group of metadata namespaces to which
    // this namespace belongs
    protected String       id;          // the ID for this namespace

    public METSNamespace(String name)
    { 
	this.name        = name;
	this.location    = null;
	this.group       = null;
	this.id          = null;
    }
    
    public METSNamespace(String name, METSLocation location)
    { 
	this.location    = location;
	this.name        = name;
	this.group       = null;
	this.id          = null;
    }
    
    /**
     *  Get the name of the namespace...
     *
     *  @return <code>String</code> the name of the namespace
     */
    public String getName()
    { 
	return this.name;
    }
    
    /**
     *  Get the group of namespaces to which this namespace belongs.
     *
     *  @return <code>String</code> the name of the namespace group
     */
    public String getGroup()
    {
	return this.group;
    }
    
    /**
     *  Set the group of namespaces to which this namespace belongs.
     *
     *  @param <code>String</code> the name of the namespace group
     */
    public void setGroup(String group)
    { 
	this.group = group;
    }
    
    /**
     *  Get the ID for this namespace.
     *
     *  @return <code>String</code> the id of the namespace
     */
    public String getID()
    {
	return this.id;
    }
    
    /**
     *  Set the id of this namespace.
     *
     *  @param <code>String</code> the name of the namespace group
     */
    public void setID(String id)
    {
	this.id = id;
    }

    /**
     *  <p>Indicate whether this namespace is open to being changed or not.</p>
     *  <p>Metadata which is created from a distinct file cannot be changed,
     *  only those which have no associated file can be modified.
     *
     *	@return <code>boolean</code> whether this namespace can be altered.
     */
    public boolean isEditable()
    { 
	return (this.location == null);
    }
    
    public abstract boolean addMetadata(String label, String value);
    public abstract boolean setMetadata(String label, String value);
    public abstract boolean removeMetadata(String label);
    public abstract boolean removeMetadata(String label, String value);
    public abstract List    getMetadata(String label);
    public abstract Iterator getMetadataNames();
    public abstract boolean write(PrintWriter writer);
    //  public abstract boolean writeSQL(GS3SQLConnection connection);

    /**
     *  Write out the metadata to an SQL database through a <code>GS3SQLConnection</code>.
     *
     *  @param <code>int</code> the sql identifier of the parent object (in "metadata") table.
     *  @param <code>GS3SQLConnection</code> the SQL database to use.
     */
    public boolean writeSQL(int parentId, GS3SQLConnection connection)
    { 
	GS3SQLAction action;

	// If the namespace is not null, then set it...
	if (this.id != null) {
	    // use an update action in this case...
	    GS3SQLUpdate update = new GS3SQLUpdate("namespaces");
	    update.addValue("NamespaceID", this.id);

	    // set up the where clause
	    GS3SQLWhere where = 
		new GS3SQLWhere(new GS3SQLWhereItem("NamespaceRef", "=", this.id, 
						    GS3SQLField.INTEGER_TYPE));
	    update.setWhere(where);
	    action = update;
	}
	else {
	    GS3SQLInsert insert = new GS3SQLInsert("namespaces");
	    action = insert;
	}

	if (this.location != null) {
	    action.addValue("FileLoc", this.location.getLocation().toString());
	    action.addValue("FileType", "URL");
	}
	else {
	    // no location stuff
	}
	action.addValue("MetadataRef", Integer.toString(parentId), GS3SQLField.INTEGER_TYPE);
	action.addValue("NamespaceType", this.name);

	// Execute the action
	Statement statement = null;
	try {
	    statement = connection.createStatement();
	    statement.execute(action.toString());
	} catch (SQLException e) {
	    System.err.println("METSNamespace.writeSQL(): "+e);
	    return false;
	}
	// then get the namespace reference number if needsbe...
	if (this.id == null) {
	    GS3SQLSelect select = new GS3SQLSelect("namespaces");
	    select.addField("NamespaceRef");
	    GS3SQLWhereItem whereItem = new GS3SQLWhereItem("MetadataRef", "=", Integer.toString(parentId), GS3SQLField.INTEGER_TYPE);
	    GS3SQLWhere where = new GS3SQLWhere(whereItem);
	    whereItem = new GS3SQLWhereItem("NamespaceType", "=", this.name);
	    where.add(where);
	    try {
		ResultSet result  = statement.executeQuery(select.toString());
      		if (result.last()) {
		    this.id = Integer.toString(result.getInt("NamespaceRef"));
		}
		statement.close();
	    }
	    catch (SQLException sqlex){
		this.id = null;
		System.err.println("METSNamespace.writeSQL(): "+sqlex);
		return false;
	    }
	}
	
	return true;
    }
    
    public static METSNamespace readSQL(GS3SQLConnection connection, ResultSet resultSet)
    {
	METSLocation metsLocation = null;
	
	try {
	    String name = resultSet.getString("NamespaceType");
	    String id = resultSet.getString("NamespaceRef");
	    String location = resultSet.getString("FileLoc");
	    String type = resultSet.getString("FileType");
	    if (location != null && type != null) {
		metsLocation = new METSLocation(type, location);
	    }
	    
	    METSNamespace namespace = NamespaceFactory.initNamespace(name, metsLocation);
	    namespace.id = id;

	    int namespaceRef = resultSet.getInt("NamespaceRef");
      
	    GS3SQLSelect select = new GS3SQLSelect("mdvalues");
	    select.addField("*");
	    GS3SQLWhere where = new GS3SQLWhere(new GS3SQLWhereItem("NamespaceRef", "=", Integer.toString(namespaceRef),
								    GS3SQLField.INTEGER_TYPE));
	    select.setWhere(where);

	    Statement statement = connection.createStatement();
	    ResultSet valuesSet = statement.executeQuery(select.toString());
	    if (valuesSet.first()) {
		do {
		    String label = valuesSet.getString("Label");
		    String value = valuesSet.getString("Value");

		    namespace.addMetadata(label, value);
		}
		while (valuesSet.next());
	    }
	    statement.close();
	    return namespace;
	}
	catch (java.net.MalformedURLException urlEx){
	    System.err.println("METSNamespace.readSQL(): "+urlEx);
	}
	catch (SQLException sqlEx){
	    System.err.println("METSNamespace.readSQL(): "+sqlEx);
	}    
	return null;
    }
}