/******************************************************************************/
/* File: request_processing.beh                                               */
/*                                                                            */
/* Describes the implementations for 3 classes:                               */
/*     RequestProcessingVisitor,                                              */
/*     VendorFormat, and                                                      */
/*     VendorDriver.                                                          */
/*                                                                            */
/* The visitor class traverses the parts of a Request structure (created by   */
/* parsing the external input) and breaks it up into separate "container"     */
/* objects for storing each component of the request.                         */
/* These components are:                                                      */
/*     the connection arguments,                                              */
/*     the request type (Query / Insert),                                     */
/*     the target data structure - table(s) and corresponding column(s),      */
/*     the generated SQL statement for submitting the request to the DBMS,    */
/*     the object hierarchy structure requested.                              */
/* The visitor class uses static methods defined in the Utils class for       */
/* dynamically creating objects specific to the corresponding DBMS vendor.    */
/* It finally returns a vector of these component objects.                    */
/*                                                                            */
/* The methods defined here for the VendorFormat and VendorDriver classes are */
/* just used for printing out their contents using the provided PrintVisitor. */
/*                                                                            */
/******************************************************************************/

RequestProcessingVisitor
{
    {{
    private String vendor;
    private String url;
    private String userid;
    private String password;

    private String requestType;

    private Vector targetData;
    private EntityStructure targetItem;
    private Vector targetColumns;
    private String lastColumnType;
    private String insertColumnValues;

    private String condition;
    private String orderTable;
    private String order;

    private String parentTable;
    private String parentColumn;
    private String childTable;
    private String childColumn;
    private String relationColumn;


    // Initialize variables used or storing intermediate state of the visitor
    public void start()
    {
	vendor = ""; url = ""; userid = ""; password = "";

	requestType = "";

	targetData = new Vector(); targetItem = null;
	targetColumns = new Vector(); insertColumnValues = "";

	condition = ""; order = "";

	parentTable = ""; parentColumn = "";
	childTable = ""; childColumn = ""; relationColumn = "";
    }


    // Implement the methods to be invoked on visiting each node in the object
    // hierarchy
    public void before(Vendor host)
    {
	vendor = host.get_vendor();
    }
    public void before(Url host)
    {
	url = host.get_url();
    }
    public void before(Userid host)
    {
	userid = host.get_userid();
    }
    public void before(Password host)
    {
	password = host.get_password();
    }


    public void before(Query host)
    {
	requestType = XMLandDB.QUERY;
    }
    public void before(Insert host)
    {
	requestType = XMLandDB.INSERT;
    }

    public void before(TableName host)
    {
	if (targetItem != null)
	{
	    targetItem.setColumns(targetColumns);
	    targetData.addElement(targetItem);

	    targetColumns = new Vector();
	}

	String tableName = host.get_name();

	targetItem = new EntityStructure(tableName);
	parentTable = tableName;
	childTable = tableName;
    }
    public void before(ColumnSpec host)
    {
	String columnName = host.get_spec();
	String columnType = host.get_type().toString();
	targetColumns.addElement(
	  new EntityStructure.ColumnDetail(columnName, columnType));

	lastColumnType = columnType;
    }

    public void before(Condition host)
    {
	condition = host.get_condition();
    }

    public void before(OrderItem host)
    {
	orderTable = "";
    }
    public void before(OrderTable host)
    {
	orderTable = host.get_name();
    }
    public void before(OrderColumn host)
    {
	order = order + (order.equals("") ? "" : ", ") +
		  (orderTable.equals("") ? "" : (orderTable + ".")) +
		  host.get_name();
    }

    public void before(InsertValue host)
    {
	insertColumnValues = insertColumnValues +
			       (insertColumnValues.equals("") ? "" : ", ") +
			       ((lastColumnType.equals("Text") ? "'" : "") +
			        host.get_value() +
			        (lastColumnType.equals("Text") ? "'" : ""));
    }


    public void before(ParentTable host)
    {
	parentTable = host.get_name();
    }
    public void before(ParentColumn host)
    {
	parentColumn = host.get_name();
    }
    public void before(ChildTable host)
    {
	childTable = host.get_name();
    }
    public void before(ChildColumn host)
    {
	childColumn = host.get_name();
    }
    public void before(RelationColumn host)
    {
	relationColumn = host.get_name();
    }


    public Object getReturnValue()
    {
	Vector returnValues = new Vector();

	returnValues.addElement(new ConnectionArgs(vendor, url, userid,
						   password));

	returnValues.addElement(requestType);

	if (targetItem != null)
	{
	    targetItem.setColumns(targetColumns);
	    targetData.addElement(targetItem);
	}
	EntityStructure entities[] = new EntityStructure[targetData.size()];
	targetData.copyInto(entities);
	returnValues.addElement(entities);

	String tableNames = "", columnNames = "",
	       prefix = "";
	for (int i = 0; i < entities.length; i++)
	{
	    tableNames = tableNames + (tableNames.equals("") ? "" : ", ") +
			   entities[i].tableName;
	    if (entities.length > 1)
		prefix = entities[i].tableName + ".";
	    for (int j = 0; j < entities[i].columns.length; j++)
	    {
		columnNames = columnNames +
		   (columnNames.equals("") ? "" : ", ") +
		   prefix + entities[i].columns[j].name;
	    }
	}

	String sqlStmt;
	if (requestType.equals(XMLandDB.QUERY))  // it is a select statement
	{
	    if (! parentColumn.equals(""))
		order = ((entities.length > 1) ? (parentTable + ".") : "") +
			parentColumn + ", " +
			((entities.length > 1) ? (childTable + ".") : "") +
			childColumn +
			(order.equals("") ? "" : (", " + order));

	    sqlStmt = buildSelectStatement(tableNames, columnNames, condition,
					   order);
	}
	else  // it is an insert statement
	{

	    sqlStmt = buildInsertStatement(tableNames, columnNames,
					   insertColumnValues);
	}
	returnValues.addElement(sqlStmt);

	returnValues.addElement(parentColumn.equals("") ? null :
				new HierarchyArgs(parentTable, parentColumn,
						  childTable, childColumn,
						  relationColumn));

	return returnValues;
    }


    // Private accessory methods for constructing a SQL statement from parts.
    // All operations in this class involving dynamic creation of objects are
    // centralized here.
    private String buildSelectStatement(String tableNames, String columnNames,
					String condition, String order)
    {
	Object selectFormat =
	    (Object) Utils.instantiate(vendor + "_SelectFormat");

	if (selectFormat == null)
	    return null;

	if (! Utils.executeSetMethod(selectFormat, "set_tableList",
				     new Ident(tableNames)))
	    return null;

	if (! Utils.executeSetMethod(selectFormat, "set_columnList",
				     new Ident(columnNames)))
	    return null;

	if (! condition.equals(""))
	{
	    if (! Utils.executeSetMethod(selectFormat, "set_whereClause",
					 new Ident(condition)))
	    return null;
	}
	if (! order.equals(""))
	{
	    if (! Utils.executeSetMethod(selectFormat, "set_orderByClause",
					 new Ident(order)))
	    return null;
	}


	Object vendorFormat = (Object) Utils.instantiate(vendor + "_Format");
	if (vendorFormat == null)
	    return null;

	if (! Utils.executeSetMethod(vendorFormat, "set_format", selectFormat,
				     vendor + "_StmtFormat"))
	    return null;


	return ((VendorFormat) vendorFormat).getSQLStatement();
    }
    private String buildInsertStatement(String tableNames, String columnNames,
					String columnValues)
    {
	Object insertFormat =
	    (Object) Utils.instantiate(vendor + "_InsertFormat");

	if (insertFormat == null)
	    return null;

	if (! Utils.executeSetMethod(insertFormat, "set_table",
				     new Ident(tableNames)))
	    return null;

	if (! Utils.executeSetMethod(insertFormat, "set_columnList",
				     new Ident(columnNames)))
	    return null;

	if (! Utils.executeSetMethod(insertFormat, "set_valueList",
				     new Ident(columnValues)))
	return null;


	Object vendorFormat = (Object) Utils.instantiate(vendor + "_Format");
	if (vendorFormat == null)
	    return null;

	if (! Utils.executeSetMethod(vendorFormat, "set_format", insertFormat,
				     vendor + "_StmtFormat"))
	    return null;


	return ((VendorFormat) vendorFormat).getSQLStatement();
    }
    }}
}


VendorFormat
{
    {{
    public String getSQLStatement()
    {
	StringWriter p = new StringWriter();
	universal_trv0(new PrintVisitor(new PrintWriter(p)));
	return p.toString();
    }
    }}
}


VendorDriver
{
    {{
    public String getDriverName()
    {
	StringWriter p = new StringWriter();
	universal_trv0(new PrintVisitor(new PrintWriter(p)));
	return p.toString();
    }
    }}
}