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package org.apache.cayenne.velocity;

import java.io.IOException;
import java.io.Writer;
import java.util.Collection;
import java.util.Iterator;

import org.apache.cayenne.access.translator.ParameterBinding;
import org.apache.cayenne.dba.TypesMapping;
import org.apache.cayenne.util.ConversionUtil;
import org.apache.velocity.context.InternalContextAdapter;
import org.apache.velocity.exception.MethodInvocationException;
import org.apache.velocity.exception.ParseErrorException;
import org.apache.velocity.exception.ResourceNotFoundException;
import org.apache.velocity.runtime.directive.Directive;
import org.apache.velocity.runtime.parser.node.Node;

/**
 * A custom Velocity directive to create a PreparedStatement parameter text.
 * There are the following possible invocation formats inside the template:
 * 
 *  * #bind(value) - e.g. #bind($xyz)
 * #bind(value jdbc_type_name) - e.g. #bind($xyz 'VARCHAR'). This is the most common and useful form.
 * #bind(value jdbc_type_name, scale) - e.g. #bind($xyz 'VARCHAR' 2)
 * 
 * 
 * Other examples:
 * 
 * 
 * Binding literal parameter value:
 * 
 * 
 * "WHERE SOME_COLUMN > #bind($xyz)" produces
 * "WHERE SOME_COLUMN > ?" and also places the value of the
 * "xyz" parameter in the context "bindings" collection.
 * 
 * 
 * Binding ID column of a Persistent value:
 * 
 * 
 * "WHERE ID_COL1 = #bind($helper.cayenneExp($xyz, 'db:ID_COL2')) 
 * AND ID_COL2 = #bind($helper.cayenneExp($xyz, 'db:ID_COL2'))" produces
 * "WHERE ID_COL1 = ? AND ID_COL2 = ?" and also places the values
 * of id columns of the Persistent parameter "xyz" in the context "bindings"
 * collection.
 * 
 * 
 * @since 1.1
 */
public class BindDirective extends Directive {

	@Override
	public String getName() {
		return "bind";
	}

	@Override
	public int getType() {
		return LINE;
	}

	/**
	 * Extracts the value of the object property to render and passes control to
	 * {@link #render(InternalContextAdapter, Writer, ParameterBinding)} to do
	 * the actual rendering.
	 */
	@Override
	public boolean render(InternalContextAdapter context, Writer writer, Node node) throws IOException,
			ResourceNotFoundException, ParseErrorException, MethodInvocationException {

		Object value = getChild(context, node, 0);
		Object type = getChild(context, node, 1);
		int scale = ConversionUtil.toInt(getChild(context, node, 2), -1);
		String typeString = type != null ? type.toString() : null;

		if (value instanceof Collection) {
			Iterator it = ((Collection) value).iterator();
			while (it.hasNext()) {
				render(context, writer, node, it.next(), typeString, scale);

				if (it.hasNext()) {
					writer.write(',');
				}
			}
		} else {
			render(context, writer, node, value, typeString, scale);
		}

		return true;
	}

	/**
	 * @since 3.0
	 */
	protected void render(InternalContextAdapter context, Writer writer, Node node, Object value, String typeString,
			int scale) throws IOException, ParseErrorException {

		int jdbcType;
		if (typeString != null) {
			jdbcType = TypesMapping.getSqlTypeByName(typeString);
		} else if (value != null) {
			jdbcType = TypesMapping.getSqlTypeByJava(value.getClass());
		} else {
			// value is null, set JDBC type to NULL
			jdbcType = TypesMapping.getSqlTypeByName(TypesMapping.SQL_NULL);
		}

		if (jdbcType == TypesMapping.NOT_DEFINED) {
			throw new ParseErrorException("Can't determine JDBC type of binding (" + value + ", " + typeString
					+ ") at line " + node.getLine() + ", column " + node.getColumn());
		}

		render(context, writer, new ParameterBinding(value, jdbcType, scale));
	}

	protected void render(InternalContextAdapter context, Writer writer, ParameterBinding binding) throws IOException {

		bind(context, binding);
		writer.write('?');
	}

	protected Object getChild(InternalContextAdapter context, Node node, int i) throws MethodInvocationException {
		return (i >= 0 && i < node.jjtGetNumChildren()) ? node.jjtGetChild(i).value(context) : null;
	}

	/**
	 * Adds value to the list of bindings in the context.
	 */
	protected void bind(InternalContextAdapter context, ParameterBinding binding) {

		@SuppressWarnings("unchecked")
		Collection bindings = (Collection)
				context.getInternalUserContext().get(VelocitySQLTemplateProcessor.BINDINGS_LIST_KEY);

		if (bindings != null) {
			bindings.add(binding);
		}
	}
}