/*
 * Copyright 2005-2011 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *	   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.xml.validation;

import java.io.IOException;
import javax.xml.validation.Validator;

import org.springframework.core.io.Resource;
import org.springframework.util.Assert;
import org.springframework.xml.JaxpVersion;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * Factory for {@link XmlValidator} objects, being aware of JAXP 1.3 {@link Validator}s, and JAXP 1.0 parsing
 * capabilities. Mainly for internal use within the framework.
 *
 * <p>The goal of this class is to avoid runtime dependencies on JAXP 1.3 by using the best validation implementation that
 * is available. Prefers JAXP 1.3 {@link XmlValidator} implementations to a custom, SAX-based implementation.
 *
 * @author Arjen Poutsma
 * @see XmlValidator
 * @since 1.0.0
 */
public abstract class XmlValidatorFactory {

	private static final Log logger = LogFactory.getLog(XmlValidatorFactory.class);

	/** Constant that defines a W3C XML Schema. */
	public static final String SCHEMA_W3C_XML = "http://www.w3.org/2001/XMLSchema";

	/** Constant that defines a RELAX NG Schema. */
	public static final String SCHEMA_RELAX_NG = "http://relaxng.org/ns/structure/1.0";

	/**
	 * Create a {@link XmlValidator} with the given schema resource and schema language type. The schema language must
	 * be one of the {@code SCHEMA_XXX} constants.
	 *
	 * @param schemaResource a resource that locates the schema to validate against
	 * @param schemaLanguage the language of the schema
	 * @return a validator
	 * @throws IOException				if the schema resource cannot be read
	 * @throws IllegalArgumentException if the schema language is not supported
	 * @throws IllegalStateException	if JAXP 1.0 cannot be located
	 * @throws XmlValidationException	if a {@code XmlValidator} cannot be created
	 * @see #SCHEMA_RELAX_NG
	 * @see #SCHEMA_W3C_XML
	 */
	public static XmlValidator createValidator(Resource schemaResource, String schemaLanguage) throws IOException {
		return createValidator(new Resource[]{schemaResource}, schemaLanguage);
	}

	/**
	 * Create a {@link XmlValidator} with the given schema resources and schema language type. The schema language must
	 * be one of the {@code SCHEMA_XXX} constants.
	 *
	 * @param schemaResources an array of resource that locate the schemas to validate against
	 * @param schemaLanguage  the language of the schemas
	 * @return a validator
	 * @throws IOException				if the schema resource cannot be read
	 * @throws IllegalArgumentException if the schema language is not supported
	 * @throws IllegalStateException	if JAXP 1.0 cannot be located
	 * @throws XmlValidationException	if a {@code XmlValidator} cannot be created
	 * @see #SCHEMA_RELAX_NG
	 * @see #SCHEMA_W3C_XML
	 */
	public static XmlValidator createValidator(Resource[] schemaResources, String schemaLanguage) throws IOException {
		Assert.notEmpty(schemaResources, "No resources given");
		Assert.hasLength(schemaLanguage, "No schema language provided");
		Assert.isTrue(SCHEMA_W3C_XML.equals(schemaLanguage) || SCHEMA_RELAX_NG.equals(schemaLanguage),
				"Invalid schema language: " + schemaLanguage);
		for (Resource schemaResource : schemaResources) {
			Assert.isTrue(schemaResource.exists(), "schema [" + schemaResource + "] does not exist");
		}
		if (JaxpVersion.getJaxpVersion() >= JaxpVersion.JAXP_13) {
			logger.trace("Creating JAXP 1.3 XmlValidator");
			return Jaxp13ValidatorFactory.createValidator(schemaResources, schemaLanguage);
		}
		else {
			throw new IllegalStateException("Could not locate JAXP 1.3.");
		}
	}

}