/*******************************************************************************
 * Copyright (c) 2020, 2021 Obeo.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 * 
 * Contributors:
 *     Obeo - initial API and implementation
 *******************************************************************************/
package org.eclipse.acceleo.aql;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

import org.eclipse.acceleo.AcceleoPackage;
import org.eclipse.acceleo.Module;
import org.eclipse.acceleo.ModuleElement;
import org.eclipse.acceleo.Template;
import org.eclipse.acceleo.aql.evaluation.AcceleoEvaluator;
import org.eclipse.acceleo.aql.evaluation.writer.DefaultGenerationStrategy;
import org.eclipse.acceleo.query.ast.EClassifierTypeLiteral;
import org.eclipse.acceleo.query.runtime.IQueryEnvironment;
import org.eclipse.acceleo.query.services.EObjectServices;
import org.eclipse.acceleo.util.AcceleoSwitch;
import org.eclipse.emf.common.util.URI;
import org.eclipse.emf.ecore.EClass;
import org.eclipse.emf.ecore.EClassifier;
import org.eclipse.emf.ecore.EObject;
import org.eclipse.emf.ecore.resource.Resource;
import org.eclipse.emf.ecore.resource.ResourceSet;

/**
 * Utility class for Acceleo.
 * 
 * @author <a href="mailto:yvan.lussaud@obeo.fr">Yvan Lussaud</a>
 */
public final class AcceleoUtil {

	/**
	 * "self".
	 */
	private static final String SELF = "self";

	/**
	 * Constructor.
	 */
	private AcceleoUtil() {
		// utility class can't be instantiated
	}

	/**
	 * Provides the name of the implicit variable in an Acceleo {@link Template} that represents the
	 * {@link Template} itself.
	 * 
	 * @return the name of the implicit variable of an Acceleo {@link Template}.
	 */
	public static String getTemplateImplicitVariableName() {
		return SELF;
	}

	/**
	 * Gets the {@link Template#isMain() main} {@link Template} of the given {@link Module}.
	 * 
	 * @param module
	 *            the {@link Module}
	 * @return the {@link Template#isMain() main} {@link Template} of the given {@link Module} if any,
	 *         <code>null</code> otherwise
	 */
	public static Template getMainTemplate(Module module) {
		Template res = null;

		for (ModuleElement moduleElement : module.getModuleElements()) {
			if (moduleElement instanceof Template && ((Template)moduleElement).isMain()) {
				res = (Template)moduleElement;
				break;
			}
		}

		return res;
	}

	/**
	 * Generates with the given {@link AcceleoEvaluator} and {@link IAcceleoEnvironment}.
	 * 
	 * @param evaluator
	 *            the {@link AcceleoEvaluator}
	 * @param acceleoEnvironment
	 *            the {@link IAcceleoEnvironment}
	 * @param module
	 *            the {@link Module}
	 * @param model
	 *            the {@link Resource} containing the model
	 * @param destination
	 *            destination {@link URI}
	 */
	public static void generate(AcceleoEvaluator evaluator, IAcceleoEnvironment acceleoEnvironment,
			Module module, Resource model, URI destination) {
		generate(evaluator, acceleoEnvironment, module, Collections.singletonList(model), destination);
	}

	/**
	 * Generates with the given {@link AcceleoEvaluator} and {@link IAcceleoEnvironment}.
	 * 
	 * @param evaluator
	 *            the {@link AcceleoEvaluator}
	 * @param acceleoEnvironment
	 *            the {@link IAcceleoEnvironment}
	 * @param module
	 *            the {@link Module}
	 * @param resourceSet
	 *            the {@link ResourceSet} containing the input model(s)
	 * @param destination
	 *            the destination {@link URI}
	 */
	public static void generate(AcceleoEvaluator evaluator, IAcceleoEnvironment acceleoEnvironment,
			Module module, ResourceSet resourceSet, URI destination) {
		generate(evaluator, acceleoEnvironment, module, resourceSet.getResources(), destination);
	}

	private static void generate(AcceleoEvaluator evaluator, IAcceleoEnvironment acceleoEnvironment,
			Module module, List<Resource> resources, URI destination) {
		final IQueryEnvironment queryEnvironment = acceleoEnvironment.getQueryEnvironment();

		final EObjectServices services = new EObjectServices(queryEnvironment, null, null);
		final Template main = getMainTemplate(module);
		// TODO more than one parameter is allowed ?
		// TODO not EClass type ?
		// TODO more than one EClass type ?
		final String parameterName = main.getParameters().get(0).getName();
		// TODO use IType ?
		// TODO this is really quick and dirty
		final EClassifierTypeLiteral eClassifierTypeLiteral = (EClassifierTypeLiteral)main.getParameters()
				.get(0).getType().getAst();
		final Collection<EClassifier> eClassifiers = queryEnvironment.getEPackageProvider().getTypes(
				eClassifierTypeLiteral.getEPackageName(), eClassifierTypeLiteral.getEClassifierName());
		if (!eClassifiers.isEmpty()) {
			final EClass parameterType = (EClass)eClassifiers.iterator().next();
			final List<EObject> values = new ArrayList<EObject>();
			for (Resource model : resources) {
				for (EObject root : model.getContents()) {
					if (parameterType.isInstance(root)) {
						values.add(root);
					}
					values.addAll(services.eAllContents(root, parameterType));
				}
			}

			final Map<String, Object> variables = new HashMap<String, Object>();
			for (EObject value : values) {
				variables.put(parameterName, value);
				evaluator.generate(module, variables, new DefaultGenerationStrategy(), destination);
			}
		}
	}

	/**
	 * Provides the concrete Acceleo {@link EClass EClasses} that are, inherit or extend the given Acceleo
	 * {@link EClass}. This is useful to use an {@link AcceleoSwitch} on non-instantiable EClasses.
	 * 
	 * @param superType
	 *            the (non-{@code null}) {@link AcceleoPackage Acceleo} {@link EClass}.
	 * @return the {@link List} of concrete (i.e. both {@link EClass#isInterface()} and
	 *         {@link EClass#isAbstract()} return {@code false}) {@link EClass EClasses} from
	 *         {@link AcceleoPackage} that are, inherit, or extend, the given Acceleo {@link EClass}.
	 */
	public static List<EClass> getConcreteAcceleoTypesInheriting(EClass superType) {
		if (!superType.getEPackage().equals(AcceleoPackage.eINSTANCE)) {
			throw new IllegalArgumentException(
					"This can only be used for EClasses from the Acceleo EPackage. " + superType
							+ " is from EPackage " + superType.getEPackage() + ".");
		}
		List<EClass> eClasses = new ArrayList<>();
		if (!superType.isAbstract() && !superType.isInterface()) {
			eClasses.add(superType);
		}
		List<EClass> allAcceleoConcreteEClasses = AcceleoPackage.eINSTANCE.getEClassifiers().stream().filter(
				EClass.class::isInstance).map(EClass.class::cast).filter(eClass -> !eClass.isInterface()
						&& !eClass.isAbstract()).collect(Collectors.toList());
		List<EClass> acceleoConcreteSubTypes = allAcceleoConcreteEClasses.stream().filter(eClass -> eClass
				.getESuperTypes().contains(superType)).collect(Collectors.toList());
		eClasses.addAll(acceleoConcreteSubTypes);
		return eClasses;
	}

}