/**
 * Copyright (C) 2010-2017 Gordon Fraser, Andrea Arcuri and EvoSuite
 * contributors
 *
 * This file is part of EvoSuite.
 *
 * EvoSuite is free software: you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published
 * by the Free Software Foundation, either version 3.0 of the License, or
 * (at your option) any later version.
 *
 * EvoSuite is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with EvoSuite. If not, see <http://www.gnu.org/licenses/>.
 */
package org.evosuite.junit;

import static org.junit.Assert.assertNotNull;

import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URI;
import java.net.URL;
import java.net.URLClassLoader;
import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.Locale;

import javax.tools.DiagnosticCollector;
import javax.tools.JavaCompiler;
import javax.tools.JavaCompiler.CompilationTask;
import javax.tools.JavaFileObject;
import javax.tools.StandardJavaFileManager;
import javax.tools.ToolProvider;

import org.apache.commons.io.FileUtils;
import org.junit.Test;

import com.examples.with.different.packagename.junit.Foo;

public class FooTestClassLoader {

	private static final String FOO_TEST_CLASS_NAME = "com.examples.with.different.packagename.junit.FooTest";

	@Test
	public void testFooTestClassCreation() throws IOException {
		Class<?> clazz = loadFooTestClass();
		assertNotNull(clazz);
	}

	private static String createFooTestJavaText() {
		StringBuffer buff = new StringBuffer();
		buff.append("package com.examples.with.different.packagename.junit;\n");
		buff.append("import static org.junit.Assert.assertEquals;\n");
		buff.append("import org.junit.Test;\n");
		buff.append("public class FooTest {\n");

		buff.append("	@Test\n");
		buff.append("	public void test1() {\n");
		buff.append("		Foo foo = new Foo();\n");
		buff.append("		int result = foo.add(10, 15);\n");
		buff.append("		assertEquals(25, result);\n");
		buff.append("	}\n");

		buff.append("	@Test\n");
		buff.append("	public void test2() {\n");
		buff.append("		Foo foo = new Foo();\n");
		buff.append("		int result = foo.add(20, 35);\n");
		buff.append("		assertEquals(55, result);\n");
		buff.append("	}\n");

		buff.append("	@Test \n");
		buff.append("	public void test3() {\n");
		buff.append("		Foo foo = new Foo();\n");
		buff.append("		int result = foo.add(10, 35);\n");
		buff.append("		assertEquals(46, result);\n");
		buff.append("	}\n");

		buff.append("}\n");

		return buff.toString();
	}

	private static File createNewTmpDir() {
		File dir = null;
		String dirName = FileUtils.getTempDirectoryPath() + File.separator
				+ "EvoSuite_" + JUnitResultBuilderTest.class.getCanonicalName()
				+ "_" + +System.currentTimeMillis();

		//first create a tmp folder
		dir = new File(dirName);
		if (!dir.mkdirs()) {
			return null;
		}

		if (!dir.exists()) {
			return null;
		}

		return dir;
	}

	public Class<?> loadFooTestClass() {

		File tempDir = createNewTmpDir();
		if (tempDir == null) {
			return null; //fail
		}

		String javaSrcDirName = tempDir.getAbsolutePath() + File.separator
				+ "src";

		String javaBinDirName = tempDir.getAbsolutePath() + File.separator
				+ "bin";

		String javaSrcPackageDirName = javaSrcDirName
				+ File.separator
				+ "com.examples.with.different.packagename.junit".replace(".",
						File.separator);

		String javaBinPackageDirName = javaBinDirName
				+ File.separator
				+ "com.examples.with.different.packagename.junit".replace(".",
						File.separator);

		File javaBinDir = new File(javaBinDirName);
		if (!javaBinDir.mkdirs()) {
			return null; //fail
		}

		File packageDir = new File(javaSrcPackageDirName);
		if (!packageDir.mkdirs()) {
			return null; //fail
		}

		String javaFilename = javaSrcPackageDirName + File.separator
				+ "FooTest.java";
		String classFilename = javaBinPackageDirName + File.separator
				+ "FooTest.class";

		String javaSourceText = createFooTestJavaText();
		File javaFile = writeJavaSourceText(javaSourceText, javaFilename);
		if (javaFile == null) {
			return null; //fail
		}

		boolean compiled = compileJavaFile(javaBinDirName, javaFile);
		if (!compiled) {
			return null; //fail
		}

		File classFile = new File(classFilename);
		if (!classFile.exists()) {
			return null; //fail
		}

		Class<?> clazz = loadClass(javaBinDir);
		if (clazz == null) {
			return null; //fail
		}

		//delete class file on exit
		classFile.delete();
		return clazz;
	}

	private static Class<?> loadClass(File javaBinDir) {

		URLClassLoader urlClassLoader = null;
		try {
			URI javaBinURI = javaBinDir.toURI();
			URL javaBinURL = javaBinURI.toURL();
			urlClassLoader = new URLClassLoader(new URL[] { javaBinURL },
					Foo.class.getClassLoader());
			Class<?> clazz = urlClassLoader.loadClass(FOO_TEST_CLASS_NAME);
			return clazz;
		} catch (ClassNotFoundException e) {
			return null;
		} catch (MalformedURLException e) {
			return null;
		}
	}

	private static boolean compileJavaFile(String javaBinDirName, File javaFile) {
		JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
		if (compiler == null) {
			return false; //fail
		}

		DiagnosticCollector<JavaFileObject> diagnostics = new DiagnosticCollector<JavaFileObject>();
		StandardJavaFileManager fileManager = compiler.getStandardFileManager(
				diagnostics, Locale.getDefault(), Charset.forName("UTF-8"));
		Iterable<? extends JavaFileObject> compilationUnits = fileManager
				.getJavaFileObjectsFromFiles(Collections
						.singletonList(javaFile));

		List<String> optionList;
		optionList = new ArrayList<String>();
		optionList.addAll(Arrays.asList("-d", javaBinDirName));
		CompilationTask task = compiler.getTask(null, fileManager, diagnostics,
				optionList, null, compilationUnits);
		boolean compiled = task.call();
		try {
			fileManager.close();
		} catch (IOException e) {
			return false;
		}
		return compiled;
	}

	private File writeJavaSourceText(String javaSourceText, String javaFilename) {
		File javaFile = new File(javaFilename);
		if (javaFile.exists()) {
			return null; //fail
		}

		BufferedWriter writer = null;
		try {
			writer = new BufferedWriter(new FileWriter(javaFilename));
			writer.write(javaSourceText);
			writer.close();
		} catch (IOException e) {
			return null;
		}
		return javaFile;
	}
}