
/*
 * Janino - An embedded Java[TM] compiler
 *
 * Copyright (c) 2001-2010 Arno Unkrig. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification, are permitted provided that the
 * following conditions are met:
 *
 *    1. Redistributions of source code must retain the above copyright notice, this list of conditions and the
 *       following disclaimer.
 *    2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the
 *       following disclaimer in the documentation and/or other materials provided with the distribution.
 *    3. Neither the name of the copyright holder nor the names of its contributors may be used to endorse or promote
 *       products derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package org.codehaus.commons.compiler;

import java.io.InputStream;
import java.net.URL;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.List;
import java.util.Properties;

import org.codehaus.commons.nullanalysis.Nullable;

/**
 * Utility class that finds implementations of {@link ICompilerFactory}s.
 */
public final
class CompilerFactoryFactory {

    private CompilerFactoryFactory() {}

    @Nullable private static ICompilerFactory defaultCompilerFactory;

    /**
     * Equivalent with {@code getDefaultCompilerFactory(Thread.currentThread().getContextClassLoader())}.
     * The context class loader is typically a bad choice, because frameworks use (abuse?) the context class loader
     * for different purposes, which causes problems in individual contexts.
     *
     * @deprecated Use {@link #getDefaultCompilerFactory(ClassLoader)} instead
     * @see        <a href="https://stackoverflow.com/a/36228195">Context class loaders are for cases where you forgot
     *             to pass an explicit class loader parameter</a>
     */
    @Deprecated public static ICompilerFactory
    getDefaultCompilerFactory() throws Exception {
        return CompilerFactoryFactory.getDefaultCompilerFactory(Thread.currentThread().getContextClassLoader());
    }

    /**
     * Finds the first implementation of {@code org.codehaus.commons.compiler} through the <var>classLoader</var>, then
     * loads and instantiates the implementation's {@link ICompilerFactory}.
     * <p>
     *   If the implementation is on the application class path (which is the case for probably 99% of all
     *   environments), then the correct class loader to use would be {@link ClassLoader#getSystemClassLoader()}.
     * </p>
     *
     * @return           The {@link ICompilerFactory} of the first implementation that was loaded
     * @throws Exception Many things can go wrong while finding and initializing the default compiler factory
     */
    public static ICompilerFactory
    getDefaultCompilerFactory(ClassLoader classLoader) throws Exception {

        if (CompilerFactoryFactory.defaultCompilerFactory != null) {
            return CompilerFactoryFactory.defaultCompilerFactory;
        }

        Properties properties;
        {
            InputStream is = classLoader.getResourceAsStream("org.codehaus.commons.compiler.properties");
            if (is == null) {
                throw new ClassNotFoundException(
                    "No implementation of org.codehaus.commons.compiler could be loaded."
                    + " Typically, you'd have  \"janino.jar\", or \"commons-compiler-jdk.jar\","
                    + " or both on the classpath, and use the \"ClassLoader.getSystemClassLoader\" to load them."
                );
            }
            try {
                properties = new Properties();
                properties.load(is);
            } finally {
                is.close();
            }
        }

        String compilerFactoryClassName = properties.getProperty("compilerFactory");

        return (
            CompilerFactoryFactory.defaultCompilerFactory
            = CompilerFactoryFactory.getCompilerFactory(compilerFactoryClassName)
        );
    }

    /**
     * Equivalent with {@code getAllCompilerFactories(Thread.currentThread().getContextClassLoader())}.
     * The context class loader is typically a bad choice, because frameworks use (abuse?) the context class loader
     * for different purposes, which causes problems in individual contexts.
     *
     * @deprecated Use {@link #getAllCompilerFactories(ClassLoader)} instead
     * @see        <a href="https://stackoverflow.com/a/36228195">Context class loaders are for cases where you forgot
     *             to pass an explicit class loader parameter</a>
     */
    @Deprecated public static ICompilerFactory[]
    getAllCompilerFactories() throws Exception {
        return CompilerFactoryFactory.getAllCompilerFactories(Thread.currentThread().getContextClassLoader());
    }

    /**
     * Finds all implementation of {@code org.codehaus.commons.compiler} through the <var>classLoader</var>, then loads
     * and instantiates the implementations' {@link ICompilerFactory}s.
     * <p>
     *   If the implementations are on the application class path (which is the case for probably 99% of all
     *   environments), then the correct class loader to use would be {@link ClassLoader#getSystemClassLoader()}.
     * </p>
     *
     * @return           The {@link ICompilerFactory}s of all implementations that were loaded
     * @throws Exception Many things can go wrong while finding and initializing the default compiler factory
     */
    public static ICompilerFactory[]
    getAllCompilerFactories(ClassLoader classLoader) throws Exception {

        List<ICompilerFactory> factories = new ArrayList<ICompilerFactory>();
        for (Enumeration<URL> en = classLoader.getResources("org.codehaus.commons.compiler.properties"); en.hasMoreElements();) {
            URL url = (URL) en.nextElement();

            Properties properties;
            {
                properties = new Properties();
                InputStream is = url.openStream();
                try {
                    properties.load(is);
                } finally {
                    is.close();
                }
            }

            String compilerFactoryClassName = properties.getProperty("compilerFactory");
            if (compilerFactoryClassName == null) {
                throw new IllegalStateException(url.toString() + " does not specify the 'compilerFactory' property");
            }

            factories.add(CompilerFactoryFactory.getCompilerFactory(compilerFactoryClassName));
        }
        return (ICompilerFactory[]) factories.toArray(new ICompilerFactory[factories.size()]);
    }

    /**
     * Equivalent with {@link #getCompilerFactory(String, ClassLoader)
     * getCompilerFactory(Thread.currentThread().getContextClassLoader())}.
     * <p>
     *   If the implementation is on the application class path (which is the case for probably 99% of all
     *   environments), then the correct class loader to use would be {@link ClassLoader#getSystemClassLoader()}.
     * </p>
     *
     * @param compilerFactoryClassName Name of a class that implements {@link ICompilerFactory}
     * @throws Exception               Many things can go wrong while finding and initializing the default compiler
     *                                 factory
     */
    @Deprecated public static ICompilerFactory
    getCompilerFactory(String compilerFactoryClassName) throws Exception {
        return CompilerFactoryFactory.getCompilerFactory(
            compilerFactoryClassName,
            Thread.currentThread().getContextClassLoader()
        );
    }

    /**
     * Loads an {@link ICompilerFactory} implementation by class name.
     * <p>
     *   If the implementation is on the application class path (which is the case for probably 99% of all
     *   environments), then the correct class loader to use would be {@link ClassLoader#getSystemClassLoader()}.
     * </p>
     *
     * @param compilerFactoryClassName Name of a class that implements {@link ICompilerFactory}
     * @throws Exception               Many things can go wrong while loading and initializing the default compiler
     *                                 factory
     */
    public static ICompilerFactory
    getCompilerFactory(String compilerFactoryClassName, ClassLoader classLoader) throws Exception {
        return (ICompilerFactory) classLoader.loadClass(compilerFactoryClassName).newInstance();
    }

    /**
     * @return The version of the commons-compiler specification, or {@code null}
     */
    public static String
    getSpecificationVersion() {
        return CompilerFactoryFactory.class.getPackage().getSpecificationVersion();
    }
}
