content: /*
   *  This file is part of AndroidIDE.
   *
   *  AndroidIDE is free software: you can redistribute it and/or modify
   *  it under the terms of the GNU General Public License as published by
   *  the Free Software Foundation, either version 3 of the License, or
   *  (at your option) any later version.
   *
   *  AndroidIDE 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 General Public License for more details.
   *
   *  You should have received a copy of the GNU General Public License
   *   along with AndroidIDE.  If not, see <https://www.gnu.org/licenses/>.
   */
  
  /*
   * Copyright (C) 2014 The Android Open Source Project
   * Copyright (c) 2005, 2013, Oracle and/or its affiliates. All rights reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.  Oracle designates this
   * particular file as subject to the "Classpath" exception as provided
   * by Oracle in the LICENSE file that accompanied this code.
   *
   * This code 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 General Public License
   * version 2 for more details (a copy is included in the LICENSE file that
   * accompanied this code).
   *
   * You should have received a copy of the GNU General Public License version
   * 2 along with this work; if not, write to the Free Software Foundation,
   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
   * or visit www.oracle.com if you need additional information or have any
   * questions.
   */
  
  package com.itsaky.androidide.utils;
  
  import androidx.annotation.NonNull;
  import java.io.BufferedReader;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.InputStreamReader;
  import java.net.URL;
  import java.nio.charset.StandardCharsets;
  import java.util.ArrayList;
  import java.util.Enumeration;
  import java.util.Iterator;
  import java.util.LinkedHashMap;
  import java.util.List;
  import java.util.Map;
  import java.util.NoSuchElementException;
  import java.util.Objects;
  import java.util.Optional;
  import java.util.ServiceConfigurationError;
  
  /**
   * A simple service-provider loading facility. This class is an adaptation of the
   * {@link java.util.ServiceLoader ServiceLoader} to avoid the usage of {@link Class#newInstance()}
   * and use
   * {@link java.lang.reflect.Constructor#newInstance(Object...) Constructor.newInstance(Object...)}
   * for class instance creation.
   *
   * <p> A <i>service</i> is a well-known set of interfaces and (usually
   * abstract) classes.  A <i>service provider</i> is a specific implementation of a service.  The
   * classes in a provider typically implement the interfaces and subclass the classes defined in the
   * service itself.  Service providers can be installed in an implementation of the Java platform in
   * the form of extensions, that is, jar files placed into any of the usual extension directories.
   * Providers can also be made available by adding them to the application's class path or by some
   * other platform-specific means.
   *
   * <p> For the purpose of loading, a service is represented by a single type,
   * that is, a single interface or abstract class.  (A concrete class can be used, but this is not
   * recommended.)  A provider of a given service contains one or more concrete classes that extend
   * this <i>service type</i> with data and code specific to the provider.  The <i>provider class</i>
   * is typically not the entire provider itself but rather a proxy which contains enough information
   * to decide whether the provider is able to satisfy a particular request together with code that
   * can create the actual provider on demand. The details of provider classes tend to be highly
   * service-specific; no single class or interface could possibly unify them, so no such type is
   * defined here.  The only requirement enforced by this facility is that provider classes must have
   * a zero-argument constructor so that they can be instantiated during loading.
   *
   * <p><a name="format"> A service provider is identified by placing a
   * <i>provider-configuration file</i> in the resource directory
   * <tt>META-INF/services</tt>.</a>  The file's name is the fully-qualified <a
   * href="../lang/ClassLoader.html#name">binary name</a> of the service's type. The file contains a
   * list of fully-qualified binary names of concrete provider classes, one per line.  Space and tab
   * characters surrounding each name, as well as blank lines, are ignored.  The comment character is
   * <tt>'#'</tt> (<tt>'&#92;u0023'</tt>,
   * <font style="font-size:smaller;">NUMBER SIGN</font>); on
   * each line all characters following the first comment character are ignored. The file must be
   * encoded in UTF-8.
   *
   * <p> If a particular concrete provider class is named in more than one
   * configuration file, or is named in the same configuration file more than once, then the
   * duplicates are ignored.  The configuration file naming a particular provider need not be in the
   * same jar file or other distribution unit as the provider itself.  The provider must be accessible
   * from the same class loader that was initially queried to locate the configuration file; note that
   * this is not necessarily the class loader from which the file was actually loaded.
   *
   * <p> Providers are located and instantiated lazily, that is, on demand.  A
   * service loader maintains a cache of the providers that have been loaded so far.  Each invocation
   * of the {@link #iterator iterator} method returns an iterator that first yields all of the
   * elements of the cache, in instantiation order, and then lazily locates and instantiates any
   * remaining providers, adding each one to the cache in turn.  The cache can be cleared via the
   * {@link #reload reload} method.
   *
   * <p> Service loaders always execute in the security context of the caller.
   * Trusted system code should typically invoke the methods in this class, and the methods of the
   * iterators which they return, from within a privileged security context.
   *
   * <p> Instances of this class are not safe for use by multiple concurrent
   * threads.
   *
   * <p> Unless otherwise specified, passing a <tt>null</tt> argument to any
   * method in this class will cause a {@link NullPointerException} to be thrown.
   *
   * <p><span style="font-weight: bold; padding-right: 1em">Example</span>
   * Suppose we have a service type <tt>com.example.CodecSet</tt> which is intended to represent sets
   * of encoder/decoder pairs for some protocol.  In this case it is an abstract class with two
   * abstract methods:
   *
   * <blockquote><pre>
   * public abstract Encoder getEncoder(String encodingName);
   * public abstract Decoder getDecoder(String encodingName);</pre></blockquote>
   * <p>
   * Each method returns an appropriate object or <tt>null</tt> if the provider does not support the
   * given encoding.  Typical providers support more than one encoding.
   *
   * <p> If <tt>com.example.impl.StandardCodecs</tt> is an implementation of the
   * <tt>CodecSet</tt> service then its jar file also contains a file named
   *
   * <blockquote><pre>
   * META-INF/services/com.example.CodecSet</pre></blockquote>
   *
   * <p> This file contains the single line:
   *
   * <blockquote><pre>
   * com.example.impl.StandardCodecs    # Standard codecs</pre></blockquote>
   *
   * <p> The <tt>CodecSet</tt> class creates and saves a single service instance
   * at initialization:
   *
   * <blockquote><pre>
   * private static ServiceLoader&lt;CodecSet&gt; codecSetLoader
   *     = ServiceLoader.load(CodecSet.class);</pre></blockquote>
   *
   * <p> To locate an encoder for a given encoding name it defines a static
   * factory method which iterates through the known and available providers, returning only when it
   * has located a suitable encoder or has run out of providers.
   *
   * <blockquote><pre>
   * public static Encoder getEncoder(String encodingName) {
   *     for (CodecSet cp : codecSetLoader) {
   *         Encoder enc = cp.getEncoder(encodingName);
   *         if (enc != null)
   *             return enc;
   *     }
   *     return null;
   * }</pre></blockquote>
   *
   * <p> A <tt>getDecoder</tt> method is defined similarly.
   *
   * <p><span style="font-weight: bold; padding-right: 1em">Usage Note</span> If
   * the class path of a class loader that is used for provider loading includes remote network URLs
   * then those URLs will be dereferenced in the process of searching for provider-configuration
   * files.
   *
   * <p> This activity is normal, although it may cause puzzling entries to be
   * created in web-server logs.  If a web server is not configured correctly, however, then this
   * activity may cause the provider-loading algorithm to fail spuriously.
   *
   * <p> A web server should return an HTTP 404 (Not Found) response when a
   * requested resource does not exist.  Sometimes, however, web servers are erroneously configured to
   * return an HTTP 200 (OK) response along with a helpful HTML error page in such cases.  This will
   * cause a {@link ServiceConfigurationError} to be thrown when this class attempts to parse the HTML
   * page as a provider-configuration file.  The best solution to this problem is to fix the
   * misconfigured web server to return the correct response code (HTTP 404) along with the HTML error
   * page.
   *
   * @param <S> The type of the service to be loaded by this loader
   * @author Mark Reinhold
   * @since 1.6
   */
  public final class ServiceLoader<S> implements Iterable<S> {
  
    private static final String PREFIX = "META-INF/services/";
    // The class or interface representing the service being loaded
    private final Class<S> service;
    // The class loader used to locate, load, and instantiate providers
    private final ClassLoader loader;
    // The access control context taken when the ServiceLoader is created
    // Android-changed: do not use legacy security code.
    // private final AccessControlContext acc;
    // Cached providers, in instantiation order
    private final LinkedHashMap<String, S> providers = new LinkedHashMap<>();
    // The current lazy-lookup iterator
    private LazyIterator lookupIterator;
  
    /**
     * Clear this loader's provider cache so that all providers will be reloaded.
     *
     * <p> After invoking this method, subsequent invocations of the {@link
     * #iterator() iterator} method will lazily look up and instantiate providers from scratch, just
     * as is done by a newly-created loader.
     *
     * <p> This method is intended for use in situations in which new providers
     * can be installed into a running Java virtual machine.
     */
    public void reload() {
      providers.clear();
      lookupIterator = new LazyIterator(service, loader);
    }
  
    private ServiceLoader(Class<S> svc, ClassLoader cl) {
      service = Objects.requireNonNull(svc, "Service interface cannot be null");
      loader = (cl == null) ? ClassLoader.getSystemClassLoader() : cl;
      // Android-changed: Do not use legacy security code.
      // On Android, System.getSecurityManager() is always null.
      // acc = (System.getSecurityManager() != null) ? AccessController.getContext() : null;
      reload();
    }
  
    private static void fail(Class<?> service, String msg, Throwable cause)
      throws ServiceConfigurationError {
      throw new ServiceConfigurationError(service.getName() + ": " + msg, cause);
    }
  
    private static void fail(Class<?> service, String msg) throws ServiceConfigurationError {
      throw new ServiceConfigurationError(service.getName() + ": " + msg);
    }
  
    private static void fail(Class<?> service, URL u, int line, String msg)
      throws ServiceConfigurationError {
      fail(service, u + ":" + line + ": " + msg);
    }
  
    // Parse a single line from the given configuration file, adding the name
    // on the line to the names list.
    //
    private int parseLine(Class<?> service, URL u, BufferedReader r, int lc, List<String> names)
      throws IOException, ServiceConfigurationError {
      String ln = r.readLine();
      if (ln == null) {
        return -1;
      }
      int ci = ln.indexOf('#');
      if (ci >= 0) {
        ln = ln.substring(0, ci);
      }
      ln = ln.trim();
      int n = ln.length();
      if (n != 0) {
        if ((ln.indexOf(' ') >= 0) || (ln.indexOf('\t') >= 0)) {
          fail(service, u, lc, "Illegal configuration-file syntax");
        }
        int cp = ln.codePointAt(0);
        if (!Character.isJavaIdentifierStart(cp)) {
          fail(service, u, lc, "Illegal provider-class name: " + ln);
        }
        for (int i = Character.charCount(cp); i < n; i += Character.charCount(cp)) {
          cp = ln.codePointAt(i);
          if (!Character.isJavaIdentifierPart(cp) && (cp != '.')) {
            fail(service, u, lc, "Illegal provider-class name: " + ln);
          }
        }
        if (!providers.containsKey(ln) && !names.contains(ln)) {
          names.add(ln);
        }
      }
      return lc + 1;
    }
  
    // Parse the content of the given URL as a provider-configuration file.
    //
    // @param  service
    //         The service type for which providers are being sought;
    //         used to construct error detail strings
    //
    // @param  u
    //         The URL naming the configuration file to be parsed
    //
    // @return A (possibly empty) iterator that will yield the provider-class
    //         names in the given configuration file that are not yet members
    //         of the returned set
    //
    // @throws ServiceConfigurationError
    //         If an I/O error occurs while reading from the given URL, or
    //         if a configuration-file format error is detected
    //
    private Iterator<String> parse(Class<?> service, URL u) throws ServiceConfigurationError {
      InputStream in = null;
      BufferedReader r = null;
      ArrayList<String> names = new ArrayList<>();
      try {
        in = u.openStream();
        r = new BufferedReader(new InputStreamReader(in, StandardCharsets.UTF_8));
        int lc = 1;
  
        //noinspection StatementWithEmptyBody
        while ((lc = parseLine(service, u, r, lc, names)) >= 0);
  
      } catch (IOException x) {
        fail(service, "Error reading configuration file", x);
      } finally {
        try {
          if (r != null) {
            r.close();
          }
          if (in != null) {
            in.close();
          }
        } catch (IOException y) {
          fail(service, "Error closing configuration file", y);
        }
      }
      return names.iterator();
    }
  
    // Private inner class implementing fully-lazy provider lookup
    //
    private class LazyIterator implements Iterator<S> {
  
      Class<S> service;
      ClassLoader loader;
      Enumeration<URL> configs = null;
      Iterator<String> pending = null;
      String nextName = null;
  
      private LazyIterator(Class<S> service, ClassLoader loader) {
        this.service = service;
        this.loader = loader;
      }
  
      private boolean hasNextService() {
        if (nextName != null) {
          return true;
        }
        if (configs == null) {
          try {
            String fullName = PREFIX + service.getName();
            if (loader == null) {
              configs = ClassLoader.getSystemResources(fullName);
            } else {
              configs = loader.getResources(fullName);
            }
          } catch (IOException x) {
            fail(service, "Error locating configuration files", x);
          }
        }
        while ((pending == null) || !pending.hasNext()) {
          if (!configs.hasMoreElements()) {
            return false;
          }
          pending = parse(service, configs.nextElement());
        }
        nextName = pending.next();
        return true;
      }
  
      private S nextService() {
        if (!hasNextService()) {
          throw new NoSuchElementException();
        }
        String cn = nextName;
        nextName = null;
        Class<?> c = null;
        try {
          c = Class.forName(cn, false, loader);
        } catch (ClassNotFoundException x) {
          fail(service,
            // Android-changed: Let the ServiceConfigurationError have a cause.
            "Provider " + cn + " not found", x);
          // "Provider " + cn + " not found");
        }
        if (!service.isAssignableFrom(c)) {
          // Android-changed: Let the ServiceConfigurationError have a cause.
          ClassCastException cce = new ClassCastException(
            service.getCanonicalName() + " is not assignable from " + c.getCanonicalName());
          fail(service, "Provider " + cn + " not a subtype", cce);
        }
        try {
          S p = service.cast(c.getConstructor().newInstance());
          providers.put(cn, p);
          return p;
        } catch (Throwable x) {
          fail(service, "Provider " + cn + " could not be instantiated", x);
        }
        throw new Error();          // This cannot happen
      }
  
      public boolean hasNext() {
        // Android-changed: do not use legacy security code
        /* if (acc == null) { */
        return hasNextService();
              /*
              } else {
                  PrivilegedAction<Boolean> action = new PrivilegedAction<Boolean>() {
                      public Boolean run() { return hasNextService(); }
                  };
                  return AccessController.doPrivileged(action, acc);
              }
              */
      }
  
      public S next() {
        // Android-changed: do not use legacy security code
        /* if (acc == null) { */
        return nextService();
              /*
              } else {
                  PrivilegedAction<S> action = new PrivilegedAction<S>() {
                      public S run() { return nextService(); }
                  };
                  return AccessController.doPrivileged(action, acc);
              }
              */
      }
  
      public void remove() {
        throw new UnsupportedOperationException();
      }
    }
  
    /**
     * Lazily loads the available providers of this loader's service.
     *
     * <p> The iterator returned by this method first yields all of the
     * elements of the provider cache, in instantiation order.  It then lazily loads and instantiates
     * any remaining providers, adding each one to the cache in turn.
     *
     * <p> To achieve laziness the actual work of parsing the available
     * provider-configuration files and instantiating providers must be done by the iterator itself.
     * Its {@link java.util.Iterator#hasNext hasNext} and {@link java.util.Iterator#next next} methods
     * can therefore throw a {@link ServiceConfigurationError} if a provider-configuration file
     * violates the specified format, or if it names a provider class that cannot be found and
     * instantiated, or if the result of instantiating the class is not assignable to the service
     * type, or if any other kind of exception or error is thrown as the next provider is located and
     * instantiated.  To write robust code it is only necessary to catch
     * {@link ServiceConfigurationError} when using a service iterator.
     *
     * <p> If such an error is thrown then subsequent invocations of the
     * iterator will make a best effort to locate and instantiate the next available provider, but in
     * general such recovery cannot be guaranteed.
     * <blockquote style="font-size: smaller; line-height: 1.2"><span
     * style="padding-right: 1em; font-weight: bold">Design Note</span> Throwing an error in these
     * cases may seem extreme.  The rationale for this behavior is that a malformed
     * provider-configuration file, like a malformed class file, indicates a serious problem with the
     * way the Java virtual machine is configured or is being used.  As such it is preferable to throw
     * an error rather than try to recover or, even worse, fail silently.</blockquote>
     *
     * <p> The iterator returned by this method does not support removal.
     * Invoking its {@link java.util.Iterator#remove() remove} method will cause an
     * {@link UnsupportedOperationException} to be thrown.
     *
     * @return An iterator that lazily loads providers for this loader's service
     * @implNote When adding providers to the cache, the {@link #iterator Iterator} processes
     * resources in the order that the
     * {@link java.lang.ClassLoader#getResources(java.lang.String) ClassLoader.getResources(String)}
     * method finds the service configuration files.
     */
    @NonNull
    public Iterator<S> iterator() {
      return new Iterator<S>() {
        final Iterator<Map.Entry<String, S>> knownProviders = providers.entrySet().iterator();
  
        public boolean hasNext() {
          if (knownProviders.hasNext()) {
            return true;
          }
          return lookupIterator.hasNext();
        }
  
        public S next() {
          if (knownProviders.hasNext()) {
            return knownProviders.next().getValue();
          }
          return lookupIterator.next();
        }
  
        public void remove() {
          throw new UnsupportedOperationException();
        }
      };
    }
  
    /**
     * Creates a new service loader for the given service type and class loader.
     *
     * @param <S>     the class of the service type
     * @param service The interface or abstract class representing the service
     * @param loader  The class loader to be used to load provider-configuration files and provider
     *                classes, or <tt>null</tt> if the system class loader (or, failing that, the
     *                bootstrap class loader) is to be used
     * @return A new service loader
     */
    public static <S> ServiceLoader<S> load(Class<S> service, ClassLoader loader) {
      return new ServiceLoader<>(service, loader);
    }
  
    /**
     * Creates a new service loader for the given service type, using the current thread's
     * {@linkplain java.lang.Thread#getContextClassLoader context class loader}.
     *
     * <p> An invocation of this convenience method of the form
     *
     * <blockquote><pre>
     * ServiceLoader.load(<i>service</i>)</pre></blockquote>
     * <p>
     * is equivalent to
     *
     * <blockquote><pre>
     * ServiceLoader.load(<i>service</i>,
     *                    Thread.currentThread().getContextClassLoader())</pre></blockquote>
     *
     * @param <S>     the class of the service type
     * @param service The interface or abstract class representing the service
     * @return A new service loader
     */
    public static <S> ServiceLoader<S> load(Class<S> service) {
      ClassLoader cl = Thread.currentThread().getContextClassLoader();
      return ServiceLoader.load(service, cl);
    }
  
    /**
     * Creates a new service loader for the given service type, using the extension class loader.
     *
     * <p> This convenience method simply locates the extension class loader,
     * call it <tt><i>extClassLoader</i></tt>, and then returns
     *
     * <blockquote><pre>
     * ServiceLoader.load(<i>service</i>, <i>extClassLoader</i>)</pre></blockquote>
     *
     * <p> If the extension class loader cannot be found then the system class
     * loader is used; if there is no system class loader then the bootstrap class loader is used.
     *
     * <p> This method is intended for use when only installed providers are
     * desired.  The resulting service will only find and load providers that have been installed into
     * the current Java virtual machine; providers on the application's class path will be ignored.
     *
     * @param <S>     the class of the service type
     * @param service The interface or abstract class representing the service
     * @return A new service loader
     */
    public static <S> ServiceLoader<S> loadInstalled(Class<S> service) {
      ClassLoader cl = ClassLoader.getSystemClassLoader();
      ClassLoader prev = null;
      while (cl != null) {
        prev = cl;
        cl = cl.getParent();
      }
      return ServiceLoader.load(service, prev);
    }
    // BEGIN Android-added: loadFromSystemProperty(), for internal use.
    // Instantiates a class from a system property (used elsewhere in libcore).
  
    /**
     * Internal API to support built-in SPIs that check a system property first. Returns an instance
     * specified by a property with the class' binary name, or null if no such property is set.
     *
     * @hide
     */
    public static <S> S loadFromSystemProperty(final Class<S> service) {
      try {
        final String className = System.getProperty(service.getName());
        if (className != null) {
          Class<?> c = ClassLoader.getSystemClassLoader().loadClass(className);
          return (S) c.getConstructor().newInstance();
        }
        return null;
      } catch (Exception e) {
        throw new Error(e);
      }
    }
    // END Android-added: loadFromSystemProperty(), for internal use.
  
    /**
     * Load the first available service provider of this loader's service. This convenience method is
     * equivalent to invoking the {@link #iterator() iterator()} method and obtaining the first
     * element. It therefore returns the first element from the provider cache if possible, it
     * otherwise attempts to load and instantiate the first provider.
     *
     * <p> The following example loads the first available service provider. If
     * no service providers are located then it uses a default implementation.
     * <pre>{@code
     *    CodecFactory factory = ServiceLoader.load(CodecFactory.class)
     *                                        .findFirst()
     *                                        .orElse(DEFAULT_CODECSET_FACTORY);
     * }</pre>
     *
     * @return The first service provider or empty {@code Optional} if no service providers are
     * located
     * @throws ServiceConfigurationError If a provider class cannot be loaded for any of the reasons
     *                                   specified in the <a href="#errors">Errors</a> section above.
     * @since 9
     */
    public Optional<S> findFirst() {
      Iterator<S> iterator = iterator();
      if (iterator.hasNext()) {
        return Optional.of(iterator.next());
      } else {
        return Optional.empty();
      }
    }
  
    /**
     * Loads the first available service provider of this loader's service. Throws
     * {@link ServiceNotFoundException} if the service provider cannot be found.
     *
     * @return The first service provider.
     * @throws ServiceNotFoundException If no service provider is found for the service.
     * @see #findFirst()
     */
    public S findFirstOrThrow() throws ServiceNotFoundException {
      final var first = findFirst();
      if (first.isPresent()) {
        return first.get();
      }
      throw new ServiceNotFoundException(service);
    }
  
    /**
     * Returns a string describing this service.
     *
     * @return A descriptive string
     */
    public String toString() {
      return "java.util.ServiceLoader[" + service.getName() + "]";
    }
  }
  