/* Copyright (c) 2014-2025. The SimGrid Team. All rights reserved.          */

/* This program is free software; you can redistribute it and/or modify it
 * under the terms of the license (GNU LGPL) which comes with this package. */

package org.simgrid.s4u;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.stream.Stream;

/**
 * Helper class loading the native functions of SimGrid that we use for downcalls
 *
 * This is loaded through a static block in org/simgrid/s4u/Engine.java
 */
public final class NativeLib {
  private static final boolean WINDOWS_OS = System.getProperty("os.name").toLowerCase().startsWith("win");
  private static boolean isNativeInited   = false;
  private static Path tempDir             = null; // where the embeeded libraries are unpacked before loading them

  /** A static-only "class" don't need no constructor */
  private NativeLib() { throw new IllegalAccessError("Utility class"); }

  /**
   * Hidden debug main() function
   *
   * It is not the Main-Class defined in src/bindings/java/MANIFEST.in (org.simgrid.msg.Msg is),
   * so it won't get executed by default. But that's helpful to debug linkage errors, if you
   * know that it exists. It's used by cmake during the configure, to inform the user.
   */
  public static void main(String[] args)
  {
    System.out.println("This jarfile searches the native code under: " + getPath());
  }

  /** Main function loading all the native classes that we need */
  public static void nativeInit()
  {
    if (isNativeInited)
      return;

    if (WINDOWS_OS)
      NativeLib.nativeInit("winpthread-1");

    NativeLib.nativeInit("simgrid");
    // If we can already use the bindings, their C code was merged into libsimgrid and we're good
    // If not, we need to load libsimgrid-java in addition
    try {
      simgridJNI.try_loading_some_symbols(1);
      // System.err.println("libsimgrid contains all of the Java bindings");
    } catch (java.lang.UnsatisfiedLinkError e) {
      // System.err.println("Loading libsimgrid-java");
      NativeLib.nativeInit("simgrid-java");
    }
    isNativeInited = true;

    /* Don't leak the files on disk */
    if (tempDir != null) {
      FileCleaner fclean = new FileCleaner(tempDir.toFile());
      fclean.run();
    }
  }

  /** Helper function trying to load one requested library */
  public static void nativeInit(String name)
  {
    Throwable cause = null;
    try {
      /* Prefer the version of the library bundled into the jar file and use it */
      if (loadLibAsStream(name))
        return;
    } catch (UnsatisfiedLinkError | SecurityException | IOException e) {
      cause = e;
    }

    /* If not found, try to see if we can find a version on disk */
    try {
      System.loadLibrary(name);
      return;
    } catch (UnsatisfiedLinkError systemException) {
      System.err.println(systemException);
    }

    System.err.println("\nCannot load the bindings to the '" + name + "'' library in path " + getPath() +
                       " and no usable SimGrid installation found on disk.");
    if (cause != null) {
      if (cause.getMessage().contains("libcgraph.so"))
        System.err.println("HINT: Try to install the libcgraph package (sudo apt-get install libcgraph).");
      else if (cause.getMessage().contains("libboost_context.so"))
        System.err.println(
            "HINT: Try to install the boost-context package (sudo apt-get install libboost-context-dev).");
      else
        System.err.println(
            "Try to install the missing dependencies, if any. Read carefully the following error message.");

      System.err.println();
      cause.printStackTrace();
    } else {
      System.err.println("This jar file does not seem to fit your system, and no usable SimGrid "
                         + "installation found on disk for " + name + ".");
    }
    System.exit(1);
  }

  /** Try to extract the library from the jarfile before loading it */
  private static boolean loadLibAsStream(String name) throws IOException, UnsatisfiedLinkError
  {
    String path = NativeLib.getPath();

    // We must write the lib onto the disk before loading it -- stupid operating systems
    if (tempDir == null) {
      final String tempPrefix = "simgrid-java-";

      if (WINDOWS_OS) {
        // The cleanup at exit fails on Windows where it is impossible to delete files which are still in
        // use.  Try to remove stale temporary files from previous executions, and limit disk usage.
        Path tmpdir = (new File(System.getProperty("java.io.tmpdir"))).toPath();
        try (Stream<Path> paths = Files.find(tmpdir, 1,
                                             (Path p, java.nio.file.attribute.BasicFileAttributes a)
                                                 -> a.isDirectory() && !p.equals(tmpdir) &&
                                                        p.getFileName().toString().startsWith(tempPrefix))) {
          paths.map(Path::toFile).map(FileCleaner::new).forEach(FileCleaner::run);
        }
      }

      tempDir = Files.createTempDirectory(tempPrefix);
    }

    /* For each possible filename of the given library on all possible OSes, try it */
    for (String filename : new String[] {name, "lib" + name + ".so",             /* linux */
                                         name + ".dll", "lib" + name + ".dll", /* windows (pure and mingw) */
                                         "lib" + name + ".dylib" /* macOS */}) {

      File fileOut = new File(tempDir.toFile(), filename);
      try ( // Try-with-resources. These stream will be autoclosed when needed.
          InputStream in = NativeLib.class.getClassLoader().getResourceAsStream(path + filename);) {
        if (in != null) {
          /* copy the library in position */
          Files.copy(in, fileOut.toPath());

          /* load that library */
          System.load(fileOut.getAbsolutePath());

          /* It loaded! we're good */
          return true;
        }
      }
    }

    /* No suitable name found */
    return false;
  }

  /** Find where to search for the library in the jar -- keep it aligned with where cmake puts it! */
  private static String getPath()
  {
    // Inspiration: https://github.com/xerial/snappy-java/blob/develop/src/main/java/org/xerial/snappy/OSInfo.java
    String prefix = "NATIVE";
    String os     = System.getProperty("os.name");
    String arch   = System.getProperty("os.arch");

    if (arch.matches("^i[3-6]86$"))
      arch = "x86";
    else if ("x86_64".equalsIgnoreCase(arch) || "AMD64".equalsIgnoreCase(arch))
      arch = "amd64";

    if (os.toLowerCase().startsWith("win")) {
      os = "Windows";
    } else if (os.contains("OS X")) {
      os = "Darwin";
    }
    os   = os.replace(' ', '_');
    arch = arch.replace(' ', '_');

    return prefix + "/" + os + "/" + arch + "/";
  }

  /** A hackish mechanism used to remove the file containing our library when the JVM shuts down */
  private static class FileCleaner implements Runnable {
    private File dir;
    public FileCleaner(File dir) { this.dir = dir; }
    @Override public void run()
    {
      try (Stream<Path> paths = Files.walk(dir.toPath())) {
        paths.sorted(java.util.Comparator.reverseOrder())
            .map(java.nio.file.Path::toFile)
            //.peek(System.err::println) // Prints what gets removed
            .forEach(java.io.File::delete);
      } catch (Exception e) {
        System.err.println("Error while cleaning temporary file " + dir.getAbsolutePath() + ": " + e.getCause());
        e.printStackTrace();
      }
    }
  }
}
