// Copyright 2010-2025 Google LLC
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package com.google.ortools;

import com.sun.jna.Platform;
import java.io.IOException;
import java.net.URI;
import java.net.URISyntaxException;
import java.net.URL;
import java.nio.file.FileSystem;
import java.nio.file.FileSystemAlreadyExistsException;
import java.nio.file.FileSystems;
import java.nio.file.FileVisitResult;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.SimpleFileVisitor;
import java.nio.file.attribute.BasicFileAttributes;
import java.util.AbstractMap;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.Objects;

/** Load native libraries needed for using ortools-java. */
public class Loader {
  private static final String RESOURCE_PATH = "ortools-" + Platform.RESOURCE_PREFIX + "/";

  /** Try to locate the native libraries directory. */
  private static URI getNativeResourceURI() throws IOException {
    ClassLoader loader = Loader.class.getClassLoader();
    URL resourceURL = loader.getResource(RESOURCE_PATH);
    Objects.requireNonNull(resourceURL,
        String.format("Resource %s was not found in ClassLoader %s", RESOURCE_PATH, loader));

    URI resourceURI;
    try {
      resourceURI = resourceURL.toURI();
    } catch (URISyntaxException e) {
      throw new IOException(e);
    }
    return resourceURI;
  }

  @FunctionalInterface
  private interface PathConsumer<T extends IOException> {
    void accept(Path path) throws T;
  }

  /**
   * Extract native resources in a temp directory.
   *
   * @param resourceURI Native resource location.
   * @return The directory path containing all extracted libraries.
   */
  private static Path unpackNativeResources(URI resourceURI) throws IOException {
    Path tempPath;
    tempPath = Files.createTempDirectory("ortools-java");
    tempPath.toFile().deleteOnExit();

    PathConsumer<?> visitor;
    visitor = (Path sourcePath) -> Files.walkFileTree(sourcePath, new SimpleFileVisitor<Path>() {
      @Override
      public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
        Path newPath = tempPath.resolve(sourcePath.getParent().relativize(file).toString());
        Files.copy(file, newPath);
        newPath.toFile().deleteOnExit();
        return FileVisitResult.CONTINUE;
      }

      @Override
      public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs)
          throws IOException {
        Path newPath = tempPath.resolve(sourcePath.getParent().relativize(dir).toString());
        Files.copy(dir, newPath);
        newPath.toFile().deleteOnExit();
        return FileVisitResult.CONTINUE;
      }
    });

    FileSystem fs;
    try {
      fs = FileSystems.newFileSystem(resourceURI, Collections.emptyMap());
    } catch (FileSystemAlreadyExistsException e) {
      fs = FileSystems.getFileSystem(resourceURI);
      if (fs == null) {
        throw new IllegalArgumentException();
      }
    }
    Path p = fs.provider().getPath(resourceURI);
    visitor.accept(p);
    return tempPath;
  }

  /** Unpack and Load the native libraries needed for using ortools-java. */
  private static boolean loaded = false;

  public static synchronized void loadNativeLibraries() {
    // prints the name of the Operating System
    // System.out.println("OS: " + System.getProperty("os.name"));
    if (loaded) {
      return;
    }
    try {
      // System.out.println("System.loadLibrary(\"jniortools\")");
      System.loadLibrary("jniortools");
      loaded = true;
      return;
    } catch (UnsatisfiedLinkError e) {
      // Do nothing.
      // System.out.println("Can't System.loadLibrary(jniortools)");
    }
    try {
      URI resourceURI = getNativeResourceURI();
      Path tempPath = unpackNativeResources(resourceURI);
      // Load the native library
      // System.out.println("System.load(" + System.mapLibraryName("jniortools") + ")");
      System.load(tempPath.resolve(RESOURCE_PATH)
              .resolve(System.mapLibraryName("jniortools"))
              .toAbsolutePath()
              .toString());
      loaded = true;
      return;
    } catch (IOException | UnsatisfiedLinkError e) {
      // Do nothing.
      // System.out.println("Can't System.load(jniortools)");
    }

    // On windows, try to load each libraries one by one.
    // System.out.println("Prefix: " + Platform.RESOURCE_PREFIX);
    if (Platform.RESOURCE_PREFIX.equals("win32-x86-64")) {
      try {
        URI resourceURI = getNativeResourceURI();
        Path tempPath = unpackNativeResources(resourceURI);
        // libraries order does matter <LibraryName, isMandatory> !
        List<Map.Entry<String, Boolean>> dlls =
            Arrays.asList((new AbstractMap.SimpleEntry("zlib1", true)),
                (new AbstractMap.SimpleEntry("bz2", true)),
                (new AbstractMap.SimpleEntry("abseil_dll", true)),
                (new AbstractMap.SimpleEntry("re2", true)),
                (new AbstractMap.SimpleEntry("libutf8_validity", true)),
                (new AbstractMap.SimpleEntry("libprotobuf", true)),
                (new AbstractMap.SimpleEntry("highs", false)),
                (new AbstractMap.SimpleEntry("libscip", false)),
                (new AbstractMap.SimpleEntry("ortools", true)),
                (new AbstractMap.SimpleEntry("jniortools", true)));

        for (Map.Entry<String, Boolean> dll : dlls) {
          try {
            // System.out.println("System.load(" + dll.getKey() + ")");
            System.load(tempPath.resolve(RESOURCE_PATH)
                    .resolve(System.mapLibraryName(dll.getKey()))
                    .toAbsolutePath()
                    .toString());
          } catch (UnsatisfiedLinkError e) {
            System.out.println("System.load(" + dll.getKey() + ") failed!");
            if (dll.getValue()) {
              throw new RuntimeException(e);
            }
          }
        }
        loaded = true;
        return;
      } catch (IOException e) {
        // Do nothing.
        // System.out.println("unpack failed");
      }
    }
  }
}