/*
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you 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 org.apache.maven.plugins.jar;
  
  import javax.inject.Named;
  import javax.inject.Singleton;
  
  import java.io.BufferedReader;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.InputStreamReader;
  import java.io.UncheckedIOException;
  import java.nio.file.Path;
  import java.nio.file.Paths;
  import java.util.HashMap;
  import java.util.Map;
  import java.util.Optional;
  
  import org.apache.maven.toolchain.Toolchain;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * Component provided JDK specification based on toolchains.
   */
  @Named
  @Singleton
  class ToolchainsJdkSpecification {
  
      private final Logger logger = LoggerFactory.getLogger(ToolchainsJdkSpecification.class);
  
      private final Map<Path, String> cache = new HashMap<>();
  
      public synchronized Optional<String> getJDKSpecification(Toolchain toolchain) {
          Optional<Path> javacPath = getJavacPath(toolchain);
          return javacPath.map(path -> cache.computeIfAbsent(path, this::getSpecForPath));
      }
  
      private Optional<Path> getJavacPath(Toolchain toolchain) {
          return Optional.ofNullable(toolchain.findTool("javac")).map(Paths::get).map(this::getCanonicalPath);
      }
  
      private Path getCanonicalPath(Path path) {
          try {
              return path.toRealPath();
          } catch (IOException e) {
              if (path.getParent() != null) {
                  return getCanonicalPath(path.getParent()).resolve(path.getFileName());
              } else {
                  throw new UncheckedIOException(e);
              }
          }
      }
  
      private String getSpecForPath(Path path) {
          try {
              ProcessBuilder processBuilder = new ProcessBuilder(path.toString(), "-version");
              processBuilder.redirectErrorStream(true);
              Process process = processBuilder.start();
              String version = readOutput(process.getInputStream()).trim();
              process.waitFor();
  
              if (version.startsWith("javac ")) {
                  version = version.substring(6);
                  if (version.startsWith("1.")) {
                      version = version.substring(0, 3);
                  } else {
                      version = version.substring(0, 2);
                  }
                  return version;
              } else {
                  logger.warn("Unrecognized output from {}: {}", processBuilder.command(), version);
              }
          } catch (IndexOutOfBoundsException | IOException e) {
              logger.warn("Failed to execute: {} - {}", path, e.getMessage());
          } catch (InterruptedException e) {
              Thread.currentThread().interrupt();
          }
  
          return null;
      }
  
      private String readOutput(InputStream inputstream) throws IOException {
         BufferedReader br = new BufferedReader(new InputStreamReader(inputstream));
 
         StringBuilder output = new StringBuilder();
         String line;
         while ((line = br.readLine()) != null) {
             output.append(line + System.lineSeparator());
         }
 
         return output.toString();
     }
 }