/*
 * Copyright (c) 2011-2019 Contributors to the Eclipse Foundation
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License 2.0 which is available at
 * http://www.eclipse.org/legal/epl-2.0, or the Apache License, Version 2.0
 * which is available at https://www.apache.org/licenses/LICENSE-2.0.
 *
 * SPDX-License-Identifier: EPL-2.0 OR Apache-2.0
 */

package io.vertx.core.impl.verticle;

import io.vertx.core.impl.logging.Logger;
import io.vertx.core.impl.logging.LoggerFactory;

import javax.tools.Diagnostic;
import javax.tools.DiagnosticCollector;
import javax.tools.JavaCompiler;
import javax.tools.JavaFileObject;
import javax.tools.JavaFileObject.Kind;
import javax.tools.StandardJavaFileManager;
import javax.tools.StandardLocation;
import javax.tools.ToolProvider;
import java.io.File;
import java.net.URL;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

import static io.vertx.core.net.impl.URIDecoder.decodeURIComponent;

Classloader for dynamic .java source file compilation and loading.
Author:
Janne Hietamäki/**
 *
 * Classloader for dynamic .java source file compilation and loading.
 *
 * @author Janne Hietamäki
 */
public class CompilingClassLoader extends ClassLoader {

  private static final Logger log = LoggerFactory.getLogger(CompilingClassLoader.class);


  private static final String JAVA_COMPILER_OPTIONS_PROP_NAME = "vertx.javaCompilerOptions";
  private final static List<String> COMPILER_OPTIONS;

  static {
    String props = System.getProperty(JAVA_COMPILER_OPTIONS_PROP_NAME);
    if (props != null) {
      String[] array = props.split(",");
      List<String> compilerProps = new ArrayList<>(array.length);

      for (String prop :array) {
        compilerProps.add(prop.trim());
      }
      COMPILER_OPTIONS = Collections.unmodifiableList(compilerProps);
    } else {
      COMPILER_OPTIONS = null;
    }
  }

  private final JavaSourceContext javaSourceContext;
  private final MemoryFileManager fileManager;
  public CompilingClassLoader(ClassLoader loader, String sourceName) {
    super(loader);
    URL resource = getResource(sourceName);
    if (resource == null) {
      throw new RuntimeException("Resource not found: " + sourceName);
    }
    //Need to urldecode it too, since bug in JDK URL class which does not url decode it, so if it contains spaces you are screwed
    final File sourceFile = new File(decodeURIComponent(resource.getFile(), false));
    if (!sourceFile.canRead()) {
      throw new RuntimeException("File not found: " + sourceFile.getAbsolutePath() + " current dir is: " + new File(".").getAbsolutePath());
    }

    this.javaSourceContext = new JavaSourceContext(sourceFile);

    try {
      DiagnosticCollector<JavaFileObject> diagnostics = new DiagnosticCollector<>();
      JavaCompiler javaCompiler = ToolProvider.getSystemJavaCompiler();
      if (javaCompiler == null) {
        throw new RuntimeException("Unable to detect java compiler, make sure you're using a JDK not a JRE!");
      }
      StandardJavaFileManager standardFileManager = javaCompiler.getStandardFileManager(null, null, null);

      standardFileManager.setLocation(StandardLocation.SOURCE_PATH, Collections.singleton(javaSourceContext.getSourceRoot()));
      fileManager = new MemoryFileManager(loader, standardFileManager);

      // TODO - this needs to be fixed so it can compile classes from the classpath otherwise can't include
      // other .java resources from other modules

      JavaFileObject javaFile = standardFileManager.getJavaFileForInput(StandardLocation.SOURCE_PATH, resolveMainClassName(), Kind.SOURCE);
      JavaCompiler.CompilationTask task = javaCompiler.getTask(null, fileManager, diagnostics, COMPILER_OPTIONS, null, Collections.singleton(javaFile));
      boolean valid = task.call();
      if (valid) {
        for (Diagnostic<?> d : diagnostics.getDiagnostics()) {
          String code = d.getCode();
          if (code == null || (!code.startsWith("compiler.warn.annotation.method.not.found") &&
              !"compiler.warn.proc.processor.incompatible.source.version".equals(code))) {
            log.info(d);
          }
        }
      } else {
        for (Diagnostic<?> d : diagnostics.getDiagnostics()) {
          log.warn(d);
        }
        throw new RuntimeException("Compilation failed!");
      }
    } catch (Exception e) {
      throw new RuntimeException("Compilation failed", e);
    }
  }

  public String resolveMainClassName() {
    return javaSourceContext.getClassName();
  }

  @Override
  protected Class<?> findClass(String name) throws ClassNotFoundException {
    byte[] bytecode = getClassBytes(name);
    if (bytecode == null) {
      throw new ClassNotFoundException(name);
    }
    return defineClass(name, bytecode, 0, bytecode.length);
  }

  public byte[] getClassBytes(String name) {
    return fileManager.getCompiledClass(name);
  }
}