import java.util.concurrent.Callable

apply plugin: SourceGenerationPlugin

/**
 * A plugin for dealing with AnnotationProcessor-based source generation.
 * <p/>
 * Creates (or reuses) a grouping task named `generateSources` which is responsible
 * for coordinating (via task deps) the running of all source-generation tasks.
 * <p/>
 * Additionally a grouping task is created for each SourceSet to hold the generation
 * task for that SourceSet.  This task is named following the `run{SourceSet.name}SourceGenerators`.
 * This task is also injected into the SourceSet as `sourceGeneratorsTask` for scripts to access
 */
class SourceGenerationPlugin implements Plugin<Project> {
	public static final String GROUP = "sourceGeneration";
	public static final String GENERATE_SOURCES_TASK_NAME = "generateSources";

	@Override
	public void apply(Project project) {
		final JavaPluginConvention javaPluginConvention = project.getConvention().findPlugin( JavaPluginConvention.class );
		if ( javaPluginConvention == null ) {
			// something seriously awry
			return;
		}

		project.convention.plugins[GROUP] = new SourceGenerationPluginConvention( project );

		// first set up the overall generateSources task
		Task generateSourcesTask = project.getTasks().findByName( GENERATE_SOURCES_TASK_NAME );
		if ( generateSourcesTask == null ) {
			generateSourcesTask = project.getTasks().create( GENERATE_SOURCES_TASK_NAME );
			generateSourcesTask.setGroup( GROUP );
			generateSourcesTask.setDescription( "Grouping task for all source generation tasks" );
		}

		// for each source set, define the specific grouping tasks (and associate with the generateSources as a
		// task dependency)
		for ( SourceSet sourceSet : javaPluginConvention.getSourceSets() ) {
			final ExtraPropertiesExtension extProps = ( (ExtensionAware) sourceSet ).getExtensions().getExtraProperties();

			// find the main javac task for this sourceSet (so we can add dependsOn to it)
			final JavaCompile javaCompileTask = (JavaCompile) project.getTasks().getByName( sourceSet.getCompileJavaTaskName() );

			// create the pre-apt generation grouping task
			final String sourceGeneratorsTaskName = sourceSet.getTaskName( "run", "sourceGenerators" );
			final Task sourceGeneratorsTask = project.getTasks().create( sourceGeneratorsTaskName );
			sourceGeneratorsTask.setGroup( GROUP );
			sourceGeneratorsTask.setDescription(
					String.format(
							"Grouping task for running all source generation tasks for the %s source-set of the %s project",
							sourceSet.getName(),
							project.getName()
					)
			);
			generateSourcesTask.dependsOn( sourceGeneratorsTask );
			javaCompileTask.dependsOn( sourceGeneratorsTask );

			final File aptDir = new File( new File( project.getBuildDir(), "generated-src/apt" ), sourceSet.name );
			javaCompileTask.options.compilerArgs += [ "-s", aptDir.absolutePath ];
			javaCompileTask.doFirst({
				if ( !aptDir.exists() ) {
					if ( !aptDir.mkdirs() ) {
						project.logger.warn( "Unable to create APT dir : " + aptDir.absolutePath )
					}
				}
			})

			generateSourcesTask.dependsOn( javaCompileTask )

			extProps.set( "sourceGeneratorsTask", sourceGeneratorsTask );
			extProps.set( "aptDir", aptDir );
		}
	}
}

class SourceGenerationPluginConvention {
	public static final String METAGEN_DEPENDENCY_CONFIG_NAME = "hibernateJpaModelGenTool";
	public static final String METAGEN_PROCESSOR_NAME = "org.hibernate.jpamodelgen.JPAMetaModelEntityProcessor";

	private final Project project;

	// practicality says we only ever deal with 2 source-sets:
	private JavaCompile mainProcOnlyTask;
	private JavaCompile testProcOnlyTask;

	SourceGenerationPluginConvention(Project project) {
		this.project = project
	}

	/**
	 * Exposed to the build scripts to be able to apply JPA Metamodel Generation support to the
	 * SourceSet it specifies.
	 *
	 * @param sourceSet The SourceSet to which JPA Metamodel Generation support should be applied.
	 */
	public void addMetaGenProcessor(SourceSet sourceSet) {
		if ( sourceSet.name.equals( "main" ) ) {
			if ( mainProcOnlyTask == null ) {
				mainProcOnlyTask = generateProcessorOnlyTask( sourceSet )
			}
		}
		else if ( sourceSet.name.equals( "test" ) ) {
			if ( testProcOnlyTask == null ) {
				testProcOnlyTask = generateProcessorOnlyTask( sourceSet )
			}
		}
		else {
			throw new IllegalArgumentException( "SourceSet (" + sourceSet.name + ") not valid for source generation" )
		}
	}

	private JavaCompile generateProcessorOnlyTask(SourceSet sourceSet) {
		final File targetDir = sourceSet.aptDir;

		// find the main javac task for this sourceSet (we will alter it a bit later on)
		final JavaCompile javaCompileTask = (JavaCompile) project.getTasks().getByName( sourceSet.getCompileJavaTaskName() );

		final ExtraPropertiesExtension extProps = ( (ExtensionAware) sourceSet ).getExtensions().getExtraProperties();

		final String aptTaskName = sourceSet.getTaskName( "run", "annotationProcessors" );
//		final AnnotationProcessorOnlyTask aptTask = project.getTasks().create( aptTaskName, AnnotationProcessorOnlyTask.class );
		final JavaCompile aptTask = project.getTasks().create( aptTaskName, JavaCompile.class );
		aptTask.options.compilerArgs += [
				"-nowarn",
				"-proc:only",
				"-encoding", "UTF-8",
				"-s", targetDir.getAbsolutePath(),
				"-processor", METAGEN_PROCESSOR_NAME
		]

		aptTask.setGroup( SourceGenerationPlugin.GROUP );
		aptTask.setDescription(
				String.format(
						"Grouping task for running all AnnotationProcessors (javac -proc:only) for the %s sourceSet of the %s project",
						sourceSet.getName(),
						project.getName()
				)
		);

		// sourceSet.getAllJava() returns a SourceDirectorySet which is a "live view" meaning it keeps expanding
		// even as we add to it.  The problem is that later on here we will add the output directory of this task
		// to this SourceDirectorySet; we need to make sure that we use the view of the SourceDirectorySet *before* that
		// happens as the source for this task.  getSrcDirs() does that
		aptTask.source( sourceSet.getAllJava() )
		aptTask.destinationDir = targetDir

		aptTask.setSourceCompatibility( javaCompileTask.getSourceCompatibility() );
		aptTask.setTargetCompatibility( javaCompileTask.getTargetCompatibility() );
		aptTask.setDependencyCacheDir( javaCompileTask.getDependencyCacheDir() );

		aptTask.getConventionMapping().map(
				"classpath",
				new Callable<FileCollection>() {
					public FileCollection call() throws Exception {
						return javaCompileTask.getClasspath() + project.configurations[METAGEN_DEPENDENCY_CONFIG_NAME]
					}
				}
		);

		aptTask.mustRunAfter( extProps.get( "sourceGeneratorsTask" ) );
		javaCompileTask.dependsOn( aptTask );
		project.tasks.findByName( SourceGenerationPlugin.GENERATE_SOURCES_TASK_NAME ).dependsOn( aptTask )

		// Add the APT output dir to the source set
		// 		- so that the generated sources get compiled during main javac
		sourceSet.getJava().srcDir( targetDir );
		return aptTask
	}
}