import java.nio.file.Files

for (def sourceSet in [sourceSets.main, sourceSets.client]) {
	// We have to capture the source set name for the lazy string literals,
	// otherwise it'll just be whatever the last source set is in the list.
	def sourceSetName = sourceSet.name
	def taskName = sourceSet.getTaskName('generate', 'ImplPackageInfos')
	def task = tasks.register(taskName, GenerateImplPackageInfos) {
		group = 'fabric'
		description = "Generates package-info files for $sourceSetName implementation packages."

		// Only apply to default source directory since we also add the generated
		// sources to the source set.
		sourceRoot = file("src/$sourceSetName/java")
		header = rootProject.file('HEADER')
		outputDir = file("src/generated/$sourceSetName")
	}
	sourceSet.java.srcDir task

	def cleanTask = tasks.register(sourceSet.getTaskName('clean', 'ImplPackageInfos'), Delete) {
		group = 'fabric'
		delete file("src/generated/$sourceSetName")
	}
	clean.dependsOn cleanTask
}

class GenerateImplPackageInfos extends DefaultTask {
	@InputFile
	File header

	@SkipWhenEmpty
	@InputDirectory
	final DirectoryProperty sourceRoot = project.objects.directoryProperty()

	@OutputDirectory
	final DirectoryProperty outputDir = project.objects.directoryProperty()

	@TaskAction
	def run() {
		def output = outputDir.get().asFile.toPath()
		output.deleteDir()
		def headerText = header.readLines().join("\n") // normalize line endings
		def root = sourceRoot.get().asFile.toPath()

		for (def dir in ['impl', 'mixin']) {
			def implDir = root.resolve("net/fabricmc/fabric/$dir")

			if (Files.notExists(implDir)) {
				continue
			}

			implDir.eachDirRecurse {
				def containsJava = Files.list(it).any {
					Files.isRegularFile(it) && it.fileName.toString().endsWith('.java')
				}

				if (containsJava && Files.notExists(it.resolve('package-info.java'))) {
					def relativePath = root.relativize(it)
					def target = output.resolve(relativePath)
					Files.createDirectories(target)

					target.resolve('package-info.java').withWriter {
						def packageName = relativePath.toString().replace(File.separator, '.')
						it.write("""$headerText
						|/**
						| * Implementation code for ${project.name}.
						| */
						|@ApiStatus.Internal
						|package $packageName;
						|
						|import org.jetbrains.annotations.ApiStatus;
						|""".stripMargin())
					}
				}
			}
		}
	}
}