import $ivy.`com.github.rockjam::license-headers:0.0.1`


import mill._, scalalib._
import mill.eval.PathRef
import de.heikoseeberger.sbtheader.{CommentStyle, FileType, HeaderCreator, License}

trait Headers extends ScalaModule {

  val headerMappings = Map(
    FileType.scala.extension -> (FileType.scala, CommentStyle.cStyleBlockComment),
    FileType.java.extension -> (FileType.java, CommentStyle.cStyleBlockComment)
  )

  val license = {
    val currentYear = java.time.Year.now(java.time.Clock.systemUTC).getValue
    License.Custom(
      s"Copyright (C) 2009-$currentYear Lightbend Inc. <https://www.lightbend.com>"
    )
  }

  def headerCreate() = T.command {
    val withoutHeaders = filesWithoutHeaders(sources() ++ resources())

    val updatedFiles = withoutHeaders.map {
      case (file, updated) =>
        os.write.over(file, updated)
        file
    }

    if (updatedFiles.nonEmpty) {
      T.ctx.log.info(
        s"Headers created for ${updatedFiles.size} files:\n${updatedFiles.mkString("\n")}")
    }
    updatedFiles
  }

  def headerCheck() = T.command {
    val withoutHeaders = filesWithoutHeaders(sources() ++ resources()).map(_._1)

    if (withoutHeaders.nonEmpty) {
      sys.error(
        s"There are files without headers!\n${withoutHeaders.mkString("\n")}"
      )
    }
  }

  private def filesWithoutHeaders(input: Seq[PathRef]) = {
    for {
      ref <- input if os.exists(ref.path)
      file <- os.walk(ref.path) if os.isFile(file)
      (fileType, commentStyle) <- headerMappings.get(file.ext)
      updatedContent <- HeaderCreator(
        fileType,
        commentStyle,
        license,
        log = _ => (),
        os.read.inputStream(file)
      ).createText
    } yield file -> updatedContent
  }

}