generateInstructions.sbt

val generateInstallInstructions = taskKey[Unit]("Generate instructions in README.md")

generateInstallInstructions := {
  val info =
    Def.task((projectID.value, cssDslConfig.value, (publish / skip).value))
      .all(ScopeFilter(inAnyProject -- inProjects(ThisProject))).value
      .collect { case (id, cfg, false) =>
        (id,
          id.name.split('_') match {
            case Array(p, s) => (p, s)
          },
          cfg)
      }
      .sortBy(_._2)(Ordering.Tuple2(Ordering.String, Ordering.String.reverse))

  def mdTable(head: Seq[String], rows: Seq[Seq[String]]) = {
    val widths =
      (head.map(_.length) +: rows.map(_.map(_.length))).transpose.map(_.max)
        .zipWithIndex.map(_.swap).toMap.withDefaultValue(0)
    def row(xs: Seq[String]) =
      xs.zipWithIndex.map { case (s, i) => s.padTo(widths(i), ' ') }.mkString("| ", " | ", " |\n")
    row(head) +
      widths.values.map("-" * _).mkString("|-", "-|-", "-|\n") +
      rows.map(row).mkString
  }

  def markerText(side: String) = s"<!-- $side autogenerated via sbt generateInstallInstructions -->"

  val artifactsTable = mdTable(List("CSS library", "Scala DOM library", "SBT Module ID"), info.map {
    case (moduleId, (_, moduleNameSuffix), config) =>
      val (op, library) = moduleNameSuffix match {
        case "scalatags"    => "%%" -> "`scalatags.Text` (JVM)"
        case "scalajsreact" => "%%%" -> "scalajs-react (scala.js)"
      }
      List(
        config.name,
        library,
        s"""`"${moduleId.organization}" $op "${moduleId.name}" % "${moduleId.revision}"`"""
      )
  })

  val importsTable =
    mdTable(
      List("CSS library", "Prefix", "Import"),
      info.flatMap { case (_, _, cfg) =>
        cfg.prefixes.map { p =>
          List(
            cfg.name,
            p.fold("None")("`" + _ + "`"),
            "`import cssdsl." + cfg.scalaPackage + "." + p.fold("")(_.capitalize) + "Dsl._`"
          )
        }
      }.distinct
    )

  val block =
    s""">${markerText("Begin")}
        >
        >#### Artifact
        >
        >$artifactsTable
        >
        >### Import
        >
        >$importsTable
        >
        >${markerText("End")}
        >""".stripMargin('>')

  val readmeFile = baseDirectory.value / "README.md"
  val currentReadme = IO.readLines(readmeFile)
  val (before, rest) = currentReadme.span(_.trim != markerText("Begin"))
  val after = rest.reverse.takeWhile(_.trim != markerText("End")).reverse
  val newReadme = before.map(_ + "\n").mkString + block + after.map(_ + "\n").mkString
  IO.write(readmeFile, newReadme)
}