package sbt

import Types.const
import java.io.File

/**
 * Represents how settings from various sources are automatically merged into a Project's settings.
 * This only configures per-project settings and not global or per-build settings.
 */
sealed abstract class AddSettings

object AddSettings {
  private[sbt] final class Sequence(val sequence: Seq[AddSettings]) extends AddSettings
  private[sbt] final object User extends AddSettings
  private[sbt] final class Plugins(val include: Plugin => Boolean) extends AddSettings
  private[sbt] final class AutoPlugins(val include: AutoPlugin => Boolean) extends AddSettings
  private[sbt] final class DefaultSbtFiles(val include: File => Boolean) extends AddSettings
  private[sbt] final class SbtFiles(val files: Seq[File]) extends AddSettings
  private[sbt] final object BuildScalaFiles extends AddSettings

  /** Adds all settings from autoplugins. */
  val autoPlugins: AddSettings = new AutoPlugins(const(true)) // Note: We do not expose fine-grained autoplugins because
  // it's dangerous to control at that level right now.
  // Leaving the hook in place in case we need to expose
  // it, but most likely it will remain locked out
  // for users with an alternative ordering feature
  // in place.

  /** Settings specified in Build.scala `Project` constructors. */
  val buildScalaFiles: AddSettings = BuildScalaFiles

  /** All plugins that aren't auto plugins. */
  val nonAutoPlugins: AddSettings = plugins(const(true))

  /** Adds all settings from a plugin to a project. */
  val allPlugins: AddSettings = seq(autoPlugins, nonAutoPlugins)

  /** Allows the plugins whose names match the `names` filter to automatically add settings to a project. */
  def plugins(include: Plugin => Boolean): AddSettings = new Plugins(include)

  /** Includes user settings in the project. */
  val userSettings: AddSettings = User

  /** Includes the settings from all .sbt files in the project's base directory. */
  val defaultSbtFiles: AddSettings = new DefaultSbtFiles(const(true))

  /** Includes the settings from the .sbt files given by `files`. */
  def sbtFiles(files: File*): AddSettings = new SbtFiles(files)

  /** Includes settings automatically*/
  def seq(autos: AddSettings*): AddSettings = new Sequence(autos)

  /** The default inclusion of settings. */
  val allDefaults: AddSettings = seq(autoPlugins, buildScalaFiles, userSettings, nonAutoPlugins, defaultSbtFiles)

  /** Combines two automatic setting configurations. */
  def append(a: AddSettings, b: AddSettings): AddSettings = (a, b) match {
    case (sa: Sequence, sb: Sequence) => seq(sa.sequence ++ sb.sequence: _*)
    case (sa: Sequence, _)            => seq(sa.sequence :+ b: _*)
    case (_, sb: Sequence)            => seq(a +: sb.sequence: _*)
    case _                            => seq(a, b)
  }

  def clearSbtFiles(a: AddSettings): AddSettings = tx(a) {
    case _: DefaultSbtFiles | _: SbtFiles => None
    case x                                => Some(x)
  } getOrElse seq()

  private[sbt] def tx(a: AddSettings)(f: AddSettings => Option[AddSettings]): Option[AddSettings] = a match {
    case s: Sequence =>
      s.sequence.flatMap { b => tx(b)(f) } match {
        case Seq()  => None
        case Seq(x) => Some(x)
        case ss     => Some(new Sequence(ss))
      }
    case x => f(x)
  }
}