import sbt._
import sbt.Keys._

import java.io.File

/** An automatic plugin that handles everything related to JPMS modules. One needs to explicitly
  * enable this plugin in a project with `.enablePlugins(JPMSPlugin)`. The keys and tasks provided by this plugin
  * corresponds to the module-related options of `javac` and `java` commands.
  *
  * This plugin injects all the module-specific options to `javaOptions`, based on
  * the settings of this plugin.
  *
  * If this plugin is enabled, and no settings/tasks from this plugin are used, then the plugin will
  * not inject anything into `javaOptions` or `javacOptions`.
  */
object JPMSPlugin extends AutoPlugin {
  object autoImport {
    val javaModuleName =
      settingKey[String]("The name of the Java (JPMS) module")
    val addModules = settingKey[Seq[String]](
      "Module names that will be added to --add-modules option"
    )
    val modulePath = taskKey[Seq[File]](
      "Directories (Jar archives or expanded Jar archives) that will be put into " +
      "--module-path option"
    )
    val patchModules = taskKey[Map[String, Seq[File]]](
      """
        |A map of module names to directories (Jar archives or expanded Jar archives) that will be
        |put into --patch-module option.
        |""".stripMargin
    )
    val addExports = taskKey[Map[String, Seq[String]]](
      """
        |A map of module names to packages that will be put into --add-exports option.
        |The format of `--add-exports` option is `module/package=target-module(,target-module)*`
        |The key in the map is `module/package` and the value is a sequence of target modules
        |""".stripMargin
    )
    val addReads = taskKey[Map[String, Seq[String]]](
      """
        |A map of module names to modules that will be put into --add-reads option.
        |When a module A reads a module B, it means that it "depends" on it - it has the same
        |effect as if module A would have `requires B` in its module-info.java file.
        |""".stripMargin
    )
    val compileModuleInfo = taskKey[Unit]("Compile module-info.java")
  }

  import autoImport._

  override lazy val projectSettings: Seq[Setting[_]] = Seq(
    addModules := Seq.empty,
    modulePath := Seq.empty,
    patchModules := Map.empty,
    addExports := Map.empty,
    addReads := Map.empty,
    compileModuleInfo := {},
    // javacOptions only inject --module-path and --add-modules, not the rest of the
    // options.
    Compile / javacOptions ++= {
      constructOptions(
        streams.value.log,
        modulePath = (Compile / modulePath).value,
        addModules = (Compile / addModules).value
      )
    },
    Compile / javaOptions ++= {
      constructOptions(
        streams.value.log,
        (Compile / modulePath).value,
        (Compile / addModules).value,
        (Compile / patchModules).value,
        (Compile / addExports).value,
        (Compile / addReads).value
      )
    },
    Test / javacOptions ++= {
      constructOptions(
        streams.value.log,
        modulePath = (Test / modulePath).value,
        addModules = (Test / addModules).value
      )
    },
    Test / javaOptions ++= {
      constructOptions(
        streams.value.log,
        (Test / modulePath).value,
        (Test / addModules).value,
        (Test / patchModules).value,
        (Test / addExports).value,
        (Test / addReads).value
      )
    }
  )

  def constructOptions(
    log: Logger,
    modulePath: Seq[File],
    addModules: Seq[String]              = Seq.empty,
    patchModules: Map[String, Seq[File]] = Map.empty,
    addExports: Map[String, Seq[String]] = Map.empty,
    addReads: Map[String, Seq[String]]   = Map.empty
  ): Seq[String] = {
    val patchOpts: Seq[String] = patchModules.flatMap {
      case (moduleName, dirsToPatch) =>
        val patchStr = dirsToPatch
          .map(_.getAbsolutePath)
          .mkString(File.pathSeparator)
        Seq(
          "--patch-module",
          s"$moduleName=$patchStr"
        )
    }.toSeq

    val addExportsOpts: Seq[String] = addExports.flatMap {
      case (modPkgName, targetModules) =>
        if (!modPkgName.contains("/")) {
          log.error(s"JPMSPlugin: Invalid module/package name: $modPkgName")
        }
        Seq(
          "--add-exports",
          modPkgName + "=" + targetModules.mkString(",")
        )
    }.toSeq

    val modulePathOpts = if (modulePath.isEmpty) {
      Seq.empty
    } else {
      Seq(
        "--module-path",
        modulePath.map(_.getAbsolutePath).mkString(File.pathSeparator)
      )
    }

    val addModsOpts = if (addModules.isEmpty) {
      Seq.empty
    } else {
      Seq(
        "--add-modules",
        addModules.mkString(",")
      )
    }

    val addReadsOpts = addReads.flatMap { case (modName, targetModules) =>
      Seq(
        "--add-reads",
        modName + "=" + targetModules.mkString(",")
      )
    }.toSeq

    modulePathOpts ++ addModsOpts ++ patchOpts ++ addExportsOpts ++ addReadsOpts
  }
}