/*
 * Copyright 2015 Lightbend Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import com.google.googlejavaformat.java.{Formatter, JavaFormatterOptions}
import sbt.Keys._
import sbt._
import sbt.util.CacheImplicits._
import sbt.util.{CacheStoreFactory, FileInfo, Logger}
import scala.collection.immutable.Seq

/** A local fork of https://github.com/sbt/sbt-java-formatter. The original plugin uses a very outdated version
  * of `google-java-format` dependency which does not support syntax > JDK8. It's unlikely we will see the
  * dependency upgraded any time soon, if ever, hence the almost one-to-one copy of the plugin.
  */
object JavaFormatter {

  def apply(
    sourceDirectories: Seq[File],
    includeFilter: FileFilter,
    excludeFilter: FileFilter,
    streams: TaskStreams,
    cacheStoreFactory: CacheStoreFactory,
    options: JavaFormatterOptions
  ): Unit = {
    val files = sourceDirectories
      .descendantsExcept(includeFilter, excludeFilter)
      .get
      .toList
    cachedFormatSources(cacheStoreFactory, files, streams.log)(
      new Formatter(options)
    )
  }

  def check(
    baseDir: File,
    sourceDirectories: Seq[File],
    includeFilter: FileFilter,
    excludeFilter: FileFilter,
    streams: TaskStreams,
    cacheStoreFactory: CacheStoreFactory,
    options: JavaFormatterOptions
  ): Boolean = {
    val files = sourceDirectories
      .descendantsExcept(includeFilter, excludeFilter)
      .get
      .toList
    val analysis =
      cachedCheckSources(cacheStoreFactory, baseDir, files, streams.log)(
        new Formatter(options)
      )
    trueOrBoom(analysis)
  }

  private def plural(i: Int) = if (i == 1) "" else "s"

  private def trueOrBoom(analysis: Analysis): Boolean = {
    val failureCount = analysis.failedCheck.size
    if (failureCount > 0) {
      throw new MessageOnlyException(
        s"${failureCount} file${plural(failureCount)} must be formatted"
      )
    }
    true
  }

  case class Analysis(failedCheck: Set[File])

  object Analysis {

    import sjsonnew.{:*:, LList, LNil}

    implicit val analysisIso = LList.iso(
      { a: Analysis => ("failedCheck", a.failedCheck) :*: LNil },
      { in: (Set[File] :*: LNil) =>
        Analysis(in.head)
      }
    )
  }

  private def cachedCheckSources(
    cacheStoreFactory: CacheStoreFactory,
    baseDir: File,
    sources: Seq[File],
    log: Logger
  )(implicit formatter: Formatter): Analysis = {
    trackSourcesViaCache(cacheStoreFactory, sources) { (outDiff, prev) =>
      log.debug(outDiff.toString)
      val updatedOrAdded          = outDiff.modified & outDiff.checked
      val filesToCheck: Set[File] = updatedOrAdded
      val prevFailed: Set[File]   = prev.failedCheck & outDiff.unmodified
      prevFailed.foreach { file =>
        warnBadFormat(file.relativeTo(baseDir).getOrElse(file), log)
      }
      val result = checkSources(baseDir, filesToCheck.toList, log)
      prev.copy(failedCheck = result.failedCheck | prevFailed)
    }
  }

  private def warnBadFormat(file: File, log: Logger): Unit = {
    log.warn(s"${file.toString} isn't formatted properly!")
  }

  private def checkSources(baseDir: File, sources: Seq[File], log: Logger)(
    implicit formatter: Formatter
  ): Analysis = {
    if (sources.nonEmpty) {
      log.info(
        s"Checking ${sources.size} Java source${plural(sources.size)}..."
      )
    }
    val unformatted =
      withFormattedSources(sources, log)((file, input, output) => {
        val diff = input != output
        if (diff) {
          warnBadFormat(file.relativeTo(baseDir).getOrElse(file), log)
          Some(file)
        } else None
      }).flatten.flatten.toSet
    Analysis(failedCheck = unformatted)
  }

  private def cachedFormatSources(
    cacheStoreFactory: CacheStoreFactory,
    sources: Seq[File],
    log: Logger
  )(implicit
    formatter: Formatter
  ): Unit = {
    trackSourcesViaCache(cacheStoreFactory, sources) { (outDiff, prev) =>
      log.debug(outDiff.toString)
      val updatedOrAdded           = outDiff.modified & outDiff.checked
      val filesToFormat: Set[File] = updatedOrAdded | prev.failedCheck
      if (filesToFormat.nonEmpty) {
        log.info(
          s"Formatting ${filesToFormat.size} Java source${plural(filesToFormat.size)}..."
        )
        formatSources(filesToFormat, log)
      }
      Analysis(Set.empty)
    }
  }

  private def formatSources(sources: Set[File], log: Logger)(implicit
    formatter: Formatter
  ): Unit = {
    val cnt =
      withFormattedSources(sources.toList, log)((file, input, output) => {
        if (input != output) {
          IO.write(file, output)
          1
        } else {
          0
        }
      }).flatten.sum
    log.info(s"Reformatted $cnt Java source${plural(cnt)}")
  }

  private def trackSourcesViaCache(
    cacheStoreFactory: CacheStoreFactory,
    sources: Seq[File]
  )(f: (ChangeReport[File], Analysis) => Analysis): Analysis = {
    val prevTracker =
      Tracked.lastOutput[Unit, Analysis](cacheStoreFactory.make("last")) {
        (_, prev0) =>
          val prev = prev0.getOrElse(Analysis(Set.empty))
          Tracked.diffOutputs(
            cacheStoreFactory.make("output-diff"),
            FileInfo.lastModified
          )(sources.toSet) { (outDiff: ChangeReport[File]) =>
            f(outDiff, prev)
          }

      }
    prevTracker(())
  }

  private def withFormattedSources[T](sources: Seq[File], log: Logger)(
    onFormat: (File, String, String) => T
  )(implicit formatter: Formatter): Seq[Option[T]] = {
    sources.map { file =>
      val input = IO.read(file)
      try {
        val output = formatter.formatSourceAndFixImports(input)
        Some(onFormat(file, input, output))
      } catch {
        case e: Exception => Some(onFormat(file, input, input))
      }
    }
  }

}