package s3.website.model

import java.io.File.createTempFile
import java.io._
import java.util.zip.{GZIPInputStream, GZIPOutputStream}

import com.amazonaws.services.s3.model.S3ObjectSummary
import org.apache.commons.codec.digest.DigestUtils
import org.apache.commons.io.IOUtils
import org.apache.tika.Tika
import s3.website._
import s3.website.model.Encoding.{Gzip, Zopfli}
import s3.website.model.Upload.{amountOfMagicGzipBytes, tika}

import scala.concurrent.{ExecutionContextExecutor, Future}
import scala.util.Try

object Encoding {

  val defaultGzipExtensions = ".html" :: ".css" :: ".js" :: ".txt" :: ".ico" :: Nil

  case class Gzip()
  case class Zopfli()
}

sealed trait UploadType {
  val pushAction: PushAction
}

case object NewFile extends UploadType {
  val pushAction = Created
}
case object FileUpdate extends UploadType {
  val pushAction = Updated
}

case object RedirectFile extends UploadType {
  val pushAction = Redirected
}

case class Upload(originalFile: File, uploadType: UploadType)(implicit site: Site, logger: Logger) {
  lazy val s3Key = site.resolveS3Key(originalFile)

  lazy val encodingOnS3: Option[Either[Gzip, Zopfli]] =
    site.config.gzip.flatMap { (gzipSetting: Either[Boolean, Seq[String]]) =>
      val shouldZipThisFile = gzipSetting.fold(
        shouldGzip => Encoding.defaultGzipExtensions exists s3Key.key.endsWith,
        fileExtensions => fileExtensions exists s3Key.key.endsWith
      )
      if (shouldZipThisFile && site.config.gzip_zopfli.isDefined)
        Some(Right(Zopfli()))
      else if (shouldZipThisFile)
        Some(Left(Gzip()))
      else
        None
    }

  lazy val gzipEnabledByConfig: Boolean = encodingOnS3.fold(false)((algorithm: Either[Gzip, Zopfli]) => true)

  lazy val contentType: Try[String] = tika map { tika =>
    val file = // This file contains the data that the user should see after decoding the the transport protocol (HTTP) encoding (practically: after ungzipping)
      if (fileIsGzippedByExternalBuildTool) {
        val unzippedFile = createTempFile("unzipped", originalFile.getName)
        unzippedFile.deleteOnExit()
        using(new GZIPInputStream(fis(originalFile))) { stream =>
          IOUtils.copy(stream, new FileOutputStream(unzippedFile))
        }
        unzippedFile
      } else {
        originalFile
      }
    val mimeType =
      site.config.content_type
        .flatMap { _.globMatch(s3Key) }
        .getOrElse { tika.detect(file) }
    if (mimeType.startsWith("text/") || mimeType == "application/json")
      mimeType + "; charset=utf-8"
    else
      mimeType
  }

  lazy val maxAge: Option[Int] =
    site.config.max_age.flatMap(
      _ fold(
        (maxAge: Int) => Some(maxAge),
        (globs: S3KeyGlob[Int]) => globs.globMatch(s3Key)
      )
    )

  lazy val cacheControl: Option[String] =
    site.config.cache_control.flatMap(
      _ fold(
        (cacheCtrl: String) => Some(cacheCtrl),
        (globs: S3KeyGlob[String]) => globs.globMatch(s3Key)
      )
    )

  /**
   * May throw an exception, so remember to call this in a Try or Future monad
   */
  lazy val md5 = uploadFile map { file =>
    using(fis { file }) { DigestUtils.md5Hex }
  }

  // This is the file we should try to upload
  lazy val uploadFile: Try[File] =
    if (gzipEnabledByConfig)
      Try {
        if (fileIsGzippedByExternalBuildTool) {
          logger.debug(s"File ${originalFile.getAbsolutePath} is already gzipped. Skipping gzip.")
          originalFile
        } else {
          logger.debug(s"Gzipping file ${originalFile.getName}")
          val tempFile = createTempFile(originalFile.getName, "gzip")
          tempFile.deleteOnExit()
          using(new GZIPOutputStream(new FileOutputStream(tempFile))) { stream =>
            IOUtils.copy(fis(originalFile), stream)
          }
          tempFile
        }
      }
    else
      Try(originalFile)

  private lazy val fileIsGzippedByExternalBuildTool = gzipEnabledByConfig && originalFileIsGzipped

  private lazy val originalFileIsGzipped =
    if (originalFile.length() < amountOfMagicGzipBytes) {
      false
    } else {
      val fis = new FileInputStream(originalFile)
      val firstTwoBytes = Array.fill[Byte](amountOfMagicGzipBytes)(0)
      fis.read(firstTwoBytes, 0, amountOfMagicGzipBytes)
      val head = firstTwoBytes(0) & 0xff | (firstTwoBytes(1) << 8) & 0xff00
      head == GZIPInputStream.GZIP_MAGIC
    }

  private[this] def fis(file: File): InputStream = new FileInputStream(file)
  private[this] def using[T <: Closeable, R](cl: T)(f: (T) => R): R = try f(cl) finally cl.close()
}

object Upload {
  lazy val tika = Try(new Tika())
  private val amountOfMagicGzipBytes = 2
}

object Files {
  def recursiveListFiles(f: File): Seq[File] = {
    val these = f.listFiles
    if (these != null)
      these ++ these.filter(_.isDirectory).flatMap(recursiveListFiles)
    else
      Nil
  }

  def listSiteFiles(implicit site: Site, logger: Logger) = {
    def excludeFromUpload(s3Key: S3Key) = {
      val excludeByConfig = site.config.exclude_from_upload exists {
        _.s3KeyRegexes.exists(_ matches s3Key)
      }
      val neverUpload = "s3_website.yml" :: ".env" :: Nil map (k => S3Key.build(k, site.config.s3_key_prefix))
      val doNotUpload = excludeByConfig || (neverUpload contains s3Key)
      if (doNotUpload) logger.debug(s"Excluded $s3Key from upload")
      doNotUpload
    }
    recursiveListFiles(site.rootDirectory)
      .filterNot(_.isDirectory)
      .filterNot(f => excludeFromUpload(site.resolveS3Key(f)))
  }
}

case class Redirect(s3Key: S3Key, redirectTarget: String, needsUpload: Boolean) {
  def uploadType = RedirectFile
}

private case class RedirectSetting(source: S3Key, target: String)

object Redirect {
  type Redirects = Future[Either[ErrorReport, Seq[Redirect]]]

  def resolveRedirects(s3FileFutures: Future[Either[ErrorReport, Seq[S3File]]])
                      (implicit config: Config, executor: ExecutionContextExecutor, pushOptions: PushOptions): Redirects = {
    val redirectSettings = config.redirects.fold(Nil: Seq[RedirectSetting]) { sourcesToTargets =>
      sourcesToTargets.foldLeft(Seq(): Seq[RedirectSetting]) {
        (redirects, sourceToTarget) =>
          redirects :+ RedirectSetting(sourceToTarget._1, applyRedirectRules(sourceToTarget._2))
      }
    }
    def redirectsWithExistsOnS3Info =
      s3FileFutures.map(_.right.map { s3Files =>
        val existingRedirectKeys = s3Files.filter(_.size == 0).map(_.s3Key).toSet
        redirectSettings.map(redirectSetting => 
          Redirect(redirectSetting, needsUpload = !existingRedirectKeys.contains(redirectSetting.source))
        )
      })
    val uploadOnlyMissingRedirects =
      config.treat_zero_length_objects_as_redirects.contains(true) && !pushOptions.force
    val allConfiguredRedirects = Future(Right(redirectSettings.map(redirectSetting =>
      Redirect(redirectSetting, needsUpload = true)
    )))
    if (uploadOnlyMissingRedirects) 
      redirectsWithExistsOnS3Info 
    else 
      allConfiguredRedirects
  }

  private def applyRedirectRules(redirectTarget: String)(implicit config: Config) = {
    val isExternalRedirect = redirectTarget.matches("https?:\\/\\/.*")
    val isInSiteRedirect = redirectTarget.startsWith("/")
    if (isInSiteRedirect || isExternalRedirect)
      redirectTarget
    else
      s"${config.s3_key_prefix.map(prefix => s"/$prefix").getOrElse("")}/$redirectTarget"
  }

  def apply(redirectSetting: RedirectSetting, needsUpload: Boolean): Redirect =
      Redirect(redirectSetting.source, redirectSetting.target, needsUpload)
}

case class S3File(s3Key: S3Key, md5: MD5, size: Long)

object S3File {
  def apply(summary: S3ObjectSummary)(implicit site: Site): S3File =
    S3File(S3Key.build(summary.getKey, None), summary.getETag, summary.getSize)
}