package xyz.driver.core.rest

import java.nio.file.{Files, Path}
import java.security.spec.X509EncodedKeySpec
import java.security.{KeyFactory, PublicKey}

import akka.actor.ActorSystem
import akka.http.scaladsl.Http
import akka.http.scaladsl.marshalling.{ToEntityMarshaller, ToResponseMarshallable}
import akka.http.scaladsl.model._
import akka.http.scaladsl.model.headers.{HttpChallenges, RawHeader, `User-Agent`}
import akka.http.scaladsl.server.AuthenticationFailedRejection.CredentialsRejected
import akka.http.scaladsl.settings.{ClientConnectionSettings, ConnectionPoolSettings}
import akka.http.scaladsl.unmarshalling.{Unmarshal, Unmarshaller}
import akka.stream.scaladsl.Flow
import akka.stream.{ActorMaterializer, Materializer}
import akka.util.ByteString
import com.github.swagger.akka.model._
import com.github.swagger.akka.{HasActorSystem, SwaggerHttpService}
import com.typesafe.config.Config
import com.typesafe.scalalogging.Logger
import io.swagger.models.Scheme
import org.slf4j.MDC
import pdi.jwt.{Jwt, JwtAlgorithm}
import xyz.driver.core.auth._
import xyz.driver.core.{Name, generators}
import xyz.driver.core.time.provider.TimeProvider

import scala.concurrent.{ExecutionContext, Future}
import scala.util.{Failure, Success}
import scalaz.Scalaz.{futureInstance, intInstance, listInstance, mapEqual, mapMonoid, stringInstance}
import scalaz.syntax.equal._
import scalaz.syntax.semigroup._
import scalaz.syntax.std.boolean._
import scalaz.syntax.traverse._
import scalaz.{Functor, ListT, OptionT, Semigroup}

object `package` {
  import akka.http.scaladsl.server._
  import Directives._

  def serviceContext: Directive1[ServiceRequestContext] = extract(ctx => extractServiceContext(ctx.request))

  def extractServiceContext(request: HttpRequest): ServiceRequestContext =
    new ServiceRequestContext(extractTrackingId(request), extractContextHeaders(request))

  def extractTrackingId(request: HttpRequest): String = {
    request.headers
      .find(_.name == ContextHeaders.TrackingIdHeader)
      .fold(java.util.UUID.randomUUID.toString)(_.value())
  }

  def extractStacktrace(request: HttpRequest): Array[String] =
    request.headers.find(_.name == ContextHeaders.StacktraceHeader).fold("")(_.value()).split("->")

  def extractContextHeaders(request: HttpRequest): Map[String, String] = {
    request.headers.filter { h =>
      h.name === ContextHeaders.AuthenticationTokenHeader || h.name === ContextHeaders.TrackingIdHeader ||
      h.name === ContextHeaders.PermissionsTokenHeader || h.name === ContextHeaders.StacktraceHeader
    } map { header =>
      if (header.name === ContextHeaders.AuthenticationTokenHeader) {
        header.name -> header.value.stripPrefix(ContextHeaders.AuthenticationHeaderPrefix).trim
      } else {
        header.name -> header.value
      }
    } toMap
  }

  private[rest] def escapeScriptTags(byteString: ByteString): ByteString = {
    @annotation.tailrec
    def dirtyIndices(from: Int, descIndices: List[Int]): List[Int] = {
      val index = byteString.indexOf('/', from)
      if (index === -1) descIndices.reverse
      else {
        val (init, tail) = byteString.splitAt(index)
        if ((init endsWith "<") && (tail startsWith "/sc")) {
          dirtyIndices(index + 1, index :: descIndices)
        } else {
          dirtyIndices(index + 1, descIndices)
        }
      }
    }

    val indices = dirtyIndices(0, Nil)

    indices.headOption.fold(byteString) { head =>
      val builder = ByteString.newBuilder
      builder ++= byteString.take(head)

      (indices :+ byteString.length).sliding(2).foreach {
        case Seq(start, end) =>
          builder += ' '
          builder ++= byteString.slice(start, end)
        case Seq(_) => // Should not match; sliding on at least 2 elements
          assert(indices.nonEmpty, s"Indices should have been nonEmpty: $indices")
      }
      builder.result
    }
  }

  val sanitizeRequestEntity: Directive0 = {
    mapRequest(request => request.mapEntity(entity => entity.transformDataBytes(Flow.fromFunction(escapeScriptTags))))
  }
}

object Implicits {
  implicit class OptionTRestAdditions[T](optionT: OptionT[Future, T]) {
    def responseOrNotFound(successCode: StatusCodes.Success = StatusCodes.OK)(
            implicit F: Functor[Future],
            em: ToEntityMarshaller[T]): Future[ToResponseMarshallable] = {
      optionT.fold[ToResponseMarshallable](successCode -> _, StatusCodes.NotFound -> None)
    }
  }
}

class ServiceRequestContext(val trackingId: String = generators.nextUuid().toString,
                            val contextHeaders: Map[String, String] = Map.empty[String, String]) {
  def authToken: Option[AuthToken] =
    contextHeaders.get(AuthProvider.AuthenticationTokenHeader).map(AuthToken.apply)

  def permissionsToken: Option[PermissionsToken] =
    contextHeaders.get(AuthProvider.PermissionsTokenHeader).map(PermissionsToken.apply)

  def withAuthToken(authToken: AuthToken): ServiceRequestContext =
    new ServiceRequestContext(
      trackingId,
      contextHeaders.updated(AuthProvider.AuthenticationTokenHeader, authToken.value)
    )

  def withAuthenticatedUser[U <: User](authToken: AuthToken, user: U): AuthorizedServiceRequestContext[U] =
    new AuthorizedServiceRequestContext(
      trackingId,
      contextHeaders.updated(AuthProvider.AuthenticationTokenHeader, authToken.value),
      user
    )

  override def hashCode(): Int =
    Seq[Any](trackingId, contextHeaders).foldLeft(31)((result, obj) => 31 * result + obj.hashCode())

  override def equals(obj: Any): Boolean = obj match {
    case ctx: ServiceRequestContext => trackingId === ctx.trackingId && contextHeaders === ctx.contextHeaders
    case _                          => false
  }

  override def toString: String = s"ServiceRequestContext($trackingId, $contextHeaders)"
}

class AuthorizedServiceRequestContext[U <: User](override val trackingId: String = generators.nextUuid().toString,
                                                 override val contextHeaders: Map[String, String] =
                                                   Map.empty[String, String],
                                                 val authenticatedUser: U)
    extends ServiceRequestContext {

  def withPermissionsToken(permissionsToken: PermissionsToken): AuthorizedServiceRequestContext[U] =
    new AuthorizedServiceRequestContext[U](
      trackingId,
      contextHeaders.updated(AuthProvider.PermissionsTokenHeader, permissionsToken.value),
      authenticatedUser)

  override def hashCode(): Int = 31 * super.hashCode() + authenticatedUser.hashCode()

  override def equals(obj: Any): Boolean = obj match {
    case ctx: AuthorizedServiceRequestContext[U] => super.equals(ctx) && ctx.authenticatedUser == authenticatedUser
    case _                                       => false
  }

  override def toString: String =
    s"AuthorizedServiceRequestContext($trackingId, $contextHeaders, $authenticatedUser)"
}

object ContextHeaders {
  val AuthenticationTokenHeader  = "Authorization"
  val PermissionsTokenHeader     = "Permissions"
  val AuthenticationHeaderPrefix = "Bearer"
  val TrackingIdHeader           = "X-Trace"
  val StacktraceHeader           = "X-Stacktrace"
}

object AuthProvider {
  val AuthenticationTokenHeader    = ContextHeaders.AuthenticationTokenHeader
  val PermissionsTokenHeader       = ContextHeaders.PermissionsTokenHeader
  val SetAuthenticationTokenHeader = "set-authorization"
  val SetPermissionsTokenHeader    = "set-permissions"
}

final case class Pagination(pageSize: Int, pageNumber: Int)

final case class AuthorizationResult(authorized: Map[Permission, Boolean], token: Option[PermissionsToken])
object AuthorizationResult {
  val unauthorized: AuthorizationResult = AuthorizationResult(authorized = Map.empty, None)

  implicit val authorizationSemigroup: Semigroup[AuthorizationResult] = new Semigroup[AuthorizationResult] {
    private implicit val authorizedBooleanSemigroup = Semigroup.instance[Boolean](_ || _)
    private implicit val permissionsTokenSemigroup =
      Semigroup.instance[Option[PermissionsToken]]((a, b) => b.orElse(a))

    override def append(a: AuthorizationResult, b: => AuthorizationResult): AuthorizationResult = {
      AuthorizationResult(a.authorized |+| b.authorized, a.token |+| b.token)
    }
  }
}

trait Authorization[U <: User] {
  def userHasPermissions(user: U, permissions: Seq[Permission])(
          implicit ctx: ServiceRequestContext): Future[AuthorizationResult]
}

class AlwaysAllowAuthorization[U <: User] extends Authorization[U] {
  override def userHasPermissions(user: U, permissions: Seq[Permission])(
          implicit ctx: ServiceRequestContext): Future[AuthorizationResult] = {
    val permissionsMap = permissions.map(_ -> true).toMap
    Future.successful(AuthorizationResult(authorized = permissionsMap, ctx.permissionsToken))
  }
}

class CachedTokenAuthorization[U <: User](publicKey: => PublicKey, issuer: String) extends Authorization[U] {
  override def userHasPermissions(user: U, permissions: Seq[Permission])(
          implicit ctx: ServiceRequestContext): Future[AuthorizationResult] = {
    import spray.json._

    def extractPermissionsFromTokenJSON(tokenObject: JsObject): Option[Map[String, Boolean]] =
      tokenObject.fields.get("permissions").collect {
        case JsObject(fields) =>
          fields.collect {
            case (key, JsBoolean(value)) => key -> value
          }
      }

    val result = for {
      token <- ctx.permissionsToken
      jwt   <- Jwt.decode(token.value, publicKey, Seq(JwtAlgorithm.RS256)).toOption
      jwtJson = jwt.parseJson.asJsObject

      // Ensure jwt is for the currently authenticated user and the correct issuer, otherwise return None
      _ <- jwtJson.fields.get("sub").contains(JsString(user.id.value)).option(())
      _ <- jwtJson.fields.get("iss").contains(JsString(issuer)).option(())

      permissionsMap <- extractPermissionsFromTokenJSON(jwtJson)

      authorized = permissions.map(p => p -> permissionsMap.getOrElse(p.toString, false)).toMap
    } yield AuthorizationResult(authorized, Some(token))

    Future.successful(result.getOrElse(AuthorizationResult.unauthorized))
  }
}

object CachedTokenAuthorization {
  def apply[U <: User](publicKeyFile: Path, issuer: String): CachedTokenAuthorization[U] = {
    lazy val publicKey: PublicKey = {
      val publicKeyBase64Encoded = new String(Files.readAllBytes(publicKeyFile)).trim
      val publicKeyBase64Decoded = java.util.Base64.getDecoder.decode(publicKeyBase64Encoded)
      val spec                   = new X509EncodedKeySpec(publicKeyBase64Decoded)
      KeyFactory.getInstance("RSA").generatePublic(spec)
    }
    new CachedTokenAuthorization[U](publicKey, issuer)
  }
}

class ChainedAuthorization[U <: User](authorizations: Authorization[U]*)(implicit execution: ExecutionContext)
    extends Authorization[U] {

  override def userHasPermissions(user: U, permissions: Seq[Permission])(
          implicit ctx: ServiceRequestContext): Future[AuthorizationResult] = {
    def allAuthorized(permissionsMap: Map[Permission, Boolean]): Boolean =
      permissions.forall(permissionsMap.getOrElse(_, false))

    authorizations.toList.foldLeftM[Future, AuthorizationResult](AuthorizationResult.unauthorized) {
      (authResult, authorization) =>
        if (allAuthorized(authResult.authorized)) Future.successful(authResult)
        else {
          authorization.userHasPermissions(user, permissions).map(authResult |+| _)
        }
    }
  }
}

abstract class AuthProvider[U <: User](val authorization: Authorization[U], log: Logger)(
        implicit execution: ExecutionContext) {

  import akka.http.scaladsl.server._
  import Directives._

  /**
    * Specific implementation on how to extract user from request context,
    * can either need to do a network call to auth server or extract everything from self-contained token
    *
    * @param ctx set of request values which can be relevant to authenticate user
    * @return authenticated user
    */
  def authenticatedUser(implicit ctx: ServiceRequestContext): OptionT[Future, U]

  /**
    * Verifies if request is authenticated and authorized to have `permissions`
    */
  def authorize(permissions: Permission*): Directive1[AuthorizedServiceRequestContext[U]] = {
    serviceContext flatMap { ctx =>
      onComplete {
        (for {
          authToken <- OptionT.optionT(Future.successful(ctx.authToken))
          user      <- authenticatedUser(ctx)
          authCtx = ctx.withAuthenticatedUser(authToken, user)
          authorizationResult <- authorization.userHasPermissions(user, permissions)(authCtx).toOptionT

          cachedPermissionsAuthCtx = authorizationResult.token.fold(authCtx)(authCtx.withPermissionsToken)
          allAuthorized            = permissions.forall(authorizationResult.authorized.getOrElse(_, false))
        } yield (cachedPermissionsAuthCtx, allAuthorized)).run
      } flatMap {
        case Success(Some((authCtx, true))) => provide(authCtx)
        case Success(Some((authCtx, false))) =>
          val challenge =
            HttpChallenges.basic(s"User does not have the required permissions: ${permissions.mkString(", ")}")
          log.warn(
            s"User ${authCtx.authenticatedUser} does not have the required permissions: ${permissions.mkString(", ")}")
          reject(AuthenticationFailedRejection(CredentialsRejected, challenge))
        case Success(None) =>
          log.warn(
            s"Wasn't able to find authenticated user for the token provided to verify ${permissions.mkString(", ")}")
          reject(ValidationRejection(s"Wasn't able to find authenticated user for the token provided"))
        case Failure(t) =>
          log.warn(s"Wasn't able to verify token for authenticated user to verify ${permissions.mkString(", ")}", t)
          reject(ValidationRejection(s"Wasn't able to verify token for authenticated user", Some(t)))
      }
    }
  }
}

trait Service

trait RestService extends Service {

  import akka.http.scaladsl.marshallers.sprayjson.SprayJsonSupport._
  import spray.json._

  protected implicit val exec: ExecutionContext
  protected implicit val materializer: Materializer

  implicit class ResponseEntityFoldable(entity: Unmarshal[ResponseEntity]) {
    def fold[T](default: => T)(implicit um: Unmarshaller[ResponseEntity, T]): Future[T] =
      if (entity.value.isKnownEmpty()) Future.successful[T](default) else entity.to[T]
  }

  protected def unitResponse(request: Future[Unmarshal[ResponseEntity]]): OptionT[Future, Unit] =
    OptionT[Future, Unit](request.flatMap(_.to[String]).map(_ => Option(())))

  protected def optionalResponse[T](request: Future[Unmarshal[ResponseEntity]])(
          implicit um: Unmarshaller[ResponseEntity, Option[T]]): OptionT[Future, T] =
    OptionT[Future, T](request.flatMap(_.fold(Option.empty[T])))

  protected def listResponse[T](request: Future[Unmarshal[ResponseEntity]])(
          implicit um: Unmarshaller[ResponseEntity, List[T]]): ListT[Future, T] =
    ListT[Future, T](request.flatMap(_.fold(List.empty[T])))

  protected def jsonEntity(json: JsValue): RequestEntity =
    HttpEntity(ContentTypes.`application/json`, json.compactPrint)

  protected def get(baseUri: Uri, path: String, query: Seq[(String, String)] = Seq.empty) =
    HttpRequest(HttpMethods.GET, endpointUri(baseUri, path, query))

  protected def post(baseUri: Uri, path: String, httpEntity: RequestEntity) =
    HttpRequest(HttpMethods.POST, endpointUri(baseUri, path), entity = httpEntity)

  protected def postJson(baseUri: Uri, path: String, json: JsValue) =
    HttpRequest(HttpMethods.POST, endpointUri(baseUri, path), entity = jsonEntity(json))

  protected def delete(baseUri: Uri, path: String) =
    HttpRequest(HttpMethods.DELETE, endpointUri(baseUri, path))

  protected def endpointUri(baseUri: Uri, path: String) =
    baseUri.withPath(Uri.Path(path))

  protected def endpointUri(baseUri: Uri, path: String, query: Seq[(String, String)]) =
    baseUri.withPath(Uri.Path(path)).withQuery(Uri.Query(query: _*))
}

trait ServiceTransport {

  def sendRequestGetResponse(context: ServiceRequestContext)(requestStub: HttpRequest): Future[HttpResponse]

  def sendRequest(context: ServiceRequestContext)(requestStub: HttpRequest): Future[Unmarshal[ResponseEntity]]
}

trait ServiceDiscovery {

  def discover[T <: Service](serviceName: Name[Service]): T
}

class NoServiceDiscovery extends ServiceDiscovery with SavingUsedServiceDiscovery {

  def discover[T <: Service](serviceName: Name[Service]): T =
    throw new IllegalArgumentException(s"Service with name $serviceName is unknown")
}

trait SavingUsedServiceDiscovery {

  private val usedServices = new scala.collection.mutable.HashSet[String]()

  def saveServiceUsage(serviceName: Name[Service]): Unit = usedServices.synchronized {
    usedServices += serviceName.value
  }

  def getUsedServices: Set[String] = usedServices.synchronized { usedServices.toSet }
}

class HttpRestServiceTransport(applicationName: Name[App],
                               applicationVersion: String,
                               actorSystem: ActorSystem,
                               executionContext: ExecutionContext,
                               log: Logger,
                               time: TimeProvider)
    extends ServiceTransport {

  protected implicit val materializer = ActorMaterializer()(actorSystem)
  protected implicit val execution    = executionContext

  private val client = Http()(actorSystem)

  private val clientConnectionSettings: ClientConnectionSettings =
    ClientConnectionSettings(actorSystem).withUserAgentHeader(
      Option(`User-Agent`(applicationName.value + "/" + applicationVersion)))

  private val connectionPoolSettings: ConnectionPoolSettings = ConnectionPoolSettings(actorSystem)
    .withConnectionSettings(clientConnectionSettings)

  def sendRequestGetResponse(context: ServiceRequestContext)(requestStub: HttpRequest): Future[HttpResponse] = {

    val requestTime = time.currentTime()

    val request = requestStub
      .withHeaders(context.contextHeaders.toSeq.map {
        case (ContextHeaders.TrackingIdHeader, _) =>
          RawHeader(ContextHeaders.TrackingIdHeader, context.trackingId)
        case (ContextHeaders.StacktraceHeader, _) =>
          RawHeader(ContextHeaders.StacktraceHeader,
                    Option(MDC.get("stack"))
                      .orElse(context.contextHeaders.get(ContextHeaders.StacktraceHeader))
                      .getOrElse(""))
        case (header, headerValue) => RawHeader(header, headerValue)
      }: _*)

    log.info(s"Sending request to ${request.method} ${request.uri}")

    val response = client.singleRequest(request, settings = connectionPoolSettings)(materializer)

    response.onComplete {
      case Success(r) =>
        val responseLatency = requestTime.durationTo(time.currentTime())
        log.info(s"Response from ${request.uri} to request $requestStub is successful in $responseLatency ms: $r")

      case Failure(t: Throwable) =>
        val responseLatency = requestTime.durationTo(time.currentTime())
        log.info(s"Failed to receive response from ${request.method} ${request.uri} in $responseLatency ms", t)
        log.warn(s"Failed to receive response from ${request.method} ${request.uri} in $responseLatency ms", t)
    }(executionContext)

    response
  }

  def sendRequest(context: ServiceRequestContext)(requestStub: HttpRequest): Future[Unmarshal[ResponseEntity]] = {

    sendRequestGetResponse(context)(requestStub) map { response =>
      if (response.status == StatusCodes.NotFound) {
        Unmarshal(HttpEntity.Empty: ResponseEntity)
      } else if (response.status.isFailure()) {
        throw new Exception(s"Http status is failure ${response.status} for ${requestStub.method} ${requestStub.uri}")
      } else {
        Unmarshal(response.entity)
      }
    }
  }
}

import scala.reflect.runtime.universe._

class Swagger(override val host: String,
              override val scheme: Scheme,
              version: String,
              override val actorSystem: ActorSystem,
              override val apiTypes: Seq[Type],
              val config: Config)
    extends SwaggerHttpService with HasActorSystem {

  val materializer = ActorMaterializer()(actorSystem)

  override val basePath    = config.getString("swagger.basePath")
  override val apiDocsPath = config.getString("swagger.docsPath")

  override val info = Info(
    config.getString("swagger.apiInfo.description"),
    version,
    config.getString("swagger.apiInfo.title"),
    config.getString("swagger.apiInfo.termsOfServiceUrl"),
    contact = Some(
      Contact(
        config.getString("swagger.apiInfo.contact.name"),
        config.getString("swagger.apiInfo.contact.url"),
        config.getString("swagger.apiInfo.contact.email")
      )),
    license = Some(
      License(
        config.getString("swagger.apiInfo.license"),
        config.getString("swagger.apiInfo.licenseUrl")
      )),
    vendorExtensions = Map.empty[String, AnyRef]
  )

  def swaggerUI = get {
    pathPrefix("") {
      pathEndOrSingleSlash {
        getFromResource("swagger-ui/index.html")
      }
    } ~ getFromResourceDirectory("swagger-ui")
  }
}