/*
 * =========================================================================================
 * Copyright © 2013-2014 the kamon project <http://kamon.io/>
 *
 * 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.
 * =========================================================================================
 */

package kamon.play

import akka.actor.{ ExtendedActorSystem, Extension, ExtensionId, ExtensionIdProvider }
import akka.event.Logging
import kamon.Kamon
import kamon.http.HttpServerMetrics
import play.api.libs.ws.WSRequest
import play.api.mvc.RequestHeader

object Play extends ExtensionId[PlayExtension] with ExtensionIdProvider {
  override def lookup(): ExtensionId[_ <: Extension] = Play
  override def createExtension(system: ExtendedActorSystem): PlayExtension = new PlayExtension(system)

  val SegmentLibraryName = "WS-client"
}

class PlayExtension(private val system: ExtendedActorSystem) extends Kamon.Extension {
  val log = Logging(system, classOf[PlayExtension])
  log.info(s"Starting the Kamon(Play) extension")

  private val config = system.settings.config.getConfig("kamon.play")
  val httpServerMetrics = Kamon.metrics.entity(HttpServerMetrics, "play-server")

  val includeTraceToken: Boolean = config.getBoolean("automatic-trace-token-propagation")
  val traceTokenHeaderName: String = config.getString("trace-token-header-name")

  private val nameGeneratorFQN = config.getString("name-generator")
  private val nameGenerator: NameGenerator = system.dynamicAccess.createInstanceFor[NameGenerator](nameGeneratorFQN, Nil).get

  def generateTraceName(requestHeader: RequestHeader): String = nameGenerator.generateTraceName(requestHeader)
  def generateHttpClientSegmentName(request: WSRequest): String = nameGenerator.generateHttpClientSegmentName(request)
}

trait NameGenerator {
  def generateTraceName(requestHeader: RequestHeader): String
  def generateHttpClientSegmentName(request: WSRequest): String
}

class DefaultNameGenerator extends NameGenerator {
  import scala.collection.concurrent.TrieMap
  import play.api.Routes
  import java.util.Locale
  import kamon.util.TriemapAtomicGetOrElseUpdate.Syntax

  private val cache = TrieMap.empty[String, String]
  private val normalizePattern = """\$([^<]+)<[^>]+>""".r

  def generateTraceName(requestHeader: RequestHeader): String = requestHeader.tags.get(Routes.ROUTE_VERB).map { verb ⇒
    val path = requestHeader.tags(Routes.ROUTE_PATTERN)
    cache.atomicGetOrElseUpdate(s"$verb$path", {
      val traceName = {
        // Convert paths of form GET /foo/bar/$paramname<regexp>/blah to foo.bar.paramname.blah.get
        val p = normalizePattern.replaceAllIn(path, "$1").replace('/', '.').dropWhile(_ == '.')
        val normalisedPath = {
          if (p.lastOption.filter(_ != '.').isDefined) s"$p."
          else p
        }
        s"$normalisedPath${verb.toLowerCase(Locale.ENGLISH)}"
      }
      traceName
    })
  } getOrElse s"${requestHeader.method}: ${requestHeader.uri}"

  def generateHttpClientSegmentName(request: WSRequest): String = request.url
}