/* =========================================================================================
 * 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.instrumentation

import kamon.Kamon
import kamon.play.{ Play, PlayExtension }
import kamon.trace.{ TraceContextAware, TraceRecorder }
import org.aspectj.lang.ProceedingJoinPoint
import org.aspectj.lang.annotation._
import play.api.Routes
import play.api.mvc.Results._
import play.api.mvc._
import play.libs.Akka

@Aspect
class RequestInstrumentation {

  import kamon.play.instrumentation.RequestInstrumentation._

  @DeclareMixin("play.api.mvc.RequestHeader+")
  def mixinContextAwareNewRequest: TraceContextAware = TraceContextAware.default

  @After("execution(* play.api.GlobalSettings+.onStart(*)) && args(application)")
  def afterApplicationStart(application: play.api.Application): Unit = {
    Kamon(Play)(Akka.system())
  }

  @Before("call(* play.api.GlobalSettings+.onRouteRequest(..)) && args(requestHeader)")
  def beforeRouteRequest(requestHeader: RequestHeader): Unit = {
    val system = Akka.system()
    val playExtension = Kamon(Play)(system)
    val defaultTraceName: String = s"${requestHeader.method}: ${requestHeader.uri}"

    val token = if (playExtension.includeTraceToken) {
      requestHeader.headers.toSimpleMap.find(_._1 == playExtension.traceTokenHeaderName).map(_._2)
    } else None

    TraceRecorder.start(defaultTraceName, token)(system)
  }

  @Around("execution(* play.api.GlobalSettings+.doFilter(*)) && args(next)")
  def aroundDoFilter(pjp: ProceedingJoinPoint, next: EssentialAction): Any = {
    val essentialAction = (requestHeader: RequestHeader) ⇒ {
      val executor = Kamon(Play)(Akka.system()).defaultDispatcher

      def onResult(result: Result): Result = {
        TraceRecorder.finish()
        TraceRecorder.currentContext.map { ctx ⇒
          val playExtension = Kamon(Play)(ctx.system)
          recordHttpServerMetrics(result.header, ctx.name, playExtension)
          if (playExtension.includeTraceToken) result.withHeaders(playExtension.traceTokenHeaderName -> ctx.token)
          else result
        }.getOrElse(result)
      }

      //override the current trace name
      normaliseTraceName(requestHeader).map(TraceRecorder.rename(_))

      // Invoke the action
      next(requestHeader).map(onResult)(executor)
    }
    pjp.proceed(Array(EssentialAction(essentialAction)))
  }

  @Before("execution(* play.api.GlobalSettings+.onError(..)) && args(request, ex)")
  def beforeOnError(request: TraceContextAware, ex: Throwable): Unit = request.traceContext.map {
    ctx ⇒ recordHttpServerMetrics(InternalServerError.header, ctx.name, Kamon(Play)(ctx.system))
  }

  private def recordHttpServerMetrics(header: ResponseHeader, traceName: String, playExtension: PlayExtension): Unit =
    playExtension.httpServerMetrics.recordResponse(traceName, header.status.toString)
}

object RequestInstrumentation {

  import java.util.Locale
  import scala.collection.concurrent.TrieMap

  private val cache = TrieMap.empty[String, String]

  def normaliseTraceName(requestHeader: RequestHeader): Option[String] = requestHeader.tags.get(Routes.ROUTE_VERB).map({ verb ⇒
    val path = requestHeader.tags(Routes.ROUTE_PATTERN)
    cache.getOrElseUpdate(s"$verb$path", {
      val traceName = {
        // Convert paths of form GET /foo/bar/$paramname<regexp>/blah to foo.bar.paramname.blah.get
        val p = path.replaceAll("""\$([^<]+)<[^>]+>""", "$1").replace('/', '.').dropWhile(_ == '.')
        val normalisedPath = {
          if (p.lastOption.filter(_ != '.').isDefined) s"$p."
          else p
        }
        s"$normalisedPath${verb.toLowerCase(Locale.ENGLISH)}"
      }
      traceName
    })
  })
}