/*
 * =========================================================================================
 * Copyright © 2013-2015 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.statsd

import java.lang.management.ManagementFactory

import com.typesafe.config.Config
import kamon.metric.{ SingleInstrumentEntityRecorder, MetricKey, Entity }

trait MetricKeyGenerator {
  def generateKey(entity: Entity, metricKey: MetricKey): String
}

class SimpleMetricKeyGenerator(config: Config) extends MetricKeyGenerator {
  type Normalizer = String ⇒ String

  val configSettings = config.getConfig("kamon.statsd.simple-metric-key-generator")
  val application = configSettings.getString("application")
  val includeHostname = configSettings.getBoolean("include-hostname")
  val hostnameOverride = configSettings.getString("hostname-override")
  val normalizer = createNormalizer(configSettings.getString("metric-name-normalization-strategy"))

  val normalizedHostname =
    if (hostnameOverride.equals("none")) normalizer(hostName)
    else normalizer(hostnameOverride)

  val baseName: String =
    if (includeHostname) s"$application.$normalizedHostname"
    else application

  def generateKey(entity: Entity, metricKey: MetricKey): String = entity.category match {
    case "trace-segment" ⇒
      s"${baseName}.trace.${normalizer(entity.tags("trace"))}.segments.${normalizer(entity.name)}.${metricKey.name}"

    case _ if SingleInstrumentEntityRecorder.AllCategories.contains(entity.category) ⇒
      s"${baseName}.${entity.category}.${normalizer(entity.name)}"

    case _ ⇒
      s"${baseName}.${entity.category}.${normalizer(entity.name)}.${metricKey.name}"

  }

  def hostName: String = ManagementFactory.getRuntimeMXBean.getName.split('@')(1)

  def createNormalizer(strategy: String): Normalizer = strategy match {
    case "percent-encode" ⇒ PercentEncoder.encode
    case "normalize"      ⇒ (s: String) ⇒ s.replace(": ", "-").replace(" ", "_").replace("/", "_").replace(".", "_")
  }
}

object PercentEncoder {

  def encode(originalString: String): String = {
    val encodedString = new StringBuilder()

    for (character ← originalString) {
      if (shouldEncode(character)) {
        encodedString.append('%')
        val charHexValue = Integer.toHexString(character).toUpperCase
        if (charHexValue.length < 2)
          encodedString.append('0')

        encodedString.append(charHexValue)

      } else {
        encodedString.append(character)
      }
    }
    encodedString.toString()
  }

  def shouldEncode(ch: Char): Boolean = {
    if (ch > 128 || ch < 0) true
    else " %$&+,./:;=?@<>#%".indexOf(ch) >= 0;
  }
}