/* =========================================================================================
 * Copyright © 2013-2017 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.context

import java.io._
import java.nio.ByteBuffer

import kamon.Kamon

class Context private (private[context] val entries: Map[Key[_], Any]) extends scala.Serializable {
  def get[T](key: Key[T]): T =
    entries.getOrElse(key, key.emptyValue).asInstanceOf[T]

  def withKey[T](key: Key[T], value: T): Context =
    new Context(entries.updated(key, value))

  var _deserializedEntries: Map[Key[_], Any] = Map.empty

  @throws[IOException]
  private def writeObject(out: ObjectOutputStream): Unit = out.write(
    Kamon.contextCodec().Binary.encode(this).array()
  )

  @throws[IOException]
  @throws[ClassNotFoundException]
  private def readObject(in: ObjectInputStream): Unit = {
    val buf = new Array[Byte](in.available())
    in.readFully(buf)
    _deserializedEntries = Kamon.contextCodec().Binary.decode(ByteBuffer.wrap(buf)).entries
  }

  def readResolve(): AnyRef = new Context(_deserializedEntries)

  override def equals(obj: scala.Any): Boolean = {
    obj != null &&
    obj.isInstanceOf[Context] &&
    obj.asInstanceOf[Context].entries != null &&
    obj.asInstanceOf[Context].entries == this.entries
  }

  override def hashCode(): Int = entries.hashCode()

}

object Context {

  val Empty = new Context(Map.empty)

  def apply(): Context =
    Empty

  def create(): Context =
    Empty

  def apply[T](key: Key[T], value: T): Context =
    new Context(Map(key -> value))

  def create[T](key: Key[T], value: T): Context =
    apply(key, value)

}


sealed abstract class Key[T] {
  def name: String
  def emptyValue: T
  def broadcast: Boolean
}

object Key {

  def local[T](name: String, emptyValue: T): Key[T] =
    new Default[T](name, emptyValue, false)

  def broadcast[T](name: String, emptyValue: T): Key[T] =
    new Default[T](name, emptyValue, true)

  def broadcastString(name: String): Key[Option[String]] =
    new Default[Option[String]](name, None, true)


  private class Default[T](val name: String, val emptyValue: T, val broadcast: Boolean) extends Key[T] {
    override def hashCode(): Int =
      name.hashCode

    override def equals(that: Any): Boolean =
      that.isInstanceOf[Default[_]] && that.asInstanceOf[Default[_]].name == this.name
  }
}