// See LICENSE for license details.

/** Enum generators, allowing circuit constants to have more meaningful names.
  */

package chisel3.util

import chisel3._

trait Enum {
  /** Returns a sequence of Bits subtypes with values from 0 until n. Helper method. */
  protected def createValues(n: Int): Seq[UInt] =
    (0 until n).map(_.U(log2Up(n).W))

  /** Returns n unique UInt values, use with unpacking to specify an enumeration.
    *
    * @example {{{
    * val state_on :: state_off :: Nil = Enum(2)
    * val current_state = UInt()
    * switch (current_state) {
    *   is (state_on) {
    *      ...
    *   }
    *   if (state_off) {
    *      ...
    *   }
    * }
    * }}}
    */
  def apply(n: Int): List[UInt] = createValues(n).toList
}

object Enum extends Enum {
  @deprecated("use Enum(n)", "chisel3, will be removed soon")
  def apply[T <: Bits](nodeType: T, n: Int): List[T] = {
    require(nodeType.isInstanceOf[UInt], "Only UInt supported for enums")
    require(!nodeType.widthKnown, "Bit width may no longer be specified for enums")
    apply(n).asInstanceOf[List[T]]
  }
}