// SPDX-License-Identifier: Apache-2.0

package chisel3

import firrtl.annotations.{IsModule, ModuleTarget}
import chisel3.experimental.{BaseModule, UnlocatableSourceInfo}
import chisel3.internal.firrtl.{Component, DefModule}
import chisel3.internal.Builder.Prefix

import scala.util.Try
import scala.annotation.{implicitNotFound, nowarn}

package object internal {

  @deprecated("This function has moved to chisel3.experimental", "Chisel 3.6")
  val prefix = chisel3.experimental.prefix
  @deprecated("This function has moved to chisel3.experimental", "Chisel 3.6")
  val noPrefix = chisel3.experimental.noPrefix

  @deprecated("This type has moved to chisel3", "Chisel 3.6")
  type ChiselException = chisel3.ChiselException

  @deprecated("This type has moved to chisel3", "Chisel 3.6")
  type InstanceId = chisel3.InstanceId

  @implicitNotFound("You are trying to access a macro-only API. Please use the @public annotation instead.")
  trait MacroGenerated

  /** Marker trait for modules that are not true modules */
  private[chisel3] trait PseudoModule extends BaseModule

  /* Check if a String name is a temporary name */
  def isTemp(name: String): Boolean = name.nonEmpty && name.head == '_'

  /** Creates a name String from a prefix and a seed
    * @param prefix The prefix associated with the seed (must be in correct order, *not* reversed)
    * @param seed The seed for computing the name (if available)
    */
  def buildName(seed: String, prefix: Prefix): String = {
    // Don't bother copying the String if there's no prefix
    if (prefix.isEmpty) {
      seed
    } else {
      // Using Java's String builder to micro-optimize appending a String excluding 1st character
      // for temporaries
      val builder = new java.lang.StringBuilder()
      // Starting with _ is the indicator of a temporary
      val temp = isTemp(seed)
      // Make sure the final result is also a temporary if this is a temporary
      if (temp) {
        builder.append('_')
      }
      prefix.foreach { p =>
        builder.append(p)
        builder.append('_')
      }
      if (temp) {
        // We've moved the leading _ to the front, drop it here
        builder.append(seed, 1, seed.length)
      } else {
        builder.append(seed)
      }
      builder.toString
    }
  }

  // Sanitizes a name, e.g. from a `HasId`, by stripping all non ANSI-C characters
  private[chisel3] def sanitize(s: String, leadingDigitOk: Boolean = false): String = {
    // TODO what character set does FIRRTL truly support? using ANSI C for now
    def legalStart(c: Char) = (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || c == '_'
    def legal(c:      Char) = legalStart(c) || (c >= '0' && c <= '9')
    val res = if (s.forall(legal)) s else s.filter(legal)
    val headOk = (!res.isEmpty) && (leadingDigitOk || legalStart(res.head))
    if (headOk) res else s"_$res"
  }

  /** Internal API for [[ViewParent]] */
  sealed private[chisel3] class ViewParentAPI extends RawModule() with PseudoModule {
    // We must provide `absoluteTarget` but not `toTarget` because otherwise they would be exactly
    // the same and we'd have no way to distinguish the kind of target when renaming view targets in
    // the Converter
    // Note that this is not overriding .toAbsoluteTarget, that is a final def in BaseModule that delegates
    // to this method
    private[chisel3] val absoluteTarget: IsModule = ModuleTarget(this.circuitName, "_$$AbsoluteView$$_")

    // This module is not instantiable
    override private[chisel3] def generateComponent():  Option[Component] = None
    override private[chisel3] def initializeInParent(): Unit = ()
    // This module is not really part of the circuit
    _parent = None

    // Sigil to mark views, starts with '_' to make it a legal FIRRTL target
    override def desiredName = "_$$View$$_"

    private[chisel3] val fakeComponent: Component = DefModule(this, desiredName, Nil, Nil)
  }

  /** Special internal object representing the parent of all views
    *
    * @note this is a val instead of an object because of the need to wrap in Module(...)
    */
  private[chisel3] val ViewParent =
    Module.do_apply(new ViewParentAPI)(UnlocatableSourceInfo)
}
