package dotty.tools
package dotc
package core
package tasty

import collection.mutable
import Names.{Name, chrs, DerivedTermName, SimpleTermName}
import Decorators._, NameOps._
import TastyBuffer._
import scala.io.Codec
import TastyName._
import TastyFormat._

class NameBuffer extends TastyBuffer(10000) {
  import NameBuffer._

  private val nameRefs = new mutable.LinkedHashMap[TastyName, NameRef]

  def nameIndex(name: TastyName): NameRef = nameRefs.get(name) match {
    case Some(ref) =>
      ref
    case None =>
      val ref = NameRef(nameRefs.size)
      nameRefs(name) = ref
      ref
  }

  def nameIndex(name: Name, toTasty: SimpleTermName => TastyName): NameRef = {
    val tname = name.toTermName match {
      case DerivedTermName(name1, NameInfo.ModuleClass) =>
        ModuleClass(nameIndex(name1, toTasty))
      case DerivedTermName(name1, NameInfo.SuperAccessor) =>
        SuperAccessor(nameIndex(name1, toTasty))
      case DerivedTermName(prefix, qual: NameInfo.Qualified) =>
        val tcon: (NameRef, NameRef) => TastyName = qual match {
          case _: NameInfo.Select => Qualified
          case _: NameInfo.Flatten => Flattened
          case _: NameInfo.Expand => Expanded
        }
        tcon(nameIndex(prefix, toTasty), nameIndex(qual.name))
      case DerivedTermName(prefix, NameInfo.DefaultGetter(num)) =>
        DefaultGetter(nameIndex(prefix, toTasty), num)
      case DerivedTermName(prefix, NameInfo.Variant(sign)) =>
        Variant(nameIndex(prefix, toTasty), sign)
      case name1 =>
        if (name1.isShadowedName) Shadowed(nameIndex(name1.revertShadowed, toTasty))
        else toTasty(name1.asSimpleName)
    }
    nameIndex(tname)
  }

  def nameIndex(name: Name): NameRef = nameIndex(name, Simple)

  def nameIndex(str: String): NameRef = nameIndex(str.toTermName)

  def fullNameIndex(name: Name): NameRef = {
    def split(name: SimpleTermName): TastyName = {
      val pos = name.lastIndexOf('.')
      if (pos <= 0) Simple(name)
      else Qualified(fullNameIndex(name.take(pos)), nameIndex(name.drop(pos + 1)))
    }
    nameIndex(name, split)
  }

  private def withLength(op: => Unit, lengthWidth: Int = 1): Unit = {
    val lengthAddr = currentAddr
    for (i <- 0 until lengthWidth) writeByte(0)
    op
    val length = currentAddr.index - lengthAddr.index - 1
    putNat(lengthAddr, length, lengthWidth)
  }

  def writeNameRef(ref: NameRef) = writeNat(ref.index)

  def pickleName(name: TastyName): Unit = name match {
    case Simple(name) =>
      val bytes =
        if (name.length == 0) new Array[Byte](0)
        else Codec.toUTF8(chrs, name.start, name.length)
      writeByte(UTF8)
      writeNat(bytes.length)
      writeBytes(bytes, bytes.length)
    case Qualified(qualified, selector) =>
      writeByte(QUALIFIED)
      withLength { writeNameRef(qualified); writeNameRef(selector) }
    case Flattened(qualified, selector) =>
      writeByte(FLATTENED)
      withLength { writeNameRef(qualified); writeNameRef(selector) }
    case Expanded(prefix, original) =>
      writeByte(EXPANDED)
      withLength { writeNameRef(prefix); writeNameRef(original) }
    case Signed(original, params, result) =>
      writeByte(SIGNED)
      withLength(
          { writeNameRef(original); writeNameRef(result); params.foreach(writeNameRef) },
          if ((params.length + 2) * maxIndexWidth <= maxNumInByte) 1 else 2)
    case ModuleClass(module) =>
      writeByte(OBJECTCLASS)
      withLength { writeNameRef(module) }
    case SuperAccessor(accessed) =>
      writeByte(SUPERACCESSOR)
      withLength { writeNameRef(accessed) }
    case DefaultGetter(method, paramNumber) =>
      writeByte(DEFAULTGETTER)
      withLength { writeNameRef(method); writeNat(paramNumber) }
    case Shadowed(original) =>
      writeByte(SHADOWED)
      withLength { writeNameRef(original) }
    case Variant(original, sign) =>
      writeByte(VARIANT)
      withLength { writeNameRef(original); writeNat(sign + 1) }
  }

  override def assemble(): Unit = {
    var i = 0
    for ((name, ref) <- nameRefs) {
      assert(ref.index == i)
      i += 1
      pickleName(name)
    }
  }
}

object NameBuffer {
  private val maxIndexWidth = 3  // allows name indices up to 2^21.
  private val payloadBitsPerByte = 7 // determined by nat encoding in TastyBuffer
  private val maxNumInByte = (1 << payloadBitsPerByte) - 1
}