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package firrtl.passes

import firrtl._
import firrtl.ir._
import firrtl.Utils._
import firrtl.Mappers._

import annotation.tailrec

/** Reports errors for any references that are not fully initialized
  *
  * @note This pass looks for [[firrtl.WVoid]]s left behind by [[ExpandWhens]]
  * @note Assumes single connection (ie. no last connect semantics)
  */
object CheckInitialization extends Pass {
  def name = "Check Initialization"

  private case class VoidExpr(stmt: Statement, voidDeps: Seq[Expression])

  class RefNotInitializedException(info: Info, mname: String, name: String, trace: Seq[Statement]) extends PassException(
      s"$info : [module $mname]  Reference $name is not fully initialized.\n" + 
      trace.map(s => s"  ${get_info(s)} : ${s.serialize}").mkString("\n")
    )

  private def getTrace(expr: WrappedExpression, voidExprs: Map[WrappedExpression, VoidExpr]): Seq[Statement] = {
    @tailrec
    def rec(e: WrappedExpression, map: Map[WrappedExpression, VoidExpr], trace: Seq[Statement]): Seq[Statement] = {
      val voidExpr = map(e) 
      val newTrace = voidExpr.stmt +: trace
      if (voidExpr.voidDeps.nonEmpty) rec(voidExpr.voidDeps.head, map, newTrace) else newTrace
    }
    rec(expr, voidExprs, Seq())
  }

  def run(c: Circuit): Circuit = {
    val errors = collection.mutable.ArrayBuffer[PassException]()


    def checkInitM(m: Module): Unit = {
      val voidExprs = collection.mutable.HashMap[WrappedExpression, VoidExpr]()

      def hasVoidExpr(e: Expression): (Boolean, Seq[Expression]) = {
        var void = false
        val voidDeps = collection.mutable.ArrayBuffer[Expression]()
        def hasVoid(e: Expression): Expression = {
          e match {
            case e: WVoid =>
              void = true
              e
            case (_: WRef | _: WSubField) =>
              if (voidExprs.contains(e)) {
                void = true
                voidDeps += e
              }
              e
            case e => e map hasVoid
          }
        }
        hasVoid(e)
        (void, voidDeps)
      }
      def checkInitS(s: Statement): Statement = {
        s match {
          case con: Connect =>
            val (hasVoid, voidDeps) = hasVoidExpr(con.expr)
            if (hasVoid) voidExprs(con.loc) = VoidExpr(con, voidDeps)
            con
          case node: DefNode =>
            val (hasVoid, voidDeps) = hasVoidExpr(node.value)
            if (hasVoid) {
              val nodeRef = WRef(node.name, node.value.tpe, NodeKind(), MALE)
              voidExprs(nodeRef) = VoidExpr(node, voidDeps)
            }
            node
          case s => s map checkInitS
        }
      }
      checkInitS(m.body)

      // Build Up Errors
      for ((expr, _) <- voidExprs) {
        getDeclaration(m, expr.e1) match {
          case node: DefNode => // Ignore nodes
          case decl: IsDeclaration =>
            val trace = getTrace(expr, voidExprs.toMap)
            errors += new RefNotInitializedException(decl.info, m.name, decl.name, trace)
        }
      }
    }

    c.modules foreach { m =>
      m match {
        case m: Module => checkInitM(m)
        case m => // Do nothing
      }
    }

    if (errors.nonEmpty) throw new PassExceptions(errors)
    c
  }
}