// SPDX-License-Identifier: Apache-2.0

package firrtl.passes

// Datastructures
import firrtl.Implicits.width2constraint
import firrtl.Mappers._
import firrtl.Utils._
import firrtl._
import firrtl.annotations._
import firrtl.constraint.{ConstraintSolver, IsMax}
import firrtl.ir._
import firrtl.options.Dependency

object InferWidths {
  def apply(): InferWidths = new InferWidths()
  def run(c:         Circuit):      Circuit = new InferWidths().run(c)(new ConstraintSolver)
  def execute(state: CircuitState): CircuitState = new InferWidths().execute(state)
}

case class WidthGeqConstraintAnnotation(loc: ReferenceTarget, exp: ReferenceTarget) extends Annotation {
  def update(renameMap: RenameMap): Seq[WidthGeqConstraintAnnotation] = {
    val newLoc :: newExp :: Nil = Seq(loc, exp).map { target =>
      renameMap.get(target) match {
        case None           => Some(target)
        case Some(Seq())    => None
        case Some(Seq(one)) => Some(one)
        case Some(many) =>
          throw new Exception(
            s"Target below is an AggregateType, which " +
              "is not supported by WidthGeqConstraintAnnotation\n" + target.prettyPrint()
          )
      }
    }

    (newLoc, newExp) match {
      case (Some(l: ReferenceTarget), Some(e: ReferenceTarget)) => Seq(WidthGeqConstraintAnnotation(l, e))
      case _ => Seq.empty
    }
  }
}

/** Infers the widths of all signals with unknown widths
  *
  * Is a global width inference algorithm
  * - Instances of the same module with unknown input port widths will be assigned the
  *   largest width of all assignments to each of its instance ports
  * - If you don't want the global inference behavior, then be sure to define all your input widths
  *
  * Infers the smallest width is larger than all assigned widths to a signal
  * - Note that this means that dummy assignments that are overwritten by last-connect-semantics
  *   can still influence width inference
  * - E.g.
  *   wire x: UInt
  *   x <= UInt<5>(15)
  *   x <= UInt<1>(1)
  *
  *   Since width inference occurs before lowering, it infers x's width to be 5 but with an assignment of UInt(1):
  *
  *   wire x: UInt<5>
  *   x <= UInt<1>(1)
  *
  * Uses firrtl.constraint package to infer widths
  */
class InferWidths extends Transform with ResolvedAnnotationPaths with DependencyAPIMigration {

  override def prerequisites =
    Seq(
      Dependency(passes.ResolveKinds),
      Dependency(passes.InferTypes),
      Dependency(passes.ResolveFlows),
      Dependency[passes.InferBinaryPoints],
      Dependency[passes.TrimIntervals]
    ) ++ firrtl.stage.Forms.MinimalHighForm
  override def invalidates(a: Transform) = false

  val annotationClasses = Seq(classOf[WidthGeqConstraintAnnotation])

  private def addTypeConstraints(
    r1: ReferenceTarget,
    r2: ReferenceTarget
  )(t1: Type,
    t2: Type
  )(
    implicit constraintSolver: ConstraintSolver
  ): Unit = (t1, t2) match {
    case (UIntType(w1), UIntType(w2)) => constraintSolver.addGeq(w1, w2, r1.prettyPrint(""), r2.prettyPrint(""))
    case (SIntType(w1), SIntType(w2)) => constraintSolver.addGeq(w1, w2, r1.prettyPrint(""), r2.prettyPrint(""))
    case (ClockType, ClockType)       =>
    case (FixedType(w1, p1), FixedType(w2, p2)) =>
      constraintSolver.addGeq(p1, p2, r1.prettyPrint(""), r2.prettyPrint(""))
      constraintSolver.addGeq(w1, w2, r1.prettyPrint(""), r2.prettyPrint(""))
    case (IntervalType(l1, u1, p1), IntervalType(l2, u2, p2)) =>
      constraintSolver.addGeq(p1, p2, r1.prettyPrint(""), r2.prettyPrint(""))
      constraintSolver.addLeq(l1, l2, r1.prettyPrint(""), r2.prettyPrint(""))
      constraintSolver.addGeq(u1, u2, r1.prettyPrint(""), r2.prettyPrint(""))
    case (AnalogType(w1), AnalogType(w2)) =>
      constraintSolver.addGeq(w1, w2, r1.prettyPrint(""), r2.prettyPrint(""))
      constraintSolver.addGeq(w2, w1, r1.prettyPrint(""), r2.prettyPrint(""))
    case (t1: BundleType, t2: BundleType) =>
      (t1.fields.zip(t2.fields)).foreach {
        case (f1, f2) =>
          (f1.flip, f2.flip) match {
            case (Default, Default) => addTypeConstraints(r1.field(f1.name), r2.field(f2.name))(f1.tpe, f2.tpe)
            case (Flip, Flip)       => addTypeConstraints(r2.field(f2.name), r1.field(f1.name))(f2.tpe, f1.tpe)
            case _                  => sys.error("Shouldn't be here")
          }
      }
    case (t1: VectorType, t2: VectorType) => addTypeConstraints(r1.index(0), r2.index(0))(t1.tpe, t2.tpe)
    case (AsyncResetType, AsyncResetType) => Nil
    case (ResetType, _)                   => Nil
    case (_, ResetType)                   => Nil
    case _                                => throwInternalError("Shouldn't be here")
  }

  private def addExpConstraints(e: Expression)(implicit constraintSolver: ConstraintSolver): Expression =
    e.map(addExpConstraints) match {
      case m @ Mux(p, tVal, fVal, t) =>
        constraintSolver.addGeq(getWidth(p), Closed(1), "mux predicate", "1.W")
        m
      case other => other
    }

  private def addStmtConstraints(
    mt: ModuleTarget
  )(s:  Statement
  )(
    implicit constraintSolver: ConstraintSolver
  ): Statement = s.map(addExpConstraints) match {
    case c: Connect =>
      val n = get_size(c.loc.tpe)
      val locs = create_exps(c.loc)
      val exps = create_exps(c.expr)
      (locs.zip(exps)).foreach {
        case (loc, exp) =>
          to_flip(flow(loc)) match {
            case Default => addTypeConstraints(Target.asTarget(mt)(loc), Target.asTarget(mt)(exp))(loc.tpe, exp.tpe)
            case Flip    => addTypeConstraints(Target.asTarget(mt)(exp), Target.asTarget(mt)(loc))(exp.tpe, loc.tpe)
          }
      }
      c
    case pc: PartialConnect =>
      val ls = get_valid_points(pc.loc.tpe, pc.expr.tpe, Default, Default)
      val locs = create_exps(pc.loc)
      val exps = create_exps(pc.expr)
      ls.foreach {
        case (x, y) =>
          val loc = locs(x)
          val exp = exps(y)
          to_flip(flow(loc)) match {
            case Default => addTypeConstraints(Target.asTarget(mt)(loc), Target.asTarget(mt)(exp))(loc.tpe, exp.tpe)
            case Flip    => addTypeConstraints(Target.asTarget(mt)(exp), Target.asTarget(mt)(loc))(exp.tpe, loc.tpe)
          }
      }
      pc
    case r: DefRegister =>
      if (r.reset.tpe != AsyncResetType) {
        addTypeConstraints(Target.asTarget(mt)(r.reset), mt.ref("1"))(r.reset.tpe, UIntType(IntWidth(1)))
      }
      addTypeConstraints(mt.ref(r.name), Target.asTarget(mt)(r.init))(r.tpe, r.init.tpe)
      r
    case a @ Attach(_, exprs) =>
      val widths = exprs.map(e => (e, getWidth(e.tpe)))
      val maxWidth = IsMax(widths.map(x => width2constraint(x._2)))
      widths.foreach {
        case (e, w) =>
          constraintSolver.addGeq(
            w,
            CalcWidth(maxWidth),
            Target.asTarget(mt)(e).prettyPrint(""),
            mt.ref(a.serialize).prettyPrint("")
          )
      }
      a
    case c: Conditionally =>
      addTypeConstraints(Target.asTarget(mt)(c.pred), mt.ref("1.W"))(c.pred.tpe, UIntType(IntWidth(1)))
      c.map(addStmtConstraints(mt))
    case x => x.map(addStmtConstraints(mt))
  }
  private def fixWidth(w: Width)(implicit constraintSolver: ConstraintSolver): Width = constraintSolver.get(w) match {
    case Some(Closed(x)) if trim(x).isWhole => IntWidth(x.toBigInt)
    case None                               => w
    case _                                  => sys.error("Shouldn't be here")
  }
  private def fixType(t: Type)(implicit constraintSolver: ConstraintSolver): Type = t.map(fixType).map(fixWidth) match {
    case IntervalType(l, u, p) =>
      val (lx, ux) = (constraintSolver.get(l), constraintSolver.get(u)) match {
        case (Some(x: Bound), Some(y: Bound)) => (x, y)
        case (None, None) => (l, u)
        case x            => sys.error(s"Shouldn't be here: $x")

      }
      IntervalType(lx, ux, fixWidth(p))
    case FixedType(w, p) => FixedType(w, fixWidth(p))
    case x               => x
  }
  private def fixStmt(s: Statement)(implicit constraintSolver: ConstraintSolver): Statement =
    s.map(fixStmt).map(fixType)
  private def fixPort(p: Port)(implicit constraintSolver: ConstraintSolver): Port = {
    Port(p.info, p.name, p.direction, fixType(p.tpe))
  }

  def run(c: Circuit)(implicit constraintSolver: ConstraintSolver): Circuit = {
    val ct = CircuitTarget(c.main)
    c.modules.foreach(m => m.map(addStmtConstraints(ct.module(m.name))))
    constraintSolver.solve()
    val ret = InferTypes.run(
      c.copy(modules =
        c.modules.map(
          _.map(fixPort)
            .map(fixStmt)
        )
      )
    )
    constraintSolver.clear()
    ret
  }

  def execute(state: CircuitState): CircuitState = {
    implicit val constraintSolver = new ConstraintSolver()

    val circuitName = state.circuit.main
    val typeMap = new collection.mutable.HashMap[ReferenceTarget, Type]

    def getDeclTypes(modName: String)(stmt: Statement): Unit = {
      val pairOpt = stmt match {
        case w: DefWire      => Some(w.name -> w.tpe)
        case r: DefRegister  => Some(r.name -> r.tpe)
        case n: DefNode      => Some(n.name -> n.value.tpe)
        case i: WDefInstance => Some(i.name -> i.tpe)
        case m: DefMemory    => Some(m.name -> MemPortUtils.memType(m))
        case other => None
      }
      pairOpt.foreach {
        case (ref, tpe) =>
          typeMap += (ReferenceTarget(circuitName, modName, Nil, ref, Nil) -> tpe)
      }
      stmt.foreachStmt(getDeclTypes(modName))
    }

    if (state.annotations.exists(_.isInstanceOf[WidthGeqConstraintAnnotation])) {
      state.circuit.modules.foreach { mod =>
        mod.ports.foreach { port =>
          typeMap += (ReferenceTarget(circuitName, mod.name, Nil, port.name, Nil) -> port.tpe)
        }
        mod.foreachStmt(getDeclTypes(mod.name))
      }
    }

    state.annotations.foreach {
      case anno: WidthGeqConstraintAnnotation if anno.loc.isLocal && anno.exp.isLocal =>
        val locType :: expType :: Nil = Seq(anno.loc, anno.exp).map { target =>
          val baseType = typeMap.getOrElse(
            target.copy(component = Seq.empty),
            throw new Exception(
              s"Target below from WidthGeqConstraintAnnotation was not found\n" + target.prettyPrint()
            )
          )
          val leafType = target.componentType(baseType)
          if (leafType.isInstanceOf[AggregateType]) {
            throw new Exception(
              s"Target below is an AggregateType, which " +
                "is not supported by WidthGeqConstraintAnnotation\n" + target.prettyPrint()
            )
          }

          leafType
        }

        //get_constraints_t(locType, expType)
        addTypeConstraints(anno.loc, anno.exp)(locType, expType)
      case other =>
    }

    state.copy(circuit = run(state.circuit))
  }

}
