fix(compiler): Fix gate inlining [LNG-253] (#924)

* Fix gate inlining

* Remake stream gate inlining, fix unit tests

* Fix: add flat inline

* Refactor, add comments

compiler/src/test/scala/aqua/compiler/AquaCompilerSpec.scala

@@ -1,14 +1,6 @@
 package aqua.compiler
 
-import aqua.model.{
-  CallModel,
-  ForModel,
-  FunctorModel,
-  IntoIndexModel,
-  LiteralModel,
-  ValueModel,
-  VarModel
-}
+import aqua.model.{CallModel, ForModel, FunctorModel, LiteralModel, ValueModel, VarModel}
 import aqua.model.transform.ModelBuilder
 import aqua.model.transform.TransformConfig
 import aqua.model.transform.Transform
@@ -115,8 +107,8 @@ class AquaCompilerSpec extends AnyFlatSpec with Matchers {
 
   private val init = LiteralModel.fromRaw(ValueRaw.InitPeerId)
 
-  private def join(vm: VarModel, idx: ValueModel) =
-    ResBuilder.join(vm, idx, init)
+  private def join(vm: VarModel, size: ValueModel) =
+    ResBuilder.join(vm, size, init)
 
   "aqua compiler" should "create right topology" in {
 
@@ -156,6 +148,7 @@ class AquaCompilerSpec extends AnyFlatSpec with Matchers {
     val canonResult = VarModel("-" + results.name + "-fix-0", CanonStreamType(resultsType.element))
     val flatResult = VarModel("-results-flat-0", ArrayType(ScalarType.string))
     val initPeer = LiteralModel.fromRaw(ValueRaw.InitPeerId)
+    val sizeVar = VarModel("results_size", LiteralType.unsigned)
     val retVar = VarModel("ret", ScalarType.string)
 
     val expected =
@@ -195,7 +188,13 @@ class AquaCompilerSpec extends AnyFlatSpec with Matchers {
                   )
                 )
               ),
-              join(results, LiteralModel.fromRaw(LiteralRaw.number(2))),
+              ResBuilder.add(
+                LiteralModel.number(2),
+                LiteralModel.number(1),
+                sizeVar,
+                initPeer
+              ),
+              join(results, sizeVar),
               CanonRes(results, init, CallModel.Export(canonResult.name, canonResult.`type`)).leaf,
               ApRes(
                 canonResult,

model/inline/src/main/scala/aqua/model/inline/RawValueInliner.scala

@@ -6,12 +6,12 @@ import aqua.model.*
 import aqua.model.inline.raw.{
   ApplyBinaryOpRawInliner,
   ApplyFunctorRawInliner,
-  ApplyGateRawInliner,
   ApplyPropertiesRawInliner,
   ApplyUnaryOpRawInliner,
   CallArrowRawInliner,
   CollectionRawInliner,
-  MakeAbilityRawInliner
+  MakeAbilityRawInliner,
+  StreamGateInliner
 }
 import aqua.raw.ops.*
 import aqua.raw.value.*
@@ -48,9 +48,6 @@ object RawValueInliner extends Logging {
       case alr: ApplyPropertyRaw =>
         ApplyPropertiesRawInliner(alr, propertiesAllowed)
 
-      case agr: ApplyGateRaw =>
-        ApplyGateRawInliner(agr, propertiesAllowed)
-
       case cr: CollectionRaw =>
         CollectionRawInliner(cr, propertiesAllowed)
 

model/inline/src/main/scala/aqua/model/inline/raw/ApplyPropertiesRawInliner.scala

@@ -18,6 +18,7 @@ import cats.syntax.bifunctor.*
 import cats.syntax.foldable.*
 import cats.syntax.monoid.*
 import cats.syntax.traverse.*
+import cats.syntax.option.*
 import scribe.Logging
 
 object ApplyPropertiesRawInliner extends RawInliner[ApplyPropertyRaw] with Logging {
@@ -48,17 +49,6 @@ object ApplyPropertiesRawInliner extends RawInliner[ApplyPropertyRaw] with Loggi
     }
   }
 
-  private def removeProperties[S: Mangler](
-    varModel: VarModel
-  ): State[S, (VarModel, Inline)] = {
-    for {
-      nn <- Mangler[S].findAndForbidName(varModel.name + "_flat")
-    } yield {
-      val flatten = VarModel(nn, varModel.`type`)
-      flatten -> Inline.tree(FlattenModel(varModel, flatten.name).leaf)
-    }
-  }
-
   private def unfoldAbilityProperty[S: Mangler: Exports: Arrows](
     varModel: VarModel,
     abilityType: NamedType,
@@ -143,9 +133,7 @@ object ApplyPropertiesRawInliner extends RawInliner[ApplyPropertyRaw] with Loggi
 
       case f @ FunctorRaw(_, _) =>
         for {
-          flattenVI <-
-            if (varModel.properties.nonEmpty) removeProperties(varModel)
-            else State.pure(varModel, Inline.empty)
+          flattenVI <- removeProperties(varModel)
           (flatten, inline) = flattenVI
           newVI <- ApplyFunctorRawInliner(flatten, f)
         } yield {
@@ -157,9 +145,7 @@ object ApplyPropertiesRawInliner extends RawInliner[ApplyPropertyRaw] with Loggi
 
       case ic @ IntoCopyRaw(_, _) =>
         for {
-          flattenVI <-
-            if (varModel.properties.nonEmpty) removeProperties(varModel)
-            else State.pure(varModel, Inline.empty)
+          flattenVI <- removeProperties(varModel)
           (flatten, inline) = flattenVI
           newVI <- ApplyIntoCopyRawInliner(flatten, ic)
         } yield {
@@ -182,15 +168,31 @@ object ApplyPropertiesRawInliner extends RawInliner[ApplyPropertyRaw] with Loggi
         unfold(vr, propertiesAllowed = false).flatMap {
           case (vm @ VarModel(_, _, _), inline) if vm.properties.nonEmpty =>
             removeProperties(vm).map { case (vf, inlf) =>
-              PropertyRawWithModel(iir, Option(IntoIndexModel(vf.name, t))) -> Inline(
+              PropertyRawWithModel(
+                iir,
+                IntoIndexModel
+                  .fromValueModel(vf, t)
+                  .getOrElse(
+                    internalError(s"Unexpected: could not convert ($vf) to IntoIndexModel")
+                  )
+                  .some
+              ) -> Inline(
                 inline.predo ++ inlf.predo,
                 mergeMode = SeqMode
               )
             }
-          case (VarModel(name, _, _), inline) =>
-            State.pure(PropertyRawWithModel(iir, Option(IntoIndexModel(name, t))) -> inline)
-          case (LiteralModel(literal, _), inline) =>
-            State.pure(PropertyRawWithModel(iir, Option(IntoIndexModel(literal, t))) -> inline)
+          case (vm, inline) =>
+            (
+              PropertyRawWithModel(
+                iir,
+                IntoIndexModel
+                  .fromValueModel(vm, t)
+                  .getOrElse(
+                    internalError(s"Unexpected: could not convert ($vm) to IntoIndexModel")
+                  )
+                  .some
+              ) -> inline
+            ).pure
         }
 
       case p => State.pure(PropertyRawWithModel(p, None) -> Inline.empty)
@@ -246,31 +248,88 @@ object ApplyPropertiesRawInliner extends RawInliner[ApplyPropertyRaw] with Loggi
     }
   }
 
+  /**
+   * Unfold `stream[idx]`
+   */
+  private def unfoldStreamGate[S: Mangler: Exports: Arrows](
+    streamName: String,
+    streamType: StreamType,
+    idx: ValueRaw
+  ): State[S, (VarModel, Inline)] = for {
+    /**
+     * Inline idx
+     */
+    idxInlined <- unfold(idx)
+    (idxVM, idxInline) = idxInlined
+    /**
+     * Inline size which is `idx + 1`
+     * TODO: Refactor to apply optimizations
+     */
+    sizeName <- Mangler[S].findAndForbidName(s"${streamName}_size")
+    sizeVar = VarModel(sizeName, idxVM.`type`)
+    sizeInline = CallServiceModel(
+      "math",
+      funcName = "add",
+      args = List(idxVM, LiteralModel.number(1)),
+      result = sizeVar
+    ).leaf
+    gateInlined <- StreamGateInliner(streamName, streamType, sizeVar)
+    (gateVM, gateInline) = gateInlined
+    /**
+     * Remove properties from idx
+     * as we need to use it in index
+     * TODO: Do not generate it
+     *       if it is not needed,
+     *       e.g. in `join`
+     */
+    idxFlattened <- idxVM match {
+      case vr: VarModel => removeProperties(vr)
+      case _ => (idxVM, Inline.empty).pure[State[S, *]]
+    }
+    (idxFlat, idxFlatInline) = idxFlattened
+    /**
+     * Construct stream[idx]
+     */
+    gate = gateVM.withProperty(
+      IntoIndexModel
+        .fromValueModel(idxFlat, streamType.element)
+        .getOrElse(
+          internalError(s"Unexpected: could not convert ($idxFlat) to IntoIndexModel")
+        )
+    )
+  } yield gate -> Inline(
+    idxInline.predo
+      .append(sizeInline) ++
+      gateInline.predo ++
+      idxFlatInline.predo,
+    mergeMode = SeqMode
+  )
+
   private def unfoldRawWithProperties[S: Mangler: Exports: Arrows](
     raw: ValueRaw,
     properties: Chain[PropertyRaw],
     propertiesAllowed: Boolean
   ): State[S, (ValueModel, Inline)] = {
-    ((raw, properties.headOption) match {
-      case (vr @ VarRaw(_, st @ StreamType(_)), Some(IntoIndexRaw(idx, _))) =>
+    ((raw, properties.uncons) match {
+      /**
+       * To inline
+       */
+      case (
+            vr @ VarRaw(_, st @ StreamType(_)),
+            Some(IntoIndexRaw(idx, _), otherProperties)
+          ) =>
         unfold(vr).flatMap {
           case (VarModel(nameVM, _, _), inl) =>
-            val gateRaw = ApplyGateRaw(nameVM, st, idx)
-            unfold(gateRaw).flatMap {
-              case (gateResVal: VarModel, gateResInline) =>
-                unfoldProperties(gateResInline, gateResVal, properties, propertiesAllowed).map {
-                  case (v, i) =>
-                    v -> Inline(
-                      inl.predo ++ i.predo,
-                      mergeMode = SeqMode
-                    )
-                }
-              case (v, i) =>
-                // what if pass nil as stream argument?
-                internalError(
-                  s"Unfolded stream ($gateRaw) cannot be a literal"
-                )
-            }
+            for {
+              gateInlined <- unfoldStreamGate(nameVM, st, idx)
+              (gateVM, gateInline) = gateInlined
+              propsInlined <- unfoldProperties(
+                gateInline,
+                gateVM,
+                otherProperties,
+                propertiesAllowed
+              )
+            } yield propsInlined
           case l =>
             internalError(
               s"Unfolded stream ($vr) cannot be a literal"
@@ -299,6 +358,19 @@ object ApplyPropertiesRawInliner extends RawInliner[ApplyPropertyRaw] with Loggi
 
   }
 
+  /**
+   * Remove properties from the var and return a new var without them
+   */
+  private def removeProperties[S: Mangler](
+    varModel: VarModel
+  ): State[S, (VarModel, Inline)] =
+    if (varModel.properties.isEmpty) (varModel, Inline.empty).pure
+    else
+      for {
+        nn <- Mangler[S].findAndForbidName(varModel.name + "_flat")
+        flatten = VarModel(nn, varModel.`type`)
+      } yield flatten -> Inline.tree(FlattenModel(varModel, flatten.name).leaf)
+
   override def apply[S: Mangler: Exports: Arrows](
     apr: ApplyPropertyRaw,
     propertiesAllowed: Boolean

model/inline/src/main/scala/aqua/model/inline/raw/StreamGateInliner.scala

@@ -1,9 +1,10 @@
 package aqua.model.inline.raw
 
+import aqua.errors.Errors.internalError
 import aqua.model.*
 import aqua.model.inline.Inline
 import aqua.model.inline.state.{Arrows, Exports, Mangler}
-import aqua.raw.value.{ApplyGateRaw, LiteralRaw, VarRaw}
+import aqua.raw.value.{LiteralRaw, VarRaw}
 import aqua.model.inline.RawValueInliner.unfold
 import aqua.types.{ArrayType, CanonStreamType, ScalarType, StreamType}
 
@@ -11,16 +12,17 @@ import cats.data.State
 import cats.data.Chain
 import cats.syntax.monoid.*
 import cats.syntax.option.*
+import cats.syntax.applicative.*
 import scribe.Logging
+import cats.instances.stream
 
-object ApplyGateRawInliner extends RawInliner[ApplyGateRaw] with Logging {
+object StreamGateInliner extends Logging {
 
   /**
-   * To wait for the element of a stream by the given index, the following model is generated:
-   * (seq
+   * To wait for size elements of a stream,
+   * the following model is generated:
    * (seq
    *  (seq
-   *   (call <peer> ("math" "add") [0 1] stream_incr)
    *   (fold $stream s
    *    (seq
    *     (seq
@@ -28,7 +30,7 @@ object ApplyGateRawInliner extends RawInliner[ApplyGateRaw] with Logging {
    *      (canon <peer> $stream_test  #stream_iter_canon)
    *     )
    *     (xor
-   *      (match #stream_iter_canon.length stream_incr
+   *      (match #stream_iter_canon.length size
    *       (null)
    *      )
    *      (next s)
@@ -36,17 +38,15 @@ object ApplyGateRawInliner extends RawInliner[ApplyGateRaw] with Logging {
    *    )
    *    (never)
    *   )
+   *   (canon <peer> $stream_test  #stream_result_canon)
    *  )
-   *  (canon <peer> $stream_test  #stream_result_canon)
-   * )
-   * (ap #stream_result_canon stream_gate)
+   *  (ap #stream_result_canon stream_gate)
    * )
    */
   def joinStreamOnIndexModel(
     streamName: String,
     streamType: StreamType,
-    idxModel: ValueModel,
-    idxIncrName: String,
+    sizeModel: ValueModel,
     testName: String,
     iterName: String,
     canonName: String,
@@ -55,16 +55,10 @@ object ApplyGateRawInliner extends RawInliner[ApplyGateRaw] with Logging {
   ): OpModel.Tree = {
     val varSTest = VarModel(testName, streamType)
     val iter = VarModel(iterName, streamType.element)
-
     val iterCanon = VarModel(iterCanonName, CanonStreamType(streamType.element))
-
-    val resultCanon =
-      VarModel(canonName, CanonStreamType(streamType.element))
-
-    val incrVar = VarModel(idxIncrName, ScalarType.u32)
+    val resultCanon = VarModel(canonName, CanonStreamType(streamType.element))
 
     RestrictionModel(varSTest.name, streamType).wrap(
-      increment(idxModel, incrVar),
       ForModel(iter.name, VarModel(streamName, streamType), ForModel.Mode.Never.some).wrap(
         PushToStreamModel(
           iter,
@@ -77,8 +71,10 @@ object ApplyGateRawInliner extends RawInliner[ApplyGateRaw] with Logging {
         XorModel.wrap(
           MatchMismatchModel(
             iterCanon
-              .copy(properties = Chain.one(FunctorModel("length", ScalarType.`u32`))),
-            incrVar,
+              .withProperty(
+                FunctorModel("length", ScalarType.`u32`)
+              ),
+            sizeModel,
             true
           ).leaf,
           NextModel(iter.name).leaf
@@ -95,25 +91,23 @@ object ApplyGateRawInliner extends RawInliner[ApplyGateRaw] with Logging {
     )
   }
 
-  override def apply[S: Mangler: Exports: Arrows](
-    afr: ApplyGateRaw,
-    propertyAllowed: Boolean
-  ): State[S, (ValueModel, Inline)] =
+  def apply[S: Mangler: Exports: Arrows](
+    streamName: String,
+    streamType: StreamType,
+    sizeModel: ValueModel
+  ): State[S, (VarModel, Inline)] =
     for {
-      uniqueCanonName <- Mangler[S].findAndForbidName(afr.name + "_result_canon")
-      uniqueResultName <- Mangler[S].findAndForbidName(afr.name + "_gate")
-      uniqueTestName <- Mangler[S].findAndForbidName(afr.name + "_test")
-      uniqueIdxIncr <- Mangler[S].findAndForbidName(afr.name + "_incr")
-      uniqueIterCanon <- Mangler[S].findAndForbidName(afr.name + "_iter_canon")
-      uniqueIter <- Mangler[S].findAndForbidName(afr.name + "_fold_var")
-      idxFolded <- unfold(afr.idx)
-      (idxModel, idxInline) = idxFolded
+      uniqueCanonName <- Mangler[S].findAndForbidName(streamName + "_result_canon")
+      uniqueResultName <- Mangler[S].findAndForbidName(streamName + "_gate")
+      uniqueTestName <- Mangler[S].findAndForbidName(streamName + "_test")
+      uniqueIdxIncr <- Mangler[S].findAndForbidName(streamName + "_incr")
+      uniqueIterCanon <- Mangler[S].findAndForbidName(streamName + "_iter_canon")
+      uniqueIter <- Mangler[S].findAndForbidName(streamName + "_fold_var")
     } yield {
       val gate = joinStreamOnIndexModel(
-        streamName = afr.name,
-        streamType = afr.streamType,
-        idxModel = idxModel,
-        idxIncrName = uniqueIdxIncr,
+        streamName = streamName,
+        streamType = streamType,
+        sizeModel = sizeModel,
         testName = uniqueTestName,
         iterName = uniqueIter,
         canonName = uniqueCanonName,
@@ -121,24 +115,12 @@ object ApplyGateRawInliner extends RawInliner[ApplyGateRaw] with Logging {
         resultName = uniqueResultName
       )
 
-      val tree = SeqModel.wrap(idxInline.predo.toList :+ gate)
-
-      val treeInline = Inline(predo = Chain.one(tree))
-
-      (
-        VarModel(uniqueResultName, ArrayType(afr.streamType.element)),
-        treeInline
+      val inline = Inline(predo = Chain.one(gate))
+      val value = VarModel(
+        uniqueResultName,
+        ArrayType(streamType.element)
       )
 
+      (value, inline)
     }
-
-  private def increment(v: ValueModel, result: VarModel) =
-    CallServiceModel(
-      LiteralModel("\"math\"", ScalarType.string),
-      "add",
-      CallModel(
-        v :: LiteralModel.fromRaw(LiteralRaw.number(1)) :: Nil,
-        CallModel.Export(result.name, result.`type`) :: Nil
-      )
-    ).leaf
 }

model/raw/src/main/scala/aqua/raw/value/ValueRaw.scala

@@ -58,8 +58,8 @@ object ValueRaw {
     errorType
   )
 
-  type ApplyRaw = ApplyGateRaw | ApplyPropertyRaw | CallArrowRaw | CollectionRaw |
-    ApplyBinaryOpRaw | ApplyUnaryOpRaw
+  type ApplyRaw = ApplyPropertyRaw | CallArrowRaw | CollectionRaw | ApplyBinaryOpRaw |
+    ApplyUnaryOpRaw
 }
 
 case class ApplyPropertyRaw(value: ValueRaw, property: PropertyRaw) extends ValueRaw {
@@ -94,22 +94,6 @@ object ApplyPropertyRaw {
     }
 }
 
-case class ApplyGateRaw(name: String, streamType: StreamType, idx: ValueRaw) extends ValueRaw {
-  override def baseType: Type = streamType
-
-  override def `type`: Type = idx.`type`
-
-  override def renameVars(map: Map[String, String]): ValueRaw =
-    copy(name = map.getOrElse(name, name), idx = idx.renameVars(map))
-
-  override def map(f: ValueRaw => ValueRaw): ValueRaw =
-    f(copy(idx = f(idx)))
-
-  override def toString: String = s"gate $name.$idx"
-
-  override def varNames: Set[String] = Set(name) ++ idx.varNames
-}
-
 case class VarRaw(name: String, baseType: Type) extends ValueRaw {
 
   override def map(f: ValueRaw => ValueRaw): ValueRaw = f(this)

model/res/src/test/scala/aqua/res/ResBuilder.scala

@@ -9,32 +9,22 @@ import cats.syntax.option.*
 
 object ResBuilder {
 
-  def join(stream: VarModel, onIdx: ValueModel, peer: ValueModel) = {
+  def join(stream: VarModel, sizeModel: ValueModel, peer: ValueModel) = {
     val testVM = VarModel(stream.name + "_test", stream.`type`)
     val testStreamType = stream.`type`.asInstanceOf[StreamType] // Unsafe
     val iter = VarModel(stream.name + "_fold_var", ScalarType.string)
     val canon = VarModel(stream.name + "_iter_canon", CanonStreamType(ScalarType.string))
     val canonRes = VarModel(stream.name + "_result_canon", CanonStreamType(ScalarType.string))
     val arrayRes = VarModel(stream.name + "_gate", ArrayType(ScalarType.string))
-    val idx = VarModel(stream.name + "_incr", ScalarType.u32)
 
     RestrictionRes(testVM.name, testStreamType).wrap(
-      CallServiceRes(
-        LiteralModel("\"math\"", ScalarType.string),
-        "add",
-        CallRes(
-          onIdx :: LiteralModel.fromRaw(LiteralRaw.number(1)) :: Nil,
-          Some(CallModel.Export(idx.name, idx.`type`))
-        ),
-        peer
-      ).leaf,
       FoldRes(iter.name, stream, ForModel.Mode.Never.some).wrap(
         ApRes(iter, CallModel.Export(testVM.name, testVM.`type`)).leaf,
         CanonRes(testVM, peer, CallModel.Export(canon.name, canon.`type`)).leaf,
         XorRes.wrap(
           MatchMismatchRes(
             canon.copy(properties = Chain.one(FunctorModel("length", ScalarType.u32))),
-            idx,
+            sizeModel,
             true
           ).leaf,
           NextRes(iter.name).leaf
@@ -45,4 +35,20 @@ object ResBuilder {
     )
   }
 
+  def add(
+    a: ValueModel,
+    b: ValueModel,
+    res: VarModel,
+    peer: ValueModel
+  ): ResolvedOp.Tree =
+    CallServiceRes(
+      LiteralModel.quote("math"),
+      "add",
+      CallRes(
+        a :: b :: Nil,
+        Some(CallModel.Export(res.name, res.`type`))
+      ),
+      peer
+    ).leaf
+
 }

model/src/main/scala/aqua/model/ValueModel.scala

@@ -157,6 +157,15 @@ case class IntoIndexModel(idx: String, `type`: Type) extends PropertyModel {
   )
 }
 
+object IntoIndexModel {
+
+  def fromValueModel(vm: ValueModel, `type`: Type): Option[IntoIndexModel] = vm match {
+    case VarModel(name, _, Chain.nil) => IntoIndexModel(name, `type`).some
+    case LiteralModel(value, _) => IntoIndexModel(value, `type`).some
+    case _ => none
+  }
+}
+
 case class VarModel(name: String, baseType: Type, properties: Chain[PropertyModel] = Chain.empty)
     extends ValueModel with Logging {
 
@@ -173,14 +182,13 @@ case class VarModel(name: String, baseType: Type, properties: Chain[PropertyMode
   private def deriveFrom(vm: VarModel): VarModel =
     vm.copy(properties = vm.properties ++ properties)
 
+  def withProperty(p: PropertyModel): VarModel =
+    copy(properties = properties :+ p)
+
   def intoField(field: String): Option[VarModel] = `type` match {
     case StructType(_, fields) =>
       fields(field)
-        .map(fieldType =>
-          copy(
-            properties = properties :+ IntoFieldModel(field, fieldType)
-          )
-        )
+        .map(fieldType => withProperty(IntoFieldModel(field, fieldType)))
     case _ => none
   }
 

model/transform/src/test/scala/aqua/model/transform/ModelBuilder.scala

@@ -8,7 +8,7 @@ import aqua.res.{CallRes, CallServiceRes, MakeRes}
 import aqua.types.{ArrayType, LiteralType, ScalarType}
 import aqua.types.StreamType
 import aqua.model.IntoIndexModel
-import aqua.model.inline.raw.ApplyGateRawInliner
+import aqua.model.inline.raw.StreamGateInliner
 import aqua.model.OnModel
 import aqua.model.FailModel
 import aqua.res.ResolvedOp
@@ -142,21 +142,20 @@ object ModelBuilder {
 
   /**
    * @param stream stream [[VarModel]]
-   * @param idx id [[ValueModel]]
-   * @return [[OpModel.Tree]] of join of `stream[idx]`
+   * @param size size [[ValueModel]]
+   * @return [[OpModel.Tree]] of join of size elements of stream
    */
-  def join(stream: VarModel, idx: ValueModel): OpModel.Tree =
+  def join(stream: VarModel, size: ValueModel): OpModel.Tree =
     stream match {
       case VarModel(
             streamName,
             streamType: StreamType,
             Chain.`nil`
           ) =>
-        ApplyGateRawInliner.joinStreamOnIndexModel(
+        StreamGateInliner.joinStreamOnIndexModel(
           streamName = streamName,
           streamType = streamType,
-          idxModel = idx,
-          idxIncrName = streamName + "_incr",
+          sizeModel = size,
           testName = streamName + "_test",
           iterName = streamName + "_fold_var",
           canonName = streamName + "_result_canon",
@@ -165,4 +164,12 @@ object ModelBuilder {
         )
       case _ => ???
     }
+
+  def add(a: ValueModel, b: ValueModel, res: VarModel): OpModel.Tree =
+    CallServiceModel(
+      "math",
+      "add",
+      args = List(a, b),
+      result = res
+    ).leaf
 }

model/transform/src/test/scala/aqua/model/transform/topology/TopologySpec.scala

@@ -25,22 +25,45 @@ class TopologySpec extends AnyFlatSpec with Matchers {
   import ModelBuilder.{join as joinModel, *}
   import ResBuilder.join as joinRes
 
-  def joinModelRes(streamEl: ValueRaw | ValueModel): (OpModel.Tree, ResolvedOp.Tree) =
+  def joinModelRes(
+    streamEl: ValueRaw | ValueModel
+  ): (Chain[OpModel.Tree], Chain[ResolvedOp.Tree]) =
     streamEl match {
       case vm: ValueModel => vm
       case vr: ValueRaw => ValueModel.fromRaw(vr)
     } match {
       case stream @ VarModel(name, baseType, IntoIndexModel(idx, idxType) ==: Chain.`nil`) =>
         val idxModel =
-          if (idx.forall(Character.isDigit)) LiteralModel(idx, idxType)
-          else VarModel(idx, idxType)
+          if (idx.forall(Character.isDigit)) LiteralModel(idx, ScalarType.u32)
+          else VarModel(idx, ScalarType.u32)
 
         val streamWithoutIdx = stream.copy(properties = Chain.`nil`)
 
-        (
-          joinModel(streamWithoutIdx, idxModel),
-          joinRes(streamWithoutIdx, idxModel, ValueModel.fromRaw(initPeer))
+        val sizeModel = VarModel(s"${name}_size", ScalarType.u32)
+        val sizeTree = ModelBuilder.add(
+          idxModel,
+          LiteralModel.number(1),
+          sizeModel
         )
+
+        val model = Chain(
+          sizeTree,
+          joinModel(streamWithoutIdx, sizeModel)
+        )
+
+        val sizeTreeResolved = ResBuilder.add(
+          idxModel,
+          LiteralModel.number(1),
+          sizeModel,
+          ValueModel.fromRaw(initPeer)
+        )
+
+        val resolved = Chain(
+          sizeTreeResolved,
+          joinRes(streamWithoutIdx, sizeModel, ValueModel.fromRaw(initPeer))
+        )
+
+        (model, resolved)
       case _ => ???
     }
 
@@ -462,54 +485,58 @@ class TopologySpec extends AnyFlatSpec with Matchers {
 
     val (joinModel, joinRes) = joinModelRes(streamEl)
 
+    val foldModel = foldPar(
+      "i",
+      valueArray,
+      OnModel(iRelay, Chain.empty).wrap(
+        XorModel.wrap(
+          callModel(2, CallModel.Export(streamRaw.name, streamRaw.`type`) :: Nil),
+          OnModel(initPeer, Chain.one(relay)).wrap(
+            callModel(4, Nil, Nil)
+          )
+        )
+      )
+    )
     val init = SeqModel.wrap(
       DeclareStreamModel(stream).leaf,
       OnModel(initPeer, Chain.one(relay)).wrap(
-        foldPar(
-          "i",
-          valueArray,
-          OnModel(iRelay, Chain.empty).wrap(
-            XorModel.wrap(
-              callModel(2, CallModel.Export(streamRaw.name, streamRaw.`type`) :: Nil),
-              OnModel(initPeer, Chain.one(relay)).wrap(
-                callModel(4, Nil, Nil)
-              )
-            )
-          )
-        ),
-        joinModel,
-        callModel(3, Nil, streamRaw :: Nil)
+        foldModel +:
+          joinModel :+
+          callModel(3, Nil, streamRaw :: Nil)
       )
     )
 
     val proc = Topology.resolve(init).value
 
-    val expected = SeqRes.wrap(
-      through(relay),
-      ParRes.wrap(
-        FoldRes("i", valueArray, ForModel.Mode.Never.some).wrap(
-          ParRes.wrap(
-            // better if first relay will be outside `for`
-            SeqRes.wrap(
-              through(relay),
-              XorRes.wrap(
-                SeqRes.wrap(
-                  callRes(2, iRelay, Some(CallModel.Export(streamRaw.name, streamRaw.`type`))),
-                  through(relay),
-                  through(initPeer)
-                ),
-                SeqRes.wrap(
-                  through(relay),
-                  callRes(4, initPeer)
-                )
+    val foldRes = ParRes.wrap(
+      FoldRes("i", valueArray, ForModel.Mode.Never.some).wrap(
+        ParRes.wrap(
+          // better if first relay will be outside `for`
+          SeqRes.wrap(
+            through(relay),
+            XorRes.wrap(
+              SeqRes.wrap(
+                callRes(2, iRelay, Some(CallModel.Export(streamRaw.name, streamRaw.`type`))),
+                through(relay),
+                through(initPeer)
+              ),
+              SeqRes.wrap(
+                through(relay),
+                callRes(4, initPeer)
               )
-            ),
-            NextRes("i").leaf
-          )
+            )
+          ),
+          NextRes("i").leaf
         )
-      ),
-      joinRes,
-      callRes(3, initPeer, None, stream :: Nil)
+      )
+    )
+    val expected = SeqRes.wrap(
+      Chain(
+        through(relay),
+        foldRes
+      ) ++
+        joinRes :+
+        callRes(3, initPeer, None, stream :: Nil)
     )
 
     proc.equalsOrShowDiff(expected) should be(true)
@@ -543,42 +570,45 @@ class TopologySpec extends AnyFlatSpec with Matchers {
               )
             )
           )
-        ),
-        joinModel,
-        callModel(3, Nil, streamRaw :: Nil)
+        ) +:
+          joinModel :+
+          callModel(3, Nil, streamRaw :: Nil)
       )
     )
 
     val proc = Topology.resolve(init).value
 
-    val expected = SeqRes.wrap(
-      through(relay),
-      ParRes.wrap(
-        FoldRes("i", valueArray, ForModel.Mode.Never.some).wrap(
-          ParRes.wrap(
-            // better if first relay will be outside `for`
-            SeqRes.wrap(
-              through(relay),
+    val fold = ParRes.wrap(
+      FoldRes("i", valueArray, ForModel.Mode.Never.some).wrap(
+        ParRes.wrap(
+          // better if first relay will be outside `for`
+          SeqRes.wrap(
+            through(relay),
+            XorRes.wrap(
               XorRes.wrap(
-                XorRes.wrap(
-                  SeqRes.wrap(
-                    callRes(2, iRelay, Some(CallModel.Export(streamRaw.name, streamRaw.`type`))),
-                    through(relay),
-                    through(initPeer)
-                  )
-                ),
                 SeqRes.wrap(
+                  callRes(2, iRelay, Some(CallModel.Export(streamRaw.name, streamRaw.`type`))),
                   through(relay),
-                  callRes(4, initPeer)
+                  through(initPeer)
                 )
+              ),
+              SeqRes.wrap(
+                through(relay),
+                callRes(4, initPeer)
               )
-            ),
-            NextRes("i").leaf
-          )
+            )
+          ),
+          NextRes("i").leaf
         )
-      ),
-      joinRes,
-      callRes(3, initPeer, None, stream :: Nil)
+      )
+    )
+    val expected = SeqRes.wrap(
+      Chain(
+        through(relay),
+        fold
+      ) ++
+        joinRes :+
+        callRes(3, initPeer, None, stream :: Nil)
     )
 
     // println(Console.MAGENTA + init.show + Console.RESET)
@@ -804,9 +834,9 @@ class TopologySpec extends AnyFlatSpec with Matchers {
         OnModel(i, Chain.empty).wrap(
           callModel(1, CallModel.Export(used.name, used.`type`) :: Nil)
         )
-      ),
-      joinModel,
-      callModel(3, Nil, used :: Nil)
+      ) +:
+        joinModel :+
+        callModel(3, Nil, used :: Nil)
     )
 
     val proc = Topology.resolve(init).value
@@ -828,9 +858,9 @@ class TopologySpec extends AnyFlatSpec with Matchers {
             NextRes("i").leaf
           )
         )
-      ),
-      joinRes,
-      callRes(3, initPeer, None, ValueModel.fromRaw(used) :: Nil)
+      ) +:
+        joinRes :+
+        callRes(3, initPeer, None, ValueModel.fromRaw(used) :: Nil)
     )
 
     proc.equalsOrShowDiff(expected) should be(true)
@@ -844,46 +874,48 @@ class TopologySpec extends AnyFlatSpec with Matchers {
 
     val (joinModel, joinRes) = joinModelRes(usedWithIdx)
 
-    val init = OnModel(initPeer, Chain.one(relay)).wrap(
-      foldPar(
-        "i",
-        valueArray,
-        OnModel(i, Chain.empty).wrap(
-          XorModel.wrap(
-            callModel(1, CallModel.Export(used.name, used.`type`) :: Nil)
-          )
+    val foldModel = foldPar(
+      "i",
+      valueArray,
+      OnModel(i, Chain.empty).wrap(
+        XorModel.wrap(
+          callModel(1, CallModel.Export(used.name, used.`type`) :: Nil)
         )
-      ),
-      joinModel,
-      callModel(3, Nil, used :: Nil)
+      )
+    )
+    val init = OnModel(initPeer, Chain.one(relay)).wrap(
+      foldModel +:
+        joinModel :+
+        callModel(3, Nil, used :: Nil)
     )
 
     val proc = Topology.resolve(init).value
 
-    val expected = SeqRes.wrap(
-      ParRes.wrap(
-        FoldRes("i", ValueModel.fromRaw(valueArray), ForModel.Mode.Never.some).wrap(
-          ParRes.wrap(
-            SeqRes.wrap(
-              through(relay),
-              XorRes.wrap(
-                SeqRes.wrap(
-                  callRes(
-                    1,
-                    ValueModel.fromRaw(i),
-                    Some(CallModel.Export(used.name, used.`type`))
-                  ),
-                  through(relay),
-                  through(initPeer)
-                )
+    val foldRes = ParRes.wrap(
+      FoldRes("i", ValueModel.fromRaw(valueArray), ForModel.Mode.Never.some).wrap(
+        ParRes.wrap(
+          SeqRes.wrap(
+            through(relay),
+            XorRes.wrap(
+              SeqRes.wrap(
+                callRes(
+                  1,
+                  ValueModel.fromRaw(i),
+                  Some(CallModel.Export(used.name, used.`type`))
+                ),
+                through(relay),
+                through(initPeer)
               )
-            ),
-            NextRes("i").leaf
-          )
+            )
+          ),
+          NextRes("i").leaf
         )
-      ),
-      joinRes,
-      callRes(3, initPeer, None, ValueModel.fromRaw(used) :: Nil)
+      )
+    )
+    val expected = SeqRes.wrap(
+      foldRes +:
+        joinRes :+
+        callRes(3, initPeer, None, ValueModel.fromRaw(used) :: Nil)
     )
 
     proc.equalsOrShowDiff(expected) should be(true)