From 0626d306b3928648a9fa17dcce6fbed7a3cb0745 Mon Sep 17 00:00:00 2001
From: Denys Zadorozhnyi <denys@zadorozhnyi.com>
Date: Thu, 30 Apr 2020 18:25:25 +0300
Subject: [PATCH 01/23] start drafting buy order contract; update compiler;

---
 build.sbt                                     |  2 +-
 .../scala/org/ergoplatform/playground.scala   |  3 +
 .../playgroundenv/dsl/BoxDsl.scala            | 31 +++++--
 .../playgroundenv/dsl/TypesDsl.scala          |  4 +
 .../utils/ErgoScriptCompiler.scala            | 27 ------
 .../AssetsAtomicExchangePlayground.scala      | 14 +--
 .../playgrounds/examples/DEXPlayground.scala  | 92 ++++++++++++-------
 7 files changed, 95 insertions(+), 78 deletions(-)
 delete mode 100644 playground-env/src/main/scala/org/ergoplatform/playgroundenv/utils/ErgoScriptCompiler.scala

diff --git a/build.sbt b/build.sbt
index f2748ca..877e5e2 100644
--- a/build.sbt
+++ b/build.sbt
@@ -27,7 +27,7 @@ dynverSeparator in ThisBuild := "-"
 lazy val allConfigDependency = "compile->compile;test->test"
 
 lazy val dependencies = Seq(
-  "org.ergoplatform" %% "ergo-scala-compiler" % "0.0.0-32-aaadbee1-SNAPSHOT",
+  "org.ergoplatform" %% "ergo-scala-compiler" % "0.0.0-41-13995374-SNAPSHOT",
   "org.ergoplatform" %% "ergo-appkit" % "develop-d77acfb8-SNAPSHOT"
 )
 
diff --git a/playground-env/src/main/scala/org/ergoplatform/playground.scala b/playground-env/src/main/scala/org/ergoplatform/playground.scala
index d47dee0..0ef8751 100644
--- a/playground-env/src/main/scala/org/ergoplatform/playground.scala
+++ b/playground-env/src/main/scala/org/ergoplatform/playground.scala
@@ -7,9 +7,12 @@ import org.ergoplatform.playgroundenv.dsl.{
   TypesDsl
 }
 import sigmastate.Values.{SigmaPropConstant, SigmaPropValue}
+import sigmastate.eval.CompiletimeIRContext
 
 object playground extends GeneratorsDsl with TypesDsl with BoxDsl with TransactionDsl {
 
+  implicit override protected def IR = new CompiletimeIRContext()
+
   val MinTxFee: Long = 1000 * 1000
   val MinErg: Long   = 1000 * 1000
 
diff --git a/playground-env/src/main/scala/org/ergoplatform/playgroundenv/dsl/BoxDsl.scala b/playground-env/src/main/scala/org/ergoplatform/playgroundenv/dsl/BoxDsl.scala
index 6693867..86f65ec 100644
--- a/playground-env/src/main/scala/org/ergoplatform/playgroundenv/dsl/BoxDsl.scala
+++ b/playground-env/src/main/scala/org/ergoplatform/playgroundenv/dsl/BoxDsl.scala
@@ -5,6 +5,7 @@ import org.ergoplatform.playgroundenv.models.TokenAmount
 import org.ergoplatform.{ErgoBox, ErgoBoxCandidate}
 import scorex.crypto.hash.Digest32
 import sigmastate.SType
+import sigmastate.SType.AnyOps
 import sigmastate.Values.{ByteArrayConstant, EvaluatedValue}
 import sigmastate.eval.Extensions._
 import sigmastate.eval._
@@ -35,14 +36,26 @@ trait BoxDsl extends TypesDsl {
     )
   }
 
-  private def liftVal[T](v: T): EvaluatedValue[SType] = v match {
-    case ba: Array[Byte] => ByteArrayConstant(ba)
+  private def liftVal(v: Any): EvaluatedValue[SType] = {
+    val (tV, newV) = v match {
+      case a: Array[Byte] => (Evaluation.rtypeOf(a.toColl).get, a.toColl)
+      case _              => (Evaluation.rtypeOf(v).get, v)
+    }
+    val elemTpe = Evaluation.rtypeToSType(tV)
+    IR.builder.mkConstant[SType](newV.asWrappedType, elemTpe)
   }
 
-  def Box[T](
+  private def liftRegVals(
+    regs: Seq[(NonMandatoryRegisterId, Any)]
+  ): Map[NonMandatoryRegisterId, EvaluatedValue[SType]] =
+    regs.map { t =>
+      (t._1, liftVal(t._2))
+    }.toMap
+
+  def Box(
     value: Long,
-    register: (NonMandatoryRegisterId, T),
-    script: ErgoContract
+    script: ErgoContract,
+    registers: (NonMandatoryRegisterId, Any)*
   ): ErgoBoxCandidate = {
     require(value > 0, s"box value shoulde be > 0, got $value")
     new ErgoBoxCandidate(
@@ -50,15 +63,15 @@ trait BoxDsl extends TypesDsl {
       script.ergoTree,
       0,
       Array[(TokenId, Long)]().toColl,
-      Map((register._1, liftVal(register._2)))
+      liftRegVals(registers)
     )
   }
 
   def Box(
     value: Long,
     token: (TokenInfo, Long),
-    register: (NonMandatoryRegisterId, Any),
-    script: ErgoContract
+    script: ErgoContract,
+    registers: (NonMandatoryRegisterId, Any)*
   ): ErgoBoxCandidate = {
     require(value > 0, s"box value shoulde be > 0, got $value")
     new ErgoBoxCandidate(
@@ -66,7 +79,7 @@ trait BoxDsl extends TypesDsl {
       script.ergoTree,
       0,
       Array[(TokenId, Long)]((Digest32 @@ token._1.tokenId.toArray, token._2)).toColl,
-      Map((register._1, liftVal(register._2)))
+      liftRegVals(registers)
     )
   }
 }
diff --git a/playground-env/src/main/scala/org/ergoplatform/playgroundenv/dsl/TypesDsl.scala b/playground-env/src/main/scala/org/ergoplatform/playgroundenv/dsl/TypesDsl.scala
index 3d05aab..b7182d4 100644
--- a/playground-env/src/main/scala/org/ergoplatform/playgroundenv/dsl/TypesDsl.scala
+++ b/playground-env/src/main/scala/org/ergoplatform/playgroundenv/dsl/TypesDsl.scala
@@ -1,7 +1,11 @@
 package org.ergoplatform.playgroundenv.dsl
 
+import sigmastate.eval.CompiletimeIRContext
+
 trait TypesDsl {
 
+  implicit protected def IR: CompiletimeIRContext;
+
   type Coll[A]              = special.collection.Coll[A]
   type SigmaProp            = special.sigma.SigmaProp
   type ErgoContract         = org.ergoplatform.compiler.ErgoContract
diff --git a/playground-env/src/main/scala/org/ergoplatform/playgroundenv/utils/ErgoScriptCompiler.scala b/playground-env/src/main/scala/org/ergoplatform/playgroundenv/utils/ErgoScriptCompiler.scala
deleted file mode 100644
index b539cca..0000000
--- a/playground-env/src/main/scala/org/ergoplatform/playgroundenv/utils/ErgoScriptCompiler.scala
+++ /dev/null
@@ -1,27 +0,0 @@
-package org.ergoplatform.playgroundenv.utils
-
-import org.ergoplatform.compiler.ErgoContract
-import sigmastate.interpreter.Interpreter.ScriptEnv
-import sigmastate.lang.{SigmaCompiler, TransformingSigmaBuilder}
-import org.ergoplatform.ErgoAddressEncoder.TestnetNetworkPrefix
-import sigmastate.eval.CompiletimeIRContext
-import sigmastate.eval.Evaluation
-import sigmastate.SType
-import sigmastate.SType.AnyOps
-
-object ErgoScriptCompiler {
-
-  val compiler = SigmaCompiler(TestnetNetworkPrefix, TransformingSigmaBuilder)
-
-  implicit var IR: CompiletimeIRContext = new CompiletimeIRContext()
-
-  def compile(env: ScriptEnv, ergoScript: String): ErgoContract = {
-    val liftedEnv = env.mapValues { v =>
-      val tV      = Evaluation.rtypeOf(v).get
-      val elemTpe = Evaluation.rtypeToSType(tV)
-      IR.builder.mkConstant[SType](v.asWrappedType, elemTpe)
-    }
-    val prop = compiler.compile(liftedEnv, ergoScript)
-    ErgoContract(_ => ???, prop)
-  }
-}
diff --git a/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/AssetsAtomicExchangePlayground.scala b/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/AssetsAtomicExchangePlayground.scala
index 317fa1d..197a345 100644
--- a/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/AssetsAtomicExchangePlayground.scala
+++ b/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/AssetsAtomicExchangePlayground.scala
@@ -138,16 +138,16 @@ object AssetsAtomicExchangePlayground {
 
     val sellerOutBox =
       Box(
-        value    = sellerAskNanoErgs,
-        register = (R4 -> sellOrderTransactionSigned.outputs(0).id),
-        script   = contract(sellerParty.wallet.getAddress.pubKey)
+        value     = sellerAskNanoErgs,
+        registers = (R4 -> sellOrderTransactionSigned.outputs(0).id),
+        script    = contract(sellerParty.wallet.getAddress.pubKey)
       )
 
     val buyerOutBox = Box(
-      value    = buyerSwapBoxValue,
-      token    = (token -> buyerBidTokenAmount),
-      register = (R4 -> buyOrderTransactionSigned.outputs(0).id),
-      script   = contract(buyerParty.wallet.getAddress.pubKey)
+      value     = buyerSwapBoxValue,
+      token     = (token -> buyerBidTokenAmount),
+      registers = (R4 -> buyOrderTransactionSigned.outputs(0).id),
+      script    = contract(buyerParty.wallet.getAddress.pubKey)
     )
 
     val dexParty = blockchainSim.newParty("DEX")
diff --git a/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala b/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
index 71b07bb..eb75aaf 100644
--- a/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
+++ b/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
@@ -2,7 +2,6 @@ package org.ergoplatform.playgrounds.examples
 
 object DEXPlayground {
   import org.ergoplatform.compiler.ErgoScalaCompiler._
-  import org.ergoplatform.playgroundenv.utils.ErgoScriptCompiler
   import org.ergoplatform.playground._
 
   def buyerContract(
@@ -22,6 +21,26 @@ object DEXPlayground {
       val tokenPrice = $tokenPrice
       val dexFeePerToken = $dexFeePerToken
 
+      // TODO: use flatmap?
+      val spendingSellOrders = INPUTS.filter { (b: Box) => 
+        b.R4[Coll[Byte]].isDefined && b.R5[Long].isDefined && {
+          val sellOrderTokenId = b.R4[Coll[Byte]].get
+          sellOrderTokenId == tokenId && {
+            b.tokens.size == 1 && b.tokens(0)._1 == tokenId
+          }
+        }
+      }
+
+      val spendingSellOrderTokenInfo = spendingSellOrders.map { (b: Box) => 
+        (b.tokens(0)._2, b.R5[Long].get)
+      }
+
+      // TODO: only part of it is matched
+      // TODO: sort by price
+      val totalSpendingSellOrdersValue = spendingSellOrderTokenInfo.fold(0L, { (acc: Long, t: (Long, Long)) =>  
+        acc + (t._1 * t._2)
+      })
+
       val returnBox = OUTPUTS.filter { (b: Box) => 
         b.R4[Coll[Byte]].isDefined && b.R4[Coll[Byte]].get == SELF.id && b.propositionBytes == buyerPk.propBytes
       }(0)
@@ -30,7 +49,7 @@ object DEXPlayground {
       val returnTokenId = returnTokenData._1
       val returnTokenAmount = returnTokenData._2
       val maxReturnTokenErgValue = returnTokenAmount * tokenPrice
-      val totalReturnErgValue = maxReturnTokenErgValue + returnBox.value
+      val totalReturnErgValueEq = maxReturnTokenErgValue + returnBox.value
       val expectedDexFee = dexFeePerToken * returnTokenAmount
       
       val foundNewOrderBoxes = OUTPUTS.filter { (b: Box) => 
@@ -38,20 +57,23 @@ object DEXPlayground {
       }
 
       val coinsSecured = (SELF.value - expectedDexFee) == maxReturnTokenErgValue || {
-        foundNewOrderBoxes.size == 1 && foundNewOrderBoxes(0).value >= (SELF.value - totalReturnErgValue - expectedDexFee)
+        foundNewOrderBoxes.size == 1 && foundNewOrderBoxes(0).value >= (SELF.value - totalReturnErgValueEq - expectedDexFee)
       }
 
+      val bestPriceDelta = maxReturnTokenErgValue - totalSpendingSellOrdersValue
+
       val tokenIdIsCorrect = returnTokenId == tokenId
     
       allOf(Coll(
           tokenIdIsCorrect,
           returnTokenAmount >= 1,
-          coinsSecured
+          coinsSecured,
+          returnBox.value >= bestPriceDelta
       ))
     }
       """.stripMargin
 
-    ErgoScriptCompiler.compile(buyerContractEnv, buyerScript)
+    contract(buyerContractEnv, buyerScript)
   }
 
   def sellerOrderContract(
@@ -98,7 +120,7 @@ object DEXPlayground {
 
       }""".stripMargin
 
-    ErgoScriptCompiler.compile(sellerContractEnv, sellerScript)
+    contract(sellerContractEnv, sellerScript)
   }
 
   def swapScenario = {
@@ -169,9 +191,11 @@ object DEXPlayground {
     )
 
     val sellOrderBox = Box(
-      value  = sellerDexFee,
-      token  = (token -> sellerAskTokenAmount),
-      script = sellOrderContract
+      value     = sellerDexFee,
+      token     = (token -> sellerAskTokenAmount),
+      script    = sellOrderContract,
+      registers = R4 -> token.tokenId,
+      R5 -> sellerAskTokenPrice
     )
 
     val sellerBalanceBoxes = sellerParty.selectUnspentBoxes(
@@ -193,28 +217,28 @@ object DEXPlayground {
     val sellerTokenAmountSold       = sellerAskTokenAmount / 2
     val sellerDexFeeForPartialMatch = sellerDexFeePerToken * sellerTokenAmountSold
     val sellerOutBoxPartialMatch = Box(
-      value    = sellerTokenAmountSold * sellerAskTokenPrice,
-      register = (R4 -> sellOrderTxSigned.outputs(0).id),
-      script   = contract(sellerParty.wallet.getAddress.pubKey)
+      value     = sellerTokenAmountSold * sellerAskTokenPrice,
+      registers = (R4 -> sellOrderTxSigned.outputs(0).id),
+      script    = contract(sellerParty.wallet.getAddress.pubKey)
     )
 
     // reuse old contract, nothing is changed
     val newSellOrderContract = sellOrderContract
 
     val newSellOrderBox = Box(
-      value    = sellOrderBox.value - sellerDexFeeForPartialMatch,
-      token    = (token -> (sellerAskTokenAmount - sellerTokenAmountSold)),
-      register = (R4 -> sellOrderTxSigned.outputs(0).id),
-      script   = newSellOrderContract
+      value     = sellOrderBox.value - sellerDexFeeForPartialMatch,
+      token     = (token -> (sellerAskTokenAmount - sellerTokenAmountSold)),
+      registers = (R4 -> sellOrderTxSigned.outputs(0).id),
+      script    = newSellOrderContract
     )
 
     val buyerTokenAmountBought     = buyerBidTokenAmount / 2
     val buyerDexFeeForPartialMatch = buyerDexFeePerToken * buyerTokenAmountBought
     val buyerOutBoxPartialMatch = Box(
-      value    = buyerSwapBoxValue,
-      token    = (token -> buyerTokenAmountBought),
-      register = (R4 -> buyOrderTxSigned.outputs(0).id),
-      script   = contract(buyerParty.wallet.getAddress.pubKey)
+      value     = buyerSwapBoxValue,
+      token     = (token -> buyerTokenAmountBought),
+      registers = (R4 -> buyOrderTxSigned.outputs(0).id),
+      script    = contract(buyerParty.wallet.getAddress.pubKey)
     )
 
     // reuse old contract, nothing is changed
@@ -222,9 +246,9 @@ object DEXPlayground {
 
     val newBuyOrderBoxValue = buyOrderBox.value - buyerTokenAmountBought * buyersBidTokenPrice - buyerDexFeeForPartialMatch
     val newBuyOrderBox = Box(
-      value    = newBuyOrderBoxValue,
-      register = (R4 -> buyOrderTxSigned.outputs(0).id),
-      script   = newBuyOrderContract
+      value     = newBuyOrderBoxValue,
+      registers = (R4 -> buyOrderTxSigned.outputs(0).id),
+      script    = newBuyOrderContract
     )
 
     val dexParty = blockchainSim.newParty("DEX")
@@ -268,18 +292,18 @@ object DEXPlayground {
       sellOrderAfterPartialMatching.additionalTokens(0)._2
     val sellerDexFeeForTotalMatching = sellerDexFeePerToken * sellerTokenAmountSoldInTotalMatching
     val sellerOutBoxForTotalMatching = Box(
-      value    = sellerTokenAmountSoldInTotalMatching * sellerAskTokenPrice,
-      register = (R4 -> sellOrderAfterPartialMatching.id),
-      script   = contract(sellerParty.wallet.getAddress.pubKey)
+      value     = sellerTokenAmountSoldInTotalMatching * sellerAskTokenPrice,
+      registers = (R4 -> sellOrderAfterPartialMatching.id),
+      script    = contract(sellerParty.wallet.getAddress.pubKey)
     )
 
     val buyerTokenAmountBoughtInTotalMatching = sellerTokenAmountSoldInTotalMatching
     val buyerDexFeeForTotalMatching           = buyerDexFeePerToken * buyerTokenAmountBoughtInTotalMatching
     val buyerOutBoxForTotalMatching = Box(
-      value    = buyerSwapBoxValue,
-      token    = (token -> buyerTokenAmountBoughtInTotalMatching),
-      register = (R4 -> buyOrderAfterPartialMatching.id),
-      script   = contract(buyerParty.wallet.getAddress.pubKey)
+      value     = buyerSwapBoxValue,
+      token     = (token -> buyerTokenAmountBoughtInTotalMatching),
+      registers = (R4 -> buyOrderAfterPartialMatching.id),
+      script    = contract(buyerParty.wallet.getAddress.pubKey)
     )
 
     val swapTxFeeForTotalMatching = MinTxFee
@@ -364,8 +388,8 @@ object DEXPlayground {
       // as a workaround for https://github.com/ScorexFoundation/sigmastate-interpreter/issues/628
       token = (blockchainSim.newToken("DEXCNCL") -> 1L),
       // as a workaround for https://github.com/ScorexFoundation/sigmastate-interpreter/issues/628
-      register = (R4 -> buyOrderTxSigned.outputs(0).id),
-      script   = contract(buyerParty.wallet.getAddress.pubKey)
+      registers = (R4 -> buyOrderTxSigned.outputs(0).id),
+      script    = contract(buyerParty.wallet.getAddress.pubKey)
     )
 
     val cancelBuyTransaction = Transaction(
@@ -436,8 +460,8 @@ object DEXPlayground {
       value = sellOrderBox.value - cancelTxFee,
       token = (token -> sellerAskTokenAmount),
       // as a workaround for https://github.com/ScorexFoundation/sigmastate-interpreter/issues/628
-      register = (R4 -> sellOrderTxSigned.outputs(0).id),
-      script   = contract(sellerParty.wallet.getAddress.pubKey)
+      registers = (R4 -> sellOrderTxSigned.outputs(0).id),
+      script    = contract(sellerParty.wallet.getAddress.pubKey)
     )
 
     val cancelSellTransaction = Transaction(

From 0aa01a1fe6fb392178a3094fe233ae5abfdfb2f2 Mon Sep 17 00:00:00 2001
From: Denys Zadorozhnyi <denys@zadorozhnyi.com>
Date: Sun, 3 May 2020 13:30:49 +0300
Subject: [PATCH 02/23] move replication check (SELF.id) to R6;

---
 .../ergoplatform/playgrounds/examples/DEXPlayground.scala | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala b/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
index eb75aaf..395131c 100644
--- a/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
+++ b/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
@@ -99,7 +99,7 @@ object DEXPlayground {
       }(0)
       
       val foundNewOrderBoxes = OUTPUTS.filter { (b: Box) => 
-        b.R4[Coll[Byte]].isDefined && b.R4[Coll[Byte]].get == SELF.id && b.propositionBytes == SELF.propositionBytes
+        b.R6[Coll[Byte]].isDefined && b.R6[Coll[Byte]].get == SELF.id && b.propositionBytes == SELF.propositionBytes
       }
 
       (returnBox.value == selfTokenAmount * tokenPrice) || {
@@ -228,8 +228,10 @@ object DEXPlayground {
     val newSellOrderBox = Box(
       value     = sellOrderBox.value - sellerDexFeeForPartialMatch,
       token     = (token -> (sellerAskTokenAmount - sellerTokenAmountSold)),
-      registers = (R4 -> sellOrderTxSigned.outputs(0).id),
-      script    = newSellOrderContract
+      script    = newSellOrderContract,
+      registers = R4 -> token.tokenId,
+      R5 -> sellerAskTokenPrice,
+      R6 -> sellOrderTxSigned.outputs(0).id
     )
 
     val buyerTokenAmountBought     = buyerBidTokenAmount / 2

From b55547076a95f410e61011513c94bf639f46d787 Mon Sep 17 00:00:00 2001
From: Denys Zadorozhnyi <denys@zadorozhnyi.com>
Date: Sun, 3 May 2020 13:46:11 +0300
Subject: [PATCH 03/23] finish buyer contract with single spending sell order;

---
 .../playgrounds/examples/DEXPlayground.scala  | 31 ++++++++++---------
 1 file changed, 17 insertions(+), 14 deletions(-)

diff --git a/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala b/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
index 395131c..41207d8 100644
--- a/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
+++ b/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
@@ -21,7 +21,6 @@ object DEXPlayground {
       val tokenPrice = $tokenPrice
       val dexFeePerToken = $dexFeePerToken
 
-      // TODO: use flatmap?
       val spendingSellOrders = INPUTS.filter { (b: Box) => 
         b.R4[Coll[Byte]].isDefined && b.R5[Long].isDefined && {
           val sellOrderTokenId = b.R4[Coll[Byte]].get
@@ -31,15 +30,14 @@ object DEXPlayground {
         }
       }
 
-      val spendingSellOrderTokenInfo = spendingSellOrders.map { (b: Box) => 
-        (b.tokens(0)._2, b.R5[Long].get)
-      }
-
       // TODO: only part of it is matched
-      // TODO: sort by price
-      val totalSpendingSellOrdersValue = spendingSellOrderTokenInfo.fold(0L, { (acc: Long, t: (Long, Long)) =>  
-        acc + (t._1 * t._2)
-      })
+      // TODO: for multiplse sell orders sort by price
+      // val spendingSellOrderTokenInfo = spendingSellOrders.map { (b: Box) => 
+      //   (b.tokens(0)._2, b.R5[Long].get)
+      // }
+      // val totalSpendingSellOrdersValue = spendingSellOrderTokenInfo.fold(0L, { (acc: Long, t: (Long, Long)) =>  
+      //   acc + (t._1 * t._2)
+      // })
 
       val returnBox = OUTPUTS.filter { (b: Box) => 
         b.R4[Coll[Byte]].isDefined && b.R4[Coll[Byte]].get == SELF.id && b.propositionBytes == buyerPk.propBytes
@@ -60,7 +58,12 @@ object DEXPlayground {
         foundNewOrderBoxes.size == 1 && foundNewOrderBoxes(0).value >= (SELF.value - totalReturnErgValueEq - expectedDexFee)
       }
 
-      val bestPriceDelta = maxReturnTokenErgValue - totalSpendingSellOrdersValue
+      // TODO: test it cannot be stolen on partial and total matching 
+      // fixed spending sell orders to 1
+      val bestPriceDeltaReturned = spendingSellOrders.size == 1 && { 
+        val spendingSellOrdersValue = spendingSellOrders(0).R5[Long].get * returnTokenAmount
+        returnBox.value >= maxReturnTokenErgValue - spendingSellOrdersValue
+      }
 
       val tokenIdIsCorrect = returnTokenId == tokenId
     
@@ -68,7 +71,7 @@ object DEXPlayground {
           tokenIdIsCorrect,
           returnTokenAmount >= 1,
           coinsSecured,
-          returnBox.value >= bestPriceDelta
+          bestPriceDeltaReturned
       ))
     }
       """.stripMargin
@@ -146,7 +149,7 @@ object DEXPlayground {
       )
 
     val sellerParty          = blockchainSim.newParty("seller")
-    val sellerAskTokenPrice  = 5000000L
+    val sellerAskTokenPrice  = 4000000L
     val sellerAskTokenAmount = 100L
     val sellerAskNanoErgs    = sellerAskTokenPrice * sellerAskTokenAmount
     val sellerDexFee         = 10000000L
@@ -237,7 +240,7 @@ object DEXPlayground {
     val buyerTokenAmountBought     = buyerBidTokenAmount / 2
     val buyerDexFeeForPartialMatch = buyerDexFeePerToken * buyerTokenAmountBought
     val buyerOutBoxPartialMatch = Box(
-      value     = buyerSwapBoxValue,
+      value     = buyerSwapBoxValue + (buyersBidTokenPrice - sellerAskTokenPrice) * buyerTokenAmountBought,
       token     = (token -> buyerTokenAmountBought),
       registers = (R4 -> buyOrderTxSigned.outputs(0).id),
       script    = contract(buyerParty.wallet.getAddress.pubKey)
@@ -302,7 +305,7 @@ object DEXPlayground {
     val buyerTokenAmountBoughtInTotalMatching = sellerTokenAmountSoldInTotalMatching
     val buyerDexFeeForTotalMatching           = buyerDexFeePerToken * buyerTokenAmountBoughtInTotalMatching
     val buyerOutBoxForTotalMatching = Box(
-      value     = buyerSwapBoxValue,
+      value     = buyerSwapBoxValue + (buyersBidTokenPrice - sellerAskTokenPrice) * buyerTokenAmountBoughtInTotalMatching,
       token     = (token -> buyerTokenAmountBoughtInTotalMatching),
       registers = (R4 -> buyOrderAfterPartialMatching.id),
       script    = contract(buyerParty.wallet.getAddress.pubKey)

From 2343110c198f0e8580d0876e4189394e955b78ea Mon Sep 17 00:00:00 2001
From: Denys Zadorozhnyi <denys@zadorozhnyi.com>
Date: Tue, 5 May 2020 17:03:31 +0300
Subject: [PATCH 04/23] draft buy order;

---
 .../playgrounds/examples/DEXPlayground.scala  | 41 +++++++++++++------
 1 file changed, 28 insertions(+), 13 deletions(-)

diff --git a/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala b/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
index 41207d8..3aa07cc 100644
--- a/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
+++ b/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
@@ -46,32 +46,37 @@ object DEXPlayground {
       val returnTokenData = returnBox.tokens(0)
       val returnTokenId = returnTokenData._1
       val returnTokenAmount = returnTokenData._2
-      val maxReturnTokenErgValue = returnTokenAmount * tokenPrice
-      val totalReturnErgValueEq = maxReturnTokenErgValue + returnBox.value
       val expectedDexFee = dexFeePerToken * returnTokenAmount
       
       val foundNewOrderBoxes = OUTPUTS.filter { (b: Box) => 
-        b.R4[Coll[Byte]].isDefined && b.R4[Coll[Byte]].get == SELF.id && b.propositionBytes == SELF.propositionBytes
+        b.R6[Coll[Byte]].isDefined && b.R6[Coll[Byte]].get == SELF.id && b.propositionBytes == SELF.propositionBytes
       }
 
-      val coinsSecured = (SELF.value - expectedDexFee) == maxReturnTokenErgValue || {
-        foundNewOrderBoxes.size == 1 && foundNewOrderBoxes(0).value >= (SELF.value - totalReturnErgValueEq - expectedDexFee)
+      val sellOrder = spendingSellOrders(0)
+      val sellOrderTokenPrice = sellOrder.R5[Long].get
+      // TODO: if both orders were in the same block who gets the spread?
+      val spreadPerToken = if (sellOrder.creationInfo._1 >=SELF.creationInfo._1) 
+        tokenPrice - sellOrderTokenPrice
+      else 
+        0L
+
+      val totalMatching = (SELF.value - expectedDexFee) == returnTokenAmount * tokenPrice && 
+        returnBox.value >=returnTokenAmount * spreadPerToken
+      val partialMatching = {
+        foundNewOrderBoxes.size == 1 && 
+          foundNewOrderBoxes(0).value == (SELF.value - returnTokenAmount * tokenPrice - expectedDexFee) &&
+          returnBox.value >=returnTokenAmount * spreadPerToken
       }
 
-      // TODO: test it cannot be stolen on partial and total matching 
-      // fixed spending sell orders to 1
-      val bestPriceDeltaReturned = spendingSellOrders.size == 1 && { 
-        val spendingSellOrdersValue = spendingSellOrders(0).R5[Long].get * returnTokenAmount
-        returnBox.value >= maxReturnTokenErgValue - spendingSellOrdersValue
-      }
+      val coinsSecured = partialMatching ||totalMatching
 
       val tokenIdIsCorrect = returnTokenId == tokenId
     
       allOf(Coll(
           tokenIdIsCorrect,
           returnTokenAmount >= 1,
-          coinsSecured,
-          bestPriceDeltaReturned
+          sellOrderTokenPrice <=tokenPrice,
+          coinsSecured
       ))
     }
       """.stripMargin
@@ -101,9 +106,19 @@ object DEXPlayground {
         b.R4[Coll[Byte]].isDefined && b.R4[Coll[Byte]].get == SELF.id && b.propositionBytes == sellerPk.propBytes
       }(0)
       
+      val spendingBuyOrders = INPUTS.filter { (b: Box) => 
+        b.R4[Coll[Byte]].isDefined && b.R5[Long].isDefined && {
+          val buyOrderTokenId = b.R4[Coll[Byte]].get
+          buyOrderTokenId == tokenId && {
+            b.tokens.size == 1 && b.tokens(0)._1 == tokenId
+          }
+        }
+      }
+
       val foundNewOrderBoxes = OUTPUTS.filter { (b: Box) => 
         b.R6[Coll[Byte]].isDefined && b.R6[Coll[Byte]].get == SELF.id && b.propositionBytes == SELF.propositionBytes
       }
+      // TODO: require spread only if we were earlier
 
       (returnBox.value == selfTokenAmount * tokenPrice) || {
         foundNewOrderBoxes.size == 1 && {

From 0fc52d139093fb29f5a24ef804e769aff7472220 Mon Sep 17 00:00:00 2001
From: Denys Zadorozhnyi <denys@zadorozhnyi.com>
Date: Tue, 5 May 2020 17:53:06 +0300
Subject: [PATCH 05/23] draft sell order contract;

---
 .../playgrounds/examples/DEXPlayground.scala  | 24 +++++++++++++++----
 1 file changed, 20 insertions(+), 4 deletions(-)

diff --git a/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala b/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
index 3aa07cc..3c91789 100644
--- a/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
+++ b/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
@@ -49,6 +49,7 @@ object DEXPlayground {
       val expectedDexFee = dexFeePerToken * returnTokenAmount
       
       val foundNewOrderBoxes = OUTPUTS.filter { (b: Box) => 
+        val contractParametersAreCorrect = b.R4[Coll[Byte]].get == tokenId && b.R5[Long].get == tokenPrice
         b.R6[Coll[Byte]].isDefined && b.R6[Coll[Byte]].get == SELF.id && b.propositionBytes == SELF.propositionBytes
       }
 
@@ -115,12 +116,23 @@ object DEXPlayground {
         }
       }
 
+      val buyOrder = spendingBuyOrders(0)
+
       val foundNewOrderBoxes = OUTPUTS.filter { (b: Box) => 
-        b.R6[Coll[Byte]].isDefined && b.R6[Coll[Byte]].get == SELF.id && b.propositionBytes == SELF.propositionBytes
+        val contractParametersAreCorrect = b.R4[Coll[Byte]].get == tokenId && b.R5[Long].get == tokenPrice
+        val contractIsTheSame = b.propositionBytes == SELF.propositionBytes
+        b.R6[Coll[Byte]].isDefined && b.R6[Coll[Byte]].get == SELF.id && contractIsTheSame
       }
-      // TODO: require spread only if we were earlier
 
-      (returnBox.value == selfTokenAmount * tokenPrice) || {
+      val buyOrderTokenPrice = buyOrder.R5[Long].get
+      val spreadPerToken = if (buyOrder.creationInfo._1 > SELF.creationInfo._1) 
+         buyOrderTokenPrice - tokenPrice
+      else 
+        0L
+
+      val totalMatching = (returnBox.value == selfTokenAmount * (tokenPrice + spreadPerToken)) 
+
+      val partialMatching = {
         foundNewOrderBoxes.size == 1 && {
           val newOrderBox = foundNewOrderBoxes(0)
           val newOrderTokenData = newOrderBox.tokens(0)
@@ -132,10 +144,14 @@ object DEXPlayground {
           val newOrderTokenId = newOrderTokenData._1
           val tokenIdIsCorrect = newOrderTokenId == tokenId
 
-          tokenIdIsCorrect && soldTokenAmount >= 1 && newOrderBox.value >= (SELF.value - minSoldTokenErgValue - expectedDexFee)
+          val newOrderValueIsCorrect = newOrderBox.value == (SELF.value - expectedDexFee)
+          val returnBoxValueIsCorrect = returnBox.value == soldTokenAmount * (tokenPrice + spreadPerToken)
+          tokenIdIsCorrect && soldTokenAmount >= 1 && newOrderValueIsCorrect && returnBoxValueIsCorrect
         }
       }
 
+      (totalMatching ||partialMatching) && buyOrderTokenPrice >=tokenPrice
+
       }""".stripMargin
 
     contract(sellerContractEnv, sellerScript)

From aebab81a0cb3975583973acdb2f31fc77e600ea0 Mon Sep 17 00:00:00 2001
From: Denys Zadorozhnyi <denys@zadorozhnyi.com>
Date: Tue, 5 May 2020 18:15:34 +0300
Subject: [PATCH 06/23] add contract parameters in registers for order boxes;

---
 .../playgrounds/examples/DEXPlayground.scala        | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala b/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
index 3c91789..8db532b 100644
--- a/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
+++ b/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
@@ -204,7 +204,12 @@ object DEXPlayground {
       )
 
     val buyOrderBoxValue = buyersBidTokenPrice * buyerBidTokenAmount + buyerDexFee
-    val buyOrderBox      = Box(value = buyOrderBoxValue, script = buyOrderContract)
+    val buyOrderBox = Box(
+      value     = buyOrderBoxValue,
+      script    = buyOrderContract,
+      registers = R4 -> token.tokenId,
+      R5 -> buyersBidTokenPrice
+    )
 
     val buyOrderTransaction = Transaction(
       inputs       = buyerParty.selectUnspentBoxes(toSpend = buyOrderBoxValue + buyOrderTxFee),
@@ -283,8 +288,10 @@ object DEXPlayground {
     val newBuyOrderBoxValue = buyOrderBox.value - buyerTokenAmountBought * buyersBidTokenPrice - buyerDexFeeForPartialMatch
     val newBuyOrderBox = Box(
       value     = newBuyOrderBoxValue,
-      registers = (R4 -> buyOrderTxSigned.outputs(0).id),
-      script    = newBuyOrderContract
+      script    = newBuyOrderContract,
+      registers = R4 -> token.tokenId,
+      R5 -> sellerAskTokenPrice,
+      R6 -> buyOrderTxSigned.outputs(0).id
     )
 
     val dexParty = blockchainSim.newParty("DEX")

From de3d69de70a7fd45dbd70019fa99e5fb899c31a0 Mon Sep 17 00:00:00 2001
From: Denys Zadorozhnyi <denys@zadorozhnyi.com>
Date: Wed, 6 May 2020 16:51:30 +0300
Subject: [PATCH 07/23] guarded counter order presence in buyer contract; added
 regs to boxes in both cancel scenarios;

---
 .../playgrounds/examples/DEXPlayground.scala  | 35 ++++++++++++-------
 1 file changed, 23 insertions(+), 12 deletions(-)

diff --git a/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala b/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
index 8db532b..a887c7a 100644
--- a/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
+++ b/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
@@ -53,13 +53,18 @@ object DEXPlayground {
         b.R6[Coll[Byte]].isDefined && b.R6[Coll[Byte]].get == SELF.id && b.propositionBytes == SELF.propositionBytes
       }
 
-      val sellOrder = spendingSellOrders(0)
-      val sellOrderTokenPrice = sellOrder.R5[Long].get
-      // TODO: if both orders were in the same block who gets the spread?
-      val spreadPerToken = if (sellOrder.creationInfo._1 >=SELF.creationInfo._1) 
-        tokenPrice - sellOrderTokenPrice
-      else 
-        0L
+      val spreadPerToken =  {
+        if (spendingSellOrders.size == 1) {        
+          val sellOrder = spendingSellOrders(0)
+          val sellOrderTokenPrice = sellOrder.R5[Long].get
+          // TODO: if both orders were in the same block who gets the spread?
+          if (sellOrder.creationInfo._1 >=SELF.creationInfo._1 && sellOrderTokenPrice <=tokenPrice) 
+            tokenPrice - sellOrderTokenPrice
+          else 
+            0L
+        } else 
+          0L
+      }
 
       val totalMatching = (SELF.value - expectedDexFee) == returnTokenAmount * tokenPrice && 
         returnBox.value >=returnTokenAmount * spreadPerToken
@@ -76,7 +81,6 @@ object DEXPlayground {
       allOf(Coll(
           tokenIdIsCorrect,
           returnTokenAmount >= 1,
-          sellOrderTokenPrice <=tokenPrice,
           coinsSecured
       ))
     }
@@ -409,7 +413,12 @@ object DEXPlayground {
       )
 
     val buyOrderBoxValue = buyersBidTokenPrice * buyerBidTokenAmount + buyerDexFee
-    val buyOrderBox      = Box(value = buyOrderBoxValue, script = buyOrderContract)
+    val buyOrderBox = Box(
+      value     = buyOrderBoxValue,
+      script    = buyOrderContract,
+      registers = R4 -> token.tokenId,
+      R5 -> buyersBidTokenPrice
+    )
 
     val buyOrderTransaction = Transaction(
       inputs       = buyerParty.selectUnspentBoxes(toSpend = buyOrderBoxValue + buyOrderTxFee),
@@ -476,9 +485,11 @@ object DEXPlayground {
     )
 
     val sellOrderBox = Box(
-      value  = sellerDexFee,
-      token  = (token -> sellerAskTokenAmount),
-      script = sellOrderContract
+      value     = sellerDexFee,
+      token     = (token -> sellerAskTokenAmount),
+      script    = sellOrderContract,
+      registers = R4 -> token.tokenId,
+      R5 -> sellerAskTokenPrice
     )
 
     val sellerBalanceBoxes = sellerParty.selectUnspentBoxes(

From 9f9835cbd70ce1df91edf4b7b4fd49dd2fa14f05 Mon Sep 17 00:00:00 2001
From: Denys Zadorozhnyi <denys@zadorozhnyi.com>
Date: Thu, 7 May 2020 09:16:54 +0300
Subject: [PATCH 08/23] comments;

---
 .../org/ergoplatform/playgrounds/examples/DEXPlayground.scala   | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala b/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
index a887c7a..8b5e190 100644
--- a/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
+++ b/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
@@ -30,6 +30,8 @@ object DEXPlayground {
         }
       }
 
+      // TODO: check that counter orders are sorted by token price
+
       // TODO: only part of it is matched
       // TODO: for multiplse sell orders sort by price
       // val spendingSellOrderTokenInfo = spendingSellOrders.map { (b: Box) => 

From 845bda8f1cfbfc25762d8fc899a59169358115bf Mon Sep 17 00:00:00 2001
From: Denys Zadorozhnyi <denys@zadorozhnyi.com>
Date: Thu, 7 May 2020 09:39:35 +0300
Subject: [PATCH 09/23] get the token id from return box via getOrElse in buyer
 contract and avoid fake token minting on buy order cancel

---
 .../playgrounds/examples/DEXPlayground.scala          | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala b/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
index a887c7a..949584a 100644
--- a/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
+++ b/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
@@ -43,9 +43,8 @@ object DEXPlayground {
         b.R4[Coll[Byte]].isDefined && b.R4[Coll[Byte]].get == SELF.id && b.propositionBytes == buyerPk.propBytes
       }(0)
 
-      val returnTokenData = returnBox.tokens(0)
-      val returnTokenId = returnTokenData._1
-      val returnTokenAmount = returnTokenData._2
+      val returnTokenAmount = if (returnBox.tokens.size == 1) returnBox.tokens(0)._2 else 0L
+      
       val expectedDexFee = dexFeePerToken * returnTokenAmount
       
       val foundNewOrderBoxes = OUTPUTS.filter { (b: Box) => 
@@ -76,8 +75,8 @@ object DEXPlayground {
 
       val coinsSecured = partialMatching ||totalMatching
 
-      val tokenIdIsCorrect = returnTokenId == tokenId
-    
+      val tokenIdIsCorrect = returnBox.tokens.getOrElse(0, (Coll[Byte](), 0L))._1 == tokenId
+      
       allOf(Coll(
           tokenIdIsCorrect,
           returnTokenAmount >= 1,
@@ -438,8 +437,6 @@ object DEXPlayground {
     val buyerReturnBox = Box(
       value = buyOrderBox.value - cancelTxFee,
       // as a workaround for https://github.com/ScorexFoundation/sigmastate-interpreter/issues/628
-      token = (blockchainSim.newToken("DEXCNCL") -> 1L),
-      // as a workaround for https://github.com/ScorexFoundation/sigmastate-interpreter/issues/628
       registers = (R4 -> buyOrderTxSigned.outputs(0).id),
       script    = contract(buyerParty.wallet.getAddress.pubKey)
     )

From cefa7b497321afcdc7944bcff19dd07b627200a6 Mon Sep 17 00:00:00 2001
From: Denys Zadorozhnyi <denys@zadorozhnyi.com>
Date: Thu, 7 May 2020 12:17:41 +0300
Subject: [PATCH 10/23] remove R4 in return box on buy order cancellation;

---
 .../playgrounds/examples/DEXPlayground.scala  | 79 ++++++++++---------
 1 file changed, 40 insertions(+), 39 deletions(-)

diff --git a/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala b/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
index 949584a..c49a5ee 100644
--- a/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
+++ b/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
@@ -39,49 +39,52 @@ object DEXPlayground {
       //   acc + (t._1 * t._2)
       // })
 
-      val returnBox = OUTPUTS.filter { (b: Box) => 
+      val returnBoxes = OUTPUTS.filter { (b: Box) => 
         b.R4[Coll[Byte]].isDefined && b.R4[Coll[Byte]].get == SELF.id && b.propositionBytes == buyerPk.propBytes
-      }(0)
-
-      val returnTokenAmount = if (returnBox.tokens.size == 1) returnBox.tokens(0)._2 else 0L
-      
-      val expectedDexFee = dexFeePerToken * returnTokenAmount
-      
-      val foundNewOrderBoxes = OUTPUTS.filter { (b: Box) => 
-        val contractParametersAreCorrect = b.R4[Coll[Byte]].get == tokenId && b.R5[Long].get == tokenPrice
-        b.R6[Coll[Byte]].isDefined && b.R6[Coll[Byte]].get == SELF.id && b.propositionBytes == SELF.propositionBytes
       }
 
-      val spreadPerToken =  {
-        if (spendingSellOrders.size == 1) {        
-          val sellOrder = spendingSellOrders(0)
-          val sellOrderTokenPrice = sellOrder.R5[Long].get
-          // TODO: if both orders were in the same block who gets the spread?
-          if (sellOrder.creationInfo._1 >=SELF.creationInfo._1 && sellOrderTokenPrice <=tokenPrice) 
-            tokenPrice - sellOrderTokenPrice
-          else 
+      returnBoxes.size == 1 && {
+        val returnBox = returnBoxes(0)
+        val returnTokenAmount = if (returnBox.tokens.size == 1) returnBox.tokens(0)._2 else 0L
+        
+        val expectedDexFee = dexFeePerToken * returnTokenAmount
+        
+        val foundNewOrderBoxes = OUTPUTS.filter { (b: Box) => 
+          val contractParametersAreCorrect = b.R4[Coll[Byte]].get == tokenId && b.R5[Long].get == tokenPrice
+          b.R6[Coll[Byte]].isDefined && b.R6[Coll[Byte]].get == SELF.id && b.propositionBytes == SELF.propositionBytes
+        }
+
+        val spreadPerToken =  {
+          if (spendingSellOrders.size == 1) {        
+            val sellOrder = spendingSellOrders(0)
+            val sellOrderTokenPrice = sellOrder.R5[Long].get
+            // TODO: if both orders were in the same block who gets the spread?
+            if (sellOrder.creationInfo._1 >=SELF.creationInfo._1 && sellOrderTokenPrice <=tokenPrice) 
+              tokenPrice - sellOrderTokenPrice
+            else 
+              0L
+          } else 
             0L
-        } else 
-          0L
-      }
+        }
 
-      val totalMatching = (SELF.value - expectedDexFee) == returnTokenAmount * tokenPrice && 
-        returnBox.value >=returnTokenAmount * spreadPerToken
-      val partialMatching = {
-        foundNewOrderBoxes.size == 1 && 
-          foundNewOrderBoxes(0).value == (SELF.value - returnTokenAmount * tokenPrice - expectedDexFee) &&
+        val totalMatching = (SELF.value - expectedDexFee) == returnTokenAmount * tokenPrice && 
           returnBox.value >=returnTokenAmount * spreadPerToken
-      }
+        val partialMatching = {
+          foundNewOrderBoxes.size == 1 && 
+            foundNewOrderBoxes(0).value == (SELF.value - returnTokenAmount * tokenPrice - expectedDexFee) &&
+            returnBox.value >=returnTokenAmount * spreadPerToken
+        }
 
-      val coinsSecured = partialMatching ||totalMatching
+        val coinsSecured = partialMatching ||totalMatching
 
-      val tokenIdIsCorrect = returnBox.tokens.getOrElse(0, (Coll[Byte](), 0L))._1 == tokenId
-      
-      allOf(Coll(
-          tokenIdIsCorrect,
-          returnTokenAmount >= 1,
-          coinsSecured
-      ))
+        val tokenIdIsCorrect = returnBox.tokens.getOrElse(0, (Coll[Byte](), 0L))._1 == tokenId
+        
+        allOf(Coll(
+            tokenIdIsCorrect,
+            returnTokenAmount >= 1,
+            coinsSecured
+        ))
+      }
     }
       """.stripMargin
 
@@ -435,10 +438,8 @@ object DEXPlayground {
     val cancelTxFee = MinTxFee
 
     val buyerReturnBox = Box(
-      value = buyOrderBox.value - cancelTxFee,
-      // as a workaround for https://github.com/ScorexFoundation/sigmastate-interpreter/issues/628
-      registers = (R4 -> buyOrderTxSigned.outputs(0).id),
-      script    = contract(buyerParty.wallet.getAddress.pubKey)
+      value  = buyOrderBox.value - cancelTxFee,
+      script = contract(buyerParty.wallet.getAddress.pubKey)
     )
 
     val cancelBuyTransaction = Transaction(

From d1d11fd0369c3c8e71a33334b3140972adf9f62c Mon Sep 17 00:00:00 2001
From: Denys Zadorozhnyi <denys@zadorozhnyi.com>
Date: Thu, 7 May 2020 12:24:51 +0300
Subject: [PATCH 11/23] remove R4 in sell order cancellation box;

---
 .../playgrounds/examples/DEXPlayground.scala  | 85 ++++++++++---------
 1 file changed, 43 insertions(+), 42 deletions(-)

diff --git a/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala b/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
index c49a5ee..7b98073 100644
--- a/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
+++ b/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
@@ -109,54 +109,57 @@ object DEXPlayground {
 
       val selfTokenAmount = SELF.tokens(0)._2
 
-      val returnBox = OUTPUTS.filter { (b: Box) => 
+      val returnBoxes = OUTPUTS.filter { (b: Box) => 
         b.R4[Coll[Byte]].isDefined && b.R4[Coll[Byte]].get == SELF.id && b.propositionBytes == sellerPk.propBytes
-      }(0)
-      
-      val spendingBuyOrders = INPUTS.filter { (b: Box) => 
-        b.R4[Coll[Byte]].isDefined && b.R5[Long].isDefined && {
-          val buyOrderTokenId = b.R4[Coll[Byte]].get
-          buyOrderTokenId == tokenId && {
-            b.tokens.size == 1 && b.tokens(0)._1 == tokenId
+      }
+
+      returnBoxes.size == 1 && {
+        val returnBox = returnBoxes(0)
+        val spendingBuyOrders = INPUTS.filter { (b: Box) => 
+          b.R4[Coll[Byte]].isDefined && b.R5[Long].isDefined && {
+            val buyOrderTokenId = b.R4[Coll[Byte]].get
+            buyOrderTokenId == tokenId && {
+              b.tokens.size == 1 && b.tokens(0)._1 == tokenId
+            }
           }
         }
-      }
 
-      val buyOrder = spendingBuyOrders(0)
+        val buyOrder = spendingBuyOrders(0)
 
-      val foundNewOrderBoxes = OUTPUTS.filter { (b: Box) => 
-        val contractParametersAreCorrect = b.R4[Coll[Byte]].get == tokenId && b.R5[Long].get == tokenPrice
-        val contractIsTheSame = b.propositionBytes == SELF.propositionBytes
-        b.R6[Coll[Byte]].isDefined && b.R6[Coll[Byte]].get == SELF.id && contractIsTheSame
-      }
+        val foundNewOrderBoxes = OUTPUTS.filter { (b: Box) => 
+          val contractParametersAreCorrect = b.R4[Coll[Byte]].get == tokenId && b.R5[Long].get == tokenPrice
+          val contractIsTheSame = b.propositionBytes == SELF.propositionBytes
+          b.R6[Coll[Byte]].isDefined && b.R6[Coll[Byte]].get == SELF.id && contractIsTheSame
+        }
+
+        val buyOrderTokenPrice = buyOrder.R5[Long].get
+        val spreadPerToken = if (buyOrder.creationInfo._1 > SELF.creationInfo._1) 
+           buyOrderTokenPrice - tokenPrice
+        else 
+          0L
 
-      val buyOrderTokenPrice = buyOrder.R5[Long].get
-      val spreadPerToken = if (buyOrder.creationInfo._1 > SELF.creationInfo._1) 
-         buyOrderTokenPrice - tokenPrice
-      else 
-        0L
-
-      val totalMatching = (returnBox.value == selfTokenAmount * (tokenPrice + spreadPerToken)) 
-
-      val partialMatching = {
-        foundNewOrderBoxes.size == 1 && {
-          val newOrderBox = foundNewOrderBoxes(0)
-          val newOrderTokenData = newOrderBox.tokens(0)
-          val newOrderTokenAmount = newOrderTokenData._2
-          val soldTokenAmount = selfTokenAmount - newOrderTokenAmount
-          val minSoldTokenErgValue = soldTokenAmount * tokenPrice
-          val expectedDexFee = dexFeePerToken * soldTokenAmount
-
-          val newOrderTokenId = newOrderTokenData._1
-          val tokenIdIsCorrect = newOrderTokenId == tokenId
-
-          val newOrderValueIsCorrect = newOrderBox.value == (SELF.value - expectedDexFee)
-          val returnBoxValueIsCorrect = returnBox.value == soldTokenAmount * (tokenPrice + spreadPerToken)
-          tokenIdIsCorrect && soldTokenAmount >= 1 && newOrderValueIsCorrect && returnBoxValueIsCorrect
+        val totalMatching = (returnBox.value == selfTokenAmount * (tokenPrice + spreadPerToken)) 
+
+        val partialMatching = {
+          foundNewOrderBoxes.size == 1 && {
+            val newOrderBox = foundNewOrderBoxes(0)
+            val newOrderTokenData = newOrderBox.tokens(0)
+            val newOrderTokenAmount = newOrderTokenData._2
+            val soldTokenAmount = selfTokenAmount - newOrderTokenAmount
+            val minSoldTokenErgValue = soldTokenAmount * tokenPrice
+            val expectedDexFee = dexFeePerToken * soldTokenAmount
+
+            val newOrderTokenId = newOrderTokenData._1
+            val tokenIdIsCorrect = newOrderTokenId == tokenId
+
+            val newOrderValueIsCorrect = newOrderBox.value == (SELF.value - expectedDexFee)
+            val returnBoxValueIsCorrect = returnBox.value == soldTokenAmount * (tokenPrice + spreadPerToken)
+            tokenIdIsCorrect && soldTokenAmount >= 1 && newOrderValueIsCorrect && returnBoxValueIsCorrect
+          }
         }
-      }
 
-      (totalMatching ||partialMatching) && buyOrderTokenPrice >=tokenPrice
+        (totalMatching ||partialMatching) && buyOrderTokenPrice >=tokenPrice
+      }
 
       }""".stripMargin
 
@@ -511,8 +514,6 @@ object DEXPlayground {
     val sellerReturnBox = Box(
       value = sellOrderBox.value - cancelTxFee,
       token = (token -> sellerAskTokenAmount),
-      // as a workaround for https://github.com/ScorexFoundation/sigmastate-interpreter/issues/628
-      registers = (R4 -> sellOrderTxSigned.outputs(0).id),
       script    = contract(sellerParty.wallet.getAddress.pubKey)
     )
 

From ca88e94a191f38f268c97a01e5bf1051891ce0ee Mon Sep 17 00:00:00 2001
From: Denys Zadorozhnyi <denys@zadorozhnyi.com>
Date: Thu, 7 May 2020 17:22:26 +0300
Subject: [PATCH 12/23] calc full spread instead of spread per token;
 formatting;

---
 .../playgrounds/examples/DEXPlayground.scala     | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala b/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
index f0ed551..cd57194 100644
--- a/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
+++ b/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
@@ -56,13 +56,13 @@ object DEXPlayground {
           b.R6[Coll[Byte]].isDefined && b.R6[Coll[Byte]].get == SELF.id && b.propositionBytes == SELF.propositionBytes
         }
 
-        val spreadPerToken =  {
+        val fullSpread = {
           if (spendingSellOrders.size == 1) {        
             val sellOrder = spendingSellOrders(0)
             val sellOrderTokenPrice = sellOrder.R5[Long].get
             // TODO: if both orders were in the same block who gets the spread?
-            if (sellOrder.creationInfo._1 >=SELF.creationInfo._1 && sellOrderTokenPrice <=tokenPrice) 
-              tokenPrice - sellOrderTokenPrice
+            if (sellOrder.creationInfo._1 >= SELF.creationInfo._1 && sellOrderTokenPrice <= tokenPrice) 
+              (tokenPrice - sellOrderTokenPrice) * returnTokenAmount
             else 
               0L
           } else 
@@ -70,11 +70,11 @@ object DEXPlayground {
         }
 
         val totalMatching = (SELF.value - expectedDexFee) == returnTokenAmount * tokenPrice && 
-          returnBox.value >=returnTokenAmount * spreadPerToken
+          returnBox.value >= fullSpread
         val partialMatching = {
           foundNewOrderBoxes.size == 1 && 
             foundNewOrderBoxes(0).value == (SELF.value - returnTokenAmount * tokenPrice - expectedDexFee) &&
-            returnBox.value >=returnTokenAmount * spreadPerToken
+            returnBox.value >= fullSpread
         }
 
         val coinsSecured = partialMatching ||totalMatching
@@ -514,9 +514,9 @@ object DEXPlayground {
     val cancelTxFee = MinTxFee
 
     val sellerReturnBox = Box(
-      value = sellOrderBox.value - cancelTxFee,
-      token = (token -> sellerAskTokenAmount),
-      script    = contract(sellerParty.wallet.getAddress.pubKey)
+      value  = sellOrderBox.value - cancelTxFee,
+      token  = (token -> sellerAskTokenAmount),
+      script = contract(sellerParty.wallet.getAddress.pubKey)
     )
 
     val cancelSellTransaction = Transaction(

From fd95cc3cdcb98aaea5e30447529c98ad83f1de36 Mon Sep 17 00:00:00 2001
From: Denys Zadorozhnyi <denys@zadorozhnyi.com>
Date: Thu, 7 May 2020 18:06:12 +0300
Subject: [PATCH 13/23] draft buyer contract for multiple counter orders;

---
 .../playgrounds/examples/DEXPlayground.scala  | 49 +++++++++++--------
 1 file changed, 28 insertions(+), 21 deletions(-)

diff --git a/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala b/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
index cd57194..885554d 100644
--- a/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
+++ b/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
@@ -16,6 +16,9 @@ object DEXPlayground {
     val buyerContractEnv: ScriptEnv =
       Map("buyerPk" -> buyerPk, "tokenId" -> token.tokenId)
 
+    // TODO : check that counter orders are sorted by token price
+    // TODO: if both orders were in the same block who gets the spread?
+    // TODO: move price check (from fullSpread) to boxesAreSortedByTokenPrice?
     val buyerScript = s"""buyerPk || {
 
       val tokenPrice = $tokenPrice
@@ -30,22 +33,13 @@ object DEXPlayground {
         }
       }
 
-      // TODO: check that counter orders are sorted by token price
-
-      // TODO: only part of it is matched
-      // TODO: for multiplse sell orders sort by price
-      // val spendingSellOrderTokenInfo = spendingSellOrders.map { (b: Box) => 
-      //   (b.tokens(0)._2, b.R5[Long].get)
-      // }
-      // val totalSpendingSellOrdersValue = spendingSellOrderTokenInfo.fold(0L, { (acc: Long, t: (Long, Long)) =>  
-      //   acc + (t._1 * t._2)
-      // })
-
       val returnBoxes = OUTPUTS.filter { (b: Box) => 
         b.R4[Coll[Byte]].isDefined && b.R4[Coll[Byte]].get == SELF.id && b.propositionBytes == buyerPk.propBytes
       }
 
-      returnBoxes.size == 1 && {
+      val boxesAreSortedByTokenPrice = { (boxes: Coll[Box]) => true }
+
+      returnBoxes.size == 1 && spendingSellOrders.size > 0 && boxesAreSortedByTokenPrice(spendingSellOrders) && {
         val returnBox = returnBoxes(0)
         val returnTokenAmount = if (returnBox.tokens.size == 1) returnBox.tokens(0)._2 else 0L
         
@@ -57,16 +51,29 @@ object DEXPlayground {
         }
 
         val fullSpread = {
-          if (spendingSellOrders.size == 1) {        
-            val sellOrder = spendingSellOrders(0)
+          spendingSellOrders.fold((returnTokenAmount, 0L), { (t: (Long, Long), sellOrder: Box) => 
+            val returnTokensLeft = t._1
+            val accumulatedFullSpread = t._2
             val sellOrderTokenPrice = sellOrder.R5[Long].get
-            // TODO: if both orders were in the same block who gets the spread?
-            if (sellOrder.creationInfo._1 >= SELF.creationInfo._1 && sellOrderTokenPrice <= tokenPrice) 
-              (tokenPrice - sellOrderTokenPrice) * returnTokenAmount
-            else 
-              0L
-          } else 
-            0L
+            val sellOrderTokenAmount = sellOrder.tokens(0)._2
+            if (sellOrder.creationInfo._1 >= SELF.creationInfo._1 && sellOrderTokenPrice <= tokenPrice) {
+              // spread is ours
+              val spreadPerToken = tokenPrice - sellOrderTokenPrice
+              // TODO: rewrite with min(returnTokensLeft, sellOrderTokenAmount)?
+              if (returnTokensLeft < sellOrderTokenAmount) {
+                val sellOrderSpread = spreadPerToken * returnTokensLeft
+                (0L, accumulatedFullSpread + sellOrderSpread)
+              } else {
+                val sellOrderSpread = spreadPerToken * sellOrderTokenAmount
+                (returnTokensLeft - sellOrderTokenAmount, accumulatedFullSpread + sellOrderSpread)
+              }
+            }
+            else {
+              // spread is not ours
+              (returnTokensLeft - min(returnTokensLeft, sellOrderTokenAmount), accumulatedFullSpread)
+            }
+          })._2
+
         }
 
         val totalMatching = (SELF.value - expectedDexFee) == returnTokenAmount * tokenPrice && 

From be35c61b2c96536a804d8b7b1c8f484aec8ea84f Mon Sep 17 00:00:00 2001
From: Denys Zadorozhnyi <denys@zadorozhnyi.com>
Date: Thu, 7 May 2020 18:39:04 +0300
Subject: [PATCH 14/23] rewrite buy order contract full spread accumulation;

---
 .../playgrounds/examples/DEXPlayground.scala      | 15 +++++----------
 1 file changed, 5 insertions(+), 10 deletions(-)

diff --git a/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala b/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
index 885554d..a262d7d 100644
--- a/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
+++ b/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
@@ -16,9 +16,9 @@ object DEXPlayground {
     val buyerContractEnv: ScriptEnv =
       Map("buyerPk" -> buyerPk, "tokenId" -> token.tokenId)
 
-    // TODO : check that counter orders are sorted by token price
-    // TODO: if both orders were in the same block who gets the spread?
+    // TODO: check that counter orders are sorted by token price
     // TODO: move price check (from fullSpread) to boxesAreSortedByTokenPrice?
+    // TODO: if both orders were in the same block who gets the spread?
     val buyerScript = s"""buyerPk || {
 
       val tokenPrice = $tokenPrice
@@ -59,14 +59,9 @@ object DEXPlayground {
             if (sellOrder.creationInfo._1 >= SELF.creationInfo._1 && sellOrderTokenPrice <= tokenPrice) {
               // spread is ours
               val spreadPerToken = tokenPrice - sellOrderTokenPrice
-              // TODO: rewrite with min(returnTokensLeft, sellOrderTokenAmount)?
-              if (returnTokensLeft < sellOrderTokenAmount) {
-                val sellOrderSpread = spreadPerToken * returnTokensLeft
-                (0L, accumulatedFullSpread + sellOrderSpread)
-              } else {
-                val sellOrderSpread = spreadPerToken * sellOrderTokenAmount
-                (returnTokensLeft - sellOrderTokenAmount, accumulatedFullSpread + sellOrderSpread)
-              }
+              val tokenAmount = min(returnTokensLeft, sellOrderTokenAmount)
+              val sellOrderSpread = spreadPerToken * tokenAmount
+              (returnTokensLeft - tokenAmount, accumulatedFullSpread + sellOrderSpread)
             }
             else {
               // spread is not ours

From 495c5ec0a1dde6c7976daca3ebc2c0b57631b305 Mon Sep 17 00:00:00 2001
From: Denys Zadorozhnyi <denys@zadorozhnyi.com>
Date: Sat, 9 May 2020 12:01:57 +0300
Subject: [PATCH 15/23] remove unused import;

---
 .../playgrounds/examples/test/DEXPlaygroundSpec.scala            | 1 -
 1 file changed, 1 deletion(-)

diff --git a/playgrounds/src/test/scala/org/ergoplatform/playgrounds/examples/test/DEXPlaygroundSpec.scala b/playgrounds/src/test/scala/org/ergoplatform/playgrounds/examples/test/DEXPlaygroundSpec.scala
index 6bb9bc8..5f65ae0 100644
--- a/playgrounds/src/test/scala/org/ergoplatform/playgrounds/examples/test/DEXPlaygroundSpec.scala
+++ b/playgrounds/src/test/scala/org/ergoplatform/playgrounds/examples/test/DEXPlaygroundSpec.scala
@@ -1,6 +1,5 @@
 package org.ergoplatform.playgrounds.examples.test
 
-import org.ergoplatform.playgrounds.examples.AssetsAtomicExchangePlayground
 import org.scalatest.PropSpec
 import org.ergoplatform.playgrounds.examples.DEXPlayground
 

From f9fd75c5d1f6f14f937de278e1f30c146a803be3 Mon Sep 17 00:00:00 2001
From: Denys Zadorozhnyi <denys@zadorozhnyi.com>
Date: Sun, 10 May 2020 16:48:54 +0300
Subject: [PATCH 16/23] implement boxesAreSortedByTokenPrice;

---
 .../playgrounds/examples/DEXPlayground.scala           | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala b/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
index a262d7d..6966d06 100644
--- a/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
+++ b/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
@@ -17,6 +17,7 @@ object DEXPlayground {
       Map("buyerPk" -> buyerPk, "tokenId" -> token.tokenId)
 
     // TODO: check that counter orders are sorted by token price
+    // TODO: show contract cost
     // TODO: move price check (from fullSpread) to boxesAreSortedByTokenPrice?
     // TODO: if both orders were in the same block who gets the spread?
     val buyerScript = s"""buyerPk || {
@@ -37,7 +38,14 @@ object DEXPlayground {
         b.R4[Coll[Byte]].isDefined && b.R4[Coll[Byte]].get == SELF.id && b.propositionBytes == buyerPk.propBytes
       }
 
-      val boxesAreSortedByTokenPrice = { (boxes: Coll[Box]) => true }
+      val boxesAreSortedByTokenPrice = { (boxes: Coll[Box]) => 
+        boxes.fold((0L, true), { (t: (Long, Boolean), box: Box) => 
+          val prevBoxTokenPrice = t._1
+          val isSorted = t._2
+          val boxTokenPrice = box.R5[Long].getOrElse(0L)
+          (boxTokenPrice, isSorted && boxTokenPrice >= prevBoxTokenPrice)
+        })._2
+      }
 
       returnBoxes.size == 1 && spendingSellOrders.size > 0 && boxesAreSortedByTokenPrice(spendingSellOrders) && {
         val returnBox = returnBoxes(0)

From 65db8a89903f517f668194bc00bb0e700cb2a41c Mon Sep 17 00:00:00 2001
From: Denys Zadorozhnyi <denys@zadorozhnyi.com>
Date: Sun, 10 May 2020 18:08:21 +0300
Subject: [PATCH 17/23] draft fullSpread for seller contract; draft multiple
 counter orders support in seller contract; expose dex fee per token in R6;

---
 .../playgrounds/examples/DEXPlayground.scala  | 76 ++++++++++++-------
 1 file changed, 50 insertions(+), 26 deletions(-)

diff --git a/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala b/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
index 6966d06..997e584 100644
--- a/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
+++ b/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
@@ -16,7 +16,7 @@ object DEXPlayground {
     val buyerContractEnv: ScriptEnv =
       Map("buyerPk" -> buyerPk, "tokenId" -> token.tokenId)
 
-    // TODO: check that counter orders are sorted by token price
+    // TODO: put contract type (sell/buy) in register and check in INPUTS filter?
     // TODO: show contract cost
     // TODO: move price check (from fullSpread) to boxesAreSortedByTokenPrice?
     // TODO: if both orders were in the same block who gets the spread?
@@ -55,7 +55,7 @@ object DEXPlayground {
         
         val foundNewOrderBoxes = OUTPUTS.filter { (b: Box) => 
           val contractParametersAreCorrect = b.R4[Coll[Byte]].get == tokenId && b.R5[Long].get == tokenPrice
-          b.R6[Coll[Byte]].isDefined && b.R6[Coll[Byte]].get == SELF.id && b.propositionBytes == SELF.propositionBytes
+          b.R7[Coll[Byte]].isDefined && b.R7[Coll[Byte]].get == SELF.id && b.propositionBytes == SELF.propositionBytes
         }
 
         val fullSpread = {
@@ -76,7 +76,6 @@ object DEXPlayground {
               (returnTokensLeft - min(returnTokensLeft, sellOrderTokenAmount), accumulatedFullSpread)
             }
           })._2
-
         }
 
         val totalMatching = (SELF.value - expectedDexFee) == returnTokenAmount * tokenPrice && 
@@ -125,32 +124,53 @@ object DEXPlayground {
         b.R4[Coll[Byte]].isDefined && b.R4[Coll[Byte]].get == SELF.id && b.propositionBytes == sellerPk.propBytes
       }
 
-      returnBoxes.size == 1 && {
-        val returnBox = returnBoxes(0)
-        val spendingBuyOrders = INPUTS.filter { (b: Box) => 
-          b.R4[Coll[Byte]].isDefined && b.R5[Long].isDefined && {
-            val buyOrderTokenId = b.R4[Coll[Byte]].get
-            buyOrderTokenId == tokenId && {
-              b.tokens.size == 1 && b.tokens(0)._1 == tokenId
-            }
-          }
+      val boxesAreSortedByTokenPrice = { (boxes: Coll[Box]) => 
+        boxes.fold((0L, true), { (t: (Long, Boolean), box: Box) => 
+          val prevBoxTokenPrice = t._1
+          val isSorted = t._2
+          val boxTokenPrice = box.R5[Long].getOrElse(0L)
+          (boxTokenPrice, isSorted && boxTokenPrice >= prevBoxTokenPrice)
+        })._2
+      }
+
+      val spendingBuyOrders = INPUTS.filter { (b: Box) => 
+        b.R4[Coll[Byte]].isDefined && b.R5[Long].isDefined && b.R6[Long].isDefined && {
+          val buyOrderTokenId = b.R4[Coll[Byte]].get
+          buyOrderTokenId == tokenId && b.tokens.size == 0 
         }
+      }
 
-        val buyOrder = spendingBuyOrders(0)
+      returnBoxes.size == 1 && spendingBuyOrders.size > 0 && boxesAreSortedByTokenPrice(spendingBuyOrders) && {
+        val returnBox = returnBoxes(0)
 
         val foundNewOrderBoxes = OUTPUTS.filter { (b: Box) => 
           val contractParametersAreCorrect = b.R4[Coll[Byte]].get == tokenId && b.R5[Long].get == tokenPrice
           val contractIsTheSame = b.propositionBytes == SELF.propositionBytes
-          b.R6[Coll[Byte]].isDefined && b.R6[Coll[Byte]].get == SELF.id && contractIsTheSame
+          b.R7[Coll[Byte]].isDefined && b.R7[Coll[Byte]].get == SELF.id && contractIsTheSame
         }
 
-        val buyOrderTokenPrice = buyOrder.R5[Long].get
-        val spreadPerToken = if (buyOrder.creationInfo._1 > SELF.creationInfo._1) 
-           buyOrderTokenPrice - tokenPrice
-        else 
-          0L
+        val fullSpread = { (tokenAmount: Long) =>
+          spendingBuyOrders.fold((tokenAmount, 0L), { (t: (Long, Long), buyOrder: Box) => 
+            val returnTokensLeft = t._1
+            val accumulatedFullSpread = t._2
+            val buyOrderTokenPrice = buyOrder.R5[Long].get
+            val buyOrderDexFeePerToken = buyOrder.R6[Long].get
+            val buyOrderTokenAmount = buyOrder.value / (buyOrderTokenPrice + buyOrderDexFeePerToken)
+            if (buyOrder.creationInfo._1 >= SELF.creationInfo._1 && buyOrderTokenPrice <= tokenPrice) {
+              // spread is ours
+              val spreadPerToken = tokenPrice - buyOrderTokenPrice
+              val tokenAmountLeft = min(returnTokensLeft, buyOrderTokenAmount)
+              val buyOrderSpread = spreadPerToken * tokenAmountLeft
+              (returnTokensLeft - tokenAmountLeft, accumulatedFullSpread + buyOrderSpread)
+            }
+            else {
+              // spread is not ours
+              (returnTokensLeft - min(returnTokensLeft, buyOrderTokenAmount), accumulatedFullSpread)
+            }
+          })._2
+        }
 
-        val totalMatching = (returnBox.value == selfTokenAmount * (tokenPrice + spreadPerToken)) 
+        val totalMatching = (returnBox.value == selfTokenAmount * tokenPrice + fullSpread(selfTokenAmount))
 
         val partialMatching = {
           foundNewOrderBoxes.size == 1 && {
@@ -165,12 +185,12 @@ object DEXPlayground {
             val tokenIdIsCorrect = newOrderTokenId == tokenId
 
             val newOrderValueIsCorrect = newOrderBox.value == (SELF.value - expectedDexFee)
-            val returnBoxValueIsCorrect = returnBox.value == soldTokenAmount * (tokenPrice + spreadPerToken)
+            val returnBoxValueIsCorrect = returnBox.value == soldTokenAmount * tokenPrice + fullSpread(soldTokenAmount)
             tokenIdIsCorrect && soldTokenAmount >= 1 && newOrderValueIsCorrect && returnBoxValueIsCorrect
           }
         }
 
-        (totalMatching ||partialMatching) && buyOrderTokenPrice >=tokenPrice
+        (totalMatching || partialMatching) 
       }
 
       }""".stripMargin
@@ -229,7 +249,8 @@ object DEXPlayground {
       value     = buyOrderBoxValue,
       script    = buyOrderContract,
       registers = R4 -> token.tokenId,
-      R5 -> buyersBidTokenPrice
+      R5 -> buyersBidTokenPrice,
+      R6 -> buyerDexFeePerToken
     )
 
     val buyOrderTransaction = Transaction(
@@ -291,7 +312,8 @@ object DEXPlayground {
       script    = newSellOrderContract,
       registers = R4 -> token.tokenId,
       R5 -> sellerAskTokenPrice,
-      R6 -> sellOrderTxSigned.outputs(0).id
+      R6 -> sellerDexFeePerToken,
+      R7 -> sellOrderTxSigned.outputs(0).id
     )
 
     val buyerTokenAmountBought     = buyerBidTokenAmount / 2
@@ -312,7 +334,8 @@ object DEXPlayground {
       script    = newBuyOrderContract,
       registers = R4 -> token.tokenId,
       R5 -> sellerAskTokenPrice,
-      R6 -> buyOrderTxSigned.outputs(0).id
+      R6 -> buyerDexFeePerToken,
+      R7 -> buyOrderTxSigned.outputs(0).id
     )
 
     val dexParty = blockchainSim.newParty("DEX")
@@ -434,7 +457,8 @@ object DEXPlayground {
       value     = buyOrderBoxValue,
       script    = buyOrderContract,
       registers = R4 -> token.tokenId,
-      R5 -> buyersBidTokenPrice
+      R5 -> buyersBidTokenPrice,
+      R6 -> buyerDexFeePerToken
     )
 
     val buyOrderTransaction = Transaction(

From 43095cb35ee0ef8782f9377c69de262c9dc31962 Mon Sep 17 00:00:00 2001
From: Denys Zadorozhnyi <denys@zadorozhnyi.com>
Date: Sun, 10 May 2020 18:21:21 +0300
Subject: [PATCH 18/23] move TODOs to PR desc;

---
 .../org/ergoplatform/playgrounds/examples/DEXPlayground.scala | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala b/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
index 997e584..0e768a4 100644
--- a/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
+++ b/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
@@ -16,10 +16,6 @@ object DEXPlayground {
     val buyerContractEnv: ScriptEnv =
       Map("buyerPk" -> buyerPk, "tokenId" -> token.tokenId)
 
-    // TODO: put contract type (sell/buy) in register and check in INPUTS filter?
-    // TODO: show contract cost
-    // TODO: move price check (from fullSpread) to boxesAreSortedByTokenPrice?
-    // TODO: if both orders were in the same block who gets the spread?
     val buyerScript = s"""buyerPk || {
 
       val tokenPrice = $tokenPrice

From e9e9505bc3d6ab76b8f6364c46fd008d9c31d51c Mon Sep 17 00:00:00 2001
From: Denys Zadorozhnyi <denys@zadorozhnyi.com>
Date: Mon, 11 May 2020 14:49:41 +0300
Subject: [PATCH 19/23] formatting;

---
 .../org/ergoplatform/playgrounds/examples/DEXPlayground.scala   | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala b/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
index 0e768a4..64a7677 100644
--- a/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
+++ b/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
@@ -82,7 +82,7 @@ object DEXPlayground {
             returnBox.value >= fullSpread
         }
 
-        val coinsSecured = partialMatching ||totalMatching
+        val coinsSecured = partialMatching || totalMatching
 
         val tokenIdIsCorrect = returnBox.tokens.getOrElse(0, (Coll[Byte](), 0L))._1 == tokenId
         

From e4798629a82e13241348f0f81769a2bb983f1710 Mon Sep 17 00:00:00 2001
From: Denys Zadorozhnyi <denys@zadorozhnyi.com>
Date: Mon, 18 May 2020 13:23:09 +0300
Subject: [PATCH 20/23] add missing new(residual) order box
 requirements(registers)

---
 .../playgrounds/examples/DEXPlayground.scala          | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala b/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
index 64a7677..a4a72e1 100644
--- a/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
+++ b/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
@@ -50,8 +50,13 @@ object DEXPlayground {
         val expectedDexFee = dexFeePerToken * returnTokenAmount
         
         val foundNewOrderBoxes = OUTPUTS.filter { (b: Box) => 
-          val contractParametersAreCorrect = b.R4[Coll[Byte]].get == tokenId && b.R5[Long].get == tokenPrice
-          b.R7[Coll[Byte]].isDefined && b.R7[Coll[Byte]].get == SELF.id && b.propositionBytes == SELF.propositionBytes
+          val tokenIdParameterIsCorrect = b.R4[Coll[Byte]].isDefined && b.R4[Coll[Byte]].get == tokenId 
+          val tokenPriceParameterIsCorrect = b.R5[Long].isDefined && b.R5[Long].get == tokenPrice
+          val dexFeePerTokenParameterIsCorrect = b.R6[Long].isDefined && b.R6[Long].get == dexFeePerToken
+          val contractParametersAreCorrect = tokenIdParameterIsCorrect && tokenPriceParameterIsCorrect
+          val referenceMe = b.R7[Coll[Byte]].isDefined && b.R7[Coll[Byte]].get == SELF.id 
+          val guardedByTheSameContract = b.propositionBytes == SELF.propositionBytes
+          contractParametersAreCorrect && referenceMe && guardedByTheSameContract
         }
 
         val fullSpread = {
@@ -329,7 +334,7 @@ object DEXPlayground {
       value     = newBuyOrderBoxValue,
       script    = newBuyOrderContract,
       registers = R4 -> token.tokenId,
-      R5 -> sellerAskTokenPrice,
+      R5 -> buyersBidTokenPrice,
       R6 -> buyerDexFeePerToken,
       R7 -> buyOrderTxSigned.outputs(0).id
     )

From 31b6bac7a184d3b479dd72ba3434a41fa6cf36dc Mon Sep 17 00:00:00 2001
From: Denys Zadorozhnyi <denys@zadorozhnyi.com>
Date: Mon, 18 May 2020 14:25:08 +0300
Subject: [PATCH 21/23] fix missing checks for residual sell order box;

---
 .../playgrounds/examples/DEXPlayground.scala           | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala b/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
index a4a72e1..588d404 100644
--- a/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
+++ b/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
@@ -145,9 +145,13 @@ object DEXPlayground {
         val returnBox = returnBoxes(0)
 
         val foundNewOrderBoxes = OUTPUTS.filter { (b: Box) => 
-          val contractParametersAreCorrect = b.R4[Coll[Byte]].get == tokenId && b.R5[Long].get == tokenPrice
-          val contractIsTheSame = b.propositionBytes == SELF.propositionBytes
-          b.R7[Coll[Byte]].isDefined && b.R7[Coll[Byte]].get == SELF.id && contractIsTheSame
+          val tokenIdParameterIsCorrect = b.R4[Coll[Byte]].isDefined && b.R4[Coll[Byte]].get == tokenId 
+          val tokenPriceParameterIsCorrect = b.R5[Long].isDefined && b.R5[Long].get == tokenPrice
+          val dexFeePerTokenParameterIsCorrect = b.R6[Long].isDefined && b.R6[Long].get == dexFeePerToken
+          val contractParametersAreCorrect = tokenIdParameterIsCorrect && tokenPriceParameterIsCorrect
+          val referenceMe = b.R7[Coll[Byte]].isDefined && b.R7[Coll[Byte]].get == SELF.id 
+          val guardedByTheSameContract = b.propositionBytes == SELF.propositionBytes
+          contractParametersAreCorrect && referenceMe && guardedByTheSameContract
         }
 
         val fullSpread = { (tokenAmount: Long) =>

From e42b5f14e9bfc50be27d69db44e40e17a3d7e58f Mon Sep 17 00:00:00 2001
From: Denys Zadorozhnyi <denys@zadorozhnyi.com>
Date: Mon, 18 May 2020 14:36:45 +0300
Subject: [PATCH 22/23] for sell order contract require spread only if strictly
 "younger" than the counter order;

---
 .../org/ergoplatform/playgrounds/examples/DEXPlayground.scala   | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala b/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
index 588d404..a201cf5 100644
--- a/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
+++ b/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala
@@ -161,7 +161,7 @@ object DEXPlayground {
             val buyOrderTokenPrice = buyOrder.R5[Long].get
             val buyOrderDexFeePerToken = buyOrder.R6[Long].get
             val buyOrderTokenAmount = buyOrder.value / (buyOrderTokenPrice + buyOrderDexFeePerToken)
-            if (buyOrder.creationInfo._1 >= SELF.creationInfo._1 && buyOrderTokenPrice <= tokenPrice) {
+            if (buyOrder.creationInfo._1 > SELF.creationInfo._1 && buyOrderTokenPrice <= tokenPrice) {
               // spread is ours
               val spreadPerToken = tokenPrice - buyOrderTokenPrice
               val tokenAmountLeft = min(returnTokensLeft, buyOrderTokenAmount)

From 152ede5189604b7da34535837747fc03a88eb3e2 Mon Sep 17 00:00:00 2001
From: Denys Zadorozhnyi <denys@zadorozhnyi.com>
Date: Tue, 2 Jun 2020 08:00:46 +0300
Subject: [PATCH 23/23] update Scastie link;

---
 README.md | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/README.md b/README.md
index efb9604..e2511bd 100644
--- a/README.md
+++ b/README.md
@@ -12,9 +12,9 @@ Enjoy:
 
 ### DEX with partial filling contracts
 
-[Run in Scastie](https://scastie.scala-lang.org/YCzvl8NBQwa7R0pVI5mHnA)
+[Run in Scastie](https://scastie.scala-lang.org/mh3h6SrESnKJwdqZjKnVkw)
 
-[Source code](https://github.com/ergoplatform/ergo-playgrounds/blob/c91117ae0b1434b7a554028592e30a5bba15a14b/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/AssetsAtomicExchangePlayground.scala#L1-L1)
+[Source code](https://github.com/ergoplatform/ergo-playgrounds/blob/e42b5f14e9bfc50be27d69db44e40e17a3d7e58f/playgrounds/src/main/scala/org/ergoplatform/playgrounds/examples/DEXPlayground.scala#L3)
 
 ### Assets Atomic Exchange contracts