ergoscript-by-example

README.md

@@ -29,6 +29,7 @@ For an overarching summary of how everything in this repo works, please referenc
 | 8 | Expert | [Token sales service contract](tokenSalesService.md) |
 | 9 | Beginner | [Self-Replicating Sale Contract](selfReplicatingTokenSale.md) |
 | 10 | Intermediate | [Heads or Tails game Contract](headsOrTails.md) |
+| 11 | Beginner | [Loser pays](loserPays.md) |
 
 ## Extra Resources To Get Started
 If you are unfamiliar with the Extended UTXO model, smart contracts, or Ergo specifically, the above examples may be a little bit challenging to jump straight into. As such the following links below are recommended resources for getting a solid background in understanding what is going on:

loserPays.md

@@ -0,0 +1,154 @@
+Loser pays
+=================================
+
+* Author: ladopixel
+* Created: November 9 2021
+* License: CC0
+* Difficulty: (Beginner)
+* Ergo Playground Link: [Loser pays](https://scastie.scala-lang.org/SqWeyRSLSNS46AxI4p1t0g)
+
+Description
+----------
+Very simple game example.
+
+In the scene there are 2 players and a waiter.
+Each player receives the same amount of NanoErgs, while the waiter has 0.
+A random number between 0 and 100 is generated, with which each player has a 50% chance of winning or losing.
+The losing player sends his NanoErgs to the waiter as payment.
+
+Code
+----------
+#### [Click Here To Run The Code Via The Ergo Playground](https://scastie.scala-lang.org/SqWeyRSLSNS46AxI4p1t0g)
+```scala
+
+// I import the necessary for everything to work properly
+import org.ergoplatform.compiler.ErgoScalaCompiler._
+import org.ergoplatform.playgroundenv.utils.ErgoScriptCompiler
+import org.ergoplatform.playground._
+
+// I create some immutable variables and another mutable one
+// Define scenario, players and quantities
+val randomPay = scala.util.Random
+val blockchainGame = newBlockChainSimulationScenario("game blockchain")
+val player1 = blockchainGame.newParty("player1")
+val player2 = blockchainGame.newParty("player2")
+val waiter = blockchainGame.newParty("waiter")
+val funds = 900000000
+
+var winner = 0
+
+// Sending to the players' wallet 900000000 nanoergs
+player1.generateUnspentBoxes(toSpend = funds)
+player2.generateUnspentBoxes(toSpend = funds)
+
+// I print on the screen the current situation:
+// Player 1: 900000000
+// Player 2: 900000000
+// Waiter: 0
+println("------------------------")
+println("The one who loses pays")
+println("------------------------")
+println("Starting balance")
+player1.printUnspentAssets()
+player2.printUnspentAssets()
+waiter.printUnspentAssets()
+println("---------------------")
+
+// I urge the contract to be fulfilled
+val trueScript = "sigmaProp(1 == 1)"
+val trueContract = ErgoScriptCompiler.compile(Map(), trueScript)
+
+val maximoParaEnviar = (funds - MinTxFee)
+
+// I generate a random number less than 100, if randomPay > 50 the winner is player 2, if randomPay < 50 the winner is player 1
+if(randomPay.nextInt(100) > 50) {
+    winner = 2
+
+    // We create the first box, blocking the funds to the contract and assigning values.
+    val trueBox = Box(value = maximoParaEnviar, script = trueContract)
+
+    // R0: NanoErgs - 1 Erg = 1000000000 NanoErgs
+    // R1: The smart contract script
+    // R2: Aditionals actives (generated automatically)
+    // R3: txId (generated automatically)
+
+    // Aditionals registers R4, R5, R6, R7, R8, R9 in a NFT Picture or Audio
+    // R4: Name
+    // R5: Description
+    // R6: Decimals
+    // R7: Picture 0e020101 - Audio 0e020102
+    // R8: SHA256 
+    // R9: Optional link to the artwork
+
+
+    // We create the transaction taking into account that we will have inputs, outputs, fee and to return the change.
+    val depositTransaction = Transaction(
+        inputs       = player1.selectUnspentBoxes(toSpend = funds),
+        outputs      = List(trueBox),
+        fee          = MinTxFee,
+        sendChangeTo = player1.wallet.getAddress
+        )
+
+    // We sign the transaction deposit to verify that it comes from the player 1.
+    val depositTransactionSigned = player1.wallet.sign(depositTransaction)
+
+    // We send the tx to the game blockchain.
+    blockchainGame.send(depositTransactionSigned)
+
+    // We withdraw funds from the contract 
+    val withdrawBox =Box(value = maximoParaEnviar - MinTxFee,
+                    script = contract(waiter.wallet.getAddress.pubKey))
+
+    // We create the withdrawal transaction "The input will be the previous output"
+    // input: depositTransactionSigned.outputs(0) 
+    val withdrawTransaction = Transaction(
+        inputs       = List(depositTransactionSigned.outputs(0)),
+        outputs      = List(withdrawBox),
+        fee          = MinTxFee,
+        sendChangeTo = player1.wallet.getAddress
+        )
+
+    // Sign the transaction
+    val withdrawTransactionSigned = player1.wallet.sign(withdrawTransaction)
+    // We send the transaction to blockchainGame
+    blockchainGame.send(withdrawTransactionSigned)
+}else{
+    winner = 1
+    val trueBox = Box(value = maximoParaEnviar, script = trueContract)
+    val depositTransaction = Transaction(
+        inputs       = player2.selectUnspentBoxes(toSpend = funds),
+        outputs      = List(trueBox),
+        fee          = MinTxFee,
+        sendChangeTo = player2.wallet.getAddress
+    )
+    val depositTransactionSigned = player2.wallet.sign(depositTransaction)
+    blockchainGame.send(depositTransactionSigned)
+    val withdrawBox =Box(value = maximoParaEnviar - MinTxFee,
+                    script = contract(waiter.wallet.getAddress.pubKey))
+    val withdrawTransaction = Transaction(
+        inputs       = List(depositTransactionSigned.outputs(0)),
+        outputs      = List(withdrawBox),
+        fee          = MinTxFee,
+        sendChangeTo = player2.wallet.getAddress
+        )
+    val withdrawTransactionSigned = player1.wallet.sign(withdrawTransaction)
+    blockchainGame.send(withdrawTransactionSigned)
+}
+
+// We print the result on the screen
+println("------------------------")
+if (winner == 1){
+    println("PLAYER 1 WIN keeps its funds.")
+}else{
+    println("PLAYER 2 WIN keeps its funds.")
+}
+println("------------------------")
+println("Current balance")
+println("---------------------")
+player1.printUnspentAssets()
+player2.printUnspentAssets()
+waiter.printUnspentAssets()
+println("....gas:" + MinTxFee)
+println("------------------------")
+
+```