Prototyping burn op_return creation function

src/slp/tokentype1.js

@@ -32,6 +32,93 @@ class TokenType1 {
    *  - outputs: an integer with a value of 1 or 2. If 2, indicates there needs to be an extra output to send token change.
    */
   generateSendOpReturn(tokenUtxos, sendQty) {
+    try {
+      const tokenId = tokenUtxos[0].tokenId
+      const decimals = tokenUtxos[0].decimals
+
+      // Calculate the total amount of tokens owned by the wallet.
+      let totalTokens = 0
+      for (let i = 0; i < tokenUtxos.length; i++)
+        totalTokens += tokenUtxos[i].tokenQty
+
+      const change = totalTokens - sendQty
+      // console.log(`change: ${change}`)
+
+      let script
+      let outputs = 1
+
+      // The normal case, when there is token change to return to sender.
+      if (change > 0) {
+        outputs = 2
+
+        let baseQty = new BigNumber(sendQty).times(10 ** decimals)
+        baseQty = baseQty.absoluteValue()
+        baseQty = Math.floor(baseQty)
+        let baseQtyHex = baseQty.toString(16)
+        baseQtyHex = baseQtyHex.padStart(16, "0")
+
+        let baseChange = new BigNumber(change).times(10 ** decimals)
+        baseChange = baseChange.absoluteValue()
+        baseChange = Math.floor(baseChange)
+        // console.log(`baseChange: ${baseChange.toString()}`)
+
+        let baseChangeHex = baseChange.toString(16)
+        baseChangeHex = baseChangeHex.padStart(16, "0")
+        // console.log(`baseChangeHex padded: ${baseChangeHex}`)
+
+        script = [
+          this.Script.opcodes.OP_RETURN,
+          Buffer.from("534c5000", "hex"),
+          //BITBOX.Script.opcodes.OP_1,
+          Buffer.from("01", "hex"),
+          Buffer.from(`SEND`),
+          Buffer.from(tokenId, "hex"),
+          Buffer.from(baseQtyHex, "hex"),
+          Buffer.from(baseChangeHex, "hex")
+        ]
+      } else {
+        // Corner case, when there is no token change to send back.
+
+        let baseQty = new BigNumber(sendQty).times(10 ** decimals)
+        baseQty = baseQty.absoluteValue()
+        baseQty = Math.floor(baseQty)
+        let baseQtyHex = baseQty.toString(16)
+        baseQtyHex = baseQtyHex.padStart(16, "0")
+
+        // console.log(`baseQty: ${baseQty.toString()}`)
+
+        script = [
+          this.Script.opcodes.OP_RETURN,
+          Buffer.from("534c5000", "hex"),
+          //BITBOX.Script.opcodes.OP_1,
+          Buffer.from("01", "hex"),
+          Buffer.from(`SEND`),
+          Buffer.from(tokenId, "hex"),
+          Buffer.from(baseQtyHex, "hex")
+        ]
+      }
+
+      return { script, outputs }
+    } catch (err) {
+      console.log(`Error in generateSendOpReturn()`)
+      throw err
+    }
+  }
+
+  /**
+   * @api SLP.TokenType1.generateBurnOpReturn() generateBurnOpReturn() - OP_RETURN code for SLP Send tx
+   * @apiName generateBurnOpReturn
+   * @apiGroup SLP
+   * @apiDescription Generate the OP_RETURN value needed to create an SLP Send transaction that burns tokens.
+   * This is a slight variation of generateSendOpReturn(). It generates an SLP
+   * SEND transaction designed to burn a select quantity of tokens.
+   *
+   * It's assumed all elements in the tokenUtxos array belong to the same token.
+   * Returns an object with two properties:
+   *  - script: an array of Bufers that is ready to fed into bchjs.Script.encode() to be turned into a transaction output.
+   *  - outputs: an integer with a value of 1. There is no token change to be sent with this transaction.
+   */
+  generateBurnOpReturn(tokenUtxos, sendQty) {
     try {
       const tokenId = tokenUtxos[0].tokenId
       const decimals = tokenUtxos[0].decimals

test/unit/slp-tokentype1.js

@@ -70,6 +70,41 @@ describe("#SLP TokenType1", () => {
       assert.hasAllKeys(result, ["script", "outputs"])
       assert.isNumber(result.outputs)
     })
+
+    //   it("should handle problematic configuration", async () => {
+    //     // Mock UTXO.
+    //     const tokenUtxos = [
+    //       {
+    //         txid:
+    //           "0bd6b874246202b4cbc2f501419a5ce6f9b01e8ba9521298afd15c7e8eac5951",
+    //         vout: 2,
+    //         value: "546",
+    //         confirmations: 0,
+    //         satoshis: 546,
+    //         utxoType: "token",
+    //         transactionType: "send",
+    //         tokenId:
+    //           "155784a206873c98acc09e8dabcccf6abf13c4c14d8662190534138a16bb93ce",
+    //         tokenTicker: "PSF",
+    //         tokenName: "PSF Testnet Token",
+    //         tokenDocumentUrl: "",
+    //         tokenDocumentHash: "",
+    //         decimals: 8,
+    //         tokenQty: 18004.71169917
+    //       }
+    //     ]
+    //
+    //     const result = await bchjs.SLP.TokenType1.generateSendOpReturn(
+    //       tokenUtxos,
+    //       5000
+    //     )
+    //     console.log(`result: ${JSON.stringify(result, null, 2)}`)
+    //
+    //     // console.log(`decoded: ${result.script[6].toString("ascii")}`)
+    //     // const msg = Buffer.from(result.script[6], "hex").toString("ascii")
+    //     const msg = result.script[6].toString("ascii")
+    //     console.log(`msg: ${msg}`)
+    //   })
   })
 
   describe("#generateGenesisOpReturn", () => {