Identify Input Payload Contracts

routes/baseActionsRouter.js

@@ -831,6 +831,49 @@ function isFlipstarter(tx, fee) {
   }
 }
 
+/**
+ * If transaction is a 'Transaction Input Payload Contract', this returns the
+ * payload it carries. Otherwise null.
+ * https://nerdekollektivet.gitlab.io/votepeer-documentation/input-payload-contract/
+ */
+function getInputPayloadContractPayload(tx) {
+	let scriptSig = "";
+	try {
+		scriptSig = tx.vin[0].scriptSig.hex;
+        scriptAsm = tx.vin[0].scriptSig.asm;
+	} catch (e) {
+		// API change?
+		return null;
+	}
+	const redeemscript_regex = /a97ca97e7ca97e21[a-z0-9]{66}76a97b7ea914[a-z0-9]{40}88ad7491$/;
+	if (!scriptSig.match(redeemscript_regex)) {
+		return null;
+	}
+    try {
+        const stackElements = scriptAsm.split(' ');
+        stackElements.pop(); // redeemscript
+        const push3 = stackElements.pop();
+        if (push3 === undefined) return null;
+        const push2 = stackElements.pop();
+        if (push2 === undefined) return null;
+        const push1 = stackElements.pop();
+        if (push1 === undefined) return null;
+
+        let payload = push3;
+        if (push2 !== '0') {
+            payload += push2;
+        }
+        if (push1 !== '0') {
+            payload += push1;
+        }
+        return payload;
+    }
+    catch (e) {
+        console.log(e);
+        return null;
+    }
+}
+
 function calcFee(tx, inputTxs) {
   let inputAmount = new Decimal(0);
   let outputAmount = new Decimal(0);
@@ -875,6 +918,7 @@ router.get("/tx/:transactionId", function(req, res, next) {
 		res.locals.result.txInputs = rawTxResult.txInputsByTransaction[txid]
 		const fee = calcFee(tx, rawTxResult.txInputsByTransaction[txid]);
 		res.locals.result.isflipstarter = isFlipstarter(tx, fee);
+		res.locals.result.inputPayloadContract = getInputPayloadContractPayload(tx);
 
 		var promises = [];
 

views/transaction.pug

@@ -235,6 +235,15 @@ block content
 
 								p Run 
 									a(href=("https://flipstarter.cash")) your own flipstarter crowdfunding campaign.
+						if (result.inputPayloadContract != null)
+							p This looks like an 
+								a(href=("https://nerdekollektivet.gitlab.io/votepeer-documentation/input-payload-contract/")) Input Payload Contract
+								span  transaction. Input Payload Contract is used to deliver a chunk of arbitrary data on the blockchain.
+
+							p The embedded data is #{result.inputPayloadContract.length} bytes. This is the embedded data:
+								div.highlight
+									pre
+										code.json.bg-light(data-lang="json") "#{result.inputPayloadContract}"