Show the spending transaction of spent outputs

app/api/electrumAddressApi.js

@@ -353,6 +353,57 @@ function lookupTxBlockHash(txid) {
 	});
 }
 
+// Lookup the spending transaction and height of a given transaction output. Only works with Electrum 1.5 protocol, ElectRS 0.9.0 does not implement subscriptions
+// but can return the transaction spending the given outpoint
+function lookupOutpointsTx(outpoints) {
+	if (electrumClients.length == 0) {
+		return Promise.reject({ error: "Not supported by Electrum 1.4", userText: noConnectionsErrorText });
+	}
+
+	if (outpoints.length == 0) {
+		return Promise.resolve(null);
+	}
+	return runOnAllServers(function(electrumClient) {
+		return new Promise((resolve, reject) => {
+			let contents = [];
+			let arguments_far_calls = {};
+			for (let outpoint of outpoints) {
+				const id = ++electrumClient.id;
+				const request = utils.makeRequest('blockchain.outpoint.subscribe', outpoint, id);
+				contents.push(request);
+				arguments_far_calls[id] = outpoint;
+			}
+			const content = '[' + contents.join(',') + ']';
+			const promise = utils.createPromiseResultBatch(resolve, reject, arguments_far_calls);
+			electrumClient.callback_message_queue[electrumClient.id] = promise;
+			electrumClient.conn.write(content + '\n');
+		});
+	}).then(function(results) {
+		runOnAllServers(function(electrumClient) {
+			return new Promise((resolve, reject) => {
+                        	let contents = [];
+                        	let arguments_far_calls = {};
+                        	for (let outpoint of outpoints) {
+                        	       	const id = ++electrumClient.id;
+                               		const request = utils.makeRequest('blockchain.outpoint.unsubscribe', outpoint, id);
+                               		contents.push(request);
+					arguments_far_calls[id] = outpoint;
+				}
+                        	const content = '[' + contents.join(',') + ']';
+				const promise = utils.createPromiseResultBatch(resolve, reject, arguments_far_calls);
+                        	electrumClient.callback_message_queue[electrumClient.id] = promise;
+                        	electrumClient.conn.write(content + '\n');
+			});
+		});
+		const spend_infos = results[0].result;
+		if (results.slice(1).every(({ result }) => result == spend_infos)) {
+                        return spend_infos;
+                } else {
+                        return Promise.reject({conflictedResults:results});
+                }
+	});
+}
+
 function logStats(cmd, dt, success) {
 	if (!global.electrumStats.rpc[cmd]) {
 		global.electrumStats.rpc[cmd] = {count:0, time:0, successes:0, failures:0};
@@ -380,5 +431,6 @@ module.exports = {
 	connectToServers: connectToServers,
 	getAddressDetails: getAddressDetails,
 	lookupTxBlockHash: lookupTxBlockHash,
+	lookupOutpointsTx: lookupOutpointsTx,
 };
 

app/utils.js

@@ -1167,6 +1167,28 @@ function bip32Addresses(extPubkey, addressType, account, limit=10, offset=0) {
 	return addresses;
 }
 
+function createPromiseResultBatch(resolve, reject, argz) {
+	return (err, result) => {
+		if (result && result[0] && result[0].id) {
+			// this is a batch request response
+			for (let r of result) {
+				r.param = argz[r.id];
+			}
+		}
+		if (err) reject(err);
+		else resolve(result);
+	};
+};
+
+function makeRequest(method, params, id) {
+	return JSON.stringify({
+		jsonrpc: '2.0',
+		method: method,
+		params: params,
+		id: id,
+	});
+};
+
 module.exports = {
 	reflectPromise: reflectPromise,
 	redirectToConnectPageIfNeeded: redirectToConnectPageIfNeeded,
@@ -1220,5 +1242,7 @@ module.exports = {
 	getVoutAddress: getVoutAddress,
 	getVoutAddresses: getVoutAddresses,
 	xpubChangeVersionBytes: xpubChangeVersionBytes,
-	bip32Addresses: bip32Addresses
+	bip32Addresses: bip32Addresses,
+	createPromiseResultBatch: createPromiseResultBatch,
+	makeRequest: makeRequest,
 };

routes/baseRouter.js

@@ -26,6 +26,7 @@ const coins = require("./../app/coins.js");
 const config = require("./../app/config.js");
 const coreApi = require("./../app/api/coreApi.js");
 const addressApi = require("./../app/api/addressApi.js");
+const electrumAddressApi = require("./../app/api/electrumAddressApi.js");
 const rpcApi = require("./../app/api/rpcApi.js");
 const btcQuotes = require("./../app/coins/btcQuotes.js");
 
@@ -1433,6 +1434,29 @@ router.get("/tx/:transactionId", asyncHandler(async (req, res, next) => {
 
 		await Promise.all(promises);
 
+		// Electrs 0.9.0 support spending transaction lookup for an outpoint
+		if ((config.addressApi == "electrum" || config.addressApi == "electrumx")  && config.electrumTxIndex) {
+			let outpoints = [];
+			for (const vout in tx.vout) {
+				if (res.locals.utxos[vout] == null) {
+					outpoints.push([txid, parseInt(vout)]);
+				}
+			}
+
+			const spent_outpoints = await electrumAddressApi.lookupOutpointsTx(outpoints);
+			let spendings_status = [];
+			let spent_idx = 0;
+			for (const vout in tx.vout) {
+				if (res.locals.utxos[vout] == null) {
+					spendings_status.push(spent_outpoints[spent_idx].result);
+					++spent_idx;
+				} else {
+					spendings_status.push(false)
+				}
+			}
+			res.locals.spendings = spendings_status
+		}
+
 		if (global.specialTransactions && global.specialTransactions[txid]) {
 			let funInfo = global.specialTransactions[txid];
 

views/includes/transaction-io-details.pug

@@ -294,6 +294,17 @@ mixin outputValueDisplay(vout, voutIndex)
 									+darkBadge
 										span(title=`Output Type: ${utils.outputTypeName(vout.scriptPubKey.type)}`, data-bs-toggle="tooltip") #{utils.outputTypeAbbreviation(vout.scriptPubKey.type)}
 
+						if (spendings)
+							- var spending_vout = spendings[voutIndex];
+							if (spending_vout)
+								span.mt-1 spent by 
+								a(href=`./tx/${spending_vout.spender_txhash}`) #{utils.ellipsizeMiddle(spending_vout.spender_txhash,9)}
+								if (spending_vout.spender_height > 0 && spending_vout.spender_height > spending_vout.height)
+									span  #{spending_vout.spender_height - spending_vout.height} blocks later
+								else if (spending_vout.spender_height <= 0)
+									span  in the mempool
+								else if (spending_vout.spender_height == spending_vout.height)
+									span  in the same block
 
 					span.ms-2.float-end
 						+outputValueDisplay(vout, voutIndex)