Add backend endpoint to fetch prevouts

backend/src/api/bitcoin/bitcoin.routes.ts

@@ -12,7 +12,7 @@ import backendInfo from '../backend-info';
 import transactionUtils from '../transaction-utils';
 import { IEsploraApi } from './esplora-api.interface';
 import loadingIndicators from '../loading-indicators';
-import { TransactionExtended } from '../../mempool.interfaces';
+import { MempoolTransactionExtended, TransactionExtended } from '../../mempool.interfaces';
 import logger from '../../logger';
 import blocks from '../blocks';
 import bitcoinClient from './bitcoin-client';
@@ -49,6 +49,7 @@ class BitcoinRoutes {
       .post(config.MEMPOOL.API_URL_PREFIX + 'psbt/addparents', this.postPsbtCompletion)
       .get(config.MEMPOOL.API_URL_PREFIX + 'blocks-bulk/:from', this.getBlocksByBulk.bind(this))
       .get(config.MEMPOOL.API_URL_PREFIX + 'blocks-bulk/:from/:to', this.getBlocksByBulk.bind(this))
+      .post(config.MEMPOOL.API_URL_PREFIX + 'prevouts', this.$getPrevouts)
       // Temporarily add txs/package endpoint for all backends until esplora supports it
       .post(config.MEMPOOL.API_URL_PREFIX + 'txs/package', this.$submitPackage)
       ;
@@ -824,6 +825,53 @@ class BitcoinRoutes {
     }
   }
 
+  private async $getPrevouts(req: Request, res: Response) {
+    try {
+      const outpoints = req.body;
+      if (!Array.isArray(outpoints) || outpoints.some((item) => !/^[a-fA-F0-9]{64}$/.test(item.txid) || typeof item.vout !== 'number')) {
+        return res.status(400).json({ error: 'Invalid input format' });
+      }
+
+      if (outpoints.length > 100) {
+        return res.status(400).json({ error: 'Too many prevouts requested' });
+      }
+
+      const result = Array(outpoints.length).fill(null);
+      const memPool = mempool.getMempool();
+
+      for (let i = 0; i < outpoints.length; i++) {
+        const outpoint = outpoints[i];
+        let prevout: IEsploraApi.Vout | null = null;
+        let tx: MempoolTransactionExtended | null = null;
+
+        const mempoolTx = memPool[outpoint.txid];
+        if (mempoolTx) {
+          prevout = mempoolTx.vout[outpoint.vout];
+          tx = mempoolTx;
+        } else {
+          const rawPrevout = await bitcoinClient.getTxOut(outpoint.txid, outpoint.vout, false);
+          if (rawPrevout) {
+            prevout = {
+              value: Math.round(rawPrevout.value * 100000000),
+              scriptpubkey: rawPrevout.scriptPubKey.hex,
+              scriptpubkey_asm: rawPrevout.scriptPubKey.asm ? transactionUtils.convertScriptSigAsm(rawPrevout.scriptPubKey.hex) : '',
+              scriptpubkey_type: transactionUtils.translateScriptPubKeyType(rawPrevout.scriptPubKey.type),
+              scriptpubkey_address: rawPrevout.scriptPubKey && rawPrevout.scriptPubKey.address ? rawPrevout.scriptPubKey.address : '',
+            };
+          }
+        }
+
+        if (prevout) {
+          result[i] = { prevout, tx };
+        }
+      }
+
+      res.json(result);
+
+    } catch (e) {
+      handleError(req, res, 500, e instanceof Error ? e.message : e);
+    }
+  }
 }
 
 export default new BitcoinRoutes();

backend/src/api/transaction-utils.ts

@@ -420,6 +420,29 @@ class TransactionUtils {
 
     return { prioritized, deprioritized };
   }
+
+  // Copied from https://github.com/mempool/mempool/blob/14e49126c3ca8416a8d7ad134a95c5e090324d69/backend/src/api/bitcoin/bitcoin-api.ts#L324
+  public translateScriptPubKeyType(outputType: string): string {
+    const map = {
+      'pubkey': 'p2pk',
+      'pubkeyhash': 'p2pkh',
+      'scripthash': 'p2sh',
+      'witness_v0_keyhash': 'v0_p2wpkh',
+      'witness_v0_scripthash': 'v0_p2wsh',
+      'witness_v1_taproot': 'v1_p2tr',
+      'nonstandard': 'nonstandard',
+      'multisig': 'multisig',
+      'anchor': 'anchor',
+      'nulldata': 'op_return'
+    };
+
+    if (map[outputType]) {
+      return map[outputType];
+    } else {
+      return 'unknown';
+    }
+  }
+  
 }
 
 export default new TransactionUtils();