check for and display simplicity transaction inputs

Author: philippem

client/src/views/tx-vin.js

@@ -1,5 +1,5 @@
 import Snabbdom from 'snabbdom-pragma'
-import { linkToParentOut, formatOutAmount, formatAssetAmount, formatHex, linkToAddr, formatNumber } from './util'
+import { linkToParentOut, formatOutAmount, formatAssetAmount, formatHex, linkToAddr, formatNumber, isSimplicitySpend, getSimplicityWitness, hexToBase64 } from './util'
 
 const layout = (vin, desc, body, { t, ...S }) =>
   <div class={{ vin: true, active: isActive(vin, S), unblinded: isUnblinded(vin) }}>
@@ -103,11 +103,38 @@ const standard = (vin, { isOpen, t, ...S }, assetMeta=getAssetMeta(vin, S)) => l
       </div>
     ] }
 
-    { vin.witness && <div className="vin-body-row">
+    { vin.witness && !isSimplicitySpend(vin) && <div className="vin-body-row">
       <div>{t`Witness`}</div>
       <div className="mono">{vin.witness.map(wit => [ ' ', wit.length ? wit : <em>&lt;empty&gt;</em> ])}</div>
     </div> }
 
+    { isSimplicitySpend(vin) && ((sw = getSimplicityWitness(vin)) => [
+      <div className="vin-body-row">
+        <div>{t`Simplicity witness data`}</div>
+        <div className="mono">{sw.witnessData}</div>
+      </div>
+
+    , <div className="vin-body-row">
+        <div>{t`Simplicity program`}</div>
+        <div className="mono">{hexToBase64(sw.program)}</div>
+      </div>
+
+    , <div className="vin-body-row">
+        <div>{t`Simplicity CMR`}</div>
+        <div className="mono">{sw.cmr}</div>
+      </div>
+
+    , <div className="vin-body-row">
+        <div>{t`Taproot control block`}</div>
+        <div className="mono">{sw.controlBlock}</div>
+      </div>
+
+    , sw.annex && <div className="vin-body-row">
+        <div>{t`Annex`}</div>
+        <div className="mono">{sw.annex}</div>
+      </div>
+    ])() }
+
     { vin.inner_redeemscript_asm && <div className="vin-body-row">
       <div>{t`P2SH redeem script`}</div>
       <div className="mono">{vin.inner_redeemscript_asm}</div>

client/src/views/util.js

@@ -121,4 +121,77 @@ export const getSupply = (asset, t) => {
   return totalSupply
 }
 
-export const strTruncate  = (str) => str.substr(0, 10) + '...' + str.substr(str.length-4, str.length);
+export const strTruncate  = (str) => str.substr(0, 10) + '...' + str.substr(str.length-4, str.length);
+
+
+// Simplicity helpers (Elements only)
+
+// Helper to check if witness has an annex (per BIP 341)
+const hasAnnex = (witness) => witness && witness.length >= 2 && witness[witness.length - 1].startsWith('50')
+
+// Get the control block element from a witness stack (accounting for optional annex)
+const getControlBlock = witness => {
+  if (!witness || witness.length < 3) return null
+  const hasAnnexBlock = hasAnnex(witness)
+  if (hasAnnexBlock) {
+    return witness[witness.length - 2]
+  }
+  return witness[witness.length - 1]
+}
+
+// Check if a vin is a P2TR Simplicity spend
+// A P2TR Simplicity spend has:
+// - 4 witness elements (or 5 with optional annex)
+// - Control block starts with 'be' or 'bf' (leaf version for Simplicity)
+export const isSimplicitySpend = vin => {
+  if (!process.env.IS_ELEMENTS || !vin.witness) return false
+
+  const witnessLen = vin.witness.length
+  const hasAnnexBlock = hasAnnex(vin.witness)
+
+  // Must be 4 elements without annex, or 5 elements with annex
+  if (witnessLen !== 4 && !(witnessLen === 5 && hasAnnexBlock)) return false
+
+  const controlBlock = getControlBlock(vin.witness)
+  return controlBlock && (controlBlock.startsWith('be') || controlBlock.startsWith('bf'))
+}
+
+// Extract Simplicity witness components from a vin
+// Returns: { witnessData, program, cmr, controlBlock, annex }
+export const getSimplicityWitness = vin => {
+  if (!isSimplicitySpend(vin)) return null
+
+  const witness = vin.witness
+  const hasAnnexBlock = hasAnnex(witness)
+
+  if (hasAnnexBlock && witness.length === 5) {
+    return {
+      witnessData: witness[0],
+      program: witness[1],
+      cmr: witness[2],
+      controlBlock: witness[3],
+      annex: witness[4]
+    }
+  }
+
+  return {
+    witnessData: witness[0],
+    program: witness[1],
+    cmr: witness[2],
+    controlBlock: witness[3],
+    annex: null
+  }
+}
+
+// Convert hex string to base64
+export const hexToBase64 = hex => {
+    if (process.browser) {
+        // Browser environment
+        const bytes = hex.match(/.{1,2}/g).map(byte => parseInt(byte, 16))
+        const binary = String.fromCharCode(...bytes)
+        return btoa(binary)
+    } else {
+        // Node environment (for pre-rendering)
+        return Buffer.from(hex, 'hex').toString('base64')
+    }
+}