Added genDeposit function

ts/__tests__/libcream.test.ts

@@ -1,8 +1,9 @@
 import {
     createDeposit,
+    generateDeposit,
     pedersenHash,
     rbigInt,
-    bigInt,
+    toHex
 } from '../'
 
 describe('creamlib utilities', () => {
@@ -17,5 +18,16 @@ describe('creamlib utilities', () => {
             expect(deposit.commitment.toString()).toEqual(pedersenHash(preimage).babyJubX.toString())
             expect(deposit.nullifierHash.toString()).toEqual(pedersenHash(nullifier_buf).babyJubX.toString())
         })
+
+        it('should generate `Deposit` object from deposit note correctly', () => {
+            const nullifier = rbigInt(31)
+            const secret = rbigInt(31)
+            const deposit = createDeposit(nullifier, secret)
+
+            const note = toHex(deposit.preimage, 62)
+            const generatedDeposit = generateDeposit(note)
+
+            expect(deposit.commitment.toString()).toEqual(generatedDeposit.commitment.toString())
+        })
     })
 })

ts/index.ts

@@ -19,6 +19,14 @@ interface Deposit {
 
 const bigInt = snarkjs.bigInt
 
+const toHex = (
+    n: SnarkBigInt,
+    length = 31
+): string => {
+    const str = n instanceof Buffer ? n.toString('hex') : bigInt(n).toString(16)
+    return '0x' + str.padStart(length * 2, '0')
+}
+
 const pedersenHash = (
     value: SnarkBigInt
 ): PedersenHash => {
@@ -54,10 +62,22 @@ const createDeposit = (
     }
 }
 
+const generateDeposit = (
+    note: string
+): Deposit => {
+    const buf: Buffer = Buffer.from(note.slice(2), 'hex')
+    return createDeposit(
+        bigInt.leBuff2int(buf.slice(0, 31)),
+        bigInt.leBuff2int(buf.slice(31, 62))
+    )
+}
+
 export {
     SnarkBigInt,
     bigInt,
+    toHex,
     pedersenHash,
     rbigInt,
     createDeposit,
+    generateDeposit
 }