From 587a0786ad276a30d4faa1325680a32bf4f02b01 Mon Sep 17 00:00:00 2001
From: Felicio Mununga <felicio@users.noreply.github.com>
Date: Fri, 10 Feb 2023 10:09:42 +0100
Subject: [PATCH] add `decompress-public-key.ts` (#336)

---
 .../src/utils/decompress-public-key.test.ts   | 30 +++++++++++++++++++
 .../src/utils/decompress-public-key.ts        | 10 +++++++
 2 files changed, 40 insertions(+)
 create mode 100644 packages/status-js/src/utils/decompress-public-key.test.ts
 create mode 100644 packages/status-js/src/utils/decompress-public-key.ts

diff --git a/packages/status-js/src/utils/decompress-public-key.test.ts b/packages/status-js/src/utils/decompress-public-key.test.ts
new file mode 100644
index 00000000..8223cae4
--- /dev/null
+++ b/packages/status-js/src/utils/decompress-public-key.test.ts
@@ -0,0 +1,30 @@
+import * as secp from 'ethereum-cryptography/secp256k1'
+import { bytesToHex } from 'ethereum-cryptography/utils'
+import { expect, test } from 'vitest'
+
+import { decompressPublicKey } from './decompress-public-key'
+
+test('should return decompressed public key', () => {
+  const privateKey = secp.utils.randomPrivateKey()
+
+  const publicKey = bytesToHex(secp.getPublicKey(privateKey))
+  const compressedPublicKey = bytesToHex(secp.getPublicKey(privateKey, true))
+
+  expect(decompressPublicKey(compressedPublicKey)).toEqual(publicKey)
+})
+
+test('should accept public key with a base prefix', () => {
+  const privateKey = secp.utils.randomPrivateKey()
+
+  const publicKey = bytesToHex(secp.getPublicKey(privateKey))
+  const compressedPublicKey =
+    '0x' + bytesToHex(secp.getPublicKey(privateKey, true))
+
+  expect(decompressPublicKey(compressedPublicKey)).toEqual(publicKey)
+})
+
+test('should throw error if public key is not a valid hex', () => {
+  expect(() => {
+    decompressPublicKey('not a valid public key')
+  }).toThrowErrorMatchingInlineSnapshot(`"Invalid public key"`)
+})
diff --git a/packages/status-js/src/utils/decompress-public-key.ts b/packages/status-js/src/utils/decompress-public-key.ts
new file mode 100644
index 00000000..a0eb345e
--- /dev/null
+++ b/packages/status-js/src/utils/decompress-public-key.ts
@@ -0,0 +1,10 @@
+import * as secp from 'ethereum-cryptography/secp256k1'
+
+export function decompressPublicKey(publicKey: string): string {
+  try {
+    const pk = publicKey.replace(/^0[xX]/, '') // ensures hexadecimal digits without "base prefix"
+    return secp.Point.fromHex(pk).toHex()
+  } catch (error) {
+    throw new Error('Invalid public key')
+  }
+}