From beb2331e417a3f5796b044b31513a4fd2a7fe446 Mon Sep 17 00:00:00 2001
From: Evan Hahn <me@evanhahn.com>
Date: Wed, 26 Jun 2024 10:49:30 -0500
Subject: [PATCH] feat: keyToInviteId (#26)

Similar to `keyToPublicId`, this adds a `keyToInviteId` for deriving an
invite ID.

This was originally added in `@mapeo/core` but should live here instead.
See <https://github.com/digidem/mapeo-core-next/pull/571>.
---
 index.js            |  2 ++
 tests/utils.test.js | 20 +++++++++++++++++++-
 utils.js            | 12 ++++++++++++
 3 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/index.js b/index.js
index 928825b..7a32c97 100644
--- a/index.js
+++ b/index.js
@@ -3,6 +3,7 @@ const {
   sign,
   verifySignature,
   keyToPublicId,
+  keyToInviteId,
 } = require('./utils.js')
 
 exports.KeyManager = require('./key-manager')
@@ -10,3 +11,4 @@ exports.invites = require('./project-invites')
 exports.sign = sign
 exports.verifySignature = verifySignature
 exports.keyToPublicId = keyToPublicId
+exports.keyToInviteId = keyToInviteId
diff --git a/tests/utils.test.js b/tests/utils.test.js
index 276f9a4..4e75615 100644
--- a/tests/utils.test.js
+++ b/tests/utils.test.js
@@ -5,7 +5,8 @@ const {
   KeyManager,
   sign,
   verifySignature,
-  keyToPublicId
+  keyToPublicId,
+  keyToInviteId,
 } = require('../')
 const z32 = require('z32')
 
@@ -38,3 +39,20 @@ test('key to public ID', function (t) {
   )
   t.end()
 })
+
+test('key to invite ID', (t) => {
+  const key = createHash('sha256').update('test key').digest()
+  const inviteId = keyToInviteId(key)
+  t.same(
+    inviteId,
+    Buffer.from('eQro+t0dzx2AFf3h9Bh5A94i0YdR19xJkq+NGny+IS0=', 'base64'),
+    'checks for consistency - a change is a breaking change'
+  )
+  t.same(keyToInviteId(key), inviteId, 'deterministic')
+  t.notSame(
+    key,
+    inviteId,
+    "didn't do something dumb and encode without hashing"
+  )
+  t.end()
+})
diff --git a/utils.js b/utils.js
index 98f0fcf..e19e028 100644
--- a/utils.js
+++ b/utils.js
@@ -3,6 +3,7 @@ const sodium = require('sodium-universal')
 const z32 = require('z32')
 
 const MAPEO = Buffer.from('mapeo')
+const PROJECT_INVITE_ID_SALT = Buffer.from('mapeo project invite id', 'ascii')
 
 /**
  * Sign message using secretKey
@@ -41,3 +42,14 @@ exports.keyToPublicId = function (key) {
   sodium.crypto_generichash(digest, MAPEO, key)
   return z32.encode(digest)
 }
+
+/**
+ * Generate an invite ID from a project key
+ * @param {Readonly<Buffer>} key
+ * @returns {Buffer}
+ */
+exports.keyToInviteId = function (key) {
+  const digest = Buffer.allocUnsafe(32)
+  sodium.crypto_generichash(digest, PROJECT_INVITE_ID_SALT, key)
+  return digest
+}