Extract event signing into its own class

lib/nostr.rb

@@ -1,5 +1,6 @@
 # frozen_string_literal: true
 
+require_relative 'nostr/crypto'
 require_relative 'nostr/version'
 require_relative 'nostr/keygen'
 require_relative 'nostr/client_message_type'

lib/nostr/crypto.rb

@@ -0,0 +1,48 @@
+# frozen_string_literal: true
+
+module Nostr
+  # Performs cryptographic operations on a +Nostr::Event+.
+  class Crypto
+    # Uses the private key to generate an event id and sign the event
+    #
+    # @api public
+    #
+    # @example Signing an event
+    #   crypto = Nostr::Crypto.new
+    #   crypto.sign(event, private_key)
+    #   event.id # => an id
+    #   event.sig # => a signature
+    #
+    # @param event [Event] The event to be signed
+    # @param private_key [String] 32-bytes hex-encoded private key.
+    #
+    # @return [Event] An unsigned event.
+    #
+    def sign_event(event, private_key)
+      event_digest = hash_event(event)
+
+      hex_private_key = Array(private_key).pack('H*')
+      hex_message     = Array(event_digest).pack('H*')
+      event_signature = Schnorr.sign(hex_message, hex_private_key).encode.unpack1('H*')
+
+      event.id = event_digest
+      event.sig = event_signature
+
+      event
+    end
+
+    private
+
+    # Generates a SHA256 hash of a +Nostr::Event+
+    #
+    # @api private
+    #
+    # @param event [Event] The event to be hashed
+    #
+    # @return [String] A SHA256 digest of the event
+    #
+    def hash_event(event)
+      Digest::SHA256.hexdigest(JSON.dump(event.serialize))
+    end
+  end
+end

lib/nostr/event.rb

@@ -70,9 +70,13 @@ module Nostr
     # @example Getting the event id
     #   event.id # => 'ccf9fdf3e1466d7c20969c71ec98defcf5f54aee088513e1b73ccb7bd770d460'
     #
+    # @example Setting the event id
+    #   event.id = 'ccf9fdf3e1466d7c20969c71ec98defcf5f54aee088513e1b73ccb7bd770d460'
+    #   event.id # => 'ccf9fdf3e1466d7c20969c71ec98defcf5f54aee088513e1b73ccb7bd770d460'
+    #
     # @return [String|nil]
     #
-    attr_reader :id
+    attr_accessor :id
 
     # 64-bytes signature of the sha256 hash of the serialized event data, which is
     # the same as the "id" field
@@ -82,9 +86,13 @@ module Nostr
     # @example Getting the event signature
     #   event.sig # => ''
     #
+    # @example Setting the event signature
+    #   event.sig = '058613f8d34c053294cc28b7f9e1f8f0e80fd1ac94fb20f2da6ca514e7360b39'
+    #   event.sig # => '058613f8d34c053294cc28b7f9e1f8f0e80fd1ac94fb20f2da6ca514e7360b39'
+    #
     # @return [String|nil]
     #
-    attr_reader :sig
+    attr_accessor :sig
 
     # Instantiates a new Event
     #
@@ -130,6 +138,22 @@ module Nostr
       @content = content
     end
 
+    # Signs an event with the user's private key
+    #
+    # @api public
+    #
+    # @example Signing an event
+    #   event.sign(private_key)
+    #
+    # @param private_key [String] 32-bytes hex-encoded private key.
+    #
+    # @return [Event] A signed event.
+    #
+    def sign(private_key)
+      crypto = Crypto.new
+      crypto.sign_event(self, private_key)
+    end
+
     # Serializes the event, to obtain a SHA256 digest of it
     #
     # @api public

lib/nostr/user.rb

@@ -57,36 +57,8 @@ module Nostr
     # @return [Event]
     #
     def create_event(event_attributes)
-      event_fragment = EventFragment.new(**event_attributes.merge(pubkey: keypair.public_key))
+      event = Event.new(**event_attributes.merge(pubkey: keypair.public_key))
-      event_sha256 = Digest::SHA256.hexdigest(JSON.dump(event_fragment.serialize))
+      event.sign(keypair.private_key)
-
-      signature = sign(event_sha256)
-
-      Event.new(
-        id: event_sha256,
-        pubkey: event_fragment.pubkey,
-        created_at: event_fragment.created_at,
-        kind: event_fragment.kind,
-        tags: event_fragment.tags,
-        content: event_fragment.content,
-        sig: signature
-      )
-    end
-
-    private
-
-    # Signs an event with the user's private key
-    #
-    # @api private
-    #
-    # @param event_sha256 [String] The SHA256 hash of the event.
-    #
-    # @return [String] The signature of the event.
-    #
-    def sign(event_sha256)
-      hex_private_key = Array(keypair.private_key).pack('H*')
-      hex_message = Array(event_sha256).pack('H*')
-      Schnorr.sign(hex_message, hex_private_key).encode.unpack1('H*')
     end
   end
 end

sig/nostr/crypto.rbs

@@ -0,0 +1,9 @@
+module Nostr
+  class Crypto
+    def sign_event: (Event, String) -> Event
+
+    private
+
+    def hash_event:(Event) -> String
+  end
+end

sig/nostr/event.rbs

@@ -5,8 +5,8 @@ module Nostr
     attr_reader kind: Integer
     attr_reader tags: Array[String]
     attr_reader content: String
-    attr_reader id: String?|nil
+    attr_accessor id: String?|nil
-    attr_reader sig: String?|nil
+    attr_accessor sig: String?|nil
 
     def initialize: (pubkey: String, kind: Integer, content: String, ?created_at: Integer, ?tags: Array[String], ?id: String|nil, ?sig: String|nil) -> void
     def serialize: -> [Integer, String, Integer, Integer, Array[String], String]
@@ -21,5 +21,7 @@ module Nostr
       sig: String?|nil
     }
     def ==: (Event other) -> bool
+
+    def sign:(String) -> Event
   end
 end

spec/nostr/crypto_spec.rb

@@ -0,0 +1,33 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Nostr::Crypto do
+  let(:crypto) { described_class.new }
+
+  describe '#sign_event' do
+    let(:keypair) do
+      Nostr::KeyPair.new(
+        public_key: '8a9d69c56e3c691bec8f9565e4dcbe38ae1d88fffeec3ce66b9f47558a3aa8ca',
+        private_key: '3185a47e3802f956ca5a2b4ea606c1d51c7610f239617e8f0f218d55bdf2b757'
+      )
+    end
+
+    let(:event) do
+      Nostr::Event.new(
+        kind: Nostr::EventKind::TEXT_NOTE,
+        content: 'Your feedback is appreciated, now pay $8',
+        pubkey: keypair.public_key
+      )
+    end
+
+    it 'signs an event' do
+      signed_event = crypto.sign_event(event, keypair.private_key)
+
+      aggregate_failures do
+        expect(signed_event.id.length).to eq(64)
+        expect(signed_event.sig.length).to eq(128)
+      end
+    end
+  end
+end

spec/nostr/event_spec.rb

@@ -121,6 +121,15 @@ RSpec.describe Nostr::Event do
     end
   end
 
+  describe '#id=' do
+    it 'sets the event id' do
+      new_id = '20f31a9b2a0ced48a167add9732ccade1dca5e34b44316e37da4af33bc8946a9'
+
+      event.id = new_id
+      expect(event.id).to eq(new_id)
+    end
+  end
+
   describe '#pubkey' do
     it 'exposes the event pubkey' do
       expect(event.pubkey).to eq('ccf9fdf3e1466d7c20969c71ec98defcf5f54aee088513e1b73ccb7bd770d460')
@@ -156,6 +165,41 @@ RSpec.describe Nostr::Event do
     end
   end
 
+  describe '#sig=' do
+    it 'sets the event signature' do
+      new_signature = '058613f8d34c053294cc28b7f9e1f8f0e80fd1ac94fb20f2da6ca514e7360b39' \
+                      '63d0086171f842ffebf1f7790ce147b4811a15ef3f59c76ec1324b970cc57ffe'
+
+      event.sig = new_signature
+      expect(event.sig).to eq(new_signature)
+    end
+  end
+
+  describe '#sign' do
+    let(:event) do
+      described_class.new(
+        pubkey: 'ccf9fdf3e1466d7c20969c71ec98defcf5f54aee088513e1b73ccb7bd770d460',
+        kind: Nostr::EventKind::TEXT_NOTE,
+        content: 'Your feedback is appreciated, now pay $8'
+      )
+    end
+    let(:keypair) do
+      Nostr::KeyPair.new(
+        public_key: '8a9d69c56e3c691bec8f9565e4dcbe38ae1d88fffeec3ce66b9f47558a3aa8ca',
+        private_key: '3185a47e3802f956ca5a2b4ea606c1d51c7610f239617e8f0f218d55bdf2b757'
+      )
+    end
+
+    it 'signs the event' do
+      event.sign(keypair.private_key)
+
+      aggregate_failures do
+        expect(event.id.length).to eq(64)
+        expect(event.sig.length).to eq(128)
+      end
+    end
+  end
+
   describe '#tags' do
     it 'exposes the event tags' do
       expect(event.tags).to eq(