Implement NIP-04: Encrypted Direct Messages

lib/nostr/events/encrypted_direct_message.rb

@@ -0,0 +1,53 @@
+# frozen_string_literal: true
+
+module Nostr
+  # Classes of event kinds.
+  module Events
+    # An event whose +content+ is encrypted. It can only be decrypted by the owner of the private key that pairs
+    # the event's +pubkey+.
+    class EncryptedDirectMessage < Event
+      # Instantiates a new encrypted direct message
+      #
+      # @api public
+      #
+      # @example Instantiating a new encrypted direct message
+      #   Nostr::Events::EncryptedDirectMessage.new(
+      #    sender_private_key: 'ccf9fdf3e1466d7c20969c71ec98defcf5f54aee088513e1b73ccb7bd770d460',
+      #    recipient_public_key: '48df4af6e240ac5f7c5de89bf5941b249880be0e87d03685b178ccb1a315f52e',
+      #    plain_text: 'Your feedback is appreciated, now pay $8',
+      # )
+      #
+      # @example Instantiating a new encrypted direct message that references a previous direct message
+      #   Nostr::Events::EncryptedDirectMessage.new(
+      #    sender_private_key: 'ccf9fdf3e1466d7c20969c71ec98defcf5f54aee088513e1b73ccb7bd770d460',
+      #    recipient_public_key: '48df4af6e240ac5f7c5de89bf5941b249880be0e87d03685b178ccb1a315f52e',
+      #    plain_text: 'Your feedback is appreciated, now pay $8',
+      #    previous_direct_message: 'ccf9fdf3e1466d7c20969c71ec98defcf5f54aee088513e1b73ccb7bd770d460'
+      # )
+      #
+      # @param plain_text [String] The +content+ of the encrypted message.
+      # @param sender_private_key [String] 32-bytes hex-encoded private key of the message's author.
+      # @param recipient_public_key [String] 32-bytes hex-encoded public key of the recipient of the encrypted message.
+      # @param previous_direct_message [String] 32-bytes hex-encoded id identifying the previous message in a
+      # conversation or a message we are explicitly replying to (such that contextual, more organized conversations
+      # may happen
+      #
+      def initialize(plain_text:, sender_private_key:, recipient_public_key:, previous_direct_message: nil)
+        crypto = Crypto.new
+        keygen = Keygen.new
+
+        encrypted_content = crypto.encrypt_text(sender_private_key, recipient_public_key, plain_text)
+        sender_public_key = keygen.extract_public_key(sender_private_key)
+
+        super(
+          pubkey: sender_public_key,
+          kind: Nostr::EventKind::ENCRYPTED_DIRECT_MESSAGE,
+          content: encrypted_content,
+          )
+
+        add_pubkey_reference(recipient_public_key)
+        add_event_reference(previous_direct_message) if previous_direct_message
+      end
+    end
+  end
+end