WIP Verify and respond to zap requests

app/services/nostr_manager/verify_zap_request.rb

@@ -0,0 +1,51 @@
+module NostrManager
+  class VerifyZapRequest < NostrManagerService
+    def initialize(amount:, event:, lnurl: nil)
+      @amount, @event, @lnurl = amount, event, lnurl
+    end
+
+    # https://github.com/nostr-protocol/nips/blob/27fef638e2460139cc9078427a0aec0ce4470517/57.md#appendix-d-lnurl-server-zap-request-validation
+    def call
+      tags = parse_tags(@event.tags)
+
+      @event.verify_signature &&
+      @event.kind == 9734 &&
+      tags.present? &&
+      valid_p_tag?(tags[:p]) &&
+      valid_e_tag?(tags[:e]) &&
+      valid_a_tag?(tags[:a]) &&
+      valid_amount_tag?(tags[:amount]) &&
+      valid_lnurl_tag?(tags[:lnurl])
+    end
+
+    def valid_p_tag?(tag)
+      return false unless tag.present? && tag.length == 1
+      key = Nostr::PublicKey.new(tag.first) rescue nil
+      key.present?
+    end
+
+    def valid_e_tag?(tag)
+      return true unless tag.present?
+      # TODO validate format of event ID properly
+      tag.length == 1 && tag.first.is_a?(String)
+    end
+
+    def valid_a_tag?(tag)
+      return true unless tag.present?
+      # TODO validate format of event coordinate properly
+      tag.length == 1 && tag.first.is_a?(String)
+    end
+
+    def valid_amount_tag?(tag)
+      return true unless tag.present?
+      amount = tag.first
+      amount.is_a?(String) && amount.to_i == @amount
+    end
+
+    def valid_lnurl_tag?(tag)
+      return true unless tag.present?
+      # TODO validate lnurl matching recipient's lnurlp
+      tag.first.is_a?(String)
+    end
+  end
+end