add DeletionEvent (nostr-sdk#102)

Sources/NostrSDK/EventCreating.swift

@@ -110,6 +110,26 @@ public extension EventCreating {
         return try DirectMessageEvent(content: encryptedMessage, tags: [recipientTag], signedBy: keypair)
     }
 
+    /// Creates a ``DeletionEvent`` (kind 5) and signs it with the provided ``Keypair``.
+    /// - Parameters:
+    ///   - events: The events the signer would like to request deletion for.
+    ///   - keypair: The Keypair to sign with.
+    /// - Returns: The signed ``DeletionEvent``.
+    ///
+    /// > Important: Events can only be deleted using the same keypair that was used to create them.
+    /// See [NIP-09 Specification](https://github.com/nostr-protocol/nips/blob/master/09.md)
+    func delete(events: [NostrEvent], reason: String? = nil, signedBy keypair: Keypair) throws -> DeletionEvent {
+        // Verify that the events being deleted were created with the same keypair.
+        let creatorValidatedEvents = events.filter { $0.pubkey == keypair.publicKey.hex }
+
+        guard !creatorValidatedEvents.isEmpty else {
+            throw EventCreatingError.invalidInput
+        }
+
+        let tags = creatorValidatedEvents.map { Tag(name: .event, value: $0.id) }
+        return try DeletionEvent(content: reason ?? "", tags: tags, signedBy: keypair)
+    }
+
     /// Creates a ``TextNoteRepostEvent`` (kind 6) or ``GenericRepostEvent`` (kind 16) based on the kind of the event being reposted and signs it with the provided ``Keypair``.
     /// - Parameters:
     ///   - event: The event to repost.

Sources/NostrSDK/EventKind.swift

@@ -38,6 +38,14 @@ public enum EventKind: RawRepresentable, CaseIterable, Codable, Equatable {
     /// See [NIP-04 - Direct Messages](https://github.com/nostr-protocol/nips/blob/master/04.md)
     case directMessage
 
+    /// This kind of event indicates that the author requests that the events in the included
+    /// tags should be deleted.
+    /// > Note: This event can only *request* that the listed events be deleted. In reality, they
+    /// may not be deleted by all clients or relays.
+    ///
+    /// See [NIP-09 - Event Deletion](https://github.com/nostr-protocol/nips/blob/master/09.md)
+    case deletion
+
     /// This kind of note is used to signal to followers that another event is worth reading.
     ///
     /// > Note: The reposted event must be a kind 1 text note.
@@ -70,6 +78,7 @@ public enum EventKind: RawRepresentable, CaseIterable, Codable, Equatable {
         .recommendServer,
         .contactList,
         .directMessage,
+        .deletion,
         .repost,
         .reaction,
         .genericRepost,
@@ -88,6 +97,7 @@ public enum EventKind: RawRepresentable, CaseIterable, Codable, Equatable {
         case .recommendServer: return 2
         case .contactList: return 3
         case .directMessage: return 4
+        case .deletion: return 5
         case .repost: return 6
         case .reaction: return 7
         case .genericRepost: return 16

Sources/NostrSDK/Events/DeletionEvent.swift

@@ -0,0 +1,38 @@
+//
+//  DeletionEvent.swift
+//
+//
+//  Created by Bryan Montz on 10/29/23.
+//
+
+import Foundation
+
+/// An event that contains one or more references to other events that the 
+/// event creator would like to delete.
+///
+/// > Note: [NIP-09 Specification](https://github.com/nostr-protocol/nips/blob/master/09.md)
+public final class DeletionEvent: NostrEvent {
+
+    public required init(from decoder: Decoder) throws {
+        try super.init(from: decoder)
+    }
+
+    @available(*, unavailable, message: "This initializer is unavailable for this class.")
+    override init(kind: EventKind, content: String, tags: [Tag] = [], createdAt: Int64 = Int64(Date.now.timeIntervalSince1970), signedBy keypair: Keypair) throws {
+        try super.init(kind: kind, content: content, tags: tags, createdAt: createdAt, signedBy: keypair)
+    }
+
+    init(content: String, tags: [Tag] = [], createdAt: Int64 = Int64(Date.now.timeIntervalSince1970), signedBy keypair: Keypair) throws {
+        try super.init(kind: .deletion, content: content, tags: tags, createdAt: createdAt, signedBy: keypair)
+    }
+
+    /// The reason the creator of the event gave for deleting the included events.
+    public var reason: String {
+        content
+    }
+
+    /// The event ids that the creator requests deletion for.
+    public var deletedEventIds: [String] {
+        tags.filter { $0.name == .event }.map { $0.value }
+    }
+}

Tests/NostrSDKTests/EventCreatingTests.swift

@@ -121,7 +121,28 @@ final class EventCreatingTests: XCTestCase, EventCreating, EventVerifying, Fixtu
 
         try verifyEvent(event)
     }
+
+    func testDeletionEvent() throws {
+        let noteToDelete: TextNoteEvent = try decodeFixture(filename: "text_note_deletable")
+        let reason = "Didn't mean to post"
+
+        let event = try delete(events: [noteToDelete], reason: reason, signedBy: Keypair.test)
+
+        XCTAssertEqual(event.kind, .deletion)
+
+        XCTAssertEqual(event.reason, "Didn't mean to post")
+        XCTAssertEqual(event.deletedEventIds, ["fa5ed84fc8eeb959fd39ad8e48388cfc33075991ef8e50064cfcecfd918bb91b"])
+
+        try verifyEvent(event)
+    }
 
+    func testDeletionEventFailsWithMismatchedKey() throws {
+        let noteToDelete: TextNoteEvent = try decodeFixture(filename: "text_note")
+        let reason = "Didn't mean to post"
+
+        XCTAssertThrowsError(try delete(events: [noteToDelete], reason: reason, signedBy: Keypair.test))
+    }
+
     func testRepostTextNoteEvent() throws {
         let noteToRepost: TextNoteEvent = try decodeFixture(filename: "text_note")
 

Tests/NostrSDKTests/Fixtures/text_note_deletable.json

@@ -0,0 +1,18 @@
+{
+  "id": "fa5ed84fc8eeb959fd39ad8e48388cfc33075991ef8e50064cfcecfd918bb91b",
+  "pubkey": "9947f9659dd80c3682402b612f5447e28249997fb3709500c32a585eb0977340",
+  "created_at": 1682080184,
+  "kind": 1,
+  "tags": [
+    [
+      "e",
+      "93930d65435d49db723499335473920795e7f13c45600dcfad922135cf44bd63"
+    ],
+    [
+      "p",
+      "f8e6c64342f1e052480630e27e1016dce35fc3a614e60434fef4aa2503328ca9"
+    ]
+  ],
+  "content": "I think it stays persistent on your profile, but interface setting doesn’t persist. Bug.  ",
+  "sig": "96e6667348b2b1fc5f6e73e68fb1605f571ad044077dda62a35c15eb8290f2c4559935db461f8466df3dcf39bc2e11984c5344f65aabee4520dd6653d74cdc09"
+}