From 13e9b4aa3eefe1053df8d32953c68ce05f7677d2 Mon Sep 17 00:00:00 2001
From: futpib <futpib@gmail.com>
Date: Mon, 24 Apr 2023 00:50:13 +0400
Subject: [PATCH] Add NIP-25 utils

---
 index.ts      |   1 +
 nip25.test.js | 104 ++++++++++++++++++++++++++++++++++++++++++++++++++
 nip25.ts      |  68 +++++++++++++++++++++++++++++++++
 3 files changed, 173 insertions(+)
 create mode 100644 nip25.test.js
 create mode 100644 nip25.ts

diff --git a/index.ts b/index.ts
index c1f8047..2ca54ae 100644
--- a/index.ts
+++ b/index.ts
@@ -12,6 +12,7 @@ export * as nip10 from './nip10'
 export * as nip13 from './nip13'
 export * as nip19 from './nip19'
 export * as nip21 from './nip21'
+export * as nip25 from './nip25'
 export * as nip26 from './nip26'
 export * as nip27 from './nip27'
 export * as nip39 from './nip39'
diff --git a/nip25.test.js b/nip25.test.js
new file mode 100644
index 0000000..ffb5992
--- /dev/null
+++ b/nip25.test.js
@@ -0,0 +1,104 @@
+/* eslint-env jest */
+
+const {nip25, finishEvent, getPublicKey, Kind} = require('./lib/nostr.cjs')
+
+describe('finishReactionEvent + getReactedEventPointer', () => {
+  const privateKey =
+        'd217c1ff2f8a65c3e3a1740db3b9f58b8c848bb45e26d00ed4714e4a0f4ceecf'
+
+  const publicKey = getPublicKey(privateKey)
+
+  const reactedEvent = finishEvent({
+    kind: Kind.Text,
+    tags: [
+      ['e', 'replied event id'],
+      ['p', 'replied event pubkey'],
+    ],
+    content: 'Replied to a post',
+    created_at: 1617932115
+  }, privateKey)
+
+  it('should create a signed event from a minimal template', () => {
+    const template = {
+      created_at: 1617932115
+    }
+
+    const event = nip25.finishReactionEvent(template, reactedEvent, privateKey)
+
+    expect(event.kind).toEqual(Kind.Reaction)
+    expect(event.tags).toEqual([
+      [
+        'e',
+        'replied event id',
+      ],
+      [
+        'p',
+        'replied event pubkey',
+      ],
+      [
+        'e',
+        '0ecdbd4dba0652afb19e5f638257a41552a37995a4438ef63de658443f8d16b1',
+      ],
+      [
+        'p',
+        '6af0f9de588f2c53cedcba26c5e2402e0d0aa64ec7b47c9f8d97b5bc562bab5f',
+      ],
+    ])
+    expect(event.content).toEqual('+')
+    expect(event.created_at).toEqual(template.created_at)
+    expect(event.pubkey).toEqual(publicKey)
+    expect(typeof event.id).toEqual('string')
+    expect(typeof event.sig).toEqual('string')
+
+    const reactedEventPointer = nip25.getReactedEventPointer(event)
+
+    expect(reactedEventPointer.id).toEqual(reactedEvent.id)
+    expect(reactedEventPointer.author).toEqual(reactedEvent.pubkey)
+  })
+
+  it('should create a signed event from a filled template', () => {
+    const template = {
+      tags: [
+        ['nonstandard', 'tag'],
+      ],
+      content: '👍',
+      created_at: 1617932115
+    }
+
+    const event = nip25.finishReactionEvent(template, reactedEvent, privateKey)
+
+    expect(event.kind).toEqual(Kind.Reaction)
+    expect(event.tags).toEqual([
+      [
+        'nonstandard',
+        'tag',
+      ],
+      [
+        'e',
+        'replied event id',
+      ],
+      [
+        'p',
+        'replied event pubkey',
+      ],
+      [
+        'e',
+        '0ecdbd4dba0652afb19e5f638257a41552a37995a4438ef63de658443f8d16b1',
+      ],
+      [
+        'p',
+        '6af0f9de588f2c53cedcba26c5e2402e0d0aa64ec7b47c9f8d97b5bc562bab5f',
+      ],
+    ])
+    expect(event.content).toEqual('👍')
+    expect(event.created_at).toEqual(template.created_at)
+    expect(event.pubkey).toEqual(publicKey)
+    expect(typeof event.id).toEqual('string')
+    expect(typeof event.sig).toEqual('string')
+
+    const reactedEventPointer = nip25.getReactedEventPointer(event)
+
+    expect(reactedEventPointer.id).toEqual(reactedEvent.id)
+    expect(reactedEventPointer.author).toEqual(reactedEvent.pubkey)
+  })
+})
diff --git a/nip25.ts b/nip25.ts
new file mode 100644
index 0000000..6d8fad8
--- /dev/null
+++ b/nip25.ts
@@ -0,0 +1,68 @@
+import { Event, finishEvent, Kind } from './event'
+import { EventPointer } from './nip19'
+
+export type ReactionEventTemplate = {
+  /**
+   * Pass only non-nip25 tags if you have to. Nip25 tags ('e' and 'p' tags from reacted event) will be added automatically.
+   */
+  tags?: string[][]
+
+  /**
+   * @default '+'
+   */
+  content?: string
+
+  created_at: number
+}
+
+export function finishReactionEvent(
+  t: ReactionEventTemplate,
+  reacted: Event,
+  privateKey: string,
+): Event {
+  const inheritedTags = reacted.tags.filter(
+    (tag) => tag.length >= 2 && (tag[0] === 'e' || tag[0] === 'p'),
+  )
+
+  return finishEvent({
+    ...t,
+    kind: Kind.Reaction,
+    tags: [
+      ...(t.tags ?? []),
+      ...inheritedTags,
+      ['e', reacted.id],
+      ['p', reacted.pubkey],
+    ],
+    content: t.content ?? '+',
+  }, privateKey)
+}
+
+export function getReactedEventPointer(event: Event): undefined | EventPointer {
+  if (event.kind !== Kind.Reaction) {
+    return undefined
+  }
+
+  let lastETag: undefined | string[]
+  let lastPTag: undefined | string[]
+
+  for (let i = event.tags.length - 1; i >= 0 && (lastETag === undefined || lastPTag === undefined); i--) {
+    const tag = event.tags[i]
+    if (tag.length >= 2) {
+      if (tag[0] === 'e' && lastETag === undefined) {
+        lastETag = tag
+      } else if (tag[0] === 'p' && lastPTag === undefined) {
+        lastPTag = tag
+      }
+    }
+  }
+
+  if (lastETag === undefined || lastPTag === undefined) {
+    return undefined
+  }
+
+  return {
+    id: lastETag[1],
+    relays: [ lastETag[2], lastPTag[2] ].filter((x) => x !== undefined),
+    author: lastPTag[1],
+  }
+}