Add NIP-25 utils

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],
+  }
+}