Add polls

src/app/util/polls.ts

@@ -0,0 +1,76 @@
+import {now, removeUndefined, uniq} from "@welshman/lib"
+import type {TrustedEvent} from "@welshman/util"
+import {getTagValue, getTags, getTagValues} from "@welshman/util"
+
+export type PollType = "singlechoice" | "multiplechoice"
+
+export type PollOption = {
+  id: string
+  label: string
+  votes: number
+}
+
+export const getPollType = (event: TrustedEvent): PollType =>
+  getTagValue("polltype", event.tags) === "multiplechoice" ? "multiplechoice" : "singlechoice"
+
+export const getPollOptions = (event: TrustedEvent) =>
+  removeUndefined(
+    getTags("option", event.tags).map(tag => {
+      const [, id, label = id] = tag
+
+      if (!id) return undefined
+
+      return {id, label}
+    }),
+  )
+
+export const getPollEndsAt = (event: TrustedEvent) => {
+  const endsAt = getTagValue("endsAt", event.tags)
+
+  if (!endsAt) return undefined
+
+  const timestamp = parseInt(endsAt)
+
+  return Number.isNaN(timestamp) ? undefined : timestamp
+}
+
+export const isPollClosed = (event: TrustedEvent) => {
+  const endsAt = getPollEndsAt(event)
+
+  return typeof endsAt === "number" ? endsAt <= now() : false
+}
+
+export const getPollResponseSelections = (event: TrustedEvent, pollType = getPollType(event)) => {
+  const selections = getTagValues("response", event.tags)
+
+  return pollType === "singlechoice" ? selections.slice(0, 1) : uniq(selections)
+}
+
+export const getPollResults = (event: TrustedEvent, responses: TrustedEvent[]) => {
+  const options = getPollOptions(event).map(option => ({...option, votes: 0}))
+  const counts = new Map(options.map(option => [option.id, option]))
+  const latestByPubkey = new Map<string, TrustedEvent>()
+
+  for (const response of responses) {
+    const current = latestByPubkey.get(response.pubkey)
+
+    if (!current || response.created_at > current.created_at) {
+      latestByPubkey.set(response.pubkey, response)
+    }
+  }
+
+  for (const response of latestByPubkey.values()) {
+    for (const optionId of getPollResponseSelections(response, getPollType(event))) {
+      const option = counts.get(optionId)
+
+      if (option) {
+        option.votes += 1
+      }
+    }
+  }
+
+  return {
+    options,
+    voters: latestByPubkey.size,
+  }
+}