feat: polls (#451)

Co-authored-by: silberengel <silberengel7@protonmail.com>

src/services/poll-results.service.ts

@@ -0,0 +1,142 @@
+import { ExtendedKind } from '@/constants'
+import { getPollResponseFromEvent } from '@/lib/event-metadata'
+import dayjs from 'dayjs'
+import { Filter } from 'nostr-tools'
+import client from './client.service'
+
+export type TPollResults = {
+  totalVotes: number
+  results: Record<string, Set<string>>
+  voters: Set<string>
+  updatedAt: number
+}
+
+class PollResultsService {
+  static instance: PollResultsService
+  private pollResultsMap: Map<string, TPollResults> = new Map()
+  private pollResultsSubscribers = new Map<string, Set<() => void>>()
+
+  constructor() {
+    if (!PollResultsService.instance) {
+      PollResultsService.instance = this
+    }
+    return PollResultsService.instance
+  }
+
+  async fetchResults(
+    pollEventId: string,
+    relays: string[],
+    validPollOptionIds: string[],
+    isMultipleChoice: boolean,
+    endsAt?: number
+  ) {
+    const filter: Filter = {
+      kinds: [ExtendedKind.POLL_RESPONSE],
+      '#e': [pollEventId],
+      limit: 1000
+    }
+
+    if (endsAt) {
+      filter.until = endsAt
+    }
+
+    let results = this.pollResultsMap.get(pollEventId)
+    if (results) {
+      if (endsAt && results.updatedAt >= endsAt) {
+        return results
+      }
+      filter.since = results.updatedAt
+    } else {
+      results = {
+        totalVotes: 0,
+        results: validPollOptionIds.reduce(
+          (acc, optionId) => {
+            acc[optionId] = new Set<string>()
+            return acc
+          },
+          {} as Record<string, Set<string>>
+        ),
+        voters: new Set<string>(),
+        updatedAt: 0
+      }
+    }
+
+    const responseEvents = await client.fetchEvents(relays, {
+      kinds: [ExtendedKind.POLL_RESPONSE],
+      '#e': [pollEventId],
+      limit: 1000
+    })
+
+    results.updatedAt = dayjs().unix()
+
+    const responses = responseEvents
+      .map((evt) => getPollResponseFromEvent(evt, validPollOptionIds, isMultipleChoice))
+      .filter((response): response is NonNullable<typeof response> => response !== null)
+
+    responses
+      .sort((a, b) => b.created_at - a.created_at)
+      .forEach((response) => {
+        if (results && results.voters.has(response.pubkey)) return
+        results.voters.add(response.pubkey)
+
+        results.totalVotes += response.selectedOptionIds.length
+        response.selectedOptionIds.forEach((optionId) => {
+          if (results.results[optionId]) {
+            results.results[optionId].add(response.pubkey)
+          }
+        })
+      })
+
+    this.pollResultsMap.set(pollEventId, { ...results })
+    if (responseEvents.length) {
+      this.notifyPollResults(pollEventId)
+    }
+    return results
+  }
+
+  subscribePollResults(pollEventId: string, callback: () => void) {
+    let set = this.pollResultsSubscribers.get(pollEventId)
+    if (!set) {
+      set = new Set()
+      this.pollResultsSubscribers.set(pollEventId, set)
+    }
+    set.add(callback)
+    return () => {
+      set?.delete(callback)
+      if (set?.size === 0) this.pollResultsSubscribers.delete(pollEventId)
+    }
+  }
+
+  private notifyPollResults(pollEventId: string) {
+    const set = this.pollResultsSubscribers.get(pollEventId)
+    if (set) {
+      set.forEach((cb) => cb())
+    }
+  }
+
+  getPollResults(id: string): TPollResults | undefined {
+    return this.pollResultsMap.get(id)
+  }
+
+  addPollResponse(pollEventId: string, pubkey: string, selectedOptionIds: string[]) {
+    const results = this.pollResultsMap.get(pollEventId)
+    if (!results) return
+
+    if (results.voters.has(pubkey)) return
+
+    results.voters.add(pubkey)
+    results.totalVotes += selectedOptionIds.length
+    selectedOptionIds.forEach((optionId) => {
+      if (results.results[optionId]) {
+        results.results[optionId].add(pubkey)
+      }
+    })
+
+    this.pollResultsMap.set(pollEventId, { ...results })
+    this.notifyPollResults(pollEventId)
+  }
+}
+
+const instance = new PollResultsService()
+
+export default instance