See the best posts from any Bluesky account
Add DiscordWebhookService for firehose virality webhooks
Builds the Discord embed payload (username, title, URL, description,
estimated likes / threshold fields) and POSTs it with a 3-attempt
exponential backoff. On final failure throws DiscordWebhookError so the
caller can decide whether to log or swallow it. Injects fetch and sleep
so unit tests run offline.
Also exports atUriToBskyAppUrl, the at:// -> bsky.app conversion helper.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
+348
+137
app/services/discord_webhook.ts
+137
app/services/discord_webhook.ts
···
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/**
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* Discord webhook service — fires an embed for a firehose virality threshold
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* crossing.
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*
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* POSTs JSON to the configured webhook URL. Retries up to 3 times total with
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* exponential backoff (500ms, 1s). On final failure, throws
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* `DiscordWebhookError` so the caller can log / capture it.
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*
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* Both `fetch` and `sleep` are injected so the unit tests run deterministically
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* and don't touch the network.
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*/
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// ---------------------------------------------------------------------------
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// Types
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// ---------------------------------------------------------------------------
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export interface DiscordWebhookSendParams {
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webhookUrl: string
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subjectUri: string
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threshold: number
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estimatedCount: number
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authorHandle: string
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postText: string
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}
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export interface DiscordWebhookServiceDeps {
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fetchImpl?: typeof fetch
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sleep?: (ms: number) => Promise<void>
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}
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export class DiscordWebhookError extends Error {
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constructor(
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message: string,
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readonly attempts: number,
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readonly cause?: unknown
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) {
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super(message, { cause })
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this.name = 'DiscordWebhookError'
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}
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}
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// ---------------------------------------------------------------------------
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// Helpers
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// ---------------------------------------------------------------------------
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const BACKOFF_DELAYS_MS = [500, 1000, 2000]
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const DESCRIPTION_MAX_CHARS = 500
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/**
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* Convert an AT-URI of shape `at://{did}/app.bsky.feed.post/{rkey}` to the
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* corresponding bsky.app web URL.
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*/
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export function atUriToBskyAppUrl(atUri: string): string {
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const match = atUri.match(/^at:\/\/([^/]+)\/app\.bsky\.feed\.post\/(.+)$/)
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if (!match) {
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throw new Error(`atUriToBskyAppUrl: not a post AT-URI: ${atUri}`)
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}
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return `https://bsky.app/profile/${match[1]}/post/${match[2]}`
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}
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function formatNumber(n: number): string {
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return n.toLocaleString('en-US')
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}
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function truncate(text: string, maxChars: number): string {
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if (text.length <= maxChars) return text
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return text.slice(0, maxChars) + '…'
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}
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function buildPayload(params: DiscordWebhookSendParams): Record<string, unknown> {
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return {
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username: 'favs.blue firehose',
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embeds: [
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{
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author: { name: `@${params.authorHandle}` },
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title: `Post crossed ${formatNumber(params.threshold)} likes`,
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url: atUriToBskyAppUrl(params.subjectUri),
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description: truncate(params.postText, DESCRIPTION_MAX_CHARS),
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color: 3447003,
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timestamp: new Date().toISOString(),
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fields: [
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{ name: 'Estimated likes', value: formatNumber(params.estimatedCount), inline: true },
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{ name: 'Threshold', value: formatNumber(params.threshold), inline: true },
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],
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},
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],
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}
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}
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// ---------------------------------------------------------------------------
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// Service
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// ---------------------------------------------------------------------------
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export class DiscordWebhookService {
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readonly #fetch: typeof fetch
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readonly #sleep: (ms: number) => Promise<void>
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constructor(deps: DiscordWebhookServiceDeps = {}) {
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this.#fetch = deps.fetchImpl ?? globalThis.fetch.bind(globalThis)
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this.#sleep = deps.sleep ?? ((ms) => new Promise((r) => setTimeout(r, ms)))
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}
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/**
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* POST the Discord embed payload. Retries up to 3 total attempts on network
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* error or HTTP >= 400. Throws `DiscordWebhookError` if all attempts fail.
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*/
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async send(params: DiscordWebhookSendParams): Promise<void> {
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const payload = buildPayload(params)
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const body = JSON.stringify(payload)
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let lastError: unknown
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for (let attempt = 0; attempt < BACKOFF_DELAYS_MS.length; attempt++) {
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try {
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const response = await this.#fetch(params.webhookUrl, {
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method: 'POST',
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headers: { 'Content-Type': 'application/json' },
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body,
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})
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if (response.ok) return
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lastError = new Error(`Discord webhook returned HTTP ${response.status}`)
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} catch (err) {
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lastError = err
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}
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if (attempt < BACKOFF_DELAYS_MS.length - 1) {
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await this.#sleep(BACKOFF_DELAYS_MS[attempt])
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}
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}
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const detail = lastError instanceof Error ? lastError.message : String(lastError)
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throw new DiscordWebhookError(
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`Discord webhook failed after ${BACKOFF_DELAYS_MS.length} attempts: ${detail}`,
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BACKOFF_DELAYS_MS.length,
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lastError
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)
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}
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}
+211
tests/unit/services/discord_webhook.spec.ts
+211
tests/unit/services/discord_webhook.spec.ts
···
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/**
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* Unit tests for DiscordWebhookService.
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*
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* Fetch is injected as a fake so no network traffic occurs.
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*/
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import { test } from '@japa/runner'
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import {
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DiscordWebhookService,
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atUriToBskyAppUrl,
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DiscordWebhookError,
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} from '#services/discord_webhook'
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// ---------------------------------------------------------------------------
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// Helpers
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// ---------------------------------------------------------------------------
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type FetchCall = { url: string; body: unknown }
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function makeFakeFetch(responses: Array<{ ok: boolean; status: number } | Error>): {
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fn: typeof fetch
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calls: FetchCall[]
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} {
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const calls: FetchCall[] = []
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let idx = 0
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const fn = (async (url: string, init?: RequestInit) => {
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calls.push({
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url,
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body: init?.body ? JSON.parse(init.body as string) : undefined,
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})
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const response = responses[idx++]
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if (!response) throw new Error('Unexpected fetch call (no response queued)')
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if (response instanceof Error) throw response
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return {
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ok: response.ok,
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status: response.status,
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text: async () => '',
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}
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}) as unknown as typeof fetch
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return { fn, calls }
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}
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// ---------------------------------------------------------------------------
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// atUriToBskyAppUrl
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// ---------------------------------------------------------------------------
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test.group('atUriToBskyAppUrl', () => {
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test('converts AT-URI to bsky.app URL', ({ assert }) => {
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const uri = 'at://did:plc:abc123/app.bsky.feed.post/3k44xyz'
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assert.equal(atUriToBskyAppUrl(uri), 'https://bsky.app/profile/did:plc:abc123/post/3k44xyz')
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})
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test('throws on malformed URI', ({ assert }) => {
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assert.throws(() => atUriToBskyAppUrl('not-an-at-uri'))
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assert.throws(() => atUriToBskyAppUrl('at://did:plc:abc/app.bsky.feed.post/'))
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})
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})
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// ---------------------------------------------------------------------------
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// Payload shape
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// ---------------------------------------------------------------------------
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test.group('DiscordWebhookService payload shape', () => {
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test('builds the expected embed', async ({ assert }) => {
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const { fn, calls } = makeFakeFetch([{ ok: true, status: 204 }])
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const svc = new DiscordWebhookService({ fetchImpl: fn, sleep: () => Promise.resolve() })
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await svc.send({
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webhookUrl: 'https://discord.example/hook',
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subjectUri: 'at://did:plc:abc/app.bsky.feed.post/rkey1',
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threshold: 1000,
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estimatedCount: 1037,
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authorHandle: 'joe.bsky.social',
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postText: 'hello world',
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})
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assert.equal(calls.length, 1)
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assert.equal(calls[0].url, 'https://discord.example/hook')
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const body = calls[0].body as any
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assert.equal(body.username, 'favs.blue firehose')
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assert.equal(body.embeds.length, 1)
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const embed = body.embeds[0]
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assert.equal(embed.author.name, '@joe.bsky.social')
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assert.equal(embed.title, 'Post crossed 1,000 likes')
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assert.equal(embed.url, 'https://bsky.app/profile/did:plc:abc/post/rkey1')
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assert.equal(embed.description, 'hello world')
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assert.equal(embed.color, 3447003)
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assert.isString(embed.timestamp)
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assert.deepEqual(embed.fields, [
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{ name: 'Estimated likes', value: '1,037', inline: true },
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{ name: 'Threshold', value: '1,000', inline: true },
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])
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})
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test('truncates post text to ~500 chars with ellipsis', async ({ assert }) => {
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const { fn, calls } = makeFakeFetch([{ ok: true, status: 204 }])
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const svc = new DiscordWebhookService({ fetchImpl: fn, sleep: () => Promise.resolve() })
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const longText = 'a'.repeat(600)
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await svc.send({
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webhookUrl: 'https://discord.example/hook',
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subjectUri: 'at://did:plc:abc/app.bsky.feed.post/rkey1',
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threshold: 10000,
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estimatedCount: 12500,
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authorHandle: 'joe.bsky.social',
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postText: longText,
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})
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const body = calls[0].body as any
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const desc = body.embeds[0].description as string
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assert.isTrue(desc.length <= 501, `expected <=501 chars, got ${desc.length}`)
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assert.isTrue(desc.endsWith('…'))
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assert.equal(body.embeds[0].title, 'Post crossed 10,000 likes')
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assert.equal(body.embeds[0].fields[0].value, '12,500')
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assert.equal(body.embeds[0].fields[1].value, '10,000')
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})
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test('leaves short text untouched', async ({ assert }) => {
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const { fn, calls } = makeFakeFetch([{ ok: true, status: 204 }])
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const svc = new DiscordWebhookService({ fetchImpl: fn, sleep: () => Promise.resolve() })
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await svc.send({
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webhookUrl: 'https://discord.example/hook',
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subjectUri: 'at://did:plc:abc/app.bsky.feed.post/rkey1',
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threshold: 1000,
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estimatedCount: 1000,
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authorHandle: 'a.bsky.social',
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postText: 'short',
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})
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const body = calls[0].body as any
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assert.equal(body.embeds[0].description, 'short')
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})
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})
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// ---------------------------------------------------------------------------
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// Retry behavior
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// ---------------------------------------------------------------------------
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test.group('DiscordWebhookService retry', () => {
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test('retries on 500 and eventually succeeds', async ({ assert }) => {
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const { fn, calls } = makeFakeFetch([
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{ ok: false, status: 500 },
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{ ok: false, status: 502 },
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{ ok: true, status: 204 },
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])
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const sleepCalls: number[] = []
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const svc = new DiscordWebhookService({
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fetchImpl: fn,
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sleep: (ms) => {
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sleepCalls.push(ms)
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return Promise.resolve()
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},
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})
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await svc.send({
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webhookUrl: 'https://discord.example/hook',
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subjectUri: 'at://did:plc:abc/app.bsky.feed.post/rkey1',
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threshold: 1000,
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estimatedCount: 1000,
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authorHandle: 'a.bsky.social',
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postText: 'x',
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})
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assert.equal(calls.length, 3)
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// two backoff waits between three attempts
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assert.equal(sleepCalls.length, 2)
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assert.equal(sleepCalls[0], 500)
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assert.equal(sleepCalls[1], 1000)
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})
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test('retries on network error and throws DiscordWebhookError after 3 failures', async ({
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assert,
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}) => {
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const { fn, calls } = makeFakeFetch([
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new Error('ECONNRESET'),
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{ ok: false, status: 500 },
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{ ok: false, status: 503 },
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])
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const svc = new DiscordWebhookService({ fetchImpl: fn, sleep: () => Promise.resolve() })
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await assert.rejects(
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() =>
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svc.send({
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webhookUrl: 'https://discord.example/hook',
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subjectUri: 'at://did:plc:abc/app.bsky.feed.post/rkey1',
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threshold: 1000,
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estimatedCount: 1000,
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authorHandle: 'a.bsky.social',
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postText: 'x',
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}),
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DiscordWebhookError
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)
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assert.equal(calls.length, 3)
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})
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+
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test('does not retry on success', async ({ assert }) => {
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const { fn, calls } = makeFakeFetch([{ ok: true, status: 204 }])
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const svc = new DiscordWebhookService({ fetchImpl: fn, sleep: () => Promise.resolve() })
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+
200
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await svc.send({
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webhookUrl: 'https://discord.example/hook',
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subjectUri: 'at://did:plc:abc/app.bsky.feed.post/rkey1',
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threshold: 1000,
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estimatedCount: 1000,
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authorHandle: 'a.bsky.social',
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postText: 'x',
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})
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assert.equal(calls.length, 1)
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})
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})