flotilla/server.js

import path from "node:path"
import {promises as fs} from "node:fs"
import {fileURLToPath} from "node:url"

import {serve} from "@hono/node-server"
import {serveStatic} from "@hono/node-server/serve-static"
import {fetchRelay} from "@welshman/app"
import {displayRelayUrl, isRelayUrl, normalizeRelayUrl} from "@welshman/util"
import {load} from "cheerio"
import {Hono} from "hono"

const __filename = fileURLToPath(import.meta.url)
const __dirname = path.dirname(__filename)

const BUILD_DIR = path.join(__dirname, "build")
const INDEX_PATH = path.join(BUILD_DIR, "index.html")

const readPositiveInt = (value, fallback) => {
  const parsed = Number.parseInt(value || "", 10)

  return Number.isFinite(parsed) && parsed > 0 ? parsed : fallback
}

const PORT = readPositiveInt(process.env.PORT, 3000)
const HOST = process.env.HOST || "0.0.0.0"

const REQUEST_TIMEOUT_MS = readPositiveInt(process.env.INVITE_PREVIEW_TIMEOUT_MS, 1200)
const CACHE_MAX_ITEMS = readPositiveInt(process.env.INVITE_PREVIEW_CACHE_MAX, 500)
const POSITIVE_CACHE_TTL_MS = readPositiveInt(
  process.env.INVITE_PREVIEW_CACHE_TTL_MS,
  15 * 60 * 1000,
)
const NEGATIVE_CACHE_TTL_MS = readPositiveInt(
  process.env.INVITE_PREVIEW_NEGATIVE_CACHE_TTL_MS,
  2 * 60 * 1000,
)

const ALLOWED_METHODS = new Set(["GET", "HEAD"])
const DEFAULT_IMAGE_PATH = "/maskable-icon-512x512.png"
const HTML_HEADERS = {"Content-Type": "text/html; charset=utf-8"}

const truncate = (value, limit) => {
  if (value.length <= limit) {
    return value
  }

  if (limit <= 3) {
    return value.slice(0, limit)
  }

  return `${value.slice(0, limit - 3)}...`
}

const sanitizeText = (value, limit) => {
  if (typeof value !== "string") {
    return undefined
  }

  const compact = value.replace(/\s+/g, " ").trim()

  if (!compact) {
    return undefined
  }

  return truncate(compact, limit)
}

const isRecord = value => Boolean(value) && typeof value === "object" && !Array.isArray(value)

const hasMetadata = metadata => Object.keys(metadata).length > 0

const firstHeaderValue = value => {
  if (typeof value !== "string") {
    return undefined
  }

  return sanitizeText(value.split(",")[0], 256)
}

const requestUrlFromContext = context => {
  const requestUrl = new URL(context.req.url)
  const forwardedProto = firstHeaderValue(context.req.header("x-forwarded-proto"))
  const forwardedHost = firstHeaderValue(context.req.header("x-forwarded-host"))

  try {
    if (forwardedProto === "http" || forwardedProto === "https") {
      requestUrl.protocol = `${forwardedProto}:`
    }

    if (forwardedHost) {
      requestUrl.host = forwardedHost
    }
  } catch {
    return requestUrl
  }

  return requestUrl
}

const absoluteUrlFromRequest = (requestUrl, value) => {
  try {
    return new URL(value, requestUrl.origin).toString()
  } catch {
    return value
  }
}

const normalizeImageUrl = (value, baseUrl) => {
  if (typeof value !== "string") {
    return undefined
  }

  const trimmed = value.trim()

  if (!trimmed) {
    return undefined
  }

  try {
    const imageUrl = new URL(trimmed, baseUrl)

    if (!["http:", "https:"].includes(imageUrl.protocol)) {
      return undefined
    }

    return imageUrl.toString()
  } catch {
    return undefined
  }
}

const normalizeRelayInput = value => {
  const trimmed = value.trim()

  if (!trimmed) {
    return undefined
  }

  let relayInput = trimmed

  try {
    const parsed = new URL(trimmed)

    if (parsed.protocol === "http:") {
      parsed.protocol = "ws:"
      relayInput = parsed.toString()
    }

    if (parsed.protocol === "https:") {
      parsed.protocol = "wss:"
      relayInput = parsed.toString()
    }
  } catch {
    relayInput = trimmed
  }

  if (!isRelayUrl(relayInput)) {
    return undefined
  }

  try {
    const relayUrl = new URL(normalizeRelayUrl(relayInput))

    relayUrl.hash = ""
    relayUrl.search = ""

    return relayUrl.toString()
  } catch {
    return undefined
  }
}

const relayToInfoUrl = relayUrl => {
  try {
    const relayHttpUrl = new URL(relayUrl)

    if (relayHttpUrl.protocol === "ws:") {
      relayHttpUrl.protocol = "http:"
    } else if (relayHttpUrl.protocol === "wss:") {
      relayHttpUrl.protocol = "https:"
    } else {
      return undefined
    }

    relayHttpUrl.hash = ""
    relayHttpUrl.search = ""

    return relayHttpUrl.toString()
  } catch {
    return undefined
  }
}

const withTimeout = async (promise, timeoutMs) =>
  new Promise(resolve => {
    if (timeoutMs <= 0) {
      resolve(undefined)
      return
    }

    const timeout = setTimeout(() => resolve(undefined), timeoutMs)

    promise
      .then(resolve)
      .catch(() => resolve(undefined))
      .finally(() => clearTimeout(timeout))
  })

const findMeta = ($, key) => {
  const normalizedKey = key.toLowerCase()

  return $("meta")
    .filter((_, element) => {
      const meta = $(element)
      const name = meta.attr("name")?.toLowerCase()
      const property = meta.attr("property")?.toLowerCase()

      return name === normalizedKey || property === normalizedKey
    })
    .first()
}

const readMetaContent = ($, key) => findMeta($, key).attr("content")

const readIconHref = $ => {
  let href

  $("link[rel]").each((_, element) => {
    if (href) {
      return
    }

    const link = $(element)
    const rel = link.attr("rel")?.toLowerCase() || ""

    if (rel.includes("icon")) {
      href = link.attr("href")
    }
  })

  return href
}

const findLinkRel = ($, rel) =>
  $("link[rel]")
    .filter((_, element) => ($(element).attr("rel")?.toLowerCase() || "").includes(rel))
    .first()

const extractHtmlMetadata = (html, baseUrl) => {
  const $ = load(html)
  const name = sanitizeText($("title").first().text(), 80)
  const description = sanitizeText(readMetaContent($, "description") || "", 180)
  const icon = normalizeImageUrl(
    readMetaContent($, "og:image") || readMetaContent($, "twitter:image") || readIconHref($) || "",
    baseUrl,
  )

  return {
    ...(name ? {name} : {}),
    ...(description ? {description} : {}),
    ...(icon ? {icon} : {}),
  }
}

const normalizeRelayMetadata = (relayMetadata, relayUrl) => {
  if (!isRecord(relayMetadata)) {
    return {}
  }

  const infoUrl = relayToInfoUrl(relayUrl) || relayUrl
  const name = sanitizeText(relayMetadata.name || relayMetadata.title, 80)
  const description = sanitizeText(relayMetadata.description, 180)
  const icon = normalizeImageUrl(
    relayMetadata.icon || relayMetadata.picture || relayMetadata.image,
    infoUrl,
  )

  return {
    ...(name ? {name} : {}),
    ...(description ? {description} : {}),
    ...(icon ? {icon} : {}),
  }
}

const fetchHtmlRelayMetadata = async (relayUrl, timeoutMs) => {
  const infoUrl = relayToInfoUrl(relayUrl)

  if (!infoUrl || timeoutMs <= 0) {
    return {}
  }

  const controller = new AbortController()
  const timeout = setTimeout(() => controller.abort(), timeoutMs)

  try {
    const response = await fetch(infoUrl, {
      headers: {
        Accept: "text/html, application/xhtml+xml, */*;q=0.1",
      },
      redirect: "follow",
      signal: controller.signal,
    })

    if (!response.ok) {
      return {}
    }

    return extractHtmlMetadata(await response.text(), infoUrl)
  } catch {
    return {}
  } finally {
    clearTimeout(timeout)
  }
}

const cacheByRelay = new Map()
const inFlightByRelay = new Map()

const getCachedRelayData = relayUrl => {
  const cached = cacheByRelay.get(relayUrl)

  if (cached === undefined) {
    return undefined
  }

  if (cached.expiresAt <= Date.now()) {
    cacheByRelay.delete(relayUrl)
    return undefined
  }

  cacheByRelay.delete(relayUrl)
  cacheByRelay.set(relayUrl, cached)

  return cached.value
}

const setCachedRelayData = (relayUrl, value, ttlMs) => {
  if (cacheByRelay.size >= CACHE_MAX_ITEMS) {
    const oldestKey = cacheByRelay.keys().next().value

    if (oldestKey !== undefined) {
      cacheByRelay.delete(oldestKey)
    }
  }

  cacheByRelay.set(relayUrl, {
    expiresAt: Date.now() + ttlMs,
    value,
  })
}

const fetchRelayMetadata = async relayUrl => {
  const cached = getCachedRelayData(relayUrl)

  if (cached !== undefined) {
    return cached
  }

  const inFlight = inFlightByRelay.get(relayUrl)

  if (inFlight !== undefined) {
    return inFlight
  }

  const loader = (async () => {
    const deadline = Date.now() + REQUEST_TIMEOUT_MS
    const remainingTimeout = () => Math.max(0, deadline - Date.now())
    const relay = await withTimeout(fetchRelay(relayUrl), remainingTimeout())
    let metadata = normalizeRelayMetadata(relay, relayUrl)

    if (!hasMetadata(metadata)) {
      metadata = await fetchHtmlRelayMetadata(relayUrl, remainingTimeout())
    }

    setCachedRelayData(
      relayUrl,
      metadata,
      hasMetadata(metadata) ? POSITIVE_CACHE_TTL_MS : NEGATIVE_CACHE_TTL_MS,
    )

    return metadata
  })()

  inFlightByRelay.set(relayUrl, loader)

  try {
    return await loader
  } finally {
    inFlightByRelay.delete(relayUrl)
  }
}

const isJoinInvitePath = pathname => pathname === "/join" || pathname === "/join/"

const parseInvite = requestUrl => {
  const relayParam = requestUrl.searchParams.get("r") || ""
  const relayUrl = normalizeRelayInput(relayParam)

  if (!relayUrl) {
    return undefined
  }

  const claim = sanitizeText(requestUrl.searchParams.get("c") || "", 256) || ""

  return {relayUrl, claim}
}

const loadIndexTemplate = async () => {
  try {
    return await fs.readFile(INDEX_PATH, "utf8")
  } catch (error) {
    console.error(`Unable to read ${INDEX_PATH}. Run \"pnpm run build\" first.`)
    throw error
  }
}

const INDEX_TEMPLATE = await loadIndexTemplate()
const INDEX_DOCUMENT = load(INDEX_TEMPLATE)
const DEFAULT_PLATFORM_NAME =
  sanitizeText(process.env.VITE_PLATFORM_NAME, 80) ||
  sanitizeText(readMetaContent(INDEX_DOCUMENT, "og:title"), 80) ||
  sanitizeText(readMetaContent(INDEX_DOCUMENT, "twitter:title"), 80) ||
  "Flotilla"
const DEFAULT_PLATFORM_DESCRIPTION =
  sanitizeText(process.env.VITE_PLATFORM_DESCRIPTION, 180) ||
  sanitizeText(readMetaContent(INDEX_DOCUMENT, "description"), 180) ||
  "Flotilla is nostr - for communities."

const buildInviteDescription = ({spaceName, relayDisplay, relayDescription}) => {
  const parts = []

  if (spaceName) {
    parts.push(`You are invited to join ${spaceName} on ${DEFAULT_PLATFORM_NAME}.`)
  } else {
    parts.push(`You are invited to join a space on ${DEFAULT_PLATFORM_NAME}.`)
  }

  if (relayDisplay) {
    parts.push(`Relay: ${relayDisplay}.`)
  }

  if (relayDescription) {
    parts.push(relayDescription)
  } else {
    parts.push(DEFAULT_PLATFORM_DESCRIPTION)
  }

  return sanitizeText(parts.join(" "), 220) || DEFAULT_PLATFORM_DESCRIPTION
}

const buildInviteMeta = (requestUrl, invite, relayMetadata) => {
  const relayDisplay = displayRelayUrl(invite.relayUrl)
  const spaceName = sanitizeText(relayMetadata.name, 80)
  const relayDescription = sanitizeText(relayMetadata.description, 180)
  const title = spaceName
    ? `Invite to ${spaceName} on ${DEFAULT_PLATFORM_NAME}`
    : `Invite to a Space on ${DEFAULT_PLATFORM_NAME}`
  const description = buildInviteDescription({spaceName, relayDisplay, relayDescription})
  const image = relayMetadata.icon || absoluteUrlFromRequest(requestUrl, DEFAULT_IMAGE_PATH)
  const url = requestUrl.toString()
  const site = requestUrl.origin

  return {title, description, image, url, site}
}

const ensureHead = $ => {
  const existingHead = $("head").first()

  if (existingHead.length > 0) {
    return existingHead
  }

  $("html").prepend("<head></head>")

  return $("head").first()
}

const upsertTitle = ($, title) => {
  const head = ensureHead($)
  let titleTag = head.children("title").first()

  if (titleTag.length === 0) {
    titleTag = $("<title></title>")
    head.prepend(titleTag)
  }

  titleTag.text(title)
}

const upsertMetaTag = ($, key, content, attribute) => {
  const head = ensureHead($)
  let tag = findMeta($, key)

  if (tag.length === 0) {
    tag = $("<meta>")
    head.append(tag)
  }

  tag.removeAttr(attribute === "name" ? "property" : "name")
  tag.attr(attribute, key)
  tag.attr("content", content)
}

const upsertCanonical = ($, href) => {
  const head = ensureHead($)
  let tag = findLinkRel($, "canonical")

  if (tag.length === 0) {
    tag = $("<link>")
    head.append(tag)
  }

  tag.attr("rel", "canonical")
  tag.attr("href", href)
}

const injectInviteMeta = (html, metadata) => {
  const $ = load(html)

  upsertTitle($, metadata.title)
  upsertCanonical($, metadata.url)
  upsertMetaTag($, "description", metadata.description, "name")
  upsertMetaTag($, "og:type", "website", "property")
  upsertMetaTag($, "og:url", metadata.url, "property")
  upsertMetaTag($, "og:title", metadata.title, "property")
  upsertMetaTag($, "og:description", metadata.description, "property")
  upsertMetaTag($, "og:image", metadata.image, "property")
  upsertMetaTag($, "twitter:card", "summary_large_image", "name")
  upsertMetaTag($, "twitter:site", metadata.site, "name")
  upsertMetaTag($, "twitter:url", metadata.url, "name")
  upsertMetaTag($, "twitter:title", metadata.title, "name")
  upsertMetaTag($, "twitter:description", metadata.description, "name")
  upsertMetaTag($, "twitter:image", metadata.image, "name")

  return $.html()
}

const renderIndex = async requestUrl => {
  if (!isJoinInvitePath(requestUrl.pathname)) {
    return INDEX_TEMPLATE
  }

  const invite = parseInvite(requestUrl)

  if (!invite) {
    return INDEX_TEMPLATE
  }

  const relayMetadata = await fetchRelayMetadata(invite.relayUrl)
  const inviteMeta = buildInviteMeta(requestUrl, invite, relayMetadata)

  return injectInviteMeta(INDEX_TEMPLATE, inviteMeta)
}

const isImmutableAsset = filePath => filePath.split(path.sep).join("/").includes("/_app/immutable/")

const getStaticCacheControl = filePath =>
  path.basename(filePath) === "index.html"
    ? "no-cache"
    : isImmutableAsset(filePath)
      ? "public, max-age=31536000, immutable"
      : "public, max-age=3600"

const respondHtml = (html, isHeadRequest, cacheControl) =>
  new Response(isHeadRequest ? undefined : html, {
    headers: {
      ...HTML_HEADERS,
      "Cache-Control": cacheControl,
    },
    status: 200,
  })

const app = new Hono()

app.use("*", async (context, next) => {
  if (!ALLOWED_METHODS.has(context.req.method)) {
    return context.text("Method Not Allowed", 405, {Allow: "GET, HEAD"})
  }

  await next()
})

app.use(
  "*",
  serveStatic({
    root: BUILD_DIR,
    onFound: (filePath, context) => {
      context.header("Cache-Control", getStaticCacheControl(filePath))
    },
  }),
)

app.on(["GET", "HEAD"], "*", async context => {
  const requestUrl = requestUrlFromContext(context)

  if (path.extname(requestUrl.pathname)) {
    return context.text("Not found", 404)
  }

  const dynamicInvite = isJoinInvitePath(requestUrl.pathname) && requestUrl.searchParams.has("r")
  const html = await renderIndex(requestUrl)

  return respondHtml(html, context.req.method === "HEAD", dynamicInvite ? "no-store" : "no-cache")
})

serve(
  {
    fetch: app.fetch,
    hostname: HOST,
    port: PORT,
  },
  () => {
    console.log(`Flotilla server running on http://${HOST}:${PORT}`)
  },
)