import {createServer} from "node:http"
import {createReadStream} from "node:fs"
import {readFile, stat} from "node:fs/promises"
import {dirname, extname, join, normalize} from "node:path"
import {fileURLToPath} from "node:url"

const __dirname = dirname(fileURLToPath(import.meta.url))
const buildDir = join(__dirname, "build")
const indexPath = join(buildDir, "index.html")
const indexHtml = await readFile(indexPath, "utf8").catch(error => {
  console.error("Unable to start server: build/index.html is missing. Run `pnpm run build` first.")

  throw error
})

const defaults = {
  title: readMetaContent(indexHtml, "og:title") || "Flotilla",
  description:
    readMetaContent(indexHtml, "og:description") ||
    readMetaContent(indexHtml, "description") ||
    "Flotilla is nostr - for communities.",
  url: readMetaContent(indexHtml, "og:url") || "",
  image: readMetaContent(indexHtml, "twitter:image") || "/maskable-icon-512x512.png",
}

const relayInfoCache = new Map()
const RELAY_CACHE_TTL_MS = 5 * 60 * 1000
const RELAY_TIMEOUT_MS = 1500

const MIME_TYPES = {
  ".css": "text/css; charset=utf-8",
  ".gif": "image/gif",
  ".html": "text/html; charset=utf-8",
  ".ico": "image/x-icon",
  ".jpg": "image/jpeg",
  ".jpeg": "image/jpeg",
  ".js": "text/javascript; charset=utf-8",
  ".json": "application/json; charset=utf-8",
  ".map": "application/json; charset=utf-8",
  ".mjs": "text/javascript; charset=utf-8",
  ".png": "image/png",
  ".svg": "image/svg+xml",
  ".txt": "text/plain; charset=utf-8",
  ".webmanifest": "application/manifest+json; charset=utf-8",
  ".woff": "font/woff",
  ".woff2": "font/woff2",
}

const server = createServer(async (req, res) => {
  try {
    const method = req.method || "GET"

    if (method !== "GET" && method !== "HEAD") {
      res.writeHead(405, {Allow: "GET, HEAD"})
      res.end()

      return
    }

    const origin = getRequestOrigin(req)
    const requestUrl = new URL(req.url || "/", origin)
    const headOnly = method === "HEAD"

    if (requestUrl.pathname === "/healthz") {
      sendText(res, "ok", "text/plain; charset=utf-8", headOnly)

      return
    }

    if (isJoinInvitePath(requestUrl.pathname)) {
      const html = await renderInvitePage(requestUrl, origin)
      sendText(res, html, "text/html; charset=utf-8", headOnly)

      return
    }

    const filePath = resolveStaticPath(requestUrl.pathname)

    if (filePath) {
      try {
        const fileInfo = await stat(filePath)

        if (fileInfo.isFile()) {
          sendFile(res, filePath, headOnly)

          return
        }
      } catch {
        // Fall through to SPA index fallback.
      }
    }

    sendText(res, indexHtml, "text/html; charset=utf-8", headOnly)
  } catch {
    res.writeHead(500, {"Content-Type": "text/plain; charset=utf-8"})
    res.end("Internal Server Error")
  }
})

const port = Number.parseInt(process.env.PORT || "3000", 10)
const host = process.env.HOST || "0.0.0.0"

server.listen(port, host, () => {
  console.log(`Flotilla server listening on http://${host}:${port}`)
})

function resolveStaticPath(pathname) {
  const decodedPath = decodeURIComponent(pathname)

  if (decodedPath.includes("\0")) {
    return undefined
  }

  const relativePath = decodedPath.replace(/^\/+/, "")
  const normalizedPath = normalize(relativePath)

  if (normalizedPath.startsWith("..")) {
    return undefined
  }

  return join(buildDir, normalizedPath)
}

function sendText(res, body, contentType, headOnly) {
  res.writeHead(200, {
    "Cache-Control": contentType.includes("text/html") ? "no-cache" : "public, max-age=60",
    "Content-Type": contentType,
  })

  if (headOnly) {
    res.end()

    return
  }

  res.end(body)
}

function sendFile(res, filePath, headOnly) {
  const extension = extname(filePath).toLowerCase()

  res.writeHead(200, {
    "Cache-Control": extension === ".html" ? "no-cache" : "public, max-age=31536000, immutable",
    "Content-Type": MIME_TYPES[extension] || "application/octet-stream",
  })

  if (headOnly) {
    res.end()

    return
  }

  const stream = createReadStream(filePath)

  stream.on("error", () => {
    if (!res.headersSent) {
      res.writeHead(500, {"Content-Type": "text/plain; charset=utf-8"})
      res.end("Internal Server Error")

      return
    }

    res.destroy()
  })

  stream.pipe(res)
}

function isJoinInvitePath(pathname) {
  return pathname === "/join" || pathname === "/join/"
}

async function renderInvitePage(requestUrl, origin) {
  const relayUrl = parseInviteRelay(requestUrl)

  if (!relayUrl) {
    return indexHtml
  }

  const relayInfo = await loadRelayInfo(relayUrl)
  const relayDisplay = getRelayDisplay(relayUrl)
  const platformName = defaults.title
  const image = toAbsoluteHttpUrl(defaults.image, origin) || `${origin}/maskable-icon-512x512.png`

  const title = relayInfo?.name
    ? `Invitation to join ${relayInfo.name} on ${platformName}`
    : `Invitation to join a ${platformName} space`

  const description = relayInfo?.description || `Join this ${platformName} space on ${relayDisplay}.`

  const meta = {
    card: "summary",
    description,
    image,
    site: defaults.url || origin,
    title,
    type: "website",
    url: requestUrl.href,
  }

  return setInviteMeta(indexHtml, meta)
}

function parseInviteRelay(requestUrl) {
  const relay = requestUrl.searchParams.get("r") || requestUrl.searchParams.get("relay")

  if (!relay) {
    return undefined
  }

  return normalizeInviteRelay(relay)
}

function normalizeInviteRelay(value) {
  const trimmed = value.trim()

  if (!trimmed) {
    return undefined
  }

  const hasProtocol = /^[a-zA-Z][a-zA-Z\d+.-]*:\/\//.test(trimmed)
  const normalized = hasProtocol ? trimmed : `wss://${trimmed}`

  try {
    const relayUrl = new URL(normalized)

    if (relayUrl.protocol === "http:") {
      relayUrl.protocol = "ws:"
    }

    if (relayUrl.protocol === "https:") {
      relayUrl.protocol = "wss:"
    }

    if (!["ws:", "wss:"].includes(relayUrl.protocol)) {
      return undefined
    }

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

    return relayUrl.href.replace(/\/$/, "")
  } catch {
    return undefined
  }
}

async function loadRelayInfo(relayUrl) {
  const now = Date.now()
  const cached = relayInfoCache.get(relayUrl)

  if (cached && cached.expiresAt > now) {
    return cached.value
  }

  const relayHttpUrl = toRelayHttpUrl(relayUrl)

  if (!relayHttpUrl) {
    return undefined
  }

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

  let relayInfo

  try {
    const response = await fetch(relayHttpUrl, {
      headers: {Accept: "application/nostr+json"},
      signal: controller.signal,
    })

    if (response.ok) {
      const json = await response.json()

      const name = typeof json.name === "string" ? json.name.trim() : ""
      const description = typeof json.description === "string" ? json.description.trim() : ""
      const icon = typeof json.icon === "string" ? toAbsoluteHttpUrl(json.icon, relayHttpUrl) : undefined

      relayInfo = {
        description: description || undefined,
        icon,
        name: name || undefined,
      }
    }
  } catch {
    relayInfo = undefined
  } finally {
    clearTimeout(timeout)
  }

  relayInfoCache.set(relayUrl, {
    expiresAt: now + RELAY_CACHE_TTL_MS,
    value: relayInfo,
  })

  return relayInfo
}

function toRelayHttpUrl(relayUrl) {
  if (relayUrl.startsWith("wss://")) {
    return `https://${relayUrl.slice(6)}`
  }

  if (relayUrl.startsWith("ws://")) {
    return `http://${relayUrl.slice(5)}`
  }

  return undefined
}

function getRelayDisplay(relayUrl) {
  const relayHttpUrl = toRelayHttpUrl(relayUrl)

  if (!relayHttpUrl) {
    return relayUrl
  }

  try {
    return new URL(relayHttpUrl).host
  } catch {
    return relayUrl
  }
}

function toAbsoluteHttpUrl(value, baseUrl) {
  try {
    const parsed = new URL(value, baseUrl)

    if (["http:", "https:"].includes(parsed.protocol)) {
      return parsed.href
    }

    return undefined
  } catch {
    return undefined
  }
}

function setInviteMeta(html, meta) {
  let result = html

  result = upsertMetaTag(result, "name", "description", meta.description)
  result = upsertMetaTag(result, "name", "og:url", meta.url)
  result = upsertMetaTag(result, "name", "og:type", meta.type)
  result = upsertMetaTag(result, "name", "og:title", meta.title)
  result = upsertMetaTag(result, "name", "og:description", meta.description)
  result = upsertMetaTag(result, "name", "twitter:card", meta.card)
  result = upsertMetaTag(result, "name", "twitter:site", meta.site)
  result = upsertMetaTag(result, "name", "twitter:title", meta.title)
  result = upsertMetaTag(result, "name", "twitter:description", meta.description)
  result = upsertMetaTag(result, "name", "twitter:image", meta.image)

  result = upsertMetaTag(result, "property", "og:url", meta.url)
  result = upsertMetaTag(result, "property", "og:type", meta.type)
  result = upsertMetaTag(result, "property", "og:title", meta.title)
  result = upsertMetaTag(result, "property", "og:description", meta.description)
  result = upsertMetaTag(result, "property", "og:image", meta.image)

  return result
}

function upsertMetaTag(html, attribute, key, value) {
  const escapedKey = escapeRegExp(key)
  const escapedValue = escapeHtml(value)
  const pattern = new RegExp(
    `(<meta\\s+[^>]*${attribute}=["']${escapedKey}["'][^>]*content=["'])[^"']*(["'][^>]*>)`,
    "i",
  )

  if (pattern.test(html)) {
    return html.replace(pattern, `$1${escapedValue}$2`)
  }

  return html.replace(
    "</head>",
    `    <meta ${attribute}="${escapeHtml(key)}" content="${escapedValue}" />\n  </head>`,
  )
}

function readMetaContent(html, key) {
  const escapedKey = escapeRegExp(key)
  const pattern = new RegExp(
    `<meta\\s+[^>]*(?:name|property)=["']${escapedKey}["'][^>]*content=["']([^"']*)["'][^>]*>`,
    "i",
  )

  const match = html.match(pattern)

  return match ? match[1] : undefined
}

function getRequestOrigin(req) {
  const forwardedProto = req.headers["x-forwarded-proto"]
  const forwardedHost = req.headers["x-forwarded-host"]

  const protocol = firstHeaderValue(forwardedProto) || "http"
  const host = firstHeaderValue(forwardedHost) || req.headers.host || "localhost"

  return `${protocol}://${host}`
}

function firstHeaderValue(value) {
  if (Array.isArray(value)) {
    return value[0]?.split(",")[0]?.trim()
  }

  if (typeof value === "string") {
    return value.split(",")[0].trim()
  }

  return undefined
}

function escapeRegExp(value) {
  return value.replace(/[.*+?^${}()|[\]\\]/g, "\\$&")
}

function escapeHtml(value) {
  return String(value)
    .replaceAll("&", "&amp;")
    .replaceAll("\"", "&quot;")
    .replaceAll("'", "&#39;")
    .replaceAll("<", "&lt;")
    .replaceAll(">", "&gt;")
}