when (NimMajor, NimMinor) < (1, 4):
  {.push raises: [Defect].}
else:
  {.push raises: [].}

import
  std/[options, sequtils, random, sets],
  stew/results,
  chronicles,
  chronos,
  metrics,
  libp2p/protocols/protocol,
  libp2p/stream/connection,
  libp2p/crypto/crypto,
  eth/p2p/discoveryv5/enr
import
  ../common/nimchronos,
  ../waku_core,
  ./rpc

logScope:
  topics = "waku metadata"

const WakuMetadataCodec* = "/vac/waku/metadata/1.0.0"
const RpcResponseMaxBytes* = 1024

type
  WakuMetadata* = ref object of LPProtocol
    clusterId*: uint32
    shards*: HashSet[uint32]
    topicSubscriptionQueue: AsyncEventQueue[SubscriptionEvent]

proc respond(m: WakuMetadata, conn: Connection): Future[Result[void, string]] {.async, gcsafe.} =
  let response = WakuMetadataResponse(
    clusterId: some(m.clusterId),
    shards: toSeq(m.shards)
  )
  
  let res = catch: await conn.writeLP(response.encode().buffer)
  if res.isErr():
    return err(res.error.msg)

  return ok()

proc request*(m: WakuMetadata, conn: Connection): Future[Result[WakuMetadataResponse, string]] {.async, gcsafe.} =
  let request = WakuMetadataRequest(clusterId: some(m.clusterId), shards: toSeq(m.shards))

  let writeRes = catch: await conn.writeLP(request.encode().buffer)
  let readRes = catch: await conn.readLp(RpcResponseMaxBytes)
  
  # close no watter what
  let closeRes = catch: await conn.closeWithEof()
  if closeRes.isErr():
    return err("close failed: " & closeRes.error.msg)

  if writeRes.isErr():
    return err("write failed: " & writeRes.error.msg)

  let buffer = 
    if readRes.isErr():
      return err("read failed: " & readRes.error.msg)
    else: readRes.get()

  let response = WakuMetadataResponse.decode(buffer).valueOr:
    return err("decode failed: " & $error)

  return ok(response)

proc initProtocolHandler*(m: WakuMetadata) =
  proc handle(conn: Connection, proto: string) {.async, gcsafe, closure.} =
    let res = catch: await conn.readLp(RpcResponseMaxBytes)
    let buffer = res.valueOr:
      error "Connection reading error", error=error.msg
      return

    let response = WakuMetadataResponse.decode(buffer).valueOr:
      error "Response decoding error", error=error
      return

    debug "Received WakuMetadata request",
      remoteClusterId=response.clusterId,
      remoteShards=response.shards,
      localClusterId=m.clusterId,
      localShards=m.shards

    discard await m.respond(conn)

    # close, no data is expected
    await conn.closeWithEof()

  m.handler = handle
  m.codec = WakuMetadataCodec

proc new*(T: type WakuMetadata,
  clusterId: uint32,
  queue: AsyncEventQueue[SubscriptionEvent],
  ): T =
  let wm = WakuMetadata(clusterId: clusterId, topicSubscriptionQueue: queue)

  wm.initProtocolHandler()

  info "Created WakuMetadata protocol", clusterId=clusterId

  return wm

proc subscriptionsListener(wm: WakuMetadata) {.async.} =
  ## Listen for pubsub topics subscriptions changes
  
  let key = wm.topicSubscriptionQueue.register()

  while wm.started:
    let events = await wm.topicSubscriptionQueue.waitEvents(key)

    for event in events:
      let parsedTopic = NsPubsubTopic.parse(event.topic).valueOr:
        continue

      if parsedTopic.kind != NsPubsubTopicKind.StaticSharding:
        continue

      if parsedTopic.clusterId != wm.clusterId:
        continue

      case event.kind:
        of PubsubSub:
          wm.shards.incl(parsedTopic.shardId)
        of PubsubUnsub:
          wm.shards.excl(parsedTopic.shardId)
        else:
          continue
      
  wm.topicSubscriptionQueue.unregister(key)

proc start*(wm: WakuMetadata) =
  wm.started = true

  asyncSpawn wm.subscriptionsListener()

proc stop*(wm: WakuMetadata) =
  wm.started = false