# nimbus_verified_proxy
# Copyright (c) 2022-2023 Status Research & Development GmbH
# Licensed and distributed under either of
#   * MIT license (license terms in the root directory or at https://opensource.org/licenses/MIT).
#   * Apache v2 license (license terms in the root directory or at https://www.apache.org/licenses/LICENSE-2.0).
# at your option. This file may not be copied, modified, or distributed except according to those terms.

{.push raises: [].}

import
  std/[strutils, typetraits],
  stint,
  stew/[byteutils, results],
  chronicles,
  json_rpc/[rpcproxy, rpcserver, rpcclient],
  eth/common/eth_types as etypes,
  web3,
  web3/[primitives, eth_api_types],
  beacon_chain/el/el_manager,
  beacon_chain/networking/network_metadata,
  beacon_chain/spec/forks,
  ./rpc_utils,
  ../validate_proof,
  ../block_cache

export forks

logScope:
  topics = "verified_proxy"

proc `==`(x, y: Quantity): bool {.borrow, noSideEffect.}

type
  VerifiedRpcProxy* = ref object
    proxy: RpcProxy
    blockCache: BlockCache
    chainId: Quantity

  QuantityTagKind = enum
    LatestBlock, BlockNumber

  BlockTag = eth_api_types.RtBlockIdentifier

  QuantityTag = object
    case kind: QuantityTagKind
    of LatestBlock:
      discard
    of BlockNumber:
      blockNumber: Quantity

func parseQuantityTag(blockTag: BlockTag): Result[QuantityTag, string] =
  if blockTag.kind == bidAlias:
    let tag = blockTag.alias.toLowerAscii
    case tag
    of "latest":
      return ok(QuantityTag(kind: LatestBlock))
    else:
      return err("Unsupported blockTag: " & tag)
  else:
    let quantity = blockTag.number.Quantity
    return ok(QuantityTag(kind: BlockNumber, blockNumber: quantity))

template checkPreconditions(proxy: VerifiedRpcProxy) =
  if proxy.blockCache.isEmpty():
    raise newException(ValueError, "Syncing")

template rpcClient(lcProxy: VerifiedRpcProxy): RpcClient =
  lcProxy.proxy.getClient()

proc getPayloadByTag(
    proxy: VerifiedRpcProxy,
    quantityTag: BlockTag):
    results.Opt[ExecutionData] {.raises: [ValueError].} =
  checkPreconditions(proxy)

  let tagResult = parseQuantityTag(quantityTag)

  if tagResult.isErr:
    raise newException(ValueError, tagResult.error)

  let tag = tagResult.get()

  case tag.kind
  of LatestBlock:
    # this will always return some block, as we always checkPreconditions
    return proxy.blockCache.latest
  of BlockNumber:
    return proxy.blockCache.getByNumber(tag.blockNumber)

proc getPayloadByTagOrThrow(
    proxy: VerifiedRpcProxy,
    quantityTag: BlockTag): ExecutionData {.raises: [ValueError].} =

  let tagResult = getPayloadByTag(proxy, quantityTag)

  if tagResult.isErr:
    raise newException(ValueError, "No block stored for given tag " & $quantityTag)

  return tagResult.get()

proc installEthApiHandlers*(lcProxy: VerifiedRpcProxy) =
  lcProxy.proxy.rpc("eth_chainId") do() -> Quantity:
    return lcProxy.chainId

  lcProxy.proxy.rpc("eth_blockNumber") do() -> Quantity:
    ## Returns the number of the most recent block.
    checkPreconditions(lcProxy)

    return lcProxy.blockCache.latest.get.blockNumber

  lcProxy.proxy.rpc("eth_getBalance") do(
      address: Address, quantityTag: BlockTag) -> UInt256:
    # When requesting state for `latest` block number, we need to translate
    # `latest` to actual block number as `latest` on proxy and on data provider
    # can mean different blocks and ultimatly piece received piece of state
    # must by validated against correct state root
    let
      executionPayload = lcProxy.getPayloadByTagOrThrow(quantityTag)
      blockNumber = executionPayload.blockNumber.uint64

    info "Forwarding eth_getBalance call", blockNumber

    let proof = await lcProxy.rpcClient.eth_getProof(
      address, @[], blockId(blockNumber))

    let accountResult = getAccountFromProof(
      executionPayload.stateRoot,
      proof.address,
      proof.balance,
      proof.nonce,
      proof.codeHash,
      proof.storageHash,
      proof.accountProof
    )

    if accountResult.isOk():
      return accountResult.get.balance
    else:
      raise newException(ValueError, accountResult.error)

  lcProxy.proxy.rpc("eth_getStorageAt") do(
      address: Address, slot: UInt256, quantityTag: BlockTag) -> UInt256:
    let
      executionPayload = lcProxy.getPayloadByTagOrThrow(quantityTag)
      blockNumber = executionPayload.blockNumber.uint64

    info "Forwarding eth_getStorageAt", blockNumber

    let proof = await lcProxy.rpcClient.eth_getProof(
      address, @[slot], blockId(blockNumber))

    let dataResult = getStorageData(executionPayload.stateRoot, slot, proof)

    if dataResult.isOk():
      let slotValue = dataResult.get()
      return slotValue
    else:
      raise newException(ValueError, dataResult.error)

  lcProxy.proxy.rpc("eth_getTransactionCount") do(
      address: Address, quantityTag: BlockTag) -> Quantity:
    let
      executionPayload = lcProxy.getPayloadByTagOrThrow(quantityTag)
      blockNumber = executionPayload.blockNumber.uint64

    info "Forwarding eth_getTransactionCount", blockNumber

    let proof = await lcProxy.rpcClient.eth_getProof(
      address, @[], blockId(blockNumber))

    let accountResult = getAccountFromProof(
      executionPayload.stateRoot,
      proof.address,
      proof.balance,
      proof.nonce,
      proof.codeHash,
      proof.storageHash,
      proof.accountProof
    )

    if accountResult.isOk():
      return Quantity(accountResult.get.nonce)
    else:
      raise newException(ValueError, accountResult.error)

  lcProxy.proxy.rpc("eth_getCode") do(
      address: Address, quantityTag: BlockTag) -> seq[byte]:
    let
      executionPayload = lcProxy.getPayloadByTagOrThrow(quantityTag)
      blockNumber = executionPayload.blockNumber.uint64

    let
      proof = await lcProxy.rpcClient.eth_getProof(
        address, @[], blockId(blockNumber))
      accountResult = getAccountFromProof(
        executionPayload.stateRoot,
        proof.address,
        proof.balance,
        proof.nonce,
        proof.codeHash,
        proof.storageHash,
        proof.accountProof
      )

    if accountResult.isErr():
      raise newException(ValueError, accountResult.error)

    let account = accountResult.get()

    if account.codeHash == etypes.EMPTY_CODE_HASH:
      # account does not have any code, return empty hex data
      return @[]

    info "Forwarding eth_getCode", blockNumber

    let code = await lcProxy.rpcClient.eth_getCode(
      address,
      blockId(blockNumber)
    )

    if isValidCode(account, code):
      return code
    else:
      raise newException(ValueError,
        "Received code which does not match the account code hash")

  # TODO:
  # Following methods are forwarded directly to the web3 provider and therefore
  # are not validated in any way.
  lcProxy.proxy.registerProxyMethod("net_version")
  lcProxy.proxy.registerProxyMethod("eth_call")
  lcProxy.proxy.registerProxyMethod("eth_sendRawTransaction")
  lcProxy.proxy.registerProxyMethod("eth_getTransactionReceipt")

  # TODO currently we do not handle fullTransactions flag. It require updates on
  # nim-web3 side
  lcProxy.proxy.rpc("eth_getBlockByNumber") do(
      quantityTag: BlockTag, fullTransactions: bool) -> Option[BlockObject]:
    let executionPayload = lcProxy.getPayloadByTag(quantityTag)

    if executionPayload.isErr:
      return none(BlockObject)

    return some(asBlockObject(executionPayload.get()))

  lcProxy.proxy.rpc("eth_getBlockByHash") do(
      blockHash: BlockHash, fullTransactions: bool) -> Option[BlockObject]:
    let executionPayload = lcProxy.blockCache.getPayloadByHash(blockHash)

    if executionPayload.isErr:
      return none(BlockObject)

    return some(asBlockObject(executionPayload.get()))

proc new*(
    T: type VerifiedRpcProxy,
    proxy: RpcProxy,
    blockCache: BlockCache,
    chainId: Quantity): T =
  VerifiedRpcProxy(
    proxy: proxy,
    blockCache: blockCache,
    chainId: chainId)

# Used to be in eth1_monitor.nim; not sure why it was deleted,
# so I copied it here. --Adam
template awaitWithRetries*[T](lazyFutExpr: Future[T],
                              retries = 3,
                              timeout = 60.seconds): untyped =
  const
    reqType = astToStr(lazyFutExpr)
  var
    retryDelayMs = 16000
    f: Future[T]
    attempts = 0

  while true:
    f = lazyFutExpr
    yield f or sleepAsync(timeout)
    if not f.finished:
      await cancelAndWait(f)
    elif f.failed:
      when not (f.error of CatchableError):
        static: doAssert false, "f.error not CatchableError"
      debug "Web3 request failed", req = reqType, err = f.error.msg
    else:
      break

    inc attempts
    if attempts >= retries:
      var errorMsg = reqType & " failed " & $retries & " times"
      if f.failed: errorMsg &= ". Last error: " & f.error.msg
      raise newException(DataProviderFailure, errorMsg)

    await sleepAsync(chronos.milliseconds(retryDelayMs))
    retryDelayMs *= 2

  read(f)

proc verifyChaindId*(p: VerifiedRpcProxy): Future[void] {.async.} =
  let localId = p.chainId

  # retry 2 times, if the data provider fails despite the re-tries, propagate
  # exception to the caller.
  let providerId = awaitWithRetries(
    p.rpcClient.eth_chainId(),
    retries = 2,
    timeout = seconds(30)
  )

  # This is a chain/network mismatch error between the Nimbus verified proxy and
  # the application using it. Fail fast to avoid misusage. The user must fix
  # the configuration.
  if localId != providerId:
    fatal "The specified data provider serves data for a different chain",
      expectedChain = distinctBase(localId),
      providerChain = distinctBase(providerId)
    quit 1

  return