# Nimbus
# Copyright (c) 2021 Status Research & Development GmbH
# Licensed under either of
#  * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE))
#  * MIT license ([LICENSE-MIT](LICENSE-MIT))
# at your option.
# This file may not be copied, modified, or distributed except according to
# those terms.

import
  std/[tables, strutils],
  eth/[common, keys, rlp],
  chronos, stint,
  stew/byteutils,
  json_rpc/[rpcclient],
  ../../../nimbus/utils/utils,
  ../../../nimbus/transaction,
  ../../../nimbus/rpc/hexstrings,
  ./client

const
  # This is the account that sends vault funding transactions.
  vaultAccountAddr = hextoByteArray[20]("0xcf49fda3be353c69b41ed96333cd24302da4556f")

const
  # Address of the vault in genesis.
  predeployedVaultAddr = hextoByteArray[20]("0000000000000000000000000000000000000315")
  # Number of blocks to wait before funding tx is considered valid.
  vaultTxConfirmationCount = 5

# vault creates accounts for testing and funds them. An instance of the vault contract is
# deployed in the genesis block. When creating a new account using createAccount, the
# account is funded by sending a transaction to this contract.
#
# The purpose of the vault is allowing tests to run concurrently without worrying about
# nonce assignment and unexpected balance changes.
type
  Vault* = ref object
    # This tracks the account nonce of the vault account.
    nonce: AccountNonce
    # Created accounts are tracked in this map.
    accounts: Table[EthAddress, PrivateKey]

    rng: ref HmacDrbgContext
    chainID: ChainID
    gasPrice: GasInt
    vaultKey: PrivateKey
    client:   RpcClient

proc newVault*(chainID: ChainID, gasPrice: GasInt, client: RpcClient): Vault =
  new(result)
  result.rng      = newRng()
  result.chainID  = chainID
  result.gasPrice = gasPrice
  result.vaultKey = PrivateKey.fromHex("63b508a03c3b5937ceb903af8b1b0c191012ef6eb7e9c3fb7afa94e5d214d376").get()
  result.client   = client

# generateKey creates a new account key and stores it.
proc generateKey*(v: Vault): EthAddress =
  let key = PrivateKey.random(v.rng[])
  let address = toCanonicalAddress(key.toPublicKey)
  v.accounts[address] = key
  address

# nextNonce generates the nonce of a funding transaction.
proc nextNonce*(v: Vault): AccountNonce =
  let nonce = v.nonce
  inc(v.nonce)
  nonce

proc sendSome(address: EthAddress, amount: UInt256): seq[byte] =
  const padding = repeat('\0', 12).toBytes
  # makeshift contract ABI construction
  # https://docs.soliditylang.org/en/develop/abi-spec.html
  let h = keccakHash("sendSome(address,uint256)".toBytes)
  result.add h.data[0..3] # first 4 bytes of hash
  result.add padding # left pad address
  result.add address
  result.add amount.toBytesBE
  doAssert(result.len == 68) # 4 + 32 + 32

proc makeFundingTx*(v: Vault, recipient: EthAddress, amount: UInt256): Transaction =
  let
    unsignedTx = Transaction(
      txType  : TxLegacy,
      chainId : v.chainId,
      nonce   : v.nextNonce(),
      gasPrice: v.gasPrice,
      gasLimit: GasInt(75000),
      to      : some(predeployedVaultAddr),
      value   : 0.u256,
      payload : sendSome(recipient, amount)
    )

  signTransaction(unsignedTx, v.vaultKey, v.chainId, eip155 = true)

proc signTx*(v: Vault,
             sender: EthAddress,
             nonce: AccountNonce,
             recipient: EthAddress,
             amount: UInt256,
             gasLimit, gasPrice: GasInt,
             payload: seq[byte] = @[]): Transaction =

  let
    unsignedTx = Transaction(
      txType  : TxLegacy,
      chainId : v.chainId,
      nonce   : nonce,
      gasPrice: gasPrice,
      gasLimit: gasLimit,
      to      : some(recipient),
      value   : amount,
      payload : payload
    )

  let key = v.accounts[sender]
  signTransaction(unsignedTx, key, v.chainId, eip155 = true)

# createAccount creates a new account that is funded from the vault contract.
# It will panic when the account could not be created and funded.
proc createAccount*(v: Vault, amount: UInt256): Future[EthAddress] {.async.} =
  let address = v.generateKey()

  # order the vault to send some ether
  let tx = v.makeFundingTx(address, amount)
  let res = await v.client.sendTransaction(tx)
  if not res:
    raise newException(ValueError, "unable to send funding transaction")

  let txBlock = await v.client.blockNumber()

  # wait for vaultTxConfirmationCount confirmation by checking the balance vaultTxConfirmationCount blocks back.
  # createAndFundAccountWithSubscription for a better solution using logs
  let count = vaultTxConfirmationCount*4
  for i in 0..<count:
    let number = await v.client.blockNumber()
    if number > txBlock + vaultTxConfirmationCount:
      let checkBlock = number - vaultTxConfirmationCount
      let balance = await v.client.balanceAt(address, checkBlock)
      if balance >= amount:
        return address

    let period = chronos.seconds(1)
    await sleepAsync(period)

  let txHash = tx.rlpHash().data.toHex
  raise newException(ValueError, "could not fund account $2 in transaction $2" % [address.toHex, txHash])