# Nimbus
# Copyright (c) 2018 Status Research & Development GmbH
# Licensed under either of
#  * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or
#    http://www.apache.org/licenses/LICENSE-2.0)
#  * MIT license ([LICENSE-MIT](LICENSE-MIT) or
#    http://opensource.org/licenses/MIT)
# at your option. This file may not be copied, modified, or distributed except
# according to those terms.

## Transaction Pool Tasklets: Packer, VM execute and compact txs
## =============================================================
##

import
  std/[sets, tables],
  ../../../db/[accounts_cache, db_chain],
  ../../../forks,
  ../../../p2p/[dao, executor, validate],
  ../../../transaction/call_evm,
  ../../../transaction,
  ../../../vm_state,
  ../../../vm_types,
  ../tx_chain,
  ../tx_desc,
  ../tx_item,
  ../tx_tabs,
  ../tx_tabs/tx_status,
  ./tx_bucket,
  ./tx_classify,
  chronicles,
  eth/[common, keys, rlp, trie, trie/db],
  stew/[sorted_set]

{.push raises: [Defect].}

type
  TxPackerError* = object of CatchableError
    ## Catch and relay exception error

  TxPackerStateRef = ref object
    xp: TxPoolRef
    tr: HexaryTrie
    cleanState: bool
    balance: UInt256

const
  receiptsExtensionSize = ##\
    ## Number of slots to extend the `receipts[]` at the same time.
    20

logScope:
  topics = "tx-pool packer"

# ------------------------------------------------------------------------------
# Private helpers
# ------------------------------------------------------------------------------

template safeExecutor(info: string; code: untyped) =
  try:
    code
  except CatchableError as e:
    raise (ref CatchableError)(msg: e.msg)
  except Defect as e:
    raise (ref Defect)(msg: e.msg)
  except:
    let e = getCurrentException()
    raise newException(TxPackerError, info & "(): " & $e.name & " -- " & e.msg)

proc persist(pst: TxPackerStateRef)
    {.gcsafe,raises: [Defect,RlpError].} =
  ## Smart wrapper
  if not pst.cleanState:
    pst.xp.chain.vmState.stateDB.persist(clearCache = false)
    pst.cleanState = true

# ------------------------------------------------------------------------------
# Private functions
# ------------------------------------------------------------------------------

proc runTx(pst: TxPackerStateRef; item: TxItemRef): GasInt
    {.gcsafe,raises: [Defect,CatchableError].} =
  ## Execute item transaction and update `vmState` book keeping. Returns the
  ## `gasUsed` after executing the transaction.
  let
    fork = pst.xp.chain.nextFork
    baseFee = pst.xp.chain.baseFee
    tx = item.tx.eip1559TxNormalization(baseFee.GasInt, fork)

  safeExecutor "tx_packer.runTx":
    # Execute transaction, may return a wildcard `Exception`
    result = tx.txCallEvm(item.sender, pst.xp.chain.vmState, fork)

  pst.cleanState = false
  doAssert 0 <= result


proc runTxCommit(pst: TxPackerStateRef; item: TxItemRef; gasBurned: GasInt)
    {.gcsafe,raises: [Defect,CatchableError].} =
  ## Book keeping after executing argument `item` transaction in the VM. The
  ## function returns the next number of items `nItems+1`.
  let
    xp = pst.xp
    vmState = xp.chain.vmState
    inx = xp.txDB.byStatus.eq(txItemPacked).nItems
    gasTip = item.tx.effectiveGasTip(xp.chain.baseFee)

  # The gas tip cannot get negative as all items in the `staged` bucket
  # are vetted for profitability before entering that bucket.
  assert 0 <= gasTip
  let reward = gasBurned.u256 * gasTip.uint64.u256
  vmState.stateDB.addBalance(xp.chain.miner, reward)

  # Update account database
  vmState.mutateStateDB:
    for deletedAccount in vmState.selfDestructs:
      db.deleteAccount deletedAccount

    if FkSpurious <= xp.chain.nextFork:
      vmState.touchedAccounts.incl(xp.chain.miner)
      # EIP158/161 state clearing
      for account in vmState.touchedAccounts:
        if db.accountExists(account) and db.isEmptyAccount(account):
          debug "state clearing", account
          db.deleteAccount account

  if vmState.generateWitness:
    vmState.stateDB.collectWitnessData()

  # Save accounts via persist() is not needed unless the fork is smaller
  # than `FkByzantium` in which case, the `rootHash()` function is called
  # by `makeReceipt()`. As the `rootHash()` function asserts unconditionally
  # that the account cache has been saved, the `persist()` call is
  # obligatory here.
  if xp.chain.nextFork < FkByzantium:
    pst.persist

  # Update receipts sequence
  if vmState.receipts.len <= inx:
    vmState.receipts.setLen(inx + receiptsExtensionSize)

  vmState.cumulativeGasUsed += gasBurned
  vmState.receipts[inx] = vmState.makeReceipt(item.tx.txType)

  # Update txRoot
  pst.tr.put(rlp.encode(inx), rlp.encode(item.tx))

  # Add the item to the `packed` bucket. This implicitely increases the
  # receipts index `inx` at the next visit of this function.
  discard xp.txDB.reassign(item,txItemPacked)

# ------------------------------------------------------------------------------
# Private functions: packer packerVmExec() helpers
# ------------------------------------------------------------------------------

proc vmExecInit(xp: TxPoolRef): TxPackerStateRef
    {.gcsafe,raises: [Defect,CatchableError].} =

  # Flush `packed` bucket
  xp.bucketFlushPacked

  xp.chain.maxMode = (packItemsMaxGasLimit in xp.pFlags)

  if xp.chain.config.daoForkSupport and
     xp.chain.config.daoForkBlock == xp.chain.head.blockNumber + 1:
    xp.chain.vmState.mutateStateDB:
      db.applyDAOHardFork()

  TxPackerStateRef( # return value
    xp: xp,
    tr: newMemoryDB().initHexaryTrie,
    balance: xp.chain.vmState.readOnlyStateDB.getBalance(xp.chain.miner))


proc vmExecGrabItem(pst: TxPackerStateRef; item: TxItemRef): Result[bool,void]
    {.gcsafe,raises: [Defect,CatchableError].}  =
  ## Greedily collect & compact items as long as the accumulated `gasLimit`
  ## values are below the maximum block size.
  let
    xp = pst.xp
    vmState = xp.chain.vmState

  # Validate transaction relative to the current vmState
  if not xp.classifyValidatePacked(vmState, item):
    return ok(false) # continue with next account

  let
    accTx = vmState.stateDB.beginSavepoint
    gasUsed = pst.runTx(item) # this is the crucial part, running the tx

  # Find out what to do next: accepting this tx or trying the next account
  if not xp.classifyPacked(vmState.cumulativeGasUsed, gasUsed):
    vmState.stateDB.rollback(accTx)
    if xp.classifyPackedNext(vmState.cumulativeGasUsed, gasUsed):
      return ok(false) # continue with next account
    return err()       # otherwise stop collecting

  # Commit account state DB
  vmState.stateDB.commit(accTx)

  vmState.stateDB.persist(clearCache = false)
  let midRoot = vmState.stateDB.rootHash

  # Finish book-keeping and move item to `packed` bucket
  pst.runTxCommit(item, gasUsed)

  ok(true) # fetch the very next item


proc vmExecCommit(pst: TxPackerStateRef)
    {.gcsafe,raises: [Defect,CatchableError].} =
  let
    xp = pst.xp
    vmState = xp.chain.vmState
    disableReward = vmState.chainDB.config.poaEngine or
                    vmState.ttdReached # EIP-3675: no reward for miner

  if not disableReward:
    let
      number = xp.chain.head.blockNumber + 1
      uncles: seq[BlockHeader] = @[] # no uncles yet
    vmState.calculateReward(xp.chain.miner, number + 1, uncles)

  # Reward beneficiary
  vmState.mutateStateDB:
    if vmState.generateWitness:
      db.collectWitnessData()
    # Finish up, then vmState.stateDB.rootHash may be accessed
    db.persist(ClearCache in vmState.flags)

  # Update flexi-array, set proper length
  let nItems = xp.txDB.byStatus.eq(txItemPacked).nItems
  vmState.receipts.setLen(nItems)

  xp.chain.receipts = vmState.receipts
  xp.chain.txRoot = pst.tr.rootHash
  xp.chain.stateRoot = vmState.stateDB.rootHash

  proc balanceDelta: UInt256 =
    let postBalance = vmState.readOnlyStateDB.getBalance(xp.chain.miner)
    if pst.balance < postBalance:
      return postBalance - pst.balance

  xp.chain.profit = balanceDelta()
  xp.chain.reward = balanceDelta()

# ------------------------------------------------------------------------------
# Public functions
# ------------------------------------------------------------------------------

proc packerVmExec*(xp: TxPoolRef) {.gcsafe,raises: [Defect,CatchableError].} =
  ## Rebuild `packed` bucket by selection items from the `staged` bucket
  ## after executing them in the VM.
  let dbTx = xp.chain.db.db.beginTransaction
  defer: dbTx.dispose()

  var pst = xp.vmExecInit

  block loop:
    for (_,nonceList) in pst.xp.txDB.packingOrderAccounts(txItemStaged):

      block account:
        for item in nonceList.incNonce:

          let rc = pst.vmExecGrabItem(item)
          if rc.isErr:
            break loop    # stop
          if not rc.value:
            break account # continue with next account

  pst.vmExecCommit
  # Block chain will roll back automatically

# ------------------------------------------------------------------------------
# End
# ------------------------------------------------------------------------------