# 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.

import
  macros, strformat, tables,
  eth_common,
  ./logging, ./constants, ./errors, ./transaction, ./db/[db_chain, state_db],
  ./utils/header

type
  BaseVMState* = ref object of RootObj
    prevHeaders*: seq[BlockHeader]
    # receipts*:
    chaindb*: BaseChainDB
    accessLogs*: AccessLogs
    blockHeader*: BlockHeader
    name*: string

  AccessLogs* = ref object
    reads*: Table[string, string]
    writes*: Table[string, string]

proc newAccessLogs*: AccessLogs =
  AccessLogs(reads: initTable[string, string](), writes: initTable[string, string]())

proc update*[K, V](t: var Table[K, V], elements: Table[K, V]) =
  for k, v in elements:
    t[k] = v

proc `$`*(vmState: BaseVMState): string =
  if vmState.isNil:
    result = "nil"
  else:
    result = &"VMState {vmState.name}:\n  header: {vmState.blockHeader}\n  chaindb:  {vmState.chaindb}"

proc newBaseVMState*(header: BlockHeader, chainDB: BaseChainDB): BaseVMState =
  new result
  result.prevHeaders = @[]
  result.name = "BaseVM"
  result.accessLogs = newAccessLogs()
  result.blockHeader = header
  result.chaindb = chainDB

method logger*(vmState: BaseVMState): Logger =
  logging.getLogger(&"evm.vmState.{vmState.name}")

method blockhash*(vmState: BaseVMState): Hash256 =
  vmState.blockHeader.hash

method coinbase*(vmState: BaseVMState): EthAddress =
  vmState.blockHeader.coinbase

method timestamp*(vmState: BaseVMState): EthTime =
  vmState.blockHeader.timestamp

method blockNumber*(vmState: BaseVMState): BlockNumber =
  vmState.blockHeader.blockNumber

method difficulty*(vmState: BaseVMState): UInt256 =
  vmState.blockHeader.difficulty

method gasLimit*(vmState: BaseVMState): GasInt =
  vmState.blockHeader.gasLimit

method getAncestorHash*(vmState: BaseVMState, blockNumber: BlockNumber): Hash256 =
  var ancestorDepth = vmState.blockHeader.blockNumber - blockNumber - 1
  if ancestorDepth >= constants.MAX_PREV_HEADER_DEPTH or ancestorDepth < 0:
    return

  let idx = ancestorDepth.toInt
  if idx >= vmState.prevHeaders.len:
    return

  var header = vmState.prevHeaders[idx]
  result = header.hash

when false:
  # this was an older version of `mutateStateDB`, kept here for reference
  # until `mutateStateDB` is fully implemented.
  macro db*(vmState: untyped, readOnly: bool, handler: untyped): untyped =
    # vm.state.db:
    #   setupStateDB(fixture{"pre"}, stateDb)
    #   code = db.getCode(fixture{"exec"}{"address"}.getStr)
    let db = ident("db")
    result = quote:
      block:
        var `db` = `vmState`.chaindb.getStateDB(`vmState`.blockHeader.stateRoot, `readOnly`)
        `handler`
        if `readOnly`:
          # This acts as a secondary check that no mutation took place for
          # read_only databases.
          assert `db`.rootHash == `vmState`.blockHeader.stateRoot
        elif `vmState`.blockHeader.stateRoot != `db`.rootHash:
          `vmState`.blockHeader.stateRoot = `db`.rootHash

        # TODO
        # `vmState`.accessLogs.reads.update(`db`.db.accessLogs.reads)
        # `vmState`.accessLogs.writes.update(`db`.db.accessLogs.writes)

        # remove the reference to the underlying `db` object to ensure that no
        # further modifications can occur using the `State` object after
        # leaving the context.
        # TODO `db`.db = nil
        # state._trie = None

template mutateStateDB*(vmState: BaseVMState, body: untyped) =
  # This should provide more clever change handling in the future
  block:
    let initialStateRoot = vmState.blockHeader.stateRoot
    var db {.inject.} = vmState.chaindb.getStateDB(initialStateRoot, false)

    body

    let finalStateRoot = db.rootHash
    if finalStateRoot != initialStateRoot:
      vmState.blockHeader.stateRoot = finalStateRoot

proc readOnlyStateDB*(vmState: BaseVMState): AccountStateDB {.inline.}=
  vmState.chaindb.getStateDb(vmState.blockHeader.stateRoot, readOnly = true)