# 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  stint

type
  Fork* = enum
    # FkGenesis
    FkFrontier,
    FkThawing,
    FkHomestead,
    FkDao,
    FkTangerine,
    FkSpurious,
    FkByzantium

  UInt256Pair = tuple[a: Uint256, b: Uint256]

let forkBlocks: array[Fork, Uint256] = [
  FkFrontier:           1.u256, # 30/07/2015 19:26:28
  FkThawing:      200_000.u256, # 08/09/2015 01:33:09
  FkHomestead:  1_150_000.u256, # 14/03/2016 20:49:53
  FkDao:        1_920_000.u256, # 20/07/2016 17:20:40
  FkTangerine:  2_463_000.u256, # 18/10/2016 17:19:31
  FkSpurious:   2_675_000.u256, # 22/11/2016 18:15:44
  FkByzantium:  4_370_000.u256  # 16/10/2017 09:22:11
]

proc toFork*(blockNumber: UInt256): Fork =

  # TODO: uint256 comparison is probably quite expensive
  #       hence binary search is probably worth it earlier than
  #       linear search

  # TODO: all toFork usage currently incurs comparison to get the fork and then another comparison to
  #       go to the ultimate needed result.

  # Genesis block 0 also uses the Frontier code path
  if blockNumber < forkBlocks[FkThawing]:     FkFrontier
  elif blockNumber < forkBlocks[FkHomestead]: FkThawing
  elif blockNumber < forkBlocks[FkDao]:       FkHomestead
  elif blockNumber < forkBlocks[FkTangerine]: FkDao
  elif blockNumber < forkBlocks[FkSpurious]:  FkTangerine
  elif blockNumber < forkBlocks[FkByzantium]: FkSpurious
  else:
    FkByzantium # Update for constantinople when announced