# Nimbus
# Copyright (c) 2022 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
  chronos,
  stint,
  json_rpc/rpcclient,
  web3,
  ./computation,
  ./state,
  ./types,
  ../db/accounts_cache



# Used in synchronous mode.
proc noLazyDataSource*(): LazyDataSource =
  LazyDataSource(
    ifNecessaryGetStorage: (proc(c: Computation, slot: UInt256): Future[void] {.async.} =
      discard
    )
  )

# Will be used in asynchronous on-demand-data-fetching mode, once
# that is implemented.
proc realLazyDataSource*(client: RpcClient): LazyDataSource =
  LazyDataSource(
    ifNecessaryGetStorage: (proc(c: Computation, slot: UInt256): Future[void] {.async.} =
      # TODO: find some way to check whether we already have it.
      # This is WRONG, but good enough for now, considering this
      # code is unused except in a few tests. I'm working on
      # doing this properly.
      if not c.getStorage(slot).isZero: return

      # FIXME-onDemandStorageNotImplementedYet
      # (I sketched in this code, but haven't actually tried running it yet.)
      echo("Attempting to for-real fetch slot " & $(slot))
      # ethAddressStr("0xfff33a3bd36abdbd412707b8e310d6011454a7ae")
      # check hexDataStr(0.u256).string == res.string
      let ethAddress = c.msg.contractAddress
      let address: Address = Address(ethAddress)
      let quantity: int = slot.truncate(int)  # this is probably wrong; what's the right way to convert this?
      let blockId: BlockIdentifier = blockId(c.vmState.parent.blockNumber.truncate(uint64)) # ditto
      let res = await client.eth_getStorageAt(address, quantity, blockId)
      echo("Fetched slot " & $(slot) & ", result is " & $(res))
      let v = res  # will res be the actual value, or do I need to convert or something?
      
      # Before implementing this, see the note from Zahary here:
      # https://github.com/status-im/nimbus-eth1/pull/1260#discussion_r999669139
      # 
      # c.vmState.mutateStateDB:
      #   db.setStorage(c.msg.contractAddress, slot, UInt256.fromBytesBE(v))
    )
  )

# Used for unit testing. Contains some prepopulated data.
proc fakeLazyDataSource*(fakePairs: seq[tuple[key, val: array[32, byte]]]): LazyDataSource =
  LazyDataSource(
    ifNecessaryGetStorage: (proc(c: Computation, slot: UInt256): Future[void] {.async.} =
      # See the comment above.
      if not c.getStorage(slot).isZero: return

      # FIXME-writeAutomatedTestsToShowThatItCanRunConcurrently

      # For now, until I've implemented some more automated way to
      # capture and verify the fact that this can run concurrently,
      # this is useful just to see in the console that the echo
      # statements from multiple Computations can run at the same
      # time and be interleaved.
      # echo("Attempting to fake-fetch slot " & $(slot))
      # await sleepAsync(2.seconds)  

      let slotBytes = toBytesBE(slot)
      # The linear search is obviously slow, but doesn't matter
      # for tests with only a few initialStorage entries. Fix
      # this if we ever want to write tests with more.
      for (k, v) in fakePairs:
        if slotBytes == k:
          c.vmState.mutateStateDB:
            db.setStorage(c.msg.contractAddress, slot, UInt256.fromBytesBE(v))
          break

      # echo("Finished fake-fetch of slot " & $(slot))
    )
  )




# Gotta find the place where we're creating a Computation without setting
# its asyncFactory in the first place, but this is fine for now.
proc asyncFactory*(c: Computation): AsyncOperationFactory =
  # Does Nim have an "ifNil" macro/template?
  if isNil(c.vmState.asyncFactory):
    AsyncOperationFactory(lazyDataSource: noLazyDataSource()) # AARDVARK - can I make a singleton?
  else:
    c.vmState.asyncFactory