## Nim-Codex
## Copyright (c) 2023 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.

{.push raises: [].}

import std/tables
import std/sugar

import pkg/libp2p/multicodec
import pkg/libp2p/multihash
import pkg/libp2p/cid
import pkg/results
import pkg/questionable/results

import ./units
import ./errors

export tables

const
  # Size of blocks for storage / network exchange,
  DefaultBlockSize* = NBytes 1024 * 64
  DefaultCellSize* = NBytes 2048

  # Proving defaults
  DefaultMaxSlotDepth*    = 32
  DefaultMaxDatasetDepth* = 8
  DefaultBlockDepth*      = 5
  DefaultCellElms*        = 67
  DefaultSamplesNum*      = 5

  # hashes
  Sha256HashCodec* = multiCodec("sha2-256")
  Sha512HashCodec* = multiCodec("sha2-512")
  Pos2Bn128SpngCodec* = multiCodec("poseidon2-alt_bn_128-sponge-r2")
  Pos2Bn128MrklCodec* = multiCodec("poseidon2-alt_bn_128-merkle-2kb")

  ManifestCodec* = multiCodec("codex-manifest")
  DatasetRootCodec* = multiCodec("codex-root")
  BlockCodec* = multiCodec("codex-block")
  SlotRootCodec* = multiCodec("codex-slot-root")
  SlotProvingRootCodec* = multiCodec("codex-proving-root")
  CodexSlotCellCodec* = multiCodec("codex-slot-cell")

  CodexHashesCodecs* = [
    Sha256HashCodec,
    Pos2Bn128SpngCodec,
    Pos2Bn128MrklCodec
  ]

  CodexPrimitivesCodecs* = [
    ManifestCodec,
    DatasetRootCodec,
    BlockCodec,
    SlotRootCodec,
    SlotProvingRootCodec,
    CodexSlotCellCodec,
  ]

proc initEmptyCidTable(): ?!Table[(CidVersion, MultiCodec, MultiCodec), Cid] =
  ## Initialize padding blocks table
  ##
  ## TODO: Ideally this is done at compile time, but for now
  ## we do it at runtime because of an `importc` error that is
  ## coming from somewhere in MultiHash that I can't track down.
  ##

  let
    emptyData: seq[byte] = @[]
    PadHashes = {
      Sha256HashCodec: ? MultiHash.digest($Sha256HashCodec, emptyData).mapFailure,
      Sha512HashCodec: ? MultiHash.digest($Sha512HashCodec, emptyData).mapFailure,
    }.toTable

  var
    table = initTable[(CidVersion, MultiCodec, MultiCodec), Cid]()

  for hcodec, mhash in PadHashes.pairs:
    table[(CIDv1, hcodec, BlockCodec)] = ? Cid.init(CIDv1, BlockCodec, mhash).mapFailure

  success table

proc emptyCid*(
  version: CidVersion,
  hcodec: MultiCodec,
  dcodec: MultiCodec): ?!Cid =
  ## Returns cid representing empty content,
  ## given cid version, hash codec and data codec
  ##

  var
    table {.global, threadvar.}: Table[(CidVersion, MultiCodec, MultiCodec), Cid]

  once:
    table = ? initEmptyCidTable()

  table[(version, hcodec, dcodec)].catch

proc emptyDigest*(
  version: CidVersion,
  hcodec: MultiCodec,
  dcodec: MultiCodec): ?!MultiHash =
  ## Returns hash representing empty content,
  ## given cid version, hash codec and data codec
  ##
  emptyCid(version, hcodec, dcodec)
    .flatMap((cid: Cid) => cid.mhash.mapFailure)