nim-codex/dagger/manifest/coders.nim

## Nim-Dagger
## Copyright (c) 2022 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.

import pkg/upraises

push: {.upraises: [].}

import std/tables

import pkg/libp2p
import pkg/questionable
import pkg/questionable/results
import pkg/chronicles
import pkg/chronos

import ./manifest
import ../errors
import ./types

func encode*(_: DagPBCoder, manifest: Manifest): ?!seq[byte] =
  ## Encode the manifest into a ``ManifestCodec``
  ## multicodec container (Dag-pb) for now
  ##

  var pbNode = initProtoBuffer()

  for c in manifest.blocks:
    var pbLink = initProtoBuffer()
    pbLink.write(1, c.data.buffer) # write Cid links
    pbLink.finish()
    pbNode.write(2, pbLink)

  # NOTE: The `Data` field in the the `dag-pb`
  # contains the following protobuf `Message`
  #
  # ```protobuf
  #   Message ErasureInfo {
  #     optional uint32 K = 1;          # number of encoded blocks
  #     optional uint32 M = 2;          # number of parity blocks
  #     optional bytes cid = 3;         # cid of the original dataset
  #     optional uint32 original = 4;   # number of original blocks
  #   }
  #   Message Header {
  #     optional bytes rootHash = 1;      # the root (tree) hash
  #     optional uint32 blockSize = 2;    # size of a single block
  #     optional uint32 blocksLen = 3;    # total amount of blocks
  #     optional ErasureInfo erasure = 4; # erasure coding info
  #   }
  # ```
  #

  let cid = !manifest.rootHash
  var header = initProtoBuffer()
  header.write(1, cid.data.buffer)
  header.write(2, manifest.blockSize.uint32)
  header.write(3, manifest.len.uint32)
  if manifest.protected:
    var erasureInfo = initProtoBuffer()
    erasureInfo.write(1, manifest.K.uint32)
    erasureInfo.write(2, manifest.M.uint32)
    erasureInfo.write(3, manifest.originalCid.data.buffer)
    erasureInfo.write(4, manifest.originalLen.uint32)
    erasureInfo.finish()

    header.write(4, erasureInfo)

  pbNode.write(1, header) # set the rootHash Cid as the data field
  pbNode.finish()

  return pbNode.buffer.success

func decode*(_: DagPBCoder, data: openArray[byte]): ?!Manifest =
  ## Decode a manifest from a data blob
  ##

  var
    pbNode = initProtoBuffer(data)
    pbHeader: ProtoBuffer
    pbErasureInfo: ProtoBuffer
    rootHash: seq[byte]
    originalCid: seq[byte]
    blockSize: uint32
    blocksLen: uint32
    originalLen: uint32
    K, M: uint32
    blocks: seq[Cid]

  # Decode `Header` message
  if pbNode.getField(1, pbHeader).isErr:
    return failure("Unable to decode `Header` from dag-pb manifest!")

  # Decode `Header` contents
  if pbHeader.getField(1, rootHash).isErr:
    return failure("Unable to decode `rootHash` from manifest!")

  if pbHeader.getField(2, blockSize).isErr:
    return failure("Unable to decode `blockSize` from manifest!")

  if pbHeader.getField(3, blocksLen).isErr:
    return failure("Unable to decode `blocksLen` from manifest!")

  if pbHeader.getField(4, pbErasureInfo).isErr:
    return failure("Unable to decode `erasureInfo` from manifest!")

  if pbErasureInfo.buffer.len > 0:
    if pbErasureInfo.getField(1, K).isErr:
      return failure("Unable to decode `K` from manifest!")

    if pbErasureInfo.getField(2, M).isErr:
      return failure("Unable to decode `M` from manifest!")

    if pbErasureInfo.getField(3, originalCid).isErr:
      return failure("Unable to decode `originalCid` from manifest!")

    if pbErasureInfo.getField(4, originalLen).isErr:
      return failure("Unable to decode `originalLen` from manifest!")

  let rootHashCid = ? Cid.init(rootHash).mapFailure
  var linksBuf: seq[seq[byte]]
  if pbNode.getRepeatedField(2, linksBuf).isOk:
    for pbLinkBuf in linksBuf:
      var
        blocksBuf: seq[seq[byte]]
        blockBuf: seq[byte]
        pbLink = initProtoBuffer(pbLinkBuf)

      if pbLink.getField(1, blockBuf).isOk:
        blocks.add(? Cid.init(blockBuf).mapFailure)

  if blocksLen.int != blocks.len:
    return failure("Total blocks and length of blocks in header don't match!")

  var
    self = Manifest(
      rootHash: rootHashCid.some,
      blockSize: blockSize.int,
      blocks: blocks,
      hcodec: (? rootHashCid.mhash.mapFailure).mcodec,
      codec: rootHashCid.mcodec,
      version: rootHashCid.cidver,
      protected: pbErasureInfo.buffer.len > 0)

  if self.protected:
    self.K = K.int
    self.M = M.int
    self.originalCid = ? Cid.init(originalCid).mapFailure
    self.originalLen = originalLen.int

  self.success

proc encode*(
  self: Manifest,
  encoder = ManifestContainers[$DagPBCodec]): ?!seq[byte] =
  ## Encode a manifest using `encoder`
  ##

  if self.rootHash.isNone:
    ? self.makeRoot()

  encoder.encode(self)

func decode*(
  _: type Manifest,
  data: openArray[byte],
  decoder = ManifestContainers[$DagPBCodec]): ?!Manifest =
  ## Decode a manifest using `decoder`
  ##

  decoder.decode(data)