LegacyWal.walk: def of mylsm-lsm-store@0.6.0.1
Import: import mylsm-lsm-store@0.6.0.1/src/transfer/LegacyWal.bend as LegacyWal
Lines 129-209 of mylsm-lsm-store@0.6.0.1/src/transfer/LegacyWal.bend: https://jend.leeeet.dev/read.txt?path=mylsm-lsm-store@0.6.0.1/src/transfer/LegacyWal.bend&start_line=129&end_line=209

import Base
import mylsm-lsm-store@0.6.0.1/src/coordinator/QueuePolicy.bend as QueuePolicy
import mylsm-lsm-store@0.6.0.1/src/Wal.bend as Wal
import bend-kit-bytes@0.3.2.0/bytes.bend as Bytes

# Applies one pure parser transition, rejecting malformed or truncated frames.
def walk(fuel: Nat, state: WalkState) -> VerifyResult:
  match fuel:
    case 0n: WalInvalid{}
    case 1n+rest:
      match state:
        case Header{pair}:
          match pair:
            case (source, header):
              walk(rest, HeaderDecoded{source, Wal.decode_header(header)})
        case HeaderDecoded{source, result}:
          match result:
            case Fail{_}: WalInvalid{}
            case Done{Unit{}}:
              walk(rest, HeaderMeasured{Bytes.length(source)})
        case HeaderMeasured{pair}:
          match pair:
            case (source, size):
              walk(rest, HeaderSeek{
                Bytes.Cursor.seek(Bytes.Cursor.new(source), 8)})
        case HeaderSeek{pair}:
          match pair:
            case (_, False{}): WalInvalid{}
            case (cursor, True{}): walk(rest, Read{cursor, 0n})
        case Read{cursor, frames}:
          walk(rest, Remaining{Bytes.Cursor.remaining(cursor), frames})
        case Remaining{pair, frames}:
          match pair:
            case (cursor, remaining):
              walk(rest, Empty{cursor, U32.to_nat(remaining), frames})
        case Empty{cursor, remaining, frames}:
          walk(rest, walk.empty.checked(cursor, frames,
            QueuePolicy.nat.clone.pair(remaining)))
        case EmptyChecked{cursor, remaining, frames, empty}:
          match empty:
            case True{}: walk(rest, Finish{frames})
            case False{}:
              walk(rest, walk.length.checked(cursor, frames,
                QueuePolicy.nat.clone.pair(remaining)))
        case HasLength{cursor, remaining, frames, has_length}:
          match has_length:
            case False{}: WalInvalid{}
            case True{}:
              walk(rest, Length{Bytes.Cursor.u32be(cursor),
                U32.from_nat(Nat.sub(remaining, 4n)), frames})
        case Length{pair, remaining, frames}:
          match pair:
            case (_, None{}): WalInvalid{}
            case (cursor, Some{length}):
              walk(rest, walk.length.validated(cursor, remaining, frames, length))
        case Bounds{cursor, length, frames, valid}:
          match valid:
            case False{}: WalInvalid{}
            case True{}:
              walk(rest, walk.position.state(cursor, frames,
                QueuePolicy.nat.clone.pair(U32.to_nat(length))))
        case Position{cursor, positions, frame_bytes, frame_length, frames}:
          match cursor:
            case Bytes.Cursor{bytes, _, _, _}:
              match positions:
                case (start_nat, end_nat):
                  +start = U32.from_nat(Nat.sub(start_nat, 4n))
                  +end = U32.add(U32.from_nat(end_nat), frame_length)
                  walk(rest, Frame{Bytes.slice(bytes, start, frame_bytes),
                    end, frames})
        case Frame{pair, end, frames}:
          match pair:
            case (source, frame):
              walk(rest, Decoded{Wal.decode_frame(frame), source, end, frames})
        case Decoded{result, source, end, frames}:
          match result:
            case Fail{_}: WalInvalid{}
            case Done{_}:
              walk(rest, Seek{Bytes.Cursor.seek(Bytes.Cursor.new(source), end),
                Nat.add(frames, 1n)})
        case Seek{pair, frames}:
          match pair:
            case (_, False{}): WalInvalid{}
            case (cursor, True{}): walk(rest, Read{cursor, frames})
        case Finish{frames}: WalValid{frames}
        case Invalid{}: WalInvalid{}

Uses (27):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Bool
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Maybe
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Nat
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Nat.add
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Nat.sub
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Result
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Sigma
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=U32.add
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=U32.from_nat
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=U32.to_nat
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Unit
  https://jend.leeeet.dev/definition.txt?path=bend-kit-bytes@0.3.3.0/bytes.bend&name=Cursor
  https://jend.leeeet.dev/definition.txt?path=bend-kit-bytes@0.3.3.0/bytes.bend&name=Cursor.new
  https://jend.leeeet.dev/definition.txt?path=bend-kit-bytes@0.3.3.0/bytes.bend&name=Cursor.remaining
  https://jend.leeeet.dev/definition.txt?path=bend-kit-bytes@0.3.3.0/bytes.bend&name=Cursor.seek
  https://jend.leeeet.dev/definition.txt?path=bend-kit-bytes@0.3.3.0/bytes.bend&name=Cursor.u32be
  https://jend.leeeet.dev/definition.txt?path=bend-kit-bytes@0.3.3.0/bytes.bend&name=length
  https://jend.leeeet.dev/definition.txt?path=bend-kit-bytes@0.3.3.0/bytes.bend&name=slice
  https://jend.leeeet.dev/definition.txt?path=mylsm-lsm-store@0.6.0.1/src/Wal.bend&name=decode_frame
  https://jend.leeeet.dev/definition.txt?path=mylsm-lsm-store@0.6.0.1/src/Wal.bend&name=decode_header
  https://jend.leeeet.dev/definition.txt?path=mylsm-lsm-store@0.6.0.1/src/coordinator/QueuePolicy.bend&name=nat.clone.pair
  https://jend.leeeet.dev/definition.txt?path=mylsm-lsm-store@0.6.0.1/src/transfer/LegacyWal.bend&name=VerifyResult
  https://jend.leeeet.dev/definition.txt?path=mylsm-lsm-store@0.6.0.1/src/transfer/LegacyWal.bend&name=WalkState
  https://jend.leeeet.dev/definition.txt?path=mylsm-lsm-store@0.6.0.1/src/transfer/LegacyWal.bend&name=walk.empty.checked
  https://jend.leeeet.dev/definition.txt?path=mylsm-lsm-store@0.6.0.1/src/transfer/LegacyWal.bend&name=walk.length.checked
  https://jend.leeeet.dev/definition.txt?path=mylsm-lsm-store@0.6.0.1/src/transfer/LegacyWal.bend&name=walk.length.validated
  https://jend.leeeet.dev/definition.txt?path=mylsm-lsm-store@0.6.0.1/src/transfer/LegacyWal.bend&name=walk.position.state