# Extensions for libp2p's protobuf library implementation

when (NimMajor, NimMinor) < (1, 4):
  {.push raises: [Defect].}
else:
  {.push raises: [].}

import
  std/options,
  libp2p/protobuf/minprotobuf,
  libp2p/varint

export
  minprotobuf,
  varint


## Custom errors

type
  ProtobufErrorKind* {.pure.} = enum
    DecodeFailure
    MissingRequiredField
    InvalidLengthField

  ProtobufError* = object
    case kind*: ProtobufErrorKind
    of DecodeFailure:
      error*: minprotobuf.ProtoError
    of MissingRequiredField, InvalidLengthField:
      field*: string

  ProtobufResult*[T] = Result[T, ProtobufError]


converter toProtobufError*(err: minprotobuf.ProtoError): ProtobufError =
  case err:
  of minprotobuf.ProtoError.RequiredFieldMissing:
    ProtobufError(kind: ProtobufErrorKind.MissingRequiredField, field: "unknown")
  else:
    ProtobufError(kind: ProtobufErrorKind.DecodeFailure, error: err)


proc missingRequiredField*(T: type ProtobufError, field: string): T =
  ProtobufError(kind: ProtobufErrorKind.MissingRequiredField, field: field)

proc invalidLengthField*(T: type ProtobufError, field: string): T =
  ProtobufError(kind: ProtobufErrorKind.InvalidLengthField, field: field)


## Extension methods

proc write3*(proto: var ProtoBuffer, field: int, value: auto) =
  when value is Option:
    if value.isSome():
      proto.write(field, value.get())
  elif value is bool:
    proto.write(field, zint(value))
  else:
    proto.write(field, value)

proc finish3*(proto: var ProtoBuffer) =
  if proto.buffer.len > 0:
    proto.finish()
  else:
    proto.offset = 0

proc `==`*(a: zint64, b: zint64): bool =
  int64(a) == int64(b)

proc `$`*(err: ProtobufError): string =
  case err.kind:
  of DecodeFailure:
    case err.error:
    of VarintDecode:
      return "VarintDecode"
    of MessageIncomplete:
      return "MessageIncomplete"
    of BufferOverflow:
      return "BufferOverflow"
    of MessageTooBig:
      return "MessageTooBig"
    of BadWireType:
      return "BadWireType"
    of IncorrectBlob:
      return "IncorrectBlob"
    of RequiredFieldMissing:
      return "RequiredFieldMissing"
  of MissingRequiredField:
    return "MissingRequiredField " & err.field
  of InvalidLengthField:
    return "InvalidLengthField " & err.field