serialization.nim

import
  faststreams, serialization/[object_serialization, errors]

export
  faststreams, object_serialization, errors

template serializationFormatImpl(Name: untyped,
                                 Reader, Writer, PreferedOutput: distinct type,
                                 mimeTypeName: static string = "") {.dirty.} =
  # This indirection is required in order to be able to generate the
  # `mimeType` accessor template. Without the indirection, the template
  # mechanism of Nim will try to expand the `mimeType` param in the position
  # of the `mimeType` template name which will result in error.
  type Name* = object
  template ReaderType*(T: type Name): type = Reader
  template WriterType*(T: type Name): type = Writer
  template PreferedOutputType*(T: type Name): type = PreferedOutput
  template mimeType*(T: type Name): string = mimeTypeName

template serializationFormat*(Name: untyped,
                              Reader, Writer, PreferedOutput: distinct type,
                              mimeType: static string = "") =
  serializationFormatImpl(Name, Reader, Writer, PreferedOutput, mimeType)

proc encodeImpl(writer: var auto, value: auto) =
  mixin writeValue, getOutput
  writer.writeValue value

template encode*(Format: type, value: auto, params: varargs[untyped]): auto =
  mixin init, WriterType, PreferedOutputType
  var s = init OutputStream

  # TODO:
  # Remove this when statement once the following bug is fixed:
  # https://github.com/nim-lang/Nim/issues/9996
  when astToStr(params) != "":
    var writer = init(WriterType(Format), s, params)
  else:
    var writer = init(WriterType(Format), s)

  encodeImpl(writer, value)
  s.getOutput PreferedOutputType(Format)

proc readValue*(reader: var auto, T: type): T =
  mixin readValue
  reader.readValue(result)

template decode*(Format: distinct type,
                 input: string,
                 RecordType: distinct type,
                 params: varargs[untyped]): auto =
  # TODO, this is dusplicated only due to a Nim bug:
  # If `input` was `string|openarray[byte]`, it won't match `seq[byte]`
  mixin init, ReaderType
  var stream = memoryStream(input)

  # TODO:
  # Remove this when statement once the following bug is fixed:
  # https://github.com/nim-lang/Nim/issues/9996
  when astToStr(params) != "":
    var reader = init(ReaderType(Format), stream, params)
  else:
    var reader = init(ReaderType(Format), stream)

  reader.readValue(RecordType)

template decode*(Format: distinct type,
                 input: openarray[byte],
                 RecordType: distinct type,
                 params: varargs[untyped]): auto =
  # TODO, this is dusplicated only due to a Nim bug:
  # If `input` was `string|openarray[byte]`, it won't match `seq[byte]`
  mixin init, ReaderType
  var stream = memoryStream(input)

  # TODO:
  # Remove this when statement once the following bug is fixed:
  # https://github.com/nim-lang/Nim/issues/9996
  when astToStr(params) != "":
    var reader = init(ReaderType(Format), stream, params)
  else:
    var reader = init(ReaderType(Format), stream)

  reader.readValue(RecordType)

template loadFile*(Format: distinct type,
                   filename: string,
                   RecordType: distinct type,
                   params: varargs[untyped]): auto =
  mixin init, ReaderType
  var stream = openFile(filename)

  # TODO:
  # Remove this when statement once the following bug is fixed:
  # https://github.com/nim-lang/Nim/issues/9996
  when astToStr(params) != "":
    var reader = init(ReaderType(Format), stream, params)
  else:
    var reader = init(ReaderType(Format), stream)

  reader.readValue(RecordType)

template loadFile*[RecordType](Format: type,
                               filename: string,
                               record: var RecordType,
                               params: varargs[untyped]) =
  record = loadFile(Format, filename, RecordType, params)

template saveFile*(Format: type, filename: string, args: varargs[untyped]) =
  # TODO: This should use a proper output stream, instead of calling `encode`
  writeFile(filename, Format.encode(args))

template borrowSerialization*(Alias: distinct type,
                              OriginalType: distinct type) {.dirty.} =

  proc writeValue*[Writer](writer: var Writer, value: Alias) =
    mixin writeValue
    writeValue(writer, OriginalType value)

  proc readValue*[Reader](reader: var Reader, value: var Alias) =
    mixin readValue
    value = Alias reader.readValue(OriginalType)