NimYAML/private/dom.nim

#            NimYAML - YAML implementation in Nim
#        (c) Copyright 2015 Felix Krause
#
#    See the file "copying.txt", included in this
#    distribution, for details about the copyright.

proc newYamlNode*(content: string, tag: string = "?"): YamlNode =
  YamlNode(kind: yScalar, content: content, tag: tag)

proc newYamlNode*(children: openarray[YamlNode], tag: string = "?"):
    YamlNode =
  YamlNode(kind: ySequence, children: @children, tag: tag)

proc newYamlNode*(pairs: openarray[tuple[key, value: YamlNode]],
                  tag: string = "?"): YamlNode =
  YamlNode(kind: yMapping, pairs: @pairs, tag: tag)

proc initYamlDoc*(root: YamlNode): YamlDocument = result.root = root

proc composeNode(s: var YamlStream, tagLib: TagLibrary,
                 c: ConstructionContext):
    YamlNode {.raises: [YamlStreamError, YamlConstructionError].} =
  let start = s.next()
  new(result)
  try:
    case start.kind
    of yamlStartMap:
      result.tag = tagLib.uri(start.mapTag)
      result.kind = yMapping
      result.pairs = newSeq[tuple[key, value: YamlNode]]()
      while s.peek().kind != yamlEndMap:
        let
          key = composeNode(s, tagLib, c)
          value = composeNode(s, tagLib, c)
        result.pairs.add((key: key, value: value))
      discard s.next()
      if start.mapAnchor != yAnchorNone:
        assert(not c.refs.hasKey(start.mapAnchor))
        c.refs[start.mapAnchor] = cast[pointer](result)
    of yamlStartSeq:
      result.tag = tagLib.uri(start.seqTag)
      result.kind = ySequence
      result.children = newSeq[YamlNode]()
      while s.peek().kind != yamlEndSeq:
        result.children.add(composeNode(s, tagLib, c))
      if start.seqAnchor != yAnchorNone:
        assert(not c.refs.hasKey(start.seqAnchor))
        c.refs[start.seqAnchor] = cast[pointer](result)
      discard s.next()
    of yamlScalar:
      result.tag = tagLib.uri(start.scalarTag)
      result.kind = yScalar
      shallowCopy(result.content, start.scalarContent)
      if start.scalarAnchor != yAnchorNone:
        assert(not c.refs.hasKey(start.scalarAnchor))
        c.refs[start.scalarAnchor] = cast[pointer](result)
    of yamlAlias:
      result = cast[YamlNode](c.refs[start.aliasTarget])
    else: assert false, "Malformed YamlStream"
  except KeyError:
    raise newException(YamlConstructionError,
                       "Wrong tag library: TagId missing")

proc compose*(s: var YamlStream, tagLib: TagLibrary): YamlDocument
    {.raises: [YamlStreamError, YamlConstructionError].} =
  var context = newConstructionContext()
  assert s.next().kind == yamlStartDoc, "Malformed YamlStream"
  result.root = composeNode(s, tagLib, context)
  assert s.next().kind == yamlEndDoc, "Malformed YamlStream"

proc loadDOM*(s: Stream): YamlDocument
    {.raises: [IOError, YamlParserError, YamlConstructionError].} =
  var
    tagLib = initExtendedTagLibrary()
    parser = newYamlParser(tagLib)
    events = parser.parse(s)
  try: result = compose(events, tagLib)
  except YamlStreamError:
    let e = getCurrentException()
    if e.parent of YamlParserError:
      raise (ref YamlParserError)(e.parent)
    elif e.parent of IOError:
      raise (ref IOError)(e.parent)
    else: assert false, "Never happens: " & e.parent.repr

proc serializeNode(n: YamlNode, c: SerializationContext, a: AnchorStyle,
                   tagLib: TagLibrary): RawYamlStream {.raises: [].}=
  let p = cast[pointer](n)
  if a != asNone and c.refs.hasKey(p):
    try:
      if c.refs[p] == yAnchorNone:
        c.refs[p] = c.nextAnchorId
        c.nextAnchorId = AnchorId(int(c.nextAnchorId) + 1)
    except KeyError: assert false, "Can never happen"
    result = iterator(): YamlStreamEvent {.raises: [].} =
      var event: YamlStreamEvent
      try: event = aliasEvent(c.refs[p])
      except KeyError: assert false, "Can never happen"
      yield event
    return
  var
    tagId: TagId
    anchor: AnchorId
  try:
    if a == asAlways:
      c.refs[p] = c.nextAnchorId
      c.nextAnchorId = AnchorId(int(c.nextAnchorId) + 1)
    else: c.refs[p] = yAnchorNone
    tagId = if tagLib.tags.hasKey(n.tag): tagLib.tags[n.tag] else:
            tagLib.registerUri(n.tag)
    case a
    of asNone: anchor = yAnchorNone
    of asTidy: anchor = cast[AnchorId](n)
    of asAlways: anchor = c.refs[p]
  except KeyError: assert false, "Can never happen"
  result = iterator(): YamlStreamEvent =
    case n.kind
    of yScalar: yield scalarEvent(n.content, tagId, anchor)
    of ySequence:
      yield startSeqEvent(tagId, anchor)
      for item in n.children:
        var events = serializeNode(item, c, a, tagLib)
        while true:
          let event = events()
          if finished(events): break
          yield event
      yield endSeqEvent()
    of yMapping:
      yield startMapEvent(tagId, anchor)
      for i in n.pairs:
        var events = serializeNode(i.key, c, a, tagLib)
        while true:
          let event = events()
          if finished(events): break
          yield event
        events = serializeNode(i.value, c, a, tagLib)
        while true:
          let event = events()
          if finished(events): break
          yield event
      yield endMapEvent()

template processAnchoredEvent(target: expr, c: SerializationContext): stmt =
  try:
    let anchorId = c.refs[cast[pointer](target)]
    if anchorId != yAnchorNone: target = anchorId
    else: target = yAnchorNone
  except KeyError: assert false, "Can never happen"
  yield event

proc serialize*(doc: YamlDocument, tagLib: TagLibrary, a: AnchorStyle = asTidy):
    YamlStream {.raises: [].} =
  var
    context = newSerializationContext(a)
    events = serializeNode(doc.root, context, a, tagLib)
  if a == asTidy:
    var backend = iterator(): YamlStreamEvent {.raises: [].} =
      var output = newSeq[YamlStreamEvent]()
      while true:
        let event = events()
        if finished(events): break
        output.add(event)
      yield startDocEvent()
      for event in output.mitems():
        case event.kind
        of yamlScalar: processAnchoredEvent(event.scalarAnchor, context)
        of yamlStartMap: processAnchoredEvent(event.mapAnchor, context)
        of yamlStartSeq: processAnchoredEvent(event.seqAnchor, context)
        else: yield event
      yield endDocEvent()
    result = initYamlStream(backend)
  else:
    var backend = iterator(): YamlStreamEvent {.raises: [].} =
      yield startDocEvent()
      while true:
        let event = events()
        if finished(events): break
        yield event
      yield endDocEvent()
    result = initYamlStream(backend)

proc dumpDOM*(doc: YamlDocument, target: Stream,
              anchorStyle: AnchorStyle = asTidy,
              options: PresentationOptions = defaultPresentationOptions)
    {.raises: [YamlPresenterJsonError, YamlPresenterOutputError].} =
  ## Dump a YamlDocument as YAML character stream.
  var
    tagLib = initExtendedTagLibrary()
    events = serialize(doc, tagLib,
                       if options.style == psJson: asNone else: anchorStyle)
  try:
    present(events, target, tagLib, options)
  except YamlStreamError:
    # serializing object does not raise any errors, so we can ignore this
    assert false, "Can never happen"