Restructure the yaml package.

pkg/yaml/lib/composer.dart

-// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-part of yaml;
-
-/// Takes a parsed YAML document (what the spec calls the "serialization tree")
-/// and resolves aliases, resolves tags, and parses scalars to produce the
-/// "representation graph".
-class _Composer extends _Visitor {
-  /// The root node of the serialization tree.
-  _Node root;
-
-  /// Map from anchor names to the most recent representation graph node with
-  /// that anchor.
-  Map<String, _Node> anchors;
-
-  /// The next id to use for the represenation graph's anchors. The spec doesn't
-  /// use anchors in the representation graph, but we do so that the constructor
-  /// can ensure that the same node in the representation graph produces the
-  /// same native object.
-  int idCounter;
-
-  _Composer(this.root) : this.anchors = <String, _Node>{}, this.idCounter = 0;
-
-  /// Runs the Composer to produce a representation graph.
-  _Node compose() => root.visit(this);
-
-  /// Returns the anchor to which an alias node refers.
-  _Node visitAlias(_AliasNode alias) {
-    if (!anchors.containsKey(alias.anchor)) {
-      throw new YamlException("no anchor for alias ${alias.anchor}");
-    }
-    return anchors[alias.anchor];
-  }
-
-  /// Parses a scalar node according to its tag, or auto-detects the type if no
-  /// tag exists. Currently this only supports the YAML core type schema.
-  _Node visitScalar(_ScalarNode scalar) {
-    if (scalar.tag.name == "!") {
-      return setAnchor(scalar, parseString(scalar.content));
-    } else if (scalar.tag.name == "?") {
-      for (var fn in [parseNull, parseBool, parseInt, parseFloat]) {
-        var result = fn(scalar.content);
-        if (result != null) return result;
-      }
-      return setAnchor(scalar, parseString(scalar.content));
-    }
-
-    // TODO(nweiz): support the full YAML type repository
-    var tagParsers = {
-      'null': parseNull, 'bool': parseBool, 'int': parseInt,
-      'float': parseFloat, 'str': parseString
-    };
-
-    for (var key in tagParsers.keys) {
-      if (scalar.tag.name != _Tag.yaml(key)) continue;
-      var result = tagParsers[key](scalar.content);
-      if (result != null) return setAnchor(scalar, result);
-      throw new YamlException('invalid literal for $key: "${scalar.content}"');
-    }
-
-    throw new YamlException('undefined tag: "${scalar.tag.name}"');
-  }
-
-  /// Assigns a tag to the sequence and recursively composes its contents.
-  _Node visitSequence(_SequenceNode seq) {
-    var tagName = seq.tag.name;
-    if (tagName != "!" && tagName != "?" && tagName != _Tag.yaml("seq")) {
-      throw new YamlException("invalid tag for sequence: ${tagName}");
-    }
-
-    var result = setAnchor(seq, new _SequenceNode(_Tag.yaml("seq"), null));
-    result.content = super.visitSequence(seq);
-    return result;
-  }
-
-  /// Assigns a tag to the mapping and recursively composes its contents.
-  _Node visitMapping(_MappingNode map) {
-    var tagName = map.tag.name;
-    if (tagName != "!" && tagName != "?" && tagName != _Tag.yaml("map")) {
-      throw new YamlException("invalid tag for mapping: ${tagName}");
-    }
-
-    var result = setAnchor(map, new _MappingNode(_Tag.yaml("map"), null));
-    result.content = super.visitMapping(map);
-    return result;
-  }
-
-  /// If the serialization tree node [anchored] has an anchor, records that
-  /// that anchor is pointing to the representation graph node [result].
-  _Node setAnchor(_Node anchored, _Node result) {
-    if (anchored.anchor == null) return result;
-    result.anchor = '${idCounter++}';
-    anchors[anchored.anchor] = result;
-    return result;
-  }
-
-  /// Parses a null scalar.
-  _ScalarNode parseNull(String content) {
-    if (!new RegExp(r"^(null|Null|NULL|~|)$").hasMatch(content)) return null;
-    return new _ScalarNode(_Tag.yaml("null"), value: null);
-  }
-
-  /// Parses a boolean scalar.
-  _ScalarNode parseBool(String content) {
-    var match = new RegExp(r"^(?:(true|True|TRUE)|(false|False|FALSE))$").
-      firstMatch(content);
-    if (match == null) return null;
-    return new _ScalarNode(_Tag.yaml("bool"), value: match.group(1) != null);
-  }
-
-  /// Parses an integer scalar.
-  _ScalarNode parseInt(String content) {
-    var match = new RegExp(r"^[-+]?[0-9]+$").firstMatch(content);
-    if (match != null) {
-      return new _ScalarNode(_Tag.yaml("int"),
-          value: int.parse(match.group(0)));
-    }
-
-    match = new RegExp(r"^0o([0-7]+)$").firstMatch(content);
-    if (match != null) {
-      int n = int.parse(match.group(1), radix: 8);
-      return new _ScalarNode(_Tag.yaml("int"), value: n);
-    }
-
-    match = new RegExp(r"^0x[0-9a-fA-F]+$").firstMatch(content);
-    if (match != null) {
-      return new _ScalarNode(_Tag.yaml("int"),
-          value: int.parse(match.group(0)));
-    }
-
-    return null;
-  }
-
-  /// Parses a floating-point scalar.
-  _ScalarNode parseFloat(String content) {
-    var match = new RegExp(
-        r"^[-+]?(\.[0-9]+|[0-9]+(\.[0-9]*)?)([eE][-+]?[0-9]+)?$").
-      firstMatch(content);
-    if (match != null) {
-      // YAML allows floats of the form "0.", but Dart does not. Fix up those
-      // floats by removing the trailing dot.
-      var matchStr = match.group(0).replaceAll(new RegExp(r"\.$"), "");
-      return new _ScalarNode(_Tag.yaml("float"),
-          value: double.parse(matchStr));
-    }
-
-    match = new RegExp(r"^([+-]?)\.(inf|Inf|INF)$").firstMatch(content);
-    if (match != null) {
-      var value = match.group(1) == "-" ? -double.INFINITY : double.INFINITY;
-      return new _ScalarNode(_Tag.yaml("float"), value: value);
-    }
-
-    match = new RegExp(r"^\.(nan|NaN|NAN)$").firstMatch(content);
-    if (match != null) {
-      return new _ScalarNode(_Tag.yaml("float"), value: double.NAN);
-    }
-
-    return null;
-  }
-
-  /// Parses a string scalar.
-  _ScalarNode parseString(String content) =>
-    new _ScalarNode(_Tag.yaml("str"), value: content);
-}