text: 'use strict';
  
  /*eslint-disable no-use-before-define*/
  
  var common              = require('./common');
  var YAMLException       = require('./exception');
  var DEFAULT_FULL_SCHEMA = require('./schema/default_full');
  var DEFAULT_SAFE_SCHEMA = require('./schema/default_safe');
  
  var _toString       = Object.prototype.toString;
  var _hasOwnProperty = Object.prototype.hasOwnProperty;
  
  var CHAR_TAB                  = 0x09; /* Tab */
  var CHAR_LINE_FEED            = 0x0A; /* LF */
  var CHAR_SPACE                = 0x20; /* Space */
  var CHAR_EXCLAMATION          = 0x21; /* ! */
  var CHAR_DOUBLE_QUOTE         = 0x22; /* " */
  var CHAR_SHARP                = 0x23; /* # */
  var CHAR_PERCENT              = 0x25; /* % */
  var CHAR_AMPERSAND            = 0x26; /* & */
  var CHAR_SINGLE_QUOTE         = 0x27; /* ' */
  var CHAR_ASTERISK             = 0x2A; /* * */
  var CHAR_COMMA                = 0x2C; /* , */
  var CHAR_MINUS                = 0x2D; /* - */
  var CHAR_COLON                = 0x3A; /* : */
  var CHAR_GREATER_THAN         = 0x3E; /* > */
  var CHAR_QUESTION             = 0x3F; /* ? */
  var CHAR_COMMERCIAL_AT        = 0x40; /* @ */
  var CHAR_LEFT_SQUARE_BRACKET  = 0x5B; /* [ */
  var CHAR_RIGHT_SQUARE_BRACKET = 0x5D; /* ] */
  var CHAR_GRAVE_ACCENT         = 0x60; /* ` */
  var CHAR_LEFT_CURLY_BRACKET   = 0x7B; /* { */
  var CHAR_VERTICAL_LINE        = 0x7C; /* | */
  var CHAR_RIGHT_CURLY_BRACKET  = 0x7D; /* } */
  
  var ESCAPE_SEQUENCES = {};
  
  ESCAPE_SEQUENCES[0x00]   = '\\0';
  ESCAPE_SEQUENCES[0x07]   = '\\a';
  ESCAPE_SEQUENCES[0x08]   = '\\b';
  ESCAPE_SEQUENCES[0x09]   = '\\t';
  ESCAPE_SEQUENCES[0x0A]   = '\\n';
  ESCAPE_SEQUENCES[0x0B]   = '\\v';
  ESCAPE_SEQUENCES[0x0C]   = '\\f';
  ESCAPE_SEQUENCES[0x0D]   = '\\r';
  ESCAPE_SEQUENCES[0x1B]   = '\\e';
  ESCAPE_SEQUENCES[0x22]   = '\\"';
  ESCAPE_SEQUENCES[0x5C]   = '\\\\';
  ESCAPE_SEQUENCES[0x85]   = '\\N';
  ESCAPE_SEQUENCES[0xA0]   = '\\_';
  ESCAPE_SEQUENCES[0x2028] = '\\L';
  ESCAPE_SEQUENCES[0x2029] = '\\P';
  
  var DEPRECATED_BOOLEANS_SYNTAX = [
    'y', 'Y', 'yes', 'Yes', 'YES', 'on', 'On', 'ON',
    'n', 'N', 'no', 'No', 'NO', 'off', 'Off', 'OFF'
  ];
  
  function compileStyleMap(schema, map) {
    var result, keys, index, length, tag, style, type;
  
    if (map === null) return {};
  
    result = {};
    keys = Object.keys(map);
  
    for (index = 0, length = keys.length; index < length; index += 1) {
      tag = keys[index];
      style = String(map[tag]);
  
      if (tag.slice(0, 2) === '!!') {
        tag = 'tag:yaml.org,2002:' + tag.slice(2);
      }
      type = schema.compiledTypeMap['fallback'][tag];
  
      if (type && _hasOwnProperty.call(type.styleAliases, style)) {
        style = type.styleAliases[style];
      }
  
      result[tag] = style;
    }
  
    return result;
  }
  
  function encodeHex(character) {
    var string, handle, length;
  
    string = character.toString(16).toUpperCase();
  
    if (character <= 0xFF) {
      handle = 'x';
      length = 2;
    } else if (character <= 0xFFFF) {
      handle = 'u';
      length = 4;
    } else if (character <= 0xFFFFFFFF) {
      handle = 'U';
      length = 8;
    } else {
      throw new YAMLException('code point within a string may not be greater than 0xFFFFFFFF');
    }
  
    return '\\' + handle + common.repeat('0', length - string.length) + string;
  }
  
  function State(options) {
    this.schema       = options['schema'] || DEFAULT_FULL_SCHEMA;
    this.indent       = Math.max(1, (options['indent'] || 2));
    this.skipInvalid  = options['skipInvalid'] || false;
    this.flowLevel    = (common.isNothing(options['flowLevel']) ? -1 : options['flowLevel']);
    this.styleMap     = compileStyleMap(this.schema, options['styles'] || null);
    this.sortKeys     = options['sortKeys'] || false;
    this.lineWidth    = options['lineWidth'] || 80;
    this.noRefs       = options['noRefs'] || false;
    this.noCompatMode = options['noCompatMode'] || false;
  
    this.implicitTypes = this.schema.compiledImplicit;
    this.explicitTypes = this.schema.compiledExplicit;
  
    this.tag = null;
    this.result = '';
  
    this.duplicates = [];
    this.usedDuplicates = null;
  }
  
  // Indents every line in a string. Empty lines (\n only) are not indented.
  function indentString(string, spaces) {
    var ind = common.repeat(' ', spaces),
        position = 0,
        next = -1,
        result = '',
        line,
        length = string.length;
  
    while (position < length) {
      next = string.indexOf('\n', position);
      if (next === -1) {
        line = string.slice(position);
        position = length;
      } else {
        line = string.slice(position, next + 1);
        position = next + 1;
      }
  
      if (line.length && line !== '\n') result += ind;
  
      result += line;
    }
  
    return result;
  }
  
  function generateNextLine(state, level) {
    return '\n' + common.repeat(' ', state.indent * level);
  }
  
  function testImplicitResolving(state, str) {
    var index, length, type;
  
    for (index = 0, length = state.implicitTypes.length; index < length; index += 1) {
      type = state.implicitTypes[index];
  
      if (type.resolve(str)) {
        return true;
      }
    }
  
    return false;
  }
  
  // [33] s-white ::= s-space | s-tab
  function isWhitespace(c) {
    return c === CHAR_SPACE || c === CHAR_TAB;
  }
  
  // Returns true if the character can be printed without escaping.
  // From YAML 1.2: "any allowed characters known to be non-printable
  // should also be escaped. [However,] This isn’t mandatory"
  // Derived from nb-char - \t - #x85 - #xA0 - #x2028 - #x2029.
  function isPrintable(c) {
    return  (0x00020 <= c && c <= 0x00007E)
        || ((0x000A1 <= c && c <= 0x00D7FF) && c !== 0x2028 && c !== 0x2029)
        || ((0x0E000 <= c && c <= 0x00FFFD) && c !== 0xFEFF /* BOM */)
        ||  (0x10000 <= c && c <= 0x10FFFF);
  }
  
  // Simplified test for values allowed after the first character in plain style.
  function isPlainSafe(c) {
    // Uses a subset of nb-char - c-flow-indicator - ":" - "#"
    // where nb-char ::= c-printable - b-char - c-byte-order-mark.
    return isPrintable(c) && c !== 0xFEFF
      // - c-flow-indicator
      && c !== CHAR_COMMA
      && c !== CHAR_LEFT_SQUARE_BRACKET
      && c !== CHAR_RIGHT_SQUARE_BRACKET
      && c !== CHAR_LEFT_CURLY_BRACKET
      && c !== CHAR_RIGHT_CURLY_BRACKET
      // - ":" - "#"
      && c !== CHAR_COLON
      && c !== CHAR_SHARP;
  }
  
  // Simplified test for values allowed as the first character in plain style.
  function isPlainSafeFirst(c) {
    // Uses a subset of ns-char - c-indicator
    // where ns-char = nb-char - s-white.
    return isPrintable(c) && c !== 0xFEFF
      && !isWhitespace(c) // - s-white
      // - (c-indicator ::=
      // “-” | “?” | “:” | “,” | “[” | “]” | “{” | “}”
      && c !== CHAR_MINUS
      && c !== CHAR_QUESTION
      && c !== CHAR_COLON
      && c !== CHAR_COMMA
      && c !== CHAR_LEFT_SQUARE_BRACKET
      && c !== CHAR_RIGHT_SQUARE_BRACKET
      && c !== CHAR_LEFT_CURLY_BRACKET
      && c !== CHAR_RIGHT_CURLY_BRACKET
      // | “#” | “&” | “*” | “!” | “|” | “>” | “'” | “"”
      && c !== CHAR_SHARP
      && c !== CHAR_AMPERSAND
      && c !== CHAR_ASTERISK
      && c !== CHAR_EXCLAMATION
      && c !== CHAR_VERTICAL_LINE
      && c !== CHAR_GREATER_THAN
      && c !== CHAR_SINGLE_QUOTE
      && c !== CHAR_DOUBLE_QUOTE
      // | “%” | “@” | “`”)
      && c !== CHAR_PERCENT
      && c !== CHAR_COMMERCIAL_AT
      && c !== CHAR_GRAVE_ACCENT;
  }
  
  var STYLE_PLAIN   = 1,
      STYLE_SINGLE  = 2,
      STYLE_LITERAL = 3,
      STYLE_FOLDED  = 4,
      STYLE_DOUBLE  = 5;
  
  // Determines which scalar styles are possible and returns the preferred style.
  // lineWidth = -1 => no limit.
  // Pre-conditions: str.length > 0.
  // Post-conditions:
  //    STYLE_PLAIN or STYLE_SINGLE => no \n are in the string.
  //    STYLE_LITERAL => no lines are suitable for folding (or lineWidth is -1).
  //    STYLE_FOLDED => a line > lineWidth and can be folded (and lineWidth != -1).
  function chooseScalarStyle(string, singleLineOnly, indentPerLevel, lineWidth, testAmbiguousType) {
    var i;
    var char;
    var hasLineBreak = false;
    var hasFoldableLine = false; // only checked if shouldTrackWidth
    var shouldTrackWidth = lineWidth !== -1;
    var previousLineBreak = -1; // count the first line correctly
    var plain = isPlainSafeFirst(string.charCodeAt(0))
            && !isWhitespace(string.charCodeAt(string.length - 1));
  
    if (singleLineOnly) {
      // Case: no block styles.
      // Check for disallowed characters to rule out plain and single.
      for (i = 0; i < string.length; i++) {
        char = string.charCodeAt(i);
        if (!isPrintable(char)) {
          return STYLE_DOUBLE;
        }
        plain = plain && isPlainSafe(char);
      }
    } else {
      // Case: block styles permitted.
      for (i = 0; i < string.length; i++) {
        char = string.charCodeAt(i);
        if (char === CHAR_LINE_FEED) {
          hasLineBreak = true;
          // Check if any line can be folded.
          if (shouldTrackWidth) {
            hasFoldableLine = hasFoldableLine ||
              // Foldable line = too long, and not more-indented.
              (i - previousLineBreak - 1 > lineWidth &&
               string[previousLineBreak + 1] !== ' ');
            previousLineBreak = i;
          }
        } else if (!isPrintable(char)) {
          return STYLE_DOUBLE;
        }
        plain = plain && isPlainSafe(char);
      }
      // in case the end is missing a \n
      hasFoldableLine = hasFoldableLine || (shouldTrackWidth &&
        (i - previousLineBreak - 1 > lineWidth &&
         string[previousLineBreak + 1] !== ' '));
    }
    // Although every style can represent \n without escaping, prefer block styles
    // for multiline, since they're more readable and they don't add empty lines.
    // Also prefer folding a super-long line.
    if (!hasLineBreak && !hasFoldableLine) {
      // Strings interpretable as another type have to be quoted;
      // e.g. the string 'true' vs. the boolean true.
      return plain && !testAmbiguousType(string)
        ? STYLE_PLAIN : STYLE_SINGLE;
    }
    // Edge case: block indentation indicator can only have one digit.
    if (string[0] === ' ' && indentPerLevel > 9) {
      return STYLE_DOUBLE;
    }
    // At this point we know block styles are valid.
    // Prefer literal style unless we want to fold.
    return hasFoldableLine ? STYLE_FOLDED : STYLE_LITERAL;
  }
  
  // Note: line breaking/folding is implemented for only the folded style.
  // NB. We drop the last trailing newline (if any) of a returned block scalar
  //  since the dumper adds its own newline. This always works:
  //    • No ending newline => unaffected; already using strip "-" chomping.
  //    • Ending newline    => removed then restored.
  //  Importantly, this keeps the "+" chomp indicator from gaining an extra line.
  function writeScalar(state, string, level, iskey) {
    state.dump = (function () {
      if (string.length === 0) {
        return "''";
      }
      if (!state.noCompatMode &&
          DEPRECATED_BOOLEANS_SYNTAX.indexOf(string) !== -1) {
        return "'" + string + "'";
      }
  
      var indent = state.indent * Math.max(1, level); // no 0-indent scalars
      // As indentation gets deeper, let the width decrease monotonically
      // to the lower bound min(state.lineWidth, 40).
      // Note that this implies
      //  state.lineWidth ≤ 40 + state.indent: width is fixed at the lower bound.
      //  state.lineWidth > 40 + state.indent: width decreases until the lower bound.
      // This behaves better than a constant minimum width which disallows narrower options,
      // or an indent threshold which causes the width to suddenly increase.
      var lineWidth = state.lineWidth === -1
        ? -1 : Math.max(Math.min(state.lineWidth, 40), state.lineWidth - indent);
  
      // Without knowing if keys are implicit/explicit, assume implicit for safety.
      var singleLineOnly = iskey
        // No block styles in flow mode.
        || (state.flowLevel > -1 && level >= state.flowLevel);
      function testAmbiguity(string) {
        return testImplicitResolving(state, string);
      }
  
      switch (chooseScalarStyle(string, singleLineOnly, state.indent, lineWidth, testAmbiguity)) {
        case STYLE_PLAIN:
          return string;
        case STYLE_SINGLE:
          return "'" + string.replace(/'/g, "''") + "'";
        case STYLE_LITERAL:
          return '|' + blockHeader(string, state.indent)
            + dropEndingNewline(indentString(string, indent));
        case STYLE_FOLDED:
          return '>' + blockHeader(string, state.indent)
            + dropEndingNewline(indentString(foldString(string, lineWidth), indent));
        case STYLE_DOUBLE:
          return '"' + escapeString(string, lineWidth) + '"';
        default:
          throw new YAMLException('impossible error: invalid scalar style');
      }
    }());
  }
  
  // Pre-conditions: string is valid for a block scalar, 1 <= indentPerLevel <= 9.
  function blockHeader(string, indentPerLevel) {
    var indentIndicator = (string[0] === ' ') ? String(indentPerLevel) : '';
  
    // note the special case: the string '\n' counts as a "trailing" empty line.
    var clip =          string[string.length - 1] === '\n';
    var keep = clip && (string[string.length - 2] === '\n' || string === '\n');
    var chomp = keep ? '+' : (clip ? '' : '-');
  
    return indentIndicator + chomp + '\n';
  }
  
  // (See the note for writeScalar.)
  function dropEndingNewline(string) {
    return string[string.length - 1] === '\n' ? string.slice(0, -1) : string;
  }
  
  // Note: a long line without a suitable break point will exceed the width limit.
  // Pre-conditions: every char in str isPrintable, str.length > 0, width > 0.
  function foldString(string, width) {
    // In folded style, $k$ consecutive newlines output as $k+1$ newlines—
    // unless they're before or after a more-indented line, or at the very
    // beginning or end, in which case $k$ maps to $k$.
    // Therefore, parse each chunk as newline(s) followed by a content line.
    var lineRe = /(\n+)([^\n]*)/g;
  
    // first line (possibly an empty line)
    var result = (function () {
      var nextLF = string.indexOf('\n');
      nextLF = nextLF !== -1 ? nextLF : string.length;
      lineRe.lastIndex = nextLF;
      return foldLine(string.slice(0, nextLF), width);
    }());
    // If we haven't reached the first content line yet, don't add an extra \n.
    var prevMoreIndented = string[0] === '\n' || string[0] === ' ';
    var moreIndented;
  
    // rest of the lines
    var match;
    while ((match = lineRe.exec(string))) {
      var prefix = match[1], line = match[2];
      moreIndented = (line[0] === ' ');
      result += prefix
        + (!prevMoreIndented && !moreIndented && line !== ''
          ? '\n' : '')
        + foldLine(line, width);
      prevMoreIndented = moreIndented;
    }
  
    return result;
  }
  
  // Greedy line breaking.
  // Picks the longest line under the limit each time,
  // otherwise settles for the shortest line over the limit.
  // NB. More-indented lines *cannot* be folded, as that would add an extra \n.
  function foldLine(line, width) {
    if (line === '' || line[0] === ' ') return line;
  
    // Since a more-indented line adds a \n, breaks can't be followed by a space.
    var breakRe = / [^ ]/g; // note: the match index will always be <= length-2.
    var match;
    // start is an inclusive index. end, curr, and next are exclusive.
    var start = 0, end, curr = 0, next = 0;
    var result = '';
  
    // Invariants: 0 <= start <= length-1.
    //   0 <= curr <= next <= max(0, length-2). curr - start <= width.
    // Inside the loop:
    //   A match implies length >= 2, so curr and next are <= length-2.
    while ((match = breakRe.exec(line))) {
      next = match.index;
      // maintain invariant: curr - start <= width
      if (next - start > width) {
        end = (curr > start) ? curr : next; // derive end <= length-2
        result += '\n' + line.slice(start, end);
        // skip the space that was output as \n
        start = end + 1;                    // derive start <= length-1
      }
      curr = next;
    }
  
    // By the invariants, start <= length-1, so there is something left over.
    // It is either the whole string or a part starting from non-whitespace.
    result += '\n';
    // Insert a break if the remainder is too long and there is a break available.
    if (line.length - start > width && curr > start) {
      result += line.slice(start, curr) + '\n' + line.slice(curr + 1);
    } else {
      result += line.slice(start);
    }
  
    return result.slice(1); // drop extra \n joiner
  }
  
  // Escapes a double-quoted string.
  function escapeString(string) {
    var result = '';
    var char;
    var escapeSeq;
  
    for (var i = 0; i < string.length; i++) {
      char = string.charCodeAt(i);
      escapeSeq = ESCAPE_SEQUENCES[char];
      result += !escapeSeq && isPrintable(char)
        ? string[i]
        : escapeSeq || encodeHex(char);
    }
  
    return result;
  }
  
  function writeFlowSequence(state, level, object) {
    var _result = '',
        _tag    = state.tag,
        index,
        length;
  
    for (index = 0, length = object.length; index < length; index += 1) {
      // Write only valid elements.
      if (writeNode(state, level, object[index], false, false)) {
        if (index !== 0) _result += ', ';
        _result += state.dump;
      }
    }
  
    state.tag = _tag;
    state.dump = '[' + _result + ']';
  }
  
  function writeBlockSequence(state, level, object, compact) {
    var _result = '',
        _tag    = state.tag,
        index,
        length;
  
    for (index = 0, length = object.length; index < length; index += 1) {
      // Write only valid elements.
      if (writeNode(state, level + 1, object[index], true, true)) {
        if (!compact || index !== 0) {
          _result += generateNextLine(state, level);
        }
        _result += '- ' + state.dump;
      }
    }
  
    state.tag = _tag;
    state.dump = _result || '[]'; // Empty sequence if no valid values.
  }
  
  function writeFlowMapping(state, level, object) {
    var _result       = '',
        _tag          = state.tag,
        objectKeyList = Object.keys(object),
        index,
        length,
        objectKey,
        objectValue,
        pairBuffer;
  
    for (index = 0, length = objectKeyList.length; index < length; index += 1) {
      pairBuffer = '';
  
      if (index !== 0) pairBuffer += ', ';
  
      objectKey = objectKeyList[index];
      objectValue = object[objectKey];
  
      if (!writeNode(state, level, objectKey, false, false)) {
        continue; // Skip this pair because of invalid key;
      }
  
      if (state.dump.length > 1024) pairBuffer += '? ';
  
      pairBuffer += state.dump + ': ';
  
      if (!writeNode(state, level, objectValue, false, false)) {
        continue; // Skip this pair because of invalid value.
      }
  
      pairBuffer += state.dump;
  
      // Both key and value are valid.
      _result += pairBuffer;
    }
  
    state.tag = _tag;
    state.dump = '{' + _result + '}';
  }
  
  function writeBlockMapping(state, level, object, compact) {
    var _result       = '',
        _tag          = state.tag,
        objectKeyList = Object.keys(object),
        index,
        length,
        objectKey,
        objectValue,
        explicitPair,
        pairBuffer;
  
    // Allow sorting keys so that the output file is deterministic
    if (state.sortKeys === true) {
      // Default sorting
      objectKeyList.sort();
    } else if (typeof state.sortKeys === 'function') {
      // Custom sort function
      objectKeyList.sort(state.sortKeys);
    } else if (state.sortKeys) {
      // Something is wrong
      throw new YAMLException('sortKeys must be a boolean or a function');
    }
  
    for (index = 0, length = objectKeyList.length; index < length; index += 1) {
      pairBuffer = '';
  
      if (!compact || index !== 0) {
        pairBuffer += generateNextLine(state, level);
      }
  
      objectKey = objectKeyList[index];
      objectValue = object[objectKey];
  
      if (!writeNode(state, level + 1, objectKey, true, true, true)) {
        continue; // Skip this pair because of invalid key.
      }
  
      explicitPair = (state.tag !== null && state.tag !== '?') ||
                     (state.dump && state.dump.length > 1024);
  
      if (explicitPair) {
        if (state.dump && CHAR_LINE_FEED === state.dump.charCodeAt(0)) {
          pairBuffer += '?';
        } else {
          pairBuffer += '? ';
        }
      }
  
      pairBuffer += state.dump;
  
      if (explicitPair) {
        pairBuffer += generateNextLine(state, level);
      }
  
      if (!writeNode(state, level + 1, objectValue, true, explicitPair)) {
        continue; // Skip this pair because of invalid value.
      }
  
      if (state.dump && CHAR_LINE_FEED === state.dump.charCodeAt(0)) {
        pairBuffer += ':';
      } else {
        pairBuffer += ': ';
      }
  
      pairBuffer += state.dump;
  
      // Both key and value are valid.
      _result += pairBuffer;
    }
  
    state.tag = _tag;
    state.dump = _result || '{}'; // Empty mapping if no valid pairs.
  }
  
  function detectType(state, object, explicit) {
    var _result, typeList, index, length, type, style;
  
    typeList = explicit ? state.explicitTypes : state.implicitTypes;
  
    for (index = 0, length = typeList.length; index < length; index += 1) {
      type = typeList[index];
  
      if ((type.instanceOf  || type.predicate) &&
          (!type.instanceOf || ((typeof object === 'object') && (object instanceof type.instanceOf))) &&
          (!type.predicate  || type.predicate(object))) {
  
        state.tag = explicit ? type.tag : '?';
  
        if (type.represent) {
          style = state.styleMap[type.tag] || type.defaultStyle;
  
          if (_toString.call(type.represent) === '[object Function]') {
            _result = type.represent(object, style);
          } else if (_hasOwnProperty.call(type.represent, style)) {
            _result = type.represent[style](object, style);
          } else {
            throw new YAMLException('!<' + type.tag + '> tag resolver accepts not "' + style + '" style');
          }
  
          state.dump = _result;
        }
  
        return true;
      }
    }
  
    return false;
  }
  
  // Serializes `object` and writes it to global `result`.
  // Returns true on success, or false on invalid object.
  //
  function writeNode(state, level, object, block, compact, iskey) {
    state.tag = null;
    state.dump = object;
  
    if (!detectType(state, object, false)) {
      detectType(state, object, true);
    }
  
    var type = _toString.call(state.dump);
  
    if (block) {
      block = (state.flowLevel < 0 || state.flowLevel > level);
    }
  
    var objectOrArray = type === '[object Object]' || type === '[object Array]',
        duplicateIndex,
        duplicate;
  
    if (objectOrArray) {
      duplicateIndex = state.duplicates.indexOf(object);
      duplicate = duplicateIndex !== -1;
    }
  
    if ((state.tag !== null && state.tag !== '?') || duplicate || (state.indent !== 2 && level > 0)) {
      compact = false;
    }
  
    if (duplicate && state.usedDuplicates[duplicateIndex]) {
      state.dump = '*ref_' + duplicateIndex;
    } else {
      if (objectOrArray && duplicate && !state.usedDuplicates[duplicateIndex]) {
        state.usedDuplicates[duplicateIndex] = true;
      }
      if (type === '[object Object]') {
        if (block && (Object.keys(state.dump).length !== 0)) {
          writeBlockMapping(state, level, state.dump, compact);
          if (duplicate) {
            state.dump = '&ref_' + duplicateIndex + state.dump;
          }
        } else {
          writeFlowMapping(state, level, state.dump);
          if (duplicate) {
            state.dump = '&ref_' + duplicateIndex + ' ' + state.dump;
          }
        }
      } else if (type === '[object Array]') {
        if (block && (state.dump.length !== 0)) {
          writeBlockSequence(state, level, state.dump, compact);
          if (duplicate) {
            state.dump = '&ref_' + duplicateIndex + state.dump;
          }
        } else {
          writeFlowSequence(state, level, state.dump);
          if (duplicate) {
            state.dump = '&ref_' + duplicateIndex + ' ' + state.dump;
          }
        }
      } else if (type === '[object String]') {
        if (state.tag !== '?') {
          writeScalar(state, state.dump, level, iskey);
        }
      } else {
        if (state.skipInvalid) return false;
        throw new YAMLException('unacceptable kind of an object to dump ' + type);
      }
  
      if (state.tag !== null && state.tag !== '?') {
        state.dump = '!<' + state.tag + '> ' + state.dump;
      }
    }
  
    return true;
  }
  
  function getDuplicateReferences(object, state) {
    var objects = [],
        duplicatesIndexes = [],
        index,
        length;
  
    inspectNode(object, objects, duplicatesIndexes);
  
    for (index = 0, length = duplicatesIndexes.length; index < length; index += 1) {
      state.duplicates.push(objects[duplicatesIndexes[index]]);
    }
    state.usedDuplicates = new Array(length);
  }
  
  function inspectNode(object, objects, duplicatesIndexes) {
    var objectKeyList,
        index,
        length;
  
    if (object !== null && typeof object === 'object') {
      index = objects.indexOf(object);
      if (index !== -1) {
        if (duplicatesIndexes.indexOf(index) === -1) {
          duplicatesIndexes.push(index);
        }
      } else {
        objects.push(object);
  
        if (Array.isArray(object)) {
          for (index = 0, length = object.length; index < length; index += 1) {
            inspectNode(object[index], objects, duplicatesIndexes);
          }
        } else {
          objectKeyList = Object.keys(object);
  
          for (index = 0, length = objectKeyList.length; index < length; index += 1) {
            inspectNode(object[objectKeyList[index]], objects, duplicatesIndexes);
          }
        }
      }
    }
  }
  
  function dump(input, options) {
    options = options || {};
  
    var state = new State(options);
  
    if (!state.noRefs) getDuplicateReferences(input, state);
  
    if (writeNode(state, 0, input, true, true)) return state.dump + '\n';
  
    return '';
  }
  
  function safeDump(input, options) {
    return dump(input, common.extend({ schema: DEFAULT_SAFE_SCHEMA }, options));
  }
  
  module.exports.dump     = dump;
  module.exports.safeDump = safeDump;
  