Helmet.js

'use strict';

Object.defineProperty(exports, '__esModule', { value: true });

function _interopDefault (ex) { return (ex && (typeof ex === 'object') && 'default' in ex) ? ex['default'] : ex; }

var PropTypes = _interopDefault(require('prop-types'));
var withSideEffect = _interopDefault(require('react-side-effect'));
var isEqual = _interopDefault(require('react-fast-compare'));
var React = _interopDefault(require('react'));
var objectAssign = _interopDefault(require('object-assign'));

var ATTRIBUTE_NAMES = {
    BODY: "bodyAttributes",
    HTML: "htmlAttributes",
    TITLE: "titleAttributes"
};

var TAG_NAMES = {
    BASE: "base",
    BODY: "body",
    HEAD: "head",
    HTML: "html",
    LINK: "link",
    META: "meta",
    NOSCRIPT: "noscript",
    SCRIPT: "script",
    STYLE: "style",
    TITLE: "title"
};

var VALID_TAG_NAMES = Object.keys(TAG_NAMES).map(function (name) {
    return TAG_NAMES[name];
});

var TAG_PROPERTIES = {
    CHARSET: "charset",
    CSS_TEXT: "cssText",
    HREF: "href",
    HTTPEQUIV: "http-equiv",
    INNER_HTML: "innerHTML",
    ITEM_PROP: "itemprop",
    NAME: "name",
    PROPERTY: "property",
    REL: "rel",
    SRC: "src"
};

var REACT_TAG_MAP = {
    accesskey: "accessKey",
    charset: "charSet",
    class: "className",
    contenteditable: "contentEditable",
    contextmenu: "contextMenu",
    "http-equiv": "httpEquiv",
    itemprop: "itemProp",
    tabindex: "tabIndex"
};

var HELMET_PROPS = {
    DEFAULT_TITLE: "defaultTitle",
    DEFER: "defer",
    ENCODE_SPECIAL_CHARACTERS: "encodeSpecialCharacters",
    ON_CHANGE_CLIENT_STATE: "onChangeClientState",
    TITLE_TEMPLATE: "titleTemplate"
};

var HTML_TAG_MAP = Object.keys(REACT_TAG_MAP).reduce(function (obj, key) {
    obj[REACT_TAG_MAP[key]] = key;
    return obj;
}, {});

var SELF_CLOSING_TAGS = [TAG_NAMES.NOSCRIPT, TAG_NAMES.SCRIPT, TAG_NAMES.STYLE];

var HELMET_ATTRIBUTE = "data-react-helmet";

var _typeof = typeof Symbol === "function" && typeof Symbol.iterator === "symbol" ? function (obj) {
  return typeof obj;
} : function (obj) {
  return obj && typeof Symbol === "function" && obj.constructor === Symbol && obj !== Symbol.prototype ? "symbol" : typeof obj;
};

var classCallCheck = function (instance, Constructor) {
  if (!(instance instanceof Constructor)) {
    throw new TypeError("Cannot call a class as a function");
  }
};

var createClass = function () {
  function defineProperties(target, props) {
    for (var i = 0; i < props.length; i++) {
      var descriptor = props[i];
      descriptor.enumerable = descriptor.enumerable || false;
      descriptor.configurable = true;
      if ("value" in descriptor) descriptor.writable = true;
      Object.defineProperty(target, descriptor.key, descriptor);
    }
  }

  return function (Constructor, protoProps, staticProps) {
    if (protoProps) defineProperties(Constructor.prototype, protoProps);
    if (staticProps) defineProperties(Constructor, staticProps);
    return Constructor;
  };
}();

var _extends = Object.assign || function (target) {
  for (var i = 1; i < arguments.length; i++) {
    var source = arguments[i];

    for (var key in source) {
      if (Object.prototype.hasOwnProperty.call(source, key)) {
        target[key] = source[key];
      }
    }
  }

  return target;
};

var inherits = function (subClass, superClass) {
  if (typeof superClass !== "function" && superClass !== null) {
    throw new TypeError("Super expression must either be null or a function, not " + typeof superClass);
  }

  subClass.prototype = Object.create(superClass && superClass.prototype, {
    constructor: {
      value: subClass,
      enumerable: false,
      writable: true,
      configurable: true
    }
  });
  if (superClass) Object.setPrototypeOf ? Object.setPrototypeOf(subClass, superClass) : subClass.__proto__ = superClass;
};

var objectWithoutProperties = function (obj, keys) {
  var target = {};

  for (var i in obj) {
    if (keys.indexOf(i) >= 0) continue;
    if (!Object.prototype.hasOwnProperty.call(obj, i)) continue;
    target[i] = obj[i];
  }

  return target;
};

var possibleConstructorReturn = function (self, call) {
  if (!self) {
    throw new ReferenceError("this hasn't been initialised - super() hasn't been called");
  }

  return call && (typeof call === "object" || typeof call === "function") ? call : self;
};

var encodeSpecialCharacters = function encodeSpecialCharacters(str) {
    var encode = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : true;

    if (encode === false) {
        return String(str);
    }

    return String(str).replace(/&/g, "&amp;").replace(/</g, "&lt;").replace(/>/g, "&gt;").replace(/"/g, "&quot;").replace(/'/g, "&#x27;");
};

var getTitleFromPropsList = function getTitleFromPropsList(propsList) {
    var innermostTitle = getInnermostProperty(propsList, TAG_NAMES.TITLE);
    var innermostTemplate = getInnermostProperty(propsList, HELMET_PROPS.TITLE_TEMPLATE);

    if (innermostTemplate && innermostTitle) {
        // use function arg to avoid need to escape $ characters
        return innermostTemplate.replace(/%s/g, function () {
            return Array.isArray(innermostTitle) ? innermostTitle.join("") : innermostTitle;
        });
    }

    var innermostDefaultTitle = getInnermostProperty(propsList, HELMET_PROPS.DEFAULT_TITLE);

    return innermostTitle || innermostDefaultTitle || undefined;
};

var getOnChangeClientState = function getOnChangeClientState(propsList) {
    return getInnermostProperty(propsList, HELMET_PROPS.ON_CHANGE_CLIENT_STATE) || function () {};
};

var getAttributesFromPropsList = function getAttributesFromPropsList(tagType, propsList) {
    return propsList.filter(function (props) {
        return typeof props[tagType] !== "undefined";
    }).map(function (props) {
        return props[tagType];
    }).reduce(function (tagAttrs, current) {
        return _extends({}, tagAttrs, current);
    }, {});
};

var getBaseTagFromPropsList = function getBaseTagFromPropsList(primaryAttributes, propsList) {
    return propsList.filter(function (props) {
        return typeof props[TAG_NAMES.BASE] !== "undefined";
    }).map(function (props) {
        return props[TAG_NAMES.BASE];
    }).reverse().reduce(function (innermostBaseTag, tag) {
        if (!innermostBaseTag.length) {
            var keys = Object.keys(tag);

            for (var i = 0; i < keys.length; i++) {
                var attributeKey = keys[i];
                var lowerCaseAttributeKey = attributeKey.toLowerCase();

                if (primaryAttributes.indexOf(lowerCaseAttributeKey) !== -1 && tag[lowerCaseAttributeKey]) {
                    return innermostBaseTag.concat(tag);
                }
            }
        }

        return innermostBaseTag;
    }, []);
};

var getTagsFromPropsList = function getTagsFromPropsList(tagName, primaryAttributes, propsList) {
    // Calculate list of tags, giving priority innermost component (end of the propslist)
    var approvedSeenTags = {};

    return propsList.filter(function (props) {
        if (Array.isArray(props[tagName])) {
            return true;
        }
        if (typeof props[tagName] !== "undefined") {
            warn("Helmet: " + tagName + " should be of type \"Array\". Instead found type \"" + _typeof(props[tagName]) + "\"");
        }
        return false;
    }).map(function (props) {
        return props[tagName];
    }).reverse().reduce(function (approvedTags, instanceTags) {
        var instanceSeenTags = {};

        instanceTags.filter(function (tag) {
            var primaryAttributeKey = void 0;
            var keys = Object.keys(tag);
            for (var i = 0; i < keys.length; i++) {
                var attributeKey = keys[i];
                var lowerCaseAttributeKey = attributeKey.toLowerCase();

                // Special rule with link tags, since rel and href are both primary tags, rel takes priority
                if (primaryAttributes.indexOf(lowerCaseAttributeKey) !== -1 && !(primaryAttributeKey === TAG_PROPERTIES.REL && tag[primaryAttributeKey].toLowerCase() === "canonical") && !(lowerCaseAttributeKey === TAG_PROPERTIES.REL && tag[lowerCaseAttributeKey].toLowerCase() === "stylesheet")) {
                    primaryAttributeKey = lowerCaseAttributeKey;
                }
                // Special case for innerHTML which doesn't work lowercased
                if (primaryAttributes.indexOf(attributeKey) !== -1 && (attributeKey === TAG_PROPERTIES.INNER_HTML || attributeKey === TAG_PROPERTIES.CSS_TEXT || attributeKey === TAG_PROPERTIES.ITEM_PROP)) {
                    primaryAttributeKey = attributeKey;
                }
            }

            if (!primaryAttributeKey || !tag[primaryAttributeKey]) {
                return false;
            }

            var value = tag[primaryAttributeKey].toLowerCase();

            if (!approvedSeenTags[primaryAttributeKey]) {
                approvedSeenTags[primaryAttributeKey] = {};
            }

            if (!instanceSeenTags[primaryAttributeKey]) {
                instanceSeenTags[primaryAttributeKey] = {};
            }

            if (!approvedSeenTags[primaryAttributeKey][value]) {
                instanceSeenTags[primaryAttributeKey][value] = true;
                return true;
            }

            return false;
        }).reverse().forEach(function (tag) {
            return approvedTags.push(tag);
        });

        // Update seen tags with tags from this instance
        var keys = Object.keys(instanceSeenTags);
        for (var i = 0; i < keys.length; i++) {
            var attributeKey = keys[i];
            var tagUnion = objectAssign({}, approvedSeenTags[attributeKey], instanceSeenTags[attributeKey]);

            approvedSeenTags[attributeKey] = tagUnion;
        }

        return approvedTags;
    }, []).reverse();
};

var getInnermostProperty = function getInnermostProperty(propsList, property) {
    for (var i = propsList.length - 1; i >= 0; i--) {
        var props = propsList[i];

        if (props.hasOwnProperty(property)) {
            return props[property];
        }
    }

    return null;
};

var reducePropsToState = function reducePropsToState(propsList) {
    return {
        baseTag: getBaseTagFromPropsList([TAG_PROPERTIES.HREF], propsList),
        bodyAttributes: getAttributesFromPropsList(ATTRIBUTE_NAMES.BODY, propsList),
        defer: getInnermostProperty(propsList, HELMET_PROPS.DEFER),
        encode: getInnermostProperty(propsList, HELMET_PROPS.ENCODE_SPECIAL_CHARACTERS),
        htmlAttributes: getAttributesFromPropsList(ATTRIBUTE_NAMES.HTML, propsList),
        linkTags: getTagsFromPropsList(TAG_NAMES.LINK, [TAG_PROPERTIES.REL, TAG_PROPERTIES.HREF], propsList),
        metaTags: getTagsFromPropsList(TAG_NAMES.META, [TAG_PROPERTIES.NAME, TAG_PROPERTIES.CHARSET, TAG_PROPERTIES.HTTPEQUIV, TAG_PROPERTIES.PROPERTY, TAG_PROPERTIES.ITEM_PROP], propsList),
        noscriptTags: getTagsFromPropsList(TAG_NAMES.NOSCRIPT, [TAG_PROPERTIES.INNER_HTML], propsList),
        onChangeClientState: getOnChangeClientState(propsList),
        scriptTags: getTagsFromPropsList(TAG_NAMES.SCRIPT, [TAG_PROPERTIES.SRC, TAG_PROPERTIES.INNER_HTML], propsList),
        styleTags: getTagsFromPropsList(TAG_NAMES.STYLE, [TAG_PROPERTIES.CSS_TEXT], propsList),
        title: getTitleFromPropsList(propsList),
        titleAttributes: getAttributesFromPropsList(ATTRIBUTE_NAMES.TITLE, propsList)
    };
};

var rafPolyfill = function () {
    var clock = Date.now();

    return function (callback) {
        var currentTime = Date.now();

        if (currentTime - clock > 16) {
            clock = currentTime;
            callback(currentTime);
        } else {
            setTimeout(function () {
                rafPolyfill(callback);
            }, 0);
        }
    };
}();

var cafPolyfill = function cafPolyfill(id) {
    return clearTimeout(id);
};

var requestAnimationFrame = typeof window !== "undefined" ? window.requestAnimationFrame || window.webkitRequestAnimationFrame || window.mozRequestAnimationFrame || rafPolyfill : global.requestAnimationFrame || rafPolyfill;

var cancelAnimationFrame = typeof window !== "undefined" ? window.cancelAnimationFrame || window.webkitCancelAnimationFrame || window.mozCancelAnimationFrame || cafPolyfill : global.cancelAnimationFrame || cafPolyfill;

var warn = function warn(msg) {
    return console && typeof console.warn === "function" && console.warn(msg);
};

var _helmetCallback = null;

var handleClientStateChange = function handleClientStateChange(newState) {
    if (_helmetCallback) {
        cancelAnimationFrame(_helmetCallback);
    }

    if (newState.defer) {
        _helmetCallback = requestAnimationFrame(function () {
            commitTagChanges(newState, function () {
                _helmetCallback = null;
            });
        });
    } else {
        commitTagChanges(newState);
        _helmetCallback = null;
    }
};

var commitTagChanges = function commitTagChanges(newState, cb) {
    var baseTag = newState.baseTag,
        bodyAttributes = newState.bodyAttributes,
        htmlAttributes = newState.htmlAttributes,
        linkTags = newState.linkTags,
        metaTags = newState.metaTags,
        noscriptTags = newState.noscriptTags,
        onChangeClientState = newState.onChangeClientState,
        scriptTags = newState.scriptTags,
        styleTags = newState.styleTags,
        title = newState.title,
        titleAttributes = newState.titleAttributes;

    updateAttributes(TAG_NAMES.BODY, bodyAttributes);
    updateAttributes(TAG_NAMES.HTML, htmlAttributes);

    updateTitle(title, titleAttributes);

    var tagUpdates = {
        baseTag: updateTags(TAG_NAMES.BASE, baseTag),
        linkTags: updateTags(TAG_NAMES.LINK, linkTags),
        metaTags: updateTags(TAG_NAMES.META, metaTags),
        noscriptTags: updateTags(TAG_NAMES.NOSCRIPT, noscriptTags),
        scriptTags: updateTags(TAG_NAMES.SCRIPT, scriptTags),
        styleTags: updateTags(TAG_NAMES.STYLE, styleTags)
    };

    var addedTags = {};
    var removedTags = {};

    Object.keys(tagUpdates).forEach(function (tagType) {
        var _tagUpdates$tagType = tagUpdates[tagType],
            newTags = _tagUpdates$tagType.newTags,
            oldTags = _tagUpdates$tagType.oldTags;


        if (newTags.length) {
            addedTags[tagType] = newTags;
        }
        if (oldTags.length) {
            removedTags[tagType] = tagUpdates[tagType].oldTags;
        }
    });

    cb && cb();

    onChangeClientState(newState, addedTags, removedTags);
};

var flattenArray = function flattenArray(possibleArray) {
    return Array.isArray(possibleArray) ? possibleArray.join("") : possibleArray;
};

var updateTitle = function updateTitle(title, attributes) {
    if (typeof title !== "undefined" && document.title !== title) {
        document.title = flattenArray(title);
    }

    updateAttributes(TAG_NAMES.TITLE, attributes);
};

var updateAttributes = function updateAttributes(tagName, attributes) {
    var elementTag = document.getElementsByTagName(tagName)[0];

    if (!elementTag) {
        return;
    }

    var helmetAttributeString = elementTag.getAttribute(HELMET_ATTRIBUTE);
    var helmetAttributes = helmetAttributeString ? helmetAttributeString.split(",") : [];
    var attributesToRemove = [].concat(helmetAttributes);
    var attributeKeys = Object.keys(attributes);

    for (var i = 0; i < attributeKeys.length; i++) {
        var attribute = attributeKeys[i];
        var value = attributes[attribute] || "";

        if (elementTag.getAttribute(attribute) !== value) {
            elementTag.setAttribute(attribute, value);
        }

        if (helmetAttributes.indexOf(attribute) === -1) {
            helmetAttributes.push(attribute);
        }

        var indexToSave = attributesToRemove.indexOf(attribute);
        if (indexToSave !== -1) {
            attributesToRemove.splice(indexToSave, 1);
        }
    }

    for (var _i = attributesToRemove.length - 1; _i >= 0; _i--) {
        elementTag.removeAttribute(attributesToRemove[_i]);
    }

    if (helmetAttributes.length === attributesToRemove.length) {
        elementTag.removeAttribute(HELMET_ATTRIBUTE);
    } else if (elementTag.getAttribute(HELMET_ATTRIBUTE) !== attributeKeys.join(",")) {
        elementTag.setAttribute(HELMET_ATTRIBUTE, attributeKeys.join(","));
    }
};

var updateTags = function updateTags(type, tags) {
    var headElement = document.head || document.querySelector(TAG_NAMES.HEAD);
    var tagNodes = headElement.querySelectorAll(type + "[" + HELMET_ATTRIBUTE + "]");
    var oldTags = Array.prototype.slice.call(tagNodes);
    var newTags = [];
    var indexToDelete = void 0;

    if (tags && tags.length) {
        tags.forEach(function (tag) {
            var newElement = document.createElement(type);

            for (var attribute in tag) {
                if (tag.hasOwnProperty(attribute)) {
                    if (attribute === TAG_PROPERTIES.INNER_HTML) {
                        newElement.innerHTML = tag.innerHTML;
                    } else if (attribute === TAG_PROPERTIES.CSS_TEXT) {
                        if (newElement.styleSheet) {
                            newElement.styleSheet.cssText = tag.cssText;
                        } else {
                            newElement.appendChild(document.createTextNode(tag.cssText));
                        }
                    } else {
                        var value = typeof tag[attribute] === "undefined" ? "" : tag[attribute];
                        newElement.setAttribute(attribute, value);
                    }
                }
            }

            newElement.setAttribute(HELMET_ATTRIBUTE, "true");

            // Remove a duplicate tag from domTagstoRemove, so it isn't cleared.
            if (oldTags.some(function (existingTag, index) {
                indexToDelete = index;
                return newElement.isEqualNode(existingTag);
            })) {
                oldTags.splice(indexToDelete, 1);
            } else {
                newTags.push(newElement);
            }
        });
    }

    oldTags.forEach(function (tag) {
        return tag.parentNode.removeChild(tag);
    });
    newTags.forEach(function (tag) {
        return headElement.appendChild(tag);
    });

    return {
        oldTags: oldTags,
        newTags: newTags
    };
};

var generateElementAttributesAsString = function generateElementAttributesAsString(attributes) {
    return Object.keys(attributes).reduce(function (str, key) {
        var attr = typeof attributes[key] !== "undefined" ? key + "=\"" + attributes[key] + "\"" : "" + key;
        return str ? str + " " + attr : attr;
    }, "");
};

var generateTitleAsString = function generateTitleAsString(type, title, attributes, encode) {
    var attributeString = generateElementAttributesAsString(attributes);
    var flattenedTitle = flattenArray(title);
    return attributeString ? "<" + type + " " + HELMET_ATTRIBUTE + "=\"true\" " + attributeString + ">" + encodeSpecialCharacters(flattenedTitle, encode) + "</" + type + ">" : "<" + type + " " + HELMET_ATTRIBUTE + "=\"true\">" + encodeSpecialCharacters(flattenedTitle, encode) + "</" + type + ">";
};

var generateTagsAsString = function generateTagsAsString(type, tags, encode) {
    return tags.reduce(function (str, tag) {
        var attributeHtml = Object.keys(tag).filter(function (attribute) {
            return !(attribute === TAG_PROPERTIES.INNER_HTML || attribute === TAG_PROPERTIES.CSS_TEXT);
        }).reduce(function (string, attribute) {
            var attr = typeof tag[attribute] === "undefined" ? attribute : attribute + "=\"" + encodeSpecialCharacters(tag[attribute], encode) + "\"";
            return string ? string + " " + attr : attr;
        }, "");

        var tagContent = tag.innerHTML || tag.cssText || "";

        var isSelfClosing = SELF_CLOSING_TAGS.indexOf(type) === -1;

        return str + "<" + type + " " + HELMET_ATTRIBUTE + "=\"true\" " + attributeHtml + (isSelfClosing ? "/>" : ">" + tagContent + "</" + type + ">");
    }, "");
};

var convertElementAttributestoReactProps = function convertElementAttributestoReactProps(attributes) {
    var initProps = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : {};

    return Object.keys(attributes).reduce(function (obj, key) {
        obj[REACT_TAG_MAP[key] || key] = attributes[key];
        return obj;
    }, initProps);
};

var convertReactPropstoHtmlAttributes = function convertReactPropstoHtmlAttributes(props) {
    var initAttributes = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : {};

    return Object.keys(props).reduce(function (obj, key) {
        obj[HTML_TAG_MAP[key] || key] = props[key];
        return obj;
    }, initAttributes);
};

var generateTitleAsReactComponent = function generateTitleAsReactComponent(type, title, attributes) {
    var _initProps;

    // assigning into an array to define toString function on it
    var initProps = (_initProps = {
        key: title
    }, _initProps[HELMET_ATTRIBUTE] = true, _initProps);
    var props = convertElementAttributestoReactProps(attributes, initProps);

    return [React.createElement(TAG_NAMES.TITLE, props, title)];
};

var generateTagsAsReactComponent = function generateTagsAsReactComponent(type, tags) {
    return tags.map(function (tag, i) {
        var _mappedTag;

        var mappedTag = (_mappedTag = {
            key: i
        }, _mappedTag[HELMET_ATTRIBUTE] = true, _mappedTag);

        Object.keys(tag).forEach(function (attribute) {
            var mappedAttribute = REACT_TAG_MAP[attribute] || attribute;

            if (mappedAttribute === TAG_PROPERTIES.INNER_HTML || mappedAttribute === TAG_PROPERTIES.CSS_TEXT) {
                var content = tag.innerHTML || tag.cssText;
                mappedTag.dangerouslySetInnerHTML = { __html: content };
            } else {
                mappedTag[mappedAttribute] = tag[attribute];
            }
        });

        return React.createElement(type, mappedTag);
    });
};

var getMethodsForTag = function getMethodsForTag(type, tags, encode) {
    switch (type) {
        case TAG_NAMES.TITLE:
            return {
                toComponent: function toComponent() {
                    return generateTitleAsReactComponent(type, tags.title, tags.titleAttributes, encode);
                },
                toString: function toString() {
                    return generateTitleAsString(type, tags.title, tags.titleAttributes, encode);
                }
            };
        case ATTRIBUTE_NAMES.BODY:
        case ATTRIBUTE_NAMES.HTML:
            return {
                toComponent: function toComponent() {
                    return convertElementAttributestoReactProps(tags);
                },
                toString: function toString() {
                    return generateElementAttributesAsString(tags);
                }
            };
        default:
            return {
                toComponent: function toComponent() {
                    return generateTagsAsReactComponent(type, tags);
                },
                toString: function toString() {
                    return generateTagsAsString(type, tags, encode);
                }
            };
    }
};

var mapStateOnServer = function mapStateOnServer(_ref) {
    var baseTag = _ref.baseTag,
        bodyAttributes = _ref.bodyAttributes,
        encode = _ref.encode,
        htmlAttributes = _ref.htmlAttributes,
        linkTags = _ref.linkTags,
        metaTags = _ref.metaTags,
        noscriptTags = _ref.noscriptTags,
        scriptTags = _ref.scriptTags,
        styleTags = _ref.styleTags,
        _ref$title = _ref.title,
        title = _ref$title === undefined ? "" : _ref$title,
        titleAttributes = _ref.titleAttributes;
    return {
        base: getMethodsForTag(TAG_NAMES.BASE, baseTag, encode),
        bodyAttributes: getMethodsForTag(ATTRIBUTE_NAMES.BODY, bodyAttributes, encode),
        htmlAttributes: getMethodsForTag(ATTRIBUTE_NAMES.HTML, htmlAttributes, encode),
        link: getMethodsForTag(TAG_NAMES.LINK, linkTags, encode),
        meta: getMethodsForTag(TAG_NAMES.META, metaTags, encode),
        noscript: getMethodsForTag(TAG_NAMES.NOSCRIPT, noscriptTags, encode),
        script: getMethodsForTag(TAG_NAMES.SCRIPT, scriptTags, encode),
        style: getMethodsForTag(TAG_NAMES.STYLE, styleTags, encode),
        title: getMethodsForTag(TAG_NAMES.TITLE, { title: title, titleAttributes: titleAttributes }, encode)
    };
};

var Helmet = function Helmet(Component) {
    var _class, _temp;

    return _temp = _class = function (_React$Component) {
        inherits(HelmetWrapper, _React$Component);

        function HelmetWrapper() {
            classCallCheck(this, HelmetWrapper);
            return possibleConstructorReturn(this, _React$Component.apply(this, arguments));
        }

        HelmetWrapper.prototype.shouldComponentUpdate = function shouldComponentUpdate(nextProps) {
            return !isEqual(this.props, nextProps);
        };

        HelmetWrapper.prototype.mapNestedChildrenToProps = function mapNestedChildrenToProps(child, nestedChildren) {
            if (!nestedChildren) {
                return null;
            }

            switch (child.type) {
                case TAG_NAMES.SCRIPT:
                case TAG_NAMES.NOSCRIPT:
                    return {
                        innerHTML: nestedChildren
                    };

                case TAG_NAMES.STYLE:
                    return {
                        cssText: nestedChildren
                    };
            }

            throw new Error("<" + child.type + " /> elements are self-closing and can not contain children. Refer to our API for more information.");
        };

        HelmetWrapper.prototype.flattenArrayTypeChildren = function flattenArrayTypeChildren(_ref) {
            var _babelHelpers$extends;

            var child = _ref.child,
                arrayTypeChildren = _ref.arrayTypeChildren,
                newChildProps = _ref.newChildProps,
                nestedChildren = _ref.nestedChildren;

            return _extends({}, arrayTypeChildren, (_babelHelpers$extends = {}, _babelHelpers$extends[child.type] = [].concat(arrayTypeChildren[child.type] || [], [_extends({}, newChildProps, this.mapNestedChildrenToProps(child, nestedChildren))]), _babelHelpers$extends));
        };

        HelmetWrapper.prototype.mapObjectTypeChildren = function mapObjectTypeChildren(_ref2) {
            var _babelHelpers$extends2, _babelHelpers$extends3;

            var child = _ref2.child,
                newProps = _ref2.newProps,
                newChildProps = _ref2.newChildProps,
                nestedChildren = _ref2.nestedChildren;

            switch (child.type) {
                case TAG_NAMES.TITLE:
                    return _extends({}, newProps, (_babelHelpers$extends2 = {}, _babelHelpers$extends2[child.type] = nestedChildren, _babelHelpers$extends2.titleAttributes = _extends({}, newChildProps), _babelHelpers$extends2));

                case TAG_NAMES.BODY:
                    return _extends({}, newProps, {
                        bodyAttributes: _extends({}, newChildProps)
                    });

                case TAG_NAMES.HTML:
                    return _extends({}, newProps, {
                        htmlAttributes: _extends({}, newChildProps)
                    });
            }

            return _extends({}, newProps, (_babelHelpers$extends3 = {}, _babelHelpers$extends3[child.type] = _extends({}, newChildProps), _babelHelpers$extends3));
        };

        HelmetWrapper.prototype.mapArrayTypeChildrenToProps = function mapArrayTypeChildrenToProps(arrayTypeChildren, newProps) {
            var newFlattenedProps = _extends({}, newProps);

            Object.keys(arrayTypeChildren).forEach(function (arrayChildName) {
                var _babelHelpers$extends4;

                newFlattenedProps = _extends({}, newFlattenedProps, (_babelHelpers$extends4 = {}, _babelHelpers$extends4[arrayChildName] = arrayTypeChildren[arrayChildName], _babelHelpers$extends4));
            });

            return newFlattenedProps;
        };

        HelmetWrapper.prototype.warnOnInvalidChildren = function warnOnInvalidChildren(child, nestedChildren) {
            if (process.env.NODE_ENV !== "production") {
                if (!VALID_TAG_NAMES.some(function (name) {
                    return child.type === name;
                })) {
                    if (typeof child.type === "function") {
                        return warn("You may be attempting to nest <Helmet> components within each other, which is not allowed. Refer to our API for more information.");
                    }

                    return warn("Only elements types " + VALID_TAG_NAMES.join(", ") + " are allowed. Helmet does not support rendering <" + child.type + "> elements. Refer to our API for more information.");
                }

                if (nestedChildren && typeof nestedChildren !== "string" && (!Array.isArray(nestedChildren) || nestedChildren.some(function (nestedChild) {
                    return typeof nestedChild !== "string";
                }))) {
                    throw new Error("Helmet expects a string as a child of <" + child.type + ">. Did you forget to wrap your children in braces? ( <" + child.type + ">{``}</" + child.type + "> ) Refer to our API for more information.");
                }
            }

            return true;
        };

        HelmetWrapper.prototype.mapChildrenToProps = function mapChildrenToProps(children, newProps) {
            var _this2 = this;

            var arrayTypeChildren = {};

            React.Children.forEach(children, function (child) {
                if (!child || !child.props) {
                    return;
                }

                var _child$props = child.props,
                    nestedChildren = _child$props.children,
                    childProps = objectWithoutProperties(_child$props, ["children"]);

                var newChildProps = convertReactPropstoHtmlAttributes(childProps);

                _this2.warnOnInvalidChildren(child, nestedChildren);

                switch (child.type) {
                    case TAG_NAMES.LINK:
                    case TAG_NAMES.META:
                    case TAG_NAMES.NOSCRIPT:
                    case TAG_NAMES.SCRIPT:
                    case TAG_NAMES.STYLE:
                        arrayTypeChildren = _this2.flattenArrayTypeChildren({
                            child: child,
                            arrayTypeChildren: arrayTypeChildren,
                            newChildProps: newChildProps,
                            nestedChildren: nestedChildren
                        });
                        break;

                    default:
                        newProps = _this2.mapObjectTypeChildren({
                            child: child,
                            newProps: newProps,
                            newChildProps: newChildProps,
                            nestedChildren: nestedChildren
                        });
                        break;
                }
            });

            newProps = this.mapArrayTypeChildrenToProps(arrayTypeChildren, newProps);
            return newProps;
        };

        HelmetWrapper.prototype.render = function render() {
            var _props = this.props,
                children = _props.children,
                props = objectWithoutProperties(_props, ["children"]);

            var newProps = _extends({}, props);

            if (children) {
                newProps = this.mapChildrenToProps(children, newProps);
            }

            return React.createElement(Component, newProps);
        };

        createClass(HelmetWrapper, null, [{
            key: "canUseDOM",


            // Component.peek comes from react-side-effect:
            // For testing, you may use a static peek() method available on the returned component.
            // It lets you get the current state without resetting the mounted instance stack.
            // Don’t use it for anything other than testing.

            /**
            * @param {Object} base: {"target": "_blank", "href": "http://mysite.com/"}
            * @param {Object} bodyAttributes: {"className": "root"}
            * @param {String} defaultTitle: "Default Title"
            * @param {Boolean} defer: true
            * @param {Boolean} encodeSpecialCharacters: true
            * @param {Object} htmlAttributes: {"lang": "en", "amp": undefined}
            * @param {Array} link: [{"rel": "canonical", "href": "http://mysite.com/example"}]
            * @param {Array} meta: [{"name": "description", "content": "Test description"}]
            * @param {Array} noscript: [{"innerHTML": "<img src='http://mysite.com/js/test.js'"}]
            * @param {Function} onChangeClientState: "(newState) => console.log(newState)"
            * @param {Array} script: [{"type": "text/javascript", "src": "http://mysite.com/js/test.js"}]
            * @param {Array} style: [{"type": "text/css", "cssText": "div { display: block; color: blue; }"}]
            * @param {String} title: "Title"
            * @param {Object} titleAttributes: {"itemprop": "name"}
            * @param {String} titleTemplate: "MySite.com - %s"
            */
            set: function set$$1(canUseDOM) {
                Component.canUseDOM = canUseDOM;
            }
        }]);
        return HelmetWrapper;
    }(React.Component), _class.propTypes = {
        base: PropTypes.object,
        bodyAttributes: PropTypes.object,
        children: PropTypes.oneOfType([PropTypes.arrayOf(PropTypes.node), PropTypes.node]),
        defaultTitle: PropTypes.string,
        defer: PropTypes.bool,
        encodeSpecialCharacters: PropTypes.bool,
        htmlAttributes: PropTypes.object,
        link: PropTypes.arrayOf(PropTypes.object),
        meta: PropTypes.arrayOf(PropTypes.object),
        noscript: PropTypes.arrayOf(PropTypes.object),
        onChangeClientState: PropTypes.func,
        script: PropTypes.arrayOf(PropTypes.object),
        style: PropTypes.arrayOf(PropTypes.object),
        title: PropTypes.string,
        titleAttributes: PropTypes.object,
        titleTemplate: PropTypes.string
    }, _class.defaultProps = {
        defer: true,
        encodeSpecialCharacters: true
    }, _class.peek = Component.peek, _class.rewind = function () {
        var mappedState = Component.rewind();
        if (!mappedState) {
            // provide fallback if mappedState is undefined
            mappedState = mapStateOnServer({
                baseTag: [],
                bodyAttributes: {},
                encodeSpecialCharacters: true,
                htmlAttributes: {},
                linkTags: [],
                metaTags: [],
                noscriptTags: [],
                scriptTags: [],
                styleTags: [],
                title: "",
                titleAttributes: {}
            });
        }

        return mappedState;
    }, _temp;
};

var NullComponent = function NullComponent() {
    return null;
};

var HelmetSideEffects = withSideEffect(reducePropsToState, handleClientStateChange, mapStateOnServer)(NullComponent);

var HelmetExport = Helmet(HelmetSideEffects);
HelmetExport.renderStatic = HelmetExport.rewind;

exports.Helmet = HelmetExport;