use crate::shared::error::Result;
use crate::shared::name::Name;
use crate::shared::text;
use std::collections::HashMap;

// ------------------------------------------------------------------------------------------------
// Public Traits
// ------------------------------------------------------------------------------------------------

///
/// This corresponds to the DOM `Attr` interface.
///
pub trait Attribute: Node {
    ///
    /// On retrieval, the value of the attribute is returned as a string.
    ///
    /// # Specification
    ///
    /// Character and general entity references are replaced with their values. See also the method
    /// [`getAttribute`](trait.Element.html#tymethod.get_attribute) on the [`Element`](trait.Element.html)
    /// interface.
    ///
    /// On setting, this creates a `Text` node with the unparsed contents of the string. I.e. any
    /// characters that an XML processor would recognize as markup are instead treated as literal
    /// text. See also the method setAttribute on the Element interface.
    ///
    /// **Exceptions on setting**
    ///
    /// * `NO_MODIFICATION_ALLOWED_ERR`: Raised when the node is readonly.
    ///
    fn value(&self) -> Option<String>;
    ///
    /// Set the `value` for the node; see [`value`](#tymethod.value).
    ///
    fn set_value(&mut self, value: &str) -> Result<()>;
    ///
    /// Set the `value` for the node to `None`; see [`value`](#tymethod.value).
    ///
    fn unset_value(&mut self) -> Result<()>;
    ///
    /// If this attribute was explicitly given a value in the original document, this is `true`;
    /// otherwise, it is `false`.
    ///
    /// # Specification
    ///
    /// Note that the implementation is in charge of this attribute, not the user. If the user
    /// changes the value of the attribute (even if it ends up having the same value as the default
    /// value) then the specified flag is automatically flipped to true. To re-specify the
    /// attribute as the default value from the DTD, the user must delete the attribute. The
    /// implementation will then make a new attribute available with specified set to false and
    /// the default value (if one exists).
    ///
    /// In summary:
    ///
    /// * If the attribute has an assigned value in the document then specified is `true`, and the
    ///   value is the assigned value.
    /// * If the attribute has no assigned value in the document and has a default value in the
    ///   DTD, then specified is `false`, and the value is the default value in the DTD.
    /// * If the attribute has no assigned value in the document and has a value of `#IMPLIED` in
    ///   the DTD, then the attribute does not appear in the structure model of the document.
    /// * If the `ownerElement` attribute is `null` (i.e. because it was just created or was set to
    ///   `null` by the various removal and cloning operations) specified is `true`.
    ///
    fn specified(&self) -> bool {
        true
    }
    ///
    /// The `Element` node this attribute is attached to or `null` if this attribute is not in use.
    ///
    fn owner_element(&self) -> Option<Self::NodeRef>;
}

// ------------------------------------------------------------------------------------------------

///
/// This corresponds to the DOM `CDataSection` interface.
///
/// # Specification
///
/// CDATA sections are used to escape blocks of text containing characters that would otherwise be
/// regarded as markup. The only delimiter that is recognized in a CDATA section is the `"]]>"`
/// string that ends the CDATA section. CDATA sections cannot be nested. Their primary purpose is
/// for including material such as XML fragments, without needing to escape all the delimiters.
///
/// The `DOMString` attribute of the `Text` node holds the text that is contained by the CDATA
/// section. Note that this may contain characters that need to be escaped outside of CDATA
/// sections and that, depending on the character encoding ("charset") chosen for serialization,
/// it may be impossible to write out some characters as part of a CDATA section.
///
/// The `CDATASection` interface inherits from the [`CharacterData`](trait.CharacterData.html)
/// interface through the [`Text`](trait.Text.html) interface. Adjacent `CDATASection` nodes are not
/// merged by use of the normalize method of the [`Node`](trait.Node.html) interface.
///
/// **Note:** Because no markup is recognized within a `CDATASection`, character numeric references
/// cannot be used as an escape mechanism when serializing. Therefore, action needs to be taken
/// when serializing a `CDATASection` with a character encoding where some of the contained
/// characters cannot be represented. Failure to do so would not produce well-formed XML.
///
/// One potential solution in the serialization process is to end the CDATA section before the
/// character, output the character using a character reference or entity reference, and open a
/// new CDATA section for any further characters in the text node. Note, however, that some
/// code conversion libraries at the time of writing do not return an error or exception when a
/// character is missing from the encoding, making the task of ensuring that data is not corrupted
/// on serialization more difficult.
///
pub trait CDataSection: Text {}

// ------------------------------------------------------------------------------------------------

///
/// This corresponds to the DOM `CharacterData` interface.
///
/// # Specification
///
/// The `CharacterData` interface extends [`Node`](trait.Node.html) with a set of attributes and
/// methods for accessing character data in the DOM. For clarity this set is defined here rather
/// than on each object that uses these attributes and methods. No DOM objects correspond directly
/// to `CharacterData`, though [`Text`](trait.Text.html) and others do inherit the interface from it.
/// All offsets in this interface start from 0.
///
/// As explained in the `DOMString` interface, text strings in the DOM are represented in UTF-16,
/// i.e. as a sequence of 16-bit units. In the following, the term 16-bit units is used whenever
/// necessary to indicate that indexing on `CharacterData` is done in 16-bit units.
///
pub trait CharacterData: Node {
    ///
    /// The number of 16-bit units that are available through data and the `substringData` method
    /// below. This may have the value zero, i.e., `CharacterData` nodes may be empty.
    ///
    /// **Note:** This implementation drops the `_data` suffix from the methods for clarity.
    ///
    fn length(&self) -> usize {
        match self.data() {
            None => 0,
            Some(s) => s.len(),
        }
    }
    ///
    /// The character data of the node that implements this interface.
    ///
    /// # Specification
    ///
    /// The DOM implementation may not put arbitrary limits on the amount of data that may be
    /// stored in a `CharacterData` node. However, implementation limits may mean that the entirety
    /// of a node's data may not fit into a single `DOMString`. In such cases, the user may call
    /// `substringData` to retrieve the data in appropriately sized pieces.
    ///
    /// **Exceptions on setting**
    ///
    /// * `NO_MODIFICATION_ALLOWED_ERR`: Raised when the node is readonly.
    ///
    /// **Exceptions on retrieval**
    ///
    /// * `DOMSTRING_SIZE_ERR`: Raised when it would return more characters than fit in a
    ///   `DOMString` variable on the implementation platform.
    ///
    fn data(&self) -> Option<String> {
        let node_type = self.node_type();
        match (
            Node::node_value(self),
            node_type == NodeType::Text || node_type == NodeType::Comment,
        ) {
            (None, _) => None,
            (v @ Some(_), false) => v,
            (Some(value), true) => Some(text::escape(&value)),
        }
    }
    ///
    /// Set the `data` for the node; see [data()](#tymethod.data).
    ///
    fn set_data(&mut self, data: &str) -> Result<()> {
        Node::set_node_value(self, data)
    }
    ///
    /// Set the `data` for the node to `None`; see [data()](#tymethod.data).
    ///
    fn unset_data(&mut self) -> Result<()> {
        Node::unset_node_value(self)
    }
    ///
    /// Extracts a range of data from the node.
    ///
    /// # Specification
    ///
    /// **Parameters**
    ///
    /// * `offset` of type `unsigned long`: Start offset of substring to extract.
    /// * `count` of type `unsigned long`: The number of 16-bit units to extract.
    ///
    /// **Return Value**
    ///
    /// * `DOMString`: The specified substring. If the sum of `offset` and `count` exceeds the
    ///   `length`, then all 16-bit units to the end of the data are returned.
    ///
    /// **Exceptions**
    ///
    /// * `INDEX_SIZE_ERR`: Raised if the specified `offset` is negative or greater than the
    ///   number of 16-bit units in data, or if the specified `count` is negative.
    /// * `DOMSTRING_SIZE_ERR`: Raised if the specified range of text does not fit into a `DOMString`.
    ///
    fn substring_data(&self, offset: usize, count: usize) -> Result<String>;
    ///
    /// Append the string to the end of the character data of the node.
    ///
    /// # Specification
    ///
    /// Upon success, data provides access to the concatenation of data and the DOMString specified.
    ///
    /// **Parameters**
    ///
    /// * `arg` of type `DOMString`: The DOMString to append.
    ///
    /// **Exceptions**
    /// * `NO_MODIFICATION_ALLOWED_ERR`: Raised if this node is readonly.
    ///
    fn append_data(&mut self, data: &str) -> Result<()>;
    ///
    /// Insert a string at the specified 16-bit unit offset.
    ///
    /// # Specification
    ///
    /// **Parameters**
    ///
    /// * `offset` of type `unsigned long`: The character offset at which to insert.
    /// * `arg` of type `DOMString`: The DOMString to insert.
    ///
    /// **Exceptions**
    ///
    /// * `INDEX_SIZE_ERR`: Raised if the specified `offset` is negative or greater than the number
    ///   of 16-bit units in data.
    /// * `NO_MODIFICATION_ALLOWED_ERR`: Raised if this node is readonly.
    ///
    fn insert_data(&mut self, offset: usize, data: &str) -> Result<()>;
    ///
    /// Remove a range of 16-bit units from the node. Upon success, data and length reflect the change.
    ///
    /// # Specification
    ///
    /// **Parameters**
    ///
    /// * `offset` of type `unsigned long`: The offset from which to start removing.
    /// * `count` of type `unsigned long`: The number of 16-bit units to delete. If the sum of
    ///   `offset` and `count` exceeds `length` then all 16-bit units from offset to the end of
    ///   the data are deleted.
    ///
    /// **Exceptions**
    ///
    /// * `INDEX_SIZE_ERR`: Raised if the specified `offset` is negative or greater than the number
    ///   of 16-bit units in data, or if the specified `count` is negative.
    /// * `NO_MODIFICATION_ALLOWED_ERR`: Raised if this node is readonly.
    ///
    fn delete_data(&mut self, offset: usize, count: usize) -> Result<()>;
    ///
    /// Replace the characters starting at the specified 16-bit unit offset with the specified string.
    ///
    /// # Specification
    ///
    /// **Parameters**
    ///
    /// * `offset` of type `unsigned long`: The offset from which to start replacing.
    /// * `count` of type `unsigned long`: The number of 16-bit units to replace. If the sum of
    ///   `offset` and `count` exceeds `length`, then all 16-bit units to the end of the data are
    ///   replaced; (i.e., the effect is the same as a remove method call with the same range,
    ///   followed by an append method invocation).
    /// * `arg` of type `DOMString`: The `DOMString` with which the range must be replaced.
    /// Exceptions
    ///
    /// INDEX_SIZE_ERR: Raised if the specified `offset` is negative or greater than the number
    ///   of 16-bit units in data, or if the specified `count` is negative.
    /// NO_MODIFICATION_ALLOWED_ERR: Raised if this node is readonly.
    ///
    fn replace_data(&mut self, offset: usize, count: usize, data: &str) -> Result<()>;
}

// ------------------------------------------------------------------------------------------------

///
/// This corresponds to the DOM `Comment` interface.
///
/// # Specification
///
/// This interface inherits from [`CharacterData`](trait.CharacterData.html) and represents the
/// content of a comment, i.e., all the characters between the starting `'<!--'` and ending `'-->'`.
/// Note that this is the definition of a comment in XML, and, in practice, HTML, although some
/// HTML tools may implement the full SGML comment structure.
///
pub trait Comment: CharacterData {}

// ------------------------------------------------------------------------------------------------

///
/// This corresponds to the DOM `Document` interface.
///
pub trait Document: Node {
    ///
    /// The Document Type Declaration (see [`DocumentType`](trait.DocumentType.html)) associated with
    /// this document.
    ///
    /// # Specification
    ///
    /// For HTML documents as well as XML documents without a document type
    /// declaration this returns `null`. The DOM Level 2 does not support editing the Document Type
    /// Declaration. `docType` cannot be altered in any way, including through the use of methods
    /// inherited from the [`Node`](trait.Node.html) interface, such as `insertNode` or `removeNode`.
    ///
    fn doc_type(&self) -> Option<Self::NodeRef>;
    ///
    /// This is a convenience attribute that allows direct access to the child node that is the
    /// root element of the document.
    ///
    /// # Specification
    ///
    /// For HTML documents, this is the element with the tagName `"HTML"`.
    ///
    fn document_element(&self) -> Option<Self::NodeRef>;
    ///
    /// The DOMImplementation object that handles this document.
    ///
    /// Note: this function will panic if for some reason an implementation is not associated
    /// with the document instance.
    ///
    /// # Specification
    ///
    /// A DOM application may use objects from multiple implementations.
    ///
    fn implementation(&self) -> &dyn DOMImplementation<NodeRef = Self::NodeRef>;
    ///
    /// Creates an [`Attribute`](trait.Attribute.html) of the given name. Note that the `Attr`
    /// instance can then be set on an [`Element`](trait.Element.html) using the `setAttributeNode`
    /// method.
    ///
    /// # Specification
    ///
    /// To create an attribute with a qualified name and namespace URI, use the `createAttributeNS`
    /// method.
    ///
    /// **Parameters**
    ///
    /// * `name` of type `DOMString`: The name of the attribute.
    ///
    /// **Return Value**
    ///
    /// * `Attr`: A new `Attr` object with the `nodeName` attribute set to name, and `localName`,
    ///   `prefix`, and `namespaceURI` set to `null`. The value of the attribute is the empty string.
    ///
    /// **Exceptions**
    ///
    /// * `INVALID_CHARACTER_ERR`: Raised if the specified name contains an illegal character.
    ///
    fn create_attribute(&self, name: &str) -> Result<Self::NodeRef>;
    ///
    /// Implementation defined extension: this is the same as `create_attribute` except that it
    /// also sets the attribute value.
    ///
    fn create_attribute_with(&self, name: &str, value: &str) -> Result<Self::NodeRef>;
    ///
    /// Creates an attribute of the given qualified name and namespace URI.
    ///
    /// # Specification
    ///
    /// HTML-only DOM implementations do not need to implement this method.
    ///
    /// **Parameters**
    ///
    /// * `namespaceURI` of type `DOMString`: The namespace URI of the attribute to create.
    /// * `qualifiedName` of type `DOMString`: The qualified name of the attribute to instantiate.
    ///
    /// **Return Value**
    ///
    /// * [`Attr`](trait.Attribute.html): A new `Attr` object with the following attributes:
    ///
    /// | Attribute           | Value               |
    /// |---------------------|---------------------|
    /// | `Node.nodeName`     | `qualifiedName`     |
    /// | `Node.namespaceURI` | `namespaceURI`      |
    /// | `Node.prefix`       | prefix, extracted from `qualifiedName`, or `null` if there is no prefix |
    /// | `Node.localName`    | local name, extracted from `qualifiedName` |
    /// | `Attr.name`         | `qualifiedName`     |
    /// | `Node.nodeValue`    | the empty string    |
    ///
    /// **Exceptions**
    ///
    /// * `INVALID_CHARACTER_ERR`: Raised if the specified qualified name contains an illegal
    ///   character.
    /// * `NAMESPACE_ERR`: Raised if the `qualifiedName` is malformed, if the `qualifiedName` has
    ///   a `prefix` and the `namespaceURI` is `null`, if the `qualifiedName` has a `prefix` that
    ///   is "xml" and the `namespaceURI` is different from "http://www.w3.org/XML/1998/namespace",
    ///   or if the `qualifiedName` is "xmlns" and the namespaceURI is different from
    ///   "http://www.w3.org/2000/xmlns/".
    ///
    fn create_attribute_ns(
        &self,
        namespace_uri: &str,
        qualified_name: &str,
    ) -> Result<Self::NodeRef>;
    ///
    /// Creates a [`CDataSection`](trait.CDataSection.html) node whose value is the specified string.
    ///
    /// # Specification
    ///
    /// **Parameters**
    ///
    /// * `data` of type `DOMString`: The data for the `CDATASection` contents.
    ///
    /// **Return Value**
    ///
    /// * `CDATASection`: The new `CDATASection` object.
    ///
    /// **Exceptions**
    ///
    /// * `NOT_SUPPORTED_ERR`: Raised if this document is an HTML document.
    ///
    fn create_cdata_section(&self, data: &str) -> Result<Self::NodeRef>;
    ///
    /// Creates an empty DocumentFragment object.
    ///
    /// # Specification
    ///
    /// **Return Value**
    ///
    /// `DocumentFragment`: A new `DocumentFragment`.
    ///
    fn create_document_fragment(&self) -> Result<Self::NodeRef>;
    ///
    /// Creates an `EntityReference` object.
    ///
    /// # Specification
    ///
    /// In addition, if the referenced entity is known, the child list of the `EntityReference`
    /// node is made the same as that of the corresponding `Entity` node.
    ///
    /// **Note:** If any descendant of the `Entity` node has an unbound namespace prefix, the
    /// corresponding descendant of the created `EntityReference` node is also unbound; (its
    /// `namespaceURI` is `null`). The DOM Level 2 does not support any mechanism to resolve
    /// namespace prefixes.
    ///
    /// **Parameters**
    ///
    /// * `name` of type `DOMString`: The name of the entity to reference.
    ///
    /// **Return Value**
    ///
    /// * `EntityReference`: The new `EntityReference` object.
    ///
    /// **Exceptions**
    ///
    ///
    /// * `INVALID_CHARACTER_ERR`: Raised if the specified name contains an illegal character.
    /// * `NOT_SUPPORTED_ERR`: Raised if this document is an HTML document.
    ///
    fn create_entity_reference(&self, name: &str) -> Result<Self::NodeRef>;
    ///
    /// Creates a [`Comment`](trait.Comment.html) node given the specified string.
    ///
    /// # Specification
    ///
    /// **Parameters**
    ///
    /// * `data` of type `DOMString`: The data for the node.
    ///
    /// **Return Value**
    ///
    /// * `Comment`: The new `Comment` object.
    ///
    fn create_comment(&self, data: &str) -> Self::NodeRef;
    ///
    /// Creates an element of the type specified.
    ///
    /// # Specification
    ///
    /// Note that the instance returned implements the [`Element`](trait.Element.html) interface, so
    /// attributes can be specified directly on the returned object.
    ///
    /// In addition, if there are known attributes with default values, [`Attr`](trait.Attribute.html)
    /// nodes representing them are automatically created and attached to the element.
    ///
    /// To create an element with a qualified name and namespace URI, use the `createElementNS` method.
    ///
    /// **Parameters**
    ///
    /// * `tagName` of type `DOMString:  The name of the element type to instantiate. For XML, this
    ///   is case-sensitive. For HTML, the `tagName` parameter may be provided in any case, but
    ///   it must be mapped to the canonical uppercase form by the DOM implementation.
    ///
    /// **Return Value**
    ///
    /// * `Element`: A new `Element` object with the `nodeName` attribute set to `tagName`, and
    ///   `localName`, `prefix`, and `namespaceURI` set to `null`.
    ///
    /// **Exceptions**
    ///
    /// * `INVALID_CHARACTER_ERR`: Raised if the specified name contains an illegal character.
    ///
    fn create_element(&self, tag_name: &str) -> Result<Self::NodeRef>;
    ///
    /// Creates an element of the given qualified name and namespace URI.
    ///
    /// # Specification
    ///
    /// HTML-only DOM implementations do not need to implement this method.
    ///
    /// **Parameters**
    ///
    /// * `namespaceURI` of type `DOMString`: The namespace URI of the attribute to create.
    /// * `qualifiedName` of type `DOMString`: The qualified name of the attribute to instantiate.
    ///
    /// **Return Value**
    ///
    /// * `Element`: A new Element object with the following attributes:
    ///
    /// | Attribute           | Value               |
    /// |---------------------|---------------------|
    /// | `Node.nodeName`     | `qualifiedName`     |
    /// | `Node.namespaceURI` | `namespaceURI`      |
    /// | `Node.prefix`       | prefix, extracted from `qualifiedName`, or `null` if there is no prefix |
    /// | `Node.localName`    | local name, extracted from `qualifiedName` |
    /// | `Attr.name`         | `qualifiedName`     |
    /// | `Node.nodeValue`    | the empty string    |
    ///
    /// **Exceptions**
    ///
    /// * `INVALID_CHARACTER_ERR`: Raised if the specified qualified name contains an illegal
    ///   character.
    /// * `NAMESPACE_ERR`: Raised if the `qualifiedName` is malformed, if the `qualifiedName` has
    ///   a `prefix` and the `namespaceURI` is `null`, if the `qualifiedName` has a `prefix` that
    ///   is "xml" and the `namespaceURI` is different from "http://www.w3.org/XML/1998/namespace",
    ///   or if the `qualifiedName` is "xmlns" and the namespaceURI is different from
    ///   "http://www.w3.org/2000/xmlns/".
    ///
    fn create_element_ns(&self, namespace_uri: &str, qualified_name: &str)
        -> Result<Self::NodeRef>;
    ///
    /// Creates a [`ProcessingInstruction`](trait.ProcessingInstruction.html) node given the
    /// specified name and data strings.
    ///
    /// # Specification
    ///
    /// **Parameters**
    ///
    /// * `target` of type `DOMString`: The target part of the processing instruction.
    /// * `data` of type `DOMString`: The `data` for the `node`.
    ///
    /// **Return Value**
    ///
    /// * `ProcessingInstruction`: The new `ProcessingInstruction` object.
    ///
    /// **Exceptions**
    ///
    /// * `INVALID_CHARACTER_ERR`: Raised if the specified target contains an illegal character.
    /// * `NOT_SUPPORTED_ERR`: Raised if this document is an HTML document.
    ///
    fn create_processing_instruction(
        &self,
        target: &str,
        data: Option<&str>,
    ) -> Result<Self::NodeRef>;
    ///
    /// Creates a [`Text`](trait.Text.html) node given the specified string.
    ///
    /// # Specification
    ///
    /// **Parameters**
    ///
    /// * `data` of type `DOMString`: The data for the node.
    ///
    /// **Return Value**
    ///
    /// * `Text`: The new Text object.
    ///
    fn create_text_node(&self, data: &str) -> Self::NodeRef;
    ///
    /// Returns the [`Element`](trait.Element.html) whose ID is given by `elementId`.
    ///
    /// **Note:** This implementation will ensure that attributes named `xml:id` or `id` with the
    /// XML namespace will be treated as identifiers. If the
    /// [`ProcessingOptions::set_assume_ids`](struct.ProcessingOptions.html#method.set_assume_ids)
    /// method is used when constructing a document any attribute with the local name `id` will
    /// be treated as identifiers.
    ///
    /// # Specification
    ///
    /// If no such element exists, returns `null`. Behavior is not defined if more than one element
    /// has this ID.
    ///
    /// **Note:** The DOM implementation must have information that says which attributes are of type
    /// ID. Attributes with the name "ID" are not of type ID unless so defined. Implementations
    /// that do not know whether attributes are of type ID or not are expected to return `null`.
    ///
    /// **Parameters**
    ///
    /// * `elementId` of type `DOMString`: The unique id value for an element.
    ///
    /// **Return Value**
    ///
    /// * `Element`: The matching element.
    ///
    fn get_element_by_id(&self, id: &str) -> Option<Self::NodeRef>;
    ///
    /// Returns a `NodeList` of all the [`Element`](trait.Element.html)s with a given tag name in the
    /// order in which they are encountered in a preorder traversal of the Document tree.
    ///
    /// **Note:** This method will panic if `document_element` is not an `Element` node.
    ///
    /// # Specification
    ///
    /// **Parameters**
    ///
    /// * `tagname` of type `DOMString`: The name of the tag to match on. The special value "*"
    ///   matches all tags.
    ///
    /// **Return Value**
    ///
    /// * `NodeList`: A new `NodeList` object containing all the matched `Element`s.
    ///
    fn get_elements_by_tag_name(&self, tag_name: &str) -> Vec<Self::NodeRef>;
    ///
    /// Returns a `NodeList` of all the [`Element`](trait.Element.html)s with a given local name and
    /// namespace URI in the order in which they are encountered in a preorder traversal of the
    /// Document tree.
    ///
    /// **Note:** This method will panic if `document_element` is not an `Element` node.
    ///
    /// # Specification
    ///
    /// **Parameters**
    ///
    /// * `namespaceURI` of type `DOMString`: The namespace URI of the elements to match on. The
    ///   special value "*" matches all namespaces.
    /// * `localName` of type `DOMString`: The local name of the elements to match on. The special
    ///   value "*" matches all local names.
    ///
    /// **Return Value**
    ///
    /// * `NodeList`: A new `NodeList` object containing all the matched `Element`s.
    ///
    fn get_elements_by_tag_name_ns(
        &self,
        namespace_uri: &str,
        local_name: &str,
    ) -> Vec<Self::NodeRef>;
}

// ------------------------------------------------------------------------------------------------

///
/// This corresponds to the DOM `DocumentFragment` interface (current unsupported).
///
/// # Specification
///
/// `DocumentFragment` is a "lightweight" or "minimal" [`Document`](trait.Document.html) object. It
/// is very common to want to be able to extract a portion of a document's tree or to create a new
/// fragment of a document. Imagine implementing a user command like cut or rearranging a document
/// by moving fragments around. It is desirable to have an object which can hold such fragments and
/// it is quite natural to use a Node for this purpose. While it is true that a `Document` object
/// could fulfill this role, a `Document` object can potentially be a heavyweight object, depending
/// on the underlying implementation. What is really needed for this is a very lightweight object.
/// `DocumentFragment` is such an object.
///
/// Furthermore, various operations -- such as inserting nodes as children of another Node -- may
/// take `DocumentFragment` objects as arguments; this results in all the child nodes of the
/// `DocumentFragment` being moved to the child list of this node.
///
/// The children of a `DocumentFragment` node are zero or more nodes representing the tops of any
/// sub-trees defining the structure of the document. `DocumentFragment` nodes do not need to be
/// well-formed XML documents (although they do need to follow the rules imposed upon well-formed
/// XML parsed entities, which can have multiple top nodes). For example, a `DocumentFragment`
/// might have only one child and that child node could be a [`Text`](trait.Text.html) node. Such a
/// structure model represents neither an HTML document nor a well-formed XML document.
///
/// When a `DocumentFragment` is inserted into a `Document` (or indeed any other `Node` that may
/// take children) the children of the `DocumentFragment` and not the `DocumentFragment` itself are
/// inserted into the `Node`. This makes the `DocumentFragment` very useful when the user wishes
/// to create nodes that are siblings; the `DocumentFragment` acts as the parent of these nodes
/// so that the user can use the standard methods from the [`Node`](trait.Node.html) interface, such as
/// `insertBefore` and `appendChild`.
///
pub trait DocumentFragment: Node {}

// ------------------------------------------------------------------------------------------------

///
/// This corresponds to the DOM `DocumentType` interface.
///
/// # Specification
///
/// Each [`Document`](trait.Document.html) has a `doctype` attribute whose value is either `null` or
/// a `DocumentType` object. The `DocumentType` interface in the DOM Core provides an interface
/// to the list of entities that are defined for the document, and little else because the effect
/// of namespaces and the various XML schema efforts on DTD representation are not clearly
/// understood as of this writing.
///
/// The DOM Level 2 doesn't support editing `DocumentType` nodes.
///
pub trait DocumentType: Node {
    ///
    /// A `NamedNodeMap` containing the general entities, both external and internal, declared in
    /// the DTD. Parameter entities are not contained. Duplicates are discarded. For example in:
    ///
    /// ```xml
    /// <!DOCTYPE ex SYSTEM "ex.dtd" [
    ///   <!ENTITY foo "foo">
    ///   <!ENTITY bar "bar">
    ///   <!ENTITY bar "bar2">
    ///   <!ENTITY % baz "baz">
    /// ]>
    /// <ex/>
    /// ```
    ///
    /// the interface provides access to `foo` and the first declaration of `bar` but not the
    /// second declaration of `bar` or `baz`. Every node in this map also implements the `Entity`
    /// interface.
    ///
    /// The DOM Level 2 does not support editing entities, therefore `entities` cannot be altered
    /// in any way.
    ///
    fn entities(&self) -> HashMap<Name, Self::NodeRef>;
    ///
    /// A `NamedNodeMap` containing the notations declared in the DTD. Duplicates are discarded.
    /// Every node in this map also implements the `Notation` interface.
    ///
    /// The DOM Level 2 does not support editing notations, therefore `notations` cannot be altered
    /// in any way.
    ///
    fn notations(&self) -> HashMap<Name, Self::NodeRef>;
    /// The public identifier of the external subset.
    fn public_id(&self) -> Option<String>;
    /// The system identifier of the external subset.
    fn system_id(&self) -> Option<String>;
    ///
    /// The internal subset as a string.
    ///
    /// **Note:** The actual content returned depends on how much information is available to the
    /// implementation. This may vary depending on various parameters, including the XML processor
    /// used to build the document.
    ///
    fn internal_subset(&self) -> Option<String>;
}

// ------------------------------------------------------------------------------------------------

///
/// This corresponds to the DOM `DOMImplementation` interface.
///
/// The instance used to create a document can be retrieved using the `implementation` method on
/// [`Document`](trait.Document.html). To fetch an implementation to create a document iun the
/// first place use the function [`get_implementation`](fn.get_implementation.html).
///
/// # Specification
///
/// The `DOMImplementation` interface provides a number of methods for performing operations that
/// are independent of any particular instance of the document object model.
///
pub trait DOMImplementation {
    ///
    /// The opaque reference type that wraps the implementation of a node within the DOM.
    ///
    type NodeRef;
    ///
    /// Creates an XML Document object of the specified type with its document element.
    ///
    /// **Note:** This method will panic if it cannot create the document node.
    ///
    /// **Note**: This will create a new document that includes namespace support and strict ID
    /// processing. If you wish to change these options, see
    /// [`create_document_with_options`](ext/trait.DOMImplementation.html#method.create_document_with_options)
    ///
    /// # Specification
    ///
    /// HTML-only DOM
    /// implementations do not need to implement this method. **Introduced in DOM Level 2**
    ///
    /// **Parameters**
    ///
    /// * `namespaceURI` of type `DOMString`: The namespace URI of the document element to create.
    /// * `qualifiedName` of type `DOMString`: The qualified name of the document element to be created.
    /// * `doctype` of type `DocumentType`: The type of document to be created or null.
    ///   When doctype is not null, its Node.ownerDocument attribute is set to the document being created.
    ///
    /// **Return Value**
    ///
    /// `Document`: A new Document object.
    ///
    /// **Exceptions**
    ///
    /// * `INVALID_CHARACTER_ERR`: Raised if the specified qualified name contains an illegal character.
    /// * `NAMESPACE_ERR`: Raised if the qualifiedName is malformed, if the qualifiedName has a prefix
    ///   and the namespaceURI is null, or if the qualifiedName has a prefix that is "xml" and the
    ///   namespaceURI is different from "http://www.w3.org/XML/1998/namespace".
    /// * `WRONG_DOCUMENT_ERR`: Raised if doctype has already been used with a different document or
    ///   was created from a different implementation.
    ///
    fn create_document(
        &self,
        namespace_uri: Option<&str>,
        qualified_name: Option<&str>,
        doc_type: Option<Self::NodeRef>,
    ) -> Result<Self::NodeRef>;
    ///
    /// Creates an empty `DocumentType` node.
    ///
    /// # Specification
    ///
    /// Entity declarations and notations are not made available. Entity reference expansions and
    /// default attribute additions do not occur. It is expected that a future version of the DOM
    /// will provide a way for populating a `DocumentType`. **Introduced in DOM Level 2**
    ///
    /// HTML-only DOM implementations do not need to implement this method.
    ///
    /// **Parameters**
    ///
    /// * `qualifiedName` of type `DOMString`: The qualified name of the document type to be created.
    /// * `publicId` of type `DOMString`: The external subset public identifier.
    /// * `systemId` of type `DOMString`: The external subset system identifier.
    ///
    /// **Return Value**
    ///
    /// `DocumentType`: A new `DocumentType` node with `Node.ownerDocument` set to null.
    ///
    /// **Exceptions**
    ///
    /// * `INVALID_CHARACTER_ERR`: Raised if the specified qualified name contains an illegal character.
    /// * `NAMESPACE_ERR`: Raised if the `qualifiedName` is malformed.
    ///
    fn create_document_type(
        &self,
        qualified_name: &str,
        public_id: Option<&str>,
        system_id: Option<&str>,
    ) -> Result<Self::NodeRef>;
    ///
    /// Test if the DOM implementation implements a specific feature.
    ///
    /// # Specification
    ///
    /// See DOM Level 2 Core [§1.3. Extended Interfaces](https://www.w3.org/TR/DOM-Level-2-Core/core.html#ID-E067D597)
    ///
    /// **Parameters**
    ///
    /// * `feature` of type `DOMString`: The name of the feature to test (case-insensitive). The
    ///   values used by DOM features are defined throughout the DOM Level 2 specifications and
    ///   listed in the Conformance section. The name must be an XML name. To avoid possible
    ///   conflicts, as a convention, names referring to features defined outside the DOM
    ///   specification should be made unique by reversing the name of the Internet domain name of
    ///   the person (or the organization that the person belongs to) who defines the feature,
    ///   component by component, and using this as a prefix. For instance, the W3C SVG Working
    ///   Group defines the feature "org.w3c.dom.svg".
    /// * `version` of type `DOMString`: This is the version number of the feature to test. In
    ///   Level 2, the string can be either "2.0" or "1.0". If the version is not specified,
    ///   supporting any version of the feature causes the method to return true.
    ///
    /// **Return Value**
    ///
    /// `boolean`: true if the feature is implemented in the specified version, false otherwise.
    ///
    /// **No Exceptions**
    ///
    fn has_feature(&self, feature: &str, version: &str) -> bool;
}

// ------------------------------------------------------------------------------------------------

///
/// This corresponds to the DOM `Element` interface.
///
/// # Specification
///
/// The `Element` interface represents an element in an HTML or XML document. Elements may have
/// attributes associated with them; since the `Element` interface inherits from [`Node`](trait.Node.html),
/// the generic `Node` interface attribute attributes may be used to retrieve the set of all
/// attributes for an element. There are methods on the `Element` interface to retrieve either an
/// [`Attr`](trait.Attribute.html) object by name or an attribute value by name. In XML, where an
/// attribute value may contain entity references, an `Attr` object should be retrieved to examine
/// the possibly fairly complex sub-tree representing the attribute value. On the other hand, in
/// HTML, where all attributes have simple string values, methods to directly access an attribute
/// value can safely be used as a convenience.
///
/// **Note:** In DOM Level 2, the method `normalize` is inherited from the `Node` interface where
/// it was moved.
///
pub trait Element: Node {
    ///
    /// The name of the element.
    ///
    /// # Specification
    ///
    /// For example, in:
    ///
    /// ```xml
    /// <elementExample id="demo">
    ///         ...
    /// </elementExample>
    /// ```
    ///
    /// `tagName` has the value "elementExample". Note that this is case-preserving in XML, as
    /// are all of the operations of the DOM. The HTML DOM returns the `tagName` of an HTML element
    /// in the canonical uppercase form, regardless of the case in the source HTML document.
    ///
    fn tag_name(&self) -> String {
        Node::node_name(self).to_string()
    }
    ///
    /// Retrieves an attribute value by name.
    ///
    /// # Specification
    ///
    /// **Parameters**
    ///
    /// * `name` of type `DOMString`: The name of the attribute to retrieve.
    ///
    /// **Return Value**
    ///
    /// * `DOMString`: The `Attr` value as a string, or the empty string if that attribute does not
    /// have a specified or default value.
    ///
    fn get_attribute(&self, name: &str) -> Option<String>;
    ///
    /// Adds a new attribute.
    ///
    /// # Specification
    ///
    /// If an attribute with that name is already present in the element, its value is changed to
    /// be that of the value parameter. This value is a simple string; it is not parsed as it is
    /// being set. So any markup (such as syntax to be recognized as an entity reference) is
    /// treated as literal text, and needs to be appropriately escaped by the implementation when
    /// it is written out. In order to assign an attribute value that contains entity references,
    /// the user must create an Attr node plus any Text and EntityReference nodes, build the
    /// appropriate subtree, and use setAttributeNode to assign it as the value of an attribute.
    ///
    /// To set an attribute with a qualified name and namespace URI, use the `setAttributeNS` method.
    ///
    /// **Parameters**
    ///
    /// * `name` of type `DOMString`: The name of the attribute to create or alter.
    /// `value` of type `DOMString`: Value to set in string form.
    ///
    /// **Exceptions**
    ///
    /// * `INVALID_CHARACTER_ERR`: Raised if the specified name contains an illegal character.
    /// * `NO_MODIFICATION_ALLOWED_ERR`: Raised if this node is readonly.
    ///
    fn set_attribute(&mut self, name: &str, value: &str) -> Result<()>;
    ///
    /// Removes an attribute by name. If the removed attribute is known to have a default value, an
    /// attribute immediately appears containing the default value as well as the corresponding
    /// namespace URI, local name, and prefix when applicable.
    ///
    /// # Specification
    ///
    /// To remove an attribute by local name and namespace URI, use the `removeAttributeNS` method.
    ///
    /// **Parameters**
    ///
    /// * `name` of type `DOMString`: The name of the attribute to remove.
    ///
    /// **Exceptions**
    ///
    /// * `NO_MODIFICATION_ALLOWED_ERR`: Raised if this node is readonly.
    ///
    fn remove_attribute(&mut self, _name: &str) -> Result<()>;
    ///
    /// Retrieves an attribute node by name.
    ///
    /// # Specification
    ///
    /// To retrieve an attribute node by qualified name and namespace URI, use the
    /// `getAttributeNodeNS` method.
    ///
    /// **Parameters**
    ///
    /// * `name` of type `DOMString`: The name (`nodeName`) of the attribute to retrieve.
    ///
    /// **Return Value**
    ///
    /// * `Attr`: The `Attr` node with the specified name (`nodeName`) or null if there is no such
    /// attribute.
    ///
    fn get_attribute_node(&self, name: &str) -> Option<Self::NodeRef>;
    ///
    /// Adds a new attribute node.
    ///
    /// # Specification
    ///
    /// If an attribute with that name (`nodeName`) is already present in the element, it is
    /// replaced by the new one.
    ///
    /// To add a new attribute node with a qualified name and namespace URI, use the
    /// `setAttributeNodeNS` method.
    ///
    /// **Parameters**
    ///
    /// * `newAttr` of type `Attr`: The `Attr` node to add to the attribute list.
    ///
    /// **Return Value**
    ///
    /// * `Attr`: If the `newAttr` attribute replaces an existing attribute, the replaced `Attr`
    ///   node is returned, otherwise `null` is returned.
    ///
    /// **Exceptions**
    ///
    /// * `WRONG_DOCUMENT_ERR`: Raised if `newAttr` was created from a different document than the
    ///   one that created the element.
    /// * `NO_MODIFICATION_ALLOWED_ERR`: Raised if this node is readonly.
    /// * `INUSE_ATTRIBUTE_ERR`: Raised if `newAttr` is already an attribute of another `Element`
    ///   object. The DOM user must explicitly clone `Attr` nodes to re-use them in other elements.
    ///
    fn set_attribute_node(&mut self, new_attribute: Self::NodeRef) -> Result<Self::NodeRef>;
    ///
    /// Removes the specified attribute node.
    ///
    /// # Specification
    ///
    /// If the removed `Attr` has a default value it is immediately replaced. The replacing
    /// attribute has the same namespace URI and local name, as well as the original prefix, when
    /// applicable.
    ///
    /// **Parameters**
    ///
    /// * `oldAttr` of type `Attr`: The `Attr` node to remove from the attribute list.
    ///
    /// **Return Value**
    ///
    /// * `Attr`: The `Attr` node that was removed.
    ///
    /// **Exceptions**
    ///
    /// * `NO_MODIFICATION_ALLOWED_ERR`: Raised if this node is readonly.
    /// * `NOT_FOUND_ERR`: Raised if oldAttr is not an attribute of the element.
    ///
    fn remove_attribute_node(&mut self, _old_attribute: Self::NodeRef) -> Result<Self::NodeRef>;
    ///
    /// Returns a `NodeList` of all descendant `Element`s with a given tag name, in the order in
    /// which they are encountered in a preorder traversal of this `Element` tree.
    ///
    /// # Specification
    ///
    /// **Parameters**
    ///
    /// * `name` of type `DOMString`: The name of the tag to match on. The special value "*" matches
    ///   all tags.
    ///
    /// **Return Value**
    ///
    /// * `NodeList`: A list of matching `Element` nodes.
    ///
    fn get_elements_by_tag_name(&self, _tag_name: &str) -> Vec<Self::NodeRef>;
    ///
    /// Retrieves an attribute value by local name and namespace URI.
    ///
    /// # Specification
    ///
    /// HTML-only DOM implementations do not need to implement this method.
    ///
    /// **Parameters**
    ///
    /// * `namespaceURI` of type `DOMString`: The namespace URI of the attribute to retrieve.
    /// * `localName` of type `DOMString`: The local name of the attribute to retrieve.
    ///
    /// **Return Value**
    ///
    /// * `DOMString`: The `Attr` value as a string, or the empty string if that attribute does not
    ///   have a specified or default value.
    ///
    fn get_attribute_ns(&self, _namespace_uri: &str, _local_name: &str) -> Option<String>;
    ///
    /// Adds a new attribute.
    ///
    /// # Specification
    ///
    /// If an attribute with the same local name and namespace URI is already present on the
    /// element, its `prefix` is changed to be the prefix part of the `qualifiedName`, and its
    /// `value` is changed to be the value parameter. This value is a simple string; it is not
    /// parsed as it is being set. So any markup (such as syntax to be recognized as an entity
    /// reference) is treated as literal text, and needs to be appropriately escaped by the
    /// implementation when it is written out. In order to assign an attribute value that contains
    /// entity references, the user must create an `Attr` node plus any `Text` and `EntityReference`
    /// nodes, build the appropriate subtree, and use `setAttributeNodeNS` or `setAttributeNode`
    /// to assign it as the value of an attribute.
    ///
    /// HTML-only DOM implementations do not need to implement this method.
    ///
    /// **Parameters**
    ///
    /// * `namespaceURI` of type `DOMString`: The namespace URI of the attribute to create or alter.
    /// * `qualifiedName` of type `DOMString`: The qualified name of the attribute to create or alter.
    /// * `value` of type `DOMString`: The value to set in string form.
    ///
    /// **Exceptions**
    ///
    /// * `INVALID_CHARACTER_ERR`: Raised if the specified qualified name contains an illegal character.
    /// * `NO_MODIFICATION_ALLOWED_ERR`: Raised if this node is readonly.
    /// * `NAMESPACE_ERR`: Raised if the `qualifiedName` is malformed, if the `qualifiedName` has a
    ///   prefix and the `namespaceURI` is null, if the `qualifiedName` has a prefix that is "xml"
    ///   and the `namespaceURI` is different from "http://www.w3.org/XML/1998/namespace", or if
    ///   the `qualifiedName` is "xmlns" and the `namespaceURI` is different from
    /// "http://www.w3.org/2000/xmlns/".
    ///
    fn set_attribute_ns(
        &mut self,
        namespace_uri: &str,
        qualified_name: &str,
        value: &str,
    ) -> Result<()>;
    ///
    /// Removes an attribute by local name and namespace URI.
    ///
    /// # Specification
    ///
    /// If the removed attribute has a default value it is immediately replaced. The replacing
    /// attribute has the same namespace URI and local name, as well as the original prefix.
    ///
    /// HTML-only DOM implementations do not need to implement this method.
    ///
    /// **Parameters**
    ///
    /// * `namespaceURI` of type `DOMString`: The namespace URI of the attribute to remove.
    /// * `localName` of type `DOMString`: The local name of the attribute to remove.
    ///
    /// **Exceptions**
    ///
    /// * `NO_MODIFICATION_ALLOWED_ERR`: Raised if this node is readonly.
    ///
    fn remove_attribute_ns(&mut self, _namespace_uri: &str, _local_name: &str) -> Result<()>;
    ///
    /// Retrieves an Attr node by local name and namespace URI.
    ///
    /// # Specification
    ///
    /// HTML-only DOM implementations do not need to implement this method.
    ///
    /// **Parameters**
    ///
    /// * `namespaceURI` of type `DOMString`: The namespace URI of the attribute to retrieve.
    /// * `localName` of type `DOMString`: The local name of the attribute to retrieve.
    ///
    /// **Return Value**
    ///
    /// * `Attr`: The `Attr` node with the specified attribute local name and namespace URI or
    ///   `null` if there is no such attribute.
    ///
    fn get_attribute_node_ns(
        &self,
        _namespace_uri: &str,
        _local_name: &str,
    ) -> Option<Self::NodeRef>;
    ///
    /// Adds a new attribute.
    ///
    /// # Specification
    ///
    /// If an attribute with that local name and that namespace URI is already present in the
    /// element, it is replaced by the new one.
    ///
    /// HTML-only DOM implementations do not need to implement this method.
    ///
    /// **Parameters**
    ///
    /// * `newAttr` of type `Attr`: The `Attr` node to add to the attribute list.
    ///
    /// **Return Value**
    ///
    /// * `Attr`: If the `newAttr` attribute replaces an existing attribute with the same local name
    ///   and namespace URI, the replaced `Attr` node is returned, otherwise `null` is returned.
    ///
    /// **Exceptions**
    ///
    /// * `WRONG_DOCUMENT_ERR`: Raised if newAttr was created from a different document than the
    ///   one that created the element.
    /// * `NO_MODIFICATION_ALLOWED_ERR`: Raised if this node is readonly.
    /// * `INUSE_ATTRIBUTE_ERR`: Raised if `newAttr` is already an attribute of another `Element`
    ///   object. The DOM user must explicitly clone `Attr` nodes to re-use them in other elements.
    ///
    fn set_attribute_node_ns(&mut self, _new_attribute: Self::NodeRef) -> Result<Self::NodeRef>;
    ///
    /// Returns a `NodeList` of all the descendant `Element`s with a given local name and namespace
    /// URI in the order in which they are encountered in a preorder traversal of this Element tree.
    ///
    /// # Specification
    ///
    /// HTML-only DOM implementations do not need to implement this method.
    ///
    /// **Parameters**
    ///
    /// * `namespaceURI` of type `DOMString`: The namespace URI of the elements to match on. The
    ///   special value "*" matches all namespaces.
    /// * `localName` of type `DOMString`: The local name of the elements to match on. The special
    ///   value "*" matches all local names.
    ///
    /// **Return Value**
    ///
    /// * `NodeList`: A new `NodeList` object containing all the matched `Element`s.
    ///
    fn get_elements_by_tag_name_ns(
        &self,
        _namespace_uri: &str,
        _local_name: &str,
    ) -> Vec<Self::NodeRef>;
    ///
    /// Returns `true` when an attribute with a given name is specified on this element or has a default
    /// value, `false` otherwise.
    ///
    /// # Specification
    ///
    /// **Parameters**
    ///
    /// * `name` of type `DOMString`: The name of the attribute to look for.
    ///
    /// **Return Value**
    ///
    /// * `boolean`: `true` if an attribute with the given name is specified on this element or
    ///   has a default value, `false` otherwise.
    ///
    fn has_attribute(&self, name: &str) -> bool;
    ///
    /// Returns `true` when an attribute with a given local name and namespace URI is specified on
    /// this element or has a default value, `false` otherwise.
    ///
    /// # Specification
    ///
    /// HTML-only DOM implementations do not need to implement this method.
    ///
    /// **Parameters**
    ///
    /// * `namespaceURI` of type `DOMString`: The namespace URI of the attribute to look for.
    /// `localName` of type `DOMString`: The local name of the attribute to look for.
    ///
    /// **Return Value**
    ///
    /// * `boolean`: `true` if an attribute with the given local name and namespace URI is
    ///   specified or has a default value on this element, `false` otherwise.
    ///
    fn has_attribute_ns(&self, namespace_uri: &str, local_name: &str) -> bool;
}

// ------------------------------------------------------------------------------------------------

///
/// This corresponds to the DOM `Entity` interface.
///
/// # Specification
///
/// This interface represents an entity, either parsed or unparsed, in an XML document. Note that
/// this models the entity itself not the entity declaration. Entity declaration modeling has
/// been left for a later Level of the DOM specification.
///
/// The nodeName attribute that is inherited from Node contains the name of the entity.
///
/// An XML processor may choose to completely expand entities before the structure model is passed
/// to the DOM; in this case there will be no `EntityReference` nodes in the document tree.
///
/// XML does not mandate that a non-validating XML processor read and process entity declarations
/// made in the external subset or declared in external parameter entities. This means that parsed
/// entities declared in the external subset need not be expanded by some classes of applications,
/// and that the replacement value of the entity may not be available. When the replacement value
/// is available, the corresponding `Entity` node's child list represents the structure of that
/// replacement text. Otherwise, the child list is empty.
///
/// The DOM Level 2 does not support editing `Entity` nodes; if a user wants to make changes to
/// the contents of an `Entity`, every related `EntityReference` node has to be replaced in the
/// structure model by a clone of the `Entity`'s contents, and then the desired changes must be
/// made to each of those clones instead. `Entity` nodes and all their descendants are readonly.
///
/// An `Entity` node does not have any parent.
///
/// **Note:** If the entity contains an unbound namespace prefix, the` namespaceURI` of the
/// corresponding node in the `Entity` node subtree is `null`. The same is true for
/// `EntityReference` nodes that refer to this entity, when they are created using the
/// `createEntityReference` method of the [`Document`](trait.Document.html) interface. The DOM
/// Level 2 does not support any mechanism to resolve namespace prefixes.
///
pub trait Entity: Node {
    ///
    /// The public identifier associated with the entity, if specified.
    ///
    /// # Specification
    ///
    /// If the public identifier was not specified, this is `null`.
    ///
    fn public_id(&self) -> Option<String>;
    ///
    /// The system identifier associated with the entity, if specified.
    ///
    /// # Specification
    ///
    /// If the system identifier was not specified, this is `null`.
    ///
    fn system_id(&self) -> Option<String>;
    ///
    /// For unparsed entities, the name of the notation for the entity.
    ///
    ///# Specification
    ///
    /// For parsed entities, this is `null`.
    ///
    fn notation_name(&self) -> Option<String>;
}

// ------------------------------------------------------------------------------------------------

///
/// This corresponds to the DOM `EntityReference` interface.
///
/// # Specification
///
/// `EntityReference` objects may be inserted into the structure model when an entity reference
/// is in the source document, or when the user wishes to insert an entity reference. Note that
/// character references and references to predefined entities are considered to be expanded by
/// the HTML or XML processor so that characters are represented by their Unicode equivalent rather
/// than by an entity reference. Moreover, the XML processor may completely expand references to
/// entities while building the structure model, instead of providing `EntityReference` objects. If
/// it does provide such objects, then for a given `EntityReference` node, it may be that there is
/// no `Entity` node representing the referenced entity. If such an `Entity` exists, then the
/// subtree of the `EntityReference` node is in general a copy of the `Entity` node subtree.
/// However, this may not be true when an entity contains an unbound namespace prefix. In such a
/// case, because the namespace prefix resolution depends on where the entity reference is, the
/// descendants of the `EntityReference` node may be bound to different namespace URIs.
///
/// As for `Entity` nodes, `EntityReference` nodes and all their descendants are readonly.
///
pub trait EntityReference: Node {}

// ------------------------------------------------------------------------------------------------

///
/// This corresponds to the DOM `Node` interface.
///
/// # Specification
///
/// The `Node` interface is the primary datatype for the entire Document Object Model. It represents
/// a single node in the document tree. While all objects implementing the `Node` interface expose
/// methods for dealing with children, not all objects implementing the `Node` interface may have
/// children. For example, `Text` nodes may not have children, and adding children to such nodes
/// results in a `DOMException` being raised.
///
/// The attributes `nodeName`, `nodeValue` and `attributes` are included as a mechanism to get at node
/// information without casting down to the specific derived interface. In cases where there is no
/// obvious mapping of these attributes for a specific nodeType (e.g., `nodeValue` for an `Element` or
/// `attributes` for a `Comment`), this returns `null`. Note that the specialized interfaces may contain
/// additional and more convenient mechanisms to get and set the relevant information.
///
/// The values of `nodeName`, `nodeValue`, and `attributes` vary according to the node type as follows:
///
///
/// | Interface               | nodeName                  | nodeValue                           | attributes   |
/// |-------------------------|---------------------------|-------------------------------------|--------------|
/// | `Attr`                  | name of attribute         | value of attribute                  | `None`       |
/// | `CDATASection`          | `"#cdata-section"`        | content of the CDATA Section        | `None`       |
/// | `Comment`               | `"#comment"`              | content of the comment              | `None`       |
/// | `Document`              | `"#document"`             | `None`                              | `None`       |
/// | `DocumentFragment`      | `"#document-fragment"`    | `None`                              | `None`       |
/// | `DocumentType`          | document type name        | `None`                              | `None`       |
/// | `Element`               | tag name                  | `None`                              | `HashMap`    |
/// | `Entity`                | entity name               | `None`                              | `None`       |
/// | `EntityReference`       | name of entity referenced | `None`                              | `None`       |
/// | `Notation`              | notation name             | `None`                              | `None`       |
/// | `ProcessingInstruction` | `target`                  | entire content excluding the target | `None`       |
/// | `Text`                  | `"#text"`                 | content of the text node            | `None`       |
///
pub trait Node {
    ///
    /// The opaque reference type that wraps the implementation of a node within the DOM.
    ///
    type NodeRef;
    ///
    /// The name of this node, depending on its type; see the table above.
    ///
    fn node_name(&self) -> Name;
    ///
    /// The value of this node, depending on its type; see the table above. When it is defined to
    /// be `None`, setting it has no effect.
    ///
    /// # Specification
    ///
    /// **Exceptions on setting**
    ///
    /// * `NO_MODIFICATION_ALLOWED_ERR`: Raised when the node is readonly.
    ///
    /// **Exceptions on retrieval**
    ///
    /// * `DOMSTRING_SIZE_ERR`: Raised when it would return more characters than fit in a DOMString
    /// variable on the implementation platform.
    ///
    fn node_value(&self) -> Option<String>;
    ///
    /// Set the `value` for the node; see [`node_value`](#tymethod.node_value).
    ///
    fn set_node_value(&mut self, value: &str) -> Result<()>;
    ///
    /// Set the `value` for the node to `None`; see [`node_value`](#tymethod.node_value).
    ///
    fn unset_node_value(&mut self) -> Result<()>;
    ///
    /// A code representing the type of the underlying object.
    ///
    fn node_type(&self) -> NodeType;
    ///
    /// The parent of this node. All nodes, except `Attr`, `Document`, `DocumentFragment`,
    /// `Entity`, and `Notation` may have a parent. However, if a node has just been created and not
    /// yet added to the tree, or if it has been removed from the tree, this is `None`.
    ///
    fn parent_node(&self) -> Option<Self::NodeRef>;
    ///
    /// A `Vec` that contains all children of this node. If there are no children,
    /// this is a `Vec` containing no nodes.
    ///
    fn child_nodes(&self) -> Vec<Self::NodeRef>;
    ///
    /// The first child of this node. If there is no such node, this returns `None`.
    ///
    fn first_child(&self) -> Option<Self::NodeRef>;
    ///
    /// The last child of this node. If there is no such node, this returns `None`.
    ///
    fn last_child(&self) -> Option<Self::NodeRef>;
    ///
    /// The node immediately preceding this node. If there is no such node, this returns `None`.
    ///
    fn previous_sibling(&self) -> Option<Self::NodeRef>;
    ///
    /// The node immediately following this node. If there is no such node, this returns `None`.
    ///
    fn next_sibling(&self) -> Option<Self::NodeRef>;
    ///
    /// A `HashMap` containing the attributes of this node (if it is an `Element`) or
    /// `None` otherwise.
    ///
    fn attributes(&self) -> HashMap<Name, Self::NodeRef>;
    ///
    /// The `Document` object associated with this node. This is also the `Document`
    /// object used to create new nodes. When this node is a `Document` or a `DocumentType` which is
    /// not used with any `Document` yet, this is `None`.
    ///
    fn owner_document(&self) -> Option<Self::NodeRef>;
    ///
    /// Inserts the node `newChild` before the existing child node `refChild`.
    ///
    /// # Specification
    ///
    /// If `refChild` is `null`, insert `newChild` at the end of the list of children.
    ///
    /// If `newChild` is a `DocumentFragment` object, all of its children are inserted, in the
    /// same order, before `refChild`. If the `newChild` is already in the tree, it is first removed.
    ///
    /// **Parameters**
    ///
    /// * `newChild` of type `Node`: The node to insert.
    /// * `refChild `of type `Node`: The reference node, i.e., the node before which the new node
    ///   must be inserted.
    ///
    /// **Return Value**
    ///
    /// * `Node`: The node being inserted.
    ///
    /// **Exceptions**
    ///
    /// * `HIERARCHY_REQUEST_ERR`: Raised if this node is of a type that does not allow children
    ///   of the type of the `newChild` node, or if the node to insert is one of this node's
    ///   ancestors.
    /// * `WRONG_DOCUMENT_ERR`: Raised if `newChild` was created from a different document than the
    ///   one that created this node.
    /// * `NO_MODIFICATION_ALLOWED_ERR`: Raised if this node is readonly or if the parent of the
    ///   node being inserted is readonly.
    /// * `NOT_FOUND_ERR`: Raised if `refChild` is not a child of this node.
    ///
    fn insert_before(
        &mut self,
        new_child: Self::NodeRef,
        ref_child: Option<Self::NodeRef>,
    ) -> Result<Self::NodeRef>;
    ///
    /// Replaces the child node `oldChild` with `newChild` in the list of children, and returns the
    /// `oldChild` node.
    ///
    /// # Specification
    ///
    /// If `newChild` is a `DocumentFragment` object, `oldChild` is replaced by all of the
    /// `DocumentFragment` children, which are inserted in the same order. If the `newChild` is
    /// already in the tree, it is first removed.
    ///
    /// **Parameters**
    ///
    /// * `newChild` of type `Node`: The new node to put in the child list.
    /// * `oldChild` of type `Node`: The node being replaced in the list.
    ///
    /// **Return Value**
    ///
    /// * `Node`: The node replaced.
    ///
    /// **Exceptions**
    ///
    /// * `HIERARCHY_REQUEST_ERR`: Raised if this node is of a type that does not allow children of
    ///   the type of the newChild node, or if the node to put in is one of this node's ancestors.
    /// * `WRONG_DOCUMENT_ERR`: Raised if `newChild` was created from a different document than the
    ///   one that created this node.
    /// * `NO_MODIFICATION_ALLOWED_ERR`: Raised if this node or the parent of the new node is readonly.
    /// * `NOT_FOUND_ERR`: Raised if oldChild is not a child of this node.
    ///
    fn replace_child(
        &mut self,
        new_child: Self::NodeRef,
        old_child: Self::NodeRef,
    ) -> Result<Self::NodeRef>;
    ///
    /// Removes the child node indicated by oldChild from the list of children, and returns it.
    ///
    /// # Specification
    ///
    /// **Parameters**
    ///
    /// * `oldChild` of type `Node`: The node being removed.
    ///
    /// **Return Value**
    ///
    /// * `Node`: The node removed.
    ///
    /// **Exceptions**
    ///
    /// * `NO_MODIFICATION_ALLOWED_ERR`: Raised if this node is readonly.
    /// * `NOT_FOUND_ERR`: Raised if oldChild is not a child of this node.
    ///
    fn remove_child(&mut self, old_child: Self::NodeRef) -> Result<Self::NodeRef>;
    ///
    /// Adds the node `newChild` to the end of the list of children of this node.
    ///
    /// # Specification
    ///
    /// If the `newChild` is already in the tree, it is first removed.
    ///
    /// **Parameters**
    ///
    /// * `newChild` of type `Node`: The node to add. If it is a `DocumentFragment` object, the
    ///   entire contents of the document fragment are moved into the child list of this node.
    ///
    /// **Return Value**
    ///
    /// `Node`: The node added.
    ///
    /// **Exceptions**
    ///
    /// * `HIERARCHY_REQUEST_ERR: Raised if this node is of a type that does not allow children of`
    ///   the type of the `newChild` node, or if the node to append is one of this node's ancestors.
    /// * `WRONG_DOCUMENT_ERR`: Raised if `newChild` was created from a different document than
    ///   the one that created this node.
    /// * `NO_MODIFICATION_ALLOWED_ERR`: Raised if this node is readonly.
    ///
    fn append_child(&mut self, new_child: Self::NodeRef) -> Result<Self::NodeRef>;
    ///
    /// Returns whether this node has any children.
    ///
    /// # Specification
    ///
    /// **Return Value**
    ///
    /// * `boolean`: `true` if this node has any children, `false` otherwise.
    ///
    fn has_child_nodes(&self) -> bool;
    ///
    /// Returns a duplicate of this node, i.e., serves as a generic copy constructor for nodes.
    ///
    /// **Note:** currently unsupported.
    ///
    /// # Specification
    ///
    /// The duplicate node has no parent; (`parentNode` is null.).
    ///
    /// Cloning an [`Element`](trait.Element.html) copies all attributes and their values, including
    /// those generated by the XML processor to represent defaulted attributes, but this method does
    /// not copy any text it contains unless it is a deep clone, since the text is contained in a
    /// child [`Text`](trait.Text.html) node. Cloning an [`Attribute`](trait.Attribute.html) directly,
    /// as opposed to be cloned as part of an `Element` cloning operation, returns a specified
    /// attribute (`specified` is `true`). Cloning any other type of node simply returns a copy of
    /// this node.
    ///
    /// Note that cloning an immutable subtree results in a mutable copy, but the children of an
    /// `EntityReference` clone are readonly. In addition, clones of unspecified `Attr` nodes are
    /// specified. And, cloning `Document`, `DocumentType`, `Entity`, and `Notation` nodes is
    /// implementation dependent.
    ///
    /// **Parameters**
    ///
    /// * `deep` of type `boolean`: If `true`, recursively clone the subtree under the specified
    ///   node; if `false`, clone only the node itself (and its attributes, if it is an `Element`).
    ///
    /// **Return Value**
    ///
    /// * `Node`:The duplicate node.
    ///
    fn clone_node(&self, deep: bool) -> Option<Self::NodeRef>;
    ///
    /// Puts all [`Text`](trait.Text.html) nodes in the full depth of the sub-tree underneath this
    /// `Node`, including attribute nodes, into a "normal" form where only structure (e.g.,
    /// elements, comments, processing instructions, CDATA sections, and entity references)
    /// separates `Text` nodes, i.e., there are neither adjacent `Text` nodes nor empty `Text` nodes.
    ///
    /// # Specification
    ///
    /// This can be used to ensure that the DOM view of a document is the same as if it were saved
    /// and re-loaded, and is useful when operations (such as XPointer lookups) that depend on a
    /// particular document tree structure are to be used.
    ///
    /// Note: In cases where the document contains [`CDataSection`](trait.CDataSection.html), the
    /// normalize operation alone may not be sufficient, since XPointers do not differentiate
    /// between `Text` nodes and `CDATASection` nodes.
    ///
    fn normalize(&mut self);
    ///
    /// Tests whether the DOM implementation implements a specific feature and that feature is
    /// supported by this node.
    ///
    /// **Note:** currently unsupported.
    ///
    /// # Specification
    ///
    /// **Parameters**
    ///
    /// * `feature` of type `DOMString`: The name of the feature to test. This is the same name
    ///   which can be passed to the method `hasFeature` on `DOMImplementation`.
    /// * `version` of type `DOMString`: This is the version number of the feature to test. In
    ///   Level 2, version 1, this is the string "2.0". If the version is not specified, supporting
    ///   any version of the feature will cause the method to return true.
    ///
    /// **Return Value**
    ///
    /// * `boolean`: Returns `true` if the specified feature is supported on this node, `false`
    ///   otherwise.
    ///
    fn is_supported(&self, feature: &str, version: &str) -> bool;
    ///
    /// Returns whether this node (if it is an element) has any attributes.
    ///
    /// **Return Value**
    ///
    /// * `boolean`: `true` if this node has any attributes, `false` otherwise.
    ///
    fn has_attributes(&self) -> bool;
    ///
    /// The namespace URI of this node, or null if it is unspecified.
    ///
    /// # Specification
    ///
    /// This is not a computed value that is the result of a namespace lookup based on an
    /// examination of the namespace declarations in scope. It is merely the namespace URI given
    /// at creation time.
    ///
    /// For nodes of any type other than `ELEMENT_NODE` and `ATTRIBUTE_NODE` and nodes created
    /// with a DOM Level 1 method, such as `createElement` from the `Document` interface, this is
    /// always `null`.
    ///
    /// **Note:** Per the _Namespaces in XML_ Specification an attribute does not inherit its
    /// namespace from the element it is attached to. If an attribute is not explicitly given a
    /// namespace, it simply has no namespace.
    ///
    fn namespace_uri(&self) -> Option<String> {
        self.node_name().namespace_uri
    }
    ///
    /// Returns the local part of the qualified name of this node.
    ///
    /// # Specification
    ///
    /// For nodes of any type other than `ELEMENT_NODE` and `ATTRIBUTE_NODE` and nodes created
    /// with a DOM Level 1 method, such as `createElement` from the `Document` interface, this is
    /// always `null`.
    ///
    fn local_name(&self) -> String {
        self.node_name().local_name
    }
    ///
    /// The namespace prefix of this node, or null if it is unspecified.
    ///
    /// # Specification
    ///
    /// Note that setting this attribute, when permitted, changes the `nodeName` attribute, which
    /// holds the qualified name, as well as the `tagName` and `name` attributes of the `Element`
    /// and `Attr` interfaces, when applicable.
    ///
    /// Note also that changing the prefix of an attribute that is known to have a default value,
    /// does not make a new attribute with the default value and the original prefix appear, since
    /// the `namespaceURI` and `localName` do not change.
    ///
    /// For nodes of any type other than `ELEMENT_NODE` and `ATTRIBUTE_NODE` and nodes created
    /// with a DOM Level 1 method, such as `createElement` from the `Document` interface, this is
    /// always `null`.
    ///
    /// **Exceptions**
    ///
    /// * `INVALID_CHARACTER_ERR`: Raised if the specified prefix contains an illegal character.
    /// * `NO_MODIFICATION_ALLOWED_ERR`: Raised if this node is readonly.
    /// * `NAMESPACE_ERR`: Raised if the specified prefix is malformed, if the `namespaceURI` of this
    ///   node is `null`, if the specified prefix is "xml" and the namespaceURI of this node is
    ///   different from "http://www.w3.org/XML/1998/namespace", if this node is an attribute and
    ///   the specified prefix is "xmlns" and the namespaceURI of this node is different from  
    ///   "http://www.w3.org/2000/xmlns/", or if this node is an attribute and the `qualifiedName`
    ///   of this node is "xmlns".
    ///
    fn prefix(&self) -> Option<String> {
        self.node_name().prefix
    }
}

// ------------------------------------------------------------------------------------------------

///
/// This corresponds to the DOM `Notation` interface.
///
/// # Specification
///
/// This interface represents a notation declared in the DTD. A notation either declares, by name,
/// the format of an unparsed entity (see section 4.7 of the XML 1.0 specification), or is used
/// for formal declaration of processing instruction targets (see section 2.6 of the XML 1.0
/// specification). The `nodeName` attribute inherited from [`Node`](trait.Node.html) is set to the
/// declared name of the notation.
///
/// The DOM Level 1 does not support editing `Notation` nodes; they are therefore readonly.
///
/// A `Notation` node does not have any parent.
///
pub trait Notation: Node {
    ///
    /// The public identifier of this notation.
    ///
    /// # Specification
    ///
    /// If the public identifier was not specified, this is `null`.
    ///
    fn public_id(&self) -> Option<String>;
    ///
    /// The system identifier of this notation.
    ///
    /// # Specification
    ///
    /// If the system identifier was not specified, this is `null`.
    ///
    fn system_id(&self) -> Option<String>;
}

// ------------------------------------------------------------------------------------------------

///
/// This corresponds to the DOM `ProcessingInstruction` interface.
///
/// # Specification
///
/// The `ProcessingInstruction` interface represents a "processing instruction", used in XML as a
/// way to keep processor-specific information in the text of the document.
///
pub trait ProcessingInstruction: Node {
    ///
    /// The number of 16-bit units that are available through `data`.
    ///
    fn length(&self) -> usize {
        match self.data() {
            None => 0,
            Some(s) => s.len(),
        }
    }
    ///
    /// The content of this processing instruction.
    ///
    /// # Specification
    ///
    /// This is from the first non white space character after the target to the character
    /// immediately preceding the `'?>'`.
    ///
    /// **Exceptions on setting**
    ///
    /// * `NO_MODIFICATION_ALLOWED_ERR`: Raised when the node is readonly.
    ///
    fn data(&self) -> Option<String> {
        Node::node_value(self)
    }
    ///
    /// Set the `data` for the node; see [`data`](#tymethod.data).
    ///
    fn set_data(&mut self, data: &str) -> Result<()> {
        Node::set_node_value(self, data)
    }
    ///
    /// Set the `data` for the node to `None`; see [`data`](#tymethod.data).
    ///
    fn unset_data(&mut self) -> Result<()> {
        Node::unset_node_value(self)
    }
    ///
    /// The target of this processing instruction.
    ///
    /// # Specification
    ///
    /// XML defines this as being the first token following the markup that begins the processing
    /// instruction.
    ///
    fn target(&self) -> String {
        Node::node_name(self).to_string()
    }
}

// ------------------------------------------------------------------------------------------------

///
/// This corresponds to the DOM `Text` interface.
///
/// # Specification
///
/// The `Text` interface inherits from [`CharacterData`](trait.CharacterData.html) and represents the
/// textual content (termed character data in XML) of an [`Element`](trait.Element.html) or
/// [`Attr`](trait.Attribute.html). If there is no markup inside an element's content, the text is
/// contained in a single object implementing the `Text` interface that is the only child of the
/// element. If there is markup, it is parsed into the information items (elements, comments,
/// etc.) and `Text` nodes that form the list of children of the element.
///
/// When a document is first made available via the DOM, there is only one `Text` node for each
/// block of text. Users may create adjacent `Text` nodes that represent the contents of a given
/// element without any intervening markup, but should be aware that there is no way to represent
/// the separations between these nodes in XML or HTML, so they will not (in general) persist
/// between DOM editing sessions. The `normalize()` method on [`Node`](trait.Node.html) merges any
/// such adjacent `Text` objects into a single node for each block of text.
///
pub trait Text: CharacterData {
    ///
    /// Breaks this node into two nodes at the specified offset, keeping both in the tree as siblings.
    ///
    /// # Specification
    ///
    /// After being split, this node will contain all the content up to the offset point. A new
    /// node of the same type, which contains all the content at and after the offset point, is
    /// returned. If the original node had a parent node, the new node is inserted as the next
    /// sibling of the original node. When the offset is equal to the length of this node, the
    /// new node has no data.
    ///
    /// **Parameters**
    ///
    /// * `offset` of type `unsigned long`: The 16-bit unit offset at which to split, starting from 0.
    ///
    /// **Return Value**
    ///
    /// * `Text`: The new node, of the same type as this node.
    ///
    /// **Exceptions**
    ///
    /// * `INDEX_SIZE_ERR`: Raised if the specified offset is negative or greater than the number
    ///   of 16-bit units in data.
    /// * `NO_MODIFICATION_ALLOWED_ERR`: Raised if this node is readonly.
    ///
    fn split(&mut self, offset: usize) -> Result<Self::NodeRef>;
}

// ------------------------------------------------------------------------------------------------

///
/// This corresponds to the DOM `NodeType` set of constants.
///
#[derive(Clone, Debug, PartialEq, Eq)]
#[repr(u16)]
pub enum NodeType {
    /// The node is an [`Element`](trait.Element.html)
    Element = 1,
    /// The node is an [`Attribute`](trait.Attribute.html)
    Attribute,
    /// The node is a [`Text`](trait.Text.html)
    Text,
    /// The node is a [`CDataSection`](trait.CDataSection.html)
    CData,
    /// The node is an `EntityReference`
    EntityReference,
    /// The node is an `Entity`
    Entity,
    /// The node is a [`ProcessingInstruction`](trait.ProcessingInstruction.html)
    ProcessingInstruction,
    /// The node is a [`Comment`](trait.Comment.html)
    Comment,
    /// The node is a [`Document`](trait.Document.html)
    Document,
    /// The node is a [`DocumentType`](trait.DocumentType.html)
    DocumentType,
    /// The node is a `DocumentFragment`
    DocumentFragment,
    /// The node is a `Notation`
    Notation,
}