// Copyright 2014-2017 The html5ever Project Developers.

// Copyright Michael Howell and others.

//

// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or

// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license

// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your

// option. This file may not be copied, modified, or distributed

// except according to those terms.

#![allow(missing_docs)]

//! A simple reference-counted DOM.

//!

//! This is sufficient as a static parse tree, but don't build a

//! web browser using it. :)

//!

//! A DOM is a [tree structure] with ordered children that can be represented in an XML-like

//! format. For example, the following graph

//!

//! ```text

//! div

//!  +- "text node"

//!  +- span

//! ```

//! in HTML would be serialized as

//!

//! ```html

//! <div>text node<span></span></div>

//! ```

//!

//! See the [document object model article on wikipedia][dom wiki] for more information.

//!

//! This implementation stores the information associated with each node once, and then hands out

//! refs to children. The nodes themselves are reference-counted to avoid copying - you can create

//! a new ref and then a node will outlive the document. Nodes own their children, but only have

//! weak references to their parents.

//!

//! [tree structure]: https://en.wikipedia.org/wiki/Tree_(data_structure)

//! [dom wiki]: https://en.wikipedia.org/wiki/Document_Object_Model

use std::borrow::Cow;

use std::cell::{Cell, RefCell};

use std::collections::{HashSet, VecDeque};

use std::default::Default;

use std::fmt;

use std::io;

use std::mem;

use std::rc::{Rc, Weak};

use tendril::StrTendril;

use html5ever::interface::tree_builder;

use html5ever::interface::tree_builder::{ElementFlags, NodeOrText, QuirksMode, TreeSink};

use html5ever::serialize::TraversalScope;

use html5ever::serialize::TraversalScope::{ChildrenOnly, IncludeNode};

use html5ever::serialize::{Serialize, Serializer};

use html5ever::Attribute;

use html5ever::ExpandedName;

use html5ever::QualName;

/// The different kinds of nodes in the DOM.

#[derive(Debug)]

pub enum NodeData {

    /// The `Document` itself - the root node of a HTML document.

    Document,

    /// A `DOCTYPE` with name, public id, and system id. See

    /// [document type declaration on wikipedia][dtd wiki].

    ///

    /// [dtd wiki]: https://en.wikipedia.org/wiki/Document_type_declaration

    Doctype {

        name: StrTendril,

    },

    /// A text node.

    Text { contents: RefCell<StrTendril> },

    /// A comment.

    Comment { contents: StrTendril },

    /// An element with attributes.

    Element {

        name: QualName,

        attrs: RefCell<Vec<Attribute>>,

        /// For HTML \<template\> elements, the [template contents].

        ///

        /// [template contents]: https://html.spec.whatwg.org/multipage/#template-contents

        template_contents: RefCell<Option<Handle>>,

        /// Whether the node is a [HTML integration point].

        ///

        /// [HTML integration point]: https://html.spec.whatwg.org/multipage/#html-integration-point

        mathml_annotation_xml_integration_point: bool,

    },

    /// A Processing instruction.

    ProcessingInstruction {

        target: StrTendril,

        contents: StrTendril,

    },

}

/// A DOM node.

pub struct Node {

    /// Parent node.

    pub parent: Cell<Option<WeakHandle>>,

    /// Child nodes of this node.

    pub children: RefCell<Vec<Handle>>,

    /// Represents this node's data.

    pub data: NodeData,

}

impl Node {

    /// Create a new node from its contents

    pub fn new(data: NodeData) -> Rc<Self> {

        Rc::new(Node {

            data,

            parent: Cell::new(None),

            children: RefCell::new(Vec::new()),

        })

    }

}

impl Drop for Node {

    fn drop(&mut self) {

        let mut nodes = mem::take(&mut *self.children.borrow_mut());

        while let Some(node) = nodes.pop() {

            let children = mem::take(&mut *node.children.borrow_mut());

            nodes.extend(children.into_iter());

            if let NodeData::Element {

                ref template_contents,

                ..

            } = node.data

            {

                if let Some(template_contents) = template_contents.borrow_mut().take() {

                    nodes.push(template_contents);

                }

            }

        }

    }

}

impl fmt::Debug for Node {

    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {

        fmt.debug_struct("Node")

            .field("data", &self.data)

            .field("children", &self.children)

            .finish()

    }

}

/// Reference to a DOM node.

pub type Handle = Rc<Node>;

/// Weak reference to a DOM node, used for parent pointers.

pub type WeakHandle = Weak<Node>;

/// Append a parentless node to another nodes' children

fn append(new_parent: &Handle, child: Handle) {

    let previous_parent = child.parent.replace(Some(Rc::downgrade(new_parent)));

    // Invariant: child cannot have existing parent

    assert!(previous_parent.is_none());

    new_parent.children.borrow_mut().push(child);

}

/// If the node has a parent, get it and this node's position in its children

fn get_parent_and_index(target: &Handle) -> Option<(Handle, usize)> {

    if let Some(weak) = target.parent.take() {

        let parent = weak.upgrade().expect("dangling weak pointer");

        target.parent.set(Some(weak));

        let i = match parent

            .children

            .borrow()

            .iter()

            .enumerate()

            .find(|&(_, child)| Rc::ptr_eq(child, target))

        {

            Some((i, _)) => i,

            None => panic!("have parent but couldn't find in parent's children!"),

        };

        Some((parent, i))

    } else {

        None

    }

}

fn append_to_existing_text(prev: &Handle, text: &str) -> bool {

    match prev.data {

        NodeData::Text { ref contents } => {

            contents.borrow_mut().push_slice(text);

            true

        }

        _ => false,

    }

}

fn remove_from_parent(target: &Handle) {

    if let Some((parent, i)) = get_parent_and_index(target) {

        parent.children.borrow_mut().remove(i);

        target.parent.set(None);

    }

}

/// The DOM itself; the result of parsing.

pub struct RcDom {

    /// The `Document` itself.

    pub document: Handle,

    /// Errors that occurred during parsing.

    pub errors: RefCell<Vec<Cow<'static, str>>>,

    /// The document's quirks mode.

    pub quirks_mode: Cell<QuirksMode>,

}

impl TreeSink for RcDom {

    type Output = Self;

    fn finish(self) -> Self {

        self

    }

    type Handle = Handle;

    type ElemName<'a> = ExpandedName<'a>;

    fn parse_error(&self, msg: Cow<'static, str>) {

        self.errors.borrow_mut().push(msg);

    }

    fn get_document(&self) -> Handle {

        self.document.clone()

    }

    fn get_template_contents(&self, target: &Handle) -> Handle {

        if let NodeData::Element {

            ref template_contents,

            ..

        } = target.data

        {

            template_contents

                .borrow()

                .as_ref()

                .expect("not a template element!")

                .clone()

        } else {

            panic!("not a template element!")

        }

    }

    fn set_quirks_mode(&self, mode: QuirksMode) {

        self.quirks_mode.set(mode);

    }

    fn same_node(&self, x: &Handle, y: &Handle) -> bool {

        Rc::ptr_eq(x, y)

    }

    fn elem_name<'a>(&self, target: &'a Handle) -> ExpandedName<'a> {

        return match target.data {

            NodeData::Element { ref name, .. } => name.expanded(),

            _ => panic!("not an element!"),

        };

    }

    fn create_element(

        &self,

        name: QualName,

        attrs: Vec<Attribute>,

        flags: ElementFlags,

    ) -> Handle {

        Node::new(NodeData::Element {

            name,

            attrs: RefCell::new(attrs),

            template_contents: RefCell::new(if flags.template {

                Some(Node::new(NodeData::Document))

            } else {

                None

            }),

            mathml_annotation_xml_integration_point: flags.mathml_annotation_xml_integration_point,

        })

    }

    fn create_comment(&self, text: StrTendril) -> Handle {

        Node::new(NodeData::Comment { contents: text })

    }

    fn create_pi(&self, target: StrTendril, data: StrTendril) -> Handle {

        Node::new(NodeData::ProcessingInstruction {

            target,

            contents: data,

        })

    }

    fn append(&self, parent: &Handle, child: NodeOrText<Handle>) {

        // Append to an existing Text node if we have one.

        if let NodeOrText::AppendText(ref text) = child {

            if let Some(h) = parent.children.borrow().last() {

                if append_to_existing_text(h, text) {

                    return;

                }

            }

        }

        append(

            parent,

            match child {

                NodeOrText::AppendText(text) => Node::new(NodeData::Text {

                    contents: RefCell::new(text),

                }),

                NodeOrText::AppendNode(node) => node,

            },

        );

    }

    fn append_before_sibling(&self, sibling: &Handle, child: NodeOrText<Handle>) {

        let (parent, i) = get_parent_and_index(sibling)

            .expect("append_before_sibling called on node without parent");

        let child = match (child, i) {

            // No previous node.

            (NodeOrText::AppendText(text), 0) => Node::new(NodeData::Text {

                contents: RefCell::new(text),

            }),

            // Look for a text node before the insertion point.

            (NodeOrText::AppendText(text), i) => {

                let children = parent.children.borrow();

                let prev = &children[i - 1];

                if append_to_existing_text(prev, &text) {

                    return;

                }

                Node::new(NodeData::Text {

                    contents: RefCell::new(text),

                })

            }

            // The tree builder promises we won't have a text node after

            // the insertion point.

            // Any other kind of node.

            (NodeOrText::AppendNode(node), _) => node,

        };

        remove_from_parent(&child);

        child.parent.set(Some(Rc::downgrade(&parent)));

        parent.children.borrow_mut().insert(i, child);

    }

    fn append_based_on_parent_node(

        &self,

        element: &Self::Handle,

        prev_element: &Self::Handle,

        child: NodeOrText<Self::Handle>,

    ) {

        let parent = element.parent.take();

        let has_parent = parent.is_some();

        element.parent.set(parent);

        if has_parent {

            self.append_before_sibling(element, child);

        } else {

            self.append(prev_element, child);

        }

    }

    fn append_doctype_to_document(

        &self,

        name: StrTendril,

        _public_id: StrTendril,

        _system_id: StrTendril,

    ) {

        append(

            &self.document,

            Node::new(NodeData::Doctype {

                name,

            }),

        );

    }

    fn add_attrs_if_missing(&self, target: &Handle, attrs: Vec<Attribute>) {

        let mut existing = if let NodeData::Element { ref attrs, .. } = target.data {

            attrs.borrow_mut()

        } else {

            panic!("not an element")

        };

        let existing_names = existing

            .iter()

            .map(|e| e.name.clone())

            .collect::<HashSet<_>>();

        existing.extend(

            attrs

                .into_iter()

                .filter(|attr| !existing_names.contains(&attr.name)),

        );

    }

    fn remove_from_parent(&self, target: &Handle) {

        remove_from_parent(target);

    }

    fn reparent_children(&self, node: &Handle, new_parent: &Handle) {

        let mut children = node.children.borrow_mut();

        let mut new_children = new_parent.children.borrow_mut();

        for child in children.iter() {

            let previous_parent = child.parent.replace(Some(Rc::downgrade(new_parent)));

            assert!(Rc::ptr_eq(

                node,

                &previous_parent.unwrap().upgrade().expect("dangling weak")

            ))

        }

        new_children.extend(mem::take(&mut *children));

    }

    fn is_mathml_annotation_xml_integration_point(&self, target: &Handle) -> bool {

        if let NodeData::Element {

            mathml_annotation_xml_integration_point,

            ..

        } = target.data

        {

            mathml_annotation_xml_integration_point

        } else {

            panic!("not an element!")

        }

    }

}

impl Default for RcDom {

    fn default() -> RcDom {

        RcDom {

            document: Node::new(NodeData::Document),

            errors: vec![].into(),

            quirks_mode: tree_builder::NoQuirks.into(),

        }

    }

}

enum SerializeOp {

    Open(Handle),

    Close(QualName),

}

pub struct SerializableHandle(Handle);

impl From<Handle> for SerializableHandle {

    fn from(h: Handle) -> SerializableHandle {

        SerializableHandle(h)

    }

}

impl Serialize for SerializableHandle {

    fn serialize<S>(&self, serializer: &mut S, traversal_scope: TraversalScope) -> io::Result<()>

    where

        S: Serializer,

    {

        let mut ops = VecDeque::new();

        match traversal_scope {

            IncludeNode => ops.push_back(SerializeOp::Open(self.0.clone())),

            ChildrenOnly(_) => ops.extend(

                self.0

                    .children

                    .borrow()

                    .iter()

                    .map(|h| SerializeOp::Open(h.clone())),

            ),

        }

        while let Some(op) = ops.pop_front() {

            match op {

                SerializeOp::Open(handle) => match handle.data {

                    NodeData::Element {

                        ref name,

                        ref attrs,

                        ..

                    } => {

                        serializer.start_elem(

                            name.clone(),

                            attrs.borrow().iter().map(|at| (&at.name, &at.value[..])),

                        )?;

                        ops.reserve(1 + handle.children.borrow().len());

                        ops.push_front(SerializeOp::Close(name.clone()));

                        for child in handle.children.borrow().iter().rev() {

                            ops.push_front(SerializeOp::Open(child.clone()));

                        }

                    }

                    NodeData::Doctype { ref name, .. } => serializer.write_doctype(name)?,

                    NodeData::Text { ref contents } => serializer.write_text(&contents.borrow())?,

                    NodeData::Comment { ref contents } => serializer.write_comment(contents)?,

                    NodeData::ProcessingInstruction {

                        ref target,

                        ref contents,

                    } => serializer.write_processing_instruction(target, contents)?,

                    NodeData::Document => panic!("Can't serialize Document node itself"),

                },

                SerializeOp::Close(name) => {

                    serializer.end_elem(name)?;

                }

            }

        }

        Ok(())

    }

}