//! Dioxus WebSys
//!
//! This crate implements a renderer of the Dioxus Virtual DOM for the web browser.
//!
//! While it is possible to render a single component directly, it is not possible to render component trees. For these,
//! an external renderer is needed to progress the component lifecycles. The `WebsysRenderer` shows how to use the Virtual DOM
//! API to progress these lifecycle events to generate a fully-mounted Virtual DOM instance which can be renderer in the
//! `render` method.
//!
//! ```ignore
//! fn main() {
//!     let renderer = WebsysRenderer::<()>::new(|_| html! {<div> "Hello world" </div>});
//!     let output = renderer.render();
//!     assert_eq!(output, "<div>Hello World</div>");
//! }
//! ```
//!
//! The `WebsysRenderer` is particularly useful when needing to cache a Virtual DOM in between requests

use dioxus::{patch::Patch, prelude::VText};
pub use dioxus_core as dioxus;
use dioxus_core::{
    events::EventTrigger,
    prelude::{bumpalo::Bump, html, DiffMachine, Properties, VNode, VirtualDom, FC},
};
use futures::{channel::mpsc, future, SinkExt, StreamExt};
use mpsc::UnboundedSender;
pub mod interpreter;
/// The `WebsysRenderer` provides a way of rendering a Dioxus Virtual DOM to the browser's DOM.
/// Under the hood, we leverage WebSys and interact directly with the DOM

///
pub struct WebsysRenderer {
    internal_dom: VirtualDom,
}

impl WebsysRenderer {
    /// Create a new instance of the Dioxus Virtual Dom with no properties for the root component.
    ///
    /// This means that the root component must either consumes its own context, or statics are used to generate the page.
    /// The root component can access things like routing in its context.
    pub fn new(root: FC<()>) -> Self {
        Self::new_with_props(root, ())
    }
    /// Create a new text-renderer instance from a functional component root.
    /// Automatically progresses the creation of the VNode tree to completion.
    ///
    /// A VDom is automatically created. If you want more granular control of the VDom, use `from_vdom`
    pub fn new_with_props<T: Properties + 'static>(root: FC<T>, root_props: T) -> Self {
        Self::from_vdom(VirtualDom::new_with_props(root, root_props))
    }

    /// Create a new text renderer from an existing Virtual DOM.
    /// This will progress the existing VDom's events to completion.
    pub fn from_vdom(dom: VirtualDom) -> Self {
        Self { internal_dom: dom }
    }

    /// Run the renderer, progressing any events that crop up
    /// Yield on event handlers
    /// If the dom errors out, self is consumed and the dom is torn down
    pub async fn run(self) -> dioxus_core::error::Result<()> {
        let WebsysRenderer { mut internal_dom } = self;

        // Progress the mount of the root component
        internal_dom
            .progress()
            .expect("Progressing the root failed :(");

        // set up the channels to connect listeners to the event loop
        let (sender, mut receiver) = mpsc::unbounded::<EventTrigger>();

        // Iterate through the nodes, attaching the closure and sender to the listener
        {
            let mut remote_sender = sender.clone();
            let listener = move || {
                let event = EventTrigger::new();
                wasm_bindgen_futures::spawn_local(async move {
                    remote_sender
                        .send(event)
                        .await
                        .expect("Updating receiver failed");
                })
            };
        }

        // Event loop waits for the receiver to finish up
        // TODO! Connect the sender to the virtual dom's suspense system
        // Suspense is basically an external event that can force renders to specific nodes
        while let Some(event) = receiver.next().await {
            // event is triggered
            // relevant listeners are ran
            // internal state is modified, components are tagged for changes

            match internal_dom.progress_with_event(event).await {
                Err(_) => {}
                Ok(_) => {} // Ok(_) => render_diffs(),
            }
            // waiting for next event to arrive from the external triggers
        }

        Ok(())
    }

    fn simple_render(tree: impl for<'a> Fn(&'a Bump) -> VNode<'a>) {
        let bump = Bump::new();

        let old = html! { <div> </div> }(&bump);
        let new = tree(&bump);

        let mut machine = DiffMachine::new();

        let patches = machine.diff(&old, &new);
    }
}

use std::collections::HashMap;
use std::collections::HashSet;
use std::{cmp::min, rc::Rc};
use wasm_bindgen::JsCast;
use wasm_bindgen::JsValue;
use web_sys::{Element, Node, Text};

/// Apply all of the patches to our old root node in order to create the new root node
/// that we desire.
/// This is usually used after diffing two virtual nodes.
pub fn patch<N: Into<Node>>(root_node: N, patches: &Vec<Patch>) -> Result<(), JsValue> {
    // pub fn patch<N: Into<Node>>(root_node: N, patches: &Vec<Patch>) -> Result<ActiveClosures, JsValue> {
    let root_node: Node = root_node.into();

    let mut cur_node_idx = 0;

    let mut nodes_to_find = HashSet::new();

    for patch in patches {
        nodes_to_find.insert(patch.node_idx());
    }

    let mut element_nodes_to_patch = HashMap::new();
    let mut text_nodes_to_patch = HashMap::new();

    // Closures that were added to the DOM during this patch operation.
    // let mut active_closures = HashMap::new();

    find_nodes(
        root_node,
        &mut cur_node_idx,
        &mut nodes_to_find,
        &mut element_nodes_to_patch,
        &mut text_nodes_to_patch,
    );

    for patch in patches {
        let patch_node_idx = patch.node_idx();

        if let Some(element) = element_nodes_to_patch.get(&patch_node_idx) {
            let new_closures = apply_element_patch(&element, &patch)?;
            // active_closures.extend(new_closures);
            continue;
        }

        if let Some(text_node) = text_nodes_to_patch.get(&patch_node_idx) {
            apply_text_patch(&text_node, &patch)?;
            continue;
        }

        unreachable!("Getting here means we didn't find the element or next node that we were supposed to patch.")
    }

    // Ok(active_closures)
    Ok(())
}

fn find_nodes(
    root_node: Node,
    cur_node_idx: &mut usize,
    nodes_to_find: &mut HashSet<usize>,
    element_nodes_to_patch: &mut HashMap<usize, Element>,
    text_nodes_to_patch: &mut HashMap<usize, Text>,
) {
    if nodes_to_find.len() == 0 {
        return;
    }

    // We use child_nodes() instead of children() because children() ignores text nodes
    let children = root_node.child_nodes();
    let child_node_count = children.length();

    // If the root node matches, mark it for patching
    if nodes_to_find.get(&cur_node_idx).is_some() {
        match root_node.node_type() {
            Node::ELEMENT_NODE => {
                element_nodes_to_patch.insert(*cur_node_idx, root_node.unchecked_into());
            }
            Node::TEXT_NODE => {
                text_nodes_to_patch.insert(*cur_node_idx, root_node.unchecked_into());
            }
            other => unimplemented!("Unsupported root node type: {}", other),
        }
        nodes_to_find.remove(&cur_node_idx);
    }

    *cur_node_idx += 1;

    for i in 0..child_node_count {
        let node = children.item(i).unwrap();

        match node.node_type() {
            Node::ELEMENT_NODE => {
                find_nodes(
                    node,
                    cur_node_idx,
                    nodes_to_find,
                    element_nodes_to_patch,
                    text_nodes_to_patch,
                );
            }
            Node::TEXT_NODE => {
                if nodes_to_find.get(&cur_node_idx).is_some() {
                    text_nodes_to_patch.insert(*cur_node_idx, node.unchecked_into());
                }

                *cur_node_idx += 1;
            }
            Node::COMMENT_NODE => {
                // At this time we do not support user entered comment nodes, so if we see a comment
                // then it was a delimiter created by virtual-dom-rs in order to ensure that two
                // neighboring text nodes did not get merged into one by the browser. So we skip
                // over this virtual-dom-rs generated comment node.
            }
            _other => {
                // Ignoring unsupported child node type
                // TODO: What do we do with this situation? Log a warning?
            }
        }
    }
}

// pub type ActiveClosures = HashMap<u32, Vec<DynClosure>>;

// fn apply_element_patch(node: &Element, patch: &Patch) -> Result<ActiveClosures, JsValue> {
fn apply_element_patch(node: &Element, patch: &Patch) -> Result<(), JsValue> {
    // let active_closures = HashMap::new();

    match patch {
        Patch::AddAttributes(_node_idx, attributes) => {
            for (attrib_name, attrib_val) in attributes.iter() {
                node.set_attribute(attrib_name, attrib_val)?;
            }

            // Ok(active_closures)
            Ok(())
        }
        Patch::RemoveAttributes(_node_idx, attributes) => {
            for attrib_name in attributes.iter() {
                node.remove_attribute(attrib_name)?;
            }

            // Ok(active_closures)
            Ok(())
        }
        Patch::Replace(_node_idx, new_node) => {
            let created_node = create_dom_node(&new_node);

            node.replace_with_with_node_1(&created_node.node)?;

            Ok(())
            // Ok(created_node.closures)
        }
        Patch::TruncateChildren(_node_idx, num_children_remaining) => {
            let children = node.child_nodes();
            let mut child_count = children.length();

            // We skip over any separators that we placed between two text nodes
            //   -> `<!--ptns-->`
            //  and trim all children that come after our new desired `num_children_remaining`
            let mut non_separator_children_found = 0;

            for index in 0 as u32..child_count {
                let child = children
                    .get(min(index, child_count - 1))
                    .expect("Potential child to truncate");

                // If this is a comment node then we know that it is a `<!--ptns-->`
                // text node separator that was created in virtual_node/mod.rs.
                if child.node_type() == Node::COMMENT_NODE {
                    continue;
                }

                non_separator_children_found += 1;

                if non_separator_children_found <= *num_children_remaining as u32 {
                    continue;
                }

                node.remove_child(&child).expect("Truncated children");
                child_count -= 1;
            }

            Ok(())
            // Ok(active_closures)
        }
        Patch::AppendChildren(_node_idx, new_nodes) => {
            let parent = &node;

            let mut active_closures = HashMap::new();

            for new_node in new_nodes {
                let created_node = create_dom_node(&new_node);
                // let created_node = new_node.create_dom_node();

                parent.append_child(&created_node.node)?;

                active_closures.extend(created_node.closures);
            }

            Ok(())
            // Ok(active_closures)
        }
        Patch::ChangeText(_node_idx, _new_node) => {
            unreachable!("Elements should not receive ChangeText patches.")
        }
    }
}

fn apply_text_patch(node: &Text, patch: &Patch) -> Result<(), JsValue> {
    match patch {
        Patch::ChangeText(_node_idx, new_node) => {
            node.set_node_value(Some(&new_node.text));
        }
        Patch::Replace(_node_idx, new_node) => {
            node.replace_with_with_node_1(&create_dom_node(&new_node).node)?;
            // node.replace_with_with_node_1(&new_node.create_dom_node().node)?;
        }
        other => unreachable!(
            "Text nodes should only receive ChangeText or Replace patches, not ",
            // other,
            // "Text nodes should only receive ChangeText or Replace patches, not {:?}.",
            // other,
        ),
    };

    Ok(())
}

/// A node along with all of the closures that were created for that
/// node's events and all of it's child node's events.
pub struct CreatedNode<T> {
    /// A `Node` or `Element` that was created from a `VirtualNode`
    pub node: T,
    /// A map of a node's unique identifier along with all of the Closures for that node.
    ///
    /// The DomUpdater uses this to look up nodes and see if they're still in the page. If not
    /// the reference that we maintain to their closure will be dropped, thus freeing the Closure's
    /// memory.
    pub closures: HashMap<u32, Vec<DynClosure>>,
}

/// Box<dyn AsRef<JsValue>>> is our js_sys::Closure. Stored this way to allow us to store
/// any Closure regardless of the arguments.
pub type DynClosure = Rc<dyn AsRef<JsValue>>;

impl<T> CreatedNode<T> {
    pub fn without_closures<N: Into<T>>(node: N) -> Self {
        CreatedNode {
            node: node.into(),
            closures: HashMap::with_capacity(0),
        }
    }
}

impl<T> std::ops::Deref for CreatedNode<T> {
    type Target = T;
    fn deref(&self) -> &Self::Target {
        &self.node
    }
}

impl From<CreatedNode<Element>> for CreatedNode<Node> {
    fn from(other: CreatedNode<Element>) -> CreatedNode<Node> {
        CreatedNode {
            node: other.node.into(),
            closures: other.closures,
        }
    }
}
fn create_dom_node(node: &VNode<'_>) -> CreatedNode<Node> {
    match node {
        VNode::Text(text_node) => CreatedNode::without_closures(create_text_node(text_node)),
        VNode::Element(element_node) => create_element_node(element_node).into(),
        // VNode::Element(element_node) => element_node.create_element_node().into(),
        VNode::Suspended => todo!(" not iimplemented yet"),
        VNode::Component(_) => todo!(" not iimplemented yet"),
    }
}

/// Build a DOM element by recursively creating DOM nodes for this element and it's
/// children, it's children's children, etc.
pub fn create_element_node(node: &dioxus_core::nodes::VElement) -> CreatedNode<Element> {
    let document = web_sys::window().unwrap().document().unwrap();

    // TODO: enable svg again
    // let element = if html_validation::is_svg_namespace(&node.tag_name) {
    //     document
    //         .create_element_ns(Some("http://www.w3.org/2000/svg"), &node.tag_name)
    //         .unwrap()
    // } else {
    let element = document.create_element(&node.tag_name).unwrap();
    // };

    let mut closures = HashMap::new();

    node.attributes
        .iter()
        .map(|f| (f.name, f.value))
        .for_each(|(name, value)| {
            if name == "unsafe_inner_html" {
                element.set_inner_html(value);

                return;
            }

            element
                .set_attribute(name, value)
                .expect("Set element attribute in create element");
        });

    // if node.events.0.len() > 0 {
    //     let unique_id = create_unique_identifier();

    //     element
    //         .set_attribute("data-vdom-id".into(), &unique_id.to_string())
    //         .expect("Could not set attribute on element");

    //     closures.insert(unique_id, vec![]);

    //     node.events.0.iter().for_each(|(onevent, callback)| {
    //         // onclick -> click
    //         let event = &onevent[2..];

    //         let current_elem: &EventTarget = element.dyn_ref().unwrap();

    //         current_elem
    //             .add_event_listener_with_callback(event, callback.as_ref().as_ref().unchecked_ref())
    //             .unwrap();

    //         closures
    //             .get_mut(&unique_id)
    //             .unwrap()
    //             .push(Rc::clone(callback));
    //     });
    // }

    let mut previous_node_was_text = false;

    node.children.iter().for_each(|child| {
        match child {
            VNode::Text(text_node) => {
                let current_node = element.as_ref() as &web_sys::Node;

                // We ensure that the text siblings are patched by preventing the browser from merging
                // neighboring text nodes. Originally inspired by some of React's work from 2016.
                //  -> https://reactjs.org/blog/2016/04/07/react-v15.html#major-changes
                //  -> https://github.com/facebook/react/pull/5753
                //
                // `ptns` = Percy text node separator
                if previous_node_was_text {
                    let separator = document.create_comment("ptns");
                    current_node
                        .append_child(separator.as_ref() as &web_sys::Node)
                        .unwrap();
                }

                current_node
                    .append_child(&create_text_node(&text_node))
                    .unwrap();

                previous_node_was_text = true;
            }
            VNode::Element(element_node) => {
                previous_node_was_text = false;

                let child = create_element_node(element_node);
                // let child = element_node.create_element_node();
                let child_elem: Element = child.node;

                closures.extend(child.closures);

                element.append_child(&child_elem).unwrap();
            }
            VNode::Suspended => {
                todo!("Not yet supported")
            }
            VNode::Component(_) => {
                todo!("Not yet supported")
            }
        }
    });

    // TODO: connect on mount to the event system somehow
    // if let Some(on_create_elem) = node.events.0.get("on_create_elem") {
    //     let on_create_elem: &js_sys::Function = on_create_elem.as_ref().as_ref().unchecked_ref();
    //     on_create_elem
    //         .call1(&wasm_bindgen::JsValue::NULL, &element)
    //         .unwrap();
    // }

    CreatedNode {
        node: element,
        closures,
    }
}

/// Return a `Text` element from a `VirtualNode`, typically right before adding it
/// into the DOM.
pub fn create_text_node(node: &VText) -> Text {
    let document = web_sys::window().unwrap().document().unwrap();
    document.create_text_node(&node.text)
}

// /// For any listeners in the tree, attach the sender closure.
// /// When a event is triggered, we convert it into the synthetic event type and dump it back in the Virtual Dom's queu
// fn attach_listeners(sender: &UnboundedSender<EventTrigger>, dom: &VirtualDom) {}

// fn render_diffs() {}