use anymap::AnyMap;
use fxhash::{FxHashMap, FxHashSet};
use std::{
    any::TypeId,
    collections::VecDeque,
    ops::{Index, IndexMut},
};

use dioxus_core::{ElementId, Mutations, VNode, VirtualDom};

use crate::state::{union_ordered_iter, AttributeMask, NodeMask, State};

/// A Dom that can sync with the VirtualDom mutations intended for use in lazy renderers.
/// The render state passes from parent to children and or accumulates state from children to parents.
/// To get started implement [PushedDownState] and or [BubbledUpState] and call [RealDom::apply_mutations] to update the dom and [RealDom::update_state] to update the state of the nodes.
#[derive(Debug)]
pub struct RealDom<S: State> {
    root: usize,
    nodes: Vec<Option<Node<S>>>,
    nodes_listening: FxHashMap<&'static str, FxHashSet<usize>>,
    node_stack: smallvec::SmallVec<[usize; 10]>,
}

impl<S: State> Default for RealDom<S> {
    fn default() -> Self {
        Self::new()
    }
}

impl<S: State> RealDom<S> {
    pub fn new() -> RealDom<S> {
        RealDom {
            root: 0,
            nodes: {
                let v = vec![Some(Node::new(
                    0,
                    NodeType::Element {
                        tag: "Root".to_string(),
                        namespace: Some("Root"),
                        children: Vec::new(),
                    },
                ))];
                v
            },
            nodes_listening: FxHashMap::default(),
            node_stack: smallvec::SmallVec::new(),
        }
    }

    /// Updates the dom, up and down state and return a set of nodes that were updated pass this to update_state.
    pub fn apply_mutations(&mut self, mutations_vec: Vec<Mutations>) -> Vec<(usize, NodeMask)> {
        let mut nodes_updated = Vec::new();
        for mutations in mutations_vec {
            for e in mutations.edits {
                use dioxus_core::DomEdit::*;
                match e {
                    PushRoot { root } => self.node_stack.push(root as usize),
                    AppendChildren { many } => {
                        let target = if self.node_stack.len() > many as usize {
                            *self
                                .node_stack
                                .get(self.node_stack.len() - (many as usize + 1))
                                .unwrap()
                        } else {
                            0
                        };
                        let drained: Vec<_> = self
                            .node_stack
                            .drain(self.node_stack.len() - many as usize..)
                            .collect();
                        for ns in drained {
                            self.link_child(ns, target).unwrap();
                            nodes_updated.push((ns, NodeMask::ALL));
                        }
                    }
                    ReplaceWith { root, m } => {
                        let root = self.remove(root as usize).unwrap();
                        let target = root.parent.unwrap().0;
                        let drained: Vec<_> = self.node_stack.drain(0..m as usize).collect();
                        for ns in drained {
                            nodes_updated.push((ns, NodeMask::ALL));
                            self.link_child(ns, target).unwrap();
                        }
                    }
                    InsertAfter { root, n } => {
                        let target = self[root as usize].parent.unwrap().0;
                        let drained: Vec<_> = self.node_stack.drain(0..n as usize).collect();
                        for ns in drained {
                            nodes_updated.push((ns, NodeMask::ALL));
                            self.link_child(ns, target).unwrap();
                        }
                    }
                    InsertBefore { root, n } => {
                        let target = self[root as usize].parent.unwrap().0;
                        let drained: Vec<_> = self.node_stack.drain(0..n as usize).collect();
                        for ns in drained {
                            nodes_updated.push((ns, NodeMask::ALL));
                            self.link_child(ns, target).unwrap();
                        }
                    }
                    Remove { root } => {
                        if let Some(parent) = self[root as usize].parent {
                            nodes_updated.push((parent.0, NodeMask::NONE));
                        }
                        self.remove(root as usize).unwrap();
                    }
                    CreateTextNode { root, text } => {
                        let n = Node::new(
                            root,
                            NodeType::Text {
                                text: text.to_string(),
                            },
                        );
                        self.insert(n);
                        self.node_stack.push(root as usize)
                    }
                    CreateElement { root, tag } => {
                        let n = Node::new(
                            root,
                            NodeType::Element {
                                tag: tag.to_string(),
                                namespace: None,
                                children: Vec::new(),
                            },
                        );
                        self.insert(n);
                        self.node_stack.push(root as usize)
                    }
                    CreateElementNs { root, tag, ns } => {
                        let n = Node::new(
                            root,
                            NodeType::Element {
                                tag: tag.to_string(),
                                namespace: Some(ns),
                                children: Vec::new(),
                            },
                        );
                        self.insert(n);
                        self.node_stack.push(root as usize)
                    }
                    CreatePlaceholder { root } => {
                        let n = Node::new(root, NodeType::Placeholder);
                        self.insert(n);
                        self.node_stack.push(root as usize)
                    }

                    NewEventListener {
                        event_name,
                        scope: _,
                        root,
                    } => {
                        if let Some(v) = self.nodes_listening.get_mut(event_name) {
                            v.insert(root as usize);
                        } else {
                            let mut hs = FxHashSet::default();
                            hs.insert(root as usize);
                            self.nodes_listening.insert(event_name, hs);
                        }
                    }
                    RemoveEventListener { root, event } => {
                        let v = self.nodes_listening.get_mut(event).unwrap();
                        v.remove(&(root as usize));
                    }
                    SetText {
                        root,
                        text: new_text,
                    } => {
                        let target = &mut self[root as usize];
                        nodes_updated.push((
                            root as usize,
                            NodeMask::new(AttributeMask::NONE, false, false, true),
                        ));
                        match &mut target.node_type {
                            NodeType::Text { text } => {
                                *text = new_text.to_string();
                            }
                            _ => unreachable!(),
                        }
                    }
                    SetAttribute { root, field, .. } => {
                        nodes_updated.push((
                            root as usize,
                            NodeMask::new(AttributeMask::single(field), false, false, false),
                        ));
                    }
                    RemoveAttribute {
                        root, name: field, ..
                    } => {
                        nodes_updated.push((
                            root as usize,
                            NodeMask::new(AttributeMask::single(field), false, false, false),
                        ));
                    }
                    PopRoot {} => {
                        self.node_stack.pop();
                    }
                }
            }
        }

        nodes_updated
    }

    /// Seperated from apply_mutations because Mutations require a mutable reference to the VirtualDom.
    pub fn update_state(
        &mut self,
        vdom: &VirtualDom,
        nodes_updated: Vec<(usize, NodeMask)>,
        ctx: AnyMap,
    ) -> Option<FxHashSet<usize>> {
        #[derive(PartialEq, Clone, Debug)]
        enum StatesToCheck {
            All,
            Some(Vec<TypeId>),
        }
        impl StatesToCheck {
            fn union(&self, other: &Self) -> Self {
                match (self, other) {
                    (Self::Some(s), Self::Some(o)) => Self::Some(union_ordered_iter(
                        s.iter().copied(),
                        o.iter().copied(),
                        s.len() + o.len(),
                    )),
                    _ => Self::All,
                }
            }
        }

        #[derive(Debug, Clone)]
        struct NodeRef {
            id: usize,
            height: u16,
            node_mask: NodeMask,
            to_check: StatesToCheck,
        }
        impl NodeRef {
            fn union_with(&mut self, other: &Self) {
                self.node_mask = self.node_mask.union(&other.node_mask);
                self.to_check = self.to_check.union(&other.to_check);
            }
        }
        impl Eq for NodeRef {}
        impl PartialEq for NodeRef {
            fn eq(&self, other: &Self) -> bool {
                self.id == other.id && self.height == other.height
            }
        }
        impl Ord for NodeRef {
            fn cmp(&self, other: &Self) -> std::cmp::Ordering {
                self.partial_cmp(other).unwrap()
            }
        }
        impl PartialOrd for NodeRef {
            fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
                // Sort nodes first by height, then if the height is the same id.
                // The order of the id does not matter it just helps with binary search later
                Some(self.height.cmp(&other.height).then(self.id.cmp(&other.id)))
            }
        }

        let mut to_rerender = FxHashSet::default();
        to_rerender.extend(nodes_updated.iter().map(|(id, _)| id));
        let mut nodes_updated: Vec<_> = nodes_updated
            .into_iter()
            .map(|(id, mask)| NodeRef {
                id,
                height: self[id].height,
                node_mask: mask,
                to_check: StatesToCheck::All,
            })
            .collect();
        nodes_updated.sort();

        // Combine mutations that affect the same node.
        let mut last_node: Option<NodeRef> = None;
        let mut new_nodes_updated = VecDeque::new();
        for current in nodes_updated.into_iter() {
            if let Some(node) = &mut last_node {
                if *node == current {
                    node.union_with(&current);
                } else {
                    new_nodes_updated.push_back(last_node.replace(current).unwrap());
                }
            } else {
                last_node = Some(current);
            }
        }
        if let Some(node) = last_node {
            new_nodes_updated.push_back(node);
        }
        let nodes_updated = new_nodes_updated;

        // update the state that only depends on nodes. The order does not matter.
        for node_ref in &nodes_updated {
            let mut changed = false;
            let node = &mut self[node_ref.id];
            let ids = match &node_ref.to_check {
                StatesToCheck::All => node.state.node_dep_types(&node_ref.node_mask),
                StatesToCheck::Some(_) => unreachable!(),
            };
            for ty in ids {
                let node = &mut self[node_ref.id];
                let vnode = node.element(vdom);
                changed |= node.state.update_node_dep_state(ty, vnode, vdom, &ctx);
            }
            if changed {
                to_rerender.insert(node_ref.id);
            }
        }

        // bubble up state. To avoid calling reduce more times than nessisary start from the bottom and go up.
        let mut to_bubble = nodes_updated.clone();
        while let Some(node_ref) = to_bubble.pop_back() {
            let NodeRef {
                id,
                height,
                node_mask,
                to_check,
            } = node_ref;
            let (node, children) = self.get_node_children_mut(id).unwrap();
            let children_state: Vec<_> = children.iter().map(|c| &c.state).collect();
            let ids = match to_check {
                StatesToCheck::All => node.state.child_dep_types(&node_mask),
                StatesToCheck::Some(ids) => ids,
            };
            let mut changed = Vec::new();
            for ty in ids {
                let vnode = node.element(vdom);
                if node
                    .state
                    .update_child_dep_state(ty, vnode, vdom, &children_state, &ctx)
                {
                    changed.push(ty);
                }
            }
            if let Some(parent_id) = node.parent {
                if !changed.is_empty() {
                    to_rerender.insert(id);
                    let i = to_bubble.partition_point(
                        |NodeRef {
                             id: other_id,
                             height: h,
                             ..
                         }| {
                            *h < height - 1 || (*h == height - 1 && *other_id < parent_id.0)
                        },
                    );
                    // make sure the parent is not already queued
                    if i < to_bubble.len() && to_bubble[i].id == parent_id.0 {
                        to_bubble[i].to_check =
                            to_bubble[i].to_check.union(&StatesToCheck::Some(changed));
                    } else {
                        to_bubble.insert(
                            i,
                            NodeRef {
                                id: parent_id.0,
                                height: height - 1,
                                node_mask: NodeMask::NONE,
                                to_check: StatesToCheck::Some(changed),
                            },
                        );
                    }
                }
            }
        }

        // push down state. To avoid calling reduce more times than nessisary start from the top and go down.
        let mut to_push = nodes_updated.clone();
        while let Some(node_ref) = to_push.pop_front() {
            let NodeRef {
                id,
                height,
                node_mask,
                to_check,
            } = node_ref;
            let node = &self[id];
            let ids = match to_check {
                StatesToCheck::All => node.state.parent_dep_types(&node_mask),
                StatesToCheck::Some(ids) => ids,
            };
            let mut changed = Vec::new();
            let (node, parent) = self.get_node_parent_mut(id).unwrap();
            for ty in ids {
                let vnode = node.element(vdom);
                let parent = parent.as_deref();
                let state = &mut node.state;
                if state.update_parent_dep_state(ty, vnode, vdom, parent.map(|n| &n.state), &ctx) {
                    changed.push(ty);
                }
            }

            to_rerender.insert(id);
            if !changed.is_empty() {
                let node = &self[id];
                if let NodeType::Element { children, .. } = &node.node_type {
                    for c in children {
                        let i = to_push.partition_point(
                            |NodeRef {
                                 id: other_id,
                                 height: h,
                                 ..
                             }| {
                                *h < height + 1 || (*h == height + 1 && *other_id < c.0)
                            },
                        );
                        if i < to_push.len() && to_push[i].id == c.0 {
                            to_push[i].to_check = to_push[i]
                                .to_check
                                .union(&StatesToCheck::Some(changed.clone()));
                        } else {
                            to_push.insert(
                                i,
                                NodeRef {
                                    id: c.0,
                                    height: height + 1,
                                    node_mask: NodeMask::NONE,
                                    to_check: StatesToCheck::Some(changed.clone()),
                                },
                            );
                        }
                    }
                }
            }
        }

        Some(to_rerender)
    }

    fn link_child(&mut self, child_id: usize, parent_id: usize) -> Option<()> {
        debug_assert_ne!(child_id, parent_id);
        let parent = &mut self[parent_id];
        parent.add_child(ElementId(child_id));
        let parent_height = parent.height + 1;
        self[child_id].set_parent(ElementId(parent_id));
        self.increase_height(child_id, parent_height);
        Some(())
    }

    fn increase_height(&mut self, id: usize, amount: u16) {
        let n = &mut self[id];
        n.height += amount;
        if let NodeType::Element { children, .. } = &n.node_type {
            for c in children.clone() {
                self.increase_height(c.0, amount);
            }
        }
    }

    // remove a node and it's children from the dom.
    fn remove(&mut self, id: usize) -> Option<Node<S>> {
        // We do not need to remove the node from the parent's children list for children.
        fn inner<S: State>(dom: &mut RealDom<S>, id: usize) -> Option<Node<S>> {
            let mut node = dom.nodes[id as usize].take()?;
            if let NodeType::Element { children, .. } = &mut node.node_type {
                for c in children {
                    inner(dom, c.0)?;
                }
            }
            Some(node)
        }
        let mut node = self.nodes[id as usize].take()?;
        if let Some(parent) = node.parent {
            let parent = &mut self[parent];
            parent.remove_child(ElementId(id));
        }
        if let NodeType::Element { children, .. } = &mut node.node_type {
            for c in children {
                inner(self, c.0)?;
            }
        }
        Some(node)
    }

    fn insert(&mut self, node: Node<S>) {
        let current_len = self.nodes.len();
        let id = node.id.0;
        if current_len - 1 < node.id.0 {
            // self.nodes.reserve(1 + id - current_len);
            self.nodes.extend((0..1 + id - current_len).map(|_| None));
        }
        self.nodes[id] = Some(node);
    }

    pub fn get(&self, id: usize) -> Option<&Node<S>> {
        self.nodes.get(id)?.as_ref()
    }

    pub fn get_mut(&mut self, id: usize) -> Option<&mut Node<S>> {
        self.nodes.get_mut(id)?.as_mut()
    }

    // this is safe because no node will have itself as a child
    pub fn get_node_children_mut<'a>(
        &'a mut self,
        id: usize,
    ) -> Option<(&'a mut Node<S>, Vec<&'a mut Node<S>>)> {
        let ptr = self.nodes.as_mut_ptr();
        unsafe {
            if id >= self.nodes.len() {
                None
            } else {
                let node = &mut *ptr.add(id);
                if let Some(node) = node.as_mut() {
                    let children = match &node.node_type {
                        NodeType::Element { children, .. } => children
                            .iter()
                            .map(|id| (&mut *ptr.add(id.0)).as_mut().unwrap())
                            .collect(),
                        _ => Vec::new(),
                    };
                    return Some((node, children));
                } else {
                    None
                }
            }
        }
    }

    // this is safe because no node will have itself as a parent
    pub fn get_node_parent_mut<'a>(
        &'a mut self,
        id: usize,
    ) -> Option<(&'a mut Node<S>, Option<&'a mut Node<S>>)> {
        let ptr = self.nodes.as_mut_ptr();
        unsafe {
            let node = &mut *ptr.add(id);
            if id >= self.nodes.len() {
                None
            } else {
                if let Some(node) = node.as_mut() {
                    let parent = node
                        .parent
                        .map(|id| (&mut *ptr.add(id.0)).as_mut().unwrap());
                    return Some((node, parent));
                } else {
                    None
                }
            }
        }
    }

    pub fn get_listening_sorted(&self, event: &'static str) -> Vec<&Node<S>> {
        if let Some(nodes) = self.nodes_listening.get(event) {
            let mut listening: Vec<_> = nodes.iter().map(|id| &self[*id]).collect();
            listening.sort_by(|n1, n2| (n1.height).cmp(&n2.height).reverse());
            listening
        } else {
            Vec::new()
        }
    }

    /// Check if the dom contains a node and its children.
    pub fn contains_node(&self, node: &VNode) -> bool {
        match node {
            VNode::Component(_) => {
                todo!()
            }
            VNode::Element(e) => {
                if let Some(id) = e.id.get() {
                    let dom_node = &self[id];
                    match &dom_node.node_type {
                        NodeType::Element {
                            tag,
                            namespace,
                            children,
                        } => {
                            tag == e.tag
                                && namespace == &e.namespace
                                && children.iter().copied().collect::<FxHashSet<_>>()
                                    == e.children
                                        .iter()
                                        .map(|c| c.mounted_id())
                                        .collect::<FxHashSet<_>>()
                                && e.children.iter().all(|c| {
                                    self.contains_node(c)
                                        && self[c.mounted_id()].parent == e.id.get()
                                })
                        }
                        _ => false,
                    }
                } else {
                    true
                }
            }
            VNode::Fragment(f) => f.children.iter().all(|c| self.contains_node(c)),
            VNode::Placeholder(_) => true,
            VNode::Text(t) => {
                if let Some(id) = t.id.get() {
                    let dom_node = &self[id];
                    match &dom_node.node_type {
                        NodeType::Text { text } => t.text == text,
                        _ => false,
                    }
                } else {
                    true
                }
            }
        }
    }

    /// Return the number of nodes in the dom.
    pub fn size(&self) -> usize {
        // The dom has a root node, ignore it.
        self.nodes.iter().filter(|n| n.is_some()).count() - 1
    }

    /// Returns the id of the root node.
    pub fn root_id(&self) -> usize {
        self.root
    }

    /// Call a function for each node in the dom, depth first.
    pub fn traverse_depth_first(&self, mut f: impl FnMut(&Node<S>)) {
        fn inner<S: State>(dom: &RealDom<S>, id: ElementId, f: &mut impl FnMut(&Node<S>)) {
            let node = &dom[id];
            f(node);
            if let NodeType::Element { children, .. } = &node.node_type {
                for c in children {
                    inner(dom, *c, f);
                }
            }
        }
        if let NodeType::Element { children, .. } = &self[self.root].node_type {
            for c in children {
                inner(self, *c, &mut f);
            }
        }
    }

    /// Call a function for each node in the dom, depth first.
    pub fn traverse_depth_first_mut(&mut self, mut f: impl FnMut(&mut Node<S>)) {
        fn inner<S: State>(dom: &mut RealDom<S>, id: ElementId, f: &mut impl FnMut(&mut Node<S>)) {
            let node = &mut dom[id];
            f(node);
            if let NodeType::Element { children, .. } = &mut node.node_type {
                for c in children.clone() {
                    inner(dom, c, f);
                }
            }
        }
        let root = self.root;
        if let NodeType::Element { children, .. } = &mut self[root].node_type {
            for c in children.clone() {
                inner(self, c, &mut f);
            }
        }
    }
}

impl<S: State> Index<usize> for RealDom<S> {
    type Output = Node<S>;

    fn index(&self, idx: usize) -> &Self::Output {
        self.get(idx).expect("Node does not exist")
    }
}

impl<S: State> Index<ElementId> for RealDom<S> {
    type Output = Node<S>;

    fn index(&self, idx: ElementId) -> &Self::Output {
        &self[idx.0]
    }
}

impl<S: State> IndexMut<usize> for RealDom<S> {
    fn index_mut(&mut self, idx: usize) -> &mut Self::Output {
        self.get_mut(idx).expect("Node does not exist")
    }
}
impl<S: State> IndexMut<ElementId> for RealDom<S> {
    fn index_mut(&mut self, idx: ElementId) -> &mut Self::Output {
        &mut self[idx.0]
    }
}

/// The node is stored client side and stores only basic data about the node. For more complete information about the node see [`domNode::element`].
#[derive(Debug, Clone)]
pub struct Node<S: State> {
    /// The id of the node this node was created from.
    pub id: ElementId,
    /// The parent id of the node.
    pub parent: Option<ElementId>,
    /// State of the node.
    pub state: S,
    /// Additional inforation specific to the node type
    pub node_type: NodeType,
    /// The number of parents before the root node. The root node has height 1.
    pub height: u16,
}

#[derive(Debug, Clone)]
pub enum NodeType {
    Text {
        text: String,
    },
    Element {
        tag: String,
        namespace: Option<&'static str>,
        children: Vec<ElementId>,
    },
    Placeholder,
}

impl<S: State> Node<S> {
    fn new(id: u64, node_type: NodeType) -> Self {
        Node {
            id: ElementId(id as usize),
            parent: None,
            node_type,
            state: S::default(),
            height: 0,
        }
    }

    /// Returns a reference to the element that this node refrences.
    pub fn element<'b>(&self, vdom: &'b VirtualDom) -> &'b VNode<'b> {
        vdom.get_element(self.id).unwrap()
    }

    fn add_child(&mut self, child: ElementId) {
        if let NodeType::Element { children, .. } = &mut self.node_type {
            children.push(child);
        }
    }

    fn remove_child(&mut self, child: ElementId) {
        if let NodeType::Element { children, .. } = &mut self.node_type {
            children.retain(|c| c != &child);
        }
    }

    fn set_parent(&mut self, parent: ElementId) {
        self.parent = Some(parent);
    }
}