use super::NodeOperations;
use crate::core::{Changeset, Node, NodeData, NodeOperation, Path, Transaction};
use crate::errors::{OTError, OTErrorCode};
use indextree::{Arena, FollowingSiblings, NodeId};
use std::sync::Arc;

#[derive(Default, Debug, Clone)]
pub struct NodeTreeContext {}

#[derive(Debug, Clone)]
pub struct NodeTree {
    arena: Arena<Node>,
    root: NodeId,
    pub context: NodeTreeContext,
}

impl Default for NodeTree {
    fn default() -> Self {
        Self::new(NodeTreeContext::default())
    }
}

pub const PLACEHOLDER_NODE_TYPE: &str = "";

impl NodeTree {
    pub fn new(context: NodeTreeContext) -> NodeTree {
        let mut arena = Arena::new();
        let root = arena.new_node(Node::new("root"));
        NodeTree { arena, root, context }
    }

    pub fn from_node_data(node_data: NodeData, context: NodeTreeContext) -> Result<Self, OTError> {
        let mut tree = Self::new(context);
        tree.insert_nodes(&0_usize.into(), vec![node_data])?;
        Ok(tree)
    }

    pub fn from_bytes(bytes: &[u8]) -> Result<Self, OTError> {
        let tree: NodeTree = serde_json::from_slice(bytes).map_err(|e| OTError::serde().context(e))?;
        Ok(tree)
    }

    pub fn to_bytes(&self) -> Vec<u8> {
        match serde_json::to_vec(self) {
            Ok(bytes) => bytes,
            Err(e) => {
                tracing::error!("{}", e);
                vec![]
            }
        }
    }

    pub fn to_json(&self, pretty: bool) -> Result<String, OTError> {
        if pretty {
            match serde_json::to_string_pretty(self) {
                Ok(json) => Ok(json),
                Err(err) => Err(OTError::serde().context(err)),
            }
        } else {
            match serde_json::to_string(self) {
                Ok(json) => Ok(json),
                Err(err) => Err(OTError::serde().context(err)),
            }
        }
    }

    pub fn from_operations<T: Into<NodeOperations>>(operations: T, context: NodeTreeContext) -> Result<Self, OTError> {
        let operations = operations.into();
        let mut node_tree = NodeTree::new(context);
        for (_, operation) in operations.into_inner().into_iter().enumerate() {
            node_tree.apply_op(operation)?;
        }
        Ok(node_tree)
    }

    pub fn from_transaction<T: Into<Transaction>>(transaction: T, context: NodeTreeContext) -> Result<Self, OTError> {
        let transaction = transaction.into();
        let mut tree = Self::new(context);
        tree.apply_transaction(transaction)?;
        Ok(tree)
    }

    pub fn get_node(&self, node_id: NodeId) -> Option<&Node> {
        if node_id.is_removed(&self.arena) {
            return None;
        }
        Some(self.arena.get(node_id)?.get())
    }

    pub fn get_node_at_path(&self, path: &Path) -> Option<&Node> {
        let node_id = self.node_id_at_path(path)?;
        self.get_node(node_id)
    }

    pub fn get_node_data_at_path(&self, path: &Path) -> Option<NodeData> {
        let node_id = self.node_id_at_path(path)?;
        let node_data = self.get_node_data(node_id)?;
        Some(node_data)
    }

    pub fn get_node_data_at_root(&self) -> Option<NodeData> {
        self.get_node_data(self.root)
    }

    pub fn get_node_data(&self, node_id: NodeId) -> Option<NodeData> {
        let Node {
            node_type,
            body,
            attributes,
        } = self.get_node(node_id)?.clone();
        let mut node_data = NodeData::new(node_type);
        for (key, value) in attributes.into_inner() {
            node_data.attributes.insert(key, value);
        }
        node_data.body = body;

        let children = self.get_children_ids(node_id);
        for child in children.into_iter() {
            if let Some(child_node_data) = self.get_node_data(child) {
                node_data.children.push(child_node_data);
            }
        }
        Some(node_data)
    }

    pub fn root_node_id(&self) -> NodeId {
        self.root
    }

    pub fn get_children(&self, node_id: NodeId) -> Vec<&Node> {
        node_id
            .children(&self.arena)
            .flat_map(|node_id| self.get_node(node_id))
            .collect()
    }
    /// Returns a iterator used to iterate over the node ids whose parent node id is node_id
    ///
    /// * `node_id`: the children's parent node id
    ///
    pub fn get_children_ids(&self, node_id: NodeId) -> Vec<NodeId> {
        node_id.children(&self.arena).collect()
    }

    /// Serialize the node to JSON with node_id
    pub fn serialize_node(&self, node_id: NodeId, pretty_json: bool) -> Result<String, OTError> {
        let node_data = self
            .get_node_data(node_id)
            .ok_or_else(|| OTError::internal().context("Node doesn't exist exist"))?;
        if pretty_json {
            serde_json::to_string_pretty(&node_data).map_err(|err| OTError::serde().context(err))
        } else {
            serde_json::to_string(&node_data).map_err(|err| OTError::serde().context(err))
        }
    }

    ///
    /// # Examples
    ///
    /// ```
    /// use std::sync::Arc;
    /// use lib_ot::core::{NodeOperation, NodeTree, NodeData, Path};
    /// let nodes = vec![NodeData::new("text".to_string())];
    /// let root_path: Path = vec![0].into();
    /// let op = NodeOperation::Insert {path: root_path.clone(),nodes };
    ///
    /// let mut node_tree = NodeTree::default();
    /// node_tree.apply_op(Arc::new(op)).unwrap();
    /// let node_id = node_tree.node_id_at_path(&root_path).unwrap();
    /// let node_path = node_tree.path_from_node_id(node_id);
    /// debug_assert_eq!(node_path, root_path);
    /// ```
    pub fn node_id_at_path<T: Into<Path>>(&self, path: T) -> Option<NodeId> {
        let path = path.into();
        if !path.is_valid() {
            return None;
        }

        let mut node_id = self.root;
        for id in path.iter() {
            node_id = self.node_id_from_parent_at_index(node_id, *id)?;
        }

        if node_id.is_removed(&self.arena) {
            return None;
        }
        Some(node_id)
    }

    pub fn path_from_node_id(&self, node_id: NodeId) -> Path {
        let mut path = vec![];
        let mut current_node = node_id;
        // Use .skip(1) on the ancestors iterator to skip the root node.
        let ancestors = node_id.ancestors(&self.arena).skip(1);
        for parent_node in ancestors {
            let counter = self.index_of_node(parent_node, current_node);
            path.push(counter);
            current_node = parent_node;
        }
        path.reverse();
        Path(path)
    }

    fn index_of_node(&self, parent_node: NodeId, child_node: NodeId) -> usize {
        let mut counter: usize = 0;
        let iter = parent_node.children(&self.arena);
        for node in iter {
            if node == child_node {
                return counter;
            }
            counter += 1;
        }

        counter
    }

    /// Returns the note_id at the index of the tree which its id is note_id
    /// # Arguments
    ///
    /// * `node_id`: the node id of the child's parent
    /// * `index`: index of the node in parent children list
    ///
    /// returns: Option<NodeId>
    ///
    /// # Examples
    ///
    /// ```
    /// use std::sync::Arc;
    /// use lib_ot::core::{NodeOperation, NodeTree, NodeData, Path};
    /// let node_1 = NodeData::new("text".to_string());
    /// let inserted_path: Path = vec![0].into();
    ///
    /// let mut node_tree = NodeTree::default();
    /// let op = NodeOperation::Insert {path: inserted_path.clone(),nodes: vec![node_1.clone()] };
    /// node_tree.apply_op(Arc::new(op)).unwrap();
    ///
    /// let node_2 = node_tree.get_node_at_path(&inserted_path).unwrap();
    /// assert_eq!(node_2.node_type, node_1.node_type);
    /// ```
    pub fn node_id_from_parent_at_index(&self, node_id: NodeId, index: usize) -> Option<NodeId> {
        let children = node_id.children(&self.arena);
        for (counter, child) in children.enumerate() {
            if counter == index {
                return Some(child);
            }
        }

        None
    }

    ///
    /// # Arguments
    ///
    /// * `node_id`: if the node_is is None, then will use root node_id.
    ///
    /// returns number of the children of the root node
    ///
    pub fn number_of_children(&self, node_id: Option<NodeId>) -> usize {
        match node_id {
            None => self.root.children(&self.arena).count(),
            Some(node_id) => node_id.children(&self.arena).count(),
        }
    }

    pub fn following_siblings(&self, node_id: NodeId) -> FollowingSiblings<'_, Node> {
        node_id.following_siblings(&self.arena)
    }

    pub fn apply_transaction(&mut self, transaction: Transaction) -> Result<(), OTError> {
        let operations = transaction.split().0;
        for operation in operations {
            self.apply_op(operation)?;
        }

        Ok(())
    }

    pub fn apply_op<T: Into<Arc<NodeOperation>>>(&mut self, op: T) -> Result<(), OTError> {
        let op = match Arc::try_unwrap(op.into()) {
            Ok(op) => op,
            Err(op) => op.as_ref().clone(),
        };

        match op {
            NodeOperation::Insert { path, nodes } => self.insert_nodes(&path, nodes),
            NodeOperation::Update { path, changeset } => self.update(&path, changeset),
            NodeOperation::Delete { path, nodes: _ } => self.delete_node(&path),
        }
    }
    /// Inserts nodes at given path
    /// root
    ///     0 - A
    ///         0 - A1
    ///     1 - B
    ///         0 - B1
    ///         1 - B2
    ///
    /// The path of each node will be:
    /// A:      [0]
    /// A1:     [0,0]
    /// B:      [1]
    /// B1:     [1,0]
    /// B2:     [1,1]
    ///
    /// When inserting multiple nodes into the same path, each of them will be appended to the root
    /// node. For example. The path is [0] and the nodes are [A, B, C]. After inserting the nodes,
    /// the tree will be:
    /// root
    ///     0: A
    ///     1: B
    ///     2: C
    ///
    /// returns error if the path is empty
    ///
    fn insert_nodes(&mut self, path: &Path, nodes: Vec<NodeData>) -> Result<(), OTError> {
        if !path.is_valid() {
            return Err(OTErrorCode::InvalidPath.into());
        }

        let (parent_path, last_path) = path.split_at(path.0.len() - 1);
        let last_index = *last_path.first().unwrap();
        if parent_path.is_empty() {
            self.insert_nodes_at_index(self.root, last_index, nodes)
        } else {
            let parent_node = match self.node_id_at_path(parent_path) {
                None => self.create_adjacent_nodes_for_path(parent_path),
                Some(parent_node) => parent_node,
            };

            self.insert_nodes_at_index(parent_node, last_index, nodes)
        }
    }

    /// Create the adjacent nodes for the path
    ///
    /// It will create a corresponding node for each node on the path if it's not existing.
    /// If the path is not start from zero, it will create its siblings.
    ///
    /// Check out the operation_insert_test.rs for more examples.
    /// * operation_insert_node_when_its_parent_is_not_exist
    /// * operation_insert_node_when_multiple_parent_is_not_exist_test
    ///
    /// # Arguments
    ///
    /// * `path`: creates nodes for this path
    ///
    /// returns: NodeId
    ///
    fn create_adjacent_nodes_for_path<T: Into<Path>>(&mut self, path: T) -> NodeId {
        let path = path.into();
        let mut node_id = self.root;
        for id in path.iter() {
            match self.node_id_from_parent_at_index(node_id, *id) {
                None => {
                    let num_of_children = node_id.children(&self.arena).count();
                    if *id > num_of_children {
                        for _ in 0..(*id - num_of_children) {
                            let node: Node = placeholder_node().into();
                            let sibling_node = self.arena.new_node(node);
                            node_id.append(sibling_node, &mut self.arena);
                        }
                    }

                    let node: Node = placeholder_node().into();
                    let new_node_id = self.arena.new_node(node);
                    node_id.append(new_node_id, &mut self.arena);
                    node_id = new_node_id;
                }
                Some(next_node_id) => {
                    node_id = next_node_id;
                }
            }
        }
        node_id
    }

    /// Inserts nodes before the node with node_id
    ///
    fn insert_nodes_before(&mut self, node_id: &NodeId, nodes: Vec<NodeData>) {
        if node_id.is_removed(&self.arena) {
            tracing::warn!("Node:{:?} is remove before insert", node_id);
            return;
        }
        for node in nodes {
            let (node, children) = node.split();
            let new_node_id = self.arena.new_node(node);
            node_id.insert_before(new_node_id, &mut self.arena);
            self.append_nodes(&new_node_id, children);
        }
    }

    fn insert_nodes_at_index(&mut self, parent: NodeId, index: usize, nodes: Vec<NodeData>) -> Result<(), OTError> {
        if index == 0 && parent.children(&self.arena).next().is_none() {
            self.append_nodes(&parent, nodes);
            return Ok(());
        }

        // Append the node to the end of the children list if index greater or equal to the
        // length of the children.
        let num_of_children = parent.children(&self.arena).count();
        if index >= num_of_children {
            let mut num_of_nodes_to_insert = index - num_of_children;
            while num_of_nodes_to_insert > 0 {
                self.append_nodes(&parent, vec![placeholder_node()]);
                num_of_nodes_to_insert -= 1;
            }

            self.append_nodes(&parent, nodes);
            return Ok(());
        }

        let node_to_insert = self
            .node_id_from_parent_at_index(parent, index)
            .ok_or_else(|| OTError::internal().context(format!("Can't find the node at {}", index)))?;

        self.insert_nodes_before(&node_to_insert, nodes);
        Ok(())
    }

    fn append_nodes(&mut self, parent: &NodeId, nodes: Vec<NodeData>) {
        for node in nodes {
            let (node, children) = node.split();
            let new_node_id = self.arena.new_node(node);
            parent.append(new_node_id, &mut self.arena);

            self.append_nodes(&new_node_id, children);
        }
    }

    /// Removes a node and its descendants from the tree
    fn delete_node(&mut self, path: &Path) -> Result<(), OTError> {
        if !path.is_valid() {
            return Err(OTErrorCode::InvalidPath.into());
        }
        match self.node_id_at_path(path) {
            None => tracing::warn!("Can't find any node at path: {:?}", path),
            Some(node) => {
                node.remove_subtree(&mut self.arena);
            }
        }

        Ok(())
    }

    /// Update the node at path with the `changeset`
    ///
    /// Do nothing if there is no node at the path.
    ///
    /// # Arguments
    ///
    /// * `path`: references to the node that will be applied with the changeset  
    /// * `changeset`: the change that will be applied to the node  
    ///
    /// returns: Result<(), OTError>
    fn update(&mut self, path: &Path, changeset: Changeset) -> Result<(), OTError> {
        match self.mut_node_at_path(path, |node| node.apply_changeset(changeset)) {
            Ok(_) => {}
            Err(err) => tracing::error!("{}", err),
        }
        Ok(())
    }

    fn mut_node_at_path<F>(&mut self, path: &Path, f: F) -> Result<(), OTError>
    where
        F: FnOnce(&mut Node) -> Result<(), OTError>,
    {
        if !path.is_valid() {
            return Err(OTErrorCode::InvalidPath.into());
        }
        let node_id = self.node_id_at_path(path).ok_or_else(|| {
            OTError::path_not_found().context(format!("Can't find the mutated node at path: {:?}", path))
        })?;
        match self.arena.get_mut(node_id) {
            None => tracing::warn!("The path: {:?} does not contain any nodes", path),
            Some(node) => {
                let node = node.get_mut();
                f(node)?;
            }
        }
        Ok(())
    }
}

pub fn placeholder_node() -> NodeData {
    NodeData::new(PLACEHOLDER_NODE_TYPE)
}