use crate::core::{Body, Changeset, NodeData, OperationTransform, Path};
use crate::errors::OTError;

use serde::{Deserialize, Serialize};
use std::sync::Arc;

#[derive(Debug, Clone, Serialize, Deserialize)]
#[serde(tag = "op")]
pub enum NodeOperation {
  #[serde(rename = "insert")]
  Insert { path: Path, nodes: Vec<NodeData> },

  #[serde(rename = "update")]
  Update { path: Path, changeset: Changeset },

  #[serde(rename = "delete")]
  Delete { path: Path, nodes: Vec<NodeData> },
}

impl NodeOperation {
  pub fn get_path(&self) -> &Path {
    match self {
      NodeOperation::Insert { path, .. } => path,
      NodeOperation::Delete { path, .. } => path,
      NodeOperation::Update { path, .. } => path,
    }
  }

  pub fn get_mut_path(&mut self) -> &mut Path {
    match self {
      NodeOperation::Insert { path, .. } => path,
      NodeOperation::Delete { path, .. } => path,
      NodeOperation::Update { path, .. } => path,
    }
  }

  pub fn is_update_delta(&self) -> bool {
    match self {
      NodeOperation::Insert { .. } => false,
      NodeOperation::Update { path: _, changeset } => changeset.is_delta(),
      NodeOperation::Delete { .. } => false,
    }
  }

  pub fn is_update_attribute(&self) -> bool {
    match self {
      NodeOperation::Insert { .. } => false,
      NodeOperation::Update { path: _, changeset } => changeset.is_attribute(),
      NodeOperation::Delete { .. } => false,
    }
  }
  pub fn is_insert(&self) -> bool {
    match self {
      NodeOperation::Insert { .. } => true,
      NodeOperation::Update { .. } => false,
      NodeOperation::Delete { .. } => false,
    }
  }
  pub fn can_compose(&self, other: &NodeOperation) -> bool {
    if self.get_path() != other.get_path() {
      return false;
    }
    if self.is_update_delta() && other.is_update_delta() {
      return true;
    }

    if self.is_update_attribute() && other.is_update_attribute() {
      return true;
    }

    if self.is_insert() && other.is_update_delta() {
      return true;
    }
    false
  }

  pub fn compose(&mut self, other: &NodeOperation) -> Result<(), OTError> {
    match (self, other) {
      (
        NodeOperation::Insert { path: _, nodes },
        NodeOperation::Update {
          path: _other_path,
          changeset,
        },
      ) => {
        match changeset {
          Changeset::Delta { delta, inverted: _ } => {
            if let Body::Delta(old_delta) = &mut nodes.last_mut().unwrap().body {
              let new_delta = old_delta.compose(delta)?;
              *old_delta = new_delta;
            }
          },
          Changeset::Attributes { new: _, old: _ } => {
            return Err(OTError::compose().context("Can't compose the attributes changeset"));
          },
        }
        Ok(())
      },
      (
        NodeOperation::Update { path: _, changeset },
        NodeOperation::Update {
          path: _,
          changeset: other_changeset,
        },
      ) => changeset.compose(other_changeset),
      (_left, _right) => Err(OTError::compose().context("Can't compose the operation")),
    }
  }

  pub fn inverted(&self) -> NodeOperation {
    match self {
      NodeOperation::Insert { path, nodes } => NodeOperation::Delete {
        path: path.clone(),
        nodes: nodes.clone(),
      },
      NodeOperation::Delete { path, nodes } => NodeOperation::Insert {
        path: path.clone(),
        nodes: nodes.clone(),
      },
      NodeOperation::Update {
        path,
        changeset: body,
      } => NodeOperation::Update {
        path: path.clone(),
        changeset: body.inverted(),
      },
    }
  }

  /// Make the `other` operation can be applied to the version after applying the `self` operation.
  /// The semantics of transform is used when editing conflicts occur, which is often determined by the version id。
  /// For example, if the inserted position has been acquired by others, then it's needed to do the transform to
  /// make sure the inserted position is right.
  ///
  /// # Arguments
  ///
  /// * `other`: The operation that is going to be transformed
  ///
  /// # Examples
  ///
  /// ```
  /// use lib_ot::core::{NodeDataBuilder, NodeOperation, Path};
  /// let node_1 = NodeDataBuilder::new("text_1").build();
  /// let node_2 = NodeDataBuilder::new("text_2").build();
  ///
  /// let op_1 = NodeOperation::Insert {
  ///     path: Path(vec![0, 1]),
  ///     nodes: vec![node_1],
  /// };
  ///
  /// let mut op_2 = NodeOperation::Insert {
  ///     path: Path(vec![0, 1]),
  ///     nodes: vec![node_2],
  /// };
  ///
  /// assert_eq!(serde_json::to_string(&op_2).unwrap(), r#"{"op":"insert","path":[0,1],"nodes":[{"type":"text_2"}]}"#);
  ///
  /// op_1.transform(&mut op_2);
  /// assert_eq!(serde_json::to_string(&op_2).unwrap(), r#"{"op":"insert","path":[0,2],"nodes":[{"type":"text_2"}]}"#);
  /// assert_eq!(serde_json::to_string(&op_1).unwrap(), r#"{"op":"insert","path":[0,1],"nodes":[{"type":"text_1"}]}"#);
  /// ```
  pub fn transform(&self, other: &mut NodeOperation) {
    match self {
      NodeOperation::Insert { path, nodes } => {
        let new_path = path.transform(other.get_path(), nodes.len());
        *other.get_mut_path() = new_path;
      },
      NodeOperation::Delete { path, nodes } => {
        let new_path = path.transform(other.get_path(), nodes.len());
        *other.get_mut_path() = new_path;
      },
      _ => {
        // Only insert/delete will change the path.
      },
    }
  }
}

type OperationIndexMap = Vec<Arc<NodeOperation>>;

#[derive(Debug, Clone, Default)]
pub struct NodeOperations {
  inner: OperationIndexMap,
}

impl NodeOperations {
  pub fn new() -> Self {
    Self::default()
  }

  pub fn from_operations(operations: Vec<NodeOperation>) -> Self {
    let mut ops = Self::new();
    for op in operations {
      ops.push_op(op)
    }
    ops
  }

  pub fn from_bytes(bytes: Vec<u8>) -> Result<Self, OTError> {
    let operation_list =
      serde_json::from_slice(&bytes).map_err(|err| OTError::serde().context(err))?;
    Ok(operation_list)
  }

  pub fn to_bytes(&self) -> Result<Vec<u8>, OTError> {
    let bytes = serde_json::to_vec(self).map_err(|err| OTError::serde().context(err))?;
    Ok(bytes)
  }

  pub fn values(&self) -> &Vec<Arc<NodeOperation>> {
    &self.inner
  }

  pub fn values_mut(&mut self) -> &mut Vec<Arc<NodeOperation>> {
    &mut self.inner
  }

  pub fn len(&self) -> usize {
    self.values().len()
  }

  pub fn is_empty(&self) -> bool {
    self.inner.is_empty()
  }

  pub fn into_inner(self) -> Vec<Arc<NodeOperation>> {
    self.inner
  }

  pub fn push_op<T: Into<Arc<NodeOperation>>>(&mut self, other: T) {
    let other = other.into();
    if let Some(last_operation) = self.inner.last_mut() {
      if last_operation.can_compose(&other) {
        let mut_operation = Arc::make_mut(last_operation);
        if mut_operation.compose(&other).is_ok() {
          return;
        }
      }
    }

    // If the passed-in operation can't be composed, then append it to the end.
    self.inner.push(other);
  }

  pub fn compose(&mut self, other: NodeOperations) {
    for operation in other.values() {
      self.push_op(operation.clone());
    }
  }

  pub fn inverted(&self) -> Self {
    let mut operations = Self::new();
    for operation in self.values() {
      operations.push_op(operation.inverted());
    }
    operations
  }
}

impl std::convert::From<Vec<NodeOperation>> for NodeOperations {
  fn from(operations: Vec<NodeOperation>) -> Self {
    Self::from_operations(operations)
  }
}

impl std::convert::From<NodeOperation> for NodeOperations {
  fn from(operation: NodeOperation) -> Self {
    Self::from_operations(vec![operation])
  }
}