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use super::*;
#[derive(Debug)]
struct ReplacementContext<'a> {
index: &'a mut usize,
index_shift: &'a mut usize,
to_delete: &'a mut FxHashMap<ContainerID, usize>,
container_remap: &'a mut FxHashMap<ContainerID, ContainerID>,
deleted_indices: &'a mut Vec<usize>,
next_deleted: &'a mut BinaryHeap<Reverse<usize>>,
}
impl MovableListHandler {
/// Applies a delta to the movable list handler.
///
/// This function processes the given delta, performing the necessary insertions,
/// deletions, and moves to update the list accordingly. It handles container elements,
/// maintains a map for remapping container IDs, and ensures proper indexing throughout
/// the operation.
///
/// # Arguments
///
/// * `delta` - A delta representing the changes to apply.
/// * `container_remap` - A map used to remap container IDs during the operation.
///
/// # Returns
///
/// * `LoroResult<()>` - Returns `Ok(())` if successful, or an error if something goes wrong.
#[tracing::instrument(level = "debug", skip_all)]
pub fn apply_delta(
&self,
delta: loro_delta::DeltaRope<
loro_delta::array_vec::ArrayVec<ValueOrHandler, 8>,
crate::event::ListDeltaMeta,
>,
container_remap: &mut FxHashMap<ContainerID, ContainerID>,
) -> LoroResult<()> {
{
// Test whether the delta is valid
let len = self.len();
let mut index = 0;
for delta_item in delta.iter() {
match delta_item {
loro_delta::DeltaItem::Retain { len, .. } => {
index += *len;
}
loro_delta::DeltaItem::Replace { delete, .. } => {
index += *delete;
}
}
if index > len {
return Err(LoroError::OutOfBound {
pos: index,
len,
info: "apply_delta".into(),
});
}
}
}
match &self.inner {
MaybeDetached::Detached(_) => {
unimplemented!();
}
MaybeDetached::Attached(_) => {
// use tracing::debug;
// debug!(
// "Movable list value before apply_delta: {:#?}",
// self.get_deep_value_with_id()
// );
// debug!("Applying delta: {:#?}", &delta);
// Preprocess deletions to build a map of containers to delete.
let mut to_delete = self.preprocess_deletions(&delta);
// Process insertions and moves.
let mut index = 0;
let mut index_shift = 0;
let mut deleted_indices = Vec::new();
let mut next_deleted = BinaryHeap::new();
// - positive values are retain
// - negative values are deletions
let mut delta_change: Vec<isize> = Vec::new();
for delta_item in delta.iter() {
match delta_item {
loro_delta::DeltaItem::Retain { len, .. } => {
index += len;
delta_change.push(*len as isize);
}
loro_delta::DeltaItem::Replace {
value,
delete,
attr,
} => {
// Handle deletions in the current replace operation.
let old_index = index;
self.handle_deletions_in_replace(
*delete,
&mut index,
index_shift,
&mut next_deleted,
);
delta_change.push(-((index - old_index) as isize));
// Process the insertions and moves.
let mut context = ReplacementContext {
index: &mut index,
index_shift: &mut index_shift,
to_delete: &mut to_delete,
container_remap,
deleted_indices: &mut deleted_indices,
next_deleted: &mut next_deleted,
};
self.process_replacements(value, attr, &mut context)
.unwrap();
delta_change.push(value.len() as isize);
}
}
}
// Apply any remaining deletions.
self.apply_remaining_deletions(delta_change, &mut deleted_indices)?;
Ok(())
}
}
}
/// Preprocess deletions to build a map of containers to delete.
///
/// # Arguments
///
/// * `delta` - The delta containing the deletions.
///
/// # Returns
///
/// * `FxHashMap<ContainerID, usize>` - A map of containers to their indices that need to be deleted.
fn preprocess_deletions(
&self,
delta: &loro_delta::DeltaRope<
loro_delta::array_vec::ArrayVec<ValueOrHandler, 8>,
crate::event::ListDeltaMeta,
>,
) -> FxHashMap<ContainerID, usize> {
let mut index = 0;
let mut to_delete = FxHashMap::default();
for delta_item in delta.iter() {
match delta_item {
loro_delta::DeltaItem::Retain { len, .. } => {
index += len;
}
loro_delta::DeltaItem::Replace { delete, .. } => {
if *delete > 0 {
for i in index..index + *delete {
if let Some(LoroValue::Container(c)) = self.get(i) {
to_delete.insert(c, i);
}
}
index += *delete;
}
}
}
}
to_delete
}
/// Handles deletions' effect on the index within a replace operation.
/// It will not perform the deletions.
///
/// # Arguments
///
/// * `delete_len` - The number of deletions.
/// * `index` - The current index in the list.
/// * `index_shift` - The current index shift due to previous operations.
/// * `next_deleted` - A heap of indices scheduled for deletion.
fn handle_deletions_in_replace(
&self,
delete_len: usize,
index: &mut usize,
index_shift: usize,
next_deleted: &mut BinaryHeap<Reverse<usize>>,
) {
if delete_len > 0 {
let mut remaining_deletes = delete_len;
while let Some(Reverse(old_index)) = next_deleted.peek() {
if *old_index + index_shift < *index + remaining_deletes {
assert!(*index <= *old_index + index_shift);
assert!(remaining_deletes > 0);
next_deleted.pop();
remaining_deletes -= 1;
} else {
break;
}
}
// Increase the index by the number of deletions handled.
*index += remaining_deletes;
}
}
/// Processes replacements, handling insertions and moves.
///
/// # Arguments
///
/// * `values` - The values to insert or move.
/// * `attr` - Additional attributes for the delta item.
/// * `context` - A context struct containing related parameters.
fn process_replacements(
&self,
values: &loro_delta::array_vec::ArrayVec<ValueOrHandler, 8>,
attr: &crate::event::ListDeltaMeta,
context: &mut ReplacementContext,
) -> LoroResult<()> {
for v in values.iter() {
match v {
ValueOrHandler::Value(LoroValue::Container(old_id)) => {
self.apply_insertion(attr, context, old_id.clone())?;
}
ValueOrHandler::Handler(handler) => {
let old_id = handler.id();
self.apply_insertion(attr, context, old_id)?;
}
ValueOrHandler::Value(value) => {
self.insert(*context.index, value.clone())?;
Self::update_positions_on_insert(context.to_delete, *context.index, 1);
*context.index += 1;
*context.index_shift += 1;
}
}
}
Ok(())
}
fn apply_insertion(
&self,
attr: &crate::event::ListDeltaMeta,
context: &mut ReplacementContext<'_>,
mut old_id: ContainerID,
) -> Result<(), LoroError> {
if !context.to_delete.contains_key(&old_id) {
while let Some(new_id) = context.container_remap.get(&old_id) {
old_id = new_id.clone();
if context.to_delete.contains_key(&old_id) {
break;
}
}
}
if let Some(old_index) = context.to_delete.remove(&old_id) {
if old_index > *context.index {
ensure_cov::notify_cov(
"loro_internal::handler::movable_list_apply_delta::process_replacements::mov_0",
);
self.mov(old_index, *context.index)?;
context.next_deleted.push(Reverse(old_index));
*context.index += 1;
*context.index_shift += 1;
} else {
ensure_cov::notify_cov(
"loro_internal::handler::movable_list_apply_delta::process_replacements::mov_1",
);
self.mov(old_index, *context.index - 1)?;
}
context.deleted_indices.push(old_index);
Self::update_positions_on_delete(context.to_delete, old_index);
Self::update_positions_on_insert(context.to_delete, *context.index, 1);
} else if !attr.from_move || !self.contains_container(&old_id) {
// Insert a new container if not moved.
let new_handler = self.insert_container(
*context.index,
Handler::new_unattached(old_id.container_type()),
)?;
let new_id = new_handler.id();
context.container_remap.insert(old_id, new_id);
Self::update_positions_on_insert(context.to_delete, *context.index, 1);
*context.index += 1;
*context.index_shift += 1;
}
Ok(())
}
fn contains_container(&self, id: &ContainerID) -> bool {
(0..self.len()).any(|index| {
matches!(
self.get(index),
Some(LoroValue::Container(container_id)) if container_id == *id
)
})
}
/// Applies any remaining deletions after processing insertions and moves.
///
/// # Arguments
///
/// * `delta` - The delta containing the deletions.
/// * `deleted_indices` - A list of indices that have been deleted.
fn apply_remaining_deletions(
&self,
delta: Vec<isize>,
deleted_indices: &mut Vec<usize>,
) -> LoroResult<()> {
// Sort deleted indices from largest to smallest.
deleted_indices.sort_by_key(|&x| std::cmp::Reverse(x));
let mut index: usize = 0;
for delta_item in delta.iter() {
match *delta_item {
x if x > 0 => {
index += x as usize;
}
neg_delete => {
let delete = neg_delete.unsigned_abs();
let mut remaining_deletes = delete;
while let Some(&last) = deleted_indices.last() {
if last < index {
deleted_indices.pop();
continue;
}
if last < index + remaining_deletes {
deleted_indices.pop();
remaining_deletes -= 1;
} else {
break;
}
}
self.delete(index, remaining_deletes)?;
}
}
}
Ok(())
}
/// Updates positions in the map after an insertion.
///
/// Increments positions that are greater than or equal to the insertion index.
///
/// # Arguments
///
/// * `positions` - The map of positions to update.
/// * `index` - The index where the insertion occurred.
/// * `len` - The length of the insertion.
fn update_positions_on_insert(
positions: &mut FxHashMap<ContainerID, usize>,
index: usize,
len: usize,
) {
for pos in positions.values_mut() {
if *pos >= index {
*pos += len;
}
}
}
/// Updates positions in the map after a deletion.
///
/// Decrements positions that are greater than or equal to the deletion index.
///
/// # Arguments
///
/// * `positions` - The map of positions to update.
/// * `index` - The index where the deletion occurred.
fn update_positions_on_delete(positions: &mut FxHashMap<ContainerID, usize>, index: usize) {
for pos in positions.values_mut() {
if *pos >= index {
*pos -= 1;
}
}
}
}