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use std::{fmt, mem, ops};
use imbl::Vector;
use crate::vector::OneOrManyDiffs;
use super::{entry::EntryIndex, BroadcastMessage, ObservableVector, VectorDiff};
/// A transaction that allows making multiple updates to an `ObservableVector`
/// as an atomic unit.
///
/// For updates from the transaction to have affect, it has to be finalized with
/// [`.commit()`](Self::commit). If the transaction is dropped without that
/// method being called, the updates will be discarded.
pub struct ObservableVectorTransaction<'o, T: Clone> {
// The observable vector being modified, only modified on commit.
inner: &'o mut ObservableVector<T>,
// A clone of the observable's values, what the methods operate on until commit.
values: Vector<T>,
// The batched updates, to be sent to subscribers on commit.
batch: Vec<VectorDiff<T>>,
}
impl<'o, T: Clone + 'static> ObservableVectorTransaction<'o, T> {
pub(super) fn new(inner: &'o mut ObservableVector<T>) -> Self {
let values = inner.values.clone();
Self { inner, values, batch: Vec::new() }
}
/// Commit this transaction, persisting the changes and notifying
/// subscribers.
pub fn commit(mut self) {
#[cfg(feature = "tracing")]
tracing::debug!("commit");
self.inner.values = mem::take(&mut self.values);
if self.batch.is_empty() {
#[cfg(feature = "tracing")]
tracing::trace!(
target: "eyeball_im::vector::broadcast",
"Skipping broadcast of empty list of diffs"
);
} else {
let diffs = OneOrManyDiffs::Many(mem::take(&mut self.batch));
let msg = BroadcastMessage { diffs, state: self.inner.values.clone() };
let _num_receivers = self.inner.sender.send(msg).unwrap_or(0);
#[cfg(feature = "tracing")]
tracing::debug!(
target: "eyeball_im::vector::broadcast",
"New observable value broadcast to {_num_receivers} receivers"
);
}
}
/// Roll back all changes made using this transaction so far.
///
/// Same as dropping the transaction and starting a new one, semantically.
pub fn rollback(&mut self) {
#[cfg(feature = "tracing")]
tracing::debug!("rollback (explicit)");
self.values = self.inner.values.clone();
self.batch.clear();
}
/// Append the given elements at the end of the `Vector` and notify
/// subscribers.
pub fn append(&mut self, values: Vector<T>) {
#[cfg(feature = "tracing")]
tracing::debug!(
target: "eyeball_im::vector::transaction::update",
"append(len = {})", values.len()
);
self.values.append(values.clone());
self.add_to_batch(VectorDiff::Append { values });
}
/// Clear out all of the elements in this `Vector` and notify subscribers.
pub fn clear(&mut self) {
#[cfg(feature = "tracing")]
tracing::debug!(target: "eyeball_im::vector::transaction::update", "clear");
self.values.clear();
self.batch.clear(); // All previous batched updates are irrelevant now
self.add_to_batch(VectorDiff::Clear);
}
/// Add an element at the front of the list and notify subscribers.
pub fn push_front(&mut self, value: T) {
#[cfg(feature = "tracing")]
tracing::debug!(target: "eyeball_im::vector::transaction::update", "push_front");
self.values.push_front(value.clone());
self.add_to_batch(VectorDiff::PushFront { value });
}
/// Add an element at the back of the list and notify subscribers.
pub fn push_back(&mut self, value: T) {
#[cfg(feature = "tracing")]
tracing::debug!(target: "eyeball_im::vector::transaction::update", "push_back");
self.values.push_back(value.clone());
self.add_to_batch(VectorDiff::PushBack { value });
}
/// Remove the first element, notify subscribers and return the element.
///
/// If there are no elements, subscribers will not be notified and this
/// method will return `None`.
pub fn pop_front(&mut self) -> Option<T> {
let value = self.values.pop_front();
if value.is_some() {
#[cfg(feature = "tracing")]
tracing::debug!(target: "eyeball_im::vector::transaction::update", "pop_front");
self.add_to_batch(VectorDiff::PopFront);
}
value
}
/// Remove the last element, notify subscribers and return the element.
///
/// If there are no elements, subscribers will not be notified and this
/// method will return `None`.
pub fn pop_back(&mut self) -> Option<T> {
let value = self.values.pop_back();
if value.is_some() {
#[cfg(feature = "tracing")]
tracing::debug!(target: "eyeball_im::vector::transaction::update", "pop_back");
self.add_to_batch(VectorDiff::PopBack);
}
value
}
/// Insert an element at the given position and notify subscribers.
///
/// # Panics
///
/// Panics if `index > len`.
#[track_caller]
pub fn insert(&mut self, index: usize, value: T) {
let len = self.values.len();
if index <= len {
#[cfg(feature = "tracing")]
tracing::debug!(
target: "eyeball_im::vector::transaction::update",
"insert(index = {index})"
);
self.values.insert(index, value.clone());
self.add_to_batch(VectorDiff::Insert { index, value });
} else {
panic!("index out of bounds: the length is {len} but the index is {index}");
}
}
/// Replace the element at the given position, notify subscribers and return
/// the previous element at that position.
///
/// # Panics
///
/// Panics if `index > len`.
#[track_caller]
pub fn set(&mut self, index: usize, value: T) -> T {
let len = self.values.len();
if index < len {
#[cfg(feature = "tracing")]
tracing::debug!(
target: "eyeball_im::vector::transaction::update",
"set(index = {index})"
);
let old_value = self.values.set(index, value.clone());
self.add_to_batch(VectorDiff::Set { index, value });
old_value
} else {
panic!("index out of bounds: the length is {len} but the index is {index}");
}
}
/// Remove the element at the given position, notify subscribers and return
/// the element.
///
/// # Panics
///
/// Panics if `index >= len`.
#[track_caller]
pub fn remove(&mut self, index: usize) -> T {
let len = self.values.len();
if index < len {
#[cfg(feature = "tracing")]
tracing::debug!(
target: "eyeball_im::vector::transaction::update",
"remove(index = {index})"
);
let value = self.values.remove(index);
self.add_to_batch(VectorDiff::Remove { index });
value
} else {
panic!("index out of bounds: the length is {len} but the index is {index}");
}
}
/// Truncate the vector to `len` elements and notify subscribers.
///
/// Does nothing if `len` is greater or equal to the vector's current
/// length.
pub fn truncate(&mut self, len: usize) {
if len < self.len() {
#[cfg(feature = "tracing")]
tracing::debug!(target: "eyeball_im::vector::update", "truncate(len = {len})");
self.values.truncate(len);
self.add_to_batch(VectorDiff::Truncate { length: len });
}
}
/// Gets an entry for the given index through which only the element at that
/// index alone can be updated or removed.
///
/// # Panics
///
/// Panics if `index >= len`.
#[track_caller]
pub fn entry(&mut self, index: usize) -> ObservableVectorTransactionEntry<'_, 'o, T> {
let len = self.values.len();
if index < len {
ObservableVectorTransactionEntry::new(self, index)
} else {
panic!("index out of bounds: the length is {len} but the index is {index}");
}
}
/// Call the given closure for every element in this `ObservableVector`,
/// with an entry struct that allows updating or removing that element.
///
/// Iteration happens in order, i.e. starting at index `0`.
pub fn for_each(&mut self, mut f: impl FnMut(ObservableVectorTransactionEntry<'_, 'o, T>)) {
let mut entries = self.entries();
while let Some(entry) = entries.next() {
f(entry);
}
}
/// Get an iterator over all the entries in this `ObservableVector`.
///
/// This is a more flexible, but less convenient alternative to
/// [`for_each`][Self::for_each]. If you don't need to use special control
/// flow like `.await` or `break` when iterating, it's recommended to use
/// that method instead.
///
/// Because `std`'s `Iterator` trait does not allow iterator items to borrow
/// from the iterator itself, the returned typed does not implement the
/// `Iterator` trait and can thus not be used with a `for` loop. Instead,
/// you have to call its `.next()` method directly, as in:
///
/// ```rust
/// # use eyeball_im::ObservableVector;
/// # let mut ob = ObservableVector::<u8>::new();
/// let mut entries = ob.entries();
/// while let Some(entry) = entries.next() {
/// // use entry
/// }
/// ```
pub fn entries(&mut self) -> ObservableVectorTransactionEntries<'_, 'o, T> {
ObservableVectorTransactionEntries::new(self)
}
fn add_to_batch(&mut self, diff: VectorDiff<T>) {
if self.inner.sender.receiver_count() != 0 {
self.batch.push(diff);
}
}
}
impl<T> fmt::Debug for ObservableVectorTransaction<'_, T>
where
T: Clone + fmt::Debug,
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("ObservableVectorWriteGuard")
.field("values", &self.values)
.finish_non_exhaustive()
}
}
// Note: No DerefMut because all mutating must go through inherent methods that
// notify subscribers
impl<T: Clone> ops::Deref for ObservableVectorTransaction<'_, T> {
type Target = Vector<T>;
fn deref(&self) -> &Self::Target {
&self.values
}
}
impl<T: Clone> Drop for ObservableVectorTransaction<'_, T> {
fn drop(&mut self) {
#[cfg(feature = "tracing")]
if !self.batch.is_empty() {
tracing::debug!("rollback (drop)");
}
}
}
/// A handle to a single value in an [`ObservableVector`], obtained from a
/// transaction.
pub struct ObservableVectorTransactionEntry<'a, 'o, T: Clone> {
inner: &'a mut ObservableVectorTransaction<'o, T>,
index: EntryIndex<'a>,
}
impl<'a, 'o, T> ObservableVectorTransactionEntry<'a, 'o, T>
where
T: Clone + 'static,
{
pub(super) fn new(inner: &'a mut ObservableVectorTransaction<'o, T>, index: usize) -> Self {
Self { inner, index: EntryIndex::Owned(index) }
}
fn new_borrowed(
inner: &'a mut ObservableVectorTransaction<'o, T>,
index: &'a mut usize,
) -> Self {
Self { inner, index: EntryIndex::Borrowed(index) }
}
/// Get the index of the element this `ObservableVectorEntry` refers to.
pub fn index(this: &Self) -> usize {
this.index.value()
}
/// Replace the given element, notify subscribers and return the previous
/// element.
pub fn set(this: &mut Self, value: T) -> T {
this.inner.set(this.index.value(), value)
}
/// Remove the given element, notify subscribers and return the element.
pub fn remove(mut this: Self) -> T {
this.inner.remove(this.index.make_owned())
}
}
impl<T> fmt::Debug for ObservableVectorTransactionEntry<'_, '_, T>
where
T: Clone + fmt::Debug,
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
let index = self.index.value();
f.debug_struct("ObservableVectorEntry")
.field("item", &self.inner[index])
.field("index", &index)
.finish()
}
}
impl<T: Clone> ops::Deref for ObservableVectorTransactionEntry<'_, '_, T> {
type Target = T;
fn deref(&self) -> &Self::Target {
&self.inner[self.index.value()]
}
}
impl<T: Clone> Drop for ObservableVectorTransactionEntry<'_, '_, T> {
fn drop(&mut self) {
// If there is an association with an externally-stored index, that
// index must be incremented on drop. This allows an external iterator
// that produces ObservableVectorEntry items to advance conditionally.
//
// There are two cases this branch is not hit:
//
// - make_owned was previously called (used for removing the item and resuming
// iteration with the same index)
// - the ObservableVectorEntry was created with ObservableVector::entry, i.e.
// it's not used for iteration at all
if let EntryIndex::Borrowed(idx) = &mut self.index {
**idx += 1;
}
}
}
/// An "iterator"¹ that yields entries into an [`ObservableVector`], obtained
/// from a transaction.
///
/// ¹ conceptually, though it does not implement `std::iterator::Iterator`
#[derive(Debug)]
pub struct ObservableVectorTransactionEntries<'a, 'o, T: Clone> {
inner: &'a mut ObservableVectorTransaction<'o, T>,
index: usize,
}
impl<'a, 'o, T> ObservableVectorTransactionEntries<'a, 'o, T>
where
T: Clone + 'static,
{
pub(super) fn new(inner: &'a mut ObservableVectorTransaction<'o, T>) -> Self {
Self { inner, index: 0 }
}
/// Advance this iterator, yielding an `ObservableVectorEntry` for the next
/// item in the vector, or `None` if all items have been visited.
#[allow(clippy::should_implement_trait)]
pub fn next(&mut self) -> Option<ObservableVectorTransactionEntry<'_, 'o, T>> {
if self.index < self.inner.len() {
Some(ObservableVectorTransactionEntry::new_borrowed(self.inner, &mut self.index))
} else {
None
}
}
}