1mod cursor;
   2mod tree_map;
   3
   4use arrayvec::ArrayVec;
   5pub use cursor::{Cursor, FilterCursor, Iter};
   6use rayon::prelude::*;
   7use std::marker::PhantomData;
   8use std::mem;
   9use std::{cmp::Ordering, fmt, iter::FromIterator, sync::Arc};
  10pub use tree_map::{MapSeekTarget, TreeMap, TreeSet};
  11
  12#[cfg(test)]
  13pub const TREE_BASE: usize = 2;
  14#[cfg(not(test))]
  15pub const TREE_BASE: usize = 6;
  16
  17pub trait Item: Clone {
  18    type Summary: Summary;
  19
  20    fn summary(&self) -> Self::Summary;
  21}
  22
  23pub trait KeyedItem: Item {
  24    type Key: for<'a> Dimension<'a, Self::Summary> + Ord;
  25
  26    fn key(&self) -> Self::Key;
  27}
  28
  29pub trait Summary: Default + Clone + fmt::Debug {
  30    type Context;
  31
  32    fn add_summary(&mut self, summary: &Self, cx: &Self::Context);
  33}
  34
  35pub trait Dimension<'a, S: Summary>: Clone + fmt::Debug + Default {
  36    fn add_summary(&mut self, _summary: &'a S, _: &S::Context);
  37
  38    fn from_summary(summary: &'a S, cx: &S::Context) -> Self {
  39        let mut dimension = Self::default();
  40        dimension.add_summary(summary, cx);
  41        dimension
  42    }
  43}
  44
  45impl<'a, T: Summary> Dimension<'a, T> for T {
  46    fn add_summary(&mut self, summary: &'a T, cx: &T::Context) {
  47        Summary::add_summary(self, summary, cx);
  48    }
  49}
  50
  51pub trait SeekTarget<'a, S: Summary, D: Dimension<'a, S>>: fmt::Debug {
  52    fn cmp(&self, cursor_location: &D, cx: &S::Context) -> Ordering;
  53}
  54
  55impl<'a, S: Summary, D: Dimension<'a, S> + Ord> SeekTarget<'a, S, D> for D {
  56    fn cmp(&self, cursor_location: &Self, _: &S::Context) -> Ordering {
  57        Ord::cmp(self, cursor_location)
  58    }
  59}
  60
  61impl<'a, T: Summary> Dimension<'a, T> for () {
  62    fn add_summary(&mut self, _: &'a T, _: &T::Context) {}
  63}
  64
  65impl<'a, T: Summary, D1: Dimension<'a, T>, D2: Dimension<'a, T>> Dimension<'a, T> for (D1, D2) {
  66    fn add_summary(&mut self, summary: &'a T, cx: &T::Context) {
  67        self.0.add_summary(summary, cx);
  68        self.1.add_summary(summary, cx);
  69    }
  70}
  71
  72impl<'a, S: Summary, D1: SeekTarget<'a, S, D1> + Dimension<'a, S>, D2: Dimension<'a, S>>
  73    SeekTarget<'a, S, (D1, D2)> for D1
  74{
  75    fn cmp(&self, cursor_location: &(D1, D2), cx: &S::Context) -> Ordering {
  76        self.cmp(&cursor_location.0, cx)
  77    }
  78}
  79
  80struct End<D>(PhantomData<D>);
  81
  82impl<D> End<D> {
  83    fn new() -> Self {
  84        Self(PhantomData)
  85    }
  86}
  87
  88impl<'a, S: Summary, D: Dimension<'a, S>> SeekTarget<'a, S, D> for End<D> {
  89    fn cmp(&self, _: &D, _: &S::Context) -> Ordering {
  90        Ordering::Greater
  91    }
  92}
  93
  94impl<D> fmt::Debug for End<D> {
  95    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  96        f.debug_tuple("End").finish()
  97    }
  98}
  99
 100#[derive(Copy, Clone, Eq, PartialEq, PartialOrd, Ord, Debug, Hash, Default)]
 101pub enum Bias {
 102    #[default]
 103    Left,
 104    Right,
 105}
 106
 107impl Bias {
 108    pub fn invert(self) -> Self {
 109        match self {
 110            Self::Left => Self::Right,
 111            Self::Right => Self::Left,
 112        }
 113    }
 114}
 115
 116#[derive(Debug, Clone)]
 117pub struct SumTree<T: Item>(Arc<Node<T>>);
 118
 119impl<T: Item> SumTree<T> {
 120    pub fn new() -> Self {
 121        SumTree(Arc::new(Node::Leaf {
 122            summary: T::Summary::default(),
 123            items: ArrayVec::new(),
 124            item_summaries: ArrayVec::new(),
 125        }))
 126    }
 127
 128    pub fn from_item(item: T, cx: &<T::Summary as Summary>::Context) -> Self {
 129        let mut tree = Self::new();
 130        tree.push(item, cx);
 131        tree
 132    }
 133
 134    pub fn from_iter<I: IntoIterator<Item = T>>(
 135        iter: I,
 136        cx: &<T::Summary as Summary>::Context,
 137    ) -> Self {
 138        let mut nodes = Vec::new();
 139
 140        let mut iter = iter.into_iter().peekable();
 141        while iter.peek().is_some() {
 142            let items: ArrayVec<T, { 2 * TREE_BASE }> = iter.by_ref().take(2 * TREE_BASE).collect();
 143            let item_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }> =
 144                items.iter().map(|item| item.summary()).collect();
 145
 146            let mut summary = item_summaries[0].clone();
 147            for item_summary in &item_summaries[1..] {
 148                <T::Summary as Summary>::add_summary(&mut summary, item_summary, cx);
 149            }
 150
 151            nodes.push(Node::Leaf {
 152                summary,
 153                items,
 154                item_summaries,
 155            });
 156        }
 157
 158        let mut parent_nodes = Vec::new();
 159        let mut height = 0;
 160        while nodes.len() > 1 {
 161            height += 1;
 162            let mut current_parent_node = None;
 163            for child_node in nodes.drain(..) {
 164                let parent_node = current_parent_node.get_or_insert_with(|| Node::Internal {
 165                    summary: T::Summary::default(),
 166                    height,
 167                    child_summaries: ArrayVec::new(),
 168                    child_trees: ArrayVec::new(),
 169                });
 170                let Node::Internal {
 171                    summary,
 172                    child_summaries,
 173                    child_trees,
 174                    ..
 175                } = parent_node
 176                else {
 177                    unreachable!()
 178                };
 179                let child_summary = child_node.summary();
 180                <T::Summary as Summary>::add_summary(summary, child_summary, cx);
 181                child_summaries.push(child_summary.clone());
 182                child_trees.push(Self(Arc::new(child_node)));
 183
 184                if child_trees.len() == 2 * TREE_BASE {
 185                    parent_nodes.extend(current_parent_node.take());
 186                }
 187            }
 188            parent_nodes.extend(current_parent_node.take());
 189            mem::swap(&mut nodes, &mut parent_nodes);
 190        }
 191
 192        if nodes.is_empty() {
 193            Self::new()
 194        } else {
 195            debug_assert_eq!(nodes.len(), 1);
 196            Self(Arc::new(nodes.pop().unwrap()))
 197        }
 198    }
 199
 200    pub fn from_par_iter<I, Iter>(iter: I, cx: &<T::Summary as Summary>::Context) -> Self
 201    where
 202        I: IntoParallelIterator<Iter = Iter>,
 203        Iter: IndexedParallelIterator<Item = T>,
 204        T: Send + Sync,
 205        T::Summary: Send + Sync,
 206        <T::Summary as Summary>::Context: Sync,
 207    {
 208        let mut nodes = iter
 209            .into_par_iter()
 210            .chunks(2 * TREE_BASE)
 211            .map(|items| {
 212                let items: ArrayVec<T, { 2 * TREE_BASE }> = items.into_iter().collect();
 213                let item_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }> =
 214                    items.iter().map(|item| item.summary()).collect();
 215                let mut summary = item_summaries[0].clone();
 216                for item_summary in &item_summaries[1..] {
 217                    <T::Summary as Summary>::add_summary(&mut summary, item_summary, cx);
 218                }
 219                SumTree(Arc::new(Node::Leaf {
 220                    summary,
 221                    items,
 222                    item_summaries,
 223                }))
 224            })
 225            .collect::<Vec<_>>();
 226
 227        let mut height = 0;
 228        while nodes.len() > 1 {
 229            height += 1;
 230            nodes = nodes
 231                .into_par_iter()
 232                .chunks(2 * TREE_BASE)
 233                .map(|child_nodes| {
 234                    let child_trees: ArrayVec<SumTree<T>, { 2 * TREE_BASE }> =
 235                        child_nodes.into_iter().collect();
 236                    let child_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }> = child_trees
 237                        .iter()
 238                        .map(|child_tree| child_tree.summary().clone())
 239                        .collect();
 240                    let mut summary = child_summaries[0].clone();
 241                    for child_summary in &child_summaries[1..] {
 242                        <T::Summary as Summary>::add_summary(&mut summary, child_summary, cx);
 243                    }
 244                    SumTree(Arc::new(Node::Internal {
 245                        height,
 246                        summary,
 247                        child_summaries,
 248                        child_trees,
 249                    }))
 250                })
 251                .collect::<Vec<_>>();
 252        }
 253
 254        if nodes.is_empty() {
 255            Self::new()
 256        } else {
 257            debug_assert_eq!(nodes.len(), 1);
 258            nodes.pop().unwrap()
 259        }
 260    }
 261
 262    #[allow(unused)]
 263    pub fn items(&self, cx: &<T::Summary as Summary>::Context) -> Vec<T> {
 264        let mut items = Vec::new();
 265        let mut cursor = self.cursor::<()>();
 266        cursor.next(cx);
 267        while let Some(item) = cursor.item() {
 268            items.push(item.clone());
 269            cursor.next(cx);
 270        }
 271        items
 272    }
 273
 274    pub fn iter(&self) -> Iter<T> {
 275        Iter::new(self)
 276    }
 277
 278    pub fn cursor<'a, S>(&'a self) -> Cursor<T, S>
 279    where
 280        S: Dimension<'a, T::Summary>,
 281    {
 282        Cursor::new(self)
 283    }
 284
 285    /// Note: If the summary type requires a non `()` context, then the filter cursor
 286    /// that is returned cannot be used with Rust's iterators.
 287    pub fn filter<'a, F, U>(&'a self, filter_node: F) -> FilterCursor<F, T, U>
 288    where
 289        F: FnMut(&T::Summary) -> bool,
 290        U: Dimension<'a, T::Summary>,
 291    {
 292        FilterCursor::new(self, filter_node)
 293    }
 294
 295    #[allow(dead_code)]
 296    pub fn first(&self) -> Option<&T> {
 297        self.leftmost_leaf().0.items().first()
 298    }
 299
 300    pub fn last(&self) -> Option<&T> {
 301        self.rightmost_leaf().0.items().last()
 302    }
 303
 304    pub fn update_last(&mut self, f: impl FnOnce(&mut T), cx: &<T::Summary as Summary>::Context) {
 305        self.update_last_recursive(f, cx);
 306    }
 307
 308    fn update_last_recursive(
 309        &mut self,
 310        f: impl FnOnce(&mut T),
 311        cx: &<T::Summary as Summary>::Context,
 312    ) -> Option<T::Summary> {
 313        match Arc::make_mut(&mut self.0) {
 314            Node::Internal {
 315                summary,
 316                child_summaries,
 317                child_trees,
 318                ..
 319            } => {
 320                let last_summary = child_summaries.last_mut().unwrap();
 321                let last_child = child_trees.last_mut().unwrap();
 322                *last_summary = last_child.update_last_recursive(f, cx).unwrap();
 323                *summary = sum(child_summaries.iter(), cx);
 324                Some(summary.clone())
 325            }
 326            Node::Leaf {
 327                summary,
 328                items,
 329                item_summaries,
 330            } => {
 331                if let Some((item, item_summary)) = items.last_mut().zip(item_summaries.last_mut())
 332                {
 333                    (f)(item);
 334                    *item_summary = item.summary();
 335                    *summary = sum(item_summaries.iter(), cx);
 336                    Some(summary.clone())
 337                } else {
 338                    None
 339                }
 340            }
 341        }
 342    }
 343
 344    pub fn extent<'a, D: Dimension<'a, T::Summary>>(
 345        &'a self,
 346        cx: &<T::Summary as Summary>::Context,
 347    ) -> D {
 348        let mut extent = D::default();
 349        match self.0.as_ref() {
 350            Node::Internal { summary, .. } | Node::Leaf { summary, .. } => {
 351                extent.add_summary(summary, cx);
 352            }
 353        }
 354        extent
 355    }
 356
 357    pub fn summary(&self) -> &T::Summary {
 358        match self.0.as_ref() {
 359            Node::Internal { summary, .. } => summary,
 360            Node::Leaf { summary, .. } => summary,
 361        }
 362    }
 363
 364    pub fn is_empty(&self) -> bool {
 365        match self.0.as_ref() {
 366            Node::Internal { .. } => false,
 367            Node::Leaf { items, .. } => items.is_empty(),
 368        }
 369    }
 370
 371    pub fn extend<I>(&mut self, iter: I, cx: &<T::Summary as Summary>::Context)
 372    where
 373        I: IntoIterator<Item = T>,
 374    {
 375        self.append(Self::from_iter(iter, cx), cx);
 376    }
 377
 378    pub fn par_extend<I, Iter>(&mut self, iter: I, cx: &<T::Summary as Summary>::Context)
 379    where
 380        I: IntoParallelIterator<Iter = Iter>,
 381        Iter: IndexedParallelIterator<Item = T>,
 382        T: Send + Sync,
 383        T::Summary: Send + Sync,
 384        <T::Summary as Summary>::Context: Sync,
 385    {
 386        self.append(Self::from_par_iter(iter, cx), cx);
 387    }
 388
 389    pub fn push(&mut self, item: T, cx: &<T::Summary as Summary>::Context) {
 390        let summary = item.summary();
 391        self.append(
 392            SumTree(Arc::new(Node::Leaf {
 393                summary: summary.clone(),
 394                items: ArrayVec::from_iter(Some(item)),
 395                item_summaries: ArrayVec::from_iter(Some(summary)),
 396            })),
 397            cx,
 398        );
 399    }
 400
 401    pub fn append(&mut self, other: Self, cx: &<T::Summary as Summary>::Context) {
 402        if self.is_empty() {
 403            *self = other;
 404        } else if !other.0.is_leaf() || !other.0.items().is_empty() {
 405            if self.0.height() < other.0.height() {
 406                for tree in other.0.child_trees() {
 407                    self.append(tree.clone(), cx);
 408                }
 409            } else if let Some(split_tree) = self.push_tree_recursive(other, cx) {
 410                *self = Self::from_child_trees(self.clone(), split_tree, cx);
 411            }
 412        }
 413    }
 414
 415    fn push_tree_recursive(
 416        &mut self,
 417        other: SumTree<T>,
 418        cx: &<T::Summary as Summary>::Context,
 419    ) -> Option<SumTree<T>> {
 420        match Arc::make_mut(&mut self.0) {
 421            Node::Internal {
 422                height,
 423                summary,
 424                child_summaries,
 425                child_trees,
 426                ..
 427            } => {
 428                let other_node = other.0.clone();
 429                <T::Summary as Summary>::add_summary(summary, other_node.summary(), cx);
 430
 431                let height_delta = *height - other_node.height();
 432                let mut summaries_to_append = ArrayVec::<T::Summary, { 2 * TREE_BASE }>::new();
 433                let mut trees_to_append = ArrayVec::<SumTree<T>, { 2 * TREE_BASE }>::new();
 434                if height_delta == 0 {
 435                    summaries_to_append.extend(other_node.child_summaries().iter().cloned());
 436                    trees_to_append.extend(other_node.child_trees().iter().cloned());
 437                } else if height_delta == 1 && !other_node.is_underflowing() {
 438                    summaries_to_append.push(other_node.summary().clone());
 439                    trees_to_append.push(other)
 440                } else {
 441                    let tree_to_append = child_trees
 442                        .last_mut()
 443                        .unwrap()
 444                        .push_tree_recursive(other, cx);
 445                    *child_summaries.last_mut().unwrap() =
 446                        child_trees.last().unwrap().0.summary().clone();
 447
 448                    if let Some(split_tree) = tree_to_append {
 449                        summaries_to_append.push(split_tree.0.summary().clone());
 450                        trees_to_append.push(split_tree);
 451                    }
 452                }
 453
 454                let child_count = child_trees.len() + trees_to_append.len();
 455                if child_count > 2 * TREE_BASE {
 456                    let left_summaries: ArrayVec<_, { 2 * TREE_BASE }>;
 457                    let right_summaries: ArrayVec<_, { 2 * TREE_BASE }>;
 458                    let left_trees;
 459                    let right_trees;
 460
 461                    let midpoint = (child_count + child_count % 2) / 2;
 462                    {
 463                        let mut all_summaries = child_summaries
 464                            .iter()
 465                            .chain(summaries_to_append.iter())
 466                            .cloned();
 467                        left_summaries = all_summaries.by_ref().take(midpoint).collect();
 468                        right_summaries = all_summaries.collect();
 469                        let mut all_trees =
 470                            child_trees.iter().chain(trees_to_append.iter()).cloned();
 471                        left_trees = all_trees.by_ref().take(midpoint).collect();
 472                        right_trees = all_trees.collect();
 473                    }
 474                    *summary = sum(left_summaries.iter(), cx);
 475                    *child_summaries = left_summaries;
 476                    *child_trees = left_trees;
 477
 478                    Some(SumTree(Arc::new(Node::Internal {
 479                        height: *height,
 480                        summary: sum(right_summaries.iter(), cx),
 481                        child_summaries: right_summaries,
 482                        child_trees: right_trees,
 483                    })))
 484                } else {
 485                    child_summaries.extend(summaries_to_append);
 486                    child_trees.extend(trees_to_append);
 487                    None
 488                }
 489            }
 490            Node::Leaf {
 491                summary,
 492                items,
 493                item_summaries,
 494            } => {
 495                let other_node = other.0;
 496
 497                let child_count = items.len() + other_node.items().len();
 498                if child_count > 2 * TREE_BASE {
 499                    let left_items;
 500                    let right_items;
 501                    let left_summaries;
 502                    let right_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }>;
 503
 504                    let midpoint = (child_count + child_count % 2) / 2;
 505                    {
 506                        let mut all_items = items.iter().chain(other_node.items().iter()).cloned();
 507                        left_items = all_items.by_ref().take(midpoint).collect();
 508                        right_items = all_items.collect();
 509
 510                        let mut all_summaries = item_summaries
 511                            .iter()
 512                            .chain(other_node.child_summaries())
 513                            .cloned();
 514                        left_summaries = all_summaries.by_ref().take(midpoint).collect();
 515                        right_summaries = all_summaries.collect();
 516                    }
 517                    *items = left_items;
 518                    *item_summaries = left_summaries;
 519                    *summary = sum(item_summaries.iter(), cx);
 520                    Some(SumTree(Arc::new(Node::Leaf {
 521                        items: right_items,
 522                        summary: sum(right_summaries.iter(), cx),
 523                        item_summaries: right_summaries,
 524                    })))
 525                } else {
 526                    <T::Summary as Summary>::add_summary(summary, other_node.summary(), cx);
 527                    items.extend(other_node.items().iter().cloned());
 528                    item_summaries.extend(other_node.child_summaries().iter().cloned());
 529                    None
 530                }
 531            }
 532        }
 533    }
 534
 535    fn from_child_trees(
 536        left: SumTree<T>,
 537        right: SumTree<T>,
 538        cx: &<T::Summary as Summary>::Context,
 539    ) -> Self {
 540        let height = left.0.height() + 1;
 541        let mut child_summaries = ArrayVec::new();
 542        child_summaries.push(left.0.summary().clone());
 543        child_summaries.push(right.0.summary().clone());
 544        let mut child_trees = ArrayVec::new();
 545        child_trees.push(left);
 546        child_trees.push(right);
 547        SumTree(Arc::new(Node::Internal {
 548            height,
 549            summary: sum(child_summaries.iter(), cx),
 550            child_summaries,
 551            child_trees,
 552        }))
 553    }
 554
 555    fn leftmost_leaf(&self) -> &Self {
 556        match *self.0 {
 557            Node::Leaf { .. } => self,
 558            Node::Internal {
 559                ref child_trees, ..
 560            } => child_trees.first().unwrap().leftmost_leaf(),
 561        }
 562    }
 563
 564    fn rightmost_leaf(&self) -> &Self {
 565        match *self.0 {
 566            Node::Leaf { .. } => self,
 567            Node::Internal {
 568                ref child_trees, ..
 569            } => child_trees.last().unwrap().rightmost_leaf(),
 570        }
 571    }
 572
 573    #[cfg(debug_assertions)]
 574    pub fn _debug_entries(&self) -> Vec<&T> {
 575        self.iter().collect::<Vec<_>>()
 576    }
 577}
 578
 579impl<T: Item + PartialEq> PartialEq for SumTree<T> {
 580    fn eq(&self, other: &Self) -> bool {
 581        self.iter().eq(other.iter())
 582    }
 583}
 584
 585impl<T: Item + Eq> Eq for SumTree<T> {}
 586
 587impl<T: KeyedItem> SumTree<T> {
 588    pub fn insert_or_replace(
 589        &mut self,
 590        item: T,
 591        cx: &<T::Summary as Summary>::Context,
 592    ) -> Option<T> {
 593        let mut replaced = None;
 594        *self = {
 595            let mut cursor = self.cursor::<T::Key>();
 596            let mut new_tree = cursor.slice(&item.key(), Bias::Left, cx);
 597            if let Some(cursor_item) = cursor.item() {
 598                if cursor_item.key() == item.key() {
 599                    replaced = Some(cursor_item.clone());
 600                    cursor.next(cx);
 601                }
 602            }
 603            new_tree.push(item, cx);
 604            new_tree.append(cursor.suffix(cx), cx);
 605            new_tree
 606        };
 607        replaced
 608    }
 609
 610    pub fn remove(&mut self, key: &T::Key, cx: &<T::Summary as Summary>::Context) -> Option<T> {
 611        let mut removed = None;
 612        *self = {
 613            let mut cursor = self.cursor::<T::Key>();
 614            let mut new_tree = cursor.slice(key, Bias::Left, cx);
 615            if let Some(item) = cursor.item() {
 616                if item.key() == *key {
 617                    removed = Some(item.clone());
 618                    cursor.next(cx);
 619                }
 620            }
 621            new_tree.append(cursor.suffix(cx), cx);
 622            new_tree
 623        };
 624        removed
 625    }
 626
 627    pub fn edit(
 628        &mut self,
 629        mut edits: Vec<Edit<T>>,
 630        cx: &<T::Summary as Summary>::Context,
 631    ) -> Vec<T> {
 632        if edits.is_empty() {
 633            return Vec::new();
 634        }
 635
 636        let mut removed = Vec::new();
 637        edits.sort_unstable_by_key(|item| item.key());
 638
 639        *self = {
 640            let mut cursor = self.cursor::<T::Key>();
 641            let mut new_tree = SumTree::new();
 642            let mut buffered_items = Vec::new();
 643
 644            cursor.seek(&T::Key::default(), Bias::Left, cx);
 645            for edit in edits {
 646                let new_key = edit.key();
 647                let mut old_item = cursor.item();
 648
 649                if old_item
 650                    .as_ref()
 651                    .map_or(false, |old_item| old_item.key() < new_key)
 652                {
 653                    new_tree.extend(buffered_items.drain(..), cx);
 654                    let slice = cursor.slice(&new_key, Bias::Left, cx);
 655                    new_tree.append(slice, cx);
 656                    old_item = cursor.item();
 657                }
 658
 659                if let Some(old_item) = old_item {
 660                    if old_item.key() == new_key {
 661                        removed.push(old_item.clone());
 662                        cursor.next(cx);
 663                    }
 664                }
 665
 666                match edit {
 667                    Edit::Insert(item) => {
 668                        buffered_items.push(item);
 669                    }
 670                    Edit::Remove(_) => {}
 671                }
 672            }
 673
 674            new_tree.extend(buffered_items, cx);
 675            new_tree.append(cursor.suffix(cx), cx);
 676            new_tree
 677        };
 678
 679        removed
 680    }
 681
 682    pub fn get(&self, key: &T::Key, cx: &<T::Summary as Summary>::Context) -> Option<&T> {
 683        let mut cursor = self.cursor::<T::Key>();
 684        if cursor.seek(key, Bias::Left, cx) {
 685            cursor.item()
 686        } else {
 687            None
 688        }
 689    }
 690}
 691
 692impl<T: Item> Default for SumTree<T> {
 693    fn default() -> Self {
 694        Self::new()
 695    }
 696}
 697
 698#[derive(Clone, Debug)]
 699pub enum Node<T: Item> {
 700    Internal {
 701        height: u8,
 702        summary: T::Summary,
 703        child_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }>,
 704        child_trees: ArrayVec<SumTree<T>, { 2 * TREE_BASE }>,
 705    },
 706    Leaf {
 707        summary: T::Summary,
 708        items: ArrayVec<T, { 2 * TREE_BASE }>,
 709        item_summaries: ArrayVec<T::Summary, { 2 * TREE_BASE }>,
 710    },
 711}
 712
 713impl<T: Item> Node<T> {
 714    fn is_leaf(&self) -> bool {
 715        matches!(self, Node::Leaf { .. })
 716    }
 717
 718    fn height(&self) -> u8 {
 719        match self {
 720            Node::Internal { height, .. } => *height,
 721            Node::Leaf { .. } => 0,
 722        }
 723    }
 724
 725    fn summary(&self) -> &T::Summary {
 726        match self {
 727            Node::Internal { summary, .. } => summary,
 728            Node::Leaf { summary, .. } => summary,
 729        }
 730    }
 731
 732    fn child_summaries(&self) -> &[T::Summary] {
 733        match self {
 734            Node::Internal {
 735                child_summaries, ..
 736            } => child_summaries.as_slice(),
 737            Node::Leaf { item_summaries, .. } => item_summaries.as_slice(),
 738        }
 739    }
 740
 741    fn child_trees(&self) -> &ArrayVec<SumTree<T>, { 2 * TREE_BASE }> {
 742        match self {
 743            Node::Internal { child_trees, .. } => child_trees,
 744            Node::Leaf { .. } => panic!("Leaf nodes have no child trees"),
 745        }
 746    }
 747
 748    fn items(&self) -> &ArrayVec<T, { 2 * TREE_BASE }> {
 749        match self {
 750            Node::Leaf { items, .. } => items,
 751            Node::Internal { .. } => panic!("Internal nodes have no items"),
 752        }
 753    }
 754
 755    fn is_underflowing(&self) -> bool {
 756        match self {
 757            Node::Internal { child_trees, .. } => child_trees.len() < TREE_BASE,
 758            Node::Leaf { items, .. } => items.len() < TREE_BASE,
 759        }
 760    }
 761}
 762
 763#[derive(Debug)]
 764pub enum Edit<T: KeyedItem> {
 765    Insert(T),
 766    Remove(T::Key),
 767}
 768
 769impl<T: KeyedItem> Edit<T> {
 770    fn key(&self) -> T::Key {
 771        match self {
 772            Edit::Insert(item) => item.key(),
 773            Edit::Remove(key) => key.clone(),
 774        }
 775    }
 776}
 777
 778fn sum<'a, T, I>(iter: I, cx: &T::Context) -> T
 779where
 780    T: 'a + Summary,
 781    I: Iterator<Item = &'a T>,
 782{
 783    let mut sum = T::default();
 784    for value in iter {
 785        sum.add_summary(value, cx);
 786    }
 787    sum
 788}
 789
 790#[cfg(test)]
 791mod tests {
 792    use super::*;
 793    use rand::{distributions, prelude::*};
 794    use std::cmp;
 795
 796    #[ctor::ctor]
 797    fn init_logger() {
 798        if std::env::var("RUST_LOG").is_ok() {
 799            env_logger::init();
 800        }
 801    }
 802
 803    #[test]
 804    fn test_extend_and_push_tree() {
 805        let mut tree1 = SumTree::new();
 806        tree1.extend(0..20, &());
 807
 808        let mut tree2 = SumTree::new();
 809        tree2.extend(50..100, &());
 810
 811        tree1.append(tree2, &());
 812        assert_eq!(
 813            tree1.items(&()),
 814            (0..20).chain(50..100).collect::<Vec<u8>>()
 815        );
 816    }
 817
 818    #[test]
 819    fn test_random() {
 820        let mut starting_seed = 0;
 821        if let Ok(value) = std::env::var("SEED") {
 822            starting_seed = value.parse().expect("invalid SEED variable");
 823        }
 824        let mut num_iterations = 100;
 825        if let Ok(value) = std::env::var("ITERATIONS") {
 826            num_iterations = value.parse().expect("invalid ITERATIONS variable");
 827        }
 828        let num_operations = std::env::var("OPERATIONS")
 829            .map_or(5, |o| o.parse().expect("invalid OPERATIONS variable"));
 830
 831        for seed in starting_seed..(starting_seed + num_iterations) {
 832            eprintln!("seed = {}", seed);
 833            let mut rng = StdRng::seed_from_u64(seed);
 834
 835            let rng = &mut rng;
 836            let mut tree = SumTree::<u8>::new();
 837            let count = rng.gen_range(0..10);
 838            if rng.gen() {
 839                tree.extend(rng.sample_iter(distributions::Standard).take(count), &());
 840            } else {
 841                let items = rng
 842                    .sample_iter(distributions::Standard)
 843                    .take(count)
 844                    .collect::<Vec<_>>();
 845                tree.par_extend(items, &());
 846            }
 847
 848            for _ in 0..num_operations {
 849                let splice_end = rng.gen_range(0..tree.extent::<Count>(&()).0 + 1);
 850                let splice_start = rng.gen_range(0..splice_end + 1);
 851                let count = rng.gen_range(0..10);
 852                let tree_end = tree.extent::<Count>(&());
 853                let new_items = rng
 854                    .sample_iter(distributions::Standard)
 855                    .take(count)
 856                    .collect::<Vec<u8>>();
 857
 858                let mut reference_items = tree.items(&());
 859                reference_items.splice(splice_start..splice_end, new_items.clone());
 860
 861                tree = {
 862                    let mut cursor = tree.cursor::<Count>();
 863                    let mut new_tree = cursor.slice(&Count(splice_start), Bias::Right, &());
 864                    if rng.gen() {
 865                        new_tree.extend(new_items, &());
 866                    } else {
 867                        new_tree.par_extend(new_items, &());
 868                    }
 869                    cursor.seek(&Count(splice_end), Bias::Right, &());
 870                    new_tree.append(cursor.slice(&tree_end, Bias::Right, &()), &());
 871                    new_tree
 872                };
 873
 874                assert_eq!(tree.items(&()), reference_items);
 875                assert_eq!(
 876                    tree.iter().collect::<Vec<_>>(),
 877                    tree.cursor::<()>().collect::<Vec<_>>()
 878                );
 879
 880                log::info!("tree items: {:?}", tree.items(&()));
 881
 882                let mut filter_cursor = tree.filter::<_, Count>(|summary| summary.contains_even);
 883                let expected_filtered_items = tree
 884                    .items(&())
 885                    .into_iter()
 886                    .enumerate()
 887                    .filter(|(_, item)| (item & 1) == 0)
 888                    .collect::<Vec<_>>();
 889
 890                let mut item_ix = if rng.gen() {
 891                    filter_cursor.next(&());
 892                    0
 893                } else {
 894                    filter_cursor.prev(&());
 895                    expected_filtered_items.len().saturating_sub(1)
 896                };
 897                while item_ix < expected_filtered_items.len() {
 898                    log::info!("filter_cursor, item_ix: {}", item_ix);
 899                    let actual_item = filter_cursor.item().unwrap();
 900                    let (reference_index, reference_item) = expected_filtered_items[item_ix];
 901                    assert_eq!(actual_item, &reference_item);
 902                    assert_eq!(filter_cursor.start().0, reference_index);
 903                    log::info!("next");
 904                    filter_cursor.next(&());
 905                    item_ix += 1;
 906
 907                    while item_ix > 0 && rng.gen_bool(0.2) {
 908                        log::info!("prev");
 909                        filter_cursor.prev(&());
 910                        item_ix -= 1;
 911
 912                        if item_ix == 0 && rng.gen_bool(0.2) {
 913                            filter_cursor.prev(&());
 914                            assert_eq!(filter_cursor.item(), None);
 915                            assert_eq!(filter_cursor.start().0, 0);
 916                            filter_cursor.next(&());
 917                        }
 918                    }
 919                }
 920                assert_eq!(filter_cursor.item(), None);
 921
 922                let mut before_start = false;
 923                let mut cursor = tree.cursor::<Count>();
 924                let start_pos = rng.gen_range(0..=reference_items.len());
 925                cursor.seek(&Count(start_pos), Bias::Right, &());
 926                let mut pos = rng.gen_range(start_pos..=reference_items.len());
 927                cursor.seek_forward(&Count(pos), Bias::Right, &());
 928
 929                for i in 0..10 {
 930                    assert_eq!(cursor.start().0, pos);
 931
 932                    if pos > 0 {
 933                        assert_eq!(cursor.prev_item().unwrap(), &reference_items[pos - 1]);
 934                    } else {
 935                        assert_eq!(cursor.prev_item(), None);
 936                    }
 937
 938                    if pos < reference_items.len() && !before_start {
 939                        assert_eq!(cursor.item().unwrap(), &reference_items[pos]);
 940                    } else {
 941                        assert_eq!(cursor.item(), None);
 942                    }
 943
 944                    if before_start {
 945                        assert_eq!(cursor.next_item(), reference_items.get(0));
 946                    } else if pos + 1 < reference_items.len() {
 947                        assert_eq!(cursor.next_item().unwrap(), &reference_items[pos + 1]);
 948                    } else {
 949                        assert_eq!(cursor.next_item(), None);
 950                    }
 951
 952                    if i < 5 {
 953                        cursor.next(&());
 954                        if pos < reference_items.len() {
 955                            pos += 1;
 956                            before_start = false;
 957                        }
 958                    } else {
 959                        cursor.prev(&());
 960                        if pos == 0 {
 961                            before_start = true;
 962                        }
 963                        pos = pos.saturating_sub(1);
 964                    }
 965                }
 966            }
 967
 968            for _ in 0..10 {
 969                let end = rng.gen_range(0..tree.extent::<Count>(&()).0 + 1);
 970                let start = rng.gen_range(0..end + 1);
 971                let start_bias = if rng.gen() { Bias::Left } else { Bias::Right };
 972                let end_bias = if rng.gen() { Bias::Left } else { Bias::Right };
 973
 974                let mut cursor = tree.cursor::<Count>();
 975                cursor.seek(&Count(start), start_bias, &());
 976                let slice = cursor.slice(&Count(end), end_bias, &());
 977
 978                cursor.seek(&Count(start), start_bias, &());
 979                let summary = cursor.summary::<_, Sum>(&Count(end), end_bias, &());
 980
 981                assert_eq!(summary.0, slice.summary().sum);
 982            }
 983        }
 984    }
 985
 986    #[test]
 987    fn test_cursor() {
 988        // Empty tree
 989        let tree = SumTree::<u8>::new();
 990        let mut cursor = tree.cursor::<IntegersSummary>();
 991        assert_eq!(
 992            cursor.slice(&Count(0), Bias::Right, &()).items(&()),
 993            Vec::<u8>::new()
 994        );
 995        assert_eq!(cursor.item(), None);
 996        assert_eq!(cursor.prev_item(), None);
 997        assert_eq!(cursor.next_item(), None);
 998        assert_eq!(cursor.start().sum, 0);
 999        cursor.prev(&());
1000        assert_eq!(cursor.item(), None);
1001        assert_eq!(cursor.prev_item(), None);
1002        assert_eq!(cursor.next_item(), None);
1003        assert_eq!(cursor.start().sum, 0);
1004        cursor.next(&());
1005        assert_eq!(cursor.item(), None);
1006        assert_eq!(cursor.prev_item(), None);
1007        assert_eq!(cursor.next_item(), None);
1008        assert_eq!(cursor.start().sum, 0);
1009
1010        // Single-element tree
1011        let mut tree = SumTree::<u8>::new();
1012        tree.extend(vec![1], &());
1013        let mut cursor = tree.cursor::<IntegersSummary>();
1014        assert_eq!(
1015            cursor.slice(&Count(0), Bias::Right, &()).items(&()),
1016            Vec::<u8>::new()
1017        );
1018        assert_eq!(cursor.item(), Some(&1));
1019        assert_eq!(cursor.prev_item(), None);
1020        assert_eq!(cursor.next_item(), None);
1021        assert_eq!(cursor.start().sum, 0);
1022
1023        cursor.next(&());
1024        assert_eq!(cursor.item(), None);
1025        assert_eq!(cursor.prev_item(), Some(&1));
1026        assert_eq!(cursor.next_item(), None);
1027        assert_eq!(cursor.start().sum, 1);
1028
1029        cursor.prev(&());
1030        assert_eq!(cursor.item(), Some(&1));
1031        assert_eq!(cursor.prev_item(), None);
1032        assert_eq!(cursor.next_item(), None);
1033        assert_eq!(cursor.start().sum, 0);
1034
1035        let mut cursor = tree.cursor::<IntegersSummary>();
1036        assert_eq!(cursor.slice(&Count(1), Bias::Right, &()).items(&()), [1]);
1037        assert_eq!(cursor.item(), None);
1038        assert_eq!(cursor.prev_item(), Some(&1));
1039        assert_eq!(cursor.next_item(), None);
1040        assert_eq!(cursor.start().sum, 1);
1041
1042        cursor.seek(&Count(0), Bias::Right, &());
1043        assert_eq!(
1044            cursor
1045                .slice(&tree.extent::<Count>(&()), Bias::Right, &())
1046                .items(&()),
1047            [1]
1048        );
1049        assert_eq!(cursor.item(), None);
1050        assert_eq!(cursor.prev_item(), Some(&1));
1051        assert_eq!(cursor.next_item(), None);
1052        assert_eq!(cursor.start().sum, 1);
1053
1054        // Multiple-element tree
1055        let mut tree = SumTree::new();
1056        tree.extend(vec![1, 2, 3, 4, 5, 6], &());
1057        let mut cursor = tree.cursor::<IntegersSummary>();
1058
1059        assert_eq!(cursor.slice(&Count(2), Bias::Right, &()).items(&()), [1, 2]);
1060        assert_eq!(cursor.item(), Some(&3));
1061        assert_eq!(cursor.prev_item(), Some(&2));
1062        assert_eq!(cursor.next_item(), Some(&4));
1063        assert_eq!(cursor.start().sum, 3);
1064
1065        cursor.next(&());
1066        assert_eq!(cursor.item(), Some(&4));
1067        assert_eq!(cursor.prev_item(), Some(&3));
1068        assert_eq!(cursor.next_item(), Some(&5));
1069        assert_eq!(cursor.start().sum, 6);
1070
1071        cursor.next(&());
1072        assert_eq!(cursor.item(), Some(&5));
1073        assert_eq!(cursor.prev_item(), Some(&4));
1074        assert_eq!(cursor.next_item(), Some(&6));
1075        assert_eq!(cursor.start().sum, 10);
1076
1077        cursor.next(&());
1078        assert_eq!(cursor.item(), Some(&6));
1079        assert_eq!(cursor.prev_item(), Some(&5));
1080        assert_eq!(cursor.next_item(), None);
1081        assert_eq!(cursor.start().sum, 15);
1082
1083        cursor.next(&());
1084        cursor.next(&());
1085        assert_eq!(cursor.item(), None);
1086        assert_eq!(cursor.prev_item(), Some(&6));
1087        assert_eq!(cursor.next_item(), None);
1088        assert_eq!(cursor.start().sum, 21);
1089
1090        cursor.prev(&());
1091        assert_eq!(cursor.item(), Some(&6));
1092        assert_eq!(cursor.prev_item(), Some(&5));
1093        assert_eq!(cursor.next_item(), None);
1094        assert_eq!(cursor.start().sum, 15);
1095
1096        cursor.prev(&());
1097        assert_eq!(cursor.item(), Some(&5));
1098        assert_eq!(cursor.prev_item(), Some(&4));
1099        assert_eq!(cursor.next_item(), Some(&6));
1100        assert_eq!(cursor.start().sum, 10);
1101
1102        cursor.prev(&());
1103        assert_eq!(cursor.item(), Some(&4));
1104        assert_eq!(cursor.prev_item(), Some(&3));
1105        assert_eq!(cursor.next_item(), Some(&5));
1106        assert_eq!(cursor.start().sum, 6);
1107
1108        cursor.prev(&());
1109        assert_eq!(cursor.item(), Some(&3));
1110        assert_eq!(cursor.prev_item(), Some(&2));
1111        assert_eq!(cursor.next_item(), Some(&4));
1112        assert_eq!(cursor.start().sum, 3);
1113
1114        cursor.prev(&());
1115        assert_eq!(cursor.item(), Some(&2));
1116        assert_eq!(cursor.prev_item(), Some(&1));
1117        assert_eq!(cursor.next_item(), Some(&3));
1118        assert_eq!(cursor.start().sum, 1);
1119
1120        cursor.prev(&());
1121        assert_eq!(cursor.item(), Some(&1));
1122        assert_eq!(cursor.prev_item(), None);
1123        assert_eq!(cursor.next_item(), Some(&2));
1124        assert_eq!(cursor.start().sum, 0);
1125
1126        cursor.prev(&());
1127        assert_eq!(cursor.item(), None);
1128        assert_eq!(cursor.prev_item(), None);
1129        assert_eq!(cursor.next_item(), Some(&1));
1130        assert_eq!(cursor.start().sum, 0);
1131
1132        cursor.next(&());
1133        assert_eq!(cursor.item(), Some(&1));
1134        assert_eq!(cursor.prev_item(), None);
1135        assert_eq!(cursor.next_item(), Some(&2));
1136        assert_eq!(cursor.start().sum, 0);
1137
1138        let mut cursor = tree.cursor::<IntegersSummary>();
1139        assert_eq!(
1140            cursor
1141                .slice(&tree.extent::<Count>(&()), Bias::Right, &())
1142                .items(&()),
1143            tree.items(&())
1144        );
1145        assert_eq!(cursor.item(), None);
1146        assert_eq!(cursor.prev_item(), Some(&6));
1147        assert_eq!(cursor.next_item(), None);
1148        assert_eq!(cursor.start().sum, 21);
1149
1150        cursor.seek(&Count(3), Bias::Right, &());
1151        assert_eq!(
1152            cursor
1153                .slice(&tree.extent::<Count>(&()), Bias::Right, &())
1154                .items(&()),
1155            [4, 5, 6]
1156        );
1157        assert_eq!(cursor.item(), None);
1158        assert_eq!(cursor.prev_item(), Some(&6));
1159        assert_eq!(cursor.next_item(), None);
1160        assert_eq!(cursor.start().sum, 21);
1161
1162        // Seeking can bias left or right
1163        cursor.seek(&Count(1), Bias::Left, &());
1164        assert_eq!(cursor.item(), Some(&1));
1165        cursor.seek(&Count(1), Bias::Right, &());
1166        assert_eq!(cursor.item(), Some(&2));
1167
1168        // Slicing without resetting starts from where the cursor is parked at.
1169        cursor.seek(&Count(1), Bias::Right, &());
1170        assert_eq!(
1171            cursor.slice(&Count(3), Bias::Right, &()).items(&()),
1172            vec![2, 3]
1173        );
1174        assert_eq!(
1175            cursor.slice(&Count(6), Bias::Left, &()).items(&()),
1176            vec![4, 5]
1177        );
1178        assert_eq!(
1179            cursor.slice(&Count(6), Bias::Right, &()).items(&()),
1180            vec![6]
1181        );
1182    }
1183
1184    #[test]
1185    fn test_edit() {
1186        let mut tree = SumTree::<u8>::new();
1187
1188        let removed = tree.edit(vec![Edit::Insert(1), Edit::Insert(2), Edit::Insert(0)], &());
1189        assert_eq!(tree.items(&()), vec![0, 1, 2]);
1190        assert_eq!(removed, Vec::<u8>::new());
1191        assert_eq!(tree.get(&0, &()), Some(&0));
1192        assert_eq!(tree.get(&1, &()), Some(&1));
1193        assert_eq!(tree.get(&2, &()), Some(&2));
1194        assert_eq!(tree.get(&4, &()), None);
1195
1196        let removed = tree.edit(vec![Edit::Insert(2), Edit::Insert(4), Edit::Remove(0)], &());
1197        assert_eq!(tree.items(&()), vec![1, 2, 4]);
1198        assert_eq!(removed, vec![0, 2]);
1199        assert_eq!(tree.get(&0, &()), None);
1200        assert_eq!(tree.get(&1, &()), Some(&1));
1201        assert_eq!(tree.get(&2, &()), Some(&2));
1202        assert_eq!(tree.get(&4, &()), Some(&4));
1203    }
1204
1205    #[derive(Clone, Default, Debug)]
1206    pub struct IntegersSummary {
1207        count: usize,
1208        sum: usize,
1209        contains_even: bool,
1210        max: u8,
1211    }
1212
1213    #[derive(Ord, PartialOrd, Default, Eq, PartialEq, Clone, Debug)]
1214    struct Count(usize);
1215
1216    #[derive(Ord, PartialOrd, Default, Eq, PartialEq, Clone, Debug)]
1217    struct Sum(usize);
1218
1219    impl Item for u8 {
1220        type Summary = IntegersSummary;
1221
1222        fn summary(&self) -> Self::Summary {
1223            IntegersSummary {
1224                count: 1,
1225                sum: *self as usize,
1226                contains_even: (*self & 1) == 0,
1227                max: *self,
1228            }
1229        }
1230    }
1231
1232    impl KeyedItem for u8 {
1233        type Key = u8;
1234
1235        fn key(&self) -> Self::Key {
1236            *self
1237        }
1238    }
1239
1240    impl Summary for IntegersSummary {
1241        type Context = ();
1242
1243        fn add_summary(&mut self, other: &Self, _: &()) {
1244            self.count += other.count;
1245            self.sum += other.sum;
1246            self.contains_even |= other.contains_even;
1247            self.max = cmp::max(self.max, other.max);
1248        }
1249    }
1250
1251    impl<'a> Dimension<'a, IntegersSummary> for u8 {
1252        fn add_summary(&mut self, summary: &IntegersSummary, _: &()) {
1253            *self = summary.max;
1254        }
1255    }
1256
1257    impl<'a> Dimension<'a, IntegersSummary> for Count {
1258        fn add_summary(&mut self, summary: &IntegersSummary, _: &()) {
1259            self.0 += summary.count;
1260        }
1261    }
1262
1263    impl<'a> SeekTarget<'a, IntegersSummary, IntegersSummary> for Count {
1264        fn cmp(&self, cursor_location: &IntegersSummary, _: &()) -> Ordering {
1265            self.0.cmp(&cursor_location.count)
1266        }
1267    }
1268
1269    impl<'a> Dimension<'a, IntegersSummary> for Sum {
1270        fn add_summary(&mut self, summary: &IntegersSummary, _: &()) {
1271            self.0 += summary.sum;
1272        }
1273    }
1274}