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use std::{cmp::Ordering, collections::BinaryHeap};
use crate::GeoFloat;
use super::*;
pub(crate) struct Sweep<C: Cross> {
is_simple: bool,
events: BinaryHeap<Event<C::Scalar, IMSegment<C>>>,
active_segments: VecSet<Active<IMSegment<C>>>,
}
impl<C: Cross + Clone> Sweep<C> {
pub(crate) fn new<I>(iter: I, is_simple: bool) -> Self
where
I: IntoIterator<Item = C>,
{
let iter = iter.into_iter();
let size = {
let (min_size, max_size) = iter.size_hint();
max_size.unwrap_or(min_size)
};
let mut sweep = Sweep {
events: BinaryHeap::with_capacity(size),
active_segments: Default::default(),
is_simple,
};
for cr in iter {
IMSegment::create_segment(cr, None, None, |ev| sweep.events.push(ev));
}
sweep
}
/// Process the next event in heap.
///
/// Calls the callback unless the event is spurious.
#[inline]
pub(super) fn next_event<F>(&mut self, mut cb: F) -> Option<SweepPoint<C::Scalar>>
where
F: for<'a> FnMut(&'a IMSegment<C>, EventType),
{
self.events.pop().map(|event| {
let pt = event.point;
self.handle_event(event, &mut cb);
pt
})
}
/// Process two adjacent segments.
///
/// The first argument must be an active segment, and the other may or may not be.
/// Overlaps are chained from active -> other.
fn process_adjacent_segments(
&mut self,
active: Active<IMSegment<C>>,
other: &IMSegment<C>,
) -> AdjProcOutput<C::Scalar> {
// NOTE: The below logic is a loop instead of a
// conditional due to FP issues. Specifically,
// sometimes, two non-overlapping lines may become
// overlapping once broken at the point of intersection!
// EXAMPLE:
// let pt_7 = Coord::from((-32.57812499999999, 241.33427773853316));
// let pt_8 = Coord::from((-36.11348070978957, 237.7989220287436));
// let pt_13 = Coord::from((-25.507080078124993, 248.40532266040816));
// let pt_14 = Coord::from((-36.48784219165816, 237.424560546875));
// let pt_16 = Coord::from((-36.048578439260666, 237.8638242992725));
// 7-8 and 13-14 intersect at 16 such that 8-16 and 14-16 overlap !
// We handle this by intersecting twice if the segments overlap after adjustment.
let mut out = AdjProcOutput {
isec: None,
should_continue: true,
should_callback: false,
};
while let Some(isec) = other.geom().intersect_line_ordered(&active.geom()) {
trace!(
"Found intersection (LL):\n\tsegment1: {other:?}\n\tsegment2: {active:?}\n\tintersection: {isec:?}"
);
out.isec = Some(isec);
// 1. Split adj_segment, and extra splits to storage
let adj_overlap = active.adjust_one_segment(isec, |e| self.events.push(e));
// 2. Split segment, adding extra segments as needed.
let seg_overlap = other.adjust_one_segment(isec, |e| self.events.push(e));
assert_eq!(
adj_overlap.is_some(),
seg_overlap.is_some(),
"one of the intersecting segments had an overlap, but not the other!"
);
if let Some(adj_ovl) = adj_overlap {
let tgt = seg_overlap.unwrap();
trace!("setting overlap: {adj_ovl:?} -> {tgt:?}");
adj_ovl.chain_overlap(tgt.clone());
if &tgt == other {
// The whole event segment is now overlapping
// some other active segment.
//
// We do not need to continue iteration, but
// should callback if the left event of the
// now-parent has already been processed.
out.should_callback = adj_ovl.is_left_event_done();
out.should_continue = false;
}
// Overlaps are exact compute, so we do not need
// to re-run the loop.
return out;
}
if active.geom().partial_cmp(&other.geom()) == Some(Ordering::Equal) {
continue;
} else {
break;
}
}
out
}
fn handle_event<F>(&mut self, event: Event<C::Scalar, IMSegment<C>>, cb: &mut F) -> bool
where
F: for<'a> FnMut(&'a IMSegment<C>, EventType),
{
use EventType::*;
let segment = match IMSegment::is_correct(&event) {
false => return false,
_ => event.payload,
};
trace!(
"handling event: {pt:?} ({ty:?}) @ {seg:?}",
pt = event.point,
ty = event.ty,
seg = segment,
);
// let prev = self.active_segments.previous(&segment).cloned();
// let next = self.active_segments.next(&segment).cloned();
match &event.ty {
LineLeft => {
let mut should_add = true;
let mut insert_idx = self.active_segments.index_not_of(&segment);
if !self.is_simple {
for is_next in [true, false].into_iter() {
let active = if is_next {
if insert_idx < self.active_segments.len() {
self.active_segments[insert_idx].clone()
} else {
continue;
}
} else if insert_idx > 0 {
self.active_segments[insert_idx - 1].clone()
} else {
continue;
};
let AdjProcOutput {
isec,
should_continue,
should_callback,
} = self.process_adjacent_segments(active.clone(), &segment);
let isec = match isec {
Some(isec) => isec,
None => continue,
};
// A special case is if adj_segment was split, and the
// intersection is at the start of this segment. In this
// case, there is an right-end event in the heap, that
// needs to be handled before finishing up this event.
let handle_end_event = {
// Get first point of intersection
let int_pt = isec.left();
// Check its not first point of the adjusted, but is
// first point of current segment
int_pt != active.geom().left() && int_pt == segment.geom().left()
};
if handle_end_event {
let event = self.events.pop().unwrap();
let done = self.handle_event(event, cb);
debug_assert!(done, "special right-end event handling failed");
if !is_next {
// The prev-segment is now removed
insert_idx -= 1;
}
}
if !should_continue {
should_add = false;
if !should_callback {
return true;
}
break;
}
// let n = self.active_segments.len();
// if is_next && 1 + insert_idx < n {
// (insert_idx..n).find(|&idx| !self.active_segments.check_swap(idx));
// } else if !is_next && insert_idx > 1 {
// (0..insert_idx - 2)
// .rev()
// .find(|&idx| !self.active_segments.check_swap(idx));
// }
}
}
if should_add {
// Add current segment as active
// Safety: `self.segments` is a `Box` that is not
// de-allocated until `self` is dropped.
debug!("insert_active: {segment:?}");
// NOTE: we bravely track insert_idx as the active-list is adjusted
// self.active_segments.insert_active(segment.clone());
self.active_segments.insert_at(insert_idx, segment.clone());
}
let mut cb_seg = Some(segment);
while let Some(seg) = cb_seg {
cb(&seg, event.ty);
seg.set_left_event_done();
cb_seg = seg.overlap();
}
}
LineRight => {
// Safety: `self.segments` is a `Box` that is not
// de-allocated until `self` is dropped.
debug!("remove_active: {segment:?}");
let el_idx = self.active_segments.index_of(&segment);
let prev = (el_idx > 0).then(|| self.active_segments[el_idx - 1].clone());
let next = (1 + el_idx < self.active_segments.len())
.then(|| self.active_segments[el_idx + 1].clone());
assert_eq!(self.active_segments.remove_at(el_idx), segment);
let mut cb_seg = Some(segment);
while let Some(seg) = cb_seg {
cb(&seg, event.ty);
cb_seg = seg.overlap();
}
if !self.is_simple
&& let (Some(prev), Some(next)) = (prev, next)
{
let prev_geom = prev.geom();
let next_geom = next.geom();
if let Some(adj_intersection) = prev_geom.intersect_line_ordered(&next_geom) {
// 1. Split prev_segment, and extra splits to storage
let first = prev
.adjust_one_segment(adj_intersection, |e| self.events.push(e))
.is_none();
let second = next
.adjust_one_segment(adj_intersection, |e| self.events.push(e))
.is_none();
debug_assert!(
first && second,
"adjacent segments @ removal can't overlap!"
);
}
}
}
PointLeft => {
if !self.is_simple {
let insert_idx = self.active_segments.index_not_of(&segment);
let prev =
(insert_idx > 0).then(|| self.active_segments[insert_idx - 1].clone());
let next = (insert_idx < self.active_segments.len())
.then(|| self.active_segments[insert_idx].clone());
for adj_segment in prev.into_iter().chain(next.into_iter()) {
let geom = adj_segment.geom();
if let Some(adj_intersection) = segment.geom().intersect_line_ordered(&geom)
{
trace!(
"Found intersection (PL):\n\tsegment1: {segment:?}\n\tsegment2: {adj_segment:?}\n\tintersection: {adj_intersection:?}"
);
// 1. Split adj_segment, and extra splits to storage
let adj_overlap = adj_segment
.adjust_one_segment(adj_intersection, |e| self.events.push(e));
// Can't have overlap with a point
debug_assert!(adj_overlap.is_none());
}
}
}
// Points need not be active segments.
// Send the point-segment to callback.
cb(&segment, event.ty);
}
PointRight => {
// Nothing to do. We could remove this variant once we
// are confident about the logic.
}
}
true
}
#[inline]
pub fn peek_point(&self) -> Option<SweepPoint<C::Scalar>> {
self.events.peek().map(|e| e.point)
}
}
/// Internal enum to communicate result from `process_adjacent_segments`
struct AdjProcOutput<T: GeoFloat> {
isec: Option<LineOrPoint<T>>,
should_continue: bool,
should_callback: bool,
}