a5 0.8.0

High-performance Rust implementation of the A5 hierarchical spatial indexing system
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173

// A5
// SPDX-License-Identifier: Apache-2.0
// Copyright (c) A5 contributors

use std::collections::BTreeSet;

use crate::core::face_adjacency::FACE_ADJACENCY;
use crate::core::origin::{get_origins, quintant_to_segment, segment_to_quintant};
use crate::core::serialization::{deserialize, serialize, FIRST_HILBERT_RESOLUTION};
use crate::core::utils::{A5Cell, Origin};
use crate::lattice::{anchor_to_triple, s_to_anchor, triple_parity, triple_to_anchor, Orientation};
use crate::traversal::lattice_boundary::{get_boundary_neighbors, BoundaryContext};
use crate::traversal::quintant_neighbors::find_quintant_neighbor_s;

/// Serialize a res 1 cell from origin and quintant.
fn serialize_res1(origin: &Origin, quintant: usize) -> u64 {
    let (segment, _) = quintant_to_segment(quintant, origin);
    serialize(&A5Cell {
        origin_id: origin.id,
        segment,
        s: 0,
        resolution: 1,
    })
    .unwrap()
}

/// Get neighbors of a resolution 0 cell (dodecahedron face).
fn get_res0_neighbors(origin: &Origin) -> Vec<u64> {
    let origins = get_origins();
    let mut neighbor_set = BTreeSet::new();
    for q in 0..5 {
        let (adjacent_face_id, _) = FACE_ADJACENCY[origin.id as usize][q];
        let adjacent_origin = &origins[adjacent_face_id as usize];
        if let Ok(cell_id) = serialize(&A5Cell {
            origin_id: adjacent_origin.id,
            segment: 0,
            s: 0,
            resolution: 0,
        }) {
            neighbor_set.insert(cell_id);
        }
    }
    neighbor_set.into_iter().collect()
}

/// Get neighbors of a resolution 1 cell (quintant).
fn get_res1_neighbors(origin: &Origin, segment: usize, edge_only: bool) -> Vec<u64> {
    let origins = get_origins();
    let (quintant, _) = segment_to_quintant(segment, origin);
    let mut neighbor_set = BTreeSet::new();

    // Left and right quintant on the same face (A, B)
    let left_q = (quintant + 4) % 5;
    let right_q = (quintant + 1) % 5;
    neighbor_set.insert(serialize_res1(origin, left_q));
    neighbor_set.insert(serialize_res1(origin, right_q));

    // Adjacent quintant on adjacent face (C)
    let (adjacent_face_id, adjacent_quintant) = FACE_ADJACENCY[origin.id as usize][quintant];
    let adjacent_origin = &origins[adjacent_face_id as usize];
    neighbor_set.insert(serialize_res1(adjacent_origin, adjacent_quintant));

    if edge_only {
        return neighbor_set.into_iter().collect();
    }

    // Remaining neighbors on face
    neighbor_set.insert(serialize_res1(origin, (quintant + 3) % 5));
    neighbor_set.insert(serialize_res1(origin, (quintant + 2) % 5));

    // Left & right quintant neighbors of C
    neighbor_set.insert(serialize_res1(adjacent_origin, (adjacent_quintant + 4) % 5));
    neighbor_set.insert(serialize_res1(adjacent_origin, (adjacent_quintant + 1) % 5));

    // Two neighbors each from adjacent faces of A & B
    let (left_adjacent_face_id, left_adjacent_quintant) =
        FACE_ADJACENCY[origin.id as usize][left_q];
    let left_adjacent_origin = &origins[left_adjacent_face_id as usize];
    neighbor_set.insert(serialize_res1(left_adjacent_origin, left_adjacent_quintant));
    neighbor_set.insert(serialize_res1(
        left_adjacent_origin,
        (left_adjacent_quintant + 4) % 5,
    ));

    let (right_adjacent_face_id, right_adjacent_quintant) =
        FACE_ADJACENCY[origin.id as usize][right_q];
    let right_adjacent_origin = &origins[right_adjacent_face_id as usize];
    neighbor_set.insert(serialize_res1(
        right_adjacent_origin,
        right_adjacent_quintant,
    ));
    neighbor_set.insert(serialize_res1(
        right_adjacent_origin,
        (right_adjacent_quintant + 1) % 5,
    ));

    neighbor_set.into_iter().collect()
}

/// Get all neighbors of a cell across quintant and face boundaries.
///
/// Within-quintant candidates are validated with `is_neighbor()` in uv space
/// (via `find_quintant_neighbor_s`). Cross-quintant, cross-face, apex, and
/// corner neighbors are emitted by the shared `get_boundary_neighbors` helper
/// using fixed delta tables — see `lattice_boundary.rs`.
///
/// `edge_only`: if true, return only edge-sharing neighbors (5 per cell).
/// Default false returns all neighbors including vertex-only neighbors (6-8 per cell).
pub fn get_global_cell_neighbors(cell_id: u64, edge_only: bool) -> Vec<u64> {
    let cell = match deserialize(cell_id) {
        Ok(c) => c,
        Err(_) => return Vec::new(),
    };
    let origins = get_origins();
    let origin = &origins[cell.origin_id as usize];
    let resolution = cell.resolution;

    if resolution == 0 {
        return get_res0_neighbors(origin);
    }
    if resolution == 1 {
        return get_res1_neighbors(origin, cell.segment, edge_only);
    }

    let hilbert_res = (resolution - FIRST_HILBERT_RESOLUTION + 1) as usize;
    let (source_quintant, source_orientation) = segment_to_quintant(cell.segment, origin);
    let anchor = s_to_anchor(cell.s, hilbert_res, source_orientation);

    // Triple coordinates are orientation-independent
    let triple = anchor_to_triple(&anchor);

    // Get uv anchor for is_neighbor validation (within-quintant)
    let uv_source_anchor = triple_to_anchor(&triple, hilbert_res, Orientation::UV);

    let mut neighbor_set: BTreeSet<u64> = BTreeSet::new();

    // --- Within-quintant: validated by is_neighbor() in uv space ---
    let within_neighbors = find_quintant_neighbor_s(
        &triple,
        uv_source_anchor.as_ref(),
        cell.s,
        hilbert_res,
        source_orientation,
        edge_only,
    );
    for neighbor_s in within_neighbors {
        if let Ok(neighbor_cell_id) = serialize(&A5Cell {
            origin_id: cell.origin_id,
            segment: cell.segment,
            s: neighbor_s,
            resolution,
        }) {
            neighbor_set.insert(neighbor_cell_id);
        }
    }

    // --- Cross-quintant / cross-face / apex / corner: shared lattice-boundary helper ---
    let ctx = BoundaryContext {
        triple,
        parity: triple_parity(&triple),
        source_quintant,
        origin,
        hilbert_res,
        max_s: 4u64.pow(hilbert_res as u32),
        max_row: (1i32 << hilbert_res) - 1,
        resolution,
    };
    for cell_id in get_boundary_neighbors(&ctx, edge_only, false) {
        neighbor_set.insert(cell_id);
    }

    neighbor_set.into_iter().collect()
}