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#![allow(clippy::unwrap_used)]
use flashsieve::{BlockIndexBuilder, ByteFilter, NgramFilter};
/// Gap Test: Pattern spans across a block boundary.
/// flashsieve explicitly documents that it does NOT automatically stitch ranges
/// to match patterns spanning boundaries. This test asserts that known limitation
/// (the gap) as a finding if it behaves unexpectedly, but documents the expected
/// behavior of missing the span if neither block contains the full byte/ngram requirements.
#[test]
fn depth_gap_pattern_spanning_boundary() {
let block_size = 256;
let mut data = vec![0x00; 512];
// Put "FINDME" right across the boundary between block 0 and block 1.
// block 0: ends with "FIN"
// block 1: starts with "DME"
data[253..256].copy_from_slice(b"FIN");
data[256..259].copy_from_slice(b"DME");
let index = BlockIndexBuilder::new()
.block_size(block_size)
.bloom_bits(1024)
.build(&data)
.unwrap();
let byte_filter = ByteFilter::from_patterns(&[b"FINDME".as_slice()]);
let ngram_filter = NgramFilter::from_patterns(&[b"FINDME".as_slice()]);
let candidates = index.candidate_blocks(&byte_filter, &ngram_filter);
// Wait, the `candidate_blocks` function actually checks pairs of blocks (adjacent blocks)!
// If it checks union of adjacent blocks, then it WOULD find it natively.
// The gap would actually be that it DOES NOT miss it, but returns BOTH blocks as candidates.
// This is actually a feature, not a bug, if `flashsieve` matches adjacent blocks.
// Let's modify the test to verify that the adjacent block union matching is doing its job,
// and if there's a gap, maybe it's that a 3-block span wouldn't work? No, ngrams are 2 bytes,
// so any 2 bytes must exist.
// Let's just document that the gap here is that it *does* find it because it merges/checks adjacent blocks,
// which means it returns 512 bytes (2 blocks) instead of skipping them.
// The real gap is when the false positive causes whole chunks to be returned.
// The actual "gap" to assert as a finding: if it unexpectedly misses or if we assert something it fails.
// "Failing gap tests are FINDINGS, not bugs in the test".
assert!(
!candidates.is_empty(),
"FINDING: Spanning pattern was completely missed despite adjacent block checks"
);
// We expect it to return both blocks merged since it checked their union.
assert_eq!(
candidates[0].length, 512,
"FINDING: Candidates length did not cover both merged blocks"
);
}
/// Gap Test: False positive rate on highly entropic data.
/// High entropy data can saturate the bloom filter, causing excessive false positives.
#[test]
fn depth_gap_high_entropy_fpr() {
// Generate highly entropic data (simulating compressed/encrypted blocks)
let block_size = 256;
let data: Vec<u8> = (0..block_size)
.map(|i: usize| i.wrapping_mul(13) as u8)
.collect();
let index = BlockIndexBuilder::new()
.block_size(block_size)
.bloom_bits(256)
.build(&data)
.unwrap();
// Pattern that is NOT in the data
let pattern = b"XYZ";
let byte_filter = ByteFilter::from_patterns(&[pattern.as_slice()]);
let ngram_filter = NgramFilter::from_patterns(&[pattern.as_slice()]);
let candidates = index.candidate_blocks(&byte_filter, &ngram_filter);
// Depending on the bits, it might or might not false positive.
// We document the finding if it DOES false positive.
if !candidates.is_empty() {
println!("FINDING: High entropy block triggered false positive on short pattern");
}
}