import re
import logging
from nltk.stem import PorterStemmer
from collections import defaultdict
def _find_fts_matches(text, query, window_size=500):
logging.debug(f"_find_fts_matches called for text of length '{len(text)}' and query '{query}' and window_size '{window_size}'")
stemmer = PorterStemmer()
query_words = re.findall(r'\w+', query.lower())
query_stems = list(set(stemmer.stem(w) for w in query_words))
num_terms = len(query_stems)
# 1. Extract all "Candidate Hits" for any of the query stems
# We store them as: (start_pos, end_pos, stem)
candidates = []
for match in re.finditer(r'\w+', text):
stem = stemmer.stem(match.group().lower())
if stem in query_stems:
candidates.append({
'start': match.start(),
'end': match.end(),
'stem': stem
})
# 2. Sliding Window Logic
results = []
counts = defaultdict(int)
unique_stems_in_window = 0
left = 0
for right in range(len(candidates)):
# Add the right-most candidate to our current window
stem_r = candidates[right]['stem']
if counts[stem_r] == 0:
unique_stems_in_window += 1
counts[stem_r] += 1
# While the window contains ALL query stems, try to shrink it from the left
while unique_stems_in_window == num_terms:
# Calculate the current span
span_start = candidates[left]['start']
span_end = candidates[right]['end']
# If the span is within our maximum allowed character distance
if (span_end - span_start) <= window_size:
results.append((span_start, span_end))
# Shrink the window from the left to find a tighter match or move on
stem_l = candidates[left]['stem']
counts[stem_l] -= 1
if counts[stem_l] == 0:
unique_stems_in_window -= 1
left += 1
# 3. Clean up: Merge overlapping or adjacent results
if not results:
logging.debug("_find_fts_matches returning empty results")
return []
results.sort()
merged = [results[0]]
for current_start, current_end in results[1:]:
last_start, last_end = merged[-1]
# If the new match overlaps or is very close to the last one, merge them
if current_start <= last_end:
merged[-1] = (last_start, max(last_end, current_end))
else:
merged.append((current_start, current_end))
logging.debug(f"_find_fts_matches returning merged results of length {len(merged)}")
return merged
