"""Find IDFH interval period via auto-correlation of structural patterns."""
from __future__ import annotations
import sys
from pathlib import Path
from collections import Counter

REPO = Path(__file__).resolve().parents[1]
sys.path.insert(0, str(REPO))


def main():
    target = REPO / "tests/fixtures/THORDATA_example/THORDATA_example/UPMC Presby/UM13981/UM13981_20220805075441.IDFH"
    buf = target.read_bytes()
    body_start = 0xF96
    body_end   = 0x270C
    body = buf[body_start:body_end]
    print(f"body size: {len(body)} bytes (file {len(buf)} bytes)")

    # For each candidate interval size, count how many bytes at fixed offsets within
    # each interval are zero (consistent column-zero pattern indicates correct size).
    print()
    print("=== zero-column score by interval size (higher = more likely) ===")
    best = []
    for sz in range(16, 100):
        n = len(body) // sz
        if n < 30:
            continue
        # For each column position within an interval, count how many of n intervals have zero
        score = 0
        for col in range(sz):
            zeros = sum(1 for i in range(n) if body[i*sz + col] == 0)
            if zeros >= n * 0.9:
                score += 1
        best.append((score, sz, n))
    best.sort(reverse=True)
    for score, sz, n in best[:10]:
        print(f"  size={sz:3d}  n_intervals={n}  consistently-zero-cols={score}")


if __name__ == "__main__":
    main()