"""Walk chunks; auto-detect preamble length by finding first 10 NN."""
import sys
sys.path.insert(0, ".")
from analysis.load_bundle import load_bundle


def walk_chunks(body, start, max_NN=0x80):
    chunks = []
    i = start
    while i + 1 < len(body):
        if body[i] != 0x10:
            break
        NN = body[i + 1]
        if NN == 0 or NN > max_NN or NN % 4 != 0:
            break
        chunk_len = NN // 2 + 4
        if i + chunk_len > len(body):
            break
        data = bytes(body[i + 2 : i + 2 + NN // 2])
        trailer = bytes(body[i + 2 + NN // 2 : i + chunk_len])
        chunks.append((i, NN, data, trailer))
        i += chunk_len
    return chunks, i


def find_first_chunk_start(body):
    """Locate first byte that begins a `10 NN` chunk (NN ∈ multiples of 4, 4..0x7C)."""
    for i in range(20):
        if body[i] == 0x10 and body[i + 1] % 4 == 0 and 0 < body[i + 1] <= 0x7C:
            return i
    return -1


def main():
    for name in ("event-c", "event-d", "event-a", "event-b"):
        b = load_bundle(name)
        body = b.body
        start = find_first_chunk_start(body)
        chunks, end = walk_chunks(body, start)
        print(f"\n=== {name} ===  body={len(body)}  N_samples={len(b.samples['Tran'])}  start={start}")
        print(f"  chunks parsed: {len(chunks)}, walk ended at {end}")
        if chunks:
            print(f"  first 5 chunks: {[(c[0], c[1], c[3].hex()) for c in chunks[:5]]}")
            print(f"  last 5 chunks: {[(c[0], c[1], c[3].hex()) for c in chunks[-5:]]}")
            print(f"  bytes around end of walk: {body[end-4:end+12].hex(' ')}")
        else:
            print(f"  bytes at start: {body[start:start+16].hex(' ')}")


if __name__ == "__main__":
    main()