"""Deterministic chunk walker: each chunk = [10 NN][NN/2 bytes data][2 bytes trailer]."""
import sys
sys.path.insert(0, ".")
from analysis.load_bundle import load_bundle


def walk_chunks(body: bytes, start: int = 7):
    """Yield (offset, NN, data_bytes, trailer_bytes) tuples."""
    i = start
    while i + 1 < len(body):
        if body[i] != 0x10:
            break
        NN = body[i + 1]
        if NN == 0 or NN > 0x80 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])
        yield (i, NN, data, trailer)
        i += chunk_len


def main():
    for name in ("event-c", "event-d", "event-a", "event-b"):
        b = load_bundle(name)
        body = b.body
        chunks = list(walk_chunks(body))
        print(f"\n=== {name} ===  body={len(body)}  N_samples={len(b.samples['Tran'])}")
        print(f"  chunks parsed: {len(chunks)}")
        if chunks:
            last = chunks[-1]
            end_of_walk = last[0] + last[1] // 2 + 4
            print(f"  walk ended at offset {end_of_walk} (= {len(body) - end_of_walk} bytes from end)")
            # Stats
            total_data_bytes = sum(len(c[2]) for c in chunks)
            print(f"  total data bytes: {total_data_bytes}, total nibbles: {2*total_data_bytes}")
            if name in ("event-c", "event-d"):
                ratio = (2 * total_data_bytes) / (len(b.samples['Tran']) * 4)
                print(f"  nibbles per (sample × channel): {ratio:.3f}")
            # Sum of trailer second-byte
            trailer_sums = [c[3][-1] if c[3] else None for c in chunks]
            print(f"  first 10 chunks: {[(c[0], c[1], c[3].hex()) for c in chunks[:10]]}")
            # Print last 10 chunks (likely transition to trailer)
            print(f"  last 10 chunks: {[(c[0], c[1], c[3].hex()) for c in chunks[-10:]]}")


if __name__ == "__main__":
    main()