"""Independent check of the live ledger: pull the RNG blob out of two save files and
compute the word delta from the FILES, with no reference to the shim's numbers."""
import sys, os
sys.path.insert(0, os.path.expanduser('~/sots-re/verify/save-reader'))
import save_reader as sr

N, M = 624, 397
def twist(mt):
    mt = list(mt)
    for kk in range(N - M):
        y = (mt[kk] & 0x80000000) | (mt[kk+1] & 0x7fffffff)
        mt[kk] = mt[kk+M] ^ (y >> 1) ^ (0x9908b0df if y & 1 else 0)
    for kk in range(N - M, N - 1):
        y = (mt[kk] & 0x80000000) | (mt[kk+1] & 0x7fffffff)
        mt[kk] = mt[kk+(M-N)] ^ (y >> 1) ^ (0x9908b0df if y & 1 else 0)
    y = (mt[N-1] & 0x80000000) | (mt[0] & 0x7fffffff)
    mt[N-1] = mt[M-1] ^ (y >> 1) ^ (0x9908b0df if y & 1 else 0)
    return mt

def find_rng(node, out):
    name = getattr(node, 'name', None)
    if name == 'RNG':
        out.append(node)
    for c in getattr(node, 'children', []) or []:
        find_rng(c, out)

def rng_of(path):
    res = sr.read_save(path)
    hits = []
    find_rng(res.tree, hits)
    if not hits:
        raise SystemExit(f"no RNG frame in {path}")
    n = hits[0]
    raw = n.raw
    if not raw and n.children:
        raw = b"".join(c.raw for c in n.children)
    if not raw:
        raise SystemExit(f"RNG frame in {path} carries no bytes")
    return raw

def parse(raw):
    # the blob is mt[624] then left, little-endian; tolerate a leading/trailing frame byte
    for off in range(0, len(raw) - 2500 + 1):
        if len(raw) - off < 2500: continue
        mt = [int.from_bytes(raw[off+4*i:off+4*i+4], 'little') for i in range(N)]
        left = int.from_bytes(raw[off+2496:off+2500], 'little', signed=True)
        if 0 <= left <= N:
            return mt, left, off, len(raw)
    raise SystemExit(f"cannot parse RNG blob of {len(raw)} bytes")

a, b = sys.argv[1], sys.argv[2]
ra, rb = rng_of(a), rng_of(b)
ma, la, oa, na = parse(ra)
mb, lb, ob, nb = parse(rb)
print(f"{os.path.basename(a)}: blob {na} B, offset {oa}, left={la}")
print(f"{os.path.basename(b)}: blob {nb} B, offset {ob}, left={lb}")
cur, tw = ma, 0
while tw <= 64 and cur != mb:
    cur = twist(cur); tw += 1
if cur != mb:
    raise SystemExit("second block is not on the first block's chain within 64 twists")
words = 624*tw + (la - lb)
print(f"twists={tw}  words consumed between the two files = {words}")