"""Trace Tran sample-by-sample to find exactly where the codec drifts."""
from __future__ import annotations
import sys
from pathlib import Path

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

from analysis_idf.recon import TARGET, TXT, load_sidecar_samples


def s4(n: int) -> int:
    return n if n < 8 else n - 16


def i8(b: int) -> int:
    return b if b < 128 else b - 256


def main():
    buf = TARGET.read_bytes()
    sc = load_sidecar_samples(TXT)
    GEO_LSB = 0.0003
    sc_tran = [int(round(v / GEO_LSB)) for v in sc["Tran"]]

    body = buf[0x0f1f:]
    # Tran[0], Tran[1] from preamble
    t0 = int.from_bytes(body[3:5], "big", signed=True)
    t1 = int.from_bytes(body[5:7], "big", signed=True)
    print(f"preamble Tran[0]={t0}  Tran[1]={t1}  (sidecar: {sc_tran[0]}, {sc_tran[1]})")

    # Block 0: 10 f8 at body[7:9]
    print(f"block 0: tag {body[7]:02x} {body[8]:02x}")
    print(f"  block 0 first 10 data bytes: {body[9:19].hex()}")

    # Walk block 0 manually, comparing each sample
    cur = t1
    samples = [t0, t1]
    block_off = 7
    nn = body[8]
    print(f"  NN = {nn}")
    data = body[9 : 9 + nn // 2]
    for byi, byte in enumerate(data):
        for nib_idx, nib in enumerate(((byte >> 4) & 0xF, byte & 0xF)):
            cur += s4(nib)
            samples.append(cur)
            idx = len(samples) - 1
            if 0 <= idx < len(sc_tran):
                sc_v = sc_tran[idx]
                match = "✓" if sc_v == cur else "✗"
                if idx < 12 or 240 <= idx <= 260:
                    print(f"    idx {idx:3d}: nibble byte={byte:02x} nib={nib:x} delta={s4(nib):+d}  cur={cur:+d}  sc={sc_v:+d}  {match}")

    print(f"end of block 0: cur={cur}, len(samples)={len(samples)}, decoder expected 250 here")
    # Block 1: 20 28 starts at offset 9 + 124 = 133 from block_off=7
    block1_off = 9 + nn // 2
    print(f"block 1: tag {body[block1_off]:02x} {body[block1_off+1]:02x} (expecting 20 28)")
    nn1 = body[block1_off + 1]
    print(f"  block 1 NN = {nn1}")
    data1 = body[block1_off + 2 : block1_off + 2 + nn1]
    for byi, byte in enumerate(data1):
        cur += i8(byte)
        samples.append(cur)
        idx = len(samples) - 1
        if idx < len(sc_tran):
            sc_v = sc_tran[idx]
            match = "✓" if sc_v == cur else "✗"
            if 248 <= idx <= 295:
                print(f"    idx {idx:3d}: int8 byte={byte:02x} delta={i8(byte):+d}  cur={cur:+d}  sc={sc_v:+d}  {match}")


if __name__ == "__main__":
    main()