# -*- coding: utf-8 -*-
"""
log_decode.py — 将 K1 LOG.BIN（W25Q 日志分区镜像）解码为可读时间线

布局:
  [0x0000 .. 0x0FFF] header (magic K1LG ...)
  [0x1000 .. end]    文本环形区，行以 \\n 结束

用法:
  python log_decode.py LOG.BIN -o problem.log
  python log_decode.py LOG.BIN --write-off 1234 --wrap 1 -o problem.log
"""
from __future__ import annotations

import argparse
import struct

MAGIC = 0x4B314C47  # 'K1LG'
HDR_SIZE = 0x1000


def unpack_header(blob: bytes) -> dict:
    if len(blob) < 36:
        return {"valid": False}
    magic = struct.unpack_from("<I", blob, 0)[0]
    ver = struct.unpack_from("<H", blob, 4)[0]
    boot = struct.unpack_from("<I", blob, 8)[0]
    write_off = struct.unpack_from("<I", blob, 12)[0]
    wrap = struct.unpack_from("<I", blob, 16)[0]
    lines = struct.unpack_from("<I", blob, 20)[0]
    overflow = struct.unpack_from("<I", blob, 24)[0]
    seq = struct.unpack_from("<I", blob, 28)[0]
    return {
        "valid": magic == MAGIC,
        "magic": magic,
        "ver": ver,
        "boot_count": boot,
        "write_off": write_off,
        "wrap_count": wrap,
        "line_count": lines,
        "overflow": overflow,
        "seq": seq,
    }


def extract_text(data: bytes, write_off: int, wrapped: bool) -> str:
    """Linearize ring: if wrapped, [write_off..end) + [0..write_off); else [0..write_off)."""
    if not data:
        return ""
    if write_off > len(data):
        write_off = len(data)
    if wrapped and write_off < len(data):
        raw = data[write_off:] + data[:write_off]
    else:
        raw = data[:write_off] if write_off else data
    text = raw.decode("utf-8", errors="replace")
    text = text.replace("\xff", "")
    return text


def decode_file(bin_path: str, out_path: str, write_off=None, wrap_count=None) -> None:
    with open(bin_path, "rb") as f:
        blob = f.read()
    hdr = unpack_header(blob)
    data = blob[HDR_SIZE:] if len(blob) > HDR_SIZE else b""

    wo = write_off if write_off is not None else hdr.get("write_off", 0)
    wrap = wrap_count if wrap_count is not None else hdr.get("wrap_count", 0)

    text = extract_text(data, wo, wrap > 0)
    lines = [ln for ln in text.splitlines() if ln.strip()]

    with open(out_path, "w", encoding="utf-8", newline="\n") as f:
        f.write(
            f"# K1 log decode magic_ok={hdr.get('valid')} ver={hdr.get('ver')} "
            f"boot={hdr.get('boot_count')} write_off={wo} wrap={wrap} "
            f"line_count={hdr.get('line_count')} decoded_lines={len(lines)}\n"
        )
        for ln in lines:
            f.write(ln.rstrip("\r") + "\n")
    print(f"decoded {len(lines)} lines -> {out_path}")


def main():
    ap = argparse.ArgumentParser()
    ap.add_argument("bin")
    ap.add_argument("-o", "--out", default="problem.log")
    ap.add_argument("--write-off", type=int, default=None)
    ap.add_argument("--wrap", type=int, default=None)
    args = ap.parse_args()
    decode_file(args.bin, args.out, args.write_off, args.wrap)


if __name__ == "__main__":
    main()