#!/usr/bin/env python3
"""
Generate Beidou_B1C_codes.h/.cc from ICD Weil parameters in Beidou_B1C_prn.h.

 -----------------------------------------------------------------------------

 GNSS-SDR is a Global Navigation Satellite System software-defined receiver.
 This file is part of GNSS-SDR.

 Copyright (C) 2010-2026  (see AUTHORS file for a list of contributors)
 SPDX-License-Identifier: GPL-3.0-or-later

 Author: Wenhao Ou, 2026. ouwh(at)mail2.sysu.edu.cn

 -----------------------------------------------------------------------------
"""

from __future__ import annotations

import re
from pathlib import Path

ROOT = Path(__file__).resolve().parents[2]
PRN_HEADER = ROOT / "src/core/system_parameters/Beidou_B1C_prn.h"
OUT_HEADER = ROOT / "src/core/system_parameters/Beidou_B1C_codes.h"
OUT_SOURCE = ROOT / "src/core/system_parameters/Beidou_B1C_codes.cc"


def extract(name: str, text: str) -> list[int]:
    match = re.search(rf"{name}\[63\]\s*=\s*\{{([^}}]+)\}}", text, re.S)
    if not match:
        raise RuntimeError(f"Could not parse {name}")
    return [int(x.strip()) for x in match.group(1).split(",") if x.strip()]


def legendre(n: int) -> list[int]:
    seq = [0] * n
    for x in range(1, n):
        seq[(x * x) % n] = 1
    return seq


def weil_code(L: list[int], weil_len: int, w: int, p: int, out_len: int) -> list[int]:
    W = [L[k] ^ L[(k + w) % weil_len] for k in range(weil_len)]
    return [W[(n + p - 1) % weil_len] for n in range(out_len)]


def chips_to_hex(chips: list[int]) -> str:
    out = ""
    for i in range(0, len(chips), 4):
        chunk = chips[i : i + 4]
        value = 0
        for bit in chunk:
            value = (value << 1) | bit
        while len(chunk) < 4:
            value <<= 1
            chunk.append(0)
        out += format(value, "X")
    return out


def chips_to_binstr(chips: list[int]) -> str:
    return "".join(str(c) for c in chips)


# Keep generated source under the CI long-line limit (512 chars).
# Match the historical 76-char fragment width used in Beidou_B1C_codes.h.
_CODE_LINE_WIDTH = 76


def emit_array_decl(name: str, rows: list[str]) -> str:
    return f"extern const char {name}[63][{len(rows[0]) + 1}];"


def emit_wrapped_string(row: str) -> list[str]:
    """Emit one array element as adjacent string literals, one chunk per line."""
    chunks = [row[i : i + _CODE_LINE_WIDTH] for i in range(0, len(row), _CODE_LINE_WIDTH)]
    if not chunks:
        chunks = [""]
    out: list[str] = []
    for idx, chunk in enumerate(chunks):
        suffix = "," if idx == len(chunks) - 1 else ""
        out.append(f'    "{chunk}"{suffix}')
    return out


def emit_array_def(name: str, rows: list[str]) -> str:
    lines = [f"const char {name}[63][{len(rows[0]) + 1}] = {{"]
    for row in rows:
        lines.extend(emit_wrapped_string(row))
    lines.append("};")
    return "\n".join(lines)


def main() -> None:
    text = PRN_HEADER.read_text(encoding="utf-8")
    data_w = extract("BEIDOU_B1C_DATA_PRN_W", text)
    data_p = extract("BEIDOU_B1C_DATA_PRN_P", text)
    pilot_w = extract("BEIDOU_B1C_PILOT_PRN_W", text)
    pilot_p = extract("BEIDOU_B1C_PILOT_PRN_P", text)
    sec_w = extract("BEIDOU_B1C_PILOT_SECONDARY_W", text)
    sec_p = extract("BEIDOU_B1C_PILOT_SECONDARY_P", text)

    L10243 = legendre(10243)
    L3607 = legendre(3607)

    data_hex = [
        chips_to_hex(weil_code(L10243, 10243, data_w[i], data_p[i], 10230)) for i in range(63)
    ]
    pilot_hex = [
        chips_to_hex(weil_code(L10243, 10243, pilot_w[i], pilot_p[i], 10230)) for i in range(63)
    ]
    sec_bin = [chips_to_binstr(weil_code(L3607, 3607, sec_w[i], sec_p[i], 1800)) for i in range(63)]

    expected = "101011111111011001001110"
    assert "".join(str(b) for b in weil_code(L10243, 10243, data_w[0], data_p[0], 10230)[:24]) == expected

    script_name = Path(__file__).name
    header = f"""/*!
 * \\file Beidou_B1C_codes.h
 * \\brief Precomputed BeiDou B1C primary and secondary codes (declarations)
 * \\author Wenhao Ou, 2026. ouwh(at)mail2.sysu.edu.cn
 *
 * Auto-generated by {script_name}. Do not edit manually.
 * Definitions live in Beidou_B1C_codes.cc.
 *
 * -----------------------------------------------------------------------------
 *
 * GNSS-SDR is a Global Navigation Satellite System software-defined receiver.
 * This file is part of GNSS-SDR.
 *
 * Copyright (C) 2010-2026  (see AUTHORS file for a list of contributors)
 * SPDX-License-Identifier: GPL-3.0-or-later
 *
 * -----------------------------------------------------------------------------
 */
#ifndef GNSS_SDR_BEIDOU_B1C_CODES_H
#define GNSS_SDR_BEIDOU_B1C_CODES_H

#include <cstddef>

constexpr size_t BEIDOU_B1C_PRIMARY_CODE_STR_LENGTH = 2558;
constexpr size_t BEIDOU_B1C_PILOT_SECONDARY_CODE_STR_LENGTH = 1800;

{emit_array_decl("BEIDOU_B1C_DATA_PRIMARY_CODE", data_hex)}

{emit_array_decl("BEIDOU_B1C_PILOT_PRIMARY_CODE", pilot_hex)}

{emit_array_decl("BEIDOU_B1C_PILOT_SECONDARY_CODE", sec_bin)}

#endif
"""

    source = f"""/*!
 * \\file Beidou_B1C_codes.cc
 * \\brief Precomputed BeiDou B1C primary and secondary codes
 * \\author Wenhao Ou, 2026. ouwh(at)mail2.sysu.edu.cn
 *
 * Auto-generated by {script_name}. Do not edit manually.
 *
 * -----------------------------------------------------------------------------
 *
 * GNSS-SDR is a Global Navigation Satellite System software-defined receiver.
 * This file is part of GNSS-SDR.
 *
 * Copyright (C) 2010-2026  (see AUTHORS file for a list of contributors)
 * SPDX-License-Identifier: GPL-3.0-or-later
 *
 * -----------------------------------------------------------------------------
 */
#include "Beidou_B1C_codes.h"

{emit_array_def("BEIDOU_B1C_DATA_PRIMARY_CODE", data_hex)}

{emit_array_def("BEIDOU_B1C_PILOT_PRIMARY_CODE", pilot_hex)}

{emit_array_def("BEIDOU_B1C_PILOT_SECONDARY_CODE", sec_bin)}
"""

    OUT_HEADER.write_text(header, encoding="utf-8")
    OUT_SOURCE.write_text(source, encoding="utf-8")
    print(f"Wrote {OUT_HEADER} ({len(header)} bytes)")
    print(f"Wrote {OUT_SOURCE} ({len(source)} bytes)")


if __name__ == "__main__":
    main()