# SPDX-License-Identifier: GPL-2.0-only
#!/usr/bin/env python3
"""Generate NSS-compatible BMP Unicode case tables from UnicodeData.txt.

The generated C file exports the NSS symbol names expected by the imported
Unicode helpers:

    unicode_t NSSUniToLower[65536]
    unicode_t NSSUniToUpper[65536]

Only single-code-point BMP mappings fit into these NSS tables. Full Unicode
case mappings and locale-sensitive SpecialCasing.txt entries are intentionally
not encoded here.
"""
from __future__ import annotations

import argparse
from pathlib import Path

BMP_SIZE = 0x10000


def parse_unicode_data(path: Path) -> tuple[list[int], list[int], dict[str, int]]:
    lower = list(range(BMP_SIZE))
    upper = list(range(BMP_SIZE))
    stats = {
        "records": 0,
        "lower_mappings": 0,
        "upper_mappings": 0,
        "non_bmp_skipped": 0,
    }

    with path.open("r", encoding="utf-8") as f:
        for line in f:
            line = line.strip()
            if not line or line.startswith("#"):
                continue
            fields = line.split(";")
            if len(fields) < 15:
                raise ValueError(f"Malformed UnicodeData line: {line!r}")
            cp = int(fields[0], 16)
            stats["records"] += 1
            if cp >= BMP_SIZE:
                stats["non_bmp_skipped"] += 1
                continue

            upper_field = fields[12]
            lower_field = fields[13]

            if upper_field:
                target = int(upper_field, 16)
                if target < BMP_SIZE:
                    upper[cp] = target
                    stats["upper_mappings"] += 1
            if lower_field:
                target = int(lower_field, 16)
                if target < BMP_SIZE:
                    lower[cp] = target
                    stats["lower_mappings"] += 1

    return lower, upper, stats


def emit_array(out, c_type: str, name: str, values: list[int]) -> None:
    out.write(f"{c_type} {name}[65536] = {{\n")
    for base in range(0, BMP_SIZE, 8):
        chunk = values[base:base + 8]
        text = ", ".join(f"0x{value:04X}" for value in chunk)
        out.write(f"\t{text}")
        if base + 8 < BMP_SIZE:
            out.write(",")
        out.write(f"\t/* 0x{base:04X} */\n")
    out.write("};\n")


def generate(ucd_dir: Path, output: Path, unicode_version: str) -> None:
    unicode_data = ucd_dir / "UnicodeData.txt"
    if not unicode_data.exists():
        raise FileNotFoundError(unicode_data)

    lower, upper, stats = parse_unicode_data(unicode_data)
    output.parent.mkdir(parents=True, exist_ok=True)
    with output.open("w", encoding="utf-8", newline="\n") as out:
        out.write("/*\n")
        out.write(" * Generated by scripts/gen_unicode_tables.py.\n")
        out.write(f" * Source: Unicode Character Database {unicode_version}.\n")
        out.write(" * Input: UCD/UnicodeData.txt simple uppercase/lowercase mappings.\n")
        out.write(" *\n")
        out.write(" * This file intentionally does not copy Novell NSS unitables/*.tab.\n")
        out.write(" * It exports NSS-compatible symbol names from Unicode UCD data.\n")
        out.write(" *\n")
        out.write(" * Only single-code-point BMP mappings fit these NSS tables. Full,\n")
        out.write(" * multi-code-point, and locale-sensitive mappings from SpecialCasing.txt\n")
        out.write(" * do not fit unicode_t[65536] tables and are not emitted here.\n")
        out.write(" */\n")
        out.write("#include <xUnicode.h>\n\n")
        out.write(f"/* UnicodeData records: {stats['records']}; non-BMP skipped: {stats['non_bmp_skipped']}. */\n")
        out.write(f"/* Simple BMP lower mappings: {stats['lower_mappings']}; upper mappings: {stats['upper_mappings']}. */\n\n")
        emit_array(out, "unicode_t", "NSSUniToLower", lower)
        out.write("\n")
        emit_array(out, "unicode_t", "NSSUniToUpper", upper)


def main() -> None:
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument("--ucd-dir", default="UCD", type=Path)
    parser.add_argument("--output", default="TAB/unicodeTables.c", type=Path)
    parser.add_argument("--unicode-version", default="17.0.0")
    args = parser.parse_args()
    generate(args.ucd_dir, args.output, args.unicode_version)


if __name__ == "__main__":
    main()