"""Regenerate font coverage after replacing the bundled NanumSquare WOFF2 files.

Requires fonttools[woff]. Normal app builds use the checked-in CSS, not Python.
Run: python3 scripts/generate-nanumsquare-css.py [--check]
"""

import argparse
import hashlib
import unicodedata
from pathlib import Path

from fontTools.pens.boundsPen import BoundsPen
from fontTools.ttLib import TTFont


ROOT = Path(__file__).resolve().parents[1]
FONTS = ROOT / "src/renderer/public/assets/fonts"
OUTPUT = ROOT / "src/renderer/src/styles/nanumSquare.css"
FACES = [(300, "NanumSquareL"), (400, "NanumSquare"), (700, "NanumSquareB"), (800, "NanumSquareEB")]
# Hangul fillers are intentionally invisible, like whitespace and controls.
FILLERS = {0x115F, 0x1160, 0x3164, 0xFFA0}


def coverage(font):
    glyphs = font.getGlyphSet()
    supported = []
    for code, name in sorted(font.getBestCmap().items()):
        pen = BoundsPen(glyphs)
        glyphs[name].draw(pen)
        intentional = chr(code).isspace() or unicodedata.category(chr(code)) in {"Cc", "Cf"} or code in FILLERS
        if pen.bounds is not None or intentional:
            supported.append(code)
    return supported


def unicode_ranges(codes):
    ranges = []
    start = end = codes[0]
    for code in codes[1:]:
        if code == end + 1:
            end = code
        else:
            ranges.append((start, end))
            start = end = code
    ranges.append((start, end))
    return [f"U+{start:X}" if start == end else f"U+{start:X}-{end:X}" for start, end in ranges]


def generate():
    sections = [
        "/* Generated by scripts/generate-nanumsquare-css.py. Do not edit manually.\n"
        " * Empty glyphs are excluded so the existing system-font fallback can render them.\n"
        " * Font binaries and visible glyphs are unchanged.\n */"
    ]
    for weight, name in FACES:
        file = FONTS / f"{name}.woff2"
        with TTFont(file) as font:
            ranges = unicode_ranges(coverage(font))
        lines = [", ".join(ranges[index:index + 10]) for index in range(0, len(ranges), 10)]
        sections.append(
            f"/* {file.name} sha256: {hashlib.sha256(file.read_bytes()).hexdigest()} */\n"
            "@font-face {\n"
            "  font-family: 'NanumSquare';\n"
            f"  src: url('/assets/fonts/{file.name}') format('woff2');\n"
            f"  font-weight: {weight};\n"
            "  font-style: normal;\n"
            "  font-display: swap;\n"
            "  unicode-range:\n    " + ",\n    ".join(lines) + ";\n}"
        )
    return "\n\n".join(sections) + "\n"


if __name__ == "__main__":
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument("--check", action="store_true")
    args = parser.parse_args()
    generated = generate()
    if args.check:
        if not OUTPUT.exists() or OUTPUT.read_text(encoding="utf-8") != generated:
            raise SystemExit("NanumSquare coverage CSS is stale; regenerate it")
        print("NanumSquare coverage matches all four font files")
    else:
        OUTPUT.parent.mkdir(parents=True, exist_ok=True)
        OUTPUT.write_text(generated, encoding="utf-8")
        print(f"Generated {OUTPUT.relative_to(ROOT)}")