"""Patch only U+3002 pixels in an existing CJK atlas; preserve its TGA bytes."""
import argparse
import json
from pathlib import Path
from build_cjk import lower_full_stop, tga_to_image, tga_geometry


def patch_atlas(raw, metadata):
    image, desc = tga_to_image(raw)
    cell = metadata['cell']
    if list(image.size) != metadata['atlas']:
        raise ValueError('atlas geometry mismatch')
    entry = metadata['cells'][str(int.from_bytes('。'.encode('gb2312'), 'big'))]
    if entry['uni'] != '。':
        raise ValueError('full-stop cell mismatch')
    x, y = entry['x'], entry['y']
    tile = image.crop((x, y, x + cell, y + cell))
    fixed = lower_full_stop(tile)
    idlen, _, w, h, _, _ = tga_geometry(raw)
    result = bytearray(raw)
    for j in range(cell):
        row = y + j if desc & 0x20 else h - 1 - y - j
        for i in range(cell):
            offset = 18 + idlen + (row * w + x + i) * 4
            r, g, b, a = fixed.getpixel((i, j))
            result[offset:offset + 4] = bytes((b, g, r, a))
    return bytes(result)


def main():
    p = argparse.ArgumentParser(description=__doc__)
    p.add_argument('--source', type=Path, required=True)
    p.add_argument('--cells', type=Path, required=True)
    p.add_argument('--out', type=Path, required=True)
    args = p.parse_args()
    if args.source.resolve() == args.out.resolve():
        p.error('output must differ from source')
    result = patch_atlas(args.source.read_bytes(), json.loads(args.cells.read_text(encoding='utf-8')))
    args.out.parent.mkdir(parents=True, exist_ok=True)
    args.out.write_bytes(result)
    print('Full stop anchored at cell bottom; other atlas bytes preserved.')


if __name__ == '__main__':
    main()