"""Build the app icons from images/mtga-assistant-icon.png (the single source image).

Writes:
* src/mtga_assistant/icon.png: loaded at runtime for the window, taskbar and tray icon.
* images/mtga-assistant-icon.ico: the Windows .exe icon (PNG-compressed entries at the usual sizes).

Run after changing the source image:  uv run python packaging/make_icon.py
"""

import shutil
import struct
import sys
from pathlib import Path

from PySide6.QtCore import QBuffer, QByteArray, QIODevice, Qt
from PySide6.QtGui import QGuiApplication, QImage

SIZES = [16, 24, 32, 48, 64, 128, 256]
ROOT = Path(__file__).resolve().parent.parent
SOURCE = ROOT / "images" / "mtga-assistant-icon.png"


def png_at(img: QImage, size: int) -> bytes:
    scaled = img.scaled(size, size, Qt.AspectRatioMode.KeepAspectRatio, Qt.TransformationMode.SmoothTransformation)
    data = QByteArray()
    buf = QBuffer(data)
    buf.open(QIODevice.OpenModeFlag.WriteOnly)
    scaled.save(buf, "PNG")  # type: ignore[arg-type]  # PySide accepts str; its stubs say bytes
    return data.data()


def main() -> None:
    QGuiApplication(sys.argv[:1])
    img = QImage(str(SOURCE))
    if img.isNull():
        sys.exit(f"can't read {SOURCE}")
    pngs = [(size, png_at(img, size)) for size in SIZES]
    # ICONDIR header, one ICONDIRENTRY per image, then the PNG data.
    out = struct.pack("<HHH", 0, 1, len(pngs))
    offset = 6 + 16 * len(pngs)
    for size, png in pngs:
        dim = 0 if size >= 256 else size  # 0 means 256
        out += struct.pack("<BBBBHHII", dim, dim, 0, 0, 1, 32, len(png), offset)
        offset += len(png)
    out += b"".join(png for _, png in pngs)
    ico = SOURCE.with_suffix(".ico")
    ico.write_bytes(out)
    shutil.copyfile(SOURCE, ROOT / "src" / "mtga_assistant" / "icon.png")
    print(f"wrote {ico.relative_to(ROOT)} and src/mtga_assistant/icon.png from {SOURCE.relative_to(ROOT)}")


if __name__ == "__main__":
    main()