#!/usr/bin/env python3
"""
optimize_web_resources.py - Resize PNG images for the web build.

Copies <src> to <dst>/resources/, then downscales all PNG files:
  - resources/w/ui/img/**  -> 1/8 original size
  - all other PNGs         -> 1/4 original size

Files listed in EXCEPTIONS are copied unchanged.

Usage (manual):
    python optimize_web_resources.py [--src resources] [--dst web_resources]

Usage (CMake):
    ${Python3_EXECUTABLE} optimize_web_resources.py --src <abs_src> --dst <abs_dst>
"""

import argparse
import os
import shutil

try:
    from PIL import Image
except ImportError:
    raise SystemExit("Pillow is required: pip install Pillow")

# Paths relative to the resources directory — these files are never resized.
EXCEPTIONS = {
    "loading.png",
    "black.png",
}

# Path prefixes (relative to resources root, forward-slash) that get 8x reduction.
HIGH_REDUCTION_PREFIXES = (
    "w/ui/img",
)


def _resize_factor(rel: str) -> int:
    norm = rel.replace("\\", "/")
    for prefix in HIGH_REDUCTION_PREFIXES:
        if norm.startswith(prefix):
            return 8
    return 4


def _next_pot(n: int) -> int:
    if n < 1:
        return 1
    p = 1
    while p < n:
        p <<= 1
    return p


def optimize(src_dir: str, dst_parent: str) -> None:
    src_dir = os.path.abspath(src_dir)
    dst_resources = os.path.join(os.path.abspath(dst_parent), "resources")

    print(f"Copying {src_dir} -> {dst_resources}")
    if os.path.exists(dst_resources):
        shutil.rmtree(dst_resources)
    shutil.copytree(src_dir, dst_resources)

    total = 0
    for root, _dirs, files in os.walk(dst_resources):
        for filename in files:
            if not filename.lower().endswith(".png"):
                continue

            full_path = os.path.join(root, filename)
            rel = os.path.relpath(full_path, dst_resources).replace("\\", "/")

            if rel in EXCEPTIONS:
                print(f"  skip (exception): {rel}")
                continue

            factor = _resize_factor(rel)

            with Image.open(full_path) as img:
                orig_w, orig_h = img.size
                new_w = _next_pot(max(1, orig_w // factor))
                new_h = _next_pot(max(1, orig_h // factor))
                resized = img.resize((new_w, new_h), Image.LANCZOS)
                resized.save(full_path)

            print(f"  {rel}: {orig_w}x{orig_h} -> {new_w}x{new_h} (/{factor} + POT)")
            total += 1

    print(f"Done. Resized {total} PNG file(s).")


if __name__ == "__main__":
    parser = argparse.ArgumentParser(description="Optimize PNG images for web build")
    parser.add_argument("--src", default="resources",
                        help="Source resources directory (default: resources)")
    parser.add_argument("--dst", default="web_resources",
                        help="Destination parent directory; will contain a 'resources' subdir "
                             "(default: web_resources)")
    args = parser.parse_args()
    optimize(args.src, args.dst)