#!/usr/bin/env python3

import argparse
import sys
from pathlib import Path
from typing import Optional

try:
    from PIL import Image
except ImportError:
    print(
        "Error: Pillow is not installed. Install it with 'pip install Pillow' or use the project venv.",
        file=sys.stderr,
    )
    sys.exit(1)


def to_bw_char(value: int, threshold: int, invert: bool) -> str:
    is_black = value < threshold
    if invert:
        is_black = not is_black
    return 'B' if is_black else 'W'


def convert_image(
    input_path: Path,
    output_path: Path,
    width: Optional[int],
    height: Optional[int],
    threshold: int,
    invert: bool,
) -> None:
    # Load image
    img = Image.open(input_path)
    # Convert to grayscale (luminance)
    img = img.convert('L')

    # Resize if requested
    if width is not None or height is not None:
        # Preserve aspect ratio if only one dimension is provided
        if width is not None and height is not None:
            target_size = (width, height)
        else:
            w, h = img.size
            if width is not None and height is None:
                height = round(h * (width / w))
            elif height is not None and width is None:
                width = round(w * (height / h))
            target_size = (width, height)
        img = img.resize(target_size, resample=Image.NEAREST)

    pixels = img.load()
    w, h = img.size

    lines = []
    for y in range(h):
        row_chars = []
        for x in range(w):
            row_chars.append(to_bw_char(pixels[x, y], threshold, invert))
        lines.append(''.join(row_chars))
    output_path.parent.mkdir(parents=True, exist_ok=True)
    output_path.write_text('\n'.join(lines), encoding='utf-8')


def parse_args() -> argparse.Namespace:
    p = argparse.ArgumentParser(
        description="Convert an image to bad_apple_frame.txt format (W=white, B=black)."
    )
    # Input aliases: --input/-i and --image
    p.add_argument(
        '--input', '-i', dest='input', type=Path, required=False,
        help='Path to input image (PNG, JPG, GIF, etc.)'
    )
    p.add_argument(
        '--image', dest='input', type=Path, required=False,
        help='Alias for --input'
    )
    # Output aliases: --output/-o and --out
    p.add_argument(
        '--output', '-o', dest='output', type=Path, required=False,
        help='Path to output text file (defaults to <image>_frame.txt)'
    )
    p.add_argument(
        '--out', dest='output', type=Path, required=False,
        help='Alias for --output'
    )
    p.add_argument('--width', type=int, help='Optional output width in pixels')
    p.add_argument('--height', type=int,
                   help='Optional output height in pixels')
    p.add_argument(
        '--threshold', type=int, default=128,
        help='Grayscale threshold 0..255 (default: 128)'
    )
    p.add_argument('--invert', action='store_true',
                   help='Invert mapping (B/W flipped)')
    args = p.parse_args()

    if args.input is None:
        p.error("--input/--image is required")

    if args.output is None:
        args.output = args.input.with_name(f"{args.input.stem}_frame.txt")

    return args


def main() -> None:
    args = parse_args()
    convert_image(
        input_path=args.input,
        output_path=args.output,
        width=args.width,
        height=args.height,
        threshold=max(0, min(255, args.threshold)),
        invert=args.invert,
    )


if __name__ == '__main__':
    main()