from argparse import ArgumentParser
from pathlib import Path

import cv2 as cv


INTERPOLATION_METHODS = {
    "area": cv.INTER_AREA,
    "linear": cv.INTER_LINEAR,
    "cubic": cv.INTER_CUBIC,
    "nearest": cv.INTER_NEAREST,
}

INTERPOLATION_NAMES = {
    "area": "INTER_AREA",
    "linear": "INTER_LINEAR",
    "cubic": "INTER_CUBIC",
    "nearest": "INTER_NEAREST",
}


parser = ArgumentParser()
parser.add_argument("--input", default="input/scene.png", help="Source image")
parser.add_argument("--output", default="output/scene-resized.png", help="Resized output image")
parser.add_argument("--width", type=int, default=360, help="Output width in pixels")
parser.add_argument("--height", type=int, default=240, help="Output height in pixels")
parser.add_argument(
    "--interpolation",
    choices=INTERPOLATION_METHODS,
    default="area",
    help="Interpolation method: area for shrinking, linear or cubic for enlarging",
)
args = parser.parse_args()

if args.width <= 0 or args.height <= 0:
    raise SystemExit("width and height must be positive integers")

input_path = Path(args.input)
output_path = Path(args.output)

image = cv.imread(str(input_path), cv.IMREAD_COLOR)
if image is None:
    raise SystemExit(f"could not read input image: {input_path}")

source_height, source_width = image.shape[:2]
resized = cv.resize(
    image,
    (args.width, args.height),
    interpolation=INTERPOLATION_METHODS[args.interpolation],
)

output_path.parent.mkdir(parents=True, exist_ok=True)
if not cv.imwrite(str(output_path), resized):
    raise SystemExit(f"could not write output image: {output_path}")

written = cv.imread(str(output_path), cv.IMREAD_COLOR)
if written is None:
    raise SystemExit(f"could not read resized image: {output_path}")

written_height, written_width = written.shape[:2]
if (written_width, written_height) != (args.width, args.height):
    raise SystemExit(
        "resized image has unexpected dimensions: "
        f"expected={args.width}x{args.height}, "
        f"actual={written_width}x{written_height}"
    )

x_scale = args.width / source_width
y_scale = args.height / source_height

print(f"read: {input_path}")
print(f"source: {source_width}x{source_height}")
print(f"target: {args.width}x{args.height}")
print(f"scale: {x_scale:.3f}x{y_scale:.3f}")
print(f"interpolation: {args.interpolation} ({INTERPOLATION_NAMES[args.interpolation]})")
print(f"wrote: {output_path}")
print(f"verified: {written_width}x{written_height}")