Product features · Width-threshold image selection

import math

def image_candidate(candidates, width, ratio):
    if type(width) is not int or not 1 <= width <= 10000 or type(ratio) not in (int, float) or not 0.25 <= ratio <= 8 or not math.isfinite(ratio):
        raise ValueError("image.viewport")
    if type(candidates) is not list or not 1 <= len(candidates) <= 64:
        raise ValueError("image.candidates")
    sizes, seen = [], set()
    for pair in candidates:
        if type(pair) not in (list, tuple) or len(pair) != 2:
            raise ValueError("image.pair")
        url, pixels = pair
        if type(url) is not str or not 1 <= len(url) <= 2048 or any(ord(c) < 32 or ord(c) == 127 for c in url):
            raise ValueError("image.url")
        if type(pixels) is not int or not 1 <= pixels <= 100000 or pixels in seen:
            raise ValueError("image.size")
        seen.add(pixels)
        sizes.append((pixels, url))
    sizes.sort()
    target = width*ratio
    return next((url for pixels, url in sizes if pixels >= target), sizes[-1][1])