Sample a string by real-valued scores

You are given:

• A list of strings texts (e.g., user comments), length n .
• A list of floating-point scores scores of length n , where each score can be any real value, including -∞ or +∞ .

Design an algorithm/function that randomly returns one string from texts such that the probability of returning texts[i] is proportional to the score distribution.

Define the sampling rule explicitly as follows:

• If all scores are finite, sample index i with probability

$p_i = \frac{e^{scores[i]}}{\sum_{j=0}^{n-1} e^{scores[j]}}\quad\text{(softmax)}.$

• If one or more scores are +∞ , return one of the +∞ items uniformly at random.
• If all scores are -∞ (so all weights are zero), return any item uniformly at random.

Requirements:

• Time complexity: O(n) per sample.
• Must be numerically stable for large/small scores.
• Clearly state how you handle corner cases (empty input, NaN scores if they appear, etc.).