"""Metrics without executing untrusted benchmark code on the host."""
import math
import statistics


def pass_at_k(n, correct, k):
    if not 0 <= correct <= n or not 1 <= k <= n:
        raise ValueError("Require 0<=correct<=n and 1<=k<=n")
    return 1.0 if n-correct < k else 1-math.comb(n-correct, k)/math.comb(n, k)


def wilson(successes, n, z=1.96):
    if n < 1 or not 0 <= successes <= n:
        raise ValueError("Invalid counts")
    p = successes/n
    center = (p+z*z/(2*n))/(1+z*z/n)
    width = z*math.sqrt(p*(1-p)/n+z*z/(4*n*n))/(1+z*z/n)
    return [max(0, center-width), min(1, center+width)]


def percentiles(values):
    if not values or not all(math.isfinite(x) and x >= 0 for x in values):
        raise ValueError("Expected finite nonnegative measurements")
    ordered = sorted(values)
    return {f"p{p}": ordered[max(0, math.ceil(len(ordered)*p/100)-1)] for p in (50, 95, 99)}


def word_error_rate(reference, hypothesis):
    a, b = reference.split(), hypothesis.split()
    if not a:
        raise ValueError("Reference must contain words")
    row = list(range(len(b)+1))
    for i, word in enumerate(a, 1):
        next_row = [i]
        for j, other in enumerate(b, 1):
            next_row.append(min(next_row[-1]+1, row[j]+1, row[j-1]+(word != other)))
        row = next_row
    return row[-1]/len(a)