"""前缀不变检测及三种不同的未来数据依赖。"""
import json


def causal(xs):
    return [int(i >= 2 and x > sum(xs[i - 2:i + 1]) / 3)
            for i, x in enumerate(xs)]


def future_shift(xs):
    return [int(xs[i + 1] > x) if i + 1 < len(xs) else 0
            for i, x in enumerate(xs)]


def full_mean(xs):
    return [int(x > sum(xs) / len(xs)) for x in xs]


def centered(xs):
    return [int(x > sum(xs[max(0, i - 1):i + 2]) /
                len(xs[max(0, i - 1):i + 2])) for i, x in enumerate(xs)]


def repaired_future_shift(xs):
    return [int(i > 0 and x > xs[i - 1]) for i, x in enumerate(xs)]


def repaired_full_mean(xs):
    return [int(x > sum(xs[:i + 1]) / (i + 1)) for i, x in enumerate(xs)]


def repaired_centered(xs):
    return causal(xs)


def failures(fn, xs):
    result = []
    full = fn(xs)
    for cutoff in range(3, len(xs)):
        prefix = fn(xs[:cutoff])
        changed = [i for i in range(cutoff) if prefix[i] != full[i]]
        if changed:
            result.append({'cutoff': cutoff, 'rows': changed})
    return result


xs = [10, 10, 10, 12, 1000, 1, 500]
report = {fn.__name__: failures(fn, xs)
          for fn in [causal, future_shift, full_mean, centered]}
assert not report['causal']
assert all(report[name] for name in ['future_shift', 'full_mean', 'centered'])
mutated = xs[:4] + [13, 9, 8]
assert causal(xs)[:4] == causal(mutated)[:4]
assert full_mean(xs)[:4] != full_mean(mutated)[:4]
repairs = {fn.__name__: failures(fn, xs) for fn in
           [repaired_future_shift, repaired_full_mean, repaired_centered]}
assert all(not failed for failed in repairs.values())
for fn in [repaired_future_shift, repaired_full_mean, repaired_centered]:
    assert fn(xs)[:4] == fn(mutated)[:4]
print(json.dumps({'prefix_failures': report, 'future_mutation_causal_equal': True,
                  'future_mutation_global_equal': False, 'repaired_prefix_failures': repairs}))