"""按券商与固定财年配对预测修正，覆盖变动不冒充上调。"""
import json
from decimal import Decimal as D

year = 2027
old_meta = {"as_of": "2026-10-01", "source": "synthetic-snapshot-old", "year": year, "currency": "CNY", "basis": "diluted"}
new_meta = {**old_meta, "as_of": "2026-10-26", "source": "synthetic-snapshot-new"}
assert old_meta["as_of"] < new_meta["as_of"]
old = [("A", 2027, "1.00"), ("B", 2027, "2.00"), ("C", 2027, "-0.50"),
       ("D", 2027, "0.01"), ("G", 2027, "1.00"), ("E", 2026, "3.00")]
new = [("A", 2027, "1.20"), ("B", 2027, "1.80"), ("C", 2027, "-0.20"),
       ("D", 2027, "0.02"), ("E", 2027, "2.00"), ("F", 2027, "1.50")]

def snapshot(rows):
    selected = {}
    for broker, fiscal_year, value in rows:
        if fiscal_year != year:
            continue
        if broker in selected:
            raise ValueError("duplicate_broker_year")
        parsed = D(value)
        if not parsed.is_finite():
            raise ValueError("nonfinite_forecast_eps")
        selected[broker] = parsed
    return selected

before, after = snapshot(old), snapshot(new)
paired = []
for broker in sorted(before.keys() & after.keys()):
    prior, current = before[broker], after[broker]
    change = current-prior
    relative = change/prior if prior > D("0.05") else None
    paired.append({"broker": broker, "year": year, "old": str(prior), "new": str(current),
                   "change": str(change), "relative": str(relative) if relative is not None else None,
                   "relative_status": "valid" if relative is not None else "negative_or_near_zero_base"})
entered, exited = sorted(after.keys()-before.keys()), sorted(before.keys()-after.keys())
assert entered == ["E", "F"] and exited == ["G"]
assert [r["relative"] for r in paired] == ["0.2", "-0.1", None, None]
assert [r["change"] for r in paired] == ["0.20", "-0.20", "0.30", "0.01"]
mean_change = sum(D(r["change"]) for r in paired)/len(paired)
mean_magnitude = sum(abs(D(r["change"])) for r in paired)/len(paired)
up_pairs = sum(D(r["change"]) > 0 for r in paired)
down_pairs = sum(D(r["change"]) < 0 for r in paired)
assert mean_change == D("0.0775") and len(paired) == 4
assert mean_magnitude == D("0.1775") and (up_pairs, down_pairs) == (3, 1)
assert snapshot(list(reversed(old))) == before
for token in ["NaN", "Infinity", "-Infinity"]:
    try:
        snapshot([("A", 2027, token)])
    except ValueError as exc:
        assert str(exc) == "nonfinite_forecast_eps"
    else:
        raise AssertionError("非有限EPS不能进入预测快照")
print(json.dumps({"paired": paired, "entered_coverage": entered, "exited_coverage": exited,
                  "snapshots": [old_meta, new_meta],
                  "mean_signed_eps_change": str(mean_change), "mean_absolute_change_magnitude": str(mean_magnitude),
                  "up_pairs": up_pairs, "down_pairs": down_pairs,
                  "eligible_percentage_pairs": sum(r["relative"] is not None for r in paired)}, sort_keys=True))