"""外供PE目标价重建及顺序驱动桥；非PE方法与口径错配不硬算。"""
import json
from decimal import Decimal as D

old = {"symbol": "AAA", "year": 2027, "currency": "CNY", "basis": "diluted", "method": "PE",
       "target_horizon": "2027-12-31",
       "eps": D("1.00"), "multiple": D("20"), "reported_target": D("20.00")}
new = {**old, "eps": D("1.20"), "multiple": D("22"), "reported_target": D("26.40")}

def rebuild(row):
    if row["method"] != "PE":
        raise ValueError("unsupported_valuation_method")
    for field in ["eps", "multiple", "reported_target"]:
        if not row[field].is_finite():
            raise ValueError("nonfinite_valuation_input:"+field)
    if row["eps"] <= 0 or row["multiple"] <= 0:
        raise ValueError("nonpositive_pe_inputs")
    computed = row["eps"]*row["multiple"]
    residual = row["reported_target"]-computed
    return computed, residual

def bridge(before, after):
    for field in ["symbol", "year", "target_horizon", "currency", "basis"]:
        if before[field] != after[field]:
            raise ValueError("incompatible_"+field)
    old_target, old_residual = rebuild(before)
    new_target, new_residual = rebuild(after)
    earnings = (after["eps"]-before["eps"])*before["multiple"]
    multiple = after["eps"]*(after["multiple"]-before["multiple"])
    assert earnings+multiple == new_target-old_target
    return {"old_computed": str(old_target), "new_computed": str(new_target),
            "earnings_first_effect": str(earnings), "multiple_second_effect": str(multiple),
            "change": str(new_target-old_target), "reported_residual": str(new_residual),
            "reproduced": abs(old_residual) <= D("0.01") and abs(new_residual) <= D("0.01")}

result = bridge(old, new)
assert result["earnings_first_effect"] == "4.00" and result["multiple_second_effect"] == "2.40"
assert result["change"] == "6.40" and result["reproduced"] is True
unmatched = bridge(old, {**new, "reported_target": D("27.00")})
assert unmatched["reported_residual"] == "0.60" and not unmatched["reproduced"]
blocked = []
for invalid in [{**new, "method": "DCF"}, {**new, "year": 2028}, {**new, "currency": "HKD"}, {**new, "basis": "basic"}, {**new, "target_horizon": "2028-12-31"}]:
    try:
        bridge(old, invalid)
    except ValueError as exc:
        blocked.append(str(exc))
assert blocked == ["unsupported_valuation_method", "incompatible_year", "incompatible_currency", "incompatible_basis", "incompatible_target_horizon"]
reverse_multiple_first = old["eps"]*(new["multiple"]-old["multiple"])
reverse_earnings_second = (new["eps"]-old["eps"])*new["multiple"]
assert reverse_multiple_first == D("2.00") and reverse_earnings_second == D("4.40")
interaction = (new["eps"]-old["eps"])*(new["multiple"]-old["multiple"])
assert interaction == D("0.40")
for field in ["eps", "multiple", "reported_target"]:
    for token in ["NaN", "Infinity", "-Infinity"]:
        try:
            rebuild({**new, field: D(token)})
        except ValueError as exc:
            assert str(exc) == "nonfinite_valuation_input:"+field
        else:
            raise AssertionError("非有限估值输入必须阻断")
print(json.dumps({"bridge": result, "unmatched_reported_target": unmatched,
                  "reverse_order_effects": [str(reverse_multiple_first), str(reverse_earnings_second)],
                  "interaction": str(interaction), "blocked": blocked}, sort_keys=True))