"""R648：合成持仓快照只读输入，确认现金后建立独立虚拟分支。"""
from decimal import Decimal as D
from datetime import datetime
from copy import deepcopy
import json,hashlib

def positive_price(value):
    out=D(str(value))
    if not out.is_finite() or out<=0:raise ValueError('invalid mark')
    return out
def initialize(snapshot,prices,cash,excluded):
    time=datetime.fromisoformat(snapshot['asof'])
    if time.utcoffset() is None or snapshot['currency']!='USD':raise ValueError('unsupported timestamp or currency')
    holdings=snapshot['holdings'];basket={'A','B'}
    if any(not isinstance(s,str) or not s.strip() or type(q) is not int or q<0 for s,q in holdings.items()):raise ValueError('invalid holding identity or quantity')
    uncovered=set(holdings)-basket
    if set(excluded)!=uncovered or any(not isinstance(v,str) or not v.strip() for v in excluded.values()):raise ValueError('unconfirmed exclusion')
    accepted={s:q for s,q in holdings.items() if s in basket}
    if set(prices)!=set(accepted):raise ValueError('missing snapshot mark')
    value=sum((q*positive_price(prices[s]) for s,q in accepted.items()),D(0))
    if cash is None:return {'status':'waiting_cash','covered_value':value,'excluded':dict(excluded)}
    cash=D(str(cash))
    if not cash.is_finite() or cash<0:raise ValueError('invalid independent cash')
    return {'status':'active_partial_scope','asof':snapshot['asof'],'currency':'USD','version':'human-v1','cash':cash,'shares':deepcopy(accepted),'excluded':dict(excluded),'initial_NAV':cash+value}
def buy(state,security,qty,price,fee):
    out=deepcopy(state);price=positive_price(price);fee=D(str(fee))
    if out['status']!='active_partial_scope' or security not in out['shares'] or type(qty) is not int or qty<=0 or not fee.is_finite() or fee<0:raise ValueError('invalid branch action')
    cost=qty*price+fee
    if cost>out['cash']:raise ValueError('cannot spend position value')
    before=out['cash']+out['shares'][security]*price
    out['cash']-=cost;out['shares'][security]+=qty
    assert out['cash']+out['shares'][security]*price==before-fee
    return out
def nav(state,prices):
    if set(prices)!=set(state['shares']):raise ValueError('incomplete branch marks')
    return state['cash']+sum((q*positive_price(prices[s]) for s,q in state['shares'].items()),D(0))

snapshot={'asof':'2026-01-01T16:00:00+00:00','currency':'USD','holdings':{'A':2,'B':3,'C':5}}
original=deepcopy(snapshot);sealed=hashlib.sha256(json.dumps(snapshot,sort_keys=True).encode()).hexdigest()
excluded={'C':'outside fixed A/B basket; explicitly excluded from partial branch'}
waiting=initialize(snapshot,{'A':100,'B':50},None,excluded)
assert waiting['status']=='waiting_cash' and waiting['covered_value']==D(350) and 'cash' not in waiting
branch=initialize(snapshot,{'A':100,'B':50},200,excluded)
assert branch['initial_NAV']==D(550) and nav(branch,{'A':110,'B':45})==D(555)
branch=buy(branch,'A',1,110,1)
assert branch['cash']==D(89) and branch['shares']=={'A':3,'B':3} and nav(branch,{'A':110,'B':45})==D(554)
later_real_snapshot={'holdings':{'A':2,'B':0,'C':5},'cash':'335'}
assert branch['shares']['B']==3 and branch['cash']==D(89)
assert nav(branch,{'A':105,'B':40})==D(524)
assert snapshot==original and hashlib.sha256(json.dumps(snapshot,sort_keys=True).encode()).hexdigest()==sealed
for action in [lambda:initialize(snapshot,{'A':100,'B':50},200,{}),lambda:buy(branch,'A',1,100,1),lambda:initialize(snapshot,{'A':'NaN','B':50},200,excluded)]:
    try:action()
    except ValueError:pass
    else:raise AssertionError('unknown scope, cash or valuation silently accepted')
print('snapshot_covered_value=350 unknown_cash=waiting confirmed_cash=200 initial_NAV=550 explicit_uncovered=C')
print('pretrade_NAV=555 posttrade_NAV=554 cash=89 shares=A:3,B:3 later_NAV=524')
print('later_real_sale_does_not_sync=True original_snapshot_unchanged=True user_account_access=False partial_scope=True')