"""Internal demonstration: exact, deterministic ledger reconciliation."""
import re

def reconcile(entries):
    seen, balances = {}, {}
    for entry in entries:
        if not isinstance(entry, dict):
            raise ValueError('Each entry must be an object')
        key, account, amount = (entry.get(k) for k in ('id', 'account', 'amount'))
        if not all(isinstance(v, str) and v.strip() for v in (key, account, amount)):
            raise ValueError('id, account and amount must be non-empty strings')
        if not re.fullmatch(r'-?(?:0|[1-9]\d*)\.\d{2}', amount):
            raise ValueError('amount must be a decimal string with two places')
        cents = int(amount.replace('.', ''))
        value = (account, cents)
        if key in seen:
            if seen[key] != value:
                raise ValueError('Conflicting duplicate id: ' + key)
            continue
        seen[key] = value
        balances[account] = balances.get(account, 0) + cents
    def money(cents):
        return ('-' if cents < 0 else '') + str(abs(cents) // 100) + '.' + str(abs(cents) % 100).zfill(2)
    return {'accounts': [{'account': a, 'net': money(balances[a])} for a in sorted(balances)],
            'total': money(sum(balances.values())), 'unique_entries': len(seen)}