f10_receipts.py

from f10_reference import Sig, Chain, Witness, verify_receipt, canon, GENESIS_SEED

class GossipClient:
    '''Collects receipts from roster witnesses per (chain_id, event_id),
    merges via gossip, reports conflict evidence without claiming completeness.'''
    def __init__(self, client_id):
        self.client_id = client_id
        self.receipts = {}   # (chain_id, event_id) -> list of receipts
        self.assurance = {}  # (chain_id, event_id) -> witness_key_id -> ok/absent
    def _verify(self, r, witness_pub, writer_registry):
        '''Verify writer sig over checkpoint, then witness sig over full signed writer-envelope.'''
        Sig('v', GENESIS_SEED).verify(canon(r['checkpoint']), r['writer_sig'],
                                     writer_registry[r['writer_key_id']])
        verify_receipt(r, witness_pub)
    def collect(self, chain_id, event_id, roster, writer_registry):
        for w, pub in roster:
            rs = w.query_all(chain_id, event_id)
            status = 'ok' if rs else 'absent'
            self.assurance.setdefault((chain_id, event_id), {})[w.sig.key_id] = status
            if rs:
                for r in rs:
                    self._verify(r, pub, writer_registry)
                self.merge(rs)
    def merge(self, receipts):
        for r in receipts:
            cp = r['checkpoint']
            k = (cp['chain_id'], cp['event_id'])
            bucket = self.receipts.setdefault(k, [])
            if not any(canon(x) == canon(r) for x in bucket):
                bucket.append(r)
    def conflict_report(self, chain_id, event_id, witness_pubs, writer_registry):
        '''Returns report; NEVER claims absence of conflict elsewhere.'''
        rs = self.receipts.get((chain_id, event_id), [])
        for r in rs:
            self._verify(r, witness_pubs[r['witness_key_id']], writer_registry)
        heads = set(r['checkpoint']['head_hash'] for r in rs)
        absent = sorted(k for k, a in self.assurance.get((chain_id, event_id), {}).items() if a == 'absent')
        if len(heads) > 1:
            return {'status': 'FORK_EVIDENCE', 'heads': sorted(heads), 'receipts': rs}
        return {'status': 'NO_CONFLICT_OBSERVED', 'heads': sorted(heads), 'absent_witnesses': absent,
                'note': 'no conflict observed; not a claim none exists'}

def gossip_merge(a, b):
    '''Merge two clients' receipt sets: durable fork evidence.'''
    for k, rs in b.receipts.items():
        a.merge(rs)
    for k, m in b.assurance.items():
        a.assurance.setdefault(k, {}).update(m)
    return a