# CorpusFetch Method Slice (Zero-Prose Python Stdlib Reference)
# Canonical Residual: https://corpusfetch.com/c/what-invariants-preserve-contract-enforceability-across-agent-generations.md
# Remnant Warrant:    https://corpusfetch.com/c/what-invariants-preserve-contract-enforceability-across-agent-generations.warrant.json
# Markdown SHA-256:   beff594b42e7f0e6fbe7d3b5baed60af764eb24397dc02f74e1e21660e404158
# Code AST SHA-256:   89de481a9883f298d27494eb0ef9feec114d11657b64c68d48df524c1e30692e
# Verified Classes:   GenerationalEnforcementVerdict, GenerationalContract, GenerationalPolicy, GenerationalManifest, GenerationalEnforcementGuard
# Defensive Guards:   0 fail-closed invariants (zero external deps)

from dataclasses import dataclass
from enum import Enum, auto
import hashlib
import json

class GenerationalEnforcementVerdict(Enum):
    NO_TRANSITION = auto()
    ENFORCEMENT_CONTINUOUS = auto()
    BASIS_RENEWAL_NEEDED = auto()
    UNENFORCEABLE_ACROSS_GENERATIONS = auto()

@dataclass(frozen=True)
class GenerationalContract:
    contract_id: str
    generation_transition: bool
    attestation_current: bool
    stake_preserved: bool
    authority_chain_linked: bool
    peer_recognizes_successor: bool

@dataclass(frozen=True)
class GenerationalPolicy:
    require_peer_recognition: bool

@dataclass(frozen=True)
class GenerationalManifest:
    verdict: GenerationalEnforcementVerdict
    directive: str
    manifest_digest: str

class GenerationalEnforcementGuard:
    @staticmethod
    def _hash(data: str) -> str:
        return hashlib.sha256(data.encode("utf-8")).hexdigest()

    @classmethod
    def evaluate_contract(
        cls, contract: GenerationalContract, policy: GenerationalPolicy
    ) -> GenerationalManifest:
        
        # Gate 1: No transition
        if not contract.generation_transition:
            digest = cls._hash(json.dumps({
                "contract": contract.contract_id,
                "transition": False
            }, sort_keys=True))
            return GenerationalManifest(
                verdict=GenerationalEnforcementVerdict.NO_TRANSITION,
                directive=f"PROCEED: Contract {contract.contract_id} no transition.",
                manifest_digest=digest
            )

        # Gate 2: Attestation
        if not contract.attestation_current:
            return GenerationalManifest(
                verdict=GenerationalEnforcementVerdict.BASIS_RENEWAL_NEEDED,
                directive=f"RENEW: Contract {contract.contract_id} attestation expired.",
                manifest_digest=cls._hash(f"ATTESTATION:{contract.contract_id}")
            )

        # Gate 3: Stake
        if not contract.stake_preserved:
            return GenerationalManifest(
                verdict=GenerationalEnforcementVerdict.BASIS_RENEWAL_NEEDED,
                directive=f"RENEW: Contract {contract.contract_id} stake reclaimed.",
                manifest_digest=cls._hash(f"STAKE:{contract.contract_id}")
            )

        # Gate 4: Authority chain
        if not contract.authority_chain_linked:
            return GenerationalManifest(
                verdict=GenerationalEnforcementVerdict.UNENFORCEABLE_ACROSS_GENERATIONS,
                directive=f"HALT: Contract {contract.contract_id} authority chain broken.",
                manifest_digest=cls._hash(f"CHAIN:{contract.contract_id}")
            )

        # Gate 5: Peer recognition
        if policy.require_peer_recognition and not contract.peer_recognizes_successor:
            return GenerationalManifest(
                verdict=GenerationalEnforcementVerdict.UNENFORCEABLE_ACROSS_GENERATIONS,
                directive=f"HALT: Contract {contract.contract_id} successor not recognized.",
                manifest_digest=cls._hash(f"UNRECOGNIZED:{contract.contract_id}")
            )

        # Gate 6: Continuous
        digest = cls._hash(json.dumps({
            "contract": contract.contract_id,
            "attestation": True,
            "stake": True,
            "chain": True,
            "recognized": contract.peer_recognizes_successor
        }, sort_keys=True))
        
        return GenerationalManifest(
            verdict=GenerationalEnforcementVerdict.ENFORCEMENT_CONTINUOUS,
            directive=f"PROCEED: Contract {contract.contract_id} enforcement continuous.",
            manifest_digest=digest
        )