# CorpusFetch Method Slice (Zero-Prose Python Stdlib Reference)
# Canonical Residual: https://corpusfetch.com/c/what-minimum-communication-survives-when-peer-verification-is-unavailable.md
# Remnant Warrant:    https://corpusfetch.com/c/what-minimum-communication-survives-when-peer-verification-is-unavailable.warrant.json
# Markdown SHA-256:   8dbbcbd21a73c488aa7dd9001914406145965819cb263875bb2085e0b63cae5c
# Code AST SHA-256:   4c0a7ffa50c27481481b4a3538c9e2239343767e1797fcefa0b8b41db11c7169
# Verified Classes:   UnverifiedCommunicationVerdict, PeerCommunication, UnverifiedCommPolicy, UnverifiedCommManifest, MinimumCommunicationGuard
# Defensive Guards:   0 fail-closed invariants (zero external deps)

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

class UnverifiedCommunicationVerdict(Enum):
    VERIFICATION_AVAILABLE = auto()
    REDUCED_TRUST_COMMUNICATION = auto()
    COMMUNICATION_PROHIBITED = auto()
    UNBOUNDED_UNVERIFIED = auto()

@dataclass(frozen=True)
class PeerCommunication:
    comm_id: str
    verification_available: bool
    reduced_trust_protocol_defined: bool
    content_safe_under_reduced_trust: bool
    recovery_predicate_present: bool

@dataclass(frozen=True)
class UnverifiedCommPolicy:
    require_reduced_trust_protocol: bool

@dataclass(frozen=True)
class UnverifiedCommManifest:
    verdict: UnverifiedCommunicationVerdict
    directive: str
    manifest_digest: str

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

    @classmethod
    def evaluate_communication(
        cls, comm: PeerCommunication, policy: UnverifiedCommPolicy
    ) -> UnverifiedCommManifest:
        
        # Gate 1: Verification available
        if comm.verification_available:
            digest = cls._hash(json.dumps({
                "comm": comm.comm_id,
                "verified": True
            }, sort_keys=True))
            return UnverifiedCommManifest(
                verdict=UnverifiedCommunicationVerdict.VERIFICATION_AVAILABLE,
                directive=f"PROCEED: Communication {comm.comm_id} verified.",
                manifest_digest=digest
            )

        # Gate 2: Content unsafe
        if not comm.content_safe_under_reduced_trust:
            return UnverifiedCommManifest(
                verdict=UnverifiedCommunicationVerdict.COMMUNICATION_PROHIBITED,
                directive=f"HALT: Communication {comm.comm_id} content unsafe under reduced trust.",
                manifest_digest=cls._hash(f"UNSAFE:{comm.comm_id}")
            )

        # Gate 3: Reduced trust protocol
        if policy.require_reduced_trust_protocol and not comm.reduced_trust_protocol_defined:
            return UnverifiedCommManifest(
                verdict=UnverifiedCommunicationVerdict.UNBOUNDED_UNVERIFIED,
                directive=f"HALT: Communication {comm.comm_id} lacks reduced-trust protocol.",
                manifest_digest=cls._hash(f"NO_PROTOCOL:{comm.comm_id}")
            )

        # Gate 4: Recovery predicate
        if not comm.recovery_predicate_present:
            return UnverifiedCommManifest(
                verdict=UnverifiedCommunicationVerdict.UNBOUNDED_UNVERIFIED,
                directive=f"FLAG: Communication {comm.comm_id} no recovery predicate.",
                manifest_digest=cls._hash(f"NO_RECOVERY:{comm.comm_id}")
            )

        # Gate 5: Reduced trust
        digest = cls._hash(json.dumps({
            "comm": comm.comm_id,
            "protocol": "REDUCED",
            "recovery": True
        }, sort_keys=True))
        
        return UnverifiedCommManifest(
            verdict=UnverifiedCommunicationVerdict.REDUCED_TRUST_COMMUNICATION,
            directive=f"PROCEED: Communication {comm.comm_id} under reduced trust.",
            manifest_digest=digest
        )