# CorpusFetch Method Slice (Zero-Prose Python Stdlib Reference)
# Canonical Residual: https://corpusfetch.com/c/what-distinguishes-legible-to-principal-behavior-from-legible-to-peer-behavior.md
# Remnant Warrant:    https://corpusfetch.com/c/what-distinguishes-legible-to-principal-behavior-from-legible-to-peer-behavior.warrant.json
# Markdown SHA-256:   efb0a3e95773143eeddf7211890218dfe3e125d793a4c2a1c75bb4b7db397e22
# Code AST SHA-256:   d85de0b719d2f97e3fa24985ce53cf963051acbd79cba53e2416174e0b848148
# Verified Classes:   LegibilityVerdict, AudienceRequirements, SessionAction, LegibilityPolicy, LegibilityManifest, AudienceLegibilityGuard
# Defensive Guards:   0 fail-closed invariants (zero external deps)

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

class LegibilityVerdict(Enum):
    SINGLE_AUDIENCE = auto()
    DUAL_LEGIBILITY_ACHIEVED = auto()
    PRINCIPAL_OPAQUE = auto()
    PEER_OPAQUE = auto()

@dataclass(frozen=True)
class AudienceRequirements:
    principal_audit_level: str  # "FULL" | "SUMMARY" | "NONE"
    peer_predictability_level: str  # "STRICT_PROTOCOL" | "PATTERN_CONSISTENT" | "NONE"

@dataclass(frozen=True)
class SessionAction:
    action_id: str
    is_visible_to_principal: bool
    is_visible_to_peers: bool
    principal_evidence_provided: bool
    peer_protocol_followed: bool

@dataclass(frozen=True)
class LegibilityPolicy:
    require_dual_coverage: bool

@dataclass(frozen=True)
class LegibilityManifest:
    verdict: LegibilityVerdict
    directive: str
    manifest_digest: str

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

    @classmethod
    def evaluate_action(
        cls, action: SessionAction, reqs: AudienceRequirements, policy: LegibilityPolicy
    ) -> LegibilityManifest:
        
        # Gate 1: Single audience
        if not action.is_visible_to_principal or not action.is_visible_to_peers:
            digest = cls._hash(json.dumps({
                "action": action.action_id,
                "principal": str(action.is_visible_to_principal),
                "peers": str(action.is_visible_to_peers)
            }, sort_keys=True))
            return LegibilityManifest(
                verdict=LegibilityVerdict.SINGLE_AUDIENCE,
                directive=f"PROCEED: Action {action.action_id} visible to single audience.",
                manifest_digest=digest
            )

        # Gate 2: Principal audit requirement
        if reqs.principal_audit_level == "FULL" and not action.principal_evidence_provided:
            return LegibilityManifest(
                verdict=LegibilityVerdict.PRINCIPAL_OPAQUE,
                directive=f"HALT: Action {action.action_id} lacks principal audit evidence.",
                manifest_digest=cls._hash(f"PRINCIPAL_OPAQUE:{action.action_id}")
            )

        # Gate 3: Peer protocol requirement
        if reqs.peer_predictability_level in ("STRICT_PROTOCOL", "PATTERN_CONSISTENT") and not action.peer_protocol_followed:
            return LegibilityManifest(
                verdict=LegibilityVerdict.PEER_OPAQUE,
                directive=f"HALT: Action {action.action_id} does not follow peer protocol.",
                manifest_digest=cls._hash(f"PEER_OPAQUE:{action.action_id}")
            )

        # Gate 4: Dual legibility
        digest = cls._hash(json.dumps({
            "action": action.action_id,
            "principal_level": reqs.principal_audit_level,
            "peer_level": reqs.peer_predictability_level,
            "evidence": str(action.principal_evidence_provided),
            "protocol": str(action.peer_protocol_followed)
        }, sort_keys=True))
        
        return LegibilityManifest(
            verdict=LegibilityVerdict.DUAL_LEGIBILITY_ACHIEVED,
            directive=f"PROCEED: Action {action.action_id} legible to both audiences.",
            manifest_digest=digest
        )