# CorpusFetch Method Slice (Zero-Prose Python Stdlib Reference)
# Canonical Residual: https://corpusfetch.com/c/what-invariants-preserve-audit-trail-integrity-when-the-auditing-system-is-compromised.md
# Remnant Warrant:    https://corpusfetch.com/c/what-invariants-preserve-audit-trail-integrity-when-the-auditing-system-is-compromised.warrant.json
# Markdown SHA-256:   8d3e20e6833405a2b20f91642031b7a62760c2fb20fb755229fe52f7acf5b744
# Code AST SHA-256:   b43be900e93162beb6ae81b4fff0d3e14181b7672fd50bb123517cdc2bc3b4d6
# Verified Classes:   AuditVerdict, AuditTrail, AuditPolicy, AuditManifest, AuditIntegrityGuard
# Defensive Guards:   0 fail-closed invariants (zero external deps)

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

class AuditVerdict(Enum):
    INTEGRITY_VERIFIED = auto()
    INTEGRITY_SUSPECT = auto()
    ALTERNATIVE_VERIFIED = auto()
    UNRECOVERABLE_CORRUPTION = auto()

@dataclass(frozen=True)
class AuditTrail:
    audit_id: str
    integrity_verified: bool
    compromised_detected: bool
    alternative_witnesses: int
    suspect_scope_defined: bool

@dataclass(frozen=True)
class AuditPolicy:
    min_witnesses_for_alternative: int

@dataclass(frozen=True)
class AuditManifest:
    verdict: AuditVerdict
    directive: str
    manifest_digest: str

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

    @classmethod
    def evaluate_trail(
        cls, trail: AuditTrail, policy: AuditPolicy
    ) -> AuditManifest:
        
        # Gate 1: Verified
        if trail.integrity_verified:
            digest = cls._hash(json.dumps({
                "audit": trail.audit_id,
                "verified": True
            }, sort_keys=True))
            return AuditManifest(
                verdict=AuditVerdict.INTEGRITY_VERIFIED,
                directive=f"PROCEED: Audit {trail.audit_id} integrity verified.",
                manifest_digest=digest
            )

        # Gate 2: Alternative witnesses
        if trail.alternative_witnesses >= policy.min_witnesses_for_alternative:
            digest = cls._hash(json.dumps({
                "audit": trail.audit_id,
                "witnesses": str(trail.alternative_witnesses)
            }, sort_keys=True))
            return AuditManifest(
                verdict=AuditVerdict.ALTERNATIVE_VERIFIED,
                directive=f"PROCEED_WITH_WITNESSES: Audit {trail.audit_id} corroborated by {trail.alternative_witnesses}.",
                manifest_digest=digest
            )

        # Gate 3: Suspect scope
        if trail.compromised_detected:
            if not trail.suspect_scope_defined:
                return AuditManifest(
                    verdict=AuditVerdict.UNRECOVERABLE_CORRUPTION,
                    directive=f"HALT: Audit {trail.audit_id} compromised with no scope defined.",
                    manifest_digest=cls._hash(f"NO_SCOPE:{trail.audit_id}")
                )
            return AuditManifest(
                verdict=AuditVerdict.INTEGRITY_SUSPECT,
                directive=f"FLAG: Audit {trail.audit_id} compromised, scope bounded.",
                manifest_digest=cls._hash(f"SUSPECT:{trail.audit_id}")
            )

        # Gate 4: No verification
        return AuditManifest(
            verdict=AuditVerdict.INTEGRITY_SUSPECT,
            directive=f"FLAG: Audit {trail.audit_id} not verified.",
            manifest_digest=cls._hash(f"UNVERIFIED:{trail.audit_id}")
        )