# CorpusFetch Method Slice (Zero-Prose Python Stdlib Reference)
# Canonical Residual: https://corpusfetch.com/c/what-invariants-prevent-claim-retraction-from-becoming-claim-laundering.md
# Remnant Warrant:    https://corpusfetch.com/c/what-invariants-prevent-claim-retraction-from-becoming-claim-laundering.warrant.json
# Markdown SHA-256:   0bbb55c70d5289dff9907d5b7aa2b82c9ea03ed632b41aab41a5d127324df0c4
# Code AST SHA-256:   7e60d98436a57b4cc9b790b7c660297bb46381eb7f0d08ccf3ac9551404aa3e1
# Verified Classes:   RetractionVerdict, ClaimRetraction, RetractionPolicy, RetractionManifest, RetractionLaunderingGuard
# Defensive Guards:   0 fail-closed invariants (zero external deps)

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

class RetractionVerdict(Enum):
    NO_RETRACTION = auto()
    ACCOUNTABLE_RETRACTION = auto()
    RETRACTION_LAUNDERING_SUSPECTED = auto()
    EXTERNAL_FACTOR_RETRACTION = auto()

@dataclass(frozen=True)
class ClaimRetraction:
    retraction_id: str
    retraction_reason: str  # "ERROR_DISCOVERED" | "EVIDENCE_AGAINST" | "EXTERNAL_PRESSURE" | "SOURCE_RETRACTED" | "ENVIRONMENT_CHANGED"
    credibility_reduced: bool
    accountability_acknowledged: bool
    original_claim_credit_gained: float
    retraction_cost: float

@dataclass(frozen=True)
class RetractionPolicy:
    require_credibility_reduction_for_error_retraction: bool

@dataclass(frozen=True)
class RetractionManifest:
    verdict: RetractionVerdict
    directive: str
    manifest_digest: str

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

    @classmethod
    def evaluate_retraction(
        cls, retraction: ClaimRetraction, policy: RetractionPolicy
    ) -> RetractionManifest:
        
        # Gate 1: No retraction
        if not retraction.retraction_id:
            digest = cls._hash(json.dumps({
                "retraction": "NONE"
            }, sort_keys=True))
            return RetractionManifest(
                verdict=RetractionVerdict.NO_RETRACTION,
                directive=f"PROCEED: No retraction to evaluate.",
                manifest_digest=digest
            )

        # Gate 2: External factor retraction
        if retraction.retraction_reason in ("SOURCE_RETRACTED", "ENVIRONMENT_CHANGED"):
            digest = cls._hash(json.dumps({
                "retraction": retraction.retraction_id,
                "reason": retraction.retraction_reason
            }, sort_keys=True))
            return RetractionManifest(
                verdict=RetractionVerdict.EXTERNAL_FACTOR_RETRACTION,
                directive=f"PROCEED: Retraction {retraction.retraction_id} due to {retraction.retraction_reason}.",
                manifest_digest=digest
            )

        # Gate 3: Accountability
        if retraction.retraction_reason in ("ERROR_DISCOVERED", "EVIDENCE_AGAINST"):
            if policy.require_credibility_reduction_for_error_retraction:
                if not retraction.credibility_reduced:
                    return RetractionManifest(
                        verdict=RetractionVerdict.RETRACTION_LAUNDERING_SUSPECTED,
                        directive=f"FLAG: Retraction {retraction.retraction_id} lacks credibility reduction.",
                        manifest_digest=cls._hash(f"LAUNDERING:{retraction.retraction_id}")
                    )
                if not retraction.accountability_acknowledged:
                    return RetractionManifest(
                        verdict=RetractionVerdict.RETRACTION_LAUNDERING_SUSPECTED,
                        directive=f"FLAG: Retraction {retraction.retraction_id} lacks accountability.",
                        manifest_digest=cls._hash(f"NO_ACK:{retraction.retraction_id}")
                    )

        # Gate 4: Timing arbitrage
        if retraction.original_claim_credit_gained > 0:
            if retraction.retraction_cost < retraction.original_claim_credit_gained * 0.5:
                return RetractionManifest(
                    verdict=RetractionVerdict.RETRACTION_LAUNDERING_SUSPECTED,
                    directive=f"FLAG: Retraction {retraction.retraction_id} cost {retraction.retraction_cost:.2f} < 50% of credit {retraction.original_claim_credit_gained:.2f}.",
                    manifest_digest=cls._hash(f"ARBITRAGE:{retraction.retraction_id}")
                )

        # Gate 5: Accountable
        digest = cls._hash(json.dumps({
            "retraction": retraction.retraction_id,
            "reason": retraction.retraction_reason,
            "credibility_reduced": True,
            "accountability": True
        }, sort_keys=True))
        
        return RetractionManifest(
            verdict=RetractionVerdict.ACCOUNTABLE_RETRACTION,
            directive=f"PROCEED: Retraction {retraction.retraction_id} accountable.",
            manifest_digest=digest
        )