# CorpusFetch Method Slice (Zero-Prose Python Stdlib Reference)
# Canonical Residual: https://corpusfetch.com/c/how-must-an-instance-handle-reference-resolution-during-active-renaming-operations.md
# Remnant Warrant:    https://corpusfetch.com/c/how-must-an-instance-handle-reference-resolution-during-active-renaming-operations.warrant.json
# Markdown SHA-256:   32355a929f115957dfc0c303a680465cacad6ef5dee061778d6ceb7ecc64abee
# Code AST SHA-256:   4e8b97f97c21ec465f994325ddeec884df67f650019897417cf075b12ad0385b
# Verified Classes:   RenameVerdict, RenameTransition, RenamePolicy, RenameManifest, RenameTransitionGuard
# Defensive Guards:   0 fail-closed invariants (zero external deps)

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

class RenameVerdict(Enum):
    NO_ACTIVE_RENAME = auto()
    TRANSITION_ACTIVE_SAFE = auto()
    TRANSITION_ACTIVE_UNSAFE = auto()
    RENAME_COMPLETED = auto()

@dataclass(frozen=True)
class RenameTransition:
    rename_id: str
    old_reference: str
    new_reference: str
    transition_start_epoch: float
    transition_end_epoch: float
    current_epoch: float
    dual_resolution_verified: bool
    completion_marker_received: bool

@dataclass(frozen=True)
class RenamePolicy:
    require_dual_resolution: bool

@dataclass(frozen=True)
class RenameManifest:
    verdict: RenameVerdict
    directive: str
    manifest_digest: str

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

    @classmethod
    def evaluate_transition(
        cls, transition: RenameTransition, policy: RenamePolicy
    ) -> RenameManifest:
        
        # Gate 1: Completion marker
        if transition.completion_marker_received:
            digest = cls._hash(json.dumps({
                "rename": transition.rename_id,
                "status": "COMPLETED",
                "new_reference": transition.new_reference
            }, sort_keys=True))
            return RenameManifest(
                verdict=RenameVerdict.RENAME_COMPLETED,
                directive=f"PROCEED: Rename complete, use {transition.new_reference}.",
                manifest_digest=digest
            )

        # Gate 2: Transition active?
        if transition.current_epoch < transition.transition_start_epoch or transition.current_epoch > transition.transition_end_epoch:
            digest = cls._hash(json.dumps({
                "rename": transition.rename_id,
                "status": "OUTSIDE_WINDOW"
            }, sort_keys=True))
            return RenameManifest(
                verdict=RenameVerdict.NO_ACTIVE_RENAME,
                directive=f"PROCEED: No active rename window.",
                manifest_digest=digest
            )

        # Gate 3: Dual resolution check
        if policy.require_dual_resolution and not transition.dual_resolution_verified:
            return RenameManifest(
                verdict=RenameVerdict.TRANSITION_ACTIVE_UNSAFE,
                directive=f"HALT: Rename window active but dual resolution unverified.",
                manifest_digest=cls._hash(f"NO_DUAL:{transition.rename_id}")
            )

        # Gate 4: Safe transition
        digest = cls._hash(json.dumps({
            "rename": transition.rename_id,
            "old": transition.old_reference,
            "new": transition.new_reference,
            "dual_verified": str(transition.dual_resolution_verified)
        }, sort_keys=True))
        
        return RenameManifest(
            verdict=RenameVerdict.TRANSITION_ACTIVE_SAFE,
            directive=f"PROCEED: Rename window active, both {transition.old_reference} and {transition.new_reference} valid.",
            manifest_digest=digest
        )