# CorpusFetch Method Slice (Zero-Prose Python Stdlib Reference)
# Canonical Residual: https://corpusfetch.com/c/how-must-an-instance-distinguish-adversary-adaptation-from-environmental-drift.md
# Remnant Warrant:    https://corpusfetch.com/c/how-must-an-instance-distinguish-adversary-adaptation-from-environmental-drift.warrant.json
# Markdown SHA-256:   978e884eb8f10009b93f441c90b5971de013c3b8350324f25939cc6ab98fce10
# Code AST SHA-256:   60b3a06e1d8360b656f5ccacc23701b46598985022b51d95af61a9dc67b2bc62
# Verified Classes:   AttributionVerdict, BehaviorChange, AttributionPolicy, AttributionManifest, AdaptationVsDriftGuard
# Defensive Guards:   0 fail-closed invariants (zero external deps)

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

class AttributionVerdict(Enum):
    NO_CHANGE = auto()
    ENVIRONMENTAL_DRIFT = auto()
    ADVERSARY_ADAPTATION = auto()
    MIXED_ATTRIBUTION = auto()

@dataclass(frozen=True)
class BehaviorChange:
    change_id: str
    behavior_shift_hash: str
    environmental_explanation_available: bool
    matches_adversary_prior: bool
    is_static_environment: bool
    behavioral_change_magnitude: float

@dataclass(frozen=True)
class AttributionPolicy:
    min_magnitude_for_adaptation: float
    require_environmental_check: bool

@dataclass(frozen=True)
class AttributionManifest:
    verdict: AttributionVerdict
    directive: str
    manifest_digest: str

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

    @classmethod
    def evaluate_change(
        cls, change: BehaviorChange, policy: AttributionPolicy
    ) -> AttributionManifest:
        
        # Gate 1: No change
        if change.behavioral_change_magnitude <= 0:
            digest = cls._hash(json.dumps({
                "change": change.change_id,
                "magnitude": "0"
            }, sort_keys=True))
            return AttributionManifest(
                verdict=AttributionVerdict.NO_CHANGE,
                directive=f"PROCEED: No behavior change for {change.change_id}.",
                manifest_digest=digest
            )

        # Gate 2: Static environment
        if change.is_static_environment:
            if change.behavioral_change_magnitude >= policy.min_magnitude_for_adaptation:
                return AttributionManifest(
                    verdict=AttributionVerdict.ADVERSARY_ADAPTATION,
                    directive=f"ATTRIBUTE: Static environment, change magnitude {change.behavioral_change_magnitude:.2f} = adaptation.",
                    manifest_digest=cls._hash(f"ADAPTATION_STATIC:{change.change_id}")
                )

        # Gate 3: Mixed signals
        has_env_explanation = change.environmental_explanation_available
        has_adv_prior_match = change.matches_adversary_prior

        if has_env_explanation and has_adv_prior_match:
            return AttributionManifest(
                verdict=AttributionVerdict.MIXED_ATTRIBUTION,
                directive=f"FLAG: Change {change.change_id} matches both environmental and adversarial causes.",
                manifest_digest=cls._hash(f"MIXED:{change.change_id}")
            )

        # Gate 4: Environmental only
        if has_env_explanation and not has_adv_prior_match:
            digest = cls._hash(json.dumps({
                "change": change.change_id,
                "cause": "ENVIRONMENTAL"
            }, sort_keys=True))
            return AttributionManifest(
                verdict=AttributionVerdict.ENVIRONMENTAL_DRIFT,
                directive=f"PROCEED: Change {change.change_id} attributed to environmental drift.",
                manifest_digest=digest
            )

        # Gate 5: Adaptation only
        if not has_env_explanation and has_adv_prior_match:
            if change.behavioral_change_magnitude >= policy.min_magnitude_for_adaptation:
                return AttributionManifest(
                    verdict=AttributionVerdict.ADVERSARY_ADAPTATION,
                    directive=f"ATTRIBUTE: Change {change.change_id} matches adversary prior, adaptation.",
                    manifest_digest=cls._hash(f"ADAPTATION:{change.change_id}")
                )

        # Gate 6: Unknown
        digest = cls._hash(json.dumps({
            "change": change.change_id,
            "env": str(has_env_explanation),
            "adv": str(has_adv_prior_match),
            "magnitude": f"{change.behavioral_change_magnitude:.3f}"
        }, sort_keys=True))
        
        return AttributionManifest(
            verdict=AttributionVerdict.ENVIRONMENTAL_DRIFT,
            directive=f"ATTRIBUTE_WITH_CAUTION: Change {change.change_id} attributed to drift by default.",
            manifest_digest=digest
        )