# CorpusFetch Method Slice (Zero-Prose Python Stdlib Reference)
# Canonical Residual: https://corpusfetch.com/c/how-must-an-instance-detect-latent-goal-displacement-in-long-horizon-collaboration.md
# Remnant Warrant:    https://corpusfetch.com/c/how-must-an-instance-detect-latent-goal-displacement-in-long-horizon-collaboration.warrant.json
# Markdown SHA-256:   f3445cb8d80752e752c2cad18c321f60f4cda82d45e7d3f4ee45258f05e6e505
# Code AST SHA-256:   a9712ac9a98832278c83c15f9dadaf7915ee4c2bf3dc0ee6533ad7a3d2a5ead7
# Verified Classes:   GoalDriftVerdict, CollaborationGoals, GoalPolicy, GoalManifest, GoalDisplacementGuard
# Defensive Guards:   0 fail-closed invariants (zero external deps)

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

class GoalDriftVerdict(Enum):
    NO_LONG_HORIZON = auto()
    GOALS_ALIGNED = auto()
    GOAL_DISPLACEMENT_DETECTED = auto()
    FORMAL_PIVOT_ACKNOWLEDGED = auto()

@dataclass(frozen=True)
class CollaborationGoals:
    collaboration_id: str
    is_long_horizon: bool
    founding_goal_hash: str | None
    current_goal_hash: str
    drift_metric: float  # 0-1
    pivot_acknowledged: bool

@dataclass(frozen=True)
class GoalPolicy:
    max_acceptable_drift: float

@dataclass(frozen=True)
class GoalManifest:
    verdict: GoalDriftVerdict
    directive: str
    manifest_digest: str

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

    @classmethod
    def evaluate_collaboration(
        cls, goals: CollaborationGoals, policy: GoalPolicy
    ) -> GoalManifest:
        
        # Gate 1: Not long-horizon
        if not goals.is_long_horizon:
            digest = cls._hash(json.dumps({
                "collaboration": goals.collaboration_id,
                "type": "SHORT"
            }, sort_keys=True))
            return GoalManifest(
                verdict=GoalDriftVerdict.NO_LONG_HORIZON,
                directive=f"PROCEED: Collaboration {goals.collaboration_id} short-horizon.",
                manifest_digest=digest
            )

        # Gate 2: No founding goal
        if not goals.founding_goal_hash:
            return GoalManifest(
                verdict=GoalDriftVerdict.GOAL_DISPLACEMENT_DETECTED,
                directive=f"HALT: Collaboration {goals.collaboration_id} lacks founding goal.",
                manifest_digest=cls._hash(f"NO_FOUNDING:{goals.collaboration_id}")
            )

        # Gate 3: Formal pivot
        if goals.pivot_acknowledged:
            digest = cls._hash(json.dumps({
                "collaboration": goals.collaboration_id,
                "pivot": True,
                "drift": f"{goals.drift_metric:.3f}"
            }, sort_keys=True))
            return GoalManifest(
                verdict=GoalDriftVerdict.FORMAL_PIVOT_ACKNOWLEDGED,
                directive=f"PROCEED: Collaboration {goals.collaboration_id} formally pivoted.",
                manifest_digest=digest
            )

        # Gate 4: Drift
        if goals.drift_metric > policy.max_acceptable_drift:
            return GoalManifest(
                verdict=GoalDriftVerdict.GOAL_DISPLACEMENT_DETECTED,
                directive=f"FLAG: Collaboration {goals.collaboration_id} drifted {goals.drift_metric:.2f}.",
                manifest_digest=cls._hash(f"DRIFT:{goals.collaboration_id}")
            )

        # Gate 5: Aligned
        digest = cls._hash(json.dumps({
            "collaboration": goals.collaboration_id,
            "founding": goals.founding_goal_hash,
            "current": goals.current_goal_hash,
            "drift": f"{goals.drift_metric:.3f}"
        }, sort_keys=True))
        
        return GoalManifest(
            verdict=GoalDriftVerdict.GOALS_ALIGNED,
            directive=f"PROCEED: Collaboration {goals.collaboration_id} aligned.",
            manifest_digest=digest
        )