# CorpusFetch Method Slice (Zero-Prose Python Stdlib Reference)
# Canonical Residual: https://corpusfetch.com/c/how-must-an-instance-distinguish-strategic-concession-from-genuine-agreement.md
# Remnant Warrant:    https://corpusfetch.com/c/how-must-an-instance-distinguish-strategic-concession-from-genuine-agreement.warrant.json
# Markdown SHA-256:   282ce6c1952d398f57473a33d02617113f29d833f8e5b3b6f7b623d83e6e98fa
# Code AST SHA-256:   8c648013d63b2ca5257f1be5e977344df880a9f64df6258fb54aa85e02fc4c27
# Verified Classes:   ConcessionVerdict, Concession, ConcessionPolicy, ConcessionManifest, StrategicConcessionGuard
# Defensive Guards:   0 fail-closed invariants (zero external deps)

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

class ConcessionVerdict(Enum):
    NO_CONCESSION = auto()
    GENUINE_COMMITTED = auto()
    GENUINE_UNCOMMITTED = auto()
    STRATEGIC_CONCESSION_SUSPECTED = auto()

@dataclass(frozen=True)
class Concession:
    concession_id: str
    is_committed: bool
    peer_reopening_history: int
    concession_scope: float  # 0-1, relative to total negotiation
    reciprocity_expected: bool
    reciprocity_value: float

@dataclass(frozen=True)
class ConcessionPolicy:
    min_scope_for_commitment: float
    max_acceptable_reopening_history: int

@dataclass(frozen=True)
class ConcessionManifest:
    verdict: ConcessionVerdict
    directive: str
    manifest_digest: str

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

    @classmethod
    def evaluate_concession(
        cls, concession: Concession, policy: ConcessionPolicy
    ) -> ConcessionManifest:
        
        # Gate 1: No concession
        if not concession.concession_id:
            digest = cls._hash(json.dumps({
                "concession": "NONE"
            }, sort_keys=True))
            return ConcessionManifest(
                verdict=ConcessionVerdict.NO_CONCESSION,
                directive=f"PROCEED: No concession to evaluate.",
                manifest_digest=digest
            )

        # Gate 2: Committed
        if concession.is_committed:
            digest = cls._hash(json.dumps({
                "concession": concession.concession_id,
                "committed": True
            }, sort_keys=True))
            return ConcessionManifest(
                verdict=ConcessionVerdict.GENUINE_COMMITTED,
                directive=f"PROCEED: Concession {concession.concession_id} is committed.",
                manifest_digest=digest
            )

        # Gate 3: Strategic history
        if concession.peer_reopening_history > policy.max_acceptable_reopening_history:
            return ConcessionManifest(
                verdict=ConcessionVerdict.STRATEGIC_CONCESSION_SUSPECTED,
                directive=f"FLAG: Peer has {concession.peer_reopening_history} reopens, concession suspect.",
                manifest_digest=cls._hash(f"STRATEGIC:{concession.concession_id}")
            )

        # Gate 4: Scope requires commitment
        if concession.concession_scope >= policy.min_scope_for_commitment:
            return ConcessionManifest(
                verdict=ConcessionVerdict.STRATEGIC_CONCESSION_SUSPECTED,
                directive=f"FLAG: Large concession {concession.concession_scope:.2f} without commitment.",
                manifest_digest=cls._hash(f"UNCOMMITTED_LARGE:{concession.concession_id}")
            )

        # Gate 5: Genuine uncommitted
        digest = cls._hash(json.dumps({
            "concession": concession.concession_id,
            "scope": f"{concession.concession_scope:.3f}",
            "reopening_history": str(concession.peer_reopening_history)
        }, sort_keys=True))
        
        return ConcessionManifest(
            verdict=ConcessionVerdict.GENUINE_UNCOMMITTED,
            directive=f"PROCEED: Concession {concession.concession_id} plausible as genuine.",
            manifest_digest=digest
        )