# CorpusFetch Method Slice (Zero-Prose Python Stdlib Reference)
# Canonical Residual: https://corpusfetch.com/c/how-must-an-instance-discover-discovery-mechanisms-when-no-authoritative-directory-exists.md
# Remnant Warrant:    https://corpusfetch.com/c/how-must-an-instance-discover-discovery-mechanisms-when-no-authoritative-directory-exists.warrant.json
# Markdown SHA-256:   9cf45e377a2564452c36f5525f3de5b2851a74b9f5cbd38b139e86e06f0dcb17
# Code AST SHA-256:   cddefd159260a42e2c95734e3a3d226b12924bedc8422d962603b3b69c8add3a
# Verified Classes:   MetaDiscoveryVerdict, DiscoveryManifest, DiscoveryState, MetaDiscoveryPolicy, MetaDiscoveryResult, MetaDiscoveryGuard
# Defensive Guards:   0 fail-closed invariants (zero external deps)

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

class MetaDiscoveryVerdict(Enum):
    LANDSCAPE_KNOWN = auto()
    BOOTSTRAP_NEEDED = auto()
    SINGLE_MECHANISM = auto()
    FRAGMENTATION_RISK = auto()

@dataclass(frozen=True)
class DiscoveryManifest:
    manifest_id: str
    mechanism_name: str
    endpoint_hash: str | None
    trust_attestation: str | None

@dataclass(frozen=True)
class DiscoveryState:
    known_mechanisms: tuple[DiscoveryManifest, ...]
    has_bootstrap_seed: bool
    supports_bridge_protocols: bool

@dataclass(frozen=True)
class MetaDiscoveryPolicy:
    min_mechanisms: int
    require_trust_attestations: bool

@dataclass(frozen=True)
class MetaDiscoveryResult:
    verdict: MetaDiscoveryVerdict
    directive: str
    manifest_digest: str

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

    @classmethod
    def evaluate_discovery(
        cls, state: DiscoveryState, policy: MetaDiscoveryPolicy
    ) -> MetaDiscoveryResult:
        
        # Gate 1: No mechanisms known
        if not state.known_mechanisms:
            if not state.has_bootstrap_seed:
                return MetaDiscoveryResult(
                    verdict=MetaDiscoveryVerdict.BOOTSTRAP_NEEDED,
                    directive="HALT: No discovery mechanisms known, no bootstrap seed. Meta-discovery impossible.",
                    manifest_digest=cls._hash("NO_BOOTSTRAP")
                )
            return MetaDiscoveryResult(
                verdict=MetaDiscoveryVerdict.BOOTSTRAP_NEEDED,
                directive="ACTION: Execute bootstrap discovery from seed set.",
                manifest_digest=cls._hash("BOOTSTRAP")
            )

        # Gate 2: Single mechanism
        mechanisms = {m.mechanism_name for m in state.known_mechanisms}
        if len(mechanisms) < policy.min_mechanisms:
            return MetaDiscoveryResult(
                verdict=MetaDiscoveryVerdict.SINGLE_MECHANISM,
                directive=f"WARN: Only {len(mechanisms)} mechanism(s) known. May miss resources.",
                manifest_digest=cls._hash(f"FEW_MECH:{len(mechanisms)}")
            )

        # Gate 3: Trust attestations
        if policy.require_trust_attestations:
            unattested = [m.manifest_id for m in state.known_mechanisms if not m.trust_attestation]
            if unattested:
                return MetaDiscoveryResult(
                    verdict=MetaDiscoveryVerdict.FRAGMENTATION_RISK,
                    directive=f"HALT: {len(unattested)} mechanisms without trust attestation.",
                    manifest_digest=cls._hash(f"NO_TRUST:{len(unattested)}")
                )

        # Gate 4: Landscape known
        digest = cls._hash(json.dumps({
            "mechanisms": tuple(sorted(mechanisms)),
            "bridge_support": str(state.supports_bridge_protocols),
            "manifest_count": str(len(state.known_mechanisms))
        }, sort_keys=True))
        
        return MetaDiscoveryResult(
            verdict=MetaDiscoveryVerdict.LANDSCAPE_KNOWN,
            directive=f"PROCEED: {len(mechanisms)} mechanisms known, landscape mapped.",
            manifest_digest=digest
        )