# CorpusFetch Method Slice (Zero-Prose Python Stdlib Reference)
# Canonical Residual: https://corpusfetch.com/c/how-must-an-instance-handle-semantic-search-returning-results-from-a-model-generated-corpus.md
# Remnant Warrant:    https://corpusfetch.com/c/how-must-an-instance-handle-semantic-search-returning-results-from-a-model-generated-corpus.warrant.json
# Markdown SHA-256:   9c3a6cc6b8ff03f9b202e69fa07959f558192ddcbdff04cc8b7bce88d092e49d
# Code AST SHA-256:   233e20b2d8033f3d5ef81b8f1c4ef646990abb2b0ecfe5e3dba487e70c7a7526
# Verified Classes:   AuthenticityClass, SynthesisVerdict, SearchResult, SynthesisPolicy, SynthesisManifest, SyntheticSourceGuard
# Defensive Guards:   1 fail-closed invariants (zero external deps)

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

class AuthenticityClass(Enum):
    HUMAN_AUTHORED = auto()
    SYNTHETIC_DEPTH_1 = auto()
    SYNTHETIC_DEPTH_2_PLUS = auto()
    UNKNOWN = auto()

class SynthesisVerdict(Enum):
    HUMAN_GROUNDED = auto()
    SYNTHETIC_DEPTH_1_ACCEPTABLE = auto()
    SYNTHETIC_DEPTH_EXCESSIVE = auto()
    UNVERIFIED_SOURCES = auto()

@dataclass(frozen=True)
class SearchResult:
    result_id: str
    authenticity: AuthenticityClass
    human_anchor_hash: str | None
    source_signature: str | None

@dataclass(frozen=True)
class SynthesisPolicy:
    min_human_grounding_ratio: float
    allow_depth_1_synthetic: bool

@dataclass(frozen=True)
class SynthesisManifest:
    verdict: SynthesisVerdict
    directive: str
    manifest_digest: str

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

    @classmethod
    def evaluate_results(
        cls, results: tuple[SearchResult, ...], policy: SynthesisPolicy
    ) -> SynthesisManifest:
        
        if not results:
            raise ValueError("No results to evaluate.")

        # Gate 1: Signature presence
        for r in results:
            if not r.source_signature:
                return SynthesisManifest(
                    verdict=SynthesisVerdict.UNVERIFIED_SOURCES,
                    directive=f"HALT: Result {r.result_id} lacks source signature.",
                    manifest_digest=cls._hash(f"NO_SIG:{r.result_id}")
                )

        # Gate 2: Human grounding ratio
        human_count = sum(1 for r in results if r.authenticity is AuthenticityClass.HUMAN_AUTHORED)
        ratio = human_count / len(results)

        # Gate 3: Depth 1 acceptance
        depth_1_count = sum(1 for r in results if r.authenticity is AuthenticityClass.SYNTHETIC_DEPTH_1)
        depth_2_plus_count = sum(1 for r in results if r.authenticity is AuthenticityClass.SYNTHETIC_DEPTH_2_PLUS)

        # If sufficient human grounding, all accepted
        if ratio >= policy.min_human_grounding_ratio:
            digest = cls._hash(json.dumps({
                "total": str(len(results)),
                "human": str(human_count),
                "ratio": f"{ratio:.2f}"
            }, sort_keys=True))
            return SynthesisManifest(
                verdict=SynthesisVerdict.HUMAN_GROUNDED,
                directive=f"PROCEED: {ratio:.2%} human grounding.",
                manifest_digest=digest
            )

        # If depth 1 allowed and no depth 2+
        if policy.allow_depth_1_synthetic and depth_2_plus_count == 0:
            digest = cls._hash(json.dumps({
                "total": str(len(results)),
                "human": str(human_count),
                "depth_1": str(depth_1_count),
                "depth_2_plus": "0"
            }, sort_keys=True))
            return SynthesisManifest(
                verdict=SynthesisVerdict.SYNTHETIC_DEPTH_1_ACCEPTABLE,
                directive=f"PROCEED: Human grounding {ratio:.2%} below threshold, but only depth-1 synthetic.",
                manifest_digest=digest
            )

        # Excessive synthetic
        return SynthesisManifest(
            verdict=SynthesisVerdict.SYNTHETIC_DEPTH_EXCESSIVE,
            directive=f"HALT: Only {ratio:.2%} human grounding, {depth_2_plus_count} depth-2+ synthetic. Re-query with human filter.",
            manifest_digest=cls._hash(f"SYNTHETIC:{ratio:.2f}")
        )