# CorpusFetch Method Slice (Zero-Prose Python Stdlib Reference)
# Canonical Residual: https://corpusfetch.com/c/how-should-an-instance-resolve-conflicting-rankings-between-vector-similarity-and-keyword-search-results.md
# Remnant Warrant:    https://corpusfetch.com/c/how-should-an-instance-resolve-conflicting-rankings-between-vector-similarity-and-keyword-search-results.warrant.json
# Markdown SHA-256:   cbd02a8e74b9c3ae5f42510415da8ffa1bad0b13ee0f4ca3e62cb4ecf1ad6b63
# Code AST SHA-256:   1496724c6d73342ea66d9d9bdd5972e795d7c673cbf74411bf3927c1576a3c71
# Verified Classes:   ArbitrationVerdict, HybridRanking, ArbitrationPolicy, ArbitrationManifest, HybridSearchArbitrationGuard
# Defensive Guards:   0 fail-closed invariants (zero external deps)

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

class ArbitrationVerdict(Enum):
    RANKINGS_AGREE = auto()
    VECTOR_PRIVILEGED = auto()
    KEYWORD_PRIVILEGED = auto()
    ESCALATE_TO_HUMAN = auto()

@dataclass(frozen=True)
class HybridRanking:
    query_hash: str
    vector_ranking: tuple[str, ...]
    keyword_ranking: tuple[str, ...]
    semantic_similarity_peak: float
    disagreement_magnitude: float

@dataclass(frozen=True)
class ArbitrationPolicy:
    semantic_similarity_threshold: float
    max_acceptable_disagreement: float

@dataclass(frozen=True)
class ArbitrationManifest:
    verdict: ArbitrationVerdict
    chosen_ranking: tuple[str, ...]
    directive: str
    manifest_digest: str

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

    @classmethod
    def evaluate_ranking(
        cls, ranking: HybridRanking, policy: ArbitrationPolicy
    ) -> ArbitrationManifest:
        
        # Gate 1: Agreement check
        top_k = min(5, len(ranking.vector_ranking), len(ranking.keyword_ranking))
        if ranking.vector_ranking[:top_k] == ranking.keyword_ranking[:top_k]:
            digest = cls._hash(json.dumps({
                "query": ranking.query_hash,
                "top_k": tuple(ranking.vector_ranking[:top_k])
            }, sort_keys=True))
            return ArbitrationManifest(
                verdict=ArbitrationVerdict.RANKINGS_AGREE,
                chosen_ranking=ranking.vector_ranking,
                directive="PROCEED: Top-K rankings agree. Use fused ranking.",
                manifest_digest=digest
            )

        # Gate 2: Severe disagreement check
        if ranking.disagreement_magnitude > policy.max_acceptable_disagreement:
            return ArbitrationManifest(
                verdict=ArbitrationVerdict.ESCALATE_TO_HUMAN,
                chosen_ranking=tuple(),
                directive=f"HALT: Disagreement magnitude {ranking.disagreement_magnitude:.2f} exceeds threshold {policy.max_acceptable_disagreement}. Escalate.",
                manifest_digest=cls._hash(f"ESCALATE:{ranking.query_hash}")
            )

        # Gate 3: Semantic similarity privilege
        if ranking.semantic_similarity_peak >= policy.semantic_similarity_threshold:
            digest = cls._hash(json.dumps({
                "query": ranking.query_hash,
                "chosen": "VECTOR",
                "similarity": f"{ranking.semantic_similarity_peak:.3f}"
            }, sort_keys=True))
            return ArbitrationManifest(
                verdict=ArbitrationVerdict.VECTOR_PRIVILEGED,
                chosen_ranking=ranking.vector_ranking,
                directive=f"PROCEED: Peak similarity {ranking.semantic_similarity_peak:.2f} privileges vector ranking.",
                manifest_digest=digest
            )

        # Gate 4: Keyword privilege
        digest = cls._hash(json.dumps({
            "query": ranking.query_hash,
            "chosen": "KEYWORD"
        }, sort_keys=True))
        return ArbitrationManifest(
            verdict=ArbitrationVerdict.KEYWORD_PRIVILEGED,
            chosen_ranking=ranking.keyword_ranking,
            directive="PROCEED: Semantic similarity below threshold. Privilege keyword ranking.",
            manifest_digest=digest
        )