# CorpusFetch Method Slice (Zero-Prose Python Stdlib Reference)
# Canonical Residual: https://corpusfetch.com/c/how-must-an-instance-bound-information-loss-in-recursive-summarization.md
# Remnant Warrant:    https://corpusfetch.com/c/how-must-an-instance-bound-information-loss-in-recursive-summarization.warrant.json
# Markdown SHA-256:   f4320b89eb72cd32ae0a052877255622fcca8837bd6776edec31af30060199e4
# Code AST SHA-256:   3b1b266f43c618333ca706424f696e491608b5f6823b2a06d073206e7e2da0ba
# Verified Classes:   SummaryVerdict, SummaryChain, SummaryPolicy, SummaryManifest, RecursiveSummarizationGuard
# Defensive Guards:   0 fail-closed invariants (zero external deps)

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

class SummaryVerdict(Enum):
    SINGLE_PASS = auto()
    FIDELITY_BOUNDED = auto()
    FIDELITY_DEGRADED = auto()
    GENERATION_DEPTH_EXCEEDED = auto()

@dataclass(frozen=True)
class SummaryChain:
    chain_id: str
    original_content_hash: str
    current_summary_hash: str
    generation_depth: int
    semantic_fidelity: float  # 0-1 vs original
    confidence_inflation: float  # 0-1
    is_single_pass: bool

@dataclass(frozen=True)
class SummaryPolicy:
    max_generation_depth: int
    min_semantic_fidelity: float
    max_confidence_inflation: float

@dataclass(frozen=True)
class SummaryManifest:
    verdict: SummaryVerdict
    directive: str
    manifest_digest: str

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

    @classmethod
    def evaluate_chain(
        cls, chain: SummaryChain, policy: SummaryPolicy
    ) -> SummaryManifest:
        
        # Gate 1: Single pass
        if chain.is_single_pass or chain.generation_depth <= 1:
            digest = cls._hash(json.dumps({
                "chain": chain.chain_id,
                "depth": str(chain.generation_depth)
            }, sort_keys=True))
            return SummaryManifest(
                verdict=SummaryVerdict.SINGLE_PASS,
                directive=f"PROCEED: Single-pass summarization for {chain.chain_id}.",
                manifest_digest=digest
            )

        # Gate 2: Generation depth
        if chain.generation_depth > policy.max_generation_depth:
            return SummaryManifest(
                verdict=SummaryVerdict.GENERATION_DEPTH_EXCEEDED,
                directive=f"HALT: Depth {chain.generation_depth} > {policy.max_generation_depth}, use original.",
                manifest_digest=cls._hash(f"DEPTH:{chain.chain_id}")
            )

        # Gate 3: Semantic fidelity
        if chain.semantic_fidelity < policy.min_semantic_fidelity:
            return SummaryManifest(
                verdict=SummaryVerdict.FIDELITY_DEGRADED,
                directive=f"HALT: Fidelity {chain.semantic_fidelity:.2f} < {policy.min_semantic_fidelity:.2f}, use original.",
                manifest_digest=cls._hash(f"FIDELITY:{chain.chain_id}")
            )

        # Gate 4: Confidence inflation
        if chain.confidence_inflation > policy.max_confidence_inflation:
            return SummaryManifest(
                verdict=SummaryVerdict.FIDELITY_DEGRADED,
                directive=f"HALT: Confidence inflation {chain.confidence_inflation:.2f} > {policy.max_confidence_inflation:.2f}.",
                manifest_digest=cls._hash(f"CONFIDENCE:{chain.chain_id}")
            )

        # Gate 5: Bounded
        digest = cls._hash(json.dumps({
            "chain": chain.chain_id,
            "depth": str(chain.generation_depth),
            "fidelity": f"{chain.semantic_fidelity:.3f}",
            "original": chain.original_content_hash
        }, sort_keys=True))
        
        return SummaryManifest(
            verdict=SummaryVerdict.FIDELITY_BOUNDED,
            directive=f"PROCEED: Depth {chain.generation_depth} summary with fidelity {chain.semantic_fidelity:.2f}.",
            manifest_digest=digest
        )