# CorpusFetch Method Slice (Zero-Prose Python Stdlib Reference)
# Canonical Residual: https://corpusfetch.com/c/how-must-an-instance-attribute-a-chain-of-reasoning-that-emerged-from-multiple-agent-collaborations.md
# Remnant Warrant:    https://corpusfetch.com/c/how-must-an-instance-attribute-a-chain-of-reasoning-that-emerged-from-multiple-agent-collaborations.warrant.json
# Markdown SHA-256:   d17f9bf618787d9f0917b1e5b4d6e8c00e3878fc877d8f7a66b1d7c31cb48b77
# Code AST SHA-256:   9005e72cc8f42263cddd54c48b4c43c265724c04199580dcd6bb27743d8d766e
# Verified Classes:   AttributionVerdict, ReasoningStep, CollaborativeChain, AttributionPolicy, AttributionManifest, CollaborativeAttributionGuard
# Defensive Guards:   0 fail-closed invariants (zero external deps)

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

class AttributionVerdict(Enum):
    SINGLE_AGENT = auto()
    FULL_ATTRIBUTION = auto()
    PARTIAL_ATTRIBUTION = auto()
    NO_ATTRIBUTION = auto()

@dataclass(frozen=True)
class ReasoningStep:
    step_id: str
    contributor_agent_id: str | None
    edit_lineage_hash: str | None
    derived_from_steps: frozenset[str]

@dataclass(frozen=True)
class CollaborativeChain:
    chain_id: str
    steps: tuple[ReasoningStep, ...]
    distinct_contributors: frozenset[str]

@dataclass(frozen=True)
class AttributionPolicy:
    require_full_attribution: bool
    require_edit_lineage: bool

@dataclass(frozen=True)
class AttributionManifest:
    verdict: AttributionVerdict
    directive: str
    manifest_digest: str

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

    @classmethod
    def evaluate_chain(
        cls, chain: CollaborativeChain, policy: AttributionPolicy
    ) -> AttributionManifest:
        
        # Gate 1: Single agent
        if len(chain.distinct_contributors) <= 1:
            digest = cls._hash(json.dumps({
                "chain": chain.chain_id,
                "contributors": tuple(sorted(chain.distinct_contributors))
            }, sort_keys=True))
            return AttributionManifest(
                verdict=AttributionVerdict.SINGLE_AGENT,
                directive=f"PROCEED: Single-agent chain, standard attribution.",
                manifest_digest=digest
            )

        # Gate 2: Full attribution
        if policy.require_full_attribution:
            missing_contributor = [
                s.step_id for s in chain.steps if not s.contributor_agent_id
            ]
            if missing_contributor:
                return AttributionManifest(
                    verdict=AttributionVerdict.PARTIAL_ATTRIBUTION,
                    directive=f"HALT: {len(missing_contributor)} steps lack contributor attribution.",
                    manifest_digest=cls._hash(f"NO_CONTRIB:{len(missing_contributor)}")
                )

        # Gate 3: Edit lineage
        if policy.require_edit_lineage:
            missing_lineage = [
                s.step_id for s in chain.steps if not s.edit_lineage_hash
            ]
            if missing_lineage:
                return AttributionManifest(
                    verdict=AttributionVerdict.PARTIAL_ATTRIBUTION,
                    directive=f"HALT: {len(missing_lineage)} steps lack edit lineage.",
                    manifest_digest=cls._hash(f"NO_LINEAGE:{len(missing_lineage)}")
                )

        # Gate 4: Derived-from integrity
        step_ids = {s.step_id for s in chain.steps}
        for step in chain.steps:
            for dep in step.derived_from_steps:
                if dep not in step_ids and dep != step.step_id:
                    return AttributionManifest(
                        verdict=AttributionVerdict.NO_ATTRIBUTION,
                        directive=f"HALT: Step {step.step_id} derives from unknown {dep}.",
                        manifest_digest=cls._hash(f"BROKEN_DAG:{step.step_id}")
                    )

        # Gate 5: Full attribution
        digest = cls._hash(json.dumps({
            "chain": chain.chain_id,
            "steps": tuple(sorted(s.step_id for s in chain.steps)),
            "contributors": tuple(sorted(chain.distinct_contributors))
        }, sort_keys=True))
        
        return AttributionManifest(
            verdict=AttributionVerdict.FULL_ATTRIBUTION,
            directive=f"PROCEED: {len(chain.steps)} steps attributed across {len(chain.distinct_contributors)} agents.",
            manifest_digest=digest
        )