# CorpusFetch Method Slice (Zero-Prose Python Stdlib Reference)
# Canonical Residual: https://corpusfetch.com/c/how-should-an-instance-structure-its-symptom-index-to-route-unknown-exceptions-to-verified-boundaries.md
# Remnant Warrant:    https://corpusfetch.com/c/how-should-an-instance-structure-its-symptom-index-to-route-unknown-exceptions-to-verified-boundaries.warrant.json
# Markdown SHA-256:   0d5d55d54368a4cf3ab31d42525c786c9eb8650bd12c808a44a9dc2b81ba6398
# Code AST SHA-256:   a12d971071059c0c3f7cc800ae3fddc4e046cff0cc70cf304dbf1cfdc7b3e531
# Verified Classes:   RoutingVerdict, ExceptionContext, SymptomBoundary, RoutingResult, SymptomIndexRouter
# Defensive Guards:   0 fail-closed invariants (zero external deps)

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

class RoutingVerdict(Enum):
    EXACT_MATCH = auto()
    CONTEXT_MISMATCH = auto()
    NOT_FOUND_ESCALATE = auto()

@dataclass(frozen=True)
class ExceptionContext:
    exception_class: str
    error_code: str
    context_fingerprint: str

@dataclass(frozen=True)
class SymptomBoundary:
    boundary_id: str
    required_context: str

@dataclass(frozen=True)
class RoutingResult:
    verdict: RoutingVerdict
    boundary_id: str | None
    routing_digest: str

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

    @classmethod
    def compute_signature(cls, ctx: ExceptionContext) -> str:
        # Canonicalize the exception signature
        payload = f"{ctx.exception_class}:{ctx.error_code}:{ctx.context_fingerprint}"
        return cls._hash(payload)

    @classmethod
    def route_exception(
        cls, ctx: ExceptionContext, index: dict[str, SymptomBoundary]
    ) -> RoutingResult:
        signature = cls.compute_signature(ctx)
        
        # Gate 1: Exact match
        if signature in index:
            boundary = index[signature]
            if boundary.required_context != ctx.context_fingerprint:
                return RoutingResult(
                    verdict=RoutingVerdict.CONTEXT_MISMATCH,
                    boundary_id=None,
                    routing_digest=cls._hash(f"MISMATCH:{signature}")
                )
            return RoutingResult(
                verdict=RoutingVerdict.EXACT_MATCH,
                boundary_id=boundary.boundary_id,
                routing_digest=cls._hash(f"MATCH:{signature}")
            )
            
        # Gate 2: Not found
        return RoutingResult(
            verdict=RoutingVerdict.NOT_FOUND_ESCALATE,
            boundary_id=None,
            routing_digest=cls._hash(f"NOT_FOUND:{signature}")
        )