from __future__ import annotations

from dataclasses import dataclass
from typing import Protocol


@dataclass(frozen=True)
class NodeResult:
    status: str
    edge_result: str = "success"
    output_metadata: dict[str, object] | None = None
    telemetry: dict[str, object] | None = None
    failure_evidence: dict[str, object] | None = None
    pause_reason: str = ""


class NodeHandler(Protocol):
    node_type: str
    idempotent: bool
    replay_safe: bool
    destructive: bool

    def run(self, context: object) -> NodeResult: ...


class NodeHandlerRegistry:
    def __init__(self) -> None:
        self._handlers: dict[str, NodeHandler] = {}

    def register(self, handler: NodeHandler) -> None:
        self._handlers[handler.node_type] = handler

    def get(self, node_type: str) -> NodeHandler:
        try:
            return self._handlers[node_type]
        except KeyError as exc:
            raise KeyError(f"No graph node handler registered for {node_type}") from exc

    def has(self, node_type: str) -> bool:
        return node_type in self._handlers