import type { KernelToHostMessage } from "../../bridge/protocol.ts";

export type ResultMessage = Extract<KernelToHostMessage, { type: "result" }>;
export type ToolCallMessage = Extract<
  KernelToHostMessage,
  { type: "tool-call" }
>;

export type JavaScriptKernelMode = "worker" | "inline" | "process";

export interface JavaScriptKernelOptions {
  readonly cwd: string;
  readonly hardenedCells?: boolean;
  readonly jitless?: boolean;
  readonly onMessage?: (message: KernelToHostMessage) => void;
  readonly parallelPoolWidth: number;
  readonly sessionId: string;
  readonly workerEntryUrl?: URL;
}

export interface JavaScriptRunInput {
  readonly cellId: string;
  readonly code: string;
  readonly onMessage?: (message: KernelToHostMessage) => void;
  readonly strings?: Readonly<Record<string, string>>;
  readonly timeoutMs?: number;
}

export type KernelOperation = "run" | "reset" | "interrupt";
export type LifecycleState = "open" | "closing" | "closed";

export class JavaScriptKernelClosedError extends Error {
  readonly name = "JavaScriptKernelClosedError";
  readonly operation: KernelOperation;

  constructor(operation: KernelOperation) {
    super(`Cannot ${operation}: JavaScript kernel is closed`);
    this.operation = operation;
  }
}

export function assertJavaScriptKernelOpen(
  lifecycle: LifecycleState,
  operation: KernelOperation
): void {
  if (lifecycle !== "open") {
    throw new JavaScriptKernelClosedError(operation);
  }
}