import { randomBytes } from "node:crypto";
import type { OperationArtifacts } from "./operation-artifacts.ts";
import { retainAcrossReload } from "./reload-boundary.ts";

/**
 * Process-local identity for one parent extension runtime.
 *
 * This is intentionally an opaque string rather than a session or filesystem
 * identity. It is never a recovery key and must not be persisted.
 */
export type ParentRuntimeId = string;

/** Identity for one independent Fresh Completion operation. */
export type CompletionOperationId = string;

const OPERATION_ID_PATTERN = /^[a-zA-Z0-9][a-zA-Z0-9._-]*$/;
const WINDOWS_DEVICE_NAMES = new Set([
  "CON",
  "PRN",
  "AUX",
  "NUL",
  ...Array.from({ length: 9 }, (_, index) => `COM${index + 1}`),
  ...Array.from({ length: 9 }, (_, index) => `LPT${index + 1}`),
]);

/**
 * Validate the wire-safe operation identity used in artifact filenames.
 *
 * Operation IDs are generated by this module, but the child reconstructs one
 * from environment variables. Keeping the grammar here prevents separators,
 * control characters, and Windows device names from becoming path components.
 */
export function isValidOperationId(value: unknown): value is CompletionOperationId {
  if (
    typeof value !== "string" ||
    value.length === 0 ||
    value.length > 128 ||
    !OPERATION_ID_PATTERN.test(value) ||
    value.endsWith(".")
  ) return false;

  const deviceStem = value.split(".", 1)[0].toUpperCase();
  return !WINDOWS_DEVICE_NAMES.has(deviceStem);
}

/**
 * Operation identity and its private protocol namespace. Artifact paths locate
 * protocol data; the operation ID remains the sole logical identity.
 */
export interface OperationReference {
  operationId: CompletionOperationId;
  artifacts: OperationArtifacts;
}

/** Build one operation reference without repeating namespace assembly. */
export function createOperationReference(
  operationId: CompletionOperationId,
  artifacts: OperationArtifacts,
): OperationReference {
  return { operationId, artifacts };
}

/** Allocate a unique identity for one parent runtime. */
export function createParentRuntimeId(): ParentRuntimeId {
  return `parent-${randomBytes(16).toString("hex")}`;
}

/** Allocate a unique identity for one Fresh Completion operation. */
export function createCompletionOperationId(): CompletionOperationId {
  return randomBytes(16).toString("hex");
}

const PROCESS_PARENT_RUNTIME_KEY = Symbol.for("pi-subagents/process-parent-runtime-id");

/**
 * Return the identity for the current process's default parent runtime.
 *
 * The value is retained across extension module reloads but is never persisted
 * as a session or recovery key. Independent ParentRuntime instances can still
 * inject their own identity through their construction seam.
 */
export function getProcessParentRuntimeId(): ParentRuntimeId {
  return retainAcrossReload(PROCESS_PARENT_RUNTIME_KEY, createParentRuntimeId);
}