/**
 * §16. Generic CPU Web Worker contract.
 *
 * The capability is `NOT_SELECTED` by default (§16.2). These types exist so a
 * selection can be expressed and validated, but no production worker entry is
 * created until a measured, CPU-bound task with an owner is contributed. This
 * runtime is separate from the OPFS dedicated worker and the Service Worker.
 */

export const WEB_WORKER_PROTOCOL = "CA_WEB_WORKER_V1" as const;

export const WEB_WORKER_BOUNDS = Object.freeze({
  taskGroups: 16,
  tasksPerGroup: 32,
  activeGroups: 4,
  queuedPerGroup: 32,
  queuedBytesPerGroup: 16 * 1024 * 1024,
  defaultInputBytes: 1024 * 1024,
  hardInputBytes: 8 * 1024 * 1024,
  defaultOutputBytes: 1024 * 1024,
  hardOutputBytes: 8 * 1024 * 1024,
  defaultDeadlineMs: 5_000,
  hardDeadlineMs: 30_000,
  cancelGraceMs: 250,
  idleTerminateMs: 60_000,
  restartsPerWindow: 3,
  restartWindowMs: 300_000,
  transferables: 16,
  mainThreadChunkBudgetMs: 8,
  mainThreadFallbackInputBytes: 1024 * 1024,
});

export interface InstalledWorkerTask {
  readonly taskId: string;
  readonly taskVersion: 1;
  readonly maximumInputBytes: number;
  readonly maximumOutputBytes: number;
  readonly deadlineMs: number;
}

export interface InstalledWebWorkerContribution {
  readonly taskGroupId: string;
  readonly tasks: readonly InstalledWorkerTask[];
  readonly fallback: "MAIN_THREAD_CHUNKED" | "UNSUPPORTED";
}

export type WorkerRequestMessage = Readonly<{
  protocol: typeof WEB_WORKER_PROTOCOL;
  kind: "EXECUTE";
  taskId: string;
  taskVersion: 1;
  requestId: string;
  workerGeneration: number;
  deadlineEpochMs: number;
  payload: unknown;
}>;

export type WorkerCancelMessage = Readonly<{
  protocol: typeof WEB_WORKER_PROTOCOL;
  kind: "CANCEL";
  requestId: string;
  workerGeneration: number;
}>;

export type WorkerFailureCode =
  | "TASK_UNKNOWN"
  | "VERSION_UNSUPPORTED"
  | "INPUT_INVALID"
  | "INPUT_TOO_LARGE"
  | "OUTPUT_INVALID"
  | "OUTPUT_TOO_LARGE"
  | "QUEUE_FULL"
  | "DEADLINE_EXCEEDED"
  | "CANCELLED"
  | "CRASHED"
  | "TRANSFER_FAILED"
  | "STALE_RESULT"
  | "RUNTIME_PROTOCOL_FAILURE";

export type WorkerResponseMessage =
  | Readonly<{
      protocol: typeof WEB_WORKER_PROTOCOL;
      kind: "SUCCESS";
      requestId: string;
      workerGeneration: number;
      payload: unknown;
    }>
  | Readonly<{
      protocol: typeof WEB_WORKER_PROTOCOL;
      kind: "FAILURE";
      requestId: string;
      workerGeneration: number;
      code: WorkerFailureCode;
    }>;

export function validateWebWorkerContributions(
  contributions: readonly InstalledWebWorkerContribution[],
): readonly InstalledWebWorkerContribution[] {
  const bounds = WEB_WORKER_BOUNDS;
  if (contributions.length > bounds.taskGroups) {
    throw new TypeError("Web Worker task groups exceed their bound.");
  }
  const groupIds = new Set<string>();
  const taskIds = new Set<string>();
  for (const contribution of contributions) {
    if (!contribution.taskGroupId || groupIds.has(contribution.taskGroupId)) {
      throw new TypeError("Web Worker task group identity is invalid.");
    }
    groupIds.add(contribution.taskGroupId);
    if (
      contribution.tasks.length === 0 ||
      contribution.tasks.length > bounds.tasksPerGroup
    ) {
      throw new TypeError("Web Worker task count is out of range.");
    }
    for (const task of contribution.tasks) {
      const qualified = `${contribution.taskGroupId}/${task.taskId}`;
      if (!task.taskId || taskIds.has(qualified)) {
        throw new TypeError("Duplicate Web Worker task.");
      }
      taskIds.add(qualified);
      if (
        task.taskVersion !== 1 ||
        !Number.isSafeInteger(task.maximumInputBytes) ||
        task.maximumInputBytes < 1 ||
        task.maximumInputBytes > bounds.hardInputBytes ||
        !Number.isSafeInteger(task.maximumOutputBytes) ||
        task.maximumOutputBytes < 1 ||
        task.maximumOutputBytes > bounds.hardOutputBytes ||
        !Number.isSafeInteger(task.deadlineMs) ||
        task.deadlineMs < 1 ||
        task.deadlineMs > bounds.hardDeadlineMs
      ) {
        throw new TypeError(`Web Worker task bounds invalid: ${qualified}`);
      }
    }
  }
  return Object.freeze([...contributions]);
}