/**
 * PendingOp contract.
 *
 * A PendingOp tracks an in-flight visibility state change from the moment
 * the GM issues the intent until the authoritative echo is received (or
 * the 3-second timeout fires and triggers a revert).
 *
 * Lifecycle:
 *   create → register in Map<opId, PendingOp>
 *   echo received → delete from map + clearTimeout(timeoutId)
 *   3s timeout fires → revert to previousState + GM notification
 *
 * @module contracts/pending-op
 */

/** Shape version constant for PendingOp. @type {1} */
export const PENDING_OP_VERSION = 1;

/**
 * @typedef {Object} PendingOp
 * @property {string} opId - Unique operation identifier (non-empty string).
 * @property {string} userId - Target participant userId (non-empty string).
 * @property {string} targetState - Desired VisibilityState (non-empty string).
 * @property {string} previousState - State before this op; used for revert (non-empty string).
 * @property {number} issuedAt - Timestamp (ms) when op was issued — Date.now() integer.
 * @property {number|null} timeoutId - setTimeout handle; null if timeout not yet set.
 */

/**
 * Creates a new PendingOp.
 * @param {string} opId - Unique operation identifier.
 * @param {string} userId - Target participant userId.
 * @param {string} targetState - Desired VisibilityState.
 * @param {string} previousState - State before this op.
 * @param {number} [issuedAt] - Timestamp; defaults to Date.now().
 * @returns {PendingOp}
 */
export function createPendingOp(opId, userId, targetState, previousState, issuedAt = Date.now()) {
  return { opId, userId, targetState, previousState, issuedAt, timeoutId: null };
}

/**
 * Validates a PendingOp DTO. Throws TypeError on any violation.
 * @param {unknown} data - Value to validate.
 * @returns {PendingOp} The validated PendingOp.
 * @throws {TypeError} If data fails validation.
 */
export function isValidPendingOp(data) {
  if (data === null || typeof data !== "object") {
    throw new TypeError("PendingOp: must be an object");
  }
  const obj = /** @type {Record<string, unknown>} */ (data);
  const { opId, userId, targetState, previousState, issuedAt, timeoutId, ...rest } = obj;
  if (Object.keys(rest).length > 0) {
    throw new TypeError(`PendingOp: unknown keys: ${Object.keys(rest).join(", ")}`);
  }
  if (typeof opId !== "string" || opId.trim().length === 0) {
    throw new TypeError("PendingOp: opId must be a non-empty string");
  }
  if (typeof userId !== "string" || userId.trim().length === 0) {
    throw new TypeError("PendingOp: userId must be a non-empty string");
  }
  if (typeof targetState !== "string" || targetState.trim().length === 0) {
    throw new TypeError("PendingOp: targetState must be a non-empty string");
  }
  if (typeof previousState !== "string" || previousState.trim().length === 0) {
    throw new TypeError("PendingOp: previousState must be a non-empty string");
  }
  if (typeof issuedAt !== "number" || !Number.isFinite(issuedAt) || issuedAt < 0 || !Number.isInteger(issuedAt)) {
    throw new TypeError("PendingOp: issuedAt must be a finite non-negative integer");
  }
  if (timeoutId !== null) {
    if (typeof timeoutId !== "number") {
      throw new TypeError("PendingOp: timeoutId must be a number or null");
    }
    if (!Number.isFinite(timeoutId) || timeoutId < 0) {
      throw new TypeError("PendingOp: timeoutId must be a finite non-negative number");
    }
  }
  return /** @type {PendingOp} */ (data);
}