/** Stored per-cell freshness and completion metadata. */
export type CellStalenessMeta = {
  status?: string | null;
  completedAt?: number | null;
  staleAt?: number | null;
  staleAfterSeconds?: number | null;
};

/**
 * Previous durable cell value passed to object-column resolvers.
 *
 * The runtime supplies this when a row+column is being recomputed after a
 * previous value existed. `value` has the same type that the column returns;
 * freshness metadata lives beside it.
 *
 * @sdkReference runtime 120
 */
export type PreviousCell<Value = unknown> = {
  /** Previous completed value for this row+column. */
  value: Value;
  /** Millisecond timestamp when the previous value completed. */
  completedAt?: number;
  /** Millisecond timestamp when the previous value becomes stale; `null` means no expiry. */
  staleAt?: number | null;
  /** Resolved numeric TTL in seconds for the previous value, when present. */
  staleAfterSeconds?: number;
};

export const DEEPLINE_CELL_META_FIELD = '__deeplineCellMeta';

export function previousCellFromValue<Value>(input: {
  hasValue: boolean;
  value: Value;
  meta?: CellStalenessMeta | null;
}): PreviousCell<Value> | undefined {
  if (!input.hasValue) {
    return undefined;
  }

  const previous: PreviousCell<Value> = {
    value: input.value,
  };
  if (
    typeof input.meta?.completedAt === 'number' &&
    Number.isFinite(input.meta.completedAt)
  ) {
    previous.completedAt = input.meta.completedAt;
  }
  if (
    input.meta &&
    Object.prototype.hasOwnProperty.call(input.meta, 'staleAt')
  ) {
    previous.staleAt =
      typeof input.meta.staleAt === 'number' &&
      Number.isFinite(input.meta.staleAt)
        ? input.meta.staleAt
        : null;
  }
  if (
    typeof input.meta?.staleAfterSeconds === 'number' &&
    Number.isFinite(input.meta.staleAfterSeconds)
  ) {
    previous.staleAfterSeconds = input.meta.staleAfterSeconds;
  }
  return previous;
}