import Histogram, { BitBucketSize } from "./Histogram";
import { constructorFromBucketSize } from "./JsHistogramFactory";
import { WasmHistogram, webAssemblyReady, webAssemblyAvailable } from "./wasm";

export interface BuildRequest {
  /**
   * The size in bit of each count bucket
   * Default value is 32
   */
  bitBucketSize?: BitBucketSize;
  /**
   * Control whether or not the histogram can auto-resize and auto-adjust it's
   * highestTrackableValue
   * Default value is true
   */
  autoResize?: boolean;
  /**
   * The lowest value that can be discerned (distinguished from 0) by the histogram.
   * Must be a positive integer that is {@literal >=} 1. May be internally rounded
   * down to nearest power of 2.
   * Default value is 1
   */
  lowestDiscernibleValue?: number;
  /**
   * The highest value to be tracked by the histogram. Must be a positive
   * integer that is {@literal >=} (2 * lowestDiscernibleValue).
   * Default value is Number.MAX_SAFE_INTEGER
   */
  highestTrackableValue?: number;
  /**
   * The number of significant decimal digits to which the histogram will
   * maintain value resolution and separation. Must be a non-negative
   * integer between 0 and 5.
   * Default value is 3
   */
  numberOfSignificantValueDigits?: 1 | 2 | 3 | 4 | 5;
  /**
   * Is WebAssembly used to speed up computations.
   * Default value is false
   */
  useWebAssembly?: boolean;
}

export const defaultRequest: BuildRequest = {
  bitBucketSize: 32,
  autoResize: true,
  lowestDiscernibleValue: 1,
  highestTrackableValue: 2,
  numberOfSignificantValueDigits: 3,
  useWebAssembly: false,
};

export const build = (request = defaultRequest): Histogram => {
  const parameters = Object.assign({}, defaultRequest, request);
  if (request.useWebAssembly && webAssemblyAvailable) {
    return WasmHistogram.build(parameters);
  }

  const histogramConstr = constructorFromBucketSize(
    parameters.bitBucketSize as BitBucketSize
  );

  const histogram = new histogramConstr(
    parameters.lowestDiscernibleValue as number,
    parameters.highestTrackableValue as number,
    parameters.numberOfSignificantValueDigits as number
  );
  histogram.autoResize = parameters.autoResize as boolean;
  return histogram;
};