/*---------------------------------------------------------------------------------------------
 *  Copyright (c) Microsoft Corporation. All rights reserved.
 *  Licensed under the MIT License. See License.txt in the project root for license information.
 *--------------------------------------------------------------------------------------------*/

export const enum Constants {
  START_CH_CODE = 32, // Space
  END_CH_CODE = 126, // Tilde (~)
  UNKNOWN_CODE = 65533, // UTF placeholder code
  CHAR_COUNT = END_CH_CODE - START_CH_CODE + 2,

  SAMPLED_CHAR_HEIGHT = 16,
  SAMPLED_CHAR_WIDTH = 10,

  BASE_CHAR_HEIGHT = 2,
  BASE_CHAR_WIDTH = 1,

  RGBA_CHANNELS_CNT = 4,
  RGBA_SAMPLED_ROW_WIDTH = RGBA_CHANNELS_CNT * CHAR_COUNT * SAMPLED_CHAR_WIDTH,
}

export const allCharCodes: ReadonlyArray<number> = (() => {
  const v: number[] = [];
  for (let i = Constants.START_CH_CODE; i <= Constants.END_CH_CODE; i++) {
    v.push(i);
  }

  v.push(Constants.UNKNOWN_CODE);
  return v;
})();

export const getCharIndex = (chCode: number, fontScale: number) => {
  chCode -= Constants.START_CH_CODE;
  if (chCode < 0 || chCode > Constants.CHAR_COUNT) {
    if (fontScale <= 2) {
      // for smaller scales, we can get away with using any ASCII character...
      return (chCode + Constants.CHAR_COUNT) % Constants.CHAR_COUNT;
    }
    return Constants.CHAR_COUNT - 1; // unknown symbol
  }

  return chCode;
};