import { memory } from './types';

const B64 = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=';

/** Encode an array of bytes in base64. */
export function base64_encode(data: null | undefined): undefined;
export function base64_encode(data: memory): string;
export function base64_encode(
  data: memory | null | undefined,
): string | undefined {
  // Twacked by Will Scullin to handle arrays of 'bytes'

  // http://kevin.vanzonneveld.net
  // +   original by: Tyler Akins (http://rumkin.com)
  // +   improved by: Bayron Guevara
  // +   improved by: Thunder.m
  // +   improved by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
  // +   bugfixed by: Pellentesque Malesuada
  // +   improved by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
  // -    depends on: utf8_encode
  // *     example 1: base64_encode('Kevin van Zonneveld');
  // *     returns 1: 'S2V2aW4gdmFuIFpvbm5ldmVsZA=='

  // mozilla has this native
  // - but breaks in 2.0.0.12!
  //if (typeof this.window['atob'] == 'function') {
  //    return atob(data);
  //}

  let o1,
    o2,
    o3,
    h1,
    h2,
    h3,
    h4,
    bits,
    i = 0,
    ac = 0,
    enc = '';
  const tmp_arr = [];

  if (!data) {
    return undefined;
  }

  do {
    // pack three octets into four hexets
    o1 = data[i++];
    o2 = data[i++];
    o3 = data[i++];

    bits = (o1 << 16) | (o2 << 8) | o3;

    h1 = (bits >> 18) & 0x3f;
    h2 = (bits >> 12) & 0x3f;
    h3 = (bits >> 6) & 0x3f;
    h4 = bits & 0x3f;

    // use hexets to index into b64, and append result to encoded string
    tmp_arr[ac++] =
      B64.charAt(h1) + B64.charAt(h2) + B64.charAt(h3) + B64.charAt(h4);
  } while (i < data.length);

  enc = tmp_arr.join('');

  switch (data.length % 3) {
    case 1:
      enc = enc.slice(0, -2) + '==';
      break;
    case 2:
      enc = enc.slice(0, -1) + '=';
      break;
  }

  return enc;
}

/** Returns undefined if the input is null or undefined. */
export function base64_decode(data: null | undefined): undefined;
/** Returns an array of bytes from the given base64-encoded string. */
export function base64_decode(data: string): memory;
/** Returns an array of bytes from the given base64-encoded string. */
export function base64_decode(
  data: string | null | undefined,
): memory | undefined {
  // Twacked by Will Scullin to handle arrays of 'bytes'

  // http://kevin.vanzonneveld.net
  // +   original by: Tyler Akins (http://rumkin.com)
  // +   improved by: Thunder.m
  // +      input by: Aman Gupta
  // +   improved by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
  // +   bugfixed by: Onno Marsman
  // +   bugfixed by: Pellentesque Malesuada
  // +   improved by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
  // +      input by: Brett Zamir (http://brett-zamir.me)
  // +   bugfixed by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
  // -    depends on: utf8_decode
  // *     example 1: base64_decode('S2V2aW4gdmFuIFpvbm5ldmVsZA==');
  // *     returns 1: 'Kevin van Zonneveld'

  // mozilla has this native
  // - but breaks in 2.0.0.12!
  //if (typeof this.window['btoa'] == 'function') {
  //    return btoa(data);
  //}

  let o1,
    o2,
    o3,
    h1,
    h2,
    h3,
    h4,
    bits,
    i = 0,
    ac = 0;
  const tmp_arr = [];

  if (!data) {
    return undefined;
  }

  do {
    // unpack four hexets into three octets using index points in B64
    h1 = B64.indexOf(data.charAt(i++));
    h2 = B64.indexOf(data.charAt(i++));
    h3 = B64.indexOf(data.charAt(i++));
    h4 = B64.indexOf(data.charAt(i++));

    bits = (h1 << 18) | (h2 << 12) | (h3 << 6) | h4;

    o1 = (bits >> 16) & 0xff;
    o2 = (bits >> 8) & 0xff;
    o3 = bits & 0xff;

    tmp_arr[ac++] = o1;
    if (h3 !== 64) {
      tmp_arr[ac++] = o2;
    }
    if (h4 !== 64) {
      tmp_arr[ac++] = o3;
    }
  } while (i < data.length);

  return new Uint8Array(tmp_arr);
}

const DATA_URL_PREFIX = 'data:application/octet-stream;base64,';

export function base64_json_parse(json: string): unknown {
  const reviver = (_key: string, value: unknown) => {
    if (typeof value === 'string' && value.startsWith(DATA_URL_PREFIX)) {
      return base64_decode(value.slice(DATA_URL_PREFIX.length));
    }
    return value;
  };

  return JSON.parse(json, reviver);
}

export function base64_json_stringify(json: unknown) {
  const replacer = (_key: string, value: unknown) => {
    if (value instanceof Uint8Array) {
      return DATA_URL_PREFIX + base64_encode(value);
    }
    return value;
  };

  return JSON.stringify(json, replacer);
}