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

import * as strings from '../../../vs/base/common/strings';

declare const Buffer: any;

const hasBuffer = typeof Buffer !== 'undefined';
const hasTextDecoder = typeof TextDecoder !== 'undefined';
let textDecoder: TextDecoder | null;

export class VSBuffer {
  static wrap(actual: Uint8Array): VSBuffer {
    if (hasBuffer && !Buffer.isBuffer(actual)) {
      // https://nodejs.org/dist/latest-v10.x/docs/api/buffer.html#buffer_class_method_buffer_from_arraybuffer_byteoffset_length
      // Create a zero-copy Buffer wrapper around the ArrayBuffer pointed to by the Uint8Array
      actual = Buffer.from(actual.buffer, actual.byteOffset, actual.byteLength);
    }
    return new VSBuffer(actual);
  }

  readonly buffer: Uint8Array;
  readonly byteLength: number;

  private constructor(buffer: Uint8Array) {
    this.buffer = buffer;
    this.byteLength = this.buffer.byteLength;
  }

  toString(): string {
    if (hasBuffer) {
      return this.buffer.toString();
    } else if (hasTextDecoder) {
      if (!textDecoder) {
        textDecoder = new TextDecoder();
      }
      return textDecoder.decode(this.buffer);
    } else {
      return strings.decodeUTF8(this.buffer);
    }
  }
}

export function readUInt16LE(source: Uint8Array, offset: number): number {
  return ((source[offset + 0] << 0) >>> 0) | ((source[offset + 1] << 8) >>> 0);
}

export function writeUInt16LE(
  destination: Uint8Array,
  value: number,
  offset: number
): void {
  destination[offset + 0] = value & 0b11111111;
  value = value >>> 8;
  destination[offset + 1] = value & 0b11111111;
}

export function readUInt32BE(source: Uint8Array, offset: number): number {
  return (
    source[offset] * 2 ** 24 +
    source[offset + 1] * 2 ** 16 +
    source[offset + 2] * 2 ** 8 +
    source[offset + 3]
  );
}

export function writeUInt32BE(
  destination: Uint8Array,
  value: number,
  offset: number
): void {
  destination[offset + 3] = value;
  value = value >>> 8;
  destination[offset + 2] = value;
  value = value >>> 8;
  destination[offset + 1] = value;
  value = value >>> 8;
  destination[offset] = value;
}

export function readUInt8(source: Uint8Array, offset: number): number {
  return source[offset];
}

export function writeUInt8(
  destination: Uint8Array,
  value: number,
  offset: number
): void {
  destination[offset] = value;
}