‘use strict’;

const { EMPTY_BUFFER } = require(‘./constants’);

/**

* Merges an array of buffers into a new buffer.
*
* @param {Buffer[]} list The array of buffers to concat
* @param {Number} totalLength The total length of buffers in the list
* @return {Buffer} The resulting buffer
* @public
*/

function concat(list, totalLength) {

if (list.length === 0) return EMPTY_BUFFER;
if (list.length === 1) return list[0];

const target = Buffer.allocUnsafe(totalLength);
let offset = 0;

for (let i = 0; i < list.length; i++) {
  const buf = list[i];
  target.set(buf, offset);
  offset += buf.length;
}

if (offset < totalLength) return target.slice(0, offset);

return target;

}

/**

* Masks a buffer using the given mask.
*
* @param {Buffer} source The buffer to mask
* @param {Buffer} mask The mask to use
* @param {Buffer} output The buffer where to store the result
* @param {Number} offset The offset at which to start writing
* @param {Number} length The number of bytes to mask.
* @public
*/

function _mask(source, mask, output, offset, length) {

for (let i = 0; i < length; i++) {
  output[offset + i] = source[i] ^ mask[i & 3];
}

}

/**

* Unmasks a buffer using the given mask.
*
* @param {Buffer} buffer The buffer to unmask
* @param {Buffer} mask The mask to use
* @public
*/

function _unmask(buffer, mask) {

// Required until https://github.com/nodejs/node/issues/9006 is resolved.
const length = buffer.length;
for (let i = 0; i < length; i++) {
  buffer[i] ^= mask[i & 3];
}

}

/**

* Converts a buffer to an `ArrayBuffer`.
*
* @param {Buffer} buf The buffer to convert
* @return {ArrayBuffer} Converted buffer
* @public
*/

function toArrayBuffer(buf) {

if (buf.byteLength === buf.buffer.byteLength) {
  return buf.buffer;
}

return buf.buffer.slice(buf.byteOffset, buf.byteOffset + buf.byteLength);

}

/**

* Converts `data` to a `Buffer`.
*
* @param {*} data The data to convert
* @return {Buffer} The buffer
* @throws {TypeError}
* @public
*/

function toBuffer(data) {

toBuffer.readOnly = true;

if (Buffer.isBuffer(data)) return data;

let buf;

if (data instanceof ArrayBuffer) {
  buf = Buffer.from(data);
} else if (ArrayBuffer.isView(data)) {
  buf = Buffer.from(data.buffer, data.byteOffset, data.byteLength);
} else {
  buf = Buffer.from(data);
  toBuffer.readOnly = false;
}

return buf;

}

try {

const bufferUtil = require('bufferutil');
const bu = bufferUtil.BufferUtil || bufferUtil;

module.exports = {
  concat,
  mask(source, mask, output, offset, length) {
    if (length < 48) _mask(source, mask, output, offset, length);
    else bu.mask(source, mask, output, offset, length);
  },
  toArrayBuffer,
  toBuffer,
  unmask(buffer, mask) {
    if (buffer.length < 32) _unmask(buffer, mask);
    else bu.unmask(buffer, mask);
  }
};

} catch (e) /* istanbul ignore next */ {

module.exports = {
  concat,
  mask: _mask,
  toArrayBuffer,
  toBuffer,
  unmask: _unmask
};

}