'use strict';

/**
 * Module exports.
 */

module.exports = dataUriToBuffer;

/**
 * Returns a `Buffer` instance from the given data URI `uri`.
 *
 * @param {String} uri Data URI to turn into a Buffer instance
 * @return {Buffer} Buffer instance from Data URI
 * @api public
 */

function dataUriToBuffer (uri) {
  if (!/^data\:/i.test(uri)) {
    throw new TypeError('`uri` does not appear to be a Data URI (must begin with "data:")');
  }

  // strip newlines
  uri = uri.replace(/\r?\n/g, '');

  // split the URI up into the "metadata" and the "data" portions
  var firstComma = uri.indexOf(',');
  if (-1 === firstComma || firstComma <= 4) throw new TypeError('malformed data: URI');

  // remove the "data:" scheme and parse the metadata
  var meta = uri.substring(5, firstComma).split(';');

  var type = meta[0] || 'text/plain';
  var typeFull = type;
  var base64 = false;
  var charset = '';
  for (var i = 1; i < meta.length; i++) {
    if ('base64' == meta[i]) {
      base64 = true;
    } else {
      typeFull += ';' + meta[i];
      if (0 == meta[i].indexOf('charset=')) {
        charset = meta[i].substring(8);
      }
    }
  }
  // defaults to US-ASCII only if type is not provided
  if (!meta[0] && !charset.length) {
    typeFull += ';charset=US-ASCII';
    charset = 'US-ASCII';
  }

  // get the encoded data portion and decode URI-encoded chars
  var data = unescape(uri.substring(firstComma + 1));

  var encoding = base64 ? 'base64' : 'ascii';
  var buffer = new Buffer(data, encoding);

  // set `.type` and `.typeFull` properties to MIME type
  buffer.type = type;
  buffer.typeFull = typeFull;

  // set the `.charset` property
  buffer.charset = charset;

  return buffer;
}
