'use strict';

Object.defineProperty(exports, "__esModule", {
  value: true
});

var _stream = require('stream');

class OverflowError extends Error {}

class MeterSream extends _stream.Transform {
  constructor() {
    let maxSize = arguments.length <= 0 || arguments[0] === undefined ? Infinity : arguments[0];

    super();
    this.maxSize = maxSize;
    this.byteCount = 0;
  }
  _transform(chunk, encoding, cb) {
    // if this is called, _flush isn't called
    if (this.err) return cb(this.err);
    if (this.maxSize === Infinity) return cb(null, chunk);
    this.byteCount += chunk.length;
    if (this.byteCount > this.maxSize) {
      const remainingBytes = this.maxSize - this.byteCount;
      const lastChunk = chunk.slice(0, remainingBytes);
      this.err = new OverflowError(`Stream exceeded specified max of ${ this.maxSize } bytes.`);
      // flush remaining chunk and wait until next
      // _transform or _flush call to emit error
      return cb(null, lastChunk);
    }
    cb(null, chunk);
  }
  // if error detected on last call to _transform
  // flush will be called with the error
  _flush(cb) {
    cb(this.err);
  }
}
MeterSream.OverflowError = OverflowError;

exports.default = MeterSream;