'use strict';
var inherits = require('inherits');
var Readable = require('readable-stream').Readable;

module.exports = ReadStream;
inherits(ReadStream, Readable);

function ReadStream(db, opts) {
  if (!(this instanceof ReadStream)) {
    return new ReadStream(db, opts);
  }
  Readable.call(this, {
    objectMode: true
  });
  opts = opts || {};
  var thisOpts = this.opts = {
    since: 0
  };
  Object.keys(opts).forEach(function (key) {
    thisOpts[key] = opts[key];
  });
  this.opts.returnDocs = false;
  this.last = opts.since;
  this.db = db;
  this.changes = void 0;
  this.canceled = false;
}
ReadStream.prototype._read = function () {
  if (this.changes) {
    return;
  }
  var self = this;
  this.opts.since = this.last;
  this.changes = this.db.changes(this.opts).on('complete', function (resp) {
    self.cancel = function () {};
    if (!resp.canceled) {
      self.push(null);
    }
  });
  this.changes.on('change', function (change) {
    self.last = change.seq;
    var more = self.push(change);
    if (!more) {
      self.changes.cancel();
    }
  });
};
ReadStream.prototype.cancel = function () {
  this.canceled = true;
  if (this.changes && typeof this.changes.cancel === 'function') {
    return this.changes.cancel();
  }
};