var http = require('http');
var fs = require('fs');
 
function Mzitu(options) {
  this.id = 1;
   
  this.initialize.call(this, options);
  return this;
}
 
Mzitu.prototype = {
  constructor: Mzitu,
  initialize: function _initialize(options) {
    this.baseUrl = options.baseUrl;
    this.dir = options.dir || '';
    this.reg = options.reg;
    this.total = options.total;
    this.page = options.from || 1;
  },
  start: function _start() {
    this.getPage();
  },
  getPage: function _getPage() {
    var self = this,
      data = null;
 
    if (this.page <= this.total) {
      http.get(this.baseUrl + this.page, function (res) {
        res.setEncoding("utf8");
 
        res.on('data', function (chunk) {
          data += chunk;
        }).on('end', function () {
          self.parseData(data);
        });
      });
    }
  },
  parseData: function _parseData(data) {
    var res = [],
      match;
 
    while ((match = this.reg.exec(data)) != null) {
      res.push(match[1]);
    }
 
    this.download(res);
  },
  download: function _download(resource) {
    var self = this,
      currentPage = self.page;
 
    resource.forEach(function (src, idx) {
      var filename = src.substring(src.lastIndexOf('/') + 1),
        writestream = fs.createWriteStream(self.dir + filename);
       
      http.get(src, function (res) {
        res.pipe(writestream);
      });
 
      writestream.on('finish', function () {
        console.log('page: ' + currentPage + ' id: ' + self.id++ + ' download: ' + filename);
      });
    });
     
    self.page++;
    self.getPage();
  }
};

var mzitu = new Mzitu({
  baseUrl: 'http://www.mzitu.com/share/comment-page-',
  dir: '',
  reg: /<img\s*src="(.*?)"\s*alt=".*"\s*\/>/g,
  total: 141,
  from: 1
});
 
mzitu.start();