// This version of the crawler also

// harvests emails from webpages

import io.Source

import scala.util.matching.Regex

import scala.util._

// gets the first ~10K of a web-page

def get_page(url: String) : String = {

  Try(Source.fromURL(url).take(10000).mkString) getOrElse 

    { println(s"  Problem with: $url"); ""}

}

// staring URL for the crawler

val startURL = """http://www.inf.kcl.ac.uk/staff/urbanc/"""

// regex for URLs

val http_pattern = """\"https?://[^\"]*\"""".r

val my_urls = """urbanc""".r

val email_pattern = """([a-z0-9_\.-]+)@([\da-z\.-]+)\.([a-z\.]{2,6})""".r

// The regular expression for emails comes from: 

//    http://net.tutsplus.com/tutorials/other/8-regular-expressions-you-should-know/

def unquote(s: String) = s.drop(1).dropRight(1)

def get_all_URLs(page: String) : Set[String] = {

  http_pattern.findAllIn(page).map(unquote).toSet

}

// naive version - seraches until a given depth

// visits pages potentially more than once

def crawl(url: String, n: Int) : Unit = {

  if (n == 0) ()

  //else if (my_urls.findFirstIn(url) == None) ()

  else {

    println(s"Visiting: $n $url")

    val page = get_page(url)

    println(email_pattern.findAllIn(page).mkString("\n"))

    for (u <- get_all_URLs(page)) crawl(u, n - 1)

  }

}

crawl(startURL, 3)