1 import io.Source

     2 import scala.util.matching.Regex

     3 

     4 // gets the first ~10K of a page

     5 def get_page(url: String) : String = { 

     6   try {

     7     Source.fromURL(url).take(10000).mkString  

     8   }

     9   catch {

    10     case e => {

    11       println("  Problem with: " + url)

    12       ""

    13     }

    14   }

    15 }

    16 

    17 

    18 // regex for URLs

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

    20 

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

    22 

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

    24   (http_pattern.findAllIn(page)).map { unquote(_) }.toSet

    25 }

    26 

    27 // naive version - seraches until a given depth

    28 // visits pages potentially more than once

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

    30   if (n == 0) ()

    31   else {

    32     println("Visiting: " + n + " " + url)

    33     for (u <- get_all_URLs(get_page(url))) crawl(u, n - 1)

    34   }

    35 }

    36 

    37 // staring URL for the crawler

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

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

    40 

    41 

    42 // call on the command line 

    43 crawl(startURL, 2)

    44 

    45 crawl("""http://www.dcs.kcl.ac.uk/staff/urbanc/msc-projects-12.html""", 2)