import io.Source

import scala.util.matching.Regex

// gets the first ~10K of a page

def get_page(url: String) : String = { 

  try {

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

  }

  catch {

    case e => {

      println("  Problem with: " + url)

      ""

    }

  }

}

// non-existing page -> returns the empty string

get_page("""http://www.foobar.com""")

// staring URL for the crawler

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

// starts with an "

// then either http or https

// then ://

// then any character that is not "

// finally "

val http_pattern = """\"((?:http|https)://(?:[^\"])*)\"""".r

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

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

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

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

}

// get all urls in startURL

get_all_URLs(get_page(startURL))

// number of all urls in startURL 

get_all_URLs(get_page(startURL)).toList.length

// naive version - seraches until a given depth

// visits pages potentially more than once

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

  if (n == 0) ()

  else {

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

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

  }

}

crawl(startURL, 2)

//breadth-first version without visiting 

//pages twice

def bf_crawl(todo: Set[String], visited: Set[String], n: Int) : Unit = {

  if (n == 0) ()

  else {

    val new_todo = todo.flatMap { 

      url => {

        if (visited.contains(url)) Set[String]()

        else {

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

          get_all_URLs(get_page(url))

        }

      }

    } 

    bf_crawl(new_todo, visited union todo, n - 1)

  }

}

bf_crawl(Set(startURL1), Set(), 2)

//breadth-first version without visiting 

//pages twice and only in "my" domain

val my_pattern = """urbanc""".r

// breadth first search avoiding double searches

def bf_crawl2(todo: Set[String], visited: Set[String], n: Int) : Unit = {

  if (n == 0) ()

  else {

    val new_todo = todo.flatMap { 

      url => {

        if (visited.contains(url)) Set[String]()

        else if (my_pattern.findFirstIn(url) == None) Set[String]()

        else {

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

          get_all_URLs(get_page(url))

        }

      }

    } 

    bf_crawl2(new_todo, visited union todo, n - 1)

  }

}

bf_crawl2(Set(startURL1), Set(), 5)

// email harvester

// from 

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

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

def bf_crawl3(todo: Set[String], visited: Set[String], n: Int) : Unit = {

  if (n == 0) ()

  else {

    val new_todo = todo.flatMap { 

      url => {

        if (visited.contains(url)) Set[String]()

        else {

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

          val page = get_page(url)

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

          get_all_URLs(get_page(url))

        }

      }

    } 

    bf_crawl3(new_todo, visited union todo, n - 1)

  }

}

bf_crawl3(Set(startURL1), Set(), 3)

// depth-first version does not work,

// because it might visit pages at depth 1

// while it still wants to visit them at 

// depth 2 

var visited = Set("")

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

  if (n == 0) ()

  else if (visited.contains(url)) () //println("Already visited: " + n + " " + url)

  else {

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

    visited += url

    for (u <- getAllURLs(getURLpage(url))) crawl(u, n - 1);

  }

}