FetchCodeforcesTags

package com.bogdan.codeforceswatcher.util

import kotlinx.coroutines.GlobalScope
import kotlinx.coroutines.launch
import java.io.BufferedReader
import java.io.InputStreamReader
import java.net.HttpURLConnection
import java.net.URL
import java.sql.DriverManager.println
import java.util.*
import java.util.regex.Pattern

/*
 * hello,karankapoor:)
 * I am AnswerNotFound.
 * this Java program helps you find all tags in codeforces
 */
object FindAllTags {

    private val set = HashSet<String>()

    fun getContent(urlString: String): String {
        println("getContent")
        val url = URL(urlString)
        val urlConnection = url.openConnection() as HttpURLConnection
        val reader = BufferedReader(InputStreamReader(urlConnection.inputStream))
        var line: String?
        var ans = ""
        line = reader.readLine()
        while (line != null) {
            ans += line + "\n"
            line = reader.readLine()
        }
        return ans
    }

    fun getKeywords(content: String): ArrayList<String> {
        println("getKeywords")
        val list = ArrayList<String>()
        val pattern = Pattern.compile("<a href=\"/problemset?tags=[^,]")
        val matcher = pattern.matcher(content)
        while (matcher.find()) {
            var tag = matcher.group()
            tag = tag.substring(26, tag.length - 1)
            list.add(tag)
        }
        return list
    }

    @Throws(Exception::class)
    fun solve() {
        //GlobalScope.launch {
        val lastPage = "<a href=\"/problemset/problem/1/A\">"
        for (i in 1..1000) {
            val urlString = "http://codeforces.com/problemset/page/$i"
            val content = getContent(urlString)
            val list = getKeywords(content)
            for (s in list) {
                set.add(s)
            }
            if (content.contains(lastPage)) {
                kotlin.io.println("page stop at $i");
                break
            }
            println("i $i")
        }

        kotlin.io.println("here are " + set.size + " tags on codeforces now. they are:")
        for (tag in set) {
            print("$tag,")
        }
        //}
    }

    @JvmStatic
    fun main(args: Array<String>) {
        solve()
    }
}