dl_bms.kt

// Require kotlinx.coroutines jar as dependency, handle it yourself

import kotlinx.coroutines.experimental.async
import kotlinx.coroutines.experimental.launch
import kotlinx.coroutines.experimental.runBlocking
import java.io.FileOutputStream
import java.net.HttpURLConnection
import java.net.URL
import java.nio.channels.Channels

val base = "http://bms.bemaniso.ws/"
val file = { style: Int ->
    "$base/files.php?group=iidx&style=$style"
}

fun main(args: Array<String>) {
    val dest = "E:\\bmssong"
    runBlocking {
        (12..21).forEach {
            val style = it
            launch {
                filterDlLink(get(file(it))).forEach {
                    launch {
                        download("$base$it", dest)
                    }
                }
            }.join()
        }
    }
}

fun filterDlLink(urls: List<String>) = urls
        .filter { it.contains(".7z") }
        .map { it.split(">")[0].split("\"")[1].replace("&amp;", "&") }

suspend fun get(url: String): List<String> {
    val conn = URL(url).openConnection() as HttpURLConnection
    conn.requestMethod = "GET"
    if (conn.responseCode != 200) {
        println(conn.errorStream.bufferedReader().readLines().reduce { x, y -> x + y })
    }
    return conn.inputStream.bufferedReader().readLines()
}

suspend fun download(url: String, dest: String) {
    val conn = URL(url).openConnection() as HttpURLConnection
    val fileName = url.split("&").filter { it.contains("file=") }[0].split("=")[1]
    conn.requestMethod = "GET"
    if (conn.responseCode != 200) {
        println(conn.errorStream.bufferedReader().readLines().reduce { x, y -> x + y })
    }
    Channels.newChannel(conn.inputStream.buffered()).use {
        val rbc = it
        FileOutputStream("$dest/$fileName").use {
            it.channel.transferFrom(rbc, 0, Long.MAX_VALUE)
        }
    }
}