src/main/java/li/cil/oc/UpdateCheck.scala

package li.cil.oc

import argo.jdom.JdomParser
import cpw.mods.fml.common.Loader
import cpw.mods.fml.common.versioning.ComparableVersion
import java.io.InputStreamReader
import java.net.{HttpURLConnection, URL}
import java.util.logging.Level
import net.minecraft.entity.player.EntityPlayerMP
import net.minecraft.util.ChatMessageComponent
import scala.collection.convert.WrapAsScala._

object UpdateCheck {
  val releasesUrl = new URL("https://api.github.com/repos/MightyPirates/OpenComputers/releases")

  val version = Loader.instance.getIndexedModList.get("OpenComputers").getVersion
  val majorVersion = version.split('.')(0).toInt

  // Lazy to make initialize() execute once from the first thread that tries to
  // read it. If other threads are spawned while it's running they will wait,
  // because lazy initializers are synchronized.
  lazy val result = initialize()

  def checkForPlayer(player: EntityPlayerMP) = if (Settings.get.updateCheck) {
    new Thread() {
      override def run() = result(player)
    }.start()
  }

  def initialize(): EntityPlayerMP => Unit = {
    try {
      OpenComputers.log.info("Starting version check.")
      releasesUrl.openConnection match {
        case conn: HttpURLConnection =>
          conn.setRequestMethod("GET")
          conn.setDoOutput(false)
          val json = new JdomParser().parse(new InputStreamReader(conn.getInputStream))
          val candidates = json.getElements.filter(node => matchesVersion(node.getStringValue("tag_name")) && !node.getBooleanValue("prerelease"))
          if (candidates.nonEmpty) {
            val newest = candidates.maxBy(node => new ComparableVersion(node.getStringValue("tag_name").stripPrefix("v")))
            val tag = newest.getStringValue("tag_name")
            val tagVersion = new ComparableVersion(tag.stripPrefix("v"))
            val modVersion = new ComparableVersion(version)
            if (tagVersion.compareTo(modVersion) > 0) {
              OpenComputers.log.info(s"A newer version is available: ($tag})")
              return (player: EntityPlayerMP) =>
                player.sendChatToPlayer(ChatMessageComponent.createFromText("§aOpenComputers§f: ").addFormatted(Settings.namespace + "gui.Chat.NewVersion", tag))
            }
          }
          OpenComputers.log.info("Running the latest version.")
        case _ => OpenComputers.log.warning("Failed to connect to Github.")
      }
    }
    catch {
      case t: Throwable => OpenComputers.log.log(Level.WARNING, "Update check failed.", t)
    }
    // Nothing to do, return dummy callback.
    p =>
  }

  def matchesVersion(tag: String) = try {
    tag.stripPrefix("v").split('.')(0).toInt == majorVersion
  }
  catch {
    case _: Throwable => false
  }

}