Add progress bars for checking and downloading libs in Bootstrap Launcher

bootstrap/build.sbt

@@ -3,4 +3,5 @@ version := "0.1"
 assemblyJarName in assembly := "ChatOverflow.jar"
 
 libraryDependencies += "org.scala-lang.modules" %% "scala-xml" % "1.1.1"
+libraryDependencies += "org.jline" % "jline-terminal-jansi" % "3.11.0" // used for terminal width
 fork := true

bootstrap/src/main/scala/Bootstrap.scala

@@ -125,25 +125,39 @@ object Bootstrap {
     * @return false, if there is a serious problem
     */
   private def downloadMissingLibraries(dependencies: List[(String, String)]): Boolean = {
+    val pb = new ProgressBar(dependencies.length)
+
     // using par here to make multiple http requests in parallel, otherwise its awfully slow on internet connections with high RTTs
-    val missing = dependencies.par.filterNot(dep => isLibraryDownloaded(dep._2)).toList
+    val missing = dependencies.par.filterNot(dep => {
+      val (name, url) = dep
+      pb.countUp()
+      pb.updateDescription(s"$name@$url")
+
+      isLibraryDownloaded(url)
+    }).toList
+
+    pb.finish()
 
     if (missing.isEmpty) {
       println("All required libraries are already downloaded.")
     } else {
       println(s"Downloading ${missing.length} missing libraries...")
 
-      for (i <- missing.indices) {
-        val (name, url) = missing(i)
+      val pb = new ProgressBar(missing.length)
+
+      for ((name, url) <- missing) {
+        pb.countUp()
+        pb.updateDescription(s"$name@$url")
 
-        println(s"[${i + 1}/${missing.length}] $name ($url)")
         if (!downloadLibrary(name, url)) {
           // Second try, just in case
           if (!downloadLibrary(name, url)) {
             return false // error has been displayed, stop bootstrapper from starting with missing lib
           }
         }
       }
+
+      pb.finish()
     }
     true // everything went fine
   }

bootstrap/src/main/scala/ProgressBar.scala

@@ -0,0 +1,95 @@
+import org.jline.terminal.TerminalBuilder
+
+/**
+  * Progress bar used reporting the status while checking and downloading libs.
+  *
+  * @param max count of events e.g. length of the list which progress is monitored.
+  */
+class ProgressBar(max: Int) {
+  // Width of the terminal, used for size calculations
+  private val width = {
+    val width = TerminalBuilder.builder().dumb(true).build().getWidth
+
+    // Size couldn't be figured out, use a default
+    if (width <= 10)
+      80
+    else
+      width
+  }
+
+  private var count = 0
+  private var description = ""
+
+  // We need to create a empty line so that latest line before creation won't be overwritten by the draw method.
+  println()
+  draw() // Initial draw
+
+  /**
+    * Increases count by 1 and re-draws the progress bar with the updated count.
+    */
+  def countUp(): Unit = {
+    // Thread-safeness when working with parallel collections
+    count.synchronized {
+      count += 1
+      draw()
+    }
+  }
+
+  /**
+    * Updates the description and re-draws the description line.
+    * @param desc the new description
+    */
+  def updateDescription(desc: String): Unit = {
+    // Thread-safeness when working with parallel collections
+    description.synchronized {
+      description = desc
+      drawDescription()
+    }
+  }
+
+  /**
+    * Deletes the description to result in a blank line. The progress bar will still be visible.
+    * After this you can normally print at the beginning of a new line and don't start at the end of the description.
+    */
+  def finish(): Unit = {
+    description = ""
+    drawDescription()
+  }
+
+  /**
+    * Draws the progress bar in the line above the current one.
+    */
+  private def draw(): Unit = {
+    val barWidth = width - 16 // Width of the bar without percentage and counts
+    val percentage = count * 100 / max
+    val equalsSigns = "=" * (barWidth * percentage / 100)
+    val whiteSpaces = " " * (barWidth - equalsSigns.length)
+
+    val content = "%3d%% (%2d|%2d) [%s]".format(percentage, count, max, equalsSigns + ">" + whiteSpaces)
+
+    print(s"\033[1A\r$content\n")
+    //          |   |    |    |
+    // Go up 1 line |    |    |
+    //   Go to beginning of line
+    //                   |    |
+    //          Actual progress bar
+    //                        |
+    //            Go back down for description
+  }
+
+  /**
+    * Draws the description which is located in the current line.
+    */
+  private def drawDescription(): Unit = {
+    // Cap the description at the width of the terminal, otherwise a new line is created and everything would shift.
+    // If the user needs to see a really long url he can just widen his terminal.
+    val content = description.take(width)
+
+    print(s"\r\033[0K$content")
+    //      |     |
+    // Go to beginning
+    //            |
+    // Clear from cursor to end of the line
+  }
+
+}