An implementation of ls -l in Scala

LsSimulator.scala

import java.io.File
import java.nio.file.attribute.{PosixFilePermission, PosixFileAttributes}
import java.nio.file.{Files, Path}
import java.time.format.DateTimeFormatter
import java.time.{LocalDateTime, ZoneId}

/*
  A solution for assignment #1
  Nima Taheri ([email protected])
 */

class RichFile(file: Path) {

  def getPermissions = {
    val filePermissions = Files.getPosixFilePermissions(file)
    val permissionToString = Seq(
      (PosixFilePermission.OWNER_READ, "r"),
      (PosixFilePermission.OWNER_WRITE, "w"),
      (PosixFilePermission.OWNER_EXECUTE, "x"),
      (PosixFilePermission.GROUP_READ, "r"),
      (PosixFilePermission.GROUP_WRITE, "w"),
      (PosixFilePermission.GROUP_EXECUTE, "x"),
      (PosixFilePermission.OTHERS_READ, "r"),
      (PosixFilePermission.OTHERS_WRITE, "w"),
      (PosixFilePermission.OTHERS_EXECUTE, "x")
    )
    val permissions = permissionToString.map({
      case (permission, representation) if filePermissions.contains(permission) => representation
      case _ => "-"
    }).mkString
    val directory = if (file.toFile.isDirectory) "d" else "-"
    s"$directory$permissions"
  }

  def getOwner = {
    Files.readAttributes(file, classOf[PosixFileAttributes]).owner().getName
  }

  def getGroup = {
    Files.readAttributes(file, classOf[PosixFileAttributes]).group().getName
  }

  def getSize = {
    file.toFile.length.toString
  }

  def getLastModificationDate = {
    val now = LocalDateTime.now()
    val lastModificationDate = LocalDateTime.ofInstant(Files.getLastModifiedTime(file).toInstant, ZoneId.systemDefault())
    val datePattern =
      if (lastModificationDate.getYear == now.getYear)
        DateTimeFormatter.ofPattern("MMM dd HH:mm")
      else
        DateTimeFormatter.ofPattern("MMM dd  YYYY")
    lastModificationDate.format(datePattern)
  }

  def getName = {
    file.getFileName.toString
  }

}

object LsSimulator {

  def listFiles(path: String): Seq[String] = {

    def addPadding(table: Seq[Seq[String]], widths: Seq[Int]) = {
      table.map(_.zip(widths).map({
        case (column, 0) => column
        case (column, width) => s"%${width}s".format(column)
      }))
    }

    def findMaximumColumnLength(table: Seq[Seq[String]]) = {
      if (table.nonEmpty) table.head.indices.map(col => table.map(_.apply(col).length).max) else Nil
    }

    val filesData = new File(path).listFiles().toSeq
      .map(f => new RichFile(f.toPath))
      .map(rf => Seq(rf.getPermissions, rf.getOwner, rf.getGroup, rf.getSize, rf.getLastModificationDate, rf.getName))
    val columnLengths = findMaximumColumnLength(filesData).dropRight(1) :+ 0 // replace columnLength of lastItem with zero to skip right-padding on it
    addPadding(filesData, columnLengths).map(_.mkString(" "))
  }

  def main(args: Array[String]) = {
    val path = args.headOption.getOrElse(System.getenv("HOME"))
    println(listFiles(path).mkString("\n"))
  }

}