/*  Title:      Pure/System/standard_system.scala

    Author:     Makarius

Standard system operations, with basic Cygwin/Posix compatibility.

*/

package isabelle

import java.util.regex.Pattern

import java.util.Locale

import java.io.{BufferedWriter, OutputStreamWriter, FileOutputStream,

  BufferedInputStream, InputStream, FileInputStream, BufferedReader, InputStreamReader,

  File, FileFilter, IOException}

import scala.io.{Source, Codec}

import scala.util.matching.Regex

import scala.collection.mutable

object Standard_System

{

  /* UTF-8 charset */

  val charset = "UTF-8"

  def codec(): Codec = Codec(charset)

  def string_bytes(s: String): Array[Byte] = s.getBytes(charset)

  /* permissive UTF-8 decoding */

  // see also http://en.wikipedia.org/wiki/UTF-8#Description

  // overlong encodings enable byte-stuffing

  def decode_permissive_utf8(text: CharSequence): String =

  {

    val buf = new java.lang.StringBuilder(text.length)

    var code = -1

    var rest = 0

    def flush()

    {

      if (code != -1) {

        if (rest == 0 && Character.isValidCodePoint(code))

          buf.appendCodePoint(code)

        else buf.append('\uFFFD')

        code = -1

        rest = 0

      }

    }

    def init(x: Int, n: Int)

    {

      flush()

      code = x

      rest = n

    }

    def push(x: Int)

    {

      if (rest <= 0) init(x, -1)

      else {

        code <<= 6

        code += x

        rest -= 1

      }

    }

    for (i <- 0 until text.length) {

      val c = text.charAt(i)

      if (c < 128) { flush(); buf.append(c) }

      else if ((c & 0xC0) == 0x80) push(c & 0x3F)

      else if ((c & 0xE0) == 0xC0) init(c & 0x1F, 1)

      else if ((c & 0xF0) == 0xE0) init(c & 0x0F, 2)

      else if ((c & 0xF8) == 0xF0) init(c & 0x07, 3)

    }

    flush()

    buf.toString

  }

  /* basic file operations */

  def slurp(reader: BufferedReader): String =

  {

    val output = new StringBuilder(100)

    var c = -1

    while ({ c = reader.read; c != -1 }) output += c.toChar

    reader.close

    output.toString

  }

  def slurp(stream: InputStream): String =

    slurp(new BufferedReader(new InputStreamReader(stream, charset)))

  def read_file(file: File): String = slurp(new FileInputStream(file))

  def write_file(file: File, text: CharSequence)

  {

    val writer = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(file), charset))

    try { writer.append(text) }

    finally { writer.close }

  }

  def with_tmp_file[A](prefix: String)(body: File => A): A =

  {

    val file = File.createTempFile(prefix, null)

    file.deleteOnExit

    try { body(file) } finally { file.delete }

  }

  // FIXME handle (potentially cyclic) directory graph

  def find_files(start: File, ok: File => Boolean): List[File] =

  {

    val files = new mutable.ListBuffer[File]

    val filter = new FileFilter { def accept(entry: File) = entry.isDirectory || ok(entry) }

    def find_entry(entry: File)

    {

      if (ok(entry)) files += entry

      if (entry.isDirectory) entry.listFiles(filter).foreach(find_entry)

    }

    find_entry(start)

    files.toList

  }

  /* shell processes */

  def raw_execute(cwd: File, env: Map[String, String], redirect: Boolean, args: String*): Process =

  {

    val cmdline = new java.util.LinkedList[String]

    for (s <- args) cmdline.add(s)

    val proc = new ProcessBuilder(cmdline)

    if (cwd != null) proc.directory(cwd)

    if (env != null) {

      proc.environment.clear

      for ((x, y) <- env) proc.environment.put(x, y)

    }

    proc.redirectErrorStream(redirect)

    proc.start

  }

  def process_output(proc: Process): (String, Int) =

  {

    proc.getOutputStream.close

    val output = slurp(proc.getInputStream)

    val rc =

      try { proc.waitFor }

      finally {

        proc.getInputStream.close

        proc.getErrorStream.close

        proc.destroy

        Thread.interrupted

      }

    (output, rc)

  }

  def raw_exec(cwd: File, env: Map[String, String], redirect: Boolean, args: String*)

    : (String, Int) = process_output(raw_execute(cwd, env, redirect, args: _*))

}

class Standard_System

{

  val platform_root = if (Platform.is_windows) Cygwin.check_root() else "/"

  override def toString = platform_root

  /* jvm_path */

  private val Cygdrive = new Regex("/cygdrive/([a-zA-Z])($|/.*)")

  private val Named_Root = new Regex("//+([^/]*)(.*)")

  def jvm_path(posix_path: String): String =

    if (Platform.is_windows) {

      val result_path = new StringBuilder

      val rest =

        posix_path match {

          case Cygdrive(drive, rest) =>

            result_path ++= (drive + ":" + File.separator)

            rest

          case Named_Root(root, rest) =>

            result_path ++= File.separator

            result_path ++= File.separator

            result_path ++= root

            rest

          case path if path.startsWith("/") =>

            result_path ++= platform_root

            path

          case path => path

        }

      for (p <- rest.split("/") if p != "") {

        val len = result_path.length

        if (len > 0 && result_path(len - 1) != File.separatorChar)

          result_path += File.separatorChar

        result_path ++= p

      }

      result_path.toString

    }

    else posix_path

  /* posix_path */

  private val Platform_Root = new Regex("(?i)" +

    Pattern.quote(platform_root) + """(?:\\+|\z)(.*)""")

  private val Drive = new Regex("""([a-zA-Z]):\\*(.*)""")

  def posix_path(jvm_path: String): String =

    if (Platform.is_windows) {

      jvm_path.replace('/', '\\') match {

        case Platform_Root(rest) => "/" + rest.replace('\\', '/')

        case Drive(letter, rest) =>

          "/cygdrive/" + letter.toLowerCase(Locale.ENGLISH) +

            (if (rest == "") "" else "/" + rest.replace('\\', '/'))

        case path => path.replace('\\', '/')

      }

    }

    else jvm_path

  /* this_java executable */

  def this_java(): String =

  {

    val java_home = System.getProperty("java.home")

    val java_exe =

      if (Platform.is_windows) new File(java_home + "\\bin\\java.exe")

      else new File(java_home + "/bin/java")

    if (!java_exe.isFile) error("Expected this Java executable: " + java_exe.toString)

    posix_path(java_exe.getAbsolutePath)

  }

}