ammonite.sshd.util.Environment.scala Maven / Gradle / Ivy

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package ammonite.sshd.util

import acyclic.file
import java.io.{InputStream, OutputStream, PrintStream}

/**
 * Container for staging environment important for Ammonite repl to run correctly.
 * @param thread a thread where execution takes place. Important for restoring contextClassLoader
 * @param contextClassLoader thread's context class loader. Ammonite repl uses that to load classes
 * @param systemIn
 * @param systemOut
 * @param systemErr
 */
case class Environment(thread: Thread,
                       contextClassLoader: ClassLoader,
                       systemIn: InputStream,
                       systemOut: PrintStream,
                       systemErr: PrintStream
)

object Environment {
  def apply(classLoader: ClassLoader, in: InputStream, out: PrintStream): Environment =
    apply(Thread.currentThread(), classLoader, in, out, out)

  def apply(classLoader: ClassLoader, in: InputStream, out: OutputStream): Environment =
    apply(classLoader, in, new PrintStream(out))


  /**
   * Collects information about current environment
   */
  def collect() = Environment(
    Thread.currentThread(),
    Thread.currentThread().getContextClassLoader,
    System.in,
    System.out,
    System.err
  )

  /**
   * Runs your code with supplied environment installed.
   * After execution of supplied code block will restore original environment
   */
  def withEnvironment(env:Environment)(code: ⇒ Any):Any = {
    val oldEnv = collect()
    try {
      install(env)
      code
    } finally {
      install(oldEnv)
    }
  }

  /**
   * Resets execution environment from parameters saved to Environment container passed in
   * @param env environment to reset to
   */
  def install(env: Environment): Unit = {
    env.thread.setContextClassLoader(env.contextClassLoader)
    System.setIn(env.systemIn)
    System.setOut(env.systemOut)
    System.setErr(env.systemErr)
  }
}