/* sbt -- Simple Build Tool
 * Copyright 2010 Mark Harrah
package sbt

import java.io.{ File, PrintWriter }

 * Provides the current global logging configuration.
 * `full` is the current global logger.  It should not be set directly because it is generated as needed from `backing.newLogger`.
 * `console` is where all logging from all ConsoleLoggers should go.
 * `backed` is the Logger that other loggers should feed into.
 * `backing` tracks the files that persist the global logging.
 * `newLogger` creates a new global logging configuration from a sink and backing configuration.
final case class GlobalLogging(full: Logger, console: ConsoleOut, backed: AbstractLogger, backing: GlobalLogBacking, newLogger: (PrintWriter, GlobalLogBacking) => GlobalLogging)

 * Tracks the files that persist the global logging.
 * `file` is the current backing file.  `last` is the previous backing file, if there is one.
 * `newBackingFile` creates a new temporary location for the next backing file.
final case class GlobalLogBacking(file: File, last: Option[File], newBackingFile: () => File) {
  /** Shifts the current backing file to `last` and sets the current backing to `newFile`. */
  def shift(newFile: File) = GlobalLogBacking(newFile, Some(file), newBackingFile)

  /** Shifts the current backing file to `last` and sets the current backing to a new temporary file generated by `newBackingFile`. */
  def shiftNew() = shift(newBackingFile())

   * If there is a previous backing file in `last`, that becomes the current backing file and the previous backing is cleared.
   * Otherwise, no changes are made.
  def unshift = GlobalLogBacking(last getOrElse file, None, newBackingFile)
object GlobalLogBacking {
  def apply(newBackingFile: => File): GlobalLogBacking = GlobalLogBacking(newBackingFile, None, newBackingFile _)
object GlobalLogging {
  def initial(newLogger: (PrintWriter, GlobalLogBacking) => GlobalLogging, newBackingFile: => File, console: ConsoleOut): GlobalLogging =
      val log = ConsoleLogger(console)
      GlobalLogging(log, console, log, GlobalLogBacking(newBackingFile), newLogger)