#!/usr/bin/env ruby -w
# encoding: UTF-8
#
# = ProjectBroker.rb -- The TaskJuggler III Project Management Software
#
# Copyright (c) 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013
#               by Chris Schlaeger <chris@linux.com>
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of version 2 of the GNU General Public License as
# published by the Free Software Foundation.
#

require 'monitor'
require 'thread'
require 'drb'
require 'drb/acl'
require 'taskjuggler/daemon/Daemon'
require 'taskjuggler/daemon/ProjectServer'
require 'taskjuggler/TjTime'
require 'taskjuggler/MessageHandler'

class TaskJuggler

  # The ProjectBroker is the central object of the TaskJuggler daemon. It can
  # manage multiple scheduled projects that it keeps in separate sub
  # processes. Requests to a specific project will be redirected to the
  # specific ProjectServer process. Projects can be added or removed. Adding
  # an already existing one (identified by project ID) will replace the old
  # one as soon as the new one has been scheduled successfully.
  #
  # The daemon uses DRb to communicate with the client and it's sub processes.
  # The communication is restricted to localhost. All remote commands require
  # an authentication key.
  #
  # Currently only tj3client can be used to communicate with the TaskJuggler
  # daemon.
  class ProjectBroker < Daemon

    include MessageHandler

    attr_accessor :authKey, :port, :uriFile, :projectFiles, :logStdIO

    def initialize
      super
      # We don't have a default key. The user must provice a key in the config
      # file. Otherwise the daemon will not start.
      @authKey = nil
      # The default TCP/IP port. ASCII code decimals for 'T' and 'J'.
      @port = 8474
      # The name of the URI file.
      @uriFile = nil
      # A list of loaded projects as Array of ProjectRecord objects.
      @projects = []
      # We operate with multiple threads so we need a Monitor to synchronize
      # the access to the list.
      @projects.extend(MonitorMixin)

      # A list of the initial projects. Array with Array of files names.
      @projectFiles = []

      # This Queue is used to load new projects. The DRb thread pushes load
      # requests that the housekeeping thread will then perform.
      @projectsToLoad = Queue.new

      # Set this flag to true to have standard IO logged into files. There
      # will be seperate set of files for each process.
      @logStdIO = !@daemonize

      # This flag will be set to true to terminate the daemon.
      @terminate = false
    end

    def start
      # To ensure a certain level of security, the user must provide an
      # authentication key to authenticate the client to this server.
      unless @authKey
        error('pb_no_auth_key', <<'EOT'
You must set an authentication key in the configuration file. Create a file
named .taskjugglerrc or taskjuggler.rc that contains at least the following
lines. Replace 'your_secret_key' with some random character sequence.

_global:
  authKey: your_secret_key
EOT
                  )
      end

      # In daemon mode, we fork twice and only the 2nd child continues here.
      super()
      debug('', "Starting project broker")

      # Setup a DRb server to handle the incomming requests from the clients.
      brokerIface = ProjectBrokerIface.new(self)
      begin
        $SAFE = 1
        DRb.install_acl(ACL.new(%w[ deny all
                                    allow 127.0.0.1 ]))
        @uri = DRb.start_service("druby://127.0.0.1:#{@port}", brokerIface).uri
        info('daemon_uri', "TaskJuggler daemon is listening on #{@uri}")
      rescue
        error('port_in_use', "Cannot listen on port #{@port}: #{$!}")
      end

      if @port == 0 && @uriFile
        # If the port is set to 0 (any port) we save the ProjectBroker URI in
        # the file .tj3d.uri. tj3client will look for it.
        begin
          File.open(@uriFile, 'w') { |f| f.write @uri }
        rescue
          error('cannot_write_uri', "Cannot write URI file #{@uriFile}: #{$!}")
        end
      end

      # If project files were specified on the command line, we add them here.
      i = 0
      @projectFiles.each do |project|
        @projectsToLoad.push(project)
      end

      # Start a Thread that waits for the @terminate flag to be set and does
      # some other work asynchronously.
      startHousekeeping

      debug('', 'Shutting down ProjectBroker DRb server')
      DRb.stop_service

      # If we have created a URI file, we need to delete it again.
      if @port == 0 && @uriFile
        begin
          File.delete(@uriFile)
        rescue
          error('cannot_delete_uri', "Cannot delete URI file .tj3d.uri: #{$!}")
        end
      end

      info('daemon_terminated', 'TaskJuggler daemon terminated')
    end

    # All remote commands must provide the proper authentication key. Usually
    # the client and the server get this secret key from the same
    # configuration file.
    def checkKey(authKey, command)
      if authKey == @authKey
        debug('', "Accepted authentication key for command '#{command}'")
      else
        warning('wrong_auth_key',
                "Rejected wrong authentication key '#{authKey}' " +
                "for command '#{command}'")
        return false
      end
      true
    end

    # This command will initiate the termination of the daemon.
    def stop
      debug('', 'Terminating on client request')

      # Shut down the web server if we've started one.
      if @webServer
        @webServer.stop
      end

      # Send termination signal to all ProjectServer instances
      @projects.synchronize do
        @projects.each { |p| p.terminateServer }
      end

      # Setting the @terminate flag to true will case the terminator Thread to
      # call DRb.stop_service
      @terminate = true
      super
    end

    # Generate a table with information about the loaded projects.
    def status
      if @projects.empty?
        "No projects registered\n"
      else
        format = "  %3s | %-25s | %-14s | %s | %-20s\n"
        out = sprintf(format, 'No.', 'Project ID', 'Status', 'M',
                              'Loaded since')
        out += "  #{'-' * 4}+#{'-' * 27}+#{'-' * 16}+#{'-' * 3}+#{'-' * 20}\n"
        @projects.synchronize do
          i = 0
          @projects.each do |project|
            out += project.to_s(format, i += 1)
          end
        end
        out
      end
    end

    # Adding a new project or replacing an existing one. The command waits
    # until the project has been loaded or the load has failed.
    def addProject(cwd, args, stdOut, stdErr, stdIn, silent)
      # We need some tag to identify the ProjectRecord that this project was
      # associated to. Just use a large enough random number.
      tag = rand(9999999999999)

      debug('', "Pushing #{tag} to load Queue")
      @projectsToLoad.push(tag)

      # Now we have to wait until the project shows up in the @projects
      # list. We use our tag to identify the right entry.
      pr = nil
      while pr.nil?
        @projects.synchronize do
          @projects.each do |p|
            if p.tag == tag
              pr = p
              break
            end
          end
        end
        # The wait in this loop should be pretty short and we don't want to
        # miss IO from the ProjectServer process.
        sleep 0.1 unless pr
      end

      debug('', "Found tag #{tag} in list of loaded projects with URI " +
            "#{pr.uri}")

      res = false

      # Open a DRb connection to the ProjectServer process
      begin
        projectServer = DRbObject.new(nil, pr.uri)
      rescue
        warning('pb_cannot_get_ps', "Can't get ProjectServer object: #{$!}")
        return false
      end
      begin
        # Hook up IO from requestor to the ProjectServer process.
        projectServer.connect(pr.authKey, stdOut, stdErr, stdIn, silent)
      rescue
        warning('pb_cannot_connect_io', "Can't connect IO: #{$!}")
        return false
      end

      # Ask the ProjectServer to load the files in _args_ into the
      # ProjectServer.
      begin
        res = projectServer.loadProject(pr.authKey, [ cwd, *args ])
      rescue
        warning('pb_load_failed', "Loading of project failed: #{$!}")
        return false
      end

      # Disconnect the IO from the ProjectServer and close the DRb connection.
      begin
        projectServer.disconnect(pr.authKey)
      rescue
        warning('pb_cannot_disconnect_io', "Can't disconnect IO: #{$!}")
        return false
      end

      res
    end

    def removeProject(indexOrId)
      @projects.synchronize do
        # Find all projects with the IDs in indexOrId and mark them as
        # :obsolete.
        if /^[0-9]$/.match(indexOrId)
          index = indexOrId.to_i - 1
          if index >= 0 && index < @projects.length
            # If we have marked the project as obsolete, we return false to
            # indicate the double remove.
            return false if p.state == :obsolete
            @projects[index].state = :obsolete
            return true
          end
        else
          @projects.each do |p|
            if indexOrId == p.id
              # If we have marked the project as obsolete, we return false to
              # indicate the double remove.
              return false if p.state == :obsolete
              p.state = :obsolete
              return true
            end
          end
        end
      end
      false
    end

    # Return the ProjectServer URI and authKey for the project with project ID
    # _projectId_.
    def getProject(projectId)
      # Find the project with the ID args[0].
      project = nil
      @projects.synchronize do
        @projects.each do |p|
          project = p if p.id == projectId && p.state == :ready
        end
      end

      if project.nil?
        debug('', "No project with ID #{projectId} found")
        return [ nil, nil ]
      end
      [ project.uri, project.authKey ]
    end

    # Reload all projects that have modified files and are not already being
    # reloaded.
    def update
      @projects.synchronize do
        @projects.each do |project|
          if project.modified && !project.reloading
            project.reloading = true
            @projectsToLoad.push(project.files)
          end
        end
      end
    end

    # Return a list of IDs of projects that are in state :ready.
    def getProjectList
      list = []
      @projects.synchronize do
        @projects.each do |project|
          list << project.id if project.state == :ready
        end
      end
      list
    end

    def report(projectId, reportId)
      uri, key = getProject(projectId)
    end

    # This is a callback from the ProjectServer process. It's used to update
    # the current state of the ProjectServer in the ProjectRecord list.
    # _projectKey_ is the authentication key for that project. It is used to
    # idenfity the entry in the ProjectRecord list to be updated.
    def updateState(projectKey, filesOrId, state, modified)
      result = false
      if filesOrId.is_a?(Array)
        files = filesOrId
        # Use the name of the master files for now.
        id = files[1]
      elsif filesOrId.is_a?(String)
        id = filesOrId
        files = nil
      else
        id = files = nil
      end

      @projects.synchronize do
        @projects.each do |project|
          # Don't accept updates for already obsolete entries.
          next if project.state == :obsolete

          debug('', "Updating state for #{id} to #{state}")
          # Only update the record that has the matching key
          if project.authKey == projectKey
            project.id = id if id
            # An Array of [ workingDir, tjpFile, ... other tji files ]
            project.files = files if files

            # If the state is being changed from something to :ready, this is
            # now the current project for the project ID.
            if state == :ready && project.state != :ready
              # Mark other project records with same project ID as obsolete
              @projects.each do |p|
                if p != project && p.id == id
                  p.state = :obsolete
                  debug('', "Marking entry with ID #{id} as obsolete")
                end
              end
              project.readySince = TjTime.new
            end

            # Failed ProjectServers are terminated automatically. We can't
            # reach them any more.
            project.uri = nil if state == :failed

            project.state = state
            project.modified = modified
            result = true
            break
          end
        end
      end

      result
    end

    private

    def startHousekeeping
      begin
        cntr = 0
        loop do
          if @terminate
            # Give the caller a chance to properly terminate the connection.
            sleep 0.5
            break
          elsif !@projectsToLoad.empty?
            loadProject(@projectsToLoad.pop)
          else
            # Send termination command to all obsolute ProjectServer
            # objects.  To minimize the locking of @projects we collect the
            # obsolete items first.
            termList = []
            @projects.synchronize do
              @projects.each do |p|
                if p.state == :obsolete
                  termList << p
                elsif p.state == :failed
                  # Start removal of entries that didn't parse.
                  p.state = :obsolete
                end
              end
            end
            # And then send them a termination command.
            termList.each { |p| p.terminateServer }

            # Check every 10 seconds that the ProjectServer processes are
            # still alive. If not, remove them from the list.
            if (cntr += 1) > 10
              @projects.synchronize do
                @projects.each do |p|
                  unless p.ping
                    termList << p unless termList.include?(p)
                  end
                end
              end
              cntr = 0
            end

            # The housekeeping thread rarely needs to so something. Make
            # sure it's sleeping most of the time.
            sleep 1

            # Remove the obsolete records from the @projects list.
            @projects.synchronize do
              @projects.delete_if { |p| termList.include?(p) }
            end
          end
        end
      rescue => exception
        # TjRuntimeError exceptions are simply passed through.
        if exception.is_a?(TjRuntimeError)
          raise TjRuntimeError, $!
        end

        fatal('pb_housekeeping_error',
              "ProjectBroker housekeeping error: #{$!}")
      end
    end

    def loadProject(tagOrProject)
      if tagOrProject.is_a?(Array)
        tag = rand(9999999999999)
        project = tagOrProject
        # The 2nd element of the Array is the *.tjp file name.
        debug('', "Loading project #{tagOrProject[1]} with tag #{tag}")
      else
        tag = tagOrProject
        project = nil
        debug('', "Loading project for tag #{tag}")
      end
      pr = ProjectRecord.new(tag)
      ps = ProjectServer.new(@authKey, project, @logStdIO)
      # The ProjectServer can be reached via this DRb URI
      pr.uri = ps.uri
      # Method calls must be authenticated with this key
      pr.authKey = ps.authKey

      # Add the ProjectRecord to the @projects list
      @projects.synchronize do
        @projects << pr
      end
    end

  end

  # This class is the DRb interface for ProjectBroker. We only want to expose
  # these methods for remote access.
  class ProjectBrokerIface

    include MessageHandler

    def initialize(broker)
      @broker = broker
    end

    # Check the authentication key and the client/server version match.
    # The following return values can be generated:
    # 0 : authKey does not match
    # 1 : client and server versions match
    # -1 : client and server versions don't match
    def apiVersion(authKey, version)
      return 0 unless @broker.checkKey(authKey, 'apiVersion')

      version == 1 ? 1 : -1
    end

    # This function catches all unhandled exceptions in the passed block.
    def trap
      begin
        yield
      rescue => e
        # TjRuntimeError exceptions are simply passed through.
        if e.is_a?(TjRuntimeError)
          raise TjRuntimeError, $!
        end

        # Any exception here is a fata error. We try hard to terminate the DRb
        # thread and then exit the program.
        begin
          fatal('pb_crash_trap', "#{e}\n#{e.backtrace.join("\n")}\n\n" +
                "#{'*' * 79}\nYou have triggered a bug in " +
                "#{AppConfig.softwareName} version #{AppConfig.version}!\n" +
                "Please see the user manual on how to get this bug fixed!\n" +
                "#{'*' * 79}\n")
        rescue RuntimeError
          @broker.stop
        end
      end
    end

    def command(authKey, cmd, args)
      return false unless @broker.checkKey(authKey, cmd)

      trap do
        case cmd
        when :status
          @broker.status
        when :stop
          @broker.stop
        when :addProject
          # To pass the DRbObject as separate arguments we need to convert it
          # into a real Array again.
          @broker.addProject(*Array.new(args))
        when :removeProject
          @broker.removeProject(args)
        when :getProject
          @broker.getProject(args)
        when :update
          @broker.update
        else
          fatal('unknown_command', 'Unknown command #{cmd} called')
        end
      end
    end

    def getProjectList(authKey)
      return false unless @broker.checkKey(authKey, 'getProjectList')

      trap { @broker.getProjectList }
    end

    def getProject(authKey, id)
      return false unless @broker.checkKey(authKey, 'getProject')

      debug('', "PID: #{id} Class: #{id.class}")
      trap { @broker.getProject(id) }
    end

    def updateState(authKey, projectKey, id, status, modified)
      return false unless @broker.checkKey(authKey, 'updateState')

      trap { @broker.updateState(projectKey, id, status, modified) }
    end

  end

  # The ProjectRecord objects are used to manage the loaded projects. There is
  # one entry for each project in the @projects list.
  class ProjectRecord < Monitor

    include MessageHandler

    attr_accessor :authKey, :uri, :files, :id, :state, :readySince, :modified,
                  :reloading
    attr_reader :tag

    def initialize(tag)
      # Before we know the project ID we use this tag to uniquely identify the
      # project.
      @tag = tag
      # Array of [ workingDir, tjp file, ... tji files ]
      @files = nil
      # The authentication key for the ProjectServer process.
      @authKey = nil
      # The DRb URI where the ProjectServer process is listening.
      @uri = nil
      # The ID of the project.
      @id = nil
      # The state of the project. :new, :loading, :ready, :failed
      # and :obsolete are supported.
      @state = :new
      # A time stamp when the project became ready for service.
      @readySince = nil
      # True if any of the input files have been modified after the load.
      @modified = false
      # True if the reload has already been triggered.
      @reloading = false

      @projectServer = nil
    end

    def ping
      return true unless @uri

      debug('', "Sending ping to ProjectServer #{@uri}")
      begin
        @projectServer = DRbObject.new(nil, @uri) unless @projectServer
        @projectServer.ping(@authKey)
      rescue
        warning('ping_failed', "Ping failed: #{$!}")
        return false
      end
      true
    end

    # Call this function to terminate the ProjectServer.
    def terminateServer
      return unless @uri

      begin
        debug('', "Sending termination request to ProjectServer #{@uri}")
        @projectServer = DRbObject.new(nil, @uri) unless @projectServer
        @projectServer.terminate(@authKey)
      rescue
        error('proj_serv_term_failed',
              "Termination of ProjectServer failed: #{$!}")
      end
      @uri = nil
    end

    # This is used to generate the status table.
    def to_s(format, index)
      sprintf(format, index, @id, @state, @modified ? '*' : ' ',
              @readySince ? @readySince.to_s('%Y-%m-%d %H:%M:%S') : '')
    end

  end

end