# encoding: utf-8

module Backup
  class Model
    include Backup::CLI::Helpers

    ##
    # The trigger is used as an identifier for
    # initializing the backup process
    attr_accessor :trigger

    ##
    # The label is used for a more friendly user output
    attr_accessor :label

    ##
    # The databases attribute holds an array of database objects
    attr_accessor :databases

    ##
    # The archives attr_accessor holds an array of archive objects
    attr_accessor :archives

    ##
    # The encryptors attr_accessor holds an array of encryptor objects
    attr_accessor :encryptors

    ##
    # The compressors attr_accessor holds an array of compressor objects
    attr_accessor :compressors

    ##
    # The notifiers attr_accessor holds an array of notifier objects
    attr_accessor :notifiers

    ##
    # The storages attribute holds an array of storage objects
    attr_accessor :storages

    ##
    # The syncers attribute holds an array of syncer objects
    attr_accessor :syncers

    ##
    # The chunk_size attribute holds the size of the chunks in megabytes
    attr_accessor :chunk_size

    ##
    # The time when the backup initiated (in format: 2011.02.20.03.29.59)
    attr_accessor :time

    class << self
      ##
      # The Backup::Model.all class method keeps track of all the models
      # that have been instantiated. It returns the @all class variable,
      # which contains an array of all the models
      attr_accessor :all

      ##
      # Contains the current file extension (this changes from time to time after a file
      # gets compressed or encrypted so we can keep track of the correct file when new
      # extensions get appended to the current file name)
      attr_accessor :extension

      ##
      # Contains the currently-in-use model. This attribute should get set by Backup::Finder.
      # Use Backup::Model.current to retrieve the actual data of the model
      attr_accessor :current

      ##
      # Contains an array of chunk suffixes for a given file
      attr_accessor :chunk_suffixes

      ##
      # Returns the full path to the current file (including the current extension).
      # To just return the filename and extension without the path, use File.basename(Backup::Model.file)
      def file
        File.join(TMP_PATH, "#{ TIME }.#{ TRIGGER }.#{ Backup::Model.extension }")
      end

      ##
      # Returns the @chunk_suffixes variable, sets it to an emtpy array if nil
      def chunk_suffixes
        @chunk_suffixes ||= Array.new
      end

      ##
      # Returns the temporary trigger path of the current model
      # e.g. /Users/Michael/tmp/backup/my_trigger
      def tmp_path
        File.join(TMP_PATH, TRIGGER)
      end
    end

    ##
    # Accessible through "Backup::Model.all", it stores an array of Backup::Model instances.
    # Everytime a new Backup::Model gets instantiated it gets pushed into this array
    @all = Array.new

    ##
    # Contains the current file extension (should change after each compression or encryption)
    @extension = 'tar'

    ##
    # Takes a trigger, label and the configuration block and instantiates the model.
    # The TIME (time of execution) gets stored in the @time attribute.
    # After the instance has evaluated the configuration block and properly set the
    # configuration for the model, it will append the newly created "model" instance
    # to the @all class variable (Array) so it can be accessed by Backup::Finder
    # and any other location
    def initialize(trigger, label, &block)
      @trigger     = trigger
      @label       = label
      @time        = TIME

      procedure_instance_variables.each do |variable|
        instance_variable_set(variable, Array.new)
      end

      instance_eval(&block)
      Backup::Model.all << self
    end

    ##
    # Adds a database to the array of databases
    # to dump during the backup process
    def database(database, &block)
      @databases << Backup::Database.const_get(
        last_constant(database)
      ).new(&block)
    end

    ##
    # Adds an archive to the array of archives
    # to store during the backup process
    def archive(name, &block)
      @archives << Backup::Archive.new(name, &block)
    end

    ##
    # Adds an encryptor to the array of encryptors
    # to use during the backup process
    def encrypt_with(name, &block)
      @encryptors << Backup::Encryptor.const_get(
        last_constant(name)
      ).new(&block)
    end

    ##
    # Adds a compressor to the array of compressors
    # to use during the backup process
    def compress_with(name, &block)
      @compressors << Backup::Compressor.const_get(
        last_constant(name)
      ).new(&block)
    end

    ##
    # Adds a notifier to the array of notifiers
    # to use during the backup process
    def notify_by(name, &block)
      @notifiers << Backup::Notifier.const_get(
        last_constant(name)
      ).new(&block)
    end

    ##
    # Adds a storage method to the array of storage
    # methods to use during the backup process
    def store_with(storage, storage_id = nil, &block)
      @storages << Backup::Storage.const_get(
        last_constant(storage)
      ).new(storage_id, &block)
    end

    ##
    # Adds a syncer method to the array of syncer
    # methods to use during the backup process
    def sync_with(syncer, &block)
      @syncers << Backup::Syncer.const_get(
        last_constant(syncer)
      ).new(&block)
    end

    ##
    # Adds a method that allows the user to set the @chunk_size.
    # The chunk_size (in megabytes) will later determine in how many chunks the
    # backup needs to be split
    def split_into_chunks_of(chunk_size = nil)
      @chunk_size = chunk_size
    end

    ##
    # Returns the path to the current file (including proper extension)
    def file
      Backup::Model.file
    end

    ##
    # Performs the backup process
    ##
    # [Databases]
    # Runs all (if any) database objects to dump the databases
    ##
    # [Archives]
    # Runs all (if any) archive objects to package all their
    # paths in to a single tar file and places it in the backup folder
    ##
    # [Packaging]
    # After all the database dumps and archives are placed inside
    # the folder, it'll make a single .tar package (archive) out of it
    ##
    # [Encryption]
    # Optionally encrypts the packaged file with one or more encryptors
    ##
    # [Compression]
    # Optionally compresses the packaged file with one or more compressors
    ##
    # [Splitting]
    # Optionally splits the backup file in to multiple smaller chunks before transferring them
    ##
    # [Storages]
    # Runs all (if any) storage objects to store the backups to remote locations
    # and (if configured) it'll cycle the files on the remote location to limit the
    # amount of backups stored on each individual location
    ##
    # [Syncers]
    # Runs all (if any) sync objects to store the backups to remote locations.
    # A Syncer does not go through the process of packaging, compressing, encrypting backups.
    # A Syncer directly transfers data from the filesystem to the remote location
    ##
    # [Notifiers]
    # Runs all (if any) notifier objects when a backup proces finished with or without
    # any errors.
    ##
    # [Cleaning]
    # After the whole backup process finishes, it'll go ahead and remove any temporary
    # file that it produced. If an exception(error) is raised during this process which
    # breaks the process, it'll always ensure it removes the temporary files regardless
    # to avoid mass consumption of storage space on the machine
    def perform!
      if databases.any? or archives.any?
        procedures.each do |procedure|
          (procedure.call; next) if procedure.is_a?(Proc)
          procedure.each(&:perform!)
        end
      end

      syncers.each(&:perform!)
      notifiers.each { |n| n.perform!(self) }

    rescue Exception => err
      fatal = !err.is_a?(StandardError)

      Logger.error Backup::Errors::ModelError.wrap(err, <<-EOS)
        Backup for #{label} (#{trigger}) Failed!
        An Error occured which has caused this Backup to abort before completion.
        Please review the Log for this Backup to determine if steps need to be taken
        to clean up, based on the point at which the failure occured.
      EOS
      Logger.error "\nBacktrace:\n" + err.backtrace.join("\n\s\s") + "\n\n"

      if fatal
        Logger.error Backup::Errors::ModelError.new(<<-EOS)
          This Error was Fatal and Backup will now exit.
          If you have other Backup jobs (triggers) configured to run,
          they will not be processed.
        EOS
      else
        Logger.message Backup::Errors::ModelError.new(<<-EOS)
          If you have other Backup jobs (triggers) configured to run,
          Backup will now attempt to continue...
        EOS
      end

      notifiers.each do |n|
        begin
          n.perform!(self, err)
        rescue Exception; end
      end

      exit(1) if fatal
    ensure
      clean!
    end

  private

    ##
    # After all the databases and archives have been dumped and sorted,
    # these files will be bundled in to a .tar archive (uncompressed) so it
    # becomes a single (transferrable) packaged file.
    def package!
      Backup::Packager.new(self).package!
    end

    ##
    # Create a new instance of Backup::Splitter,
    # passing it the current model instance and runs it.
    def split!
      Backup::Splitter.new(self).split!
    end

    ##
    # Cleans up the temporary files that were created after the backup process finishes
    def clean!
      Backup::Cleaner.new(self).clean!
    end

    ##
    # Returns an array of procedures
    def procedures
      Array.new([
        databases, archives, lambda { package! }, compressors,
        encryptors, lambda { split! }, storages
      ])
    end

    ##
    # Returns an Array of the names (String) of the procedure instance variables
    def procedure_instance_variables
      [:@databases, :@archives, :@encryptors, :@compressors, :@storages, :@notifiers, :@syncers]
    end

    ##
    # Returns the string representation of the last value of a nested constant
    # example: last_constant(Backup::Model::MySQL) becomes and returns "MySQL"
    def last_constant(constant)
      constant.to_s.split("::").last
    end

  end
end