backup '/home/russ/documents'
backup '/home/russ/music', file_name('*.mp3') & file_name('*.wav')
backup '/home/russ/images', except(file_name('*.tmp'))
to '/external_drive/backups'

interval 60

require 'finder'
require 'find'

class Expression
  def |(other)
    Or.new(self, other)
  end

  def &(other)
    And.new(self, other)
  end
end

class All < Expression
  def evaluate(dir)
    results = []
    Find.find(dir) do |p|
      next unless File.file?(p)
      results << p
    end
    results
  end
end

class And < Expression
  def initialize(expression1, expression2)
    @expression1 = expression1
    @expression2 = expression2
  end

  def evaluate(dir)
    result1 = @expression1.evaluate(dir)
    result2 = @expression2.evaluate(dir)
    (result1 & result2)
  end
end

class Not < Expression
  def initialize(expression)
    @expression = expression
  end

  def evaluate(dir)
    All.new.evaluate(dir) - @expression.evaluate(dir)
  end
end

class FileName < Expression
  def initialize(pattern)
    @pattern = pattern
  end

  def evaluate(dir)
    results = []
    Find.find(dir) do |p|
      next unless File.file?(p)
      name = File.basename(p)
      results << p if File.fnmatch(@pattern, name)
    end
    results
  end
end

def backup(dir, find_expression=All.new)
  puts "Backup called, source dir=#{dir} find expr=#{find_expression}"
end

def to(backup_directory)
  puts "To called, backup dir=#{backup_directory}"
end

def interval(minutes)
  puts "Interval called, interval = #{minutes} minutes"
end

def except(expression)
  Not.new(expression)
end

def file_name(pattern)
  FileName.new(pattern)
end

eval(File.read('backup.pr'))