advance a date object and deliver obis-common style

advance_date.coffee

# advances date x days and formats as if it is coming from                                                
# obis-common date validated attributes YYYY-MM-DD                                                        
# clones the passed in date such to avoid mutating the original.                                          
advance_date: (date, days=0)->
  assert date instanceof Date, "date needs to be a Date object"
  assert typeof days == 'number', "days need to be an Integer"
  d = new Date(date)
  d.setDate(d.getDate() + days)
  cast_by_two = (v)->
    if v < 10 then "0#{v}" else v
  "#{d.getFullYear()}-#{cast_by_two(d.getMonth() + 1)}-#{cast_by_two(d.getDate())}"

# random date between Jan 1, 2011 and the current day                                                                                                                                        
# formatted like obis-common would return from an obis-common date attribute                                                                                                                 
# (not timestamp)                                                                                                                                                                            
date: ->
  cast_by_two = (v)->
    if v < 10 then "0#{v}" else v
  randomDate = (start, end)->
    new Date start.getTime() + Math.random() * (end.getTime() - start.getTime())
  d = randomDate(new Date(2011,0,1), new Date())
  "#{d.getFullYear()}-#{cast_by_two(d.getMonth() + 1)}-#{cast_by_two(d.getDate())}"