require 'dateparse'

local age = {}
 
local function isLeapYr(Year)
   if math.fmod(Year/400,1) == 0 then
      return true
   end
   
   if math.fmod(Year/4,1) == 0 and math.fmod(Year/100,1) ~= 0 then
      return true
   end
   return false
end
 
local function calcYrs(DOB)
   local _, dob = dateparse.parse(DOB)
   
   local T = os.time()
   local ageSecs = os.difftime(T, os.time{
         year = dob.year, 
         month = dob.month, 
         day = dob.day})
 
   local currY = tonumber(os.ts.date('%Y'))
   local yrs = 0
   local YRSEC = 365*24*3600
   local LPYRSEC = 366*24*3600
 
   local secs = ageSecs
   for i = dob.year, currY do
      if isLeapYr(i) then
         secs = secs - LPYRSEC
         yrs = yrs + 1
         if secs < YRSEC then
            return yrs, yrs + secs/YRSEC, secs
         end
      else
         secs = secs - YRSEC
         yrs = yrs + 1
         if isLeapYr(1 + 1) then
            if secs < LPYRSEC then
               return yrs, secs/LPYRSEC, secs
            end
            else
            if secs < YRSEC then             
               return yrs, yrs + secs/YRSEC, secs          
            end          
         end       
      end    
   end 
end 

local function calcMths(DOB)    
   local _, dob = dateparse.parse(DOB)    
   local _, currDt = dateparse.parse(os.date())    
   local ageMths    
   if currDt.month > dob.month then
      ageMths = currDt.month - dob.month
      trace(ageMths)
   elseif currDt.month == dob.month then
      ageMths = 0
      trace(ageMths)
   else
      ageMths = 12 + (currDt.month - dob.month)
   end
   return ageMths
end
  
function age.getAge(DOB)   
   -- calculate years
   local ageYrs, ageDec = calcYrs(DOB)
   -- calculate months
   local ageMths = calcMths(DOB)
   return ageYrs, ageMths, ageDec
end

local HELP_DEF=[[{
   "Desc": "Calculate age from date of birth (DOB).  Returns years, months and partial years.",
   "Returns": [{
         "Desc": "Years  <u>integer</u>"
      },
      {
         "Desc": "Months  <u>integer</u>"
      },
      {
         "Desc": "Partial years  <u>number</u>"
      }
   ],
   "SummaryLine": "Calculate age from date of birth",
   "SeeAlso": [
      {
         "Title": "age.lua - in our code repository.",
         "Link": "http://help.interfaceware.com/code/details/age-lua"
      }
   ],
   "Title": "age.getAge",
   "Usage": "local Years, Months, PartialYears = age.getAge{DOB}",
   "Parameters": [
      {
         "DOB": {
            "Desc": "Date of birth <u>string</u>. "
         }
      }
   ],
   "Examples": [
      "<pre>local Years, Months, PartialYears = age.getAge(DOB)</pre>"
   ],
   "ParameterTable": false
}]]

help.set{input_function=age.getAge, help_data=json.parse{data=HELP_DEF}}    
 
return age