#!/bin/sh
#######################################################################
# Program Name:  adddays.sh
# Purpose:  calculate date ahead or behind by X days
# Written by: J. David Schronce
# Creation Date: 03/03/2000
#######################################################################
# 3/29/2007 - JDS - replace complex leapyear and DOM calculations
#             with call to 'cal'
#
#set -xv
USAGE="
$0 USAGE:[-]number_of_days [start_date in YYYY MM DD format]
(where number_of_days between 365 and -365)\n\n
Example: \n
$0 -7 will return the date one week ago\n
$0 90 will return the date in 90 days\n
$0 90 2020 04 04 will return the date in 90 days from 4/4/2020"
echo $#

mSourceDir=/lsfprod/usr/bin/prod/Fidelity

if [ $# -eq "0" ] #|| [ $# -ne 4 ]
then
        echo $USAGE
      exit
elif test $1 -gt 365
then
        echo "parameter too large - max 365"
        exit
elif test $1 -lt -365
then
        echo "parameter too large - max -365"
        exit
else
        diffdays=`echo $1 | sed 's/+//g'`
fi
# Process commandline parameters
echo "Params $# $2 $3 $4"
if [ $# -eq 1 ]
then
        dom=`date '+%d'`
        dow=`date '+%w'`
        doy=`date '+%j'`
        year=`date '+%Y'`       # 4 digit
else
        year=$2 # 4 digit
        mnth=$3
        dom=$4
        echo dow=`$mSourceDir/dow.sh $2 $3 $4`
        echo doy=`$mSourceDir/doy.sh $2 $3 $4`
        dow=`$mSourceDir/dow.sh $2 $3 $4`
        doy=`$mSourceDir/doy.sh $2 $3 $4`
fi
if test $diffdays -lt 0
then
    sign="-"
    diffdays=`echo "$diffdays * -1" | bc`
    if test $diffdays -ge $doy
    then
        year=`echo "$year - 1" | bc`
# Test for leapyear
        if test `cal 2 $year | grep -v  \^\$ | tail -1 | awk '{print $NF}'` -eq "29"
        then
            yeardays=366
        else
            yeardays=365
        fi
        doy=`echo "$yeardays + $doy" | bc`
    fi
    targetday=`echo "$doy $sign $diffdays" | bc`
else
    sign="+"
# Test for leapyear
    if test `cal 2 $year | grep -v  \^\$ | tail -1 | awk '{print $NF}'` -eq "29"
    then
            yeardays=366
    else
            yeardays=365
    fi
    if test `echo "$diffdays + $doy" | bc` -gt $yeardays
    then
        year=`echo "$year + 1" | bc`
 #      echo "$sign doy=$doy"
        targetday=`echo "($diffdays + $doy) - $yeardays" | bc`
    else
        targetday=`echo "($diffdays + $doy)" | bc`
    fi
fi

# calculate current month
month=1
continue="yes"
while test $continue = "yes"
do
    subdays=`cal $month $year | grep -v  \^\$ | tail -1 | awk '{print $NF}'`

    if test $targetday -le $subdays
    then
        continue="no"
        case $month in
                ?) month="0$month";;
        esac
        case $targetday in
                ?) targetday="0$targetday";;
        esac
        echo "$month-$targetday-$year"
        echo "$year $month $targetday"
        echo "$year$month$targetday"
        exit
    else
        #((month=month+1))
        month=`echo "$month + 1" | bc`
        targetday=`echo "$targetday - $subdays" | bc`
        continue="yes"
    fi
done
# Test for leapyear - see if Feb has 29 days
    if test `cal 2 $year | grep -v  \^\$ | tail -1 | awk '{print $NF}'` -eq "29"
        then
            yeardays=366
        else
            yeardays=365
        fi
        doy=`echo "$yeardays + $doy" | bc`
    fi
    targetday=`echo "$doy $sign $diffdays" | bc`
else
    sign="+"
# Test for leapyear - see if Feb has 29 days
    if test `cal 2 $year | grep -v  \^\$ | tail -1 | awk '{print $NF}'` -eq "29"
    then
            yeardays=366
    else
            yeardays=365
    fi
    if test `echo "$diffdays + $doy" | bc` -gt $yeardays
    then
        year=`echo "$year + 1" | bc`
        echo "$sign doy=$doy"
        targetday=`echo "($diffdays + $doy) - $yeardays" | bc`
    else
        targetday=`echo "($diffdays + $doy)" | bc`
    fi
fi

# calculate current month
month=1
continue="yes"
while test $continue = "yes"
do
    subdays=`cal $month $year | grep -v  \^\$ | tail -1 | awk '{print $NF}'`

    if test $targetday -le $subdays
    then
        continue="no"
        case $month in
                ?) month="0$month";;
        esac
        case $targetday in
                ?) targetday="0$targetday";;
        esac
        echo "$month-$targetday-$year"
        echo "$year $month $targetday"
        echo "$year$month$targetday"
        exit
    else
        ((month=month+1))
        targetday=`echo "$targetday - $subdays" | bc`
        continue="yes"
    fi
done