#!/bin/ksh
typeset -i mYear mMonth mDay
typeset -i mYear2 mMonth2
typeset -i mDaysWeek
set -A mNameDays N/A Sunday Monday Tuesday Wednesday Thursday Friday Saturday
clear
echo ""
echo "Based on a date (YMD) and a day of the week,"
echo "this script will display the equivalent date (YMD)"
echo "for the entered day of the week."
echo "Examples:"
echo "1) Date: 2010-12-31 and Saturday"
echo "   The output will be: 2011-01-01"
echo "2) Date: 2011-04-01 and Tuesday"
echo "   The output will be: 2011-03-29"
echo ""
echo "WARNING: No data validation will be performed."
echo "         Garbage in, garbage out."
echo ""
echo "Enter Year in the format (YYYY):"
read mYear
echo "Enter Month in the format (MM):"
read mMonth
echo "Enter Day in the format (DD):"
read mDayStr
mDay=${mDayStr}

# Inserts '0' to the left of single digit days:
cal ${mMonth} ${mYear} | sed -e 's/ \([1-9]\) /0\1 /g' -e 's/ \([1-9]\)$/0\1/' > /tmp/mFile_Calendar

# Remove lines without day numbers from calendar:
egrep -v '[a-z]' /tmp/mFile_Calendar > /tmp/mFile_Cal_Numbers

# Create a file with week current of day:
egrep "${mDayStr}" /tmp/mFile_Cal_Numbers > /tmp/mFile_Week

# Count the number of days in the week for calendar line:
mDaysWeek=`wc -w /tmp/mFile_Week | sed 's/ .*//'`
if [[ ${mDaysWeek} -eq 7 ]]; then
  mv /tmp/mFile_Week /tmp/mFile_Full_Week
  mMonth2=${mMonth}
  mYear2=${mYear}
else
  # If day is in first week of month:
  if [[ ${mDay} -lt 7 ]]; then
    # Get the last week of prior month:
    if [[ ${mMonth} -eq 1 ]]; then
      mMonth2=12
      mYear2=${mYear}-1
    else
      mMonth2=${mMonth}-1
      mYear2=${mYear}
    fi
    cal ${mMonth2} ${mYear2} | sed '$d' | tail -1 > /tmp/mFile_Week2
    cat /tmp/mFile_Week2 /tmp/mFile_Week | xargs > /tmp/mFile_Full_Week
  else
    # If day is in last week of month:
    # Get the first week of next month:
    if [[ ${mMonth} -eq 12 ]]; then
      mMonth2=1
      mYear2=${mYear}+1
    else
      mMonth2=${mMonth}+1
      mYear2=${mYear}
    fi
    # Inserts '0' to the left of single digit days:
    cal ${mMonth2} ${mYear2} | sed -e 's/ \([1-9]\) /0\1 /g' -e 's/ \([1-9]\)$/0\1/' > /tmp/mFile_Calendar2
    # Remove lines without day numbers from calendar:
    egrep -v '[a-z]' /tmp/mFile_Calendar2 > /tmp/mFile_Cal_Numbers2
    # Create a file with week current of day:
    # Create a file with week current of day:
    head -1 /tmp/mFile_Cal_Numbers2 > /tmp/mFile_Week2
    cat /tmp/mFile_Week /tmp/mFile_Week2 | xargs > /tmp/mFile_Full_Week
  fi
fi
clear
echo "==============================================="
echo "Following is the input date:"
echo "Year = ${mYear} Month = ${mMonth} Day = ${mDay}"
echo "Full week for the input date:"
echo "Su Mo Tu We Th Fr Sa"
cat /tmp/mFile_Full_Week
echo "Now enter the day of the week in the format (XX):"
echo "01-Sunday"
echo "02-Monday"
echo "03-Tuesday"
echo "04-Wednesday"
echo "05-Thursday"
echo "06-Friday"
echo "07-Saturday"
read mWeekDay
echo ${mNameDays[${mWeekDay}]}
mDay2=`cut -d' ' -f${mWeekDay} /tmp/mFile_Full_Week`
echo "For the above week, ${mNameDays[${mWeekDay}]} is:"
echo "Year = ${mYear2} Month = ${mMonth2} Day = ${mDay2}"
rm -f /tmp/mFile*
#---------------------- End of Script ---------------------#