# gendt - DATE GENERATOR WITHIN THE GIVEN RANGE
#
# USAGE
#
# gendt <From> <To>
#
# Note: 1. The date must be in DDMMYYYY format
#    2. The <From> date must be smaller than <To> date
#        Ex: dt 30012009 28022009
#    3. The output is in DDMMYY format
#     4. Invalid month days like 300209 (feb has 28 days) & 310408 
#       are corrected automatically by the script
#
# MAINTENANCE HISTORY 
# DATE        AUTHOR AND DETAILS
# 30-01-09    BAS     TR - ORIGINAL 
#
#----------------------------------------------------------------------------79 

frmDate=$1
toDate=$2

# Basic data check
dateChk1() {
    
    len=`echo $1 | wc -c`
    len=`expr $len - 1`

    if [ $len -ne 8 ]; then
        cecho green "Invalid date length (DDMMYYYY)."
        exit
    fi
    
    alpNumFlg=`anflg "$1" "AN"`
    alpFlg=`anflg "$1" "AT"`
    
    finFlg=`expr $alpNumFlg + $alpFlg`
    if [ "$finFlg" != "0" ]; then
        cecho green "$1 is not a number"
        exit
    fi
        
}


dateChk1 "$frmDate"
dateChk1 "$toDate"

# Basic date validation
dateChk2 () {

    case $2 in
        "M")                    
            if [ $1 -le  12 ]; then                        
                if [ $1 -le 0 ]; then                                    
                    cecho green "$1 is an invalid month (1-12)"
                    exit
                fi
            else
                cecho green "$1 is an invalid month (1-12)"
                exit
            fi
            ;;
        "D")
            if [ $1 -le 31 ]; then
                if [ $1 -le 0 ]; then
                    cecho green "Day value $1 must be within (1-31)"
                    exit
                fi
            else
                cecho green "Day value $1 must be within (1-31)"
                exit
                
            fi
            ;;

        "Y")
            if [ $1 -le 0 ]; then
                cecho green "$1 is an invalid year."
                exit
            fi
            ;;
    esac
}

frmDtDay=`echo $frmDate | cut -c1-2`
frmDtMon=`echo $frmDate | cut -c3-4 | tr -d 0`
frmDtYer=`echo $frmDate | cut -c5-8`

toDtDay=`echo $toDate | cut -c1-2`
toDtMon=`echo $toDate | cut -c3-4 | tr -d 0`
toDtYer=`echo $toDate | cut -c5-8`

dateChk2 "$frmDtDay" "D"
dateChk2 "$frmDtMon" "M"
dateChk2 "$frmDtYer" "Y"
dateChk2 "$toDtDay" "D"
dateChk2 "$toDtMon" "M"
dateChk2 "$toDtYer" "Y"

# Make any D & M day,month formats to DD,MM respectively
dateFill() {

    val="$1"    
    dtLen=`echo "$val" | wc -c`
    dtLen=`expr $dtLen - 1`
    if [ $dtLen -lt 2 ]; then
        val="0$1"    
    fi
    return $val
}

yerDiff=`expr $toDtYer - $frmDtYer`
if [ $yerDiff -lt 0 ]; then
    cecho green "Date $frmDate must be less than date $toDate."
    exit
fi

# Display the date in DDMMYY format
datDisp () {

    dateFill $1
    dayTmp=$val
    dateFill $2
    monTmp=$val
    year=`echo $3 | cut -c3-4`    
    echo "$dayTmp$monTmp$year"
}

# Generate dates
for y in $(seq $frmDtYer $toDtYer); do
    for m in $(seq 1 12); do        
        dtGenIni=`cal $m $y | grep -v [A-z] | tr -s ' ' '\n'`
        for d in $dtGenIni; do
                                
            day=$d
            # same year
            if [ $y -eq $toDtYer ]; then
                # same month
                if [ $m -eq $toDtMon ]; then
                    # same day
                    if [ $day -eq $toDtDay ]; then
                        # if all the above, print the same BAS-BAS-BAS day
                        datDisp $day $m $y
                    # different days
                    else                    
                        # print days between From & To Days
                        if [ $day -ge $frmDtDay ]; then
                            if [ $day -le $toDtDay ]; then
                                datDisp $day $m $y                                
                            fi
                        fi                    
                    fi
                # different months
                else
                    # print days between From & To Months                    
                    if [ $m -ge $frmDtMon ]; then                                
                        if [ $m -le $toDtMon ]; then
                            # if curent month is From or To, 
                            # remove dates outside the range                            
                            if [ $m -eq $frmDtMon ]; then
                                if [ $day -ge $frmDtDay ]; then                                    
                                    datDisp $day $m $y
                                fi
                            else
                                    datDisp $day $m $y
                            fi
                        fi
                    fi
                fi    
    
            # different year    
            else
                # print the days between the From & To Years
                if [ $y -ge $frmDtYer ]; then
                    if [ $y -le $toDtYer ]; then
                        # check for same From year
                        if [ $y -eq $frmDtYer ]; then
                            # check for same month
                            if [ $m -eq $frmDtMon ]; then
                                if [ $day -ge $frmDtDay ]; then
                                    datDisp $day $m $y
                                        
                                fi                                
                            fi
                        fi
                        # check for same To Year
                        if [ $y -eq $toDtYer ]; then
                            # check for same month
                            if [ $m -eq $toDtMon ]; then
                                datDisp $day $m $y
                            fi                    
                        else
                            # simply print other dates within the range
                            datDisp $day $m $y
                        fi                    
                    fi    
                fi
            fi                                    
        
        done
    done
done