#!/bin/bash
## When datestamping the Version of a computer-program, I want days to change at 8am rather than midnight;  Eugene Reimer  2008-02-11
##	(changing days at 4am would be more appropriate for most people, but not for someone of my habits...)
## This ought to be dead-trivial and would be but for that silliness about a leading-zero implying Octal, and then printf not supporting 10#NN, grumble grumble...
##
## USAGE:  same as for the date command  (only -d -r +FMT options).

##--original arg-handling:
DOP="now";                 if [[ $1 == -d ]];then DOP=$2; shift;shift; fi	##support -d option, as in date command
ROP=;                      if [[ $1 == -r ]];then ROP=$2; shift;shift; fi	##support -r option, as in date command
FMT="+%Y-%m-%d %H:%M:%S";  if [[ $1 == +* ]];then FMT=$1; shift; fi		##support FMT-string as in date command
if [ $ROP ];then  DATEANDTIME=$(date -r "$ROP" "+%Y-%m-%d %H:%M:%S");
else              DATEANDTIME=$(date -d "$DOP" "+%Y-%m-%d %H:%M:%S");
fi

##--2008-07-19:  ==UNFINISHED==  improved arg-handling:
##while [ $# -gt 0 ]; do  						##parse the cmdline-args
##  [[ $1 == --[hv]* ]] && HELP=1  					##set HELP=1 for --help or --version
##  case "$1" in
##  +*)		FMT=$1; shift			;;			##save FMT-arg separately
##  -d)		ARG="$ARG -d '$2'"; shift;shift	;;			##save -d arg in ARG-string      (strophs not behaving as expected here either??))
##  *)		ARG="$ARG $1"; shift		;;			##save other args in ARG-string
####*)		ARG="$ARG '$1'"; shift		;;			##save other args in ARG-string  (strophs not behaving as expected)
##  esac
##done
##echo "DEBUG ARG:$ARG FMT:$FMT HELP:$HELP"; read; 			##DEBUG
##if [ $HELP ];then date $ARG; exit 0; fi  				##for --help or --version:  handle then exit
##DATEANDTIME=$(date $ARG "+%Y-%m-%d %H:%M:%S")

##--rest is independent of where the date came from (this may become datefixupERW):
YEAR=$(date -d "$DATEANDTIME" +%Y)
MNTH=$(date -d "$DATEANDTIME" +%m)
DAYM=$(date -d "$DATEANDTIME" +%d)
HOUR=$(date -d "$DATEANDTIME" +%H)
MINU=$(date -d "$DATEANDTIME" +%M)
SECO=$(date -d "$DATEANDTIME" +%S)
daym=${DAYM#0}; hour=${HOUR#0};						##remove leading-zero, to avoid octal...
if ((hour<8));then ((daym=daym-1)); HOUR=23; MINU=59; SECO=59; fi;	##do arithmetic with numeric vars  (clock stands still midnight-to-8am)
DAYM=$(printf "%02d" $daym)						##convert back to string, adding leading-zero if needed
date -d "$YEAR$MNTH$DAYM $HOUR:$MINU:$SECO"  "$FMT"			##use date to reformat result, to support FMT param, and fixup day-zero...
	##--tested with  dateERW -d "20080101 07:22"  to verify that <date> handles day-of-month going to zero.


exit
CONSIDER:  making FMT-default same as date-cmd;  the only previous use is in  INSTALL-new-version-of-nopercart--??--

2008-07-19:  copyCF needs support for -r/--reference,  so I TRIED to rewrite the arg-handling to support any date-arg;
	GRUMBLE:  the -d operand apparently must have a space between date & time when both being specified
		==my reading suggests that "T" ought to work too, but it results in time-less-13-hours -- may be fixable--??--
		==2010-03: (see notes in EXAMPLES-DATE);  date-cmd supports single-letter timezone-names, where "F" is -0600 (winter-time), "E" is -0500 (summer-time);
		==	but not "J" which ought to be roughly what "T" is in ISO-8601-dates;  Conclusion: it can produce ISO-8601-dates, but not accept them:-(
	ARG-HANDLING:
		==using  <ARG="-d '20080101 07:22'"; args $ARG>  demonstrates problem with quotes/strophs inside strings not behaving as I thought they did--!!--
		==for more info:  http://www.mpi-inf.mpg.de/~uwe/lehre/unixffb/quoting-guide.html
		==!!==failed to find satisfactory solution;  would involve <eval> and way too much work+mess,  unless I can solve the "T" riddle==!!==
		==2010-03: ANOTHER SOLUTION: make ARG an array;  later use set-cmd followed by:  date "$@"==??==
	SOLUTION:  went back to old method, adding ROP for -r support  ==surely there is a better way??

2008-07-20:  copyCF needs to use the EXIF-date (to handle having rotated on the laptop) -- so made separate script dateEXIF-ERW to do that;
	==datefixupERW to do the shared portion -- receives  YYYY-MM-YY HH:MM:SS +FMT