#!/bin/sh
# 
# zoneinfo - show the current time in the specified timezone or 
#   geographic zone. Without any argument, show UTC/GMT. Use
#   the word "list" to see a list of known geographic regions
#   Note that it's possible to match a zone directory (a region)
#   but that only timezone files are valid specifications.
#   
#   Timezone database ref: http://www.twinsun.com/tz/tz-link.htm

zonedir="/usr/share/zoneinfo"
if [ ! -d $zonedir ] ; then
	echo "No timezone database at $zonedir." >&2 ; exit 1
fi

if [ -d "$zonedir/posix" ] ; then
	zonedir=$zonedir/posix
fi

if [ $# -eq 0 ] ; then
	timezone="UTC"
	mixedzone="UTC"
	elif [ "$1" = "list" ] ; then
		( echo "All known timezones and regions defined on this system:"
		cd $zonedir
		find * -type f -print | xargs -n 2 | awk '{ printf "  %-38s %-38s\n", $1, $2 }' ) | $PAGER
		exit 0
	else
		region="$(dirname $1)"
		zone="$(basename $1)"

		# Is it a direct match?  If so,  we're good to go. Otherwise we need 
		# to dig around a bit to find things. Start by just counting matches
		matchcnt="$(find $zonedir -name $zone -type f -print | wc -l | sed 's/[^[:digit:]]//g' )"
		if [ "$matchcnt" -gt 0 ] ; then       # at least one file matches
			if [ $matchcnt -gt 1 ] ; then       # more than one file match
				echo "\"$zone\" matches more than one possible time zone record." >&2
				echo "Please use 'list' to see all known regions and timezones" >&2
				exit 1
			fi
			match="$(find $zonedir -name $zone -type f -print)"
			mixedzone="$zone" 
		else
			# Normalize to first upper, rest of word lowercase for region + zone
			mixedregion="$(echo ${region%${region#?}} | tr '[[:lower:]]' '[[:upper:]]') \
			$(echo ${region#?} | tr '[[:upper:]]' '[[:lower:]]')"
			mixedzone="$(echo ${zone%${zone#?}} | tr '[[:lower:]]' '[[:upper:]]') \
			$(echo ${zone#?} | tr '[[:upper:]]' '[[:lower:]]')"
			if [ "$mixedregion" != "." ] ; then
				# only look for specified zone in specified region
				# to let users specify unique matches when there's more than one
				# possibility (e.g., "Atlantic")
				match="$(find $zonedir/$mixedregion -type f -name $mixedzone -print)"
			else
				match="$(find $zonedir -name $mixedzone -type f -print)"
			fi
			if [ -z "$match"  ] ; then  # no file matches specified pattern
				if [ ! -z $(find $zonedir -name $mixedzone -type d -print) ] ; then
					echo \
					"The region \"$1\" has more than one timezone. Please use 'list'" >&2
				else #  just not a match at all
					echo "Can't find an exact match for \"$1\". Please use 'list'" >&2
				fi
				echo "to see all known regions and timezones." >&2
				exit 1
			fi
		fi
		timezone="$match"
	fi
	nicetz=$(echo $timezone | sed "s|$zonedir/||g")     # pretty up the output
	echo It\'s $(TZ=$timezone date '+%A, %B %e, %Y, at %l:%M %p') in $nicetz
	exit 0