#!/bin/bash

# Desc: Template to display date and time.

yell() { echo "$0: $*" >&2; }      #o Yell, Die, Try Three-Fingered Claw technique
die() { yell "$*"; exit 111; }     #o Ref/Attrib: https://stackoverflow.com/a/25515370
try() { "$@" || die "cannot $*"; } #o
dateTimeShort(){
    # Desc: Timestamp without separators (YYYYmmddTHHMMSS+zzzz)
    # Usage: dateTimeShort ([str date])
    # Version 1.1.0
    # Input: arg1: 'date'-parsable timestamp string (optional)
    # Output: stdout: timestamp (ISO-8601, no separators)
    # Depends: yell
    local TIME_CURRENT TIME_CURRENT_SHORT

    argTime="$1";
    # Get Current Time
    TIME_CURRENT="$(date --iso-8601=seconds)" ; # Produce `date`-parsable current timestamp with resolution of 1 second.
    # Decide to parse current or supplied date
    ## Check if time argument empty
    if [[ -z "$argTime" ]]; then
	## T: Time argument empty, use current time
	TIME_INPUT="$TIME_CURRENT";
    else
	## F: Time argument exists, validate time
	if date --date="$argTime" 1>/dev/null 2>&1; then
	    ### T: Time argument is valid; use it
	    TIME_INPUT="$argTime";
	else
	    ### F: Time argument not valid; exit
	    yell "ERROR:Invalid time argument supplied. Exiting."; exit 1;
	fi
    fi
    # Construct and deliver separator-les date string
    TIME_CURRENT_SHORT="$(date -d "$TIME_INPUT" +%Y%m%dT%H%M%S%z)";
    echo "$TIME_CURRENT_SHORT";
} # Get YYYYmmddTHHMMSS±zzzz

#==BEGIN sample code==
echo "The current day and time is :$(dateTimeShort)";
echo "Contact lost with STS-107 on:$(dateTimeShort "2003-02-01T08:59:15-05:00")";
echo "Bitcoin started on          :$(dateTimeShort "@1231006505")";

#==END sample code==

# Author: Steven Baltakatei Sandoval
# License: GPLv3+