#!/usr/bin/env bash
# Desc: Baltakatei's verbose date command
# Usage: bkdatev [args]
# Example: bkdatev --date="2001-09-11T09:02:59-04"
# Version: 0.1.0
# Ref/Attrib: [1] "ISO 8601". Wikipedia. https://en.wikipedia.org/wiki/ISO_8601
#             [2] "Changing the Locale in Wine" https://stackoverflow.com/a/16428951
#             [3] "Shanghai vs Beijing" https://bugs.launchpad.net/ubuntu/+source/libgweather/+bug/228554
# Notes:  * Check `ls -R /usr/share/zoneinfo` for time zone names.
#         * Check `cat /usr/share/i18n/SUPPORTED` for supported locales.
#         * For list of valid locales, see: https://manpages.ubuntu.com/manpages/bionic/man3/DateTime::Locale::Catalog.3pm.html
#         * Locations chosen for population, personal signifiance, and spatial coverage.
#         # For International Atomic Time (TAI), use offsets from UTC provided in `/usr/share/zoneinfo/leap-seconds.list`.

line_sep() {
    # Input: var: n_ln
    local skip_every=4;
    ((n_ln++));
    if ! ((n_ln % "$skip_every")); then
        printf "\n";
    fi;
    return 0;
}; # periodically print separating blank line
print_dateline() {
    # Input: var: $id
    #        var: $fs_1
    #        var: $fs_2
    #        var: $fs_3
    #        args: $@
    # Output: stdout
    # Depends: printf, date
    # Ref/Attrib: * Truncate string in printf https://stackoverflow.com/a/46812677
    local s_1 s_2 s_3 s_4;

    s_1="$id";
    s_2="$(date "$@" "$fs_1")";
    s_3="$(date "$@" "$fs_2")";
    s_4="$(date "$@" "$fs_3")";

    printf "%-10.10s %-25.25s (%-20.20s) (%s)" "$s_1" "$s_2" "$s_3" "$s_4";
    printf "\n";

    unset fs_1 fs_2 fs_3 fs_4;
    }; # print line of dates
main() {
    n_ln=0; # for line_sep()
    
    # format strings
    fs_iso8601="+%Y-%m-%dT%H:%M:%S%:::z"; # typical ISO-8601
    fs_iso8601_etc="+%G-W%V-%u, %Y-%j"; # alternate ISO-8601 dates
    fs_locale="+%Z; %A; %c"; # locale-specific date strings

    # vars for print_dateline()
    fs_1="$fs_iso8601";
    fs_2="$fs_iso8601_etc";
    fs_3="$fs_locale";

    # UTC (pop. (2021): 7,837,000,000)
    (
        export TZ=UTC;
        id="UTC";
        fs_3="+%s seconds since 1970-01-01T00:00+00";
        print_dateline "$@";
    ); line_sep;

    # Hawaii
    (
        export TZ=US/Hawaii;
        export LANG="haw-US.UTF8";
        id="HAWAII";
        print_dateline "$@";
    ); line_sep;

    # Los Angeles, USA
    (
        export TZ=America/Los_Angeles;
        export LANG="en_US.UTF-8";
        id="LOS ANGELES";
        print_dateline "$@";
    ); line_sep;

    # Denver, USA (pop. (2021): 711,463)
    (
        export TZ=America/Denver;
        export LANG="en_US.UTF-8";
        id="DENVER";
        print_dateline "$@";
    ); line_sep;

    # Chicago, USA (pop. (2021): 711,463)
    (
        export TZ=America/Chicago;
        export LANG="en_US.UTF-8";
        id="CHICAGO";
        print_dateline "$@";
    ); line_sep;

    # Mexico City, Mexico (pop. (2018): 21,804,515)
    (
        export TZ=America/Mexico_City;
        export LANG="es_MX.UTF8";
        id="MEXICO CITY";
        print_dateline "$@";
    ); line_sep;

    # Panama City, Panama
    (
        export TZ=America/Panama;
        export LANG="es_PA.UTF8";
        id="PANAMA CITY";
        print_dateline "$@";
    ); line_sep;

    # New York, USA (pop. (2018): 20,140,470)
    (
        export TZ=America/New_York;
        export LANG="en_US.UTF-8";
        id="NEW YORK";
        print_dateline "$@";
    ); line_sep;

    # São Paulo, Brazil
    (
        export TZ=America/Sao_Paulo;
        export LANG="pt_BR.UTF8";
        id="SAO PAULO";
        print_dateline "$@";
    ); line_sep;

    # Buenos Aires
    (
        export TZ=America/Argentina/Buenos_Aires;
        export LANG="es_AR.UTF8";
        id="BUENOS AIRES";
        print_dateline "$@";
    ); line_sep;

    # London, England
    (
        export TZ=Europe/London;
        export LANG="en_GB.UTF-8";
        id="LONDON";
        print_dateline "$@";
    ); line_sep;

    # Kinshasa, Africa
    (
        export TZ=Africa/Kinshasa;
        export LANG="ln_CD.UTF8";
        id="KINSHASA";
        print_dateline "$@";
    ); line_sep;

    # Lagos, Africa
    (
        export TZ=Africa/Lagos;
        export LANG="en_NG.UTF8";
        id="LAGOS";
        print_dateline "$@";
    ); line_sep;

    # Paris, France
    (
        export TZ=Europe/Paris;
        export LANG="fr_FR.UTF8";
        id="PARIS";
        print_dateline "$@";
    ); line_sep;

    # Stockholm, Sweden
    (
        export TZ=Europe/Stockholm;
        export LANG="sv_SE.UTF8";
        id="STOCKHOLM";
        print_dateline "$@";
    ); line_sep;

    # Cairo, Egypt
    (
        export TZ=Africa/Cairo;
        export LANG="ar_EG.UTF8";
        id="CAIRO";
        print_dateline "$@";
    ); line_sep;

    # Athens (pop. (2020): 3,526,887)
    (
        export TZ=Europe/Athens;
        export LANG="el_GR.UTF8";
        id="ATHENS";
        print_dateline "$@";
    ); line_sep;

    # Istanbul (pop. (2020): 13,719,061)
    (
        export TZ=Asia/Istanbul;
        export LANG="tr_TR.UTF8";
        id="ISTANBUL";
        print_dateline "$@";
    ); line_sep;

    # Tehran, Iran
    (
        export TZ=Asia/Tehran;
        export LANG="fa_IR.UTF8";
        id="TEHRAN";
        print_dateline "$@";
    ); line_sep;

    # Moscow, Russia
    (
        export TZ=Europe/Moscow;
        export LANG="ru_RU.UTF-8";
        id="MOSCOW";
        print_dateline "$@";
    ); line_sep;

    # Kyiv, Ukraine (pop. (2021): 2,962,180)
    (
        export TZ=Europe/Kyiv;
        export LANG="uk_UA.UTF-8";
        id="KYIV";
        print_dateline "$@";
    ); line_sep;

    # Delhi, India (pop. (2018): 29,000,000)
    (
        export TZ=Asia/Kolkata;
        export LANG="hi_IN.UTF-8";
        id="DELHI";
        print_dateline "$@";
    ); line_sep;

    # Jakarta, Indonesia (pop. (2018): 33,430,285)
    (
        export TZ=Asia/Jakarta;
        export LANG="id_ID.UTF8";
        id="JAKARTA";
        print_dateline "$@";
    ); line_sep;

    # Singapore, Singapore (pop (2018): 5,792,000)
    (
        export TZ=Asia/Singapore;
        export LANG="en_SG.UTF-8";
        id="SINGAPORE";
        print_dateline "$@";
    ); line_sep;

    # Beijing, China (pop. (2018): 19,618,000)
    (
        export TZ=Asia/Shanghai; # [3]
        export LANG="zh_CN.UTF-8";
        id="BEIJING";
        print_dateline "$@";
    ); line_sep;

    # Tokyo, Japan (pop. (2018): 37,274,000)
    (
        export TZ=Asia/Tokyo;
        export LANG="ja_JP.UTF8";
        id="TOKYO";
        print_dateline "$@";
    ); line_sep;

    # Seoul, South Korea (pop. (2018): 25,514,000)
    (
        export TZ=Asia/Seoul;
        export LANG="ko_KR.UTF8";
        id="SEOUL";
        print_dateline "$@";
    ); line_sep;

    # Sydney, Australia
    (
        export TZ=Australia/Sydney;
        export LANG="en_AU.UTF8";
        id="SYDNEY";
        print_dateline "$@";
    ); line_sep;

    # Guam
    (
        export TZ=Pacific/Guam;
        export LANG="en_GU.UTF8";
        id="GUAM";
        print_dateline "$@";
    ); line_sep;

    # Auckland, New Zealand
    (
        export TZ=Pacific/Auckland;
        export LANG="en_NZ.UTF8";
        id="AUCKLAND";
        print_dateline "$@";
    ); line_sep;
    
    return 0;
}; # main program

main "$@";