use structopt::StructOpt;
use chrono::prelude::*;

/// timezone converter
///
/// examples:
///
/// - tzconvert CET EST 2pm
///
/// - tzconvert EST CET 1:30pm thu
///
/// - tzconvert Africa/Timbuktu America/Jamaica 18:30 --date 2021-11-03
///
#[derive(StructOpt, Debug)]
#[structopt(author = env!("CARGO_PKG_AUTHORS"))]
struct Opt {
    /// originating time zone
    #[structopt(value_name = "FROM TIMEZONE")]
    from: String,
    /// destination time zone
    #[structopt(value_name = "TO TIMEZONE")]
    to: String,
    /// time to convert (%H:%M or %I[:%M]%p)
    #[structopt(value_name = "TIME")]
    time: String,

    /// optional: specify day of week the time lies, relative to today.
    ///
    /// this will always result in a DATE greater than or equal to
    /// today (in FROM TIMEZONE).
    ///
    /// example: if today is Thursday, Aug. 26, passing DAY OF WEEK "Friday"/"fri"
    /// will result in a DATE of Friday, Aug. 27.
    #[structopt(value_name = "DAY OF WEEK")]
    day: Option<String>,

    /// optional: specify date the time lies. defaults to today.
    ///
    /// when DAY OF WEEK argument is also specified, DAY OF WEEK will be picked relative
    /// to DATE (i.e. the next occuring instance of, on or following DATE).
    #[structopt(long, short, value_name = "DATE")]
    date: Option<NaiveDate>,
}

fn main() {
    let Opt { from, to, time, date, day } = Opt::from_args();
    tzconvert::convert(&from, &to, &time, day, date);
}