extern crate chrono; // 0.4.6
use chrono::TimeZone;
use chrono::Datelike;
use chrono::{DateTime, Utc, Weekday, Duration};


fn string_to_datetime(s: String) -> DateTime<Utc> {
    let now = Utc::now();
    match s.as_ref() {
        "this_week" => {
            let this_week = Utc.isoywd(now.iso_week().year(), now.iso_week().week(), Weekday::Fri).and_hms(8, 0, 0);
            if this_week <= now { Utc.isoywd(now.iso_week().year(), now.iso_week().week() + 1, Weekday::Fri).and_hms(8, 0, 0) } else { this_week }
        },
        "next_week" => {
            let this_week = Utc.isoywd(now.iso_week().year(), now.iso_week().week(), Weekday::Fri).and_hms(8, 0, 0);
            if this_week <= now {
                Utc.isoywd(now.iso_week().year(), now.iso_week().week() + 2, Weekday::Fri).and_hms(8, 0, 0)
            } else {
                Utc.isoywd(now.iso_week().year(), now.iso_week().week() + 1, Weekday::Fri).and_hms(8, 0, 0)
            }
        },
        "quarter" => {
            let now = Utc::now();
            match now {
                x if x < Utc.ymd(2018, 12, 28).and_hms(8, 0, 0) => Utc.ymd(2018, 12, 28).and_hms(8, 0, 0),
                x if x < Utc.ymd(2019, 03, 29).and_hms(8, 0, 0) => Utc.ymd(2019, 03, 29).and_hms(8, 0, 0),
                x if x < Utc.ymd(2019, 06, 28).and_hms(8, 0, 0) => Utc.ymd(2019, 06, 28).and_hms(8, 0, 0),
                _ => panic!("Need to update hardcoded quarterly futures for okex.")
            }
        },
        _ => panic!("Unrecognized futures string.")
    }
}


fn datetime_to_string(d: DateTime<Utc>) -> String {
    let now = Utc::now();
    if d < now + Duration::weeks(1) {
        "this_week".to_owned()
    } else if d < now + Duration::weeks(2) {
        "next_week".to_owned()
    } else {
        "quarter".to_owned()
    }
}

fn main() {
    let d1 = Utc.ymd(2018, 12, 7).and_hms(8, 0, 0);
    let d2 = Utc.ymd(2018, 12, 14).and_hms(8, 0, 0);
    let d3 = Utc.ymd(2018, 12, 28).and_hms(8, 0, 0);
    assert_eq!(datetime_to_string(d1), "this_week");
    assert_eq!(datetime_to_string(d2), "next_week");
    assert_eq!(datetime_to_string(d3), "quarter");
    assert_eq!(string_to_datetime("this_week".to_string()), d1);
    assert_eq!(string_to_datetime("next_week".to_string()), d2);
    assert_eq!(string_to_datetime("quarter".to_string()), d3);
}