use chrono::offset::TimeZone;
use chrono::{Duration, Utc};
use segmap::SegmentMap;

let people = ["Alice", "Bob", "Carol"];
let mut roster = SegmentMap::new();

// Set up initial roster.
let start_of_roster = Utc.ymd(2019, 1, 7);
let mut week_start = start_of_roster;
for _ in 0..3 {
    for person in people {
        let next_week = week_start + Duration::weeks(1);
        roster.insert(week_start..next_week, person);
        week_start = next_week;
    }
}

// Bob is covering Alice's second shift (the fourth shift overall).
let fourth_shift_start = start_of_roster + Duration::weeks(3);
let fourth_shift_end = fourth_shift_start + Duration::weeks(1);
roster.insert(fourth_shift_start..fourth_shift_end, "Bob");

// Print out the roster, and observe that
// the fourth and fifth shifts have been coalesced
// into one range.
for (range, &person) in roster.iter() {
    let start = *range.start_value().unwrap();
    let duration = *range.end_value().unwrap() - start;
    println!("{} ({}): {}", start, duration, person);
}

// Output:
// 2019-01-07UTC (P7D): Alice
// 2019-01-14UTC (P7D): Bob
// 2019-01-21UTC (P7D): Carol
// 2019-01-28UTC (P14D): Bob
// 2019-02-11UTC (P7D): Carol
// 2019-02-18UTC (P7D): Alice
// 2019-02-25UTC (P7D): Bob
// 2019-03-04UTC (P7D): Carol