June 2018 Update

Task/Discordian-date/Rust/discordian-date.rust

@@ -0,0 +1,71 @@
+extern crate chrono;
+
+use chrono::NaiveDate;
+use std::str::FromStr;
+
+fn main() {
+    let date = std::env::args().nth(1).expect("Please provide a YYYY-MM-DD date.");
+    println!("{} is {}", date, NaiveDate::from_str(&date).unwrap().to_poee());
+}
+
+// The necessary constants for the seasons, weekdays, and holydays.
+const APOSTLES: [&str; 5] = ["Mungday", "Mojoday", "Syaday", "Zaraday", "Maladay"];
+const HOLYDAYS: [&str; 5] = ["Chaoflux", "Discoflux", "Confuflux", "Bureflux", "Afflux"];
+const SEASONS: [&str; 5] = ["Chaos", "Discord", "Confusion", "Bureaucracy", "The Aftermath"];
+const WEEKDAYS: [&str; 5] = ["Sweetmorn", "Boomtime", "Pungenday", "Prickle-Prickle", "Setting Orange"];
+
+// The necessary constants for the conversion.
+const APOSTLE_HOLYDAY: usize = 5;
+const CURSE_OF_GREYFACE: i32 = 1166;
+const SEASON_DAYS: usize = 73;
+const SEASON_HOLYDAY: usize = 50;
+const ST_TIBS_DAY: usize = 59;
+const WEEK_DAYS: usize = 5;
+
+// This extends the `Datelike` trait of Rust's Chrono crate with a method that
+// prints any Datelike type as a String.
+impl<T: Datelike> DiscordianDate for T {}
+pub trait DiscordianDate: Datelike {
+    fn to_poee(&self) -> String {
+        let day = self.ordinal0() as usize;
+        let leap = self.year() % 4 == 0 && self.year() % 100 != 0 || self.year() % 400 == 0;
+        let year = self.year() + CURSE_OF_GREYFACE;
+
+        if leap && day == ST_TIBS_DAY { return format!("St. Tib's Day, in the YOLD {}", year); }
+
+        let day_offset = if leap && day > ST_TIBS_DAY { day - 1 } else { day };
+
+        let day_of_season = day_offset % SEASON_DAYS + 1;
+
+        let season = SEASONS[day_offset / SEASON_DAYS];
+        let weekday = WEEKDAYS[day_offset % WEEK_DAYS];
+
+        let holiday = if day_of_season == APOSTLE_HOLYDAY {
+            format!("\nCelebrate {}", APOSTLES[day_offset / SEASON_DAYS])
+        } else if day_of_season == SEASON_HOLYDAY {
+            format!("\nCelebrate {}", HOLYDAYS[day_offset / SEASON_DAYS])
+        } else {
+            String::with_capacity(0)
+        };
+
+        format!("{}, the {} day of {} in the YOLD {}{}",
+            weekday, ordinalize(day_of_season), season, year, holiday)
+    }
+}
+
+/// A helper function to ordinalize a numeral.
+fn ordinalize(num: usize) -> String {
+    let s = format!("{}", num);
+
+    let suffix = if s.ends_with('1') && !s.ends_with("11") {
+        "st"
+    } else if s.ends_with('2') && !s.ends_with("12") {
+        "nd"
+    } else if s.ends_with('3') && !s.ends_with("13") {
+        "rd"
+    } else {
+        "th"
+    };
+
+    format!("{}{}", s, suffix)
+}