use std::env;
use std::fs;
use std::io::{self, BufReader, BufRead};
//use regex::Regex;
use chrono::{Duration, DateTime, FixedOffset, NaiveDateTime, TimeZone, Utc};
use chrono_tz::Tz;

fn main() {
    // Regexes
    //let sep = Regex::new(r":").unwrap();

    // read file argument or stdin
    let input = env::args().nth(1);
    let reader: Box<dyn BufRead> = match input {
        None => Box::new(BufReader::new(io::stdin())),
        Some(filename) => Box::new(BufReader::new(fs::File::open(filename).unwrap()))
    };

    // set vacuous values for old and new timestamps, so we can detect the first and second lines
    // of input
    let mut old: DateTime<FixedOffset> = DateTime::from(DateTime::<Utc>::MIN_UTC);
    let mut new: DateTime<FixedOffset> = DateTime::from(DateTime::<Utc>::MIN_UTC);

    for line in reader.lines() {
        let l: String = line.unwrap();
        let (tag, timestamp) = l.split_once(':').unwrap();
        // Timezone mapping
        let ts: Vec<&str> = timestamp.split_whitespace().collect();
        let timezone = ts[4];
        let tz: Tz = match timezone {
            "EDT" => "America/New_York".parse().unwrap(),
            "EST" => "America/New_York".parse().unwrap(),
            "CDT" => "America/Chicago".parse().unwrap(),
            "CST" => "America/Chicago".parse().unwrap(),
            "MDT" => "America/Denver".parse().unwrap(),
            "MST" => "America/Denver".parse().unwrap(),
            "PDT" => "America/Los_Angeles".parse().unwrap(),
            "PST" => "America/Los_Angeles".parse().unwrap(),
            "UTC" => "UTC".parse().unwrap(),
            "GMT" => "GMT".parse().unwrap(),
            other => panic!("Timezone '{}' unknown!", other)
        };

        let ndt = NaiveDateTime::parse_from_str(&timestamp, "%a %b %e %H:%M:%S %Z %Y").unwrap();
        let dt  = tz.from_local_datetime(&ndt).unwrap();
        let to: DateTime<FixedOffset> = DateTime::parse_from_rfc3339(&dt.to_rfc3339()).unwrap();
        if old == DateTime::<Utc>::MIN_UTC { // detect first line
            old = to;
            continue;
        } else if new == DateTime::<Utc>::MIN_UTC { // detect second line
            new = to;
        } else { // subsequent lines
            old = new;
            new = to;
        };

        let dur: Duration = new - old;

        let weeks   = dur.num_weeks();
        let days    = dur.num_days() - weeks * 7;
        let hours   = dur.num_hours() - weeks * 7 * 24 - days * 24;
        let minutes = dur.num_minutes() - weeks * 7 * 24 * 60 - days * 24 * 60 - hours * 60;
        let seconds = dur.num_seconds() - weeks * 7 * 24 * 60 * 60 
                                        - days * 24 * 60 * 60 - hours * 60 * 60 - minutes * 60;

        println!("{}: {} weeks, {} days, {} hours, {} minutes, {} seconds", 
                 tag, weeks, days, hours, minutes, seconds);
    };
}