#![allow(unused)]
use std::str::FromStr;
use chrono::{DateTime, Utc, NaiveDateTime, TimeZone};

const ONE_SECOND: u64 = 1_000_000_000_u64;

fn nanos(utc: DateTime<Utc>) -> u64 {
    (utc.timestamp() as u64) * 1_000_000_000_u64 + (utc.timestamp_subsec_nanos() as u64)
}

fn get_time() -> (i64, i32) {
    let mut tv = libc::timespec { tv_sec: 0, tv_nsec: 0 };
    unsafe { libc::clock_gettime(libc::CLOCK_REALTIME, &mut tv); }
    (tv.tv_sec as i64, tv.tv_nsec as i32)
}

fn timespec_to_utc(sec: i64, nsec: i32) -> DateTime<Utc> {
    let naive = NaiveDateTime::from_timestamp(sec, nsec as u32);
    DateTime::from_utc(naive, Utc)
}

fn timespec_to_nanos(sec: i64, nsec: i32) -> u64 {
    (sec as u64) * ONE_SECOND + (nsec as u64)
}

fn nanos_to_timespec(nanos: u64) -> (i64, i32) {
    ((nanos / ONE_SECOND) as i64, (nanos % ONE_SECOND) as i32)
}

fn main() {
    let args: clap::ArgMatches = clap::App::new("utcnow")
        .author("Jonathan Strong <jonathan.strong@gmail.com>")
        .version(clap::crate_version!())
        .about("\ncurrent time in utc with non-cryptic interface.\n\n\
                for your own safety and well-being, local time functionality is not provided.\n\n\
                default output format is rfc3339 with trailing 'Z', e.g. '1999-12-31T23:59:59.999999999Z'")
        .help_message("help")
        .version_message("version")
        .arg(clap::Arg::with_name("unix")
            .help("display elapsed nanoseconds since 1970-01-01T00:00:00Z")
            .long("unix")
            .short("u")
            .required(false)
            .takes_value(false))
        .arg(clap::Arg::with_name("rfc2822")
            .help("display in rfc2822 format")
            .long("rfc2822")
            .short("r")
            .required(false)
            .takes_value(false))
        .arg(clap::Arg::with_name("seconds")
            .help("display unix timestamp in seconds, instead of default nanoseconds")
            .long("seconds")
            .short("s")
            .conflicts_with_all(&["rfc2822", "timespec", "millis"])
            .required(false)
            .takes_value(false))
        .arg(clap::Arg::with_name("millis")
            .help("display unix timestamp in milliseconds, instead of default nanoseconds")
            .long("millis")
            .short("m")
            .conflicts_with_all(&["rfc2822", "timespec", "seconds"])
            .required(false)
            .takes_value(false))
        .arg(clap::Arg::with_name("timespec")
            .help("display as <sec>,<nsec>")
            .long("timespec")
            .short("t")
            .required(false)
            .takes_value(false))
        .arg(clap::Arg::with_name("null")
            .short("0")
            .long("null")
            .help("terminate displayed time with null character instead of newline")
            .takes_value(false)
            .required(false))
        .arg(clap::Arg::with_name("unix-to-rfc3339")
            .long("unix-to-rfc3339")
            .short("R")
            .alias("unix-to-utc")
            .help("convert integer unix timestamp (nanoseconds precision) to datetime \
                   in rfc3339 format. combine with --seconds or --millis to parse a
                   seconds timestamp with alternate precison")
            .takes_value(true)
            .required(false)
            .conflicts_with_all(&["unix"]))
        .arg(clap::Arg::with_name("rfc3339-to-unix")
            .long("rfc3339-to-unix")
            .short("U")
            .alias("utc-to-unix")
            .help("parse rfc3339 timestamp and display it as a unix timestamp")
            .takes_value(true)
            .required(false)
            .conflicts_with_all(&["unix", "unix-to-rfc3339", "rfc2822", "timespec"]))
        .get_matches();

    
    let (sec, nsec): (i64, i32) =

        if let Some(ts_str) = args.value_of("unix-to-rfc3339") {                        // either parse --unix-to-rfc3339 input
            match u64::from_str(ts_str) {

                // check alternate precisions --seconds or --millis

                Ok(seconds) if args.is_present("seconds") => nanos_to_timespec(seconds * ONE_SECOND),
                
                Ok(millis) if args.is_present("millis") => nanos_to_timespec(millis * 1_000_000),

                // otherwise go with default nanos

                Ok(nanos) => nanos_to_timespec(nanos),

                Err(e) => {
                    eprintln!("failed to parse timestamp (expected integer): {}", e);
                    std::process::exit(1);
                }
            }

        } else if let Some(rfc_str) = args.value_of("rfc3339-to-unix") {                // or --rfc3339-to-unix
            //match DateTime::<Utc>::parse_from_rfc3339(rfc_str) {
            match rfc_str.parse::<DateTime<Utc>>() {
                Ok(utc) => nanos_to_timespec(nanos(utc)),

                Err(e) => {
                    eprintln!("failed to parse timestamp (expected integer): {}", e);
                    std::process::exit(1);
                }
            }

        } else {                                                                        // or else get current time
            get_time()
        };


    let endline = if args.is_present("null") { "\u{0}" } else { "\n" };                 // pick endline - \n unless -0


    if args.is_present("timespec") {                                                    // display timespec
        print!("{},{}{}", sec, nsec, endline);


    } else if args.is_present("unix") || args.is_present("rfc3339-to-unix") {           // display unix

        if args.is_present("seconds") {                                                 // unix seconds
            print!("{}{}", sec, endline);
        } else if args.is_present("millis") {                                           // unix millis
            print!("{}{}", timespec_to_nanos(sec, nsec) / 1_000_000, endline);
        } else {                                                                        // unix nanos
            print!("{}{}", timespec_to_nanos(sec, nsec), endline);
        }


    } else if args.is_present("rfc2822") {                                              // display rfc2822
        print!("{}{}", timespec_to_utc(sec, nsec).to_rfc2822(), endline);


    } else {                                                                            // display rfc3339
        // Debug view is iso format / rfc3339 that we want
        // Display has spaces - no go
        // to_rfc3339 uses +00:00 instead of Z, which I don't like
        print!("{:?}{}", timespec_to_utc(sec, nsec), endline);
    }
}