emlop 0.6.1

use crate::{table::Disp, wtb, DurationStyle, Styles};
use anyhow::{bail, Error};
use log::{debug, warn};
use regex::Regex;
use std::{convert::TryFrom,
          io::Write as _,
          str::FromStr,
          time::{SystemTime, UNIX_EPOCH}};
use time::{macros::format_description, parsing::Parsed, Date, Duration, Month, OffsetDateTime,
           UtcOffset, Weekday};

/// Get the UtcOffset to parse/display datetimes with.
/// Needs to be called before starting extra threads.
pub fn get_offset(utc: bool) -> UtcOffset {
    if utc {
        UtcOffset::UTC
    } else {
        UtcOffset::current_local_offset().unwrap_or_else(|e| {
                                             warn!("Falling back to UTC: {}", e);
                                             UtcOffset::UTC
                                         })
    }
}

// It'd be nice to support user-defined formats, but lifetimes make this a bit akward.
// See <https://github.com/time-rs/time/issues/429>
pub struct DateStyle(&'static [time::format_description::FormatItem<'static>]);
impl FromStr for DateStyle {
    type Err = &'static str;
    fn from_str(s: &str) -> Result<Self, Self::Err> {
        let fmt = match s {
            "ymd" | "d" => format_description!("[year]-[month]-[day]"),
            "ymdhms" | "dt" => format_description!("[year]-[month]-[day] [hour]:[minute]:[second]"),
            "ymdhmso" | "dto" => format_description!("[year]-[month]-[day] [hour]:[minute]:[second] [offset_hour sign:mandatory]:[offset_minute]"),
            "rfc3339" | "3339" => format_description!("[year]-[month]-[day]T[hour]:[minute]:[second][offset_hour sign:mandatory]:[offset_minute]"),
            "rfc2822" | "2822" => format_description!("[weekday repr:short], [day] [month repr:short] [year] [hour]:[minute]:[second] [offset_hour sign:mandatory]:[offset_minute]"),
            "compact" => format_description!("[year][month][day][hour][minute][second]"),
            "unix" => &[],
            _ => return Err("Valid values are ymd, d, ymdhms, dt, ymdhmso, dto, rfc3339, 3339, rfc2822, 2822, compact, unix"),
        };
        Ok(Self(fmt))
    }
}

/// Format standardized utc dates
pub fn fmt_utctime(ts: i64) -> String {
    let fmt = format_description!("[year]-[month]-[day]T[hour]:[minute]:[second]Z");
    OffsetDateTime::from_unix_timestamp(ts).unwrap().format(&fmt).unwrap()
}

pub struct FmtDate(pub i64);
/// Format dates according to user preferencess
impl Disp for FmtDate {
    fn out(&self, buf: &mut Vec<u8>, st: &Styles) -> usize {
        let start = buf.len();
        if st.date_fmt.0.is_empty() {
            write!(buf, "{}", self.0).expect("write to buf");
        } else {
            OffsetDateTime::from_unix_timestamp(self.0).expect("unix from i64")
                                                       .to_offset(st.date_offset)
                                                       .format_into(buf, &st.date_fmt.0)
                                                       .expect("write to buf");
        }
        buf.len() - start
    }
}

pub fn epoch_now() -> i64 {
    SystemTime::now().duration_since(UNIX_EPOCH).unwrap().as_secs() as i64
}

/// Parse datetime in various formats, returning unix timestamp
pub fn parse_date(s: &str, offset: UtcOffset) -> Result<i64, String> {
    let s = s.trim();
    i64::from_str(s).or_else(|e| {
                        debug!("{s}: bad timestamp: {e}");
                        parse_date_yyyymmdd(s, offset)
                    })
                    .or_else(|e| {
                        debug!("{s}: bad absolute date: {e}");
                        parse_date_ago(s)
                    })
                    .map_err(|e| {
                        debug!("{s}: bad relative date: {e}");
                        format!("Couldn't parse {s:#?}, check examples in --help")
                    })
}

/// Parse a number of day/years/hours/etc in the past, relative to current time
fn parse_date_ago(s: &str) -> Result<i64, Error> {
    if !s.chars().all(|c| c.is_alphanumeric() || c == ' ' || c == ',') {
        bail!("Illegal char");
    }
    let mut now = OffsetDateTime::now_utc();
    let re = Regex::new("([0-9]+|[a-z]+)").expect("Bad date span regex");
    let mut tokens = re.find_iter(s);
    let mut at_least_one = false;

    // The regex gives us a list of positive integers and strings. We expect to always have a
    // number, followed by a known string.
    while let Some(t) = tokens.next() {
        at_least_one = true;
        let num: i32 = t.as_str().parse()?;
        match tokens.next().map(|m| m.as_str()).unwrap_or("") {
            "y" | "year" | "years" => {
                let d = Date::from_calendar_date(now.year() - num, now.month(), now.day())?;
                now = now.replace_date(d);
            },
            "m" | "month" | "months" => {
                let mut month = now.month();
                let mut year = now.year();
                for _ in 0..num {
                    month = month.previous();
                    if month == time::Month::December {
                        year -= 1;
                    }
                }
                let d = Date::from_calendar_date(year, month, now.day())?;
                now = now.replace_date(d);
            },
            "w" | "week" | "weeks" => now -= num * Duration::WEEK,
            "d" | "day" | "days" => now -= num * Duration::DAY,
            "h" | "hour" | "hours" => now -= num * Duration::HOUR,
            "min" | "mins" | "minute" | "minutes" => now -= num * Duration::MINUTE,
            "s" | "sec" | "secs" | "second" | "seconds" => now -= num * Duration::SECOND,
            o => bail!("bad span {:?}", o),
        };
    }

    if !at_least_one {
        bail!("No token found");
    }
    Ok(now.unix_timestamp())
}

/// Parse rfc3339-like format with added flexibility
fn parse_date_yyyymmdd(s: &str, offset: UtcOffset) -> Result<i64, Error> {
    use time::format_description::{modifier::*, Component, FormatItem::*};
    let mut p = Parsed::new().with_hour_24(0)
                             .unwrap()
                             .with_minute(0)
                             .unwrap()
                             .with_second(0)
                             .unwrap()
                             .with_offset_hour(offset.whole_hours())
                             .unwrap()
                             .with_offset_minute_signed(offset.minutes_past_hour())
                             .unwrap()
                             .with_offset_second_signed(offset.seconds_past_minute())
                             .unwrap();
    // See <https://github.com/time-rs/time/issues/428>
    let rest = p.parse_items(s.as_bytes(), &[
        Component(Component::Year(Year::default())),
        Literal(b"-"),
        Component(Component::Month(Month::default())),
        Literal(b"-"),
        Component(Component::Day(Day::default())),
        Optional(&Compound(&[
            First(&[
                Literal(b"T"),
                Literal(b" ")
            ]),
            Component(Component::Hour(Hour::default())),
            Literal(b":"),
            Component(Component::Minute(Minute::default())),
            Optional(&Compound(&[
                Literal(b":"),
                Component(Component::Second(Second::default()))
            ]))
        ]))
    ])?;
    if !rest.is_empty() {
        bail!("Junk at end")
    }
    Ok(OffsetDateTime::try_from(p)?.unix_timestamp())
}

#[derive(Debug, Clone, Copy, clap::ValueEnum)]
pub enum Timespan {
    #[clap(id("y"))]
    Year,
    #[clap(id("m"))]
    Month,
    #[clap(id("w"))]
    Week,
    #[clap(id("d"))]
    Day,
}
impl Timespan {
    /// Given a unix timestamp, advance to the beginning of the next year/month/week/day.
    pub fn next(&self, ts: i64, offset: UtcOffset) -> i64 {
        let d = OffsetDateTime::from_unix_timestamp(ts).unwrap().to_offset(offset).date();
        let d2 = match self {
            Timespan::Year => Date::from_calendar_date(d.year() + 1, Month::January, 1).unwrap(),
            Timespan::Month => {
                let year = if d.month() == Month::December { d.year() + 1 } else { d.year() };
                Date::from_calendar_date(year, d.month().next(), 1).unwrap()
            },
            Timespan::Week => {
                let til_monday = match d.weekday() {
                    Weekday::Monday => 7,
                    Weekday::Tuesday => 6,
                    Weekday::Wednesday => 5,
                    Weekday::Thursday => 4,
                    Weekday::Friday => 3,
                    Weekday::Saturday => 2,
                    Weekday::Sunday => 1,
                };
                d.checked_add(Duration::days(til_monday)).unwrap()
            },
            Timespan::Day => d.checked_add(Duration::DAY).unwrap(),
        };
        let res = d2.with_hms(0, 0, 0).unwrap().assume_offset(offset).unix_timestamp();
        debug!("{} + {:?} = {}", fmt_utctime(ts), self, fmt_utctime(res));
        res
    }

    pub fn at(&self, ts: i64, offset: UtcOffset) -> String {
        let d = OffsetDateTime::from_unix_timestamp(ts).unwrap().to_offset(offset);
        match self {
            Timespan::Year => d.format(format_description!("[year]")).unwrap(),
            Timespan::Month => d.format(format_description!("[year]-[month]")).unwrap(),
            Timespan::Week => d.format(format_description!("[year]-[week_number]")).unwrap(),
            Timespan::Day => d.format(format_description!("[year]-[month]-[day]")).unwrap(),
        }
    }

    pub fn name(&self) -> &'static str {
        match self {
            Timespan::Year => "Year",
            Timespan::Month => "Month",
            Timespan::Week => "Week",
            Timespan::Day => "Date",
        }
    }
}

/// Wrapper around a duration (seconds) to implement `table::Disp`
pub struct FmtDur(pub i64);
impl crate::table::Disp for FmtDur {
    fn out(&self, buf: &mut Vec<u8>, st: &Styles) -> usize {
        use std::io::Write;
        use DurationStyle::*;
        let sec = self.0;
        let dur = st.dur.val;
        let start = buf.len();
        match st.dur_t {
            _ if sec < 0 => wtb!(buf, "{dur}?"),
            HMS if sec >= 3600 => {
                wtb!(buf, "{dur}{}:{:02}:{:02}", sec / 3600, sec % 3600 / 60, sec % 60)
            },
            HMS if sec >= 60 => wtb!(buf, "{dur}{}:{:02}", sec % 3600 / 60, sec % 60),
            HMS | Secs => wtb!(buf, "{dur}{sec}"),
            HMSFixed => wtb!(buf, "{dur}{}:{:02}:{:02}", sec / 3600, sec % 3600 / 60, sec % 60),
            Human if sec == 0 => wtb!(buf, "{dur}0 second"),
            Human => {
                let a = [(sec / 86400, "day"),
                         (sec % 86400 / 3600, "hour"),
                         (sec % 3600 / 60, "minute"),
                         (sec % 60, "second")];
                let mut prefix = dur;
                for (num, what) in a.into_iter().filter(|(n, _)| *n > 0) {
                    wtb!(buf, "{prefix}{num} {what}{}", if num > 1 { "s" } else { "" });
                    prefix = ", ";
                }
            },
        }
        buf.len() - start - st.dur.val.len()
    }
}

#[cfg(test)]
mod test {
    use super::*;
    use std::convert::TryInto;
    use time::{format_description::well_known::Rfc3339, Weekday};

    fn parse_3339(s: &str) -> OffsetDateTime {
        OffsetDateTime::parse(s, &Rfc3339).expect(s)
    }
    fn ts(t: OffsetDateTime) -> i64 {
        t.unix_timestamp()
    }

    #[test]
    fn date() {
        let then =
            OffsetDateTime::parse("2018-04-03T00:00:00Z", &Rfc3339).unwrap().unix_timestamp();
        let now = epoch_now();
        let (day, hour, min) = (60 * 60 * 24, 60 * 60, 60);
        let tz_utc = UtcOffset::UTC;

        // Absolute dates
        assert_eq!(Ok(then), parse_date(" 1522713600 ", tz_utc));
        assert_eq!(Ok(then), parse_date(" 2018-04-03 ", tz_utc));
        assert_eq!(Ok(then + hour + min), parse_date("2018-04-03 01:01", tz_utc));
        assert_eq!(Ok(then + hour + min + 1), parse_date("2018-04-03 01:01:01", tz_utc));
        assert_eq!(Ok(then + hour + min + 1), parse_date("2018-04-03T01:01:01", tz_utc));

        // Different timezone (not calling `get_utcoffset()` because tests are threaded, which makes
        // `UtcOffset::current_local_offset()` error out)
        for secs in [hour, -1 * hour, 90 * min, -90 * min] {
            let offset = dbg!(UtcOffset::from_whole_seconds(secs.try_into().unwrap()).unwrap());
            assert_eq!(Ok(then - secs), parse_date("2018-04-03T00:00", offset));
        }

        // Relative dates
        assert_eq!(Ok(now - hour - 3 * day - 45), parse_date("1 hour, 3 days  45sec", tz_utc));
        assert_eq!(Ok(now - 5 * 7 * day), parse_date("5 weeks", tz_utc));

        // Failure cases
        assert!(parse_date("", tz_utc).is_err());
        assert!(parse_date("junk2018-04-03T01:01:01", tz_utc).is_err());
        assert!(parse_date("2018-04-03T01:01:01junk", tz_utc).is_err());
        assert!(parse_date("152271000o", tz_utc).is_err());
        assert!(parse_date("1 day 3 centuries", tz_utc).is_err());
        assert!(parse_date("a while ago", tz_utc).is_err());
    }

    #[test]
    fn timespan_next_() {
        for t in [// input             year       month      week       day
                  "2019-01-01T00:00:00 2020-01-01 2019-02-01 2019-01-07 2019-01-02",
                  "2019-01-01T23:59:59 2020-01-01 2019-02-01 2019-01-07 2019-01-02",
                  "2019-01-30T00:00:00 2020-01-01 2019-02-01 2019-02-04 2019-01-31",
                  "2019-01-31T00:00:00 2020-01-01 2019-02-01 2019-02-04 2019-02-01",
                  "2019-12-31T00:00:00 2020-01-01 2020-01-01 2020-01-06 2020-01-01",
                  "2020-02-28T12:34:00 2021-01-01 2020-03-01 2020-03-02 2020-02-29"]
        {
            // Convert the test string into test data (base input, and results depending on
            // timespan). The same test data works whatever the timeone, but the actual timestamp
            // returned by the function is offset.
            let v: Vec<&str> = t.split_whitespace().collect();
            let (base_s, year_s, month_s, week_s, day_s) = (v[0], v[1], v[2], v[3], v[4]);
            let base_utc = parse_3339(&format!("{base_s}+00:00"));
            for offset_s in ["+00:00", "+05:00", "-10:30"] {
                let base = parse_3339(&format!("{base_s}{offset_s}"));
                let year = parse_3339(&format!("{year_s}T00:00:00{offset_s}"));
                let month = parse_3339(&format!("{month_s}T00:00:00{offset_s}"));
                let week = parse_3339(&format!("{week_s}T00:00:00{offset_s}"));
                let day = parse_3339(&format!("{day_s}T00:00:00{offset_s}"));
                // Check our test data is correct
                let offset = base.offset();
                assert!(base < year && base < month && base < week && base < day,
                        "{base} < {year} / {month} / {week} / {day}");
                assert_eq!(ts(base), ts(base_utc) - offset.whole_seconds() as i64);
                assert_eq!(Month::January, year.month());
                assert_eq!(1, year.day());
                assert_eq!(1, month.day());
                assert_eq!(Weekday::Monday, week.weekday());
                // Check the tested code is correct
                assert_eq!(ts(year), Timespan::Year.next(ts(base), offset), "{base} Y {year}");
                assert_eq!(ts(month), Timespan::Month.next(ts(base), offset), "{base} M {month}");
                assert_eq!(ts(week), Timespan::Week.next(ts(base), offset), "{base} W {week}");
                assert_eq!(ts(day), Timespan::Day.next(ts(base), offset), "{base} D {day}");
            }
        }
    }

    #[test]
    fn duration() {
        for (hms, fixed, secs, human, i) in
            [("0", "0:00:00", "0", "0 second", 0),
             ("1", "0:00:01", "1", "1 second", 1),
             ("59", "0:00:59", "59", "59 seconds", 59),
             ("1:00", "0:01:00", "60", "1 minute", 60),
             ("1:01", "0:01:01", "61", "1 minute, 1 second", 61),
             ("59:59", "0:59:59", "3599", "59 minutes, 59 seconds", 3599),
             ("1:00:00", "1:00:00", "3600", "1 hour", 3600),
             ("48:00:01", "48:00:01", "172801", "2 days, 1 second", 172801),
             ("99:59:59", "99:59:59", "359999", "4 days, 3 hours, 59 minutes, 59 seconds", 359999),
             ("100:00:00", "100:00:00", "360000", "4 days, 4 hours", 360000),
             ("?", "?", "?", "?", -1),
             ("?", "?", "?", "?", -123456)]
        {
            for (st, exp) in [("hms", hms), ("hmsfixed", fixed), ("secs", secs), ("human", human)] {
                let mut buf = vec![];
                FmtDur(i).out(&mut buf, &Styles::from_str(format!("emlop l --color=n --dur {st}")));
                assert_eq!(exp, &String::from_utf8(buf).unwrap());
            }
        }
    }
}