use std::io::Write;

use crate::models::Entry;
use crate::error::Result;

const ICAL_TIME_FORMAT: &'static str = "%Y%m%dT%H%M%SZ";

pub fn print_formatted<W: Write>(entries: Vec<Entry>, out: &mut W) -> Result<()> {
    writeln!(out, "BEGIN:VCALENDAR")?;
    writeln!(out, "CALSCALE:GREGORIAN")?;
    writeln!(out, "METHOD:PUBLISH")?;
    writeln!(out, "PRODID:tiempo-rs")?;
    writeln!(out, "VERSION:2.0")?;

    let hostname = hostname::get()?;
    let host = hostname.to_string_lossy();

    for entry in entries.into_iter().filter(|e| e.end.is_some()) {
        let uid = format!("tiempo-{id}", id=entry.id);
        let note = entry.note.unwrap_or("".into());

        writeln!(out, "BEGIN:VEVENT")?;
        writeln!(out, "DESCRIPTION:{note}", note=note)?;
        writeln!(out, "DTEND:{end}", end=entry.end.unwrap().format(ICAL_TIME_FORMAT).to_string())?;
        writeln!(out, "DTSTAMP:{start}", start=entry.start.format(ICAL_TIME_FORMAT).to_string())?;
        writeln!(out, "DTSTART:{start}", start=entry.start.format(ICAL_TIME_FORMAT).to_string())?;
        writeln!(out, "SEQUENCE:0")?;
        writeln!(out, "SUMMARY:{note}", note=note)?;
        writeln!(out, "UID:{uid}@{host}", uid=uid, host=host)?;
        writeln!(out, "END:VEVENT")?;
    }

    writeln!(out, "END:VCALENDAR")?;

    Ok(())
}

#[cfg(test)]
mod tests {
    use pretty_assertions::assert_eq;
    use chrono::{Utc, Duration};

    use crate::test_utils::PrettyString;

    use super::*;

    #[test]
    fn ical_format() {
        let now = Utc::now();
        let an_hour_ago = now - Duration::hours(1);
        let entries = vec![
            Entry::new_sample(1, an_hour_ago, Some(now)),
            Entry::new_sample(2, an_hour_ago, None),
        ];

        let mut out = Vec::new();

        print_formatted(entries, &mut out).unwrap();

        let host = hostname::get().unwrap();
        let host = host.to_string_lossy();

        assert_eq!(PrettyString(&String::from_utf8_lossy(&out)), PrettyString(&format!("BEGIN:VCALENDAR
CALSCALE:GREGORIAN
METHOD:PUBLISH
PRODID:tiempo-rs
VERSION:2.0
BEGIN:VEVENT
DESCRIPTION:{note}
DTEND:{end}
DTSTAMP:{start}
DTSTART:{start}
SEQUENCE:0
SUMMARY:{note}
UID:tiempo-{id}@{host}
END:VEVENT
END:VCALENDAR
", note="entry 1", end=now.format(ICAL_TIME_FORMAT).to_string(),
        start=an_hour_ago.format(ICAL_TIME_FORMAT).to_string(), id=1, host=host)));
    }
}