use chrono::*;

use crate::utils::fileutil;
use std::env;
use std::path::PathBuf;

pub fn date_from_str(date_str: &str) -> ParseResult<Date<Local>> {
    if date_str == "today" || date_str == "now" {
        return Ok(Local::now().date());
    }
    let naive_date = &NaiveDate::parse_from_str(date_str, "%Y-%m-%d")?;
    Ok(Local.from_local_date(naive_date).unwrap())
}

pub fn datetime_from_str(datetime_str: &str) -> ParseResult<DateTime<Local>> {
    if datetime_str == "now" {
        return Ok(Local::now());
    }
    let naive_datetime = &NaiveDateTime::parse_from_str(datetime_str, "%Y-%m-%dT%H:%M")?;
    Ok(Local.from_local_datetime(naive_datetime).unwrap())
}

pub fn week_from_str_begin(date_str: &str) -> Result<Date<Local>, String> {
    let now = Local::now();
    if date_str == "toweek" || date_str == "thisweek" {
        return Ok(Local.isoywd(now.year(), now.iso_week().week(), Weekday::Mon));
    }
    if let Ok(date) = &NaiveDate::parse_from_str(&format!("{}-1", date_str), "%G-W%V-%u") {
        return Ok(Local.from_local_date(date).unwrap());
    }
    if let Ok(date) =
        &NaiveDate::parse_from_str(&format!("{}-{}-1", now.year(), date_str), "%G-W%V-%u")
    {
        return Ok(Local.from_local_date(date).unwrap());
    }
    Err("Could not parse '{}' as week".to_string())
}

pub fn find_local_timezone() -> String {
    if let Ok(candidate) = env::var("TZ") {
        return candidate;
    }
    if let Ok(candidate) = fileutil::read_file_to_string(&PathBuf::from("/etc/timezone")) {
        return candidate.trim().to_owned();
    }
    if let Ok(candidate) = fileutil::read_file_to_string(&PathBuf::from("/etc/localtime")) {
        return candidate.trim().to_owned();
    }
    "UTC".to_owned()
}

#[cfg(not(test))]
pub fn now() -> DateTime<Utc> {
    Utc::now()
}

#[cfg(test)]
pub fn now() -> DateTime<Utc> {
    use crate::testdata;
    *testdata::NOW_TEST
}

pub fn week_from_str_end(date_str: &str) -> Result<Date<Local>, String> {
    let now = Local::now();
    if date_str == "toweek" || date_str == "thisweek" {
        return Ok(Local.isoywd(now.year(), now.iso_week().week(), Weekday::Sun));
    }
    if let Ok(date) = &NaiveDate::parse_from_str(&format!("{}-7", date_str), "%G-W%V-%u") {
        return Ok(Local.from_local_date(date).unwrap());
    }
    if let Ok(date) =
        &NaiveDate::parse_from_str(&format!("{}-{}-7", now.year(), date_str), "%G-W%V-%u")
    {
        return Ok(Local.from_local_date(date).unwrap());
    }
    Err("Could not parse '{}' as week".to_string())
}

pub fn datetime_from_timestamp(timestamp: &str) -> Option<DateTime<Local>> {
    let timestamp_i64 = timestamp.parse::<i64>().ok()?;
    let naive_datetime = NaiveDateTime::from_timestamp_opt(timestamp_i64, 0)?;
    let utc_time: DateTime<Utc> = DateTime::from_utc(naive_datetime, Utc);
    Some(utc_time.with_timezone(&Local))
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_date_from_str() {
        let date = date_from_str("2018-12-10").unwrap();
        assert_eq!("2018-12-10", format!("{}", date.format("%F")));
        let date = date_from_str("today").unwrap();
        assert_eq!(Local::now().date(), date);
        let date = date_from_str("now").unwrap();
        assert_eq!(Local::now().date(), date);
    }

    #[test]
    #[should_panic]
    fn test_date_from_str_negative() {
        date_from_str("2018-02-30").unwrap();
    }

    #[test]
    fn test_week_from_str_begin() {
        let date = week_from_str_begin("2018-W50").unwrap();
        assert_eq!("2018-12-10", format!("{}", date.format("%F")));
        let date = week_from_str_begin("W50").unwrap();
        assert_eq!("2019-12-09", format!("{}", date.format("%F")));
    }

    #[test]
    fn test_week_from_str_begin_current_year() {
        // TODO test must be adapted once a year. hum.
        let date = week_from_str_begin("W50").unwrap();
        assert_eq!("2019-12-09", format!("{}", date.format("%F")));
    }

    #[test]
    #[should_panic]
    fn test_week_from_str_begin_neg() {
        week_from_str_begin("nonsense").unwrap();
    }

    #[test]
    fn test_week_from_str_end() {
        let date = week_from_str_end("W50").unwrap();
        assert_eq!("2019-12-15", format!("{}", date.format("%F")));
    }
    #[test]
    fn test_week_from_str_end_current_year() {
        // TODO test must be adapted once a year. hum.
        let date = week_from_str_end("W50").unwrap();
        assert_eq!("2019-12-15", format!("{}", date.format("%F")));
    }

    #[test]
    #[should_panic]
    fn test_week_from_str_end_neg() {
        week_from_str_end("nonsense").unwrap();
    }

    #[test]
    fn test_datetime_from_timestamp() {
        let timestamp = "1547234687";
        let dt_from_ts = datetime_from_timestamp(timestamp).unwrap();
        let dt = Utc.ymd(2019, 01, 11).and_hms(19, 24, 47);
        assert_eq!(dt, dt_from_ts);
    }
}