libhaystack 3.2.0

Rust implementation of the Haystack 4 data types, defs, filter, units, and encodings
Documentation 
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// Copyright (C) 2020 - 2022, J2 Innovations

//! Haystack Timezone configured to work with the full IANA database
//! provided by chrono_tz.

use chrono::{DateTime as StdDateTime, FixedOffset, TimeZone, Utc};

use chrono_tz::{OffsetName, Tz, UTC};

use crate::timezone::fixed_timezone;

/// DateTime type that supports timezones
pub type DateTimeType = StdDateTime<Tz>;

pub fn make_date_time(date: StdDateTime<FixedOffset>) -> Result<DateTimeType, String> {
    use chrono::LocalResult;
    if let Ok(tz) = find_timezone(&fixed_timezone(&date.offset().to_string())) {
        Ok(match tz.from_local_datetime(&date.naive_local()) {
            LocalResult::Single(val) => val,
            LocalResult::Ambiguous(v1, _) => v1,
            LocalResult::None => return Err(format!("Can't create datetime with timezone {tz}")),
        })
    } else {
        Err("Invalid timezone".into())
    }
}

/// Constructs a datetime with the timezone
pub fn make_date_time_with_tz(
    datetime: &StdDateTime<FixedOffset>,
    tz: &str,
) -> Result<DateTimeType, String> {
    if let Ok(tz) = find_timezone(tz) {
        Ok(datetime.with_timezone(&tz))
    } else {
        Err(format!("Can't create datetime with timezone {tz}"))
    }
}

pub fn utc_now() -> DateTimeType {
    Utc::now().with_timezone(&UTC)
}

pub fn is_utc(date: &DateTimeType) -> bool {
    date.timezone() == UTC
}

pub fn timezone_short_name(date: &DateTimeType) -> String {
    let tz_id = date.offset().tz_id();

    tz_id[tz_id.find('/').map_or(0, |v| v + 1)..].to_string()
}

static PREFIXES: [&str; 18] = [
    "Africa",
    "America",
    "Asia",
    "Atlantic",
    "Australia",
    "Brazil",
    "Canada",
    "Chile",
    "Etc",
    "Europe",
    "Indian",
    "Mexico",
    "Pacific",
    "US",
    "America/Argentina",
    "America/Indiana",
    "America/Kentucky",
    "America/North_Dakota",
];

fn find_timezone(name: &str) -> Result<Tz, String> {
    name.parse().or_else(|err: chrono_tz::ParseError| {
        PREFIXES
            .into_iter()
            .find_map(|prefix| format!("{prefix}/{name}").parse().ok())
            .ok_or(err.to_string())
    })
}