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// This file is part of ICU4X. For terms of use, please see the file
// called LICENSE at the top level of the ICU4X source tree
// (online at: https://github.com/unicode-org/icu4x/blob/main/LICENSE ).

//! Types for resolving and manipulating time zones.
//!
//! # Fields
//!
//! In ICU4X, a [formattable time zone](TimeZoneInfo) consists of up to four different fields:
//!
//! 1. The time zone ID
//! 2. The offset from UTC
//! 3. A timestamp, as time zone names can change over time
//! 4. The zone variant, representing concepts such as Standard, Summer, Daylight, and Ramadan time
//!
//! ## Time Zone
//!
//! The time zone ID corresponds to a time zone from the time zone database. The time zone ID
//! usually corresponds to the largest city in the time zone.
//!
//! There are two mostly-interchangeable standards for time zone IDs:
//!
//! 1. IANA time zone IDs, like `"America/Chicago"`
//! 2. BCP-47 time zone IDs, like `"uschi"`
//!
//! ICU4X uses BCP-47 time zone IDs for all of its APIs. To get a BCP-47 time zone from an
//! IANA time zone, use [`TimeZoneIdMapper`].
//!
//! ## UTC Offset
//!
//! The UTC offset precisely states the time difference between the time zone in question and
//! Coordinated Universal Time (UTC).
//!
//! In localized strings, it is often rendered as "UTC-6", meaning 6 hours less than UTC (some locales
//! use the term "GMT" instead of "UTC").
//!
//! ## Timestamp
//!
//! Some time zones change names over time, such as when changing "metazone". For example, Portugal changed from
//! "Western European Time" to "Central European Time" and back in the 1990s, without changing time zone id
//! (`Europe/Lisbon`/`ptlis`). Therefore, a timestamp is needed to resolve such generic time zone names.
//!
//! It is not required to set the timestamp on [`TimeZoneInfo`]. If it is not set, some string
//! formats may be unsupported.
//!
//! ## Zone Variant
//!
//! Many zones use different names and offsets in the summer than in the winter. In ICU4X,
//! this is called the _zone variant_.
//!
//! CLDR has two zone variants, named `"standard"` and `"daylight"`. However, the mapping of these
//! variants to specific observed offsets varies from time zone to time zone, and they may not
//! consistently represent winter versus summer time.
//!
//! Note: It is not required to set the zone variant on [`TimeZoneInfo`]. If it is not set, some string
//! formats may be unsupported.
//!
//! # Examples
//!
//! ```
//! use icu::calendar::{Date, Time};
//! use icu::timezone::TimeZoneBcp47Id;
//! use icu::timezone::TimeZoneIdMapper;
//! use icu::timezone::ZoneVariant;
//! use tinystr::tinystr;
//!
//! // Parse the IANA ID
//! let id = TimeZoneIdMapper::new().iana_to_bcp47("America/Chicago");
//!
//! // Alternatively, use the BCP47 ID directly
//! let id = TimeZoneBcp47Id(tinystr!(8, "uschi"));
//!
//! // Create a TimeZoneInfo<Base> by associating the ID with an offset
//! let time_zone = id.with_offset("-0600".parse().ok());
//!
//! // Extend to a TimeZoneInfo<AtTime> by adding a local time
//! let time_zone_at_time = time_zone
//!     .at_time((Date::try_new_iso(2023, 12, 2).unwrap(), Time::midnight()));
//!
//! // Extend to a TimeZoneInfo<Full> by adding a zone variant
//! let time_zone_with_variant =
//!     time_zone_at_time.with_zone_variant(ZoneVariant::Standard);
//! ```

// https://github.com/unicode-org/icu4x/blob/main/documents/process/boilerplate.md#library-annotations
#![cfg_attr(not(any(test, feature = "std")), no_std)]
#![cfg_attr(
    not(test),
    deny(
        clippy::indexing_slicing,
        clippy::unwrap_used,
        clippy::expect_used,
        clippy::panic,
        clippy::exhaustive_structs,
        clippy::exhaustive_enums,
        missing_debug_implementations,
    )
)]
#![warn(missing_docs)]

extern crate alloc;

mod error;
mod ids;
pub mod provider;
pub mod scaffold;
mod time_zone;
mod types;
mod windows_tz;
mod zone_offset;
mod zoned_datetime;

#[cfg(feature = "ixdtf")]
mod ixdtf;
#[cfg(feature = "ixdtf")]
pub use self::ixdtf::IxdtfParser;

pub use error::InvalidOffsetError;
pub use ids::{
    TimeZoneIdMapper, TimeZoneIdMapperBorrowed, TimeZoneIdMapperWithFastCanonicalization,
    TimeZoneIdMapperWithFastCanonicalizationBorrowed,
};
pub use provider::TimeZoneBcp47Id;
pub use time_zone::models;
pub use time_zone::TimeZoneInfo;
pub use time_zone::TimeZoneModel;
pub use types::{UtcOffset, ZoneVariant};
pub use windows_tz::{WindowsTimeZoneMapper, WindowsTimeZoneMapperBorrowed};
pub use zone_offset::{ZoneOffsetCalculator, ZoneOffsets};
pub use zoned_datetime::CustomZonedDateTime;

#[cfg(all(feature = "ixdtf", feature = "compiled_data"))]
pub use crate::ixdtf::ParseError;