ixdtf/

lib.rs

// 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 ).

//! Parsers for extended date time string and Duration parsing.
//!
//! The [Internet Extended Date/Time Fmt (IXDTF)][rfc9557] is laid out by RFC 9557. RFC 9557
//! builds on RFC 3339's time stamp specification and ISO 8601 to provide an optional extension
//! syntax for date/time strings.
//!
//! RFC 9557 also updates the interpretation of `Z` from RFC 3339.
//!
//! # Date Time Extended Examples
//!
//! - `2024-03-02T08:48:00-05:00[America/New_York]`
//! - `2024-03-02T08:48:00-05:00[-05:00]`
//! - `2024-03-02T08:48:00-05:00[u-ca=iso8601]`
//!
//! ## Example Usage
//!
//! ```
//! use ixdtf::parsers::{
//!     records::{Sign, TimeZoneRecord},
//!     IxdtfParser,
//! };
//!
//! let ixdtf_str = "2024-03-02T08:48:00-05:00[America/New_York]";
//!
//! let result = IxdtfParser::from_str(ixdtf_str).parse().unwrap();
//!
//! let date = result.date.unwrap();
//! let time = result.time.unwrap();
//! let offset = result.offset.unwrap().resolve_rfc_9557();
//! let tz_annotation = result.tz.unwrap();
//!
//! assert_eq!(date.year, 2024);
//! assert_eq!(date.month, 3);
//! assert_eq!(date.day, 2);
//! assert_eq!(time.hour, 8);
//! assert_eq!(time.minute, 48);
//! assert_eq!(offset.sign(), Sign::Negative);
//! assert_eq!(offset.hour(), 5);
//! assert_eq!(offset.minute(), 0);
//! assert_eq!(offset.second(), None);
//! assert_eq!(offset.fraction(), None);
//! assert!(!tz_annotation.critical);
//! assert_eq!(
//!     tz_annotation.tz,
//!     TimeZoneRecord::Name("America/New_York".as_bytes())
//! );
//! ```
//!
//! ## Date/Time Strings
//!
//! The extended suffixes laid out by RFC 9557 are optional, so the `IxdtfParser`
//! will also still parse any valid date time strings described by RFC3339.
//!
//! Example Valid Date Time Strings:
//!
//! - `2024-03-02`
//! - `+002024-03-02`
//! - `20240302`
//! - `+0020240302`
//! - `2024-03-02T08:48:00`
//! - `2024-03-02T08:48:00`
//!
//! ## Updates to Zulu interpretation from RFC 3339
//!
//! RFC 3339 interpreted both `+00:00` and `Z` "UTC is the preferred reference point for the
//! specified time"; meanwhile, `-00:00` expressed "the time in UTC is known, but the local
//! time is unknown".
//!
//! RFC 9557 updates the interpretation of `Z` to align with `-00:00`.
//!
//! ```rust
//! use ixdtf::parsers::{
//!     records::{Sign, TimeZoneRecord},
//!     IxdtfParser,
//! };
//!
//! let ixdtf_str = "2024-03-02T08:48:00Z[America/New_York]";
//!
//! let result = IxdtfParser::from_str(ixdtf_str).parse().unwrap();
//!
//! let date = result.date.unwrap();
//! let time = result.time.unwrap();
//! let offset = result.offset.unwrap().resolve_rfc_9557();
//! let tz_annotation = result.tz.unwrap();
//!
//! assert_eq!(date.year, 2024);
//! assert_eq!(date.month, 3);
//! assert_eq!(date.day, 2);
//! assert_eq!(time.hour, 8);
//! assert_eq!(time.minute, 48);
//! assert_eq!(offset.sign(), Sign::Negative);
//! assert_eq!(offset.hour(), 0);
//! assert_eq!(offset.minute(), 0);
//! assert_eq!(offset.second(), None);
//! assert_eq!(offset.fraction(), None);
//! assert!(!tz_annotation.critical);
//! assert_eq!(
//!     tz_annotation.tz,
//!     TimeZoneRecord::Name("America/New_York".as_bytes())
//! );
//! ```
//!
//! For more information on the update to RFC 3339, please see RFC 9557, Section 2.
//!
//! For more information on `Z` along with time zone annotations, please see the Annotations
//! with Application Defined Behavior section below.
//!
//! ## IXDTF Extensions: A Deeper Look
//!
//! The suffix extensions come in two primary kinds: a time zone annotation and a key-value
//! annotation. The suffixes may also be flagged as critical with a `!` as a leading flag
//! character.
//!
//! ### Time Zone Annotations
//!
//! Time zone annotations can be either a valid IANA time zone name or numeric
//! offset.
//!
//! #### Valid Time Zone Annotations
//!
//! - `2024-03-02T08:48:00-5:00[America/New_York]`
//! - `2024-03-02T08:48:00-5:00[-05:00]`
//! - `2024-03-02T08:48:00Z[America/New_York]`
//!
//! ##### Time Zone Consistency
//!
//! With the update to RFC 3339, when `Z` is provided as a datetime offset along side a time zone
//! annotation, the IXDTF string is not considered inconsistent as `Z` does not assert any local
//! time. Instead, an application may decide to calculate the time with the rules of the time
//! zone annotation if it is provided.
//!
//! ```rust
//! use ixdtf::parsers::{
//!     records::{Sign, TimeZoneRecord},
//!     IxdtfParser,
//! };
//!
//! let zulu_offset = "2024-03-02T08:48:00Z[!America/New_York]";
//!
//! let result = IxdtfParser::from_str(zulu_offset).parse().unwrap();
//!
//! let tz_annotation = result.tz.unwrap();
//! let offset = result.offset.unwrap().resolve_rfc_9557();
//!
//! // The offset is `Z`/`-00:00`, so the application can use the rules of
//! // "America/New_York" to calculate the time for IXDTF string.
//! assert_eq!(offset.sign(), Sign::Negative);
//! assert_eq!(offset.hour(), 0);
//! assert_eq!(offset.minute(), 0);
//! assert_eq!(offset.second(), None);
//! assert_eq!(offset.fraction(), None);
//! assert!(tz_annotation.critical);
//! assert_eq!(
//!     tz_annotation.tz,
//!     TimeZoneRecord::Name("America/New_York".as_bytes())
//! );
//! ```
//!
//! ### Key-Value Annotations
//!
//! Key-value pair annotations are any key and value string separated by a '=' character.
//! Key-value pairs are can include any information. Keys may be permanently registered,
//! provisionally registered, or unknown; however, only permanent keys are acted on by
//! `IxdtfParser`.
//!
//! If duplicate registered keys are provided the first key will be returned, unless one
//! of the duplicate annotations is marked as critical, in which case an error may be
//! thrown by the `ixdtf` (See [Invalid Annotations](#invalid-annotations) for more
//! information).
//!
//! #### Permanent Registered Keys
//!
//! - `u-ca`
//!
//! #### Valid Annotations
//!
//! - (1) `2024-03-02T08:48:00-05:00[America/New_York][u-ca=iso8601]`
//! - (2) `2024-03-02T08:48:00-05:00[u-ca=iso8601][u-ca=japanese]`
//! - (3) `2024-03-02T08:48:00-05:00[u-ca=iso8601][!u-ca=iso8601]`
//! - (4) `2024-03-02T08:48:00-05:00[u-ca=iso8601][answer-to-universe=fortytwo]`
//!
//! ##### Example 1
//!
//! This is a basic annotation string that has a Time Zone and calendar annotation.
//!
//! ##### Example 2
//!
//! This example is duplicate and different calendar annotations, but neither calendar
//! is flagged as critical so the first calendar is returned while the second calendar
//! is ignored.
//!
//! ##### Example 3
//!
//! This example is a duplicate and identical calendar annotations with one annotation flagged
//! as critical. As the annotations are identical values, there is no ambiguity with the use of
//! the critical flag that may cause an error. Thus, the first annotation is returned, and the
//! second is ignored (See [Annotations with Application Defined
//! Behavior](#annotations-with-application-defined-behavior)).
//!
//! ##### Example 4
//!
//! This example contains an unknown annotation. The annotation is not marked as critical
//! so the value is ignored (See [Implementing Annotation Handlers](#implementing-annotation-handlers)).
//!
//! #### Invalid Annotations
//!
//! The below `ixdtf` strings have invalid annotations that will cause an error
//! to be thrown (NOTE: these are not to be confused with potentially invalid
//! annotations with application defined behavior).
//!
//! - (1) `2024-03-02T08:48:00-05:00[u-ca=iso8601][America/New_York]`
//! - (2) `2024-03-02T08:48:00-05:00[u-ca=iso8601][!u-ca=japanese]`
//! - (3) `2024-03-02T08:48:00-05:00[u-ca=iso8601][!answer-to-universe=fortytwo]`
//!
//! ##### Example 1
//!
//! This example shows a Time Zone annotation that is not currently in the correct
//! order with the key value. When parsing this invalid annotation, `ixdtf`
//! will attempt to parse the Time Zone annotation as a key-value annotation.
//!
//! ```rust
//! use ixdtf::{parsers::IxdtfParser, ParseError};
//!
//! let example_one =
//!     "2024-03-02T08:48:00-05:00[u-ca=iso8601][America/New_York]";
//!
//! let result = IxdtfParser::from_str(example_one).parse();
//!
//! assert_eq!(result, Err(ParseError::AnnotationKeyLeadingChar));
//! ```
//!
//! ##### Example 2
//!
//! This example shows a duplicate registered key; however, in this case, one
//! of the registered keys is flagged as critical, which throws an error as
//! the ixdtf string must be treated as erroneous
//!
//! ```rust
//! use ixdtf::{parsers::IxdtfParser, ParseError};
//!
//! let example_two = "2024-03-02T08:48:00-05:00[u-ca=iso8601][!u-ca=japanese]";
//!
//! let result = IxdtfParser::from_str(example_two).parse();
//!
//! assert_eq!(result, Err(ParseError::CriticalDuplicateCalendar));
//! ```
//!
//! ##### Example 3
//!
//! This example shows an unknown key flagged as critical. `ixdtf` will return an
//! error on an unknown flag being flagged as critical.
//!
//! ```rust
//! use ixdtf::{parsers::IxdtfParser, ParseError};
//!
//! let example_three =
//!     "2024-03-02T08:48:00-05:00[u-ca=iso8601][!answer-to-universe=fortytwo]";
//!
//! let result = IxdtfParser::from_str(example_three).parse();
//!
//! assert_eq!(result, Err(ParseError::UnrecognizedCritical));
//! ```
//!
//! #### Annotations with Application Defined Behavior
//!
//! The below options may be viewed as valid or invalid depending on application defined
//! behavior. Where user defined behavior might be required, the `ixdtf` crate applies
//! the logic in the least restrictive interpretation and provides optional callbacks
//! for the user to define stricter behavior.
//!
//! - (1) `2024-03-02T08:48:00-05:00[u-ca=japanese][!u-ca=japanese]`
//! - (2) `2024-03-02T08:48:00+01:00[America/New_York]`
//!
//! ##### Example 1
//!
//! This example shows a critical duplicate calendar where the annotation value is identical. RFC 9557 is
//! ambiguous on whether this should be rejected for inconsistency. `ixdtf` treats these values
//! as consistent, and, therefore, okay. However, an application may wish to handle this duplicate
//! critical calendar value as inconsistent (See [Implementing Annotation Handlers](#implementing-annotation-handlers)).
//!
//! ##### Example 2
//!
//! This example shows an ambiguous Time Zone caused by a misalignment
//! of the offset and the Time Zone annotation. It is up to the user to handle this ambiguity
//! between the offset and annotation.
//!
//! ```rust
//! use ixdtf::parsers::{IxdtfParser, records::TimeZoneRecord};
//!
//! let example_two = "2024-03-02T08:48:00+01:00[!America/New_York]";
//!
//! let result = IxdtfParser::from_str(example_two).parse().unwrap();
//!
//! let tz_annotation = result.tz.unwrap();
//! let offset = result.offset.unwrap().resolve_rfc_9557();
//!
//! // The time zone annotation and offset conflict with each other, and must therefore be
//! // resolved by the user.
//! assert!(tz_annotation.critical);
//! assert_eq!(tz_annotation.tz, TimeZoneRecord::Name("America/New_York".as_bytes()));
//! assert_eq!(offset.hour(), 1);
//! ```
//!
//! #### Implementing Annotation Handlers
//!
//! As mentioned in the prior section, there may be times where an application may
//! need to implement application defined behavior for user defined functionality.
//! In this instance, `ixdtf` provides a `*_with_annotation_handler` method that
//! allows to the user to provide a callback.
//!
//! A handler is defined as `handler: impl FnMut(Annotation<'a>) -> Option<Annotation<'a>>`
//! where `ixdtf` provides visibility to an annotation to the user. The call to this callback
//! occurs prior to the `ixdtf`'s processing of the annotation, and will only occur if the
//! annotation is provided back to `ixdtf`.
//!
//! If the user wishes to ignore any `ixdtf`'s errors, then they may return `None`, which
//! results in a no-op for that annotation.
//!
//! Unless the user’s application has a specific reason to bypass action on an annotation,
//! such as, custom unknown key handling or superceding a calendar based on it’s critical
//! flag, it is recommended to return the annotation value.
//!
//! ##### Handler Example
//!
//! A user may wish to implement a custom key in an annotation set. This can be completed
//! with custom handler.
//!
//! ```rust
//! use ixdtf::parsers::IxdtfParser;
//!
//! let example_with_custom_key = "2024-03-02T08:48:00-05:00[u-ca=iso8601][!answer-to-universe=fortytwo]";
//!
//! let mut answer = None;
//!
//! let _ = IxdtfParser::from_str(example_with_custom_key).parse_with_annotation_handler(|annotation| {
//!     if annotation.key == "answer-to-universe".as_bytes() {
//!         answer.get_or_insert(annotation);
//!         // Found our value! We don't need `ixdtf` to handle this annotation.
//!         return None
//!     }
//!     // The annotation is not our custom annotation, so we return
//!     // the value back for regular logic.
//!     Some(annotation)
//! }).unwrap();
//!
//! let answer = answer.unwrap();
//!
//! assert!(answer.critical);
//! assert_eq!(answer.value, "fortytwo".as_bytes());
//! ```
//!
//! It is worth noting that in the above example the annotation above found is a critically flagged
//! unknown key. RFC 9557 and `ixdtf` considers unknown critical keys as invalid. However, handlers
//! allow the user to define any known keys of their own and therefore also handle the logic around
//! criticality.
//!
//! ## Additional grammar resources
//!
//! Additional resources for Date and Time string grammar can be found in [RFC3339][rfc3339]
//! and the [Temporal proposal][temporal-grammar].
//!
//! ## Additional Feature
//!
//! The `ixdtf` crate also implements an ISO8601 Duration parser (`IsoDurationParser`) that is available under
//! the `duration` feature flag. The API for `IsoDurationParser` is the same as `IxdtfParser`, but
//! parses duration strings over date/time strings.
//!
//! [rfc9557]: https://datatracker.ietf.org/doc/rfc9557/
//! [rfc3339]: https://datatracker.ietf.org/doc/html/rfc3339
//! [temporal-grammar]: https://tc39.es/proposal-temporal/#sec-temporal-iso8601grammar

#![no_std]
#![cfg_attr(
    not(test),
    deny(
        clippy::indexing_slicing,
        clippy::unwrap_used,
        clippy::expect_used,
        clippy::panic,
        clippy::exhaustive_structs,
        clippy::exhaustive_enums,
        clippy::trivially_copy_pass_by_ref,
        missing_debug_implementations,
    )
)]

mod error;
pub mod parsers;

extern crate alloc;

pub use error::ParseError;

/// The `ixdtf` crate's Result type.
pub type ParserResult<T> = Result<T, ParseError>;