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//! Rules defined in [ISO 8601].
//!
//! [ISO 8601]: https://www.iso.org/iso-8601-date-and-time-format.html
use core::num::NonZero;
use num_conv::prelude::*;
use crate::parsing::ParsedItem;
use crate::parsing::combinator::{ExactlyNDigits, Sign, any_digit, sign};
use crate::{Month, Weekday};
/// What kind of format is being parsed. This is used to ensure each part of the format (date, time,
/// offset) is the same kind.
#[derive(Debug, Clone, Copy)]
pub(crate) enum ExtendedKind {
/// The basic format.
Basic,
/// The extended format.
Extended,
/// ¯\_(ツ)_/¯
Unknown,
}
impl ExtendedKind {
/// Is it possible that the format is extended?
#[inline]
pub(crate) const fn maybe_extended(self) -> bool {
matches!(self, Self::Extended | Self::Unknown)
}
/// Is the format known for certain to be extended?
#[inline]
pub(crate) const fn is_extended(self) -> bool {
matches!(self, Self::Extended)
}
/// If the kind is `Unknown`, make it `Basic`. Otherwise, do nothing. Returns `Some` if and only
/// if the kind is now `Basic`.
#[inline]
pub(crate) const fn coerce_basic(&mut self) -> Option<()> {
match self {
Self::Basic => Some(()),
Self::Extended => None,
Self::Unknown => {
*self = Self::Basic;
Some(())
}
}
}
/// If the kind is `Unknown`, make it `Extended`. Otherwise, do nothing. Returns `Some` if and
/// only if the kind is now `Extended`.
#[inline]
pub(crate) const fn coerce_extended(&mut self) -> Option<()> {
match self {
Self::Basic => None,
Self::Extended => Some(()),
Self::Unknown => {
*self = Self::Extended;
Some(())
}
}
}
}
/// Parse a possibly expanded year.
#[inline]
pub(crate) fn year(input: &[u8]) -> Option<ParsedItem<'_, i32>> {
Some(match sign(input) {
Some(ParsedItem(input, sign)) => ExactlyNDigits::<6>::parse(input)?.map(|val| {
let val = val.cast_signed();
match sign {
Sign::Negative => -val,
Sign::Positive => val,
}
}),
None => ExactlyNDigits::<4>::parse(input)?.map(|val| val.cast_signed().extend()),
})
}
/// Parse a month.
#[inline]
pub(crate) fn month(input: &[u8]) -> Option<ParsedItem<'_, Month>> {
match input {
[b'0', b'1', remaining @ ..] => Some(ParsedItem(remaining, Month::January)),
[b'0', b'2', remaining @ ..] => Some(ParsedItem(remaining, Month::February)),
[b'0', b'3', remaining @ ..] => Some(ParsedItem(remaining, Month::March)),
[b'0', b'4', remaining @ ..] => Some(ParsedItem(remaining, Month::April)),
[b'0', b'5', remaining @ ..] => Some(ParsedItem(remaining, Month::May)),
[b'0', b'6', remaining @ ..] => Some(ParsedItem(remaining, Month::June)),
[b'0', b'7', remaining @ ..] => Some(ParsedItem(remaining, Month::July)),
[b'0', b'8', remaining @ ..] => Some(ParsedItem(remaining, Month::August)),
[b'0', b'9', remaining @ ..] => Some(ParsedItem(remaining, Month::September)),
[b'1', b'0', remaining @ ..] => Some(ParsedItem(remaining, Month::October)),
[b'1', b'1', remaining @ ..] => Some(ParsedItem(remaining, Month::November)),
[b'1', b'2', remaining @ ..] => Some(ParsedItem(remaining, Month::December)),
_ => None,
}
}
/// Parse a week number.
#[inline]
pub(crate) fn week(input: &[u8]) -> Option<ParsedItem<'_, NonZero<u8>>> {
ExactlyNDigits::<2>::parse(input).and_then(|parsed| parsed.flat_map(NonZero::new))
}
/// Parse a day of the month.
#[inline]
pub(crate) fn day(input: &[u8]) -> Option<ParsedItem<'_, NonZero<u8>>> {
ExactlyNDigits::<2>::parse(input).and_then(|parsed| parsed.flat_map(NonZero::new))
}
/// Parse a day of the week.
#[inline]
pub(crate) fn dayk(input: &[u8]) -> Option<ParsedItem<'_, Weekday>> {
match input {
[b'1', remaining @ ..] => Some(ParsedItem(remaining, Weekday::Monday)),
[b'2', remaining @ ..] => Some(ParsedItem(remaining, Weekday::Tuesday)),
[b'3', remaining @ ..] => Some(ParsedItem(remaining, Weekday::Wednesday)),
[b'4', remaining @ ..] => Some(ParsedItem(remaining, Weekday::Thursday)),
[b'5', remaining @ ..] => Some(ParsedItem(remaining, Weekday::Friday)),
[b'6', remaining @ ..] => Some(ParsedItem(remaining, Weekday::Saturday)),
[b'7', remaining @ ..] => Some(ParsedItem(remaining, Weekday::Sunday)),
_ => None,
}
}
/// Parse a day of the year.
#[inline]
pub(crate) fn dayo(input: &[u8]) -> Option<ParsedItem<'_, NonZero<u16>>> {
ExactlyNDigits::<3>::parse(input).and_then(|parsed| parsed.flat_map(NonZero::new))
}
/// Parse the hour.
#[inline]
pub(crate) const fn hour(input: &[u8]) -> Option<ParsedItem<'_, u8>> {
ExactlyNDigits::<2>::parse(input)
}
/// Parse the minute.
#[inline]
pub(crate) const fn min(input: &[u8]) -> Option<ParsedItem<'_, u8>> {
ExactlyNDigits::<2>::parse(input)
}
/// Parse a floating point number as its integer and optional fractional parts.
///
/// The number must have two digits before the decimal point. If a decimal point is present, at
/// least one digit must follow.
///
/// The return type is a tuple of the integer part and optional fraction part.
#[inline]
pub(crate) fn float(input: &[u8]) -> Option<ParsedItem<'_, (u8, Option<f64>)>> {
// Two digits before the decimal.
let ParsedItem(input, integer_part) = match input {
[
first_digit @ b'0'..=b'9',
second_digit @ b'0'..=b'9',
input @ ..,
] => ParsedItem(input, (first_digit - b'0') * 10 + (second_digit - b'0')),
_ => return None,
};
if let Some(ParsedItem(input, ())) = decimal_sign(input) {
// Mandatory post-decimal digit.
let ParsedItem(mut input, mut fractional_part) =
any_digit(input)?.map(|digit| ((digit - b'0') as f64) / 10.);
let mut divisor = 10.;
// Any number of subsequent digits.
while let Some(ParsedItem(new_input, digit)) = any_digit(input) {
input = new_input;
divisor *= 10.;
fractional_part += (digit - b'0') as f64 / divisor;
}
Some(ParsedItem(input, (integer_part, Some(fractional_part))))
} else {
Some(ParsedItem(input, (integer_part, None)))
}
}
/// Parse a "decimal sign", which is either a comma or a period.
#[inline]
fn decimal_sign(input: &[u8]) -> Option<ParsedItem<'_, ()>> {
match input {
[b'.' | b',', remaining @ ..] => Some(ParsedItem(remaining, ())),
_ => None,
}
}