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use chumsky::prelude::*;
use crate::MetarError;
/// Data that is provided in a metar which might be unknown.
/// Note that this differs from an `Option<T>` field which is used when data
/// might not be given at all. In the cases where `Data<T>` is used, data is
/// usually given but has been replaced in the METAR by slashes, indicating
/// that it is not known.
#[derive(PartialEq, Eq, Copy, Clone, Debug, Hash)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub enum Data<T> {
/// The data is known and given
Known(T),
/// The data isn't or cannot be known
Unknown,
}
impl<T> Data<T> {
/// Gets a new `Data` that has a `&T` inside it.
pub fn as_ref(&self) -> Data<&T> {
match *self {
Data::Known(ref v) => Data::Known(v),
Data::Unknown => Data::Unknown,
}
}
/// Gets a new `Data` that has a `&mut T` inside it.
pub fn as_mut(&mut self) -> Data<&mut T> {
match *self {
Data::Known(ref mut v) => Data::Known(v),
Data::Unknown => Data::Unknown,
}
}
/// Unwraps the inner data type, panics otherwise.
///
/// # Panics
///
/// Panics if the data is [`Data::Unknown`].
pub fn unwrap(self) -> T {
match self {
Data::Known(v) => v,
Data::Unknown => panic!("cannot unwrap unknown data"),
}
}
/// Apply a function to the contained value in this [`Data`].
pub(crate) fn map<F, O>(self, f: F) -> Data<O>
where
F: FnOnce(T) -> O,
{
match self {
Self::Unknown => Data::Unknown,
Self::Known(val) => Data::Known(f(val)),
}
}
}
impl<T> Data<T> {
/// Generate a parser for this Data<T>, with a given parser to get `T`.
pub(crate) fn parser_inline<'src>(
num_slashes: usize,
parser: impl Parser<'src, &'src str, T, extra::Err<MetarError<'src>>>,
) -> impl Parser<'src, &'src str, Data<T>, extra::Err<MetarError<'src>>> {
let slashes = just("/").repeated().exactly(num_slashes);
choice((
slashes.map(|()| Data::Unknown),
parser.map(|v| Data::Known(v)),
))
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_data() {
assert_eq!(
Data::parser_inline(4, just("ABCD").map(|_| true))
.parse("ABCD")
.into_result()
.unwrap(),
Data::Known(true)
);
assert_eq!(
Data::parser_inline(4, just("ABCD").map(|_| true))
.parse("////")
.into_result()
.unwrap(),
Data::Unknown
);
}
}