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use std::iter::Enumerate;
#[derive(Debug, Clone)]
pub struct EnsureIter<I, T, E, F, Factory>
where
I: Iterator<Item = Result<T, E>>,
F: Fn(&T) -> bool,
Factory: Fn(usize, T) -> E,
{
iter: Enumerate<I>,
validation: F,
factory: Factory,
}
impl<I, T, E, F, Factory> EnsureIter<I, T, E, F, Factory>
where
I: Iterator<Item = Result<T, E>>,
F: Fn(&T) -> bool,
Factory: Fn(usize, T) -> E,
{
pub(crate) fn new(iter: I, validation: F, factory: Factory) -> EnsureIter<I, T, E, F, Factory> {
EnsureIter {
iter: iter.enumerate(),
validation,
factory,
}
}
}
impl<I, T, E, F, Factory> Iterator for EnsureIter<I, T, E, F, Factory>
where
I: Iterator<Item = Result<T, E>>,
F: Fn(&T) -> bool,
Factory: Fn(usize, T) -> E,
{
type Item = Result<T, E>;
fn next(&mut self) -> Option<Self::Item> {
match self.iter.next() {
Some((i, Ok(val))) => match (self.validation)(&val) {
true => Some(Ok(val)),
false => Some(Err((self.factory)(i, val))),
},
Some((_, err)) => Some(err),
None => None,
}
}
}
pub trait Ensure<T, E, F, Factory>: Iterator<Item = Result<T, E>> + Sized
where
F: Fn(&T) -> bool,
Factory: Fn(usize, T) -> E,
{
/// Applies a boolean test too each element, and fails the
/// iteration if any element violates the constraint.
///
/// `ensure(validation, factory)` is the general validation tool, it takes
/// a boolean test as an argument and applies it to each of the
/// elements in the iteration. If the test returns `true`, the element
/// is wrapped in `Ok(element)`. Otherwise, `factory` gets called on it
/// and the index of the error.
///
/// Values already wrapped in `Result::Err` are ignored.
///
/// # Examples
///
/// Basic usage:
/// ```
/// use validiter::Ensure;
/// #[derive(Debug, PartialEq)]
/// struct Odd(usize, i32);
/// let mut iter = (0..=3).map(|v| Ok(v)).ensure(|i| i % 2 == 0, |i, v| Odd(i, v));
///
/// assert_eq!(iter.next(), Some(Ok(0)));
/// assert_eq!(iter.next(), Some(Err(Odd(1, 1))));
/// assert_eq!(iter.next(), Some(Ok(2)));
/// assert_eq!(iter.next(), Some(Err(Odd(3, 3))));
/// ```
///
/// You might want to chain `ensure` validations to create
/// a more complex test:
/// ```
/// # use validiter::Ensure;
/// # #[derive(Debug, PartialEq)]
/// enum IterError {
/// Odd,
/// NonPositive
/// }
///
/// let mut iter = (0..=3)
/// .map(|v| Ok(v))
/// .ensure(|i| i % 2 == 0, |_, _| IterError::Odd)
/// .ensure(|i| *i > 0, |_, _| IterError::NonPositive);
///
/// assert_eq!(iter.next(), Some(Err(IterError::NonPositive)));
/// assert_eq!(iter.next(), Some(Err(IterError::Odd)));
/// assert_eq!(iter.next(), Some(Ok(2)));
/// assert_eq!(iter.next(), Some(Err(IterError::Odd)));
/// ```
///
/// `ensure` ignores error elements:
/// ```
/// # use validiter::Ensure;
///
/// let mut iter = [Err(0)]
/// .into_iter()
/// .ensure(|i| *i == 0, |_, v| v);
///
/// assert_eq!(iter.next(), Some(Err(0)));
/// ```
///
/// [`Err(ValidErr::Invalid(element))`](crate::valid_result::ValidErr)
fn ensure(self, test: F, factory: Factory) -> EnsureIter<Self, T, E, F, Factory> {
EnsureIter::new(self, test, factory)
}
}
impl<I, T, E, F, Factory> Ensure<T, E, F, Factory> for I
where
I: Iterator<Item = Result<T, E>>,
F: Fn(&T) -> bool,
Factory: Fn(usize, T) -> E,
{
}
#[cfg(test)]
mod tests {
use super::Ensure;
#[derive(Debug, PartialEq)]
enum TestErr {
IsOdd(usize, i32),
Err1(usize, i32),
Err2(usize, i32),
}
#[test]
fn test_ensure() {
(0..10)
.map(|v| Ok(v))
.ensure(|i| i % 2 == 0, |err_index, i| TestErr::IsOdd(err_index, i))
.enumerate()
.for_each(|(i, res_i)| match res_i {
Ok(int) if i % 2 == 0 && i as i32 == int => {}
Err(TestErr::IsOdd(i, v)) if v % 2 == 1 && i as i32 == v => {}
_ => panic!("unexpected value in ensure adapter"),
})
}
#[test]
fn test_ensure_ignores_errors() {
let v = (0..=0)
.map(|v| Ok(v))
.ensure(|i| *i != 0, |err_index, v| TestErr::Err1(err_index, v))
.ensure(|i| *i != 0, |err_index, v| TestErr::Err2(err_index, v))
.next();
assert_eq!(v, Some(Err(TestErr::Err1(0, 0))))
}
}