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//
// imag - the personal information management suite for the commandline
// Copyright (C) 2015-2020 the imag contributors
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; version
// 2.1 of the License.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
//
use failure::Error;
/// An iterator that unwraps the `Ok` items of `iter`, while passing the `Err` items to its
/// closure `f`.
///
/// This `struct` is created by the `unwrap_with()` method on `TraceIterator`. See its
/// documentation for more information.
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
#[derive(Clone)]
pub struct UnwrapWith<I, F>{
iter: I,
f: F
}
impl<I, F, T> Iterator for UnwrapWith<I, F>
where
I: Iterator<Item = Result<T, Error>>,
F: FnMut(Error)
{
type Item = T;
#[inline]
fn next(&mut self) -> Option<Self::Item> {
loop {
match self.iter.next() {
Some(Err(e)) => { (self.f)(e); },
Some(Ok(item)) => return Some(item),
None => return None,
}
}
}
}
/// Iterator helper for Unwrap with exiting on error
pub struct UnwrapExit<I, T>(I)
where I: Iterator<Item = Result<T, Error>>;
impl<I, T> Iterator for UnwrapExit<I, T>
where I: Iterator<Item = Result<T, Error>>,
{
type Item = T;
fn next(&mut self) -> Option<Self::Item> {
use crate::trace::MapErrTrace;
self.0.next().map(|e| e.map_err_trace_exit_unwrap())
}
}
impl<I, T> DoubleEndedIterator for UnwrapExit<I, T>
where I: DoubleEndedIterator<Item = Result<T, Error>>,
{
fn next_back(&mut self) -> Option<Self::Item> {
use crate::trace::MapErrTrace;
self.0.next_back().map(|e| e.map_err_trace_exit_unwrap())
}
}
/// This trait provides methods that make it easier to work with iterators that yield a `Result`.
pub trait TraceIterator<T> : Iterator<Item = Result<T, Error>> + Sized {
/// Creates an iterator that yields the item in each `Ok` item, while filtering out the
/// `Err`
/// items. Each filtered `Err` will be trace-logged with [`::trace::trace_error`].
///
/// As with all iterators, the processing is lazy. If you do not use the result of this method,
/// nothing will be passed to `::trace::trace_error`, no matter how many `Err` items might
/// be present.
#[inline]
fn trace_unwrap(self) -> UnwrapWith<Self, fn(Error)> {
#[inline]
fn trace_error(err: Error) {
err.iter_chain().for_each(|cause| {
eprintln!("{}", cause);
});
}
self.unwrap_with(trace_error)
}
/// Creates an iterator that yields the item in each `Ok` item.
///
/// The first `Err(_)` element is traced using `::trace::trace_error_exit`.
///
/// As with all iterators, the processing is lazy. If you do not use the result of this method,
/// nothing will be passed to `::trace::trace_error_exit`, no matter how many `Err` items might
/// be present.
#[inline]
fn trace_unwrap_exit(self) -> UnwrapExit<Self, T> {
UnwrapExit(self)
}
/// Takes a closure and creates an iterator that will yield the items inside all `Ok` items
/// yielded by the original iterator. All `Err` items will be filtered out, and the contents
/// of each `Err` will be passed to the closure.
///
/// As with all iterators, the processing is lazy. The result of this method must be evaluated
/// for the closure to be called.
#[inline]
fn unwrap_with<F>(self, f: F) -> UnwrapWith<Self, F>
where F: FnMut(Error)
{
UnwrapWith { iter: self, f }
}
}
impl<I, T> TraceIterator<T> for I where
I: Iterator<Item = Result<T, Error>>
{}
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