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use crate::owned;
/// Tests if all elements of the iterator are equal to each other.
///
/// An empty iterator returns `true`.
///
/// `uniform()` is short-circuiting. It will stop processing as soon
/// as it finds two pairwise inequal elements.
fn uniform<I, E>(iter: I) -> bool
where
I: IntoIterator<Item = E>,
E: Eq,
{
let mut iter = iter.into_iter();
match iter.next() {
Some(first) => iter.all(|e| e == first),
None => true,
}
}
pub fn commute(first: &owned::Hunk, second: &owned::Hunk) -> Option<(owned::Hunk, owned::Hunk)> {
let (_, _, first_upper, first_lower) = first.anchors();
let (second_upper, second_lower, _, _) = second.anchors();
// represent hunks in content order rather than application order
let (first_above, above, below) = {
if first_lower <= second_upper {
(true, first, second)
} else if second_lower <= first_upper {
(false, second, first)
} else {
// if both hunks are exclusively adding or removing, and
// both hunks are composed entirely of the same line being
// repeated, then they commute no matter what their
// offsets are, because they can be interleaved in any
// order without changing the final result
if (first.added.lines.is_empty()
&& second.added.lines.is_empty()
&& uniform(first.removed.lines.iter().chain(&*second.removed.lines)))
|| (first.removed.lines.is_empty()
&& second.removed.lines.is_empty()
&& uniform(first.added.lines.iter().chain(&*second.added.lines)))
{
// TODO: removed/added start positions probably need to be
// tweaked here
return Some((second.clone(), first.clone()));
}
// these hunks overlap and cannot be interleaved, so they
// do not commute
return None;
}
};
let above = above.clone();
let mut below = below.clone();
let above_change_offset = (above.added.lines.len() as i64 - above.removed.lines.len() as i64)
* if first_above { -1 } else { 1 };
below.added.start = (below.added.start as i64 + above_change_offset) as usize;
below.removed.start = (below.removed.start as i64 + above_change_offset) as usize;
Some(if first_above {
(below, above)
} else {
(above, below)
})
}
pub fn commute_diff_before<'a, I>(after: &owned::Hunk, before: I) -> Option<owned::Hunk>
where
I: IntoIterator<Item = &'a owned::Hunk>,
<I as IntoIterator>::IntoIter: DoubleEndedIterator,
{
before
.into_iter()
// the patch's hunks must be iterated in reverse application
// order (last applied to first applied), which also happens
// to be reverse line order (bottom to top), which also
// happens to be reverse of the order they're stored
.rev()
.try_fold(after.clone(), |after, next| {
commute(next, &after).map(|(commuted_after, _)| commuted_after)
})
}
#[cfg(test)]
mod tests {
use super::*;
use std::rc::Rc;
#[test]
fn test_commute() {
// example init: <<EOF
// foo
// EOF
let hunk1 = owned::Hunk {
added: owned::Block {
start: 2,
lines: Rc::new(vec![b"bar\n".to_vec()]),
},
removed: owned::Block {
start: 1,
lines: Rc::new(vec![]),
},
};
// after hunk1: <<EOF
// foo
// bar
// EOF
let hunk2 = owned::Hunk {
added: owned::Block {
start: 1,
lines: Rc::new(vec![b"bar\n".to_vec()]),
},
removed: owned::Block {
start: 0,
lines: Rc::new(vec![]),
},
};
// after hunk2: <<EOF
// bar
// foo
// bar
// EOF
let (new1, new2) = commute(&hunk1, &hunk2).unwrap();
assert_eq!(new1.added.start, 1);
assert_eq!(new2.added.start, 3);
}
#[test]
fn test_commute_trivial_add() {
let mut line = ::std::iter::repeat(b"bar\n".to_vec());
let hunk1 = owned::Hunk {
added: owned::Block {
start: 1,
lines: Rc::new((&mut line).take(4).collect::<Vec<_>>()),
},
removed: owned::Block {
start: 0,
lines: Rc::new(vec![]),
},
};
let hunk2 = owned::Hunk {
added: owned::Block {
start: 1,
lines: Rc::new((&mut line).take(2).collect::<Vec<_>>()),
},
removed: owned::Block {
start: 0,
lines: Rc::new(vec![]),
},
};
let (new1, new2) = commute(&hunk1, &hunk2).unwrap();
assert_eq!(new1.added.lines.len(), 2);
assert_eq!(new2.added.lines.len(), 4);
}
#[test]
fn test_commute_trivial_remove() {
let mut line = ::std::iter::repeat(b"bar\n".to_vec());
let hunk1 = owned::Hunk {
added: owned::Block {
start: 1,
lines: Rc::new(vec![]),
},
removed: owned::Block {
start: 4,
lines: Rc::new((&mut line).take(4).collect::<Vec<_>>()),
},
};
let hunk2 = owned::Hunk {
added: owned::Block {
start: 1,
lines: Rc::new(vec![]),
},
removed: owned::Block {
start: 2,
lines: Rc::new((&mut line).take(2).collect::<Vec<_>>()),
},
};
let (new1, new2) = commute(&hunk1, &hunk2).unwrap();
assert_eq!(new1.removed.lines.len(), 2);
assert_eq!(new2.removed.lines.len(), 4);
}
#[test]
fn test_commute_patch() {
// example init: <<EOF
// foo
// foo
// EOF
let patch = vec![
owned::Hunk {
added: owned::Block {
start: 1,
lines: Rc::new(vec![b"bar\n".to_vec()]),
},
removed: owned::Block {
start: 0,
lines: Rc::new(vec![]),
},
},
owned::Hunk {
added: owned::Block {
start: 3,
lines: Rc::new(vec![b"bar\n".to_vec()]),
},
removed: owned::Block {
start: 1,
lines: Rc::new(vec![]),
},
},
];
// after patch: <<EOF
// bar
// foo
// bar
// foo
// EOF
let hunk = owned::Hunk {
added: owned::Block {
start: 5,
lines: Rc::new(vec![b"bar\n".to_vec()]),
},
removed: owned::Block {
start: 4,
lines: Rc::new(vec![]),
},
};
// after hunk: <<EOF
// bar
// foo
// bar
// foo
// bar
// EOF
let commuted = commute_diff_before(&hunk, &patch).unwrap();
assert_eq!(commuted.added.start, 3);
}
}