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use git_object::bstr::BString;
use crate::{
transaction::{Change, LogChange, PreviousValue, RefEdit, RefLog, Target},
PartialNameRef,
};
/// An extension trait to perform commonly used operations on edits across different ref stores.
pub trait RefEditsExt<T>
where
T: std::borrow::Borrow<RefEdit> + std::borrow::BorrowMut<RefEdit>,
{
/// Return true if each ref `name` has exactly one `edit` across multiple ref edits
fn assure_one_name_has_one_edit(&self) -> Result<(), BString>;
/// Split all symbolic refs into updates for the symbolic ref as well as all their referents if the `deref` flag is enabled.
///
/// Note no action is performed if deref isn't specified.
fn extend_with_splits_of_symbolic_refs(
&mut self,
find: impl FnMut(&PartialNameRef) -> Option<Target>,
make_entry: impl FnMut(usize, RefEdit) -> T,
) -> Result<(), std::io::Error>;
/// All processing steps in one and in the correct order.
///
/// Users call this to assure derefs are honored and duplicate checks are done.
fn pre_process(
&mut self,
find: impl FnMut(&PartialNameRef) -> Option<Target>,
make_entry: impl FnMut(usize, RefEdit) -> T,
) -> Result<(), std::io::Error> {
self.extend_with_splits_of_symbolic_refs(find, make_entry)?;
self.assure_one_name_has_one_edit().map_err(|name| {
std::io::Error::new(
std::io::ErrorKind::AlreadyExists,
format!("A reference named '{name}' has multiple edits"),
)
})
}
}
impl<E> RefEditsExt<E> for Vec<E>
where
E: std::borrow::Borrow<RefEdit> + std::borrow::BorrowMut<RefEdit>,
{
fn assure_one_name_has_one_edit(&self) -> Result<(), BString> {
let mut names: Vec<_> = self.iter().map(|e| &e.borrow().name).collect();
names.sort();
match names.windows(2).find(|v| v[0] == v[1]) {
Some(name) => Err(name[0].as_bstr().to_owned()),
None => Ok(()),
}
}
fn extend_with_splits_of_symbolic_refs(
&mut self,
mut find: impl FnMut(&PartialNameRef) -> Option<Target>,
mut make_entry: impl FnMut(usize, RefEdit) -> E,
) -> Result<(), std::io::Error> {
let mut new_edits = Vec::new();
let mut first = 0;
let mut round = 1;
loop {
for (eid, edit) in self[first..].iter_mut().enumerate().map(|(eid, v)| (eid + first, v)) {
let edit = edit.borrow_mut();
if !edit.deref {
continue;
};
// we can't tell what happened and we are here because it's a non-existing ref or an invalid one.
// In any case, we don't want the following algorithms to try dereffing it and assume they deal with
// broken refs gracefully.
edit.deref = false;
if let Some(Target::Symbolic(referent)) = find(edit.name.as_ref().as_partial_name()) {
new_edits.push(make_entry(
eid,
match &mut edit.change {
Change::Delete {
expected: previous,
log: mode,
} => {
let current_mode = *mode;
*mode = RefLog::Only;
RefEdit {
change: Change::Delete {
expected: previous.clone(),
log: current_mode,
},
name: referent,
deref: true,
}
}
Change::Update { log, expected, new } => {
let current = std::mem::replace(
log,
LogChange {
message: log.message.clone(),
mode: RefLog::Only,
force_create_reflog: log.force_create_reflog,
},
);
let next = std::mem::replace(expected, PreviousValue::Any);
RefEdit {
change: Change::Update {
expected: next,
new: new.clone(),
log: current,
},
name: referent,
deref: true,
}
}
},
));
}
}
if new_edits.is_empty() {
break Ok(());
}
if round == 5 {
break Err(std::io::Error::new(
std::io::ErrorKind::WouldBlock,
format!("Could not follow all splits after {round} rounds, assuming reference cycle"),
));
}
round += 1;
first = self.len();
self.append(&mut new_edits);
}
}
}