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use std::{collections::HashSet, ops::Deref};
use crate::{
store::{load_index, Handle},
Find,
};
///
pub mod lookup {
use crate::loose;
/// Returned by [`Handle::lookup_prefix()`][crate::store::Handle::lookup_prefix()]
#[derive(thiserror::Error, Debug)]
#[allow(missing_docs)]
pub enum Error {
#[error("An error occurred looking up a prefix which requires iteration")]
LooseWalkDir(#[from] loose::iter::Error),
#[error(transparent)]
LoadIndex(#[from] crate::store::load_index::Error),
}
/// A way to indicate if a lookup, despite successful, was ambiguous or yielded exactly
/// one result in the particular index.
pub type Outcome = Result<git_hash::ObjectId, ()>;
}
///
pub mod disambiguate {
/// A potentially ambiguous prefix for use with `Handle::disambiguate_prefix()`.
#[derive(Debug, Copy, Clone)]
pub struct Candidate {
id: git_hash::ObjectId,
hex_len: usize,
}
impl Candidate {
/// Create a new potentially ambiguous prefix from an `id` and the desired minimal `hex_len`.
///
/// It is considered ambiguous until it's disambiguated by validating that there is only a single object
/// matching this prefix.
pub fn new(id: impl Into<git_hash::ObjectId>, hex_len: usize) -> Result<Self, git_hash::prefix::Error> {
let id = id.into();
git_hash::Prefix::new(id, hex_len)?;
Ok(Candidate { id, hex_len })
}
/// Transform ourselves into a `Prefix` with our current hex lengths.
pub fn to_prefix(&self) -> git_hash::Prefix {
git_hash::Prefix::new(self.id, self.hex_len).expect("our hex-len to always be in bounds")
}
pub(crate) fn inc_hex_len(&mut self) {
self.hex_len += 1;
assert!(self.hex_len <= self.id.kind().len_in_hex());
}
pub(crate) fn id(&self) -> &git_hash::oid {
&self.id
}
pub(crate) fn hex_len(&self) -> usize {
self.hex_len
}
}
/// Returned by [`Handle::disambiguate_prefix()`][crate::store::Handle::disambiguate_prefix()]
#[derive(thiserror::Error, Debug)]
#[allow(missing_docs)]
pub enum Error {
#[error("An error occurred while trying to determine if a full hash contained in the object database")]
Contains(#[from] crate::store::find::Error),
#[error(transparent)]
Lookup(#[from] super::lookup::Error),
}
}
impl<S> Handle<S>
where
S: Deref<Target = super::Store> + Clone,
{
/// Return the exact number of packed objects after loading all currently available indices
/// as last seen on disk.
pub fn packed_object_count(&self) -> Result<u64, load_index::Error> {
let mut count = self.packed_object_count.borrow_mut();
match *count {
Some(count) => Ok(count),
None => {
let mut snapshot = self.snapshot.borrow_mut();
*snapshot = self.store.load_all_indices()?;
let mut obj_count = 0;
for index in &snapshot.indices {
obj_count += index.num_objects() as u64;
}
*count = Some(obj_count);
Ok(obj_count)
}
}
}
/// Given a prefix `candidate` with an object id and an initial `hex_len`, check if it only matches a single
/// object within the entire object database and increment its `hex_len` by one until it is unambiguous.
/// Return `Ok(None)` if no object with that prefix exists.
pub fn disambiguate_prefix(
&self,
mut candidate: disambiguate::Candidate,
) -> Result<Option<git_hash::Prefix>, disambiguate::Error> {
let max_hex_len = candidate.id().kind().len_in_hex();
if candidate.hex_len() == max_hex_len {
return Ok(self.contains(candidate.id()).then(|| candidate.to_prefix()));
}
while candidate.hex_len() != max_hex_len {
let res = self.lookup_prefix(candidate.to_prefix(), None)?;
match res {
Some(Ok(_id)) => return Ok(Some(candidate.to_prefix())),
Some(Err(())) => {
candidate.inc_hex_len();
continue;
}
None => return Ok(None),
}
}
Ok(Some(candidate.to_prefix()))
}
/// Find the only object matching `prefix` and return it as `Ok(Some(Ok(<ObjectId>)))`, or return `Ok(Some(Err(()))`
/// if multiple different objects with the same prefix were found.
///
/// Return `Ok(None)` if no object matched the `prefix`.
///
/// Pass `candidates` to obtain the set of all object ids matching `prefix`, with the same return value as
/// one would have received if it remained `None`.
///
/// ### Performance Note
///
/// - Unless the handles refresh mode is set to `Never`, each lookup will trigger a refresh of the object databases files
/// on disk if the prefix doesn't lead to ambiguous results.
/// - Since all objects need to be examined to assure non-ambiguous return values, after calling this method all indices will
/// be loaded.
/// - If `candidates` is `Some(…)`, the traversal will continue to obtain all candidates, which takes more time
/// as there is no early abort.
pub fn lookup_prefix(
&self,
prefix: git_hash::Prefix,
mut candidates: Option<&mut HashSet<git_hash::ObjectId>>,
) -> Result<Option<lookup::Outcome>, lookup::Error> {
let mut candidate: Option<git_hash::ObjectId> = None;
loop {
let snapshot = self.snapshot.borrow();
for index in snapshot.indices.iter() {
#[allow(clippy::needless_option_as_deref)] // needed as it's the equivalent of a reborrow.
let lookup_result = index.lookup_prefix(prefix, candidates.as_deref_mut());
if candidates.is_none() && !check_candidate(lookup_result, &mut candidate) {
return Ok(Some(Err(())));
}
}
for lodb in snapshot.loose_dbs.iter() {
#[allow(clippy::needless_option_as_deref)] // needed as it's the equivalent of a reborrow.
let lookup_result = lodb.lookup_prefix(prefix, candidates.as_deref_mut())?;
if candidates.is_none() && !check_candidate(lookup_result, &mut candidate) {
return Ok(Some(Err(())));
}
}
match self.store.load_one_index(self.refresh, snapshot.marker)? {
Some(new_snapshot) => {
drop(snapshot);
*self.snapshot.borrow_mut() = new_snapshot;
}
None => {
return match &candidates {
Some(candidates) => match candidates.len() {
0 => Ok(None),
1 => Ok(candidates.iter().cloned().next().map(Ok)),
_ => Ok(Some(Err(()))),
},
None => Ok(candidate.map(Ok)),
};
}
}
}
fn check_candidate(lookup_result: Option<lookup::Outcome>, candidate: &mut Option<git_hash::ObjectId>) -> bool {
match (lookup_result, &*candidate) {
(Some(Ok(oid)), Some(candidate)) if *candidate != oid => false,
(Some(Ok(_)), Some(_)) | (None, None) | (None, Some(_)) => true,
(Some(Err(())), _) => false,
(Some(Ok(oid)), None) => {
*candidate = Some(oid);
true
}
}
}
}
}