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use std::collections::{BTreeMap, HashMap, HashSet};
use log::trace;
use super::types::ConflictMap;
use crate::core::resolver::Context;
use crate::core::{Dependency, PackageId};
/// This is a trie for storing a large number of sets designed to
/// efficiently see if any of the stored sets are a subset of a search set.
enum ConflictStoreTrie {
/// One of the stored sets.
Leaf(ConflictMap),
/// A map from an element to a subtrie where
/// all the sets in the subtrie contains that element.
Node(BTreeMap<PackageId, ConflictStoreTrie>),
}
impl ConflictStoreTrie {
/// Finds any known set of conflicts, if any,
/// where all elements return some from `is_active` and contain `PackageId` specified.
/// If more then one are activated, then it will return
/// one that will allow for the most jump-back.
fn find(
&self,
is_active: &impl Fn(PackageId) -> Option<usize>,
must_contain: Option<PackageId>,
mut max_age: usize,
) -> Option<(&ConflictMap, usize)> {
match self {
ConflictStoreTrie::Leaf(c) => {
if must_contain.is_none() {
Some((c, 0))
} else {
// We did not find `must_contain`, so we need to keep looking.
None
}
}
ConflictStoreTrie::Node(m) => {
let mut out = None;
for (&pid, store) in must_contain
.map(|f| m.range(..=f))
.unwrap_or_else(|| m.range(..))
{
// If the key is active, then we need to check all of the corresponding subtrie.
if let Some(age_this) = is_active(pid) {
if age_this >= max_age && must_contain != Some(pid) {
// not worth looking at, it is to old.
continue;
}
if let Some((o, age_o)) =
store.find(is_active, must_contain.filter(|&f| f != pid), max_age)
{
let age = if must_contain == Some(pid) {
// all the results will include `must_contain`
// so the age of must_contain is not relevant to find the best result.
age_o
} else {
std::cmp::max(age_this, age_o)
};
if max_age > age {
// we found one that can jump-back further so replace the out.
out = Some((o, age));
// and don't look at anything older
max_age = age
}
}
}
// Else, if it is not active then there is no way any of the corresponding
// subtrie will be conflicting.
}
out
}
}
}
fn insert(&mut self, mut iter: impl Iterator<Item = PackageId>, con: ConflictMap) {
if let Some(pid) = iter.next() {
if let ConflictStoreTrie::Node(p) = self {
p.entry(pid)
.or_insert_with(|| ConflictStoreTrie::Node(BTreeMap::new()))
.insert(iter, con);
}
// Else, we already have a subset of this in the `ConflictStore`.
} else {
// We are at the end of the set we are adding, there are three cases for what to do
// next:
// 1. `self` is a empty dummy Node inserted by `or_insert_with`
// in witch case we should replace it with `Leaf(con)`.
// 2. `self` is a `Node` because we previously inserted a superset of
// the thing we are working on (I don't know if this happens in practice)
// but the subset that we are working on will
// always match any time the larger set would have
// in witch case we can replace it with `Leaf(con)`.
// 3. `self` is a `Leaf` that is in the same spot in the structure as
// the thing we are working on. So it is equivalent.
// We can replace it with `Leaf(con)`.
if cfg!(debug_assertions) {
if let ConflictStoreTrie::Leaf(c) = self {
let a: Vec<_> = con.keys().collect();
let b: Vec<_> = c.keys().collect();
assert_eq!(a, b);
}
}
*self = ConflictStoreTrie::Leaf(con)
}
}
}
pub(super) struct ConflictCache {
// `con_from_dep` is a cache of the reasons for each time we
// backtrack. For example after several backtracks we may have:
//
// con_from_dep[`foo = "^1.0.2"`] = map!{
// `foo=1.0.1`: map!{`foo=1.0.1`: Semver},
// `foo=1.0.0`: map!{`foo=1.0.0`: Semver},
// };
//
// This can be read as "we cannot find a candidate for dep `foo = "^1.0.2"`
// if either `foo=1.0.1` OR `foo=1.0.0` are activated".
//
// Another example after several backtracks we may have:
//
// con_from_dep[`foo = ">=0.8.2, <=0.9.3"`] = map!{
// `foo=0.8.1`: map!{
// `foo=0.9.4`: map!{`foo=0.8.1`: Semver, `foo=0.9.4`: Semver},
// }
// };
//
// This can be read as "we cannot find a candidate for dep `foo = ">=0.8.2,
// <=0.9.3"` if both `foo=0.8.1` AND `foo=0.9.4` are activated".
//
// This is used to make sure we don't queue work we know will fail. See the
// discussion in https://github.com/rust-lang/cargo/pull/5168 for why this
// is so important. The nested HashMaps act as a kind of btree, that lets us
// look up which entries are still active without
// linearly scanning through the full list.
//
// Also, as a final note, this map is **not** ever removed from. This remains
// as a global cache which we never delete from. Any entry in this map is
// unconditionally true regardless of our resolution history of how we got
// here.
con_from_dep: HashMap<Dependency, ConflictStoreTrie>,
// `dep_from_pid` is an inverse-index of `con_from_dep`.
// For every `PackageId` this lists the `Dependency`s that mention it in `dep_from_pid`.
dep_from_pid: HashMap<PackageId, HashSet<Dependency>>,
}
impl ConflictCache {
pub fn new() -> ConflictCache {
ConflictCache {
con_from_dep: HashMap::new(),
dep_from_pid: HashMap::new(),
}
}
pub fn find(
&self,
dep: &Dependency,
is_active: &impl Fn(PackageId) -> Option<usize>,
must_contain: Option<PackageId>,
max_age: usize,
) -> Option<&ConflictMap> {
self.con_from_dep
.get(dep)?
.find(is_active, must_contain, max_age)
.map(|(c, _)| c)
}
/// Finds any known set of conflicts, if any,
/// which are activated in `cx` and contain `PackageId` specified.
/// If more then one are activated, then it will return
/// one that will allow for the most jump-back.
pub fn find_conflicting(
&self,
cx: &Context,
dep: &Dependency,
must_contain: Option<PackageId>,
) -> Option<&ConflictMap> {
let out = self.find(dep, &|id| cx.is_active(id), must_contain, std::usize::MAX);
if cfg!(debug_assertions) {
if let Some(c) = &out {
assert!(cx.is_conflicting(None, c).is_some());
if let Some(f) = must_contain {
assert!(c.contains_key(&f));
}
}
}
out
}
pub fn conflicting(&self, cx: &Context, dep: &Dependency) -> Option<&ConflictMap> {
self.find_conflicting(cx, dep, None)
}
/// Adds to the cache a conflict of the form:
/// `dep` is known to be unresolvable if
/// all the `PackageId` entries are activated.
pub fn insert(&mut self, dep: &Dependency, con: &ConflictMap) {
if con.values().any(|c| c.is_public_dependency()) {
// TODO: needs more info for back jumping
// for now refuse to cache it.
return;
}
self.con_from_dep
.entry(dep.clone())
.or_insert_with(|| ConflictStoreTrie::Node(BTreeMap::new()))
.insert(con.keys().cloned(), con.clone());
trace!(
"{} = \"{}\" adding a skip {:?}",
dep.package_name(),
dep.version_req(),
con
);
for c in con.keys() {
self.dep_from_pid
.entry(c.clone())
.or_insert_with(HashSet::new)
.insert(dep.clone());
}
}
pub fn dependencies_conflicting_with(&self, pid: PackageId) -> Option<&HashSet<Dependency>> {
self.dep_from_pid.get(&pid)
}
}