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// Copyright 2023 The Jujutsu Authors//// Licensed under the Apache License, Version 2.0 (the "License");// you may not use this file except in compliance with the License.// You may obtain a copy of the License at//// https://www.apache.org/licenses/LICENSE-2.0//// Unless required by applicable law or agreed to in writing, software// distributed under the License is distributed on an "AS IS" BASIS,// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.// See the License for the specific language governing permissions and// limitations under the License. use std::any::Any;use std::collections::HashMap;use std::fmt::{Debug, Error, Formatter};use std::io::{Cursor, Read};use std::path::{Path, PathBuf};use std::sync::{Arc, Mutex, MutexGuard, OnceLock};use std::time::SystemTime; use async_trait::async_trait;use jj_lib::backend::{    make_root_commit, Backend, BackendError, BackendResult, ChangeId, Commit, CommitId, Conflict,    ConflictId, FileId, SecureSig, SigningFn, SymlinkId, Tree, TreeId,};use jj_lib::index::Index;use jj_lib::object_id::ObjectId;use jj_lib::repo_path::{RepoPath, RepoPathBuf}; const HASH_LENGTH: usize = 10;const CHANGE_ID_LENGTH: usize = 16; static BACKEND_DATA: OnceLock<Mutex<HashMap<PathBuf, Arc<Mutex<TestBackendData>>>>> =    OnceLock::new(); fn backend_data() -> &'static Mutex<HashMap<PathBuf, Arc<Mutex<TestBackendData>>>> {    BACKEND_DATA.get_or_init(|| Mutex::new(HashMap::new()))} #[derive(Default)]pub struct TestBackendData {    commits: HashMap<CommitId, Commit>,    trees: HashMap<RepoPathBuf, HashMap<TreeId, Tree>>,    files: HashMap<RepoPathBuf, HashMap<FileId, Vec<u8>>>,    symlinks: HashMap<RepoPathBuf, HashMap<SymlinkId, String>>,    conflicts: HashMap<RepoPathBuf, HashMap<ConflictId, Conflict>>,} fn get_hash(content: &(impl jj_lib::content_hash::ContentHash + ?Sized)) -> Vec<u8> {    jj_lib::content_hash::blake2b_hash(content).as_slice()[..HASH_LENGTH].to_vec()} /// A commit backend for use in tests. It's meant to be strict, in order to/// catch bugs where we make the wrong assumptions. For example, unlike both/// `GitBackend` and `LocalBackend`, this backend doesn't share objects written/// to different paths (writing a file with contents X to path A will not make/// it possible to read that contents from path B given the same `FileId`).pub struct TestBackend {    root_commit_id: CommitId,    root_change_id: ChangeId,    empty_tree_id: TreeId,    data: Arc<Mutex<TestBackendData>>,} impl TestBackend {    pub fn init(store_path: &Path) -> Self {        let root_commit_id = CommitId::from_bytes(&[0; HASH_LENGTH]);        let root_change_id = ChangeId::from_bytes(&[0; CHANGE_ID_LENGTH]);        let empty_tree_id = TreeId::new(get_hash(&Tree::default()));        let data = Arc::new(Mutex::new(TestBackendData::default()));        backend_data()            .lock()            .unwrap()            .insert(store_path.to_path_buf(), data.clone());        TestBackend {            root_commit_id,            root_change_id,            empty_tree_id,            data,        }    }     pub fn load(store_path: &Path) -> Self {        let data = backend_data()            .lock()            .unwrap()            .get(store_path)            .unwrap()            .clone();        let root_commit_id = CommitId::from_bytes(&[0; HASH_LENGTH]);        let root_change_id = ChangeId::from_bytes(&[0; CHANGE_ID_LENGTH]);        let empty_tree_id = TreeId::new(get_hash(&Tree::default()));        TestBackend {            root_commit_id,            root_change_id,            empty_tree_id,            data,        }    }     fn locked_data(&self) -> MutexGuard<'_, TestBackendData> {        self.data.lock().unwrap()    }     pub fn remove_commit_unchecked(&self, id: &CommitId) {        self.locked_data().commits.remove(id);    }} impl Debug for TestBackend {    fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error> {        f.debug_struct("TestBackend").finish_non_exhaustive()    }} #[async_trait]impl Backend for TestBackend {    fn as_any(&self) -> &dyn Any {        self    }     fn name(&self) -> &str {        "test"    }     fn commit_id_length(&self) -> usize {        HASH_LENGTH    }     fn change_id_length(&self) -> usize {        CHANGE_ID_LENGTH    }     fn root_commit_id(&self) -> &CommitId {        &self.root_commit_id    }     fn root_change_id(&self) -> &ChangeId {        &self.root_change_id    }     fn empty_tree_id(&self) -> &TreeId {        &self.empty_tree_id    }     fn concurrency(&self) -> usize {        // Not optimal, just for testing the async code more        10    }     async fn read_file(&self, path: &RepoPath, id: &FileId) -> BackendResult<Box<dyn Read>> {        match self            .locked_data()            .files            .get(path)            .and_then(|items| items.get(id))            .cloned()        {            None => Err(BackendError::ObjectNotFound {                object_type: "file".to_string(),                hash: id.hex(),                source: format!("at path {path:?}").into(),            }),            Some(contents) => Ok(Box::new(Cursor::new(contents))),        }    }     fn write_file(&self, path: &RepoPath, contents: &mut dyn Read) -> BackendResult<FileId> {        let mut bytes = Vec::new();        contents.read_to_end(&mut bytes).unwrap();        let id = FileId::new(get_hash(&bytes));        self.locked_data()            .files            .entry(path.to_owned())            .or_default()            .insert(id.clone(), bytes);        Ok(id)    }     async fn read_symlink(&self, path: &RepoPath, id: &SymlinkId) -> Result<String, BackendError> {        match self            .locked_data()            .symlinks            .get(path)            .and_then(|items| items.get(id))            .cloned()        {            None => Err(BackendError::ObjectNotFound {                object_type: "symlink".to_string(),                hash: id.hex(),                source: format!("at path {path:?}").into(),            }),            Some(target) => Ok(target),        }    }     fn write_symlink(&self, path: &RepoPath, target: &str) -> Result<SymlinkId, BackendError> {        let id = SymlinkId::new(get_hash(target.as_bytes()));        self.locked_data()            .symlinks            .entry(path.to_owned())            .or_default()            .insert(id.clone(), target.to_string());        Ok(id)    }     async fn read_tree(&self, path: &RepoPath, id: &TreeId) -> BackendResult<Tree> {        if id == &self.empty_tree_id {            return Ok(Tree::default());        }        match self            .locked_data()            .trees            .get(path)            .and_then(|items| items.get(id))            .cloned()        {            None => Err(BackendError::ObjectNotFound {                object_type: "tree".to_string(),                hash: id.hex(),                source: format!("at path {path:?}").into(),            }),            Some(tree) => Ok(tree),        }    }     fn write_tree(&self, path: &RepoPath, contents: &Tree) -> BackendResult<TreeId> {        let id = TreeId::new(get_hash(contents));        self.locked_data()            .trees            .entry(path.to_owned())            .or_default()            .insert(id.clone(), contents.clone());        Ok(id)    }     fn read_conflict(&self, path: &RepoPath, id: &ConflictId) -> BackendResult<Conflict> {        match self            .locked_data()            .conflicts            .get(path)            .and_then(|items| items.get(id))            .cloned()        {            None => Err(BackendError::ObjectNotFound {                object_type: "conflict".to_string(),                hash: id.hex(),                source: format!("at path {path:?}").into(),            }),            Some(conflict) => Ok(conflict),        }    }     fn write_conflict(&self, path: &RepoPath, contents: &Conflict) -> BackendResult<ConflictId> {        let id = ConflictId::new(get_hash(contents));        self.locked_data()            .conflicts            .entry(path.to_owned())            .or_default()            .insert(id.clone(), contents.clone());        Ok(id)    }     async fn read_commit(&self, id: &CommitId) -> BackendResult<Commit> {        if id == &self.root_commit_id {            return Ok(make_root_commit(                self.root_change_id.clone(),                self.empty_tree_id.clone(),            ));        }        match self.locked_data().commits.get(id).cloned() {            None => Err(BackendError::ObjectNotFound {                object_type: "commit".to_string(),                hash: id.hex(),                source: "".into(),            }),            Some(commit) => Ok(commit),        }    }     fn write_commit(        &self,        mut contents: Commit,        mut sign_with: Option<&mut SigningFn>,    ) -> BackendResult<(CommitId, Commit)> {        assert!(contents.secure_sig.is_none(), "commit.secure_sig was set");         if let Some(sign) = &mut sign_with {            let data = format!("{contents:?}").into_bytes();            let sig = sign(&data).map_err(|err| BackendError::Other(Box::new(err)))?;            contents.secure_sig = Some(SecureSig { data, sig });        }         let id = CommitId::new(get_hash(&contents));        self.locked_data()            .commits            .insert(id.clone(), contents.clone());        Ok((id, contents))    }     fn gc(&self, _index: &dyn Index, _keep_newer: SystemTime) -> BackendResult<()> {        Ok(())    }}