// Copyright 2020 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. #![allow(missing_docs)] use std::any::Any;use std::collections::BTreeMap;use std::fmt::Debug;use std::io::Read;use std::time::SystemTime; use async_trait::async_trait;use futures::stream::BoxStream;use thiserror::Error; use crate::content_hash::ContentHash;use crate::hex_util;use crate::index::Index;use crate::merge::Merge;use crate::object_id::id_type;use crate::object_id::ObjectId as _;use crate::repo_path::RepoPath;use crate::repo_path::RepoPathBuf;use crate::repo_path::RepoPathComponent;use crate::repo_path::RepoPathComponentBuf;use crate::signing::SignResult; id_type!(    /// Identifier for a [`Commit`] based on its content. When a commit is    /// rewritten, its `CommitId` changes.    pub CommitId { hex() });id_type!(    /// Stable identifier for a [`Commit`]. Unlike the `CommitId`, the `ChangeId`    /// follows the commit and is not updated when the commit is rewritten.    pub ChangeId { reverse_hex() });id_type!(pub TreeId { hex() });id_type!(pub FileId { hex() });id_type!(pub SymlinkId { hex() });id_type!(pub ConflictId { hex() }); impl ChangeId {    /// Returns the hex string representation of this ID, which uses `z-k`    /// "digits" instead of `0-9a-f`.    pub fn reverse_hex(&self) -> String {        hex_util::encode_reverse_hex(&self.0)    }} #[derive(ContentHash, Debug, PartialEq, Eq, Clone, Copy, PartialOrd, Ord)]pub struct MillisSinceEpoch(pub i64); #[derive(ContentHash, Debug, PartialEq, Eq, Clone, Copy, PartialOrd, Ord)]pub struct Timestamp {    pub timestamp: MillisSinceEpoch,    // time zone offset in minutes    pub tz_offset: i32,} impl Timestamp {    pub fn now() -> Self {        Self::from_datetime(chrono::offset::Local::now())    }     pub fn from_datetime<Tz: chrono::TimeZone<Offset = chrono::offset::FixedOffset>>(        datetime: chrono::DateTime<Tz>,    ) -> Self {        Self {            timestamp: MillisSinceEpoch(datetime.timestamp_millis()),            tz_offset: datetime.offset().local_minus_utc() / 60,        }    }} /// Represents a [`Commit`] signature.#[derive(ContentHash, Debug, PartialEq, Eq, Clone)]pub struct Signature {    pub name: String,    pub email: String,    pub timestamp: Timestamp,} /// Represents a cryptographically signed [`Commit`] signature.#[derive(ContentHash, Debug, PartialEq, Eq, Clone)]pub struct SecureSig {    pub data: Vec<u8>,    pub sig: Vec<u8>,} pub type SigningFn<'a> = dyn FnMut(&[u8]) -> SignResult<Vec<u8>> + Send + 'a; /// Identifies a single legacy tree, which may have path-level conflicts, or a/// merge of multiple trees, where the individual trees do not have conflicts.// TODO(#1624): Delete this type at some point in the future, when we decide to drop// support for conflicts in older repos, or maybe after we have provided an upgrade// mechanism.#[derive(ContentHash, Debug, Clone)]pub enum MergedTreeId {    /// The tree id of a legacy tree    Legacy(TreeId),    /// The tree id(s) of a merge tree    Merge(Merge<TreeId>),} impl PartialEq for MergedTreeId {    /// Overridden to make conflict-free trees be considered equal even if their    /// `MergedTreeId` variant is different.    fn eq(&self, other: &Self) -> bool {        self.to_merge() == other.to_merge()    }} impl Eq for MergedTreeId {} impl MergedTreeId {    /// Create a resolved `MergedTreeId` from a single regular tree.    pub fn resolved(tree_id: TreeId) -> Self {        MergedTreeId::Merge(Merge::resolved(tree_id))    }     /// Return this id as `Merge<TreeId>`    pub fn to_merge(&self) -> Merge<TreeId> {        match self {            MergedTreeId::Legacy(tree_id) => Merge::resolved(tree_id.clone()),            MergedTreeId::Merge(tree_ids) => tree_ids.clone(),        }    }} #[derive(ContentHash, Debug, PartialEq, Eq, Clone)]pub struct Commit {    pub parents: Vec<CommitId>,    pub predecessors: Vec<CommitId>,    pub root_tree: MergedTreeId,    pub change_id: ChangeId,    pub description: String,    pub author: Signature,    pub committer: Signature,    pub secure_sig: Option<SecureSig>,} #[derive(ContentHash, Debug, PartialEq, Eq, Clone)]pub struct ConflictTerm {    pub value: TreeValue,} #[derive(ContentHash, Debug, PartialEq, Eq, Clone)]pub struct Conflict {    // A conflict is represented by a list of positive and negative states that need to be applied.    // In a simple 3-way merge of B and C with merge base A, the conflict will be { add: [B, C],    // remove: [A] }. Also note that a conflict of the form { add: [A], remove: [] } is the    // same as non-conflict A.    pub removes: Vec<ConflictTerm>,    pub adds: Vec<ConflictTerm>,} /// An individual copy event, from file A -> B.#[derive(Debug, PartialEq, Eq, Clone)]pub struct CopyRecord {    /// The destination of the copy, B.    pub target: RepoPathBuf,    /// The CommitId where the copy took place.    pub target_commit: CommitId,    /// The source path a target was copied from.    ///    /// It is not required that the source path is different than the target    /// path. A custom backend may choose to represent 'rollbacks' as copies    /// from a file unto itself, from a specific prior commit.    pub source: RepoPathBuf,    pub source_file: FileId,    /// The source commit the target was copied from. Backends may use this    /// field to implement 'integration' logic, where a source may be    /// periodically merged into a target, similar to a branch, but the    /// branching occurs at the file level rather than the repository level. It    /// also follows naturally that any copy source targeted to a specific    /// commit should avoid copy propagation on rebasing, which is desirable    /// for 'fork' style copies.    ///    /// It is required that the commit id is an ancestor of the commit with    /// which this copy source is associated.    pub source_commit: CommitId,} /// Error that may occur during backend initialization.#[derive(Debug, Error)]#[error(transparent)]pub struct BackendInitError(pub Box<dyn std::error::Error + Send + Sync>); /// Error that may occur during backend loading.#[derive(Debug, Error)]#[error(transparent)]pub struct BackendLoadError(pub Box<dyn std::error::Error + Send + Sync>); /// Commit-backend error that may occur after the backend is loaded.#[derive(Debug, Error)]pub enum BackendError {    #[error(        "Invalid hash length for object of type {object_type} (expected {expected} bytes, got \         {actual} bytes): {hash}"    )]    InvalidHashLength {        expected: usize,        actual: usize,        object_type: String,        hash: String,    },    #[error("Invalid UTF-8 for object {hash} of type {object_type}")]    InvalidUtf8 {        object_type: String,        hash: String,        source: std::str::Utf8Error,    },    #[error("Object {hash} of type {object_type} not found")]    ObjectNotFound {        object_type: String,        hash: String,        source: Box<dyn std::error::Error + Send + Sync>,    },    #[error("Error when reading object {hash} of type {object_type}")]    ReadObject {        object_type: String,        hash: String,        source: Box<dyn std::error::Error + Send + Sync>,    },    #[error("Access denied to read object {hash} of type {object_type}")]    ReadAccessDenied {        object_type: String,        hash: String,        source: Box<dyn std::error::Error + Send + Sync>,    },    #[error(        "Error when reading file content for file {path} with id {id}",        path = path.as_internal_file_string()    )]    ReadFile {        path: RepoPathBuf,        id: FileId,        source: Box<dyn std::error::Error + Send + Sync>,    },    #[error("Could not write object of type {object_type}")]    WriteObject {        object_type: &'static str,        source: Box<dyn std::error::Error + Send + Sync>,    },    #[error(transparent)]    Other(Box<dyn std::error::Error + Send + Sync>),    /// A valid operation attempted, but failed because it isn't supported by    /// the particular backend.    #[error("{0}")]    Unsupported(String),} pub type BackendResult<T> = Result<T, BackendError>; #[derive(ContentHash, Debug, PartialEq, Eq, Clone, Hash)]pub enum TreeValue {    File { id: FileId, executable: bool },    Symlink(SymlinkId),    Tree(TreeId),    GitSubmodule(CommitId),    Conflict(ConflictId),} impl TreeValue {    pub fn hex(&self) -> String {        match self {            TreeValue::File { id, .. } => id.hex(),            TreeValue::Symlink(id) => id.hex(),            TreeValue::Tree(id) => id.hex(),            TreeValue::GitSubmodule(id) => id.hex(),            TreeValue::Conflict(id) => id.hex(),        }    }} #[derive(Debug, PartialEq, Eq, Clone)]pub struct TreeEntry<'a> {    name: &'a RepoPathComponent,    value: &'a TreeValue,} impl<'a> TreeEntry<'a> {    pub fn new(name: &'a RepoPathComponent, value: &'a TreeValue) -> Self {        TreeEntry { name, value }    }     pub fn name(&self) -> &'a RepoPathComponent {        self.name    }     pub fn value(&self) -> &'a TreeValue {        self.value    }} pub struct TreeEntriesNonRecursiveIterator<'a> {    iter: std::collections::btree_map::Iter<'a, RepoPathComponentBuf, TreeValue>,} impl<'a> Iterator for TreeEntriesNonRecursiveIterator<'a> {    type Item = TreeEntry<'a>;     fn next(&mut self) -> Option<Self::Item> {        self.iter            .next()            .map(|(name, value)| TreeEntry { name, value })    }} #[derive(ContentHash, Default, PartialEq, Eq, Debug, Clone)]pub struct Tree {    entries: BTreeMap<RepoPathComponentBuf, TreeValue>,} impl Tree {    pub fn is_empty(&self) -> bool {        self.entries.is_empty()    }     pub fn names(&self) -> impl Iterator<Item = &RepoPathComponent> {        self.entries.keys().map(|name| name.as_ref())    }     pub fn entries(&self) -> TreeEntriesNonRecursiveIterator {        TreeEntriesNonRecursiveIterator {            iter: self.entries.iter(),        }    }     pub fn set(&mut self, name: RepoPathComponentBuf, value: TreeValue) {        self.entries.insert(name, value);    }     pub fn remove(&mut self, name: &RepoPathComponent) {        self.entries.remove(name);    }     pub fn set_or_remove(&mut self, name: &RepoPathComponent, value: Option<TreeValue>) {        match value {            None => {                self.entries.remove(name);            }            Some(value) => {                self.entries.insert(name.to_owned(), value);            }        }    }     pub fn entry(&self, name: &RepoPathComponent) -> Option<TreeEntry> {        self.entries            .get_key_value(name)            .map(|(name, value)| TreeEntry { name, value })    }     pub fn value(&self, name: &RepoPathComponent) -> Option<&TreeValue> {        self.entries.get(name)    }} pub fn make_root_commit(root_change_id: ChangeId, empty_tree_id: TreeId) -> Commit {    let timestamp = Timestamp {        timestamp: MillisSinceEpoch(0),        tz_offset: 0,    };    let signature = Signature {        name: String::new(),        email: String::new(),        timestamp,    };    Commit {        parents: vec![],        predecessors: vec![],        root_tree: MergedTreeId::resolved(empty_tree_id),        change_id: root_change_id,        description: String::new(),        author: signature.clone(),        committer: signature,        secure_sig: None,    }} /// Defines the interface for commit backends.#[async_trait]pub trait Backend: Send + Sync + Debug {    fn as_any(&self) -> &dyn Any;     /// A unique name that identifies this backend. Written to    /// `.jj/repo/store/backend` when the repo is created.    fn name(&self) -> &str;     /// The length of commit IDs in bytes.    fn commit_id_length(&self) -> usize;     /// The length of change IDs in bytes.    fn change_id_length(&self) -> usize;     fn root_commit_id(&self) -> &CommitId;     fn root_change_id(&self) -> &ChangeId;     fn empty_tree_id(&self) -> &TreeId;     /// An estimate of how many concurrent requests this backend handles well. A    /// local backend like the Git backend (at until it supports partial clones)    /// may want to set this to 1. A cloud-backed backend may want to set it to    /// 100 or so.    ///    /// It is not guaranteed that at most this number of concurrent requests are    /// sent.    fn concurrency(&self) -> usize;     async fn read_file(&self, path: &RepoPath, id: &FileId) -> BackendResult<Box<dyn Read>>;     async fn write_file(        &self,        path: &RepoPath,        contents: &mut (dyn Read + Send),    ) -> BackendResult<FileId>;     async fn read_symlink(&self, path: &RepoPath, id: &SymlinkId) -> BackendResult<String>;     async fn write_symlink(&self, path: &RepoPath, target: &str) -> BackendResult<SymlinkId>;     async fn read_tree(&self, path: &RepoPath, id: &TreeId) -> BackendResult<Tree>;     async fn write_tree(&self, path: &RepoPath, contents: &Tree) -> BackendResult<TreeId>;     // Not async because it would force `MergedTree::value()` to be async. We don't    // need this to be async anyway because it's only used by legacy repos.    fn read_conflict(&self, path: &RepoPath, id: &ConflictId) -> BackendResult<Conflict>;     fn write_conflict(&self, path: &RepoPath, contents: &Conflict) -> BackendResult<ConflictId>;     async fn read_commit(&self, id: &CommitId) -> BackendResult<Commit>;     /// Writes a commit and returns its ID and the commit itself. The commit    /// should contain the data that was actually written, which may differ    /// from the data passed in. For example, the backend may change the    /// committer name to an authenticated user's name, or the backend's    /// timestamps may have less precision than the millisecond precision in    /// `Commit`.    ///    /// The `sign_with` parameter could contain a function to cryptographically    /// sign some binary representation of the commit.    /// If the backend supports it, it could call it and store the result in    /// an implementation specific fashion, and both `read_commit` and the    /// return of `write_commit` should read it back as the `secure_sig`    /// field.    async fn write_commit(        &self,        contents: Commit,        sign_with: Option<&mut SigningFn>,    ) -> BackendResult<(CommitId, Commit)>;     /// Get copy records for the dag range `root..head`.  If `paths` is None    /// include all paths, otherwise restrict to only `paths`.    ///    /// The exact order these are returned is unspecified, but it is guaranteed    /// to be reverse-topological. That is, for any two copy records with    /// different commit ids A and B, if A is an ancestor of B, A is streamed    /// after B.    ///    /// Streaming by design to better support large backends which may have very    /// large single-file histories. This also allows more iterative algorithms    /// like blame/annotate to short-circuit after a point without wasting    /// unnecessary resources.    fn get_copy_records(        &self,        paths: Option<&[RepoPathBuf]>,        root: &CommitId,        head: &CommitId,    ) -> BackendResult<BoxStream<BackendResult<CopyRecord>>>;     /// Perform garbage collection.    ///    /// All commits found in the `index` won't be removed. In addition to that,    /// objects created after `keep_newer` will be preserved. This mitigates a    /// risk of deleting new commits created concurrently by another process.    fn gc(&self, index: &dyn Index, keep_newer: SystemTime) -> BackendResult<()>;}