// Copyright 2020-2023 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. //! Utility for operation id resolution and traversal. use std::cmp::Ordering;use std::collections::HashMap;use std::collections::HashSet;use std::slice;use std::sync::Arc; use futures::Stream;use futures::StreamExt as _;use futures::TryStreamExt as _;use futures::future::ready;use futures::future::try_join_all;use futures::stream;use itertools::Itertools as _;use pollster::FutureExt as _;use thiserror::Error; use crate::dag_walk_async;use crate::object_id::HexPrefix;use crate::object_id::PrefixResolution;use crate::op_heads_store;use crate::op_heads_store::OpHeadsStore;use crate::op_heads_store::OpHeadsStoreError;use crate::op_store::OpStore;use crate::op_store::OpStoreError;use crate::op_store::OpStoreResult;use crate::op_store::OperationId;use crate::operation::Operation;use crate::repo::ReadonlyRepo;use crate::repo::Repo as _;use crate::repo::RepoLoader; /// Error that may occur during evaluation of operation set expression.#[derive(Debug, Error)]pub enum OpsetEvaluationError {    /// Failed to resolve operation set expression.    #[error(transparent)]    OpsetResolution(#[from] OpsetResolutionError),    /// Failed to read op heads.    #[error(transparent)]    OpHeadsStore(#[from] OpHeadsStoreError),    /// Failed to access operation object.    #[error(transparent)]    OpStore(#[from] OpStoreError),} /// Error that may occur during parsing and resolution of operation set/// expression.#[derive(Debug, Error)]pub enum OpsetResolutionError {    // TODO: Maybe empty/multiple operations should be allowed, and rejected by    // caller as needed.    /// Expression resolved to multiple operations.    #[error(r#"The "{expr}" expression resolved to more than one operation"#)]    MultipleOperations {        /// Source expression.        expr: String,        /// Matched operation ids.        candidates: Vec<OperationId>,    },    /// Expression resolved to no operations.    #[error(r#"The "{0}" expression resolved to no operations"#)]    EmptyOperations(String),    /// Invalid symbol as an operation ID.    #[error(r#"Operation ID "{0}" is not a valid hexadecimal prefix"#)]    InvalidIdPrefix(String),    /// Operation ID not found.    #[error(r#"No operation ID matching "{0}""#)]    NoSuchOperation(String),    /// Operation ID prefix matches multiple operations.    #[error(r#"Operation ID prefix "{0}" is ambiguous"#)]    AmbiguousIdPrefix(String),} /// Resolves operation set expression without loading a repo.pub async fn resolve_op_for_load(    repo_loader: &RepoLoader,    op_str: &str,) -> Result<Operation, OpsetEvaluationError> {    let op_store = repo_loader.op_store();    let op_heads_store = repo_loader.op_heads_store().as_ref();    let get_current_op = async || {        op_heads_store::resolve_op_heads(op_heads_store, op_store, async |op_heads| {            Err(OpsetResolutionError::MultipleOperations {                expr: "@".to_owned(),                candidates: op_heads.iter().map(|op| op.id().clone()).collect(),            }            .into())        })        .await    };    let get_head_ops = async || get_current_head_ops(op_store, op_heads_store).await;    resolve_single_op(op_store, get_current_op, get_head_ops, op_str).await} /// Resolves operation set expression against the loaded repo.////// The "@" symbol will be resolved to the operation the repo was loaded at.pub async fn resolve_op_with_repo(    repo: &ReadonlyRepo,    op_str: &str,) -> Result<Operation, OpsetEvaluationError> {    resolve_op_at(repo.op_store(), slice::from_ref(repo.operation()), op_str).await} /// Resolves operation set expression at the given head operations.pub async fn resolve_op_at(    op_store: &Arc<dyn OpStore>,    head_ops: &[Operation],    op_str: &str,) -> Result<Operation, OpsetEvaluationError> {    let get_current_op = async || match head_ops {        [head_op] => Ok(head_op.clone()),        [] => Err(OpsetResolutionError::EmptyOperations("@".to_owned()).into()),        _ => Err(OpsetResolutionError::MultipleOperations {            expr: "@".to_owned(),            candidates: head_ops.iter().map(|op| op.id().clone()).collect(),        }        .into()),    };    let get_head_ops = async || Ok(head_ops.to_vec());    resolve_single_op(op_store, get_current_op, get_head_ops, op_str).await} /// Resolves operation set expression with the given "@" symbol resolution/// callbacks.async fn resolve_single_op(    op_store: &Arc<dyn OpStore>,    get_current_op: impl AsyncFnOnce() -> Result<Operation, OpsetEvaluationError>,    get_head_ops: impl AsyncFnOnce() -> Result<Vec<Operation>, OpsetEvaluationError>,    op_str: &str,) -> Result<Operation, OpsetEvaluationError> {    let op_symbol = op_str.trim_end_matches(['-', '+']);    let op_postfix = &op_str[op_symbol.len()..];    let head_ops = if op_postfix.contains('+') {        Some(get_head_ops().await?)    } else {        None    };    let mut operation = match op_symbol {        "@" => get_current_op().await,        s => resolve_single_op_from_store(op_store, s).await,    }?;    for (i, c) in op_postfix.chars().enumerate() {        let mut neighbor_ops = match c {            '-' => operation.parents().await?,            '+' => find_child_ops(head_ops.as_ref().unwrap(), operation.id()).await?,            _ => unreachable!(),        };        operation = match neighbor_ops.len() {            // Since there is no hint provided for `EmptyOperations` in            // `opset_resolution_error_hint()` (there would be no useful hint for the            // user to take action on anyway), we don't have to worry about op ids being            // incoherent with the op set expression shown to the user, unlike for the            // `MultipleOperations` variant.            //            // The full op set expression is guaranteed to be empty in this case,            // because ancestors/descendants of an empty operation are empty.            0 => Err(OpsetResolutionError::EmptyOperations(op_str.to_owned()))?,            1 => neighbor_ops.pop().unwrap(),            // Returns the exact subexpression that resolves to multiple operations,            // rather than the full expression provided by the user.            _ => Err(OpsetResolutionError::MultipleOperations {                expr: op_str[..=op_symbol.len() + i].to_owned(),                candidates: neighbor_ops.iter().map(|op| op.id().clone()).collect(),            })?,        };    }    Ok(operation)} async fn resolve_single_op_from_store(    op_store: &Arc<dyn OpStore>,    op_str: &str,) -> Result<Operation, OpsetEvaluationError> {    if op_str.is_empty() {        return Err(OpsetResolutionError::InvalidIdPrefix(op_str.to_owned()).into());    }    let prefix = HexPrefix::try_from_hex(op_str)        .ok_or_else(|| OpsetResolutionError::InvalidIdPrefix(op_str.to_owned()))?;    match op_store.resolve_operation_id_prefix(&prefix).await? {        PrefixResolution::NoMatch => {            Err(OpsetResolutionError::NoSuchOperation(op_str.to_owned()).into())        }        PrefixResolution::SingleMatch(op_id) => {            let data = op_store.read_operation(&op_id).await?;            Ok(Operation::new(op_store.clone(), op_id, data))        }        PrefixResolution::AmbiguousMatch => {            Err(OpsetResolutionError::AmbiguousIdPrefix(op_str.to_owned()).into())        }    }} /// Loads the current head operations. The returned operations may contain/// redundant ones which are ancestors of the other heads.pub async fn get_current_head_ops(    op_store: &Arc<dyn OpStore>,    op_heads_store: &dyn OpHeadsStore,) -> Result<Vec<Operation>, OpsetEvaluationError> {    let head_ops_futures = op_heads_store.get_op_heads().await?.into_iter().map(        async |id| -> OpStoreResult<Operation> {            let data = op_store.read_operation(&id).await?;            Ok(Operation::new(op_store.clone(), id, data))        },    );    let mut head_ops = try_join_all(head_ops_futures).await?;    // To stabilize output, sort in the same order as resolve_op_heads()    head_ops.sort_by_key(|op| op.metadata().time.end.timestamp);    Ok(head_ops)} /// Looks up children of the `root_op_id` by traversing from the `head_ops`.////// This will be slow if the `root_op_id` is far away (or unreachable) from the/// `head_ops`.async fn find_child_ops(    head_ops: &[Operation],    root_op_id: &OperationId,) -> OpStoreResult<Vec<Operation>> {    walk_ancestors(head_ops)        .take_while(|res| ready(res.as_ref().map_or(true, |op| op.id() != root_op_id)))        .try_filter(|op| ready(op.parent_ids().iter().any(|id| id == root_op_id)))        .try_collect()        .await} #[derive(Clone, Debug, Eq, Hash, PartialEq)]struct OperationByEndTime(Operation); impl Ord for OperationByEndTime {    fn cmp(&self, other: &Self) -> Ordering {        let self_end_time = &self.0.metadata().time.end;        let other_end_time = &other.0.metadata().time.end;        self_end_time            .cmp(other_end_time)            .then_with(|| self.0.cmp(&other.0)) // to comply with Eq    }} impl PartialOrd for OperationByEndTime {    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {        Some(self.cmp(other))    }} /// Walks `head_ops` and their ancestors in reverse topological order.pub fn walk_ancestors(    head_ops: &[Operation],) -> impl Stream<Item = OpStoreResult<Operation>> + use<> {    let head_ops = head_ops        .iter()        .cloned()        .map(OperationByEndTime)        .collect_vec();    // Lazily load operations based on timestamp-based heuristic. This works so long    // as the operation history is mostly linear.    dag_walk_async::topo_order_reverse_lazy(        head_ops.into_iter().map(Ok),        |OperationByEndTime(op)| op.id().clone(),        async |OperationByEndTime(op)| match op.parents().await {            Ok(parents) => parents                .into_iter()                .map(|parent| Ok(OperationByEndTime(parent)))                .collect_vec(),            Err(err) => vec![Err(err)],        },        |_| panic!("graph has cycle"),    )    .map_ok(|OperationByEndTime(op)| op)} /// Walks ancestors from `head_ops` in reverse topological order, excluding/// ancestors of `root_ops`.pub fn walk_ancestors_range(    head_ops: &[Operation],    root_ops: &[Operation],) -> impl Stream<Item = OpStoreResult<Operation>> + use<> {    let mut start_ops = itertools::chain(head_ops, root_ops)        .cloned()        .map(OperationByEndTime)        .collect_vec();     // Consume items until root_ops to get rid of unwanted ops.    let leading_items = if root_ops.is_empty() {        vec![]    } else {        let unwanted_ids = root_ops.iter().map(|op| op.id().clone()).collect();        collect_ancestors_until_roots(&mut start_ops, unwanted_ids)    };     // Lazily load operations based on timestamp-based heuristic. This works so long    // as the operation history is mostly linear.    let trailing_stream = dag_walk_async::topo_order_reverse_lazy(        start_ops.into_iter().map(Ok),        |OperationByEndTime(op)| op.id().clone(),        async |OperationByEndTime(op)| match op.parents().await {            Ok(parents) => parents                .into_iter()                .map(|op| Ok(OperationByEndTime(op)))                .collect_vec(),            Err(err) => vec![Err(err)],        },        |_| panic!("graph has cycle"),    )    .map_ok(|OperationByEndTime(op)| op);    stream::iter(leading_items).chain(trailing_stream)} fn collect_ancestors_until_roots(    start_ops: &mut Vec<OperationByEndTime>,    mut unwanted_ids: HashSet<OperationId>,) -> Vec<OpStoreResult<Operation>> {    let sorted_ops = match dag_walk_async::topo_order_reverse_chunked(        start_ops,        |OperationByEndTime(op)| op.id().clone(),        async |OperationByEndTime(op)| match op.parents().await {            Ok(parents) => parents                .into_iter()                .map(|op| Ok(OperationByEndTime(op)))                .collect_vec(),            Err(err) => vec![Err(err)],        },        |_| panic!("graph has cycle"),    )    .block_on()    {        Ok(sorted_ops) => sorted_ops,        Err(err) => return vec![Err(err)],    };    let mut items = Vec::new();    for OperationByEndTime(op) in sorted_ops {        if unwanted_ids.contains(op.id()) {            unwanted_ids.extend(op.parent_ids().iter().cloned());        } else {            items.push(Ok(op));        }    }    // Don't visit ancestors of unwanted ops further.    start_ops.retain(|OperationByEndTime(op)| !unwanted_ids.contains(op.id()));    items} /// Finds the closest common ancestor of `set1` and `set2`. Uses the end/// timestamp as a heuristic.// TODO: We should probably make this a function on `OpStore` instead of// relying on heuristics (even if the implementation of the trait might rely on// the same heuristic initially).pub async fn closest_common_ancestors(    set1: impl IntoIterator<Item = Operation>,    set2: impl IntoIterator<Item = Operation>,) -> OpStoreResult<Vec<Operation>> {    let ancestor_ops = dag_walk_async::closest_common_nodes(        set1.into_iter().map(OperationByEndTime),        set2.into_iter().map(OperationByEndTime),        |op: &OperationByEndTime| op.0.id().clone(),        async |op: &OperationByEndTime| {            op.0.parents()                .await                .map(|parents| parents.into_iter().map(OperationByEndTime))        },    )    .await?;    Ok(ancestor_ops.into_iter().map(|op| op.0).collect())} /// Stats about `reparent_range()`.#[derive(Clone, Debug, Eq, PartialEq)]pub struct ReparentStats {    /// New head operation ids in order of the old `head_ops`.    pub new_head_ids: Vec<OperationId>,    /// The number of rewritten operations.    pub rewritten_count: usize,    /// The number of ancestor operations that become unreachable from the    /// rewritten heads.    pub unreachable_count: usize,} /// Reparents the operation range `root_ops..head_ops` onto the `dest_op`.////// Returns the new head operation ids as well as some stats. If the old/// operation heads are remapped to the new heads, the operations within the/// range `dest_op..root_ops` become unreachable.////// If the source operation range `root_ops..head_ops` was empty, the/// `new_head_ids` will be `[dest_op.id()]`, meaning the `dest_op` is the head.// TODO: Find better place to host this function. It might be an OpStore method.pub async fn reparent_range(    op_store: &dyn OpStore,    root_ops: &[Operation],    head_ops: &[Operation],    dest_op: &Operation,) -> OpStoreResult<ReparentStats> {    let ops_to_reparent: Vec<_> = walk_ancestors_range(head_ops, root_ops)        .try_collect()        .await?;    let unreachable_count = walk_ancestors_range(root_ops, slice::from_ref(dest_op))        .try_fold(0, |acc, _| async move { Ok(acc + 1) })        .await?;     assert!(        ops_to_reparent            .last()            .is_none_or(|op| op.id() != op_store.root_operation_id()),        "root operation cannot be rewritten"    );    let mut rewritten_ids = HashMap::new();    for old_op in ops_to_reparent.into_iter().rev() {        let mut data = old_op.store_operation().clone();        let mut dest_once = Some(dest_op.id());        data.parents = data            .parents            .iter()            .filter_map(|id| rewritten_ids.get(id).or_else(|| dest_once.take()))            .cloned()            .collect();        let new_id = op_store.write_operation(&data).await?;        rewritten_ids.insert(old_op.id().clone(), new_id);    }     let mut dest_once = Some(dest_op.id());    let new_head_ids = head_ops        .iter()        .filter_map(|op| rewritten_ids.get(op.id()).or_else(|| dest_once.take()))        .cloned()        .collect();    Ok(ReparentStats {        new_head_ids,        rewritten_count: rewritten_ids.len(),        unreachable_count,    })}