jj/cli/src/commit_templater.rs

// 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.

use std::cmp::max;
use std::collections::HashMap;
use std::io;
use std::rc::Rc;

use itertools::Itertools as _;
use jj_lib::backend::{ChangeId, CommitId};
use jj_lib::commit::Commit;
use jj_lib::hex_util::to_reverse_hex;
use jj_lib::id_prefix::IdPrefixContext;
use jj_lib::object_id::ObjectId as _;
use jj_lib::op_store::{RefTarget, WorkspaceId};
use jj_lib::repo::Repo;
use jj_lib::{git, rewrite};
use once_cell::unsync::OnceCell;

use crate::formatter::Formatter;
use crate::template_builder::{
    self, merge_fn_map, BuildContext, CoreTemplateBuildFnTable, CoreTemplatePropertyKind,
    IntoTemplateProperty, TemplateBuildMethodFnMap, TemplateLanguage,
};
use crate::template_parser::{self, FunctionCallNode, TemplateAliasesMap, TemplateParseResult};
use crate::templater::{
    self, IntoTemplate, PlainTextFormattedProperty, Template, TemplateFunction, TemplateProperty,
    TemplatePropertyFn,
};
use crate::text_util;

pub struct CommitTemplateLanguage<'repo> {
    repo: &'repo dyn Repo,
    workspace_id: WorkspaceId,
    id_prefix_context: &'repo IdPrefixContext,
    build_fn_table: CommitTemplateBuildFnTable<'repo>,
    keyword_cache: CommitKeywordCache,
}

pub trait CommitTemplateLanguageExtension {
    fn build_fn_table<'repo>(&self) -> CommitTemplateBuildFnTable<'repo>;
}

impl<'repo> TemplateLanguage<'repo> for CommitTemplateLanguage<'repo> {
    type Context = Commit;
    type Property = CommitTemplatePropertyKind<'repo>;

    template_builder::impl_core_wrap_property_fns!('repo, CommitTemplatePropertyKind::Core);

    fn build_self(&self) -> Self::Property {
        // Commit object is lightweight (a few Arc + CommitId)
        self.wrap_commit(TemplatePropertyFn(|commit: &Commit| Ok(commit.clone())))
    }

    fn build_method(
        &self,
        build_ctx: &BuildContext<Self::Property>,
        property: Self::Property,
        function: &FunctionCallNode,
    ) -> TemplateParseResult<Self::Property> {
        match property {
            CommitTemplatePropertyKind::Core(property) => {
                let table = &self.build_fn_table.core;
                table.build_method(self, build_ctx, property, function)
            }
            CommitTemplatePropertyKind::Commit(property) => {
                let table = &self.build_fn_table.commit_methods;
                let build = template_parser::lookup_method("Commit", table, function)?;
                build(self, build_ctx, property, function)
            }
            CommitTemplatePropertyKind::CommitList(property) => {
                // TODO: migrate to table?
                template_builder::build_unformattable_list_method(
                    self,
                    build_ctx,
                    property,
                    function,
                    |item| self.wrap_commit(item),
                )
            }
            CommitTemplatePropertyKind::RefName(property) => {
                let table = &self.build_fn_table.ref_name_methods;
                let build = template_parser::lookup_method("RefName", table, function)?;
                build(self, build_ctx, property, function)
            }
            CommitTemplatePropertyKind::RefNameList(property) => {
                // TODO: migrate to table?
                template_builder::build_formattable_list_method(
                    self,
                    build_ctx,
                    property,
                    function,
                    |item| self.wrap_ref_name(item),
                )
            }
            CommitTemplatePropertyKind::CommitOrChangeId(property) => {
                let table = &self.build_fn_table.commit_or_change_id_methods;
                let build = template_parser::lookup_method("CommitOrChangeId", table, function)?;
                build(self, build_ctx, property, function)
            }
            CommitTemplatePropertyKind::ShortestIdPrefix(property) => {
                let table = &self.build_fn_table.shortest_id_prefix_methods;
                let build = template_parser::lookup_method("ShortestIdPrefix", table, function)?;
                build(self, build_ctx, property, function)
            }
        }
    }
}

// If we need to add multiple languages that support Commit types, this can be
// turned into a trait which extends TemplateLanguage.
impl<'repo> CommitTemplateLanguage<'repo> {
    fn wrap_commit(
        &self,
        property: impl TemplateProperty<Commit, Output = Commit> + 'repo,
    ) -> CommitTemplatePropertyKind<'repo> {
        CommitTemplatePropertyKind::Commit(Box::new(property))
    }

    fn wrap_commit_list(
        &self,
        property: impl TemplateProperty<Commit, Output = Vec<Commit>> + 'repo,
    ) -> CommitTemplatePropertyKind<'repo> {
        CommitTemplatePropertyKind::CommitList(Box::new(property))
    }

    fn wrap_ref_name(
        &self,
        property: impl TemplateProperty<Commit, Output = RefName> + 'repo,
    ) -> CommitTemplatePropertyKind<'repo> {
        CommitTemplatePropertyKind::RefName(Box::new(property))
    }

    fn wrap_ref_name_list(
        &self,
        property: impl TemplateProperty<Commit, Output = Vec<RefName>> + 'repo,
    ) -> CommitTemplatePropertyKind<'repo> {
        CommitTemplatePropertyKind::RefNameList(Box::new(property))
    }

    fn wrap_commit_or_change_id(
        &self,
        property: impl TemplateProperty<Commit, Output = CommitOrChangeId> + 'repo,
    ) -> CommitTemplatePropertyKind<'repo> {
        CommitTemplatePropertyKind::CommitOrChangeId(Box::new(property))
    }

    fn wrap_shortest_id_prefix(
        &self,
        property: impl TemplateProperty<Commit, Output = ShortestIdPrefix> + 'repo,
    ) -> CommitTemplatePropertyKind<'repo> {
        CommitTemplatePropertyKind::ShortestIdPrefix(Box::new(property))
    }
}

pub enum CommitTemplatePropertyKind<'repo> {
    Core(CoreTemplatePropertyKind<'repo, Commit>),
    Commit(Box<dyn TemplateProperty<Commit, Output = Commit> + 'repo>),
    CommitList(Box<dyn TemplateProperty<Commit, Output = Vec<Commit>> + 'repo>),
    RefName(Box<dyn TemplateProperty<Commit, Output = RefName> + 'repo>),
    RefNameList(Box<dyn TemplateProperty<Commit, Output = Vec<RefName>> + 'repo>),
    CommitOrChangeId(Box<dyn TemplateProperty<Commit, Output = CommitOrChangeId> + 'repo>),
    ShortestIdPrefix(Box<dyn TemplateProperty<Commit, Output = ShortestIdPrefix> + 'repo>),
}

impl<'repo> IntoTemplateProperty<'repo, Commit> for CommitTemplatePropertyKind<'repo> {
    fn try_into_boolean(self) -> Option<Box<dyn TemplateProperty<Commit, Output = bool> + 'repo>> {
        match self {
            CommitTemplatePropertyKind::Core(property) => property.try_into_boolean(),
            CommitTemplatePropertyKind::Commit(_) => None,
            CommitTemplatePropertyKind::CommitList(property) => {
                Some(Box::new(TemplateFunction::new(property, |l| {
                    Ok(!l.is_empty())
                })))
            }
            CommitTemplatePropertyKind::RefName(_) => None,
            CommitTemplatePropertyKind::RefNameList(property) => {
                Some(Box::new(TemplateFunction::new(property, |l| {
                    Ok(!l.is_empty())
                })))
            }
            CommitTemplatePropertyKind::CommitOrChangeId(_) => None,
            CommitTemplatePropertyKind::ShortestIdPrefix(_) => None,
        }
    }

    fn try_into_integer(self) -> Option<Box<dyn TemplateProperty<Commit, Output = i64> + 'repo>> {
        match self {
            CommitTemplatePropertyKind::Core(property) => property.try_into_integer(),
            _ => None,
        }
    }

    fn try_into_plain_text(
        self,
    ) -> Option<Box<dyn TemplateProperty<Commit, Output = String> + 'repo>> {
        match self {
            CommitTemplatePropertyKind::Core(property) => property.try_into_plain_text(),
            _ => {
                let template = self.try_into_template()?;
                Some(Box::new(PlainTextFormattedProperty::new(template)))
            }
        }
    }

    fn try_into_template(self) -> Option<Box<dyn Template<Commit> + 'repo>> {
        match self {
            CommitTemplatePropertyKind::Core(property) => property.try_into_template(),
            CommitTemplatePropertyKind::Commit(_) => None,
            CommitTemplatePropertyKind::CommitList(_) => None,
            CommitTemplatePropertyKind::RefName(property) => Some(property.into_template()),
            CommitTemplatePropertyKind::RefNameList(property) => Some(property.into_template()),
            CommitTemplatePropertyKind::CommitOrChangeId(property) => {
                Some(property.into_template())
            }
            CommitTemplatePropertyKind::ShortestIdPrefix(property) => {
                Some(property.into_template())
            }
        }
    }
}

/// Table of functions that translate method call node of self type `T`.
pub type CommitTemplateBuildMethodFnMap<'repo, T> =
    TemplateBuildMethodFnMap<'repo, CommitTemplateLanguage<'repo>, T>;

/// Symbol table of methods available in the commit template.
pub struct CommitTemplateBuildFnTable<'repo> {
    pub core: CoreTemplateBuildFnTable<'repo, CommitTemplateLanguage<'repo>>,
    pub commit_methods: CommitTemplateBuildMethodFnMap<'repo, Commit>,
    pub ref_name_methods: CommitTemplateBuildMethodFnMap<'repo, RefName>,
    pub commit_or_change_id_methods: CommitTemplateBuildMethodFnMap<'repo, CommitOrChangeId>,
    pub shortest_id_prefix_methods: CommitTemplateBuildMethodFnMap<'repo, ShortestIdPrefix>,
}

impl<'repo> CommitTemplateBuildFnTable<'repo> {
    /// Creates new symbol table containing the builtin methods.
    fn builtin() -> Self {
        CommitTemplateBuildFnTable {
            core: CoreTemplateBuildFnTable::builtin(),
            commit_methods: builtin_commit_methods(),
            ref_name_methods: builtin_ref_name_methods(),
            commit_or_change_id_methods: builtin_commit_or_change_id_methods(),
            shortest_id_prefix_methods: builtin_shortest_id_prefix_methods(),
        }
    }

    pub fn empty() -> Self {
        CommitTemplateBuildFnTable {
            core: CoreTemplateBuildFnTable::empty(),
            commit_methods: HashMap::new(),
            ref_name_methods: HashMap::new(),
            commit_or_change_id_methods: HashMap::new(),
            shortest_id_prefix_methods: HashMap::new(),
        }
    }

    fn merge(&mut self, extension: CommitTemplateBuildFnTable<'repo>) {
        let CommitTemplateBuildFnTable {
            core,
            commit_methods,
            ref_name_methods,
            commit_or_change_id_methods,
            shortest_id_prefix_methods,
        } = extension;

        self.core.merge(core);
        merge_fn_map(&mut self.commit_methods, commit_methods);
        merge_fn_map(&mut self.ref_name_methods, ref_name_methods);
        merge_fn_map(
            &mut self.commit_or_change_id_methods,
            commit_or_change_id_methods,
        );
        merge_fn_map(
            &mut self.shortest_id_prefix_methods,
            shortest_id_prefix_methods,
        );
    }
}

#[derive(Debug, Default)]
struct CommitKeywordCache {
    // Build index lazily, and Rc to get away from &self lifetime.
    branches_index: OnceCell<Rc<RefNamesIndex>>,
    tags_index: OnceCell<Rc<RefNamesIndex>>,
    git_refs_index: OnceCell<Rc<RefNamesIndex>>,
}

impl CommitKeywordCache {
    fn branches_index(&self, repo: &dyn Repo) -> &Rc<RefNamesIndex> {
        self.branches_index
            .get_or_init(|| Rc::new(build_branches_index(repo)))
    }

    fn tags_index(&self, repo: &dyn Repo) -> &Rc<RefNamesIndex> {
        self.tags_index
            .get_or_init(|| Rc::new(build_ref_names_index(repo.view().tags())))
    }

    fn git_refs_index(&self, repo: &dyn Repo) -> &Rc<RefNamesIndex> {
        self.git_refs_index
            .get_or_init(|| Rc::new(build_ref_names_index(repo.view().git_refs())))
    }
}

fn builtin_commit_methods<'repo>() -> CommitTemplateBuildMethodFnMap<'repo, Commit> {
    // Not using maplit::hashmap!{} or custom declarative macro here because
    // code completion inside macro is quite restricted.
    let mut map = CommitTemplateBuildMethodFnMap::<Commit>::new();
    map.insert(
        "description",
        |language, _build_ctx, self_property, function| {
            template_parser::expect_no_arguments(function)?;
            let out_property = TemplateFunction::new(self_property, |commit| {
                Ok(text_util::complete_newline(commit.description()))
            });
            Ok(language.wrap_string(out_property))
        },
    );
    map.insert(
        "change_id",
        |language, _build_ctx, self_property, function| {
            template_parser::expect_no_arguments(function)?;
            let out_property = TemplateFunction::new(self_property, |commit| {
                Ok(CommitOrChangeId::Change(commit.change_id().to_owned()))
            });
            Ok(language.wrap_commit_or_change_id(out_property))
        },
    );
    map.insert(
        "commit_id",
        |language, _build_ctx, self_property, function| {
            template_parser::expect_no_arguments(function)?;
            let out_property = TemplateFunction::new(self_property, |commit| {
                Ok(CommitOrChangeId::Commit(commit.id().to_owned()))
            });
            Ok(language.wrap_commit_or_change_id(out_property))
        },
    );
    map.insert(
        "parents",
        |language, _build_ctx, self_property, function| {
            template_parser::expect_no_arguments(function)?;
            let out_property = TemplateFunction::new(self_property, |commit| Ok(commit.parents()));
            Ok(language.wrap_commit_list(out_property))
        },
    );
    map.insert("author", |language, _build_ctx, self_property, function| {
        template_parser::expect_no_arguments(function)?;
        let out_property =
            TemplateFunction::new(self_property, |commit| Ok(commit.author().clone()));
        Ok(language.wrap_signature(out_property))
    });
    map.insert(
        "committer",
        |language, _build_ctx, self_property, function| {
            template_parser::expect_no_arguments(function)?;
            let out_property =
                TemplateFunction::new(self_property, |commit| Ok(commit.committer().clone()));
            Ok(language.wrap_signature(out_property))
        },
    );
    map.insert(
        "working_copies",
        |language, _build_ctx, self_property, function| {
            template_parser::expect_no_arguments(function)?;
            let repo = language.repo;
            let out_property = TemplateFunction::new(self_property, |commit| {
                Ok(extract_working_copies(repo, &commit))
            });
            Ok(language.wrap_string(out_property))
        },
    );
    map.insert(
        "current_working_copy",
        |language, _build_ctx, self_property, function| {
            template_parser::expect_no_arguments(function)?;
            let repo = language.repo;
            let workspace_id = language.workspace_id.clone();
            let out_property = TemplateFunction::new(self_property, move |commit| {
                Ok(Some(commit.id()) == repo.view().get_wc_commit_id(&workspace_id))
            });
            Ok(language.wrap_boolean(out_property))
        },
    );
    map.insert(
        "branches",
        |language, _build_ctx, self_property, function| {
            template_parser::expect_no_arguments(function)?;
            let index = language.keyword_cache.branches_index(language.repo).clone();
            let out_property = TemplateFunction::new(self_property, move |commit| {
                Ok(index
                    .get(commit.id())
                    .iter()
                    .filter(|ref_name| ref_name.is_local() || !ref_name.synced)
                    .cloned()
                    .collect())
            });
            Ok(language.wrap_ref_name_list(out_property))
        },
    );
    map.insert(
        "local_branches",
        |language, _build_ctx, self_property, function| {
            template_parser::expect_no_arguments(function)?;
            let index = language.keyword_cache.branches_index(language.repo).clone();
            let out_property = TemplateFunction::new(self_property, move |commit| {
                Ok(index
                    .get(commit.id())
                    .iter()
                    .filter(|ref_name| ref_name.is_local())
                    .cloned()
                    .collect())
            });
            Ok(language.wrap_ref_name_list(out_property))
        },
    );
    map.insert(
        "remote_branches",
        |language, _build_ctx, self_property, function| {
            template_parser::expect_no_arguments(function)?;
            let index = language.keyword_cache.branches_index(language.repo).clone();
            let out_property = TemplateFunction::new(self_property, move |commit| {
                Ok(index
                    .get(commit.id())
                    .iter()
                    .filter(|ref_name| ref_name.is_remote())
                    .cloned()
                    .collect())
            });
            Ok(language.wrap_ref_name_list(out_property))
        },
    );
    map.insert("tags", |language, _build_ctx, self_property, function| {
        template_parser::expect_no_arguments(function)?;
        let index = language.keyword_cache.tags_index(language.repo).clone();
        let out_property = TemplateFunction::new(self_property, move |commit| {
            Ok(index.get(commit.id()).to_vec())
        });
        Ok(language.wrap_ref_name_list(out_property))
    });
    map.insert(
        "git_refs",
        |language, _build_ctx, self_property, function| {
            template_parser::expect_no_arguments(function)?;
            let index = language.keyword_cache.git_refs_index(language.repo).clone();
            let out_property = TemplateFunction::new(self_property, move |commit| {
                Ok(index.get(commit.id()).to_vec())
            });
            Ok(language.wrap_ref_name_list(out_property))
        },
    );
    map.insert(
        "git_head",
        |language, _build_ctx, self_property, function| {
            template_parser::expect_no_arguments(function)?;
            let repo = language.repo;
            let out_property =
                TemplateFunction::new(self_property, |commit| Ok(extract_git_head(repo, &commit)));
            Ok(language.wrap_ref_name_list(out_property))
        },
    );
    map.insert(
        "divergent",
        |language, _build_ctx, self_property, function| {
            template_parser::expect_no_arguments(function)?;
            let repo = language.repo;
            let out_property = TemplateFunction::new(self_property, |commit| {
                // The given commit could be hidden in e.g. obslog.
                let maybe_entries = repo.resolve_change_id(commit.change_id());
                Ok(maybe_entries.map_or(0, |entries| entries.len()) > 1)
            });
            Ok(language.wrap_boolean(out_property))
        },
    );
    map.insert("hidden", |language, _build_ctx, self_property, function| {
        template_parser::expect_no_arguments(function)?;
        let repo = language.repo;
        let out_property = TemplateFunction::new(self_property, |commit| {
            let maybe_entries = repo.resolve_change_id(commit.change_id());
            Ok(maybe_entries.map_or(true, |entries| !entries.contains(commit.id())))
        });
        Ok(language.wrap_boolean(out_property))
    });
    map.insert(
        "conflict",
        |language, _build_ctx, self_property, function| {
            template_parser::expect_no_arguments(function)?;
            let out_property =
                TemplateFunction::new(self_property, |commit| Ok(commit.has_conflict()?));
            Ok(language.wrap_boolean(out_property))
        },
    );
    map.insert("empty", |language, _build_ctx, self_property, function| {
        template_parser::expect_no_arguments(function)?;
        let repo = language.repo;
        let out_property = TemplateFunction::new(self_property, |commit| {
            if let [parent] = &commit.parents()[..] {
                return Ok(parent.tree_id() == commit.tree_id());
            }
            let parent_tree = rewrite::merge_commit_trees(repo, &commit.parents())?;
            Ok(*commit.tree_id() == parent_tree.id())
        });
        Ok(language.wrap_boolean(out_property))
    });
    map.insert("root", |language, _build_ctx, self_property, function| {
        template_parser::expect_no_arguments(function)?;
        let repo = language.repo;
        let out_property = TemplateFunction::new(self_property, |commit| {
            Ok(commit.id() == repo.store().root_commit_id())
        });
        Ok(language.wrap_boolean(out_property))
    });
    map
}

// TODO: return Vec<String>
fn extract_working_copies(repo: &dyn Repo, commit: &Commit) -> String {
    let wc_commit_ids = repo.view().wc_commit_ids();
    if wc_commit_ids.len() <= 1 {
        return "".to_string();
    }
    let mut names = vec![];
    for (workspace_id, wc_commit_id) in wc_commit_ids.iter().sorted() {
        if wc_commit_id == commit.id() {
            names.push(format!("{}@", workspace_id.as_str()));
        }
    }
    names.join(" ")
}

/// Branch or tag name with metadata.
#[derive(Clone, Debug, Eq, PartialEq)]
pub struct RefName {
    /// Local name.
    name: String,
    /// Remote name if this is a remote or Git-tracking ref.
    remote: Option<String>,
    /// Ref target has conflicts.
    conflict: bool,
    /// Local ref is synchronized with all tracking remotes, or tracking remote
    /// ref is synchronized with the local.
    synced: bool,
}

impl RefName {
    fn is_local(&self) -> bool {
        self.remote.is_none()
    }

    fn is_remote(&self) -> bool {
        self.remote.is_some()
    }
}

impl Template<()> for RefName {
    fn format(&self, _: &(), formatter: &mut dyn Formatter) -> io::Result<()> {
        write!(formatter.labeled("name"), "{}", self.name)?;
        if let Some(remote) = &self.remote {
            write!(formatter, "@")?;
            write!(formatter.labeled("remote"), "{remote}")?;
        }
        // Don't show both conflict and unsynced sigils as conflicted ref wouldn't
        // be pushed.
        if self.conflict {
            write!(formatter, "??")?;
        } else if self.is_local() && !self.synced {
            write!(formatter, "*")?;
        }
        Ok(())
    }
}

impl Template<()> for Vec<RefName> {
    fn format(&self, _: &(), formatter: &mut dyn Formatter) -> io::Result<()> {
        templater::format_joined(&(), formatter, self, " ")
    }
}

fn builtin_ref_name_methods<'repo>() -> CommitTemplateBuildMethodFnMap<'repo, RefName> {
    // Not using maplit::hashmap!{} or custom declarative macro here because
    // code completion inside macro is quite restricted.
    let mut map = CommitTemplateBuildMethodFnMap::<RefName>::new();
    map.insert("name", |language, _build_ctx, self_property, function| {
        template_parser::expect_no_arguments(function)?;
        let out_property = TemplateFunction::new(self_property, |ref_name| Ok(ref_name.name));
        Ok(language.wrap_string(out_property))
    });
    map.insert("remote", |language, _build_ctx, self_property, function| {
        template_parser::expect_no_arguments(function)?;
        let out_property = TemplateFunction::new(self_property, |ref_name| {
            Ok(ref_name.remote.unwrap_or_default())
        });
        Ok(language.wrap_string(out_property))
    });
    map
}

/// Cache for reverse lookup refs.
#[derive(Clone, Debug, Default)]
struct RefNamesIndex {
    index: HashMap<CommitId, Vec<RefName>>,
}

impl RefNamesIndex {
    fn insert<'a>(&mut self, ids: impl IntoIterator<Item = &'a CommitId>, name: RefName) {
        for id in ids {
            let ref_names = self.index.entry(id.clone()).or_default();
            ref_names.push(name.clone());
        }
    }

    fn get(&self, id: &CommitId) -> &[RefName] {
        if let Some(names) = self.index.get(id) {
            names
        } else {
            &[]
        }
    }
}

fn build_branches_index(repo: &dyn Repo) -> RefNamesIndex {
    let mut index = RefNamesIndex::default();
    for (branch_name, branch_target) in repo.view().branches() {
        let local_target = branch_target.local_target;
        let remote_refs = branch_target.remote_refs;
        if local_target.is_present() {
            let ref_name = RefName {
                name: branch_name.to_owned(),
                remote: None,
                conflict: local_target.has_conflict(),
                synced: remote_refs.iter().all(|&(_, remote_ref)| {
                    !remote_ref.is_tracking() || remote_ref.target == *local_target
                }),
            };
            index.insert(local_target.added_ids(), ref_name);
        }
        for &(remote_name, remote_ref) in &remote_refs {
            let ref_name = RefName {
                name: branch_name.to_owned(),
                remote: Some(remote_name.to_owned()),
                conflict: remote_ref.target.has_conflict(),
                synced: remote_ref.is_tracking() && remote_ref.target == *local_target,
            };
            index.insert(remote_ref.target.added_ids(), ref_name);
        }
    }
    index
}

fn build_ref_names_index<'a>(
    ref_pairs: impl IntoIterator<Item = (&'a String, &'a RefTarget)>,
) -> RefNamesIndex {
    let mut index = RefNamesIndex::default();
    for (name, target) in ref_pairs {
        let ref_name = RefName {
            name: name.to_owned(),
            remote: None,
            conflict: target.has_conflict(),
            synced: true, // has no tracking remotes
        };
        index.insert(target.added_ids(), ref_name);
    }
    index
}

// TODO: maybe add option or nullable type?
fn extract_git_head(repo: &dyn Repo, commit: &Commit) -> Vec<RefName> {
    let target = repo.view().git_head();
    if target.added_ids().contains(commit.id()) {
        let ref_name = RefName {
            name: "HEAD".to_owned(),
            remote: Some(git::REMOTE_NAME_FOR_LOCAL_GIT_REPO.to_owned()),
            conflict: target.has_conflict(),
            synced: false, // has no local counterpart
        };
        vec![ref_name]
    } else {
        vec![]
    }
}

#[derive(Clone, Debug, Eq, PartialEq)]
pub enum CommitOrChangeId {
    Commit(CommitId),
    Change(ChangeId),
}

impl CommitOrChangeId {
    pub fn hex(&self) -> String {
        match self {
            CommitOrChangeId::Commit(id) => id.hex(),
            CommitOrChangeId::Change(id) => {
                // TODO: We can avoid the unwrap() and make this more efficient by converting
                // straight from bytes.
                to_reverse_hex(&id.hex()).unwrap()
            }
        }
    }

    pub fn short(&self, total_len: usize) -> String {
        let mut hex = self.hex();
        hex.truncate(total_len);
        hex
    }

    /// The length of the id printed will be the maximum of `total_len` and the
    /// length of the shortest unique prefix
    pub fn shortest(
        &self,
        repo: &dyn Repo,
        id_prefix_context: &IdPrefixContext,
        total_len: usize,
    ) -> ShortestIdPrefix {
        let mut hex = self.hex();
        let prefix_len = match self {
            CommitOrChangeId::Commit(id) => id_prefix_context.shortest_commit_prefix_len(repo, id),
            CommitOrChangeId::Change(id) => id_prefix_context.shortest_change_prefix_len(repo, id),
        };
        hex.truncate(max(prefix_len, total_len));
        let rest = hex.split_off(prefix_len);
        ShortestIdPrefix { prefix: hex, rest }
    }
}

impl Template<()> for CommitOrChangeId {
    fn format(&self, _: &(), formatter: &mut dyn Formatter) -> io::Result<()> {
        formatter.write_str(&self.hex())
    }
}

fn builtin_commit_or_change_id_methods<'repo>(
) -> CommitTemplateBuildMethodFnMap<'repo, CommitOrChangeId> {
    // Not using maplit::hashmap!{} or custom declarative macro here because
    // code completion inside macro is quite restricted.
    let mut map = CommitTemplateBuildMethodFnMap::<CommitOrChangeId>::new();
    map.insert("short", |language, build_ctx, self_property, function| {
        let ([], [len_node]) = template_parser::expect_arguments(function)?;
        let len_property = len_node
            .map(|node| template_builder::expect_usize_expression(language, build_ctx, node))
            .transpose()?;
        let out_property = TemplateFunction::new((self_property, len_property), |(id, len)| {
            Ok(id.short(len.unwrap_or(12)))
        });
        Ok(language.wrap_string(out_property))
    });
    map.insert(
        "shortest",
        |language, build_ctx, self_property, function| {
            let id_prefix_context = &language.id_prefix_context;
            let ([], [len_node]) = template_parser::expect_arguments(function)?;
            let len_property = len_node
                .map(|node| template_builder::expect_usize_expression(language, build_ctx, node))
                .transpose()?;
            let out_property = TemplateFunction::new((self_property, len_property), |(id, len)| {
                Ok(id.shortest(language.repo, id_prefix_context, len.unwrap_or(0)))
            });
            Ok(language.wrap_shortest_id_prefix(out_property))
        },
    );
    map
}

pub struct ShortestIdPrefix {
    pub prefix: String,
    pub rest: String,
}

impl Template<()> for ShortestIdPrefix {
    fn format(&self, _: &(), formatter: &mut dyn Formatter) -> io::Result<()> {
        formatter.with_label("prefix", |fmt| fmt.write_str(&self.prefix))?;
        formatter.with_label("rest", |fmt| fmt.write_str(&self.rest))
    }
}

impl ShortestIdPrefix {
    fn to_upper(&self) -> Self {
        Self {
            prefix: self.prefix.to_ascii_uppercase(),
            rest: self.rest.to_ascii_uppercase(),
        }
    }
    fn to_lower(&self) -> Self {
        Self {
            prefix: self.prefix.to_ascii_lowercase(),
            rest: self.rest.to_ascii_lowercase(),
        }
    }
}

fn builtin_shortest_id_prefix_methods<'repo>(
) -> CommitTemplateBuildMethodFnMap<'repo, ShortestIdPrefix> {
    // Not using maplit::hashmap!{} or custom declarative macro here because
    // code completion inside macro is quite restricted.
    let mut map = CommitTemplateBuildMethodFnMap::<ShortestIdPrefix>::new();
    map.insert("prefix", |language, _build_ctx, self_property, function| {
        template_parser::expect_no_arguments(function)?;
        let out_property = TemplateFunction::new(self_property, |id| Ok(id.prefix));
        Ok(language.wrap_string(out_property))
    });
    map.insert("rest", |language, _build_ctx, self_property, function| {
        template_parser::expect_no_arguments(function)?;
        let out_property = TemplateFunction::new(self_property, |id| Ok(id.rest));
        Ok(language.wrap_string(out_property))
    });
    map.insert("upper", |language, _build_ctx, self_property, function| {
        template_parser::expect_no_arguments(function)?;
        let out_property = TemplateFunction::new(self_property, |id| Ok(id.to_upper()));
        Ok(language.wrap_shortest_id_prefix(out_property))
    });
    map.insert("lower", |language, _build_ctx, self_property, function| {
        template_parser::expect_no_arguments(function)?;
        let out_property = TemplateFunction::new(self_property, |id| Ok(id.to_lower()));
        Ok(language.wrap_shortest_id_prefix(out_property))
    });
    map
}

pub fn parse<'repo>(
    repo: &'repo dyn Repo,
    workspace_id: &WorkspaceId,
    id_prefix_context: &'repo IdPrefixContext,
    extension: Option<&dyn CommitTemplateLanguageExtension>,
    template_text: &str,
    aliases_map: &TemplateAliasesMap,
) -> TemplateParseResult<Box<dyn Template<Commit> + 'repo>> {
    let mut build_fn_table = CommitTemplateBuildFnTable::builtin();
    if let Some(extension) = extension {
        build_fn_table.merge(extension.build_fn_table());
    }

    let language = CommitTemplateLanguage {
        repo,
        workspace_id: workspace_id.clone(),
        id_prefix_context,
        build_fn_table,
        keyword_cache: CommitKeywordCache::default(),
    };
    let node = template_parser::parse(template_text, aliases_map)?;
    template_builder::build(&language, &node)
        .map_err(|err| err.extend_alias_candidates(aliases_map))
}