// Copyright 2021 Google LLC
//
// 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 jujutsu_lib::backend::CommitId;
use jujutsu_lib::commit::Commit;
use jujutsu_lib::commit_builder::CommitBuilder;
use jujutsu_lib::op_store::RefTarget;
use jujutsu_lib::repo_path::RepoPath;
use jujutsu_lib::rewrite::{update_branches_after_rewrite, DescendantRebaser, RebasedDescendant};
use jujutsu_lib::testutils;
use jujutsu_lib::testutils::CommitGraphBuilder;
use maplit::{hashmap, hashset};
use test_case::test_case;

fn assert_rebased(
    rebased: Option<RebasedDescendant>,
    expected_old_commit: &Commit,
    expected_new_parents: &[CommitId],
) -> Commit {
    if let Some(RebasedDescendant {
        old_commit,
        new_commit,
    }) = rebased
    {
        assert_eq!(old_commit, *expected_old_commit);
        assert_eq!(new_commit.change_id(), expected_old_commit.change_id());
        assert_eq!(&new_commit.parent_ids(), expected_new_parents);
        new_commit
    } else {
        panic!("expected rebased commit: {:?}", rebased);
    }
}

#[test_case(false ; "local backend")]
#[test_case(true ; "git backend")]
fn test_rebase_descendants_sideways(use_git: bool) {
    let settings = testutils::user_settings();
    let (_temp_dir, repo) = testutils::init_repo(&settings, use_git);

    // Commit 2 was replaced by commit 6. Commits 3-5 should be rebased.
    //
    // 6
    // | 4
    // | 3 5
    // | |/
    // | 2
    // |/
    // 1
    let mut tx = repo.start_transaction("test");
    let mut graph_builder = CommitGraphBuilder::new(&settings, tx.mut_repo());
    let commit1 = graph_builder.initial_commit();
    let commit2 = graph_builder.commit_with_parents(&[&commit1]);
    let commit3 = graph_builder.commit_with_parents(&[&commit2]);
    let commit4 = graph_builder.commit_with_parents(&[&commit3]);
    let commit5 = graph_builder.commit_with_parents(&[&commit2]);
    let commit6 = graph_builder.commit_with_parents(&[&commit1]);

    let mut rebaser = DescendantRebaser::new(
        &settings,
        tx.mut_repo(),
        hashmap! {
            commit2.id().clone() => commit6.id().clone()
        },
        hashset! {},
    );
    let new_commit3 = assert_rebased(rebaser.rebase_next(), &commit3, &[commit6.id().clone()]);
    assert_rebased(rebaser.rebase_next(), &commit4, &[new_commit3.id().clone()]);
    assert_rebased(rebaser.rebase_next(), &commit5, &[commit6.id().clone()]);
    assert!(rebaser.rebase_next().is_none());
    assert_eq!(rebaser.rebased().len(), 3);

    tx.discard();
}

#[test_case(false ; "local backend")]
#[test_case(true ; "git backend")]
fn test_rebase_descendants_forward(use_git: bool) {
    let settings = testutils::user_settings();
    let (_temp_dir, repo) = testutils::init_repo(&settings, use_git);

    // Commit 2 was replaced by commit 6. Commits 3 and 5 should be rebased onto 6.
    // Commit 4 does not get rebased because it's an ancestor of the
    // destination. Commit 7 does not get replaced because it's already in
    // place.
    //
    // 7
    // 6 5
    // |/
    // 4 3
    // |/
    // 2
    // 1
    let mut tx = repo.start_transaction("test");
    let mut graph_builder = CommitGraphBuilder::new(&settings, tx.mut_repo());
    let commit1 = graph_builder.initial_commit();
    let commit2 = graph_builder.commit_with_parents(&[&commit1]);
    let commit3 = graph_builder.commit_with_parents(&[&commit2]);
    let commit4 = graph_builder.commit_with_parents(&[&commit2]);
    let commit5 = graph_builder.commit_with_parents(&[&commit4]);
    let commit6 = graph_builder.commit_with_parents(&[&commit4]);
    let _commit7 = graph_builder.commit_with_parents(&[&commit6]);

    let mut rebaser = DescendantRebaser::new(
        &settings,
        tx.mut_repo(),
        hashmap! {
            commit2.id().clone() =>
            commit6.id().clone()
        },
        hashset! {},
    );
    assert_rebased(rebaser.rebase_next(), &commit3, &[commit6.id().clone()]);
    assert_rebased(rebaser.rebase_next(), &commit5, &[commit6.id().clone()]);
    assert!(rebaser.rebase_next().is_none());
    assert_eq!(rebaser.rebased().len(), 2);

    tx.discard();
}

#[test_case(false ; "local backend")]
#[test_case(true ; "git backend")]
fn test_rebase_descendants_backward(use_git: bool) {
    let settings = testutils::user_settings();
    let (_temp_dir, repo) = testutils::init_repo(&settings, use_git);

    // Commit 3 was replaced by commit 2. Commit 4 should be rebased.
    //
    // 4
    // 3
    // 2
    // 1
    let mut tx = repo.start_transaction("test");
    let mut graph_builder = CommitGraphBuilder::new(&settings, tx.mut_repo());
    let commit1 = graph_builder.initial_commit();
    let commit2 = graph_builder.commit_with_parents(&[&commit1]);
    let commit3 = graph_builder.commit_with_parents(&[&commit2]);
    let commit4 = graph_builder.commit_with_parents(&[&commit3]);

    let mut rebaser = DescendantRebaser::new(
        &settings,
        tx.mut_repo(),
        hashmap! {
            commit3.id().clone() => commit2.id().clone()
        },
        hashset! {},
    );
    assert_rebased(rebaser.rebase_next(), &commit4, &[commit2.id().clone()]);
    assert!(rebaser.rebase_next().is_none());
    assert_eq!(rebaser.rebased().len(), 1);

    tx.discard();
}

#[test_case(false ; "local backend")]
#[test_case(true ; "git backend")]
fn test_rebase_descendants_internal_merge(use_git: bool) {
    let settings = testutils::user_settings();
    let (_temp_dir, repo) = testutils::init_repo(&settings, use_git);

    // Commit 2 was replaced by commit 6. Commits 3-5 should be rebased.
    //
    // 6
    // | 5
    // | |\
    // | 3 4
    // | |/
    // | 2
    // |/
    // 1
    let mut tx = repo.start_transaction("test");
    let mut graph_builder = CommitGraphBuilder::new(&settings, tx.mut_repo());
    let commit1 = graph_builder.initial_commit();
    let commit2 = graph_builder.commit_with_parents(&[&commit1]);
    let commit3 = graph_builder.commit_with_parents(&[&commit2]);
    let commit4 = graph_builder.commit_with_parents(&[&commit2]);
    let commit5 = graph_builder.commit_with_parents(&[&commit3, &commit4]);
    let commit6 = graph_builder.commit_with_parents(&[&commit1]);

    let mut rebaser = DescendantRebaser::new(
        &settings,
        tx.mut_repo(),
        hashmap! {
            commit2.id().clone() => commit6.id().clone()
        },
        hashset! {},
    );
    let new_commit3 = assert_rebased(rebaser.rebase_next(), &commit3, &[commit6.id().clone()]);
    let new_commit4 = assert_rebased(rebaser.rebase_next(), &commit4, &[commit6.id().clone()]);
    assert_rebased(
        rebaser.rebase_next(),
        &commit5,
        &[new_commit3.id().clone(), new_commit4.id().clone()],
    );
    assert!(rebaser.rebase_next().is_none());
    assert_eq!(rebaser.rebased().len(), 3);

    tx.discard();
}

#[test_case(false ; "local backend")]
#[test_case(true ; "git backend")]
fn test_rebase_descendants_external_merge(use_git: bool) {
    let settings = testutils::user_settings();
    let (_temp_dir, repo) = testutils::init_repo(&settings, use_git);

    // Commit 3 was replaced by commit 6. Commits 5 should be rebased. The rebased
    // commit 5 should have 6 as first parent and commit 4 as second parent.
    //
    // 6
    // | 5
    // | |\
    // | 3 4
    // | |/
    // | 2
    // |/
    // 1
    let mut tx = repo.start_transaction("test");
    let mut graph_builder = CommitGraphBuilder::new(&settings, tx.mut_repo());
    let commit1 = graph_builder.initial_commit();
    let commit2 = graph_builder.commit_with_parents(&[&commit1]);
    let commit3 = graph_builder.commit_with_parents(&[&commit2]);
    let commit4 = graph_builder.commit_with_parents(&[&commit2]);
    let commit5 = graph_builder.commit_with_parents(&[&commit3, &commit4]);
    let commit6 = graph_builder.commit_with_parents(&[&commit1]);

    let mut rebaser = DescendantRebaser::new(
        &settings,
        tx.mut_repo(),
        hashmap! {
            commit3.id().clone() => commit6.id().clone()
        },
        hashset! {},
    );
    assert_rebased(
        rebaser.rebase_next(),
        &commit5,
        &[commit6.id().clone(), commit4.id().clone()],
    );
    assert!(rebaser.rebase_next().is_none());
    assert_eq!(rebaser.rebased().len(), 1);

    tx.discard();
}

#[test_case(false ; "local backend")]
#[test_case(true ; "git backend")]
fn test_rebase_descendants_abandon(use_git: bool) {
    let settings = testutils::user_settings();
    let (_temp_dir, repo) = testutils::init_repo(&settings, use_git);

    // Commit 2 and commit 5 were abandoned. Commit 3 and commit 4 should get
    // rebased onto commit 1. Commit 6 should get rebased onto the new commit 4.
    //
    // 6
    // 5
    // 4 3
    // |/
    // 2
    // 1
    let mut tx = repo.start_transaction("test");
    let mut graph_builder = CommitGraphBuilder::new(&settings, tx.mut_repo());
    let commit1 = graph_builder.initial_commit();
    let commit2 = graph_builder.commit_with_parents(&[&commit1]);
    let commit3 = graph_builder.commit_with_parents(&[&commit2]);
    let commit4 = graph_builder.commit_with_parents(&[&commit2]);
    let commit5 = graph_builder.commit_with_parents(&[&commit4]);
    let commit6 = graph_builder.commit_with_parents(&[&commit5]);

    let mut rebaser = DescendantRebaser::new(
        &settings,
        tx.mut_repo(),
        hashmap! {},
        hashset! {commit2.id().clone(), commit5.id().clone()},
    );
    assert_rebased(rebaser.rebase_next(), &commit3, &[commit1.id().clone()]);
    let new_commit4 = assert_rebased(rebaser.rebase_next(), &commit4, &[commit1.id().clone()]);
    assert_rebased(rebaser.rebase_next(), &commit6, &[new_commit4.id().clone()]);
    assert!(rebaser.rebase_next().is_none());
    assert_eq!(rebaser.rebased().len(), 3);

    tx.discard();
}

#[test_case(false ; "local backend")]
#[test_case(true ; "git backend")]
fn test_rebase_descendants_abandon_and_replace(use_git: bool) {
    let settings = testutils::user_settings();
    let (_temp_dir, repo) = testutils::init_repo(&settings, use_git);

    // Commit 2 was replaced by commit 5. Commit 3 was abandoned. Commit 4 should
    // get rebased onto commit 5.
    //
    //   4
    //   3
    // 5 2
    // |/
    // 1
    let mut tx = repo.start_transaction("test");
    let mut graph_builder = CommitGraphBuilder::new(&settings, tx.mut_repo());
    let commit1 = graph_builder.initial_commit();
    let commit2 = graph_builder.commit_with_parents(&[&commit1]);
    let commit3 = graph_builder.commit_with_parents(&[&commit2]);
    let commit4 = graph_builder.commit_with_parents(&[&commit3]);
    let commit5 = graph_builder.commit_with_parents(&[&commit1]);

    let mut rebaser = DescendantRebaser::new(
        &settings,
        tx.mut_repo(),
        hashmap! {commit2.id().clone() => commit5.id().clone()},
        hashset! {commit3.id().clone()},
    );
    assert_rebased(rebaser.rebase_next(), &commit4, &[commit5.id().clone()]);
    assert!(rebaser.rebase_next().is_none());
    assert_eq!(rebaser.rebased().len(), 1);

    tx.discard();
}

#[test_case(false ; "local backend")]
#[test_case(true ; "git backend")]
fn test_rebase_descendants_abandon_degenerate_merge(use_git: bool) {
    let settings = testutils::user_settings();
    let (_temp_dir, repo) = testutils::init_repo(&settings, use_git);

    // Commit 2 was abandoned. Commit 4 should get rebased to have only 3 as parent
    // (not 1 and 3).
    //
    // 4
    // |\
    // 2 3
    // |/
    // 1
    let mut tx = repo.start_transaction("test");
    let mut graph_builder = CommitGraphBuilder::new(&settings, tx.mut_repo());
    let commit1 = graph_builder.initial_commit();
    let commit2 = graph_builder.commit_with_parents(&[&commit1]);
    let commit3 = graph_builder.commit_with_parents(&[&commit1]);
    let commit4 = graph_builder.commit_with_parents(&[&commit2, &commit3]);

    let mut rebaser = DescendantRebaser::new(
        &settings,
        tx.mut_repo(),
        hashmap! {},
        hashset! {commit2.id().clone()},
    );
    assert_rebased(rebaser.rebase_next(), &commit4, &[commit3.id().clone()]);
    assert!(rebaser.rebase_next().is_none());
    assert_eq!(rebaser.rebased().len(), 1);

    tx.discard();
}

#[test_case(false ; "local backend")]
#[test_case(true ; "git backend")]
fn test_rebase_descendants_abandon_widen_merge(use_git: bool) {
    let settings = testutils::user_settings();
    let (_temp_dir, repo) = testutils::init_repo(&settings, use_git);

    // Commit 5 was abandoned. Commit 6 should get rebased to have 2, 3, and 4 as
    // parents (in that order).
    //
    // 6
    // |\
    // 5 \
    // |\ \
    // 2 3 4
    //  \|/
    //   1
    let mut tx = repo.start_transaction("test");
    let mut graph_builder = CommitGraphBuilder::new(&settings, tx.mut_repo());
    let commit1 = graph_builder.initial_commit();
    let commit2 = graph_builder.commit_with_parents(&[&commit1]);
    let commit3 = graph_builder.commit_with_parents(&[&commit1]);
    let commit4 = graph_builder.commit_with_parents(&[&commit1]);
    let commit5 = graph_builder.commit_with_parents(&[&commit2, &commit3]);
    let commit6 = graph_builder.commit_with_parents(&[&commit5, &commit4]);

    let mut rebaser = DescendantRebaser::new(
        &settings,
        tx.mut_repo(),
        hashmap! {},
        hashset! {commit5.id().clone()},
    );
    assert_rebased(
        rebaser.rebase_next(),
        &commit6,
        &[
            commit2.id().clone(),
            commit3.id().clone(),
            commit4.id().clone(),
        ],
    );
    assert!(rebaser.rebase_next().is_none());
    assert_eq!(rebaser.rebased().len(), 1);

    tx.discard();
}

#[test_case(false ; "local backend")]
#[test_case(true ; "git backend")]
fn test_rebase_descendants_multiple_sideways(use_git: bool) {
    let settings = testutils::user_settings();
    let (_temp_dir, repo) = testutils::init_repo(&settings, use_git);

    // Commit 2 and commit 4 were both replaced by commit 6. Commit 3 and commit 5
    // should get rebased onto it.
    //
    // 3 5
    // 2 4 6
    // | |/
    // |/
    // 1
    let mut tx = repo.start_transaction("test");
    let mut graph_builder = CommitGraphBuilder::new(&settings, tx.mut_repo());
    let commit1 = graph_builder.initial_commit();
    let commit2 = graph_builder.commit_with_parents(&[&commit1]);
    let commit3 = graph_builder.commit_with_parents(&[&commit2]);
    let commit4 = graph_builder.commit_with_parents(&[&commit1]);
    let commit5 = graph_builder.commit_with_parents(&[&commit4]);
    let commit6 = graph_builder.commit_with_parents(&[&commit1]);

    let mut rebaser = DescendantRebaser::new(
        &settings,
        tx.mut_repo(),
        hashmap! {
            commit2.id().clone() => commit6.id().clone(),
            commit4.id().clone() => commit6.id().clone(),
        },
        hashset! {},
    );
    assert_rebased(rebaser.rebase_next(), &commit3, &[commit6.id().clone()]);
    assert_rebased(rebaser.rebase_next(), &commit5, &[commit6.id().clone()]);
    assert!(rebaser.rebase_next().is_none());
    assert_eq!(rebaser.rebased().len(), 2);

    tx.discard();
}

#[test_case(false ; "local backend")]
#[test_case(true ; "git backend")]
fn test_rebase_descendants_multiple_swap(use_git: bool) {
    let settings = testutils::user_settings();
    let (_temp_dir, repo) = testutils::init_repo(&settings, use_git);

    // Commit 2 was replaced by commit 4 and commit 4 was replaced by commit 2.
    // Commit 3 and commit 5 should swap places.
    //
    // 3 5
    // 2 4
    // |/
    // 1
    let mut tx = repo.start_transaction("test");
    let mut graph_builder = CommitGraphBuilder::new(&settings, tx.mut_repo());
    let commit1 = graph_builder.initial_commit();
    let commit2 = graph_builder.commit_with_parents(&[&commit1]);
    let commit3 = graph_builder.commit_with_parents(&[&commit2]);
    let commit4 = graph_builder.commit_with_parents(&[&commit1]);
    let commit5 = graph_builder.commit_with_parents(&[&commit4]);

    let mut rebaser = DescendantRebaser::new(
        &settings,
        tx.mut_repo(),
        hashmap! {
            commit2.id().clone() => commit4.id().clone(),
            commit4.id().clone() => commit2.id().clone(),
        },
        hashset! {},
    );
    assert_rebased(rebaser.rebase_next(), &commit3, &[commit4.id().clone()]);
    assert_rebased(rebaser.rebase_next(), &commit5, &[commit2.id().clone()]);
    assert!(rebaser.rebase_next().is_none());
    assert_eq!(rebaser.rebased().len(), 2);

    tx.discard();
}

#[test_case(false ; "local backend")]
#[test_case(true ; "git backend")]
fn test_rebase_descendants_multiple_forward_and_backward(use_git: bool) {
    let settings = testutils::user_settings();
    let (_temp_dir, repo) = testutils::init_repo(&settings, use_git);

    // Commit 2 was replaced by commit 4 and commit 6 was replaced by commit 3.
    // Commit 7 should be rebased onto commit 3. Commit 8 should be rebased onto
    // commit 4. Commits 3-4 should be left alone since they're ancestors of 4.
    // Commit 5 should be left alone since its already in place (as a descendant of
    // 4).
    //
    // 7
    // 6
    // 5
    // 4
    // 3 8
    // |/
    // 2
    // 1
    let mut tx = repo.start_transaction("test");
    let mut graph_builder = CommitGraphBuilder::new(&settings, tx.mut_repo());
    let commit1 = graph_builder.initial_commit();
    let commit2 = graph_builder.commit_with_parents(&[&commit1]);
    let commit3 = graph_builder.commit_with_parents(&[&commit2]);
    let commit4 = graph_builder.commit_with_parents(&[&commit3]);
    let commit5 = graph_builder.commit_with_parents(&[&commit4]);
    let commit6 = graph_builder.commit_with_parents(&[&commit5]);
    let commit7 = graph_builder.commit_with_parents(&[&commit6]);
    let commit8 = graph_builder.commit_with_parents(&[&commit2]);

    let mut rebaser = DescendantRebaser::new(
        &settings,
        tx.mut_repo(),
        hashmap! {
            commit2.id().clone() => commit4.id().clone(),
            commit6.id().clone() => commit3.id().clone(),
        },
        hashset! {},
    );
    assert_rebased(rebaser.rebase_next(), &commit7, &[commit3.id().clone()]);
    assert_rebased(rebaser.rebase_next(), &commit8, &[commit4.id().clone()]);
    assert!(rebaser.rebase_next().is_none());
    assert_eq!(rebaser.rebased().len(), 2);

    tx.discard();
}

#[test_case(false ; "local backend")]
#[test_case(true ; "git backend")]
fn test_rebase_descendants_contents(use_git: bool) {
    let settings = testutils::user_settings();
    let (_temp_dir, repo) = testutils::init_repo(&settings, use_git);

    // Commit 2 was replaced by commit 4. Commit 3 should have the changes from
    // commit 3 and commit 4, but not the changes from commit 2.
    //
    // 4
    // | 3
    // | 2
    // |/
    // 1
    let mut tx = repo.start_transaction("test");
    let path1 = RepoPath::from_internal_string("file1");
    let tree1 = testutils::create_tree(&repo, &[(&path1, "content")]);
    let commit1 = CommitBuilder::for_new_commit(&settings, repo.store(), tree1.id().clone())
        .write_to_repo(tx.mut_repo());
    let path2 = RepoPath::from_internal_string("file2");
    let tree2 = testutils::create_tree(&repo, &[(&path2, "content")]);
    let commit2 = CommitBuilder::for_new_commit(&settings, repo.store(), tree2.id().clone())
        .set_parents(vec![commit1.id().clone()])
        .write_to_repo(tx.mut_repo());
    let path3 = RepoPath::from_internal_string("file3");
    let tree3 = testutils::create_tree(&repo, &[(&path3, "content")]);
    let commit3 = CommitBuilder::for_new_commit(&settings, repo.store(), tree3.id().clone())
        .set_parents(vec![commit2.id().clone()])
        .write_to_repo(tx.mut_repo());
    let path4 = RepoPath::from_internal_string("file4");
    let tree4 = testutils::create_tree(&repo, &[(&path4, "content")]);
    let commit4 = CommitBuilder::for_new_commit(&settings, repo.store(), tree4.id().clone())
        .set_parents(vec![commit1.id().clone()])
        .write_to_repo(tx.mut_repo());

    let mut rebaser = DescendantRebaser::new(
        &settings,
        tx.mut_repo(),
        hashmap! {
            commit2.id().clone() => commit4.id().clone()
        },
        hashset! {},
    );
    rebaser.rebase_all();
    let rebased = rebaser.rebased();
    assert_eq!(rebased.len(), 1);
    let new_commit3 = repo
        .store()
        .get_commit(rebased.get(commit3.id()).unwrap())
        .unwrap();

    assert_eq!(
        new_commit3.tree().path_value(&path3),
        commit3.tree().path_value(&path3)
    );
    assert_eq!(
        new_commit3.tree().path_value(&path4),
        commit4.tree().path_value(&path4)
    );
    assert_ne!(
        new_commit3.tree().path_value(&path2),
        commit2.tree().path_value(&path2)
    );

    tx.discard();
}

#[test]
fn test_update_branches_after_rewrite_basic() {
    let settings = testutils::user_settings();
    let (_temp_dir, repo) = testutils::init_repo(&settings, false);

    // Branch "main" points to branch B. B gets rewritten as B2. Branch main should
    // be updated to point to B2.
    //
    // B main         B2 main
    // |         =>   |
    // A              A
    let mut tx = repo.start_transaction("test");
    let mut graph_builder = CommitGraphBuilder::new(&settings, tx.mut_repo());
    let commit_a = graph_builder.initial_commit();
    let commit_b = graph_builder.commit_with_parents(&[&commit_a]);
    tx.mut_repo()
        .set_local_branch("main".to_string(), RefTarget::Normal(commit_b.id().clone()));
    tx.mut_repo().set_remote_branch(
        "main".to_string(),
        "origin".to_string(),
        RefTarget::Normal(commit_b.id().clone()),
    );
    tx.mut_repo()
        .set_tag("v1".to_string(), RefTarget::Normal(commit_b.id().clone()));
    let repo = tx.commit();

    let mut tx = repo.start_transaction("test");
    let commit_b2 = CommitBuilder::for_rewrite_from(&settings, repo.store(), &commit_b)
        .write_to_repo(tx.mut_repo());
    update_branches_after_rewrite(tx.mut_repo());
    assert_eq!(
        tx.mut_repo().get_local_branch("main"),
        Some(RefTarget::Normal(commit_b2.id().clone()))
    );
    // The remote branch and tag should not get updated
    assert_eq!(
        tx.mut_repo().get_remote_branch("main", "origin"),
        Some(RefTarget::Normal(commit_b.id().clone()))
    );
    assert_eq!(
        tx.mut_repo().get_tag("v1"),
        Some(RefTarget::Normal(commit_b.id().clone()))
    );

    tx.discard();
}

#[test]
fn test_update_branches_after_rewrite_to_conflict() {
    let settings = testutils::user_settings();
    let (_temp_dir, repo) = testutils::init_repo(&settings, false);

    // Branch "main" points to commit B. B gets rewritten as B2, B3, B4. Branch main
    // should become a conflict pointing to all of them.
    //
    //                B4 main?
    //                | B3 main?
    // B main         |/B2 main?
    // |         =>   |/
    // A              A
    let mut tx = repo.start_transaction("test");
    let mut graph_builder = CommitGraphBuilder::new(&settings, tx.mut_repo());
    let commit_a = graph_builder.initial_commit();
    let commit_b = graph_builder.commit_with_parents(&[&commit_a]);
    tx.mut_repo()
        .set_local_branch("main".to_string(), RefTarget::Normal(commit_b.id().clone()));
    let repo = tx.commit();

    let mut tx = repo.start_transaction("test");
    let commit_b2 = CommitBuilder::for_rewrite_from(&settings, repo.store(), &commit_b)
        .write_to_repo(tx.mut_repo());
    // Different description so they're not the same commit
    let commit_b3 = CommitBuilder::for_rewrite_from(&settings, repo.store(), &commit_b)
        .set_description("different".to_string())
        .write_to_repo(tx.mut_repo());
    // Different description so they're not the same commit
    let commit_b4 = CommitBuilder::for_rewrite_from(&settings, repo.store(), &commit_b)
        .set_description("more different".to_string())
        .write_to_repo(tx.mut_repo());
    update_branches_after_rewrite(tx.mut_repo());
    assert_eq!(
        tx.mut_repo().get_local_branch("main"),
        Some(RefTarget::Conflict {
            removes: vec![commit_b.id().clone(), commit_b.id().clone()],
            adds: vec![
                commit_b2.id().clone(),
                commit_b3.id().clone(),
                commit_b4.id().clone()
            ]
        })
    );

    tx.discard();
}

#[test]
fn test_update_branches_after_rewrite_update_conflict() {
    let settings = testutils::user_settings();
    let (_temp_dir, repo) = testutils::init_repo(&settings, false);

    // Branch "main" is a conflict removing commit A and adding commit B and C.
    // A gets rewritten as A2 and A3. B gets rewritten as B2 and B2. The branch
    // should become a conflict removing A2, A3, and B, and adding A, B2, B3, C.
    let mut tx = repo.start_transaction("test");
    let mut graph_builder = CommitGraphBuilder::new(&settings, tx.mut_repo());
    let commit_a = graph_builder.initial_commit();
    let commit_b = graph_builder.initial_commit();
    let commit_c = graph_builder.initial_commit();
    tx.mut_repo().set_local_branch(
        "main".to_string(),
        RefTarget::Conflict {
            removes: vec![commit_a.id().clone()],
            adds: vec![commit_b.id().clone(), commit_c.id().clone()],
        },
    );
    let repo = tx.commit();

    let mut tx = repo.start_transaction("test");
    let commit_a2 = CommitBuilder::for_rewrite_from(&settings, repo.store(), &commit_a)
        .write_to_repo(tx.mut_repo());
    // Different description so they're not the same commit
    let commit_a3 = CommitBuilder::for_rewrite_from(&settings, repo.store(), &commit_a)
        .set_description("different".to_string())
        .write_to_repo(tx.mut_repo());
    let commit_b2 = CommitBuilder::for_rewrite_from(&settings, repo.store(), &commit_b)
        .write_to_repo(tx.mut_repo());
    // Different description so they're not the same commit
    let commit_b3 = CommitBuilder::for_rewrite_from(&settings, repo.store(), &commit_b)
        .set_description("different".to_string())
        .write_to_repo(tx.mut_repo());
    update_branches_after_rewrite(tx.mut_repo());
    assert_eq!(
        tx.mut_repo().get_local_branch("main"),
        Some(RefTarget::Conflict {
            removes: vec![
                commit_b.id().clone(),
                commit_a2.id().clone(),
                commit_a3.id().clone()
            ],
            adds: vec![
                commit_c.id().clone(),
                commit_b2.id().clone(),
                commit_b3.id().clone(),
                commit_a.id().clone()
            ]
        })
    );

    tx.discard();
}

#[test]
fn test_update_branches_after_rewrite_resolves_conflict() {
    let settings = testutils::user_settings();
    let (_temp_dir, repo) = testutils::init_repo(&settings, false);

    // Branch "main" is a conflict removing ancestor commit A and adding commit B
    // and C (maybe it moved forward to B locally and moved forward to C
    // remotely). Now B gets rewritten as B2, which is a descendant of C (maybe
    // B was automatically rebased on top of the updated remote). That
    // would result in a conflict removing A and adding B2 and C. However, since C
    // is a descendant of A, and B2 is a descendant of C, the conflict gets
    // resolved to B2.
    let mut tx = repo.start_transaction("test");
    let mut graph_builder = CommitGraphBuilder::new(&settings, tx.mut_repo());
    let commit_a = graph_builder.initial_commit();
    let commit_b = graph_builder.commit_with_parents(&[&commit_a]);
    let commit_c = graph_builder.commit_with_parents(&[&commit_a]);
    tx.mut_repo().set_local_branch(
        "main".to_string(),
        RefTarget::Conflict {
            removes: vec![commit_a.id().clone()],
            adds: vec![commit_b.id().clone(), commit_c.id().clone()],
        },
    );
    let repo = tx.commit();

    let mut tx = repo.start_transaction("test");
    let commit_b2 = CommitBuilder::for_rewrite_from(&settings, repo.store(), &commit_b)
        .set_parents(vec![commit_c.id().clone()])
        .write_to_repo(tx.mut_repo());
    update_branches_after_rewrite(tx.mut_repo());
    assert_eq!(
        tx.mut_repo().get_local_branch("main"),
        Some(RefTarget::Normal(commit_b2.id().clone()))
    );

    tx.discard();
}

// TODO: Add a test for the following case, which can't happen with our current
// evolution-based rewriting.
//
// 1. Operation 1 points a branch to commit A
// 2. Operation 2 repoints the branch to commit B
// 3. Operation 3, which is concurrent with operation 2, deletes the branch
// 4. Resolved state (operation 4) will have a "-A+B" state for the branch
//
// Now we hide B and make A visible instead. When that diff is applied to the
// branch, the branch state becomes empty and is thus deleted.