// 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.

use std::cmp::max;
use std::thread;

use jujutsu_lib::dag_walk;
use jujutsu_lib::repo::{ReadonlyRepo, StoreFactories};
use test_case::test_case;
use testutils::{write_random_commit, TestWorkspace};

fn count_non_merge_operations(repo: &ReadonlyRepo) -> usize {
    let op_store = repo.op_store();
    let op_id = repo.op_id().clone();
    let mut num_ops = 0;

    for op_id in dag_walk::bfs(
        vec![op_id],
        Box::new(|op_id| op_id.clone()),
        Box::new(|op_id| op_store.read_operation(op_id).unwrap().parents),
    ) {
        if op_store.read_operation(&op_id).unwrap().parents.len() <= 1 {
            num_ops += 1;
        }
    }
    num_ops
}

#[test_case(false ; "local backend")]
#[test_case(true ; "git backend")]
fn test_commit_parallel(use_git: bool) {
    // This loads a Repo instance and creates and commits many concurrent
    // transactions from it. It then reloads the repo. That should merge all the
    // operations and all commits should be visible.
    let settings = testutils::user_settings();
    let test_workspace = TestWorkspace::init(&settings, use_git);
    let repo = &test_workspace.repo;

    let num_threads = max(num_cpus::get(), 4);
    let mut threads = vec![];
    for _ in 0..num_threads {
        let settings = settings.clone();
        let repo = repo.clone();
        let handle = thread::spawn(move || {
            let mut tx = repo.start_transaction(&settings, "test");
            write_random_commit(tx.mut_repo(), &settings);
            tx.commit();
        });
        threads.push(handle);
    }
    for thread in threads {
        thread.join().ok().unwrap();
    }
    let repo = repo.reload_at_head(&settings).unwrap();
    // One commit per thread plus the commit from the initial working-copy on top of
    // the root commit
    assert_eq!(repo.view().heads().len(), num_threads + 1);

    // One additional operation for initializing the repo, one for checking out the
    // initial commit.
    assert_eq!(count_non_merge_operations(&repo), num_threads + 2);
}

#[test_case(false ; "local backend")]
#[test_case(true ; "git backend")]
fn test_commit_parallel_instances(use_git: bool) {
    // Like the test above but creates a new repo instance for every thread, which
    // makes it behave very similar to separate processes.
    let settings = testutils::user_settings();
    let test_workspace = TestWorkspace::init(&settings, use_git);
    let repo = &test_workspace.repo;

    let num_threads = max(num_cpus::get(), 4);
    let mut threads = vec![];
    for _ in 0..num_threads {
        let settings = settings.clone();
        let repo =
            ReadonlyRepo::load_at_head(&settings, repo.repo_path(), &StoreFactories::default())
                .unwrap();
        let handle = thread::spawn(move || {
            let mut tx = repo.start_transaction(&settings, "test");
            write_random_commit(tx.mut_repo(), &settings);
            tx.commit();
        });
        threads.push(handle);
    }
    for thread in threads {
        thread.join().ok().unwrap();
    }
    // One commit per thread plus the commit from the initial working-copy commit on
    // top of the root commit
    let repo = ReadonlyRepo::load_at_head(&settings, repo.repo_path(), &StoreFactories::default())
        .unwrap();
    assert_eq!(repo.view().heads().len(), num_threads + 1);

    // One addition operation for initializing the repo, one for checking out the
    // initial commit.
    assert_eq!(count_non_merge_operations(&repo), num_threads + 2);
}