// Copyright 2020 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 std::collections::HashSet;
use std::path::PathBuf;

use tempfile::TempDir;

use jujube_lib::repo::{ReadonlyRepo, Repo};
use jujube_lib::testutils;
use std::sync::Arc;
use test_case::test_case;

fn copy_directory(src: &PathBuf, dst: &PathBuf) {
    std::fs::create_dir(dst).ok();
    for entry in std::fs::read_dir(src).unwrap() {
        let child_src = entry.unwrap().path();
        let base_name = child_src.file_name().unwrap();
        let child_dst = dst.join(base_name);
        if child_src.is_dir() {
            copy_directory(&child_src, &child_dst)
        } else {
            std::fs::copy(&child_src, &child_dst).unwrap();
        }
    }
}

fn merge_directories(left: &PathBuf, base: &PathBuf, right: &PathBuf, output: &PathBuf) {
    std::fs::create_dir(output).ok();
    let mut sub_dirs = vec![];
    // Walk the left side and copy to the output
    for entry in std::fs::read_dir(left).unwrap() {
        let path = entry.unwrap().path();
        let base_name = path.file_name().unwrap();
        let child_left = left.join(base_name);
        let child_output = output.join(base_name);
        if child_left.is_dir() {
            sub_dirs.push(base_name.to_os_string());
        } else {
            std::fs::copy(&child_left, &child_output).unwrap();
        }
    }
    // Walk the base and find files removed in the right side, then remove them in
    // the output
    for entry in std::fs::read_dir(base).unwrap() {
        let path = entry.unwrap().path();
        let base_name = path.file_name().unwrap();
        let child_base = base.join(base_name);
        let child_right = right.join(base_name);
        let child_output = output.join(base_name);
        if child_base.is_dir() {
            sub_dirs.push(base_name.to_os_string());
        } else if !child_right.exists() {
            std::fs::remove_file(child_output).ok();
        }
    }
    // Walk the right side and find files added in the right side, then add them in
    // the output
    for entry in std::fs::read_dir(right).unwrap() {
        let path = entry.unwrap().path();
        let base_name = path.file_name().unwrap();
        let child_base = base.join(base_name);
        let child_right = right.join(base_name);
        let child_output = output.join(base_name);
        if child_right.is_dir() {
            sub_dirs.push(base_name.to_os_string());
        } else if !child_base.exists() {
            // This overwrites the left side if that's been written. That's fine, since the
            // point of the test is that it should be okay for either side to win.
            std::fs::copy(&child_right, &child_output).unwrap();
        }
    }
    // Do the merge in subdirectories
    for base_name in sub_dirs {
        let child_base = base.join(&base_name);
        let child_right = right.join(&base_name);
        let child_left = left.join(&base_name);
        let child_output = output.join(&base_name);
        merge_directories(&child_left, &child_base, &child_right, &child_output);
    }
}

#[test_case(false ; "local store")]
#[test_case(true ; "git store")]
fn test_bad_locking_children(use_git: bool) {
    // Test that two new commits created on separate machines are both visible (not
    // lost due to lack of locking)
    let settings = testutils::user_settings();
    let (_temp_dir, repo) = testutils::init_repo(&settings, use_git);

    let initial = testutils::create_random_commit(&settings, &repo)
        .set_parents(vec![repo.store().root_commit_id().clone()])
        .write_to_new_transaction(&repo, "test");

    // Simulate a write of a commit that happens on one machine
    let machine1_path = TempDir::new().unwrap().into_path();
    copy_directory(repo.working_copy_path(), &machine1_path);
    let machine1_repo = ReadonlyRepo::load(&settings, machine1_path);
    let child1 = testutils::create_random_commit(&settings, &machine1_repo)
        .set_parents(vec![initial.id().clone()])
        .write_to_new_transaction(&machine1_repo, "test");

    // Simulate a write of a commit that happens on another machine
    let machine2_path = TempDir::new().unwrap().into_path();
    copy_directory(repo.working_copy_path(), &machine2_path);
    let machine2_repo = ReadonlyRepo::load(&settings, machine2_path);
    let child2 = testutils::create_random_commit(&settings, &machine2_repo)
        .set_parents(vec![initial.id().clone()])
        .write_to_new_transaction(&machine2_repo, "test");

    // Simulate that the distributed file system now has received the changes from
    // both machines
    let merged_path = TempDir::new().unwrap().into_path();
    merge_directories(
        machine1_repo.working_copy_path(),
        repo.working_copy_path(),
        machine2_repo.working_copy_path(),
        &merged_path,
    );
    let merged_repo = ReadonlyRepo::load(&settings, merged_path);
    let heads: HashSet<_> = merged_repo.view().heads().cloned().collect();
    assert!(heads.contains(child1.id()));
    assert!(heads.contains(child2.id()));
    let op_head_id = merged_repo.view().base_op_head_id().clone();
    let op_head = merged_repo
        .view()
        .op_store()
        .read_operation(&op_head_id)
        .unwrap();
    assert_eq!(op_head.parents.len(), 2);
}

#[test_case(false ; "local store")]
#[test_case(true ; "git store")]
fn test_bad_locking_interrupted(use_git: bool) {
    // Test that an interrupted update of the op-heads resulting in on op-head
    // that's a descendant of the other is resolved without creating a new
    // operation.
    let settings = testutils::user_settings();
    let (_temp_dir, mut repo) = testutils::init_repo(&settings, use_git);

    let initial = testutils::create_random_commit(&settings, &repo)
        .set_parents(vec![repo.store().root_commit_id().clone()])
        .write_to_new_transaction(&repo, "test");
    Arc::get_mut(&mut repo).unwrap().reload();

    // Simulate a crash that resulted in the old op-head left in place. We simulate
    // it somewhat hackily by copying the view/op_heads/ directory before the
    // operation and then copying that back afterwards, leaving the existing
    // op-head(s) in place.
    let op_heads_dir = repo.repo_path().join("view").join("op_heads");
    let backup_path = TempDir::new().unwrap().into_path();
    copy_directory(&op_heads_dir, &backup_path);
    let mut tx = repo.start_transaction("test");
    testutils::create_random_commit(&settings, &repo)
        .set_parents(vec![initial.id().clone()])
        .write_to_transaction(&mut tx);
    let op_head_id = tx.commit().id().clone();

    copy_directory(&backup_path, &op_heads_dir);
    // Reload the repo and check that only the new head is present.
    let reloaded_repo = ReadonlyRepo::load(&settings, repo.working_copy_path().clone());
    assert_eq!(reloaded_repo.view().base_op_head_id(), &op_head_id);
    // Reload once more to make sure that the view/op_heads/ directory was updated
    // correctly.
    let reloaded_repo = ReadonlyRepo::load(&settings, repo.working_copy_path().clone());
    assert_eq!(reloaded_repo.view().base_op_head_id(), &op_head_id);
}