/*
 * This file is open source software, licensed to you under the terms
 * of the Apache License, Version 2.0 (the "License").  See the NOTICE file
 * distributed with this work for additional information regarding copyright
 * ownership.  You may not use this file except in compliance with the License.
 *
 * You may obtain a copy of the License at
 *
 *   http://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.
 */

/*
 * Copyright 2020 ScyllaDB
 */

#include <iostream>
#include <list>
#include <deque>

#include <seastar/core/reactor.hh>
#include <seastar/core/seastar.hh>
#include <seastar/util/file.hh>

namespace seastar {

namespace fs = std::filesystem;

future<> make_directory(std::string_view name, file_permissions permissions) noexcept {
    return engine().make_directory(name, permissions);
}

future<> touch_directory(std::string_view name, file_permissions permissions) noexcept {
    return engine().touch_directory(name, permissions);
}

future<> sync_directory(std::string_view name) noexcept {
    return open_directory(name).then([] (file f) {
        return do_with(std::move(f), [] (file& f) {
            return f.flush().then([&f] () mutable {
                return f.close();
            });
        });
    });
}

static future<> do_recursive_touch_directory(std::string_view base_view, std::string_view name, file_permissions permissions) {
    sstring base(base_view);
    static const sstring::value_type separator = '/';

    if (name.empty()) {
        return make_ready_future<>();
    }

    size_t pos = std::min(name.find(separator), name.size() - 1);
    base += sstring(name.substr(0 , pos + 1));
    name = name.substr(pos + 1);
    if (name.length() == 1 && name[0] == separator) {
        name = {};
    }
    // use the optional permissions only for last component,
    // other directories in the patch will always be created using the default_dir_permissions
    auto f = name.empty() ? touch_directory(base, permissions) : touch_directory(base);
    return f.then([base, name = sstring(name), permissions] {
        return do_recursive_touch_directory(base, std::move(name), permissions);
    }).then([base] {
        // We will now flush the directory that holds the entry we potentially
        // created. Technically speaking, we only need to touch when we did
        // create. But flushing the unchanged ones should be cheap enough - and
        // it simplifies the code considerably.
        if (base.empty()) {
            return make_ready_future<>();
        }

        return sync_directory(base);
    });
}

future<> recursive_touch_directory(std::string_view name, file_permissions permissions) noexcept {
    // If the name is empty,  it will be of the type a/b/c, which should be interpreted as
    // a relative path. This means we have to flush our current directory
    std::string_view base = "";
    if (name[0] != '/' || name[0] == '.') {
        base = "./";
    }
    return futurize_invoke(do_recursive_touch_directory, base, name, permissions);
}

future<> remove_file(std::string_view pathname) noexcept {
    return engine().remove_file(pathname);
}

future<> rename_file(std::string_view old_pathname, std::string_view new_pathname) noexcept {
    return engine().rename_file(old_pathname, new_pathname);
}

future<fs_type> file_system_at(std::string_view name) noexcept {
    return engine().file_system_at(name);
}

future<uint64_t> fs_avail(std::string_view name) noexcept {
    return engine().statvfs(name).then([] (struct statvfs st) {
        return make_ready_future<uint64_t>(st.f_bavail * st.f_frsize);
    });
}

future<uint64_t> fs_free(std::string_view name) noexcept {
    return engine().statvfs(name).then([] (struct statvfs st) {
        return make_ready_future<uint64_t>(st.f_bfree * st.f_frsize);
    });
}

future<stat_data> file_stat(std::string_view name, follow_symlink follow) noexcept {
    return engine().file_stat(name, follow);
}

future<uint64_t> file_size(std::string_view name) noexcept {
    return engine().file_size(name);
}

future<bool> file_accessible(std::string_view name, access_flags flags) noexcept {
    return engine().file_accessible(name, flags);
}

future<bool> file_exists(std::string_view name) noexcept {
    return engine().file_exists(name);
}

future<> link_file(std::string_view oldpath, std::string_view newpath) noexcept {
    return engine().link_file(oldpath, newpath);
}

future<> chmod(std::string_view name, file_permissions permissions) noexcept {
    return engine().chmod(name, permissions);
}

static future<> do_recursive_remove_directory(const fs::path path) noexcept {
    struct work_entry {
        const fs::path path;
        bool listed;

        work_entry(const fs::path path, bool listed)
                : path(std::move(path))
                , listed(listed)
        {
        }
    };

    return do_with(std::deque<work_entry>(), [path = std::move(path)] (auto& work_queue) mutable {
        work_queue.emplace_back(std::move(path), false);
        return do_until([&work_queue] { return work_queue.empty(); }, [&work_queue] () mutable {
            auto ent = work_queue.back();
            work_queue.pop_back();
            if (ent.listed) {
                return remove_file(ent.path.native());
            } else {
                work_queue.emplace_back(ent.path, true);
                return do_with(std::move(ent.path), [&work_queue] (const fs::path& path) {
                    return open_directory(path.native()).then([&path, &work_queue] (file dir) mutable {
                        return do_with(std::move(dir), [&path, &work_queue] (file& dir) mutable {
                            return dir.list_directory([&path, &work_queue] (directory_entry de) mutable {
                                const fs::path sub_path = path / de.name.c_str();
                                if (de.type && *de.type == directory_entry_type::directory) {
                                    work_queue.emplace_back(std::move(sub_path), false);
                                } else {
                                    work_queue.emplace_back(std::move(sub_path), true);
                                }
                                return make_ready_future<>();
                            }).done().then([&dir] () mutable {
                                return dir.close();
                            });
                        });
                    });
                });
            }
        });
    });
}

future<> recursive_remove_directory(fs::path path) noexcept {
    sstring parent;
    try {
        parent = (path / "..").native();
    } catch (...) {
        return current_exception_as_future();
    }
    return open_directory(std::move(parent)).then([path = std::move(path)] (file parent) mutable {
        return do_with(std::move(parent), [path = std::move(path)] (file& parent) mutable {
            return do_recursive_remove_directory(std::move(path)).then([&parent] {
                return parent.flush().then([&parent] () mutable {
                    return parent.close();
                });
            });
        });
    });
}

namespace util {

future<std::vector<temporary_buffer<char>>> read_entire_file(std::filesystem::path path) {
    return with_file_input_stream(path, [] (input_stream<char>& in) {
        return read_entire_stream(in);
    });
}

future<sstring> read_entire_file_contiguous(std::filesystem::path path) {
    return with_file_input_stream(path, [] (input_stream<char>& in) {
        return read_entire_stream_contiguous(in);
    });
}

} // namespace util

} //namespace seastar
