/*
 * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this
 *    list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#pragma once

// Device is the base class of everything that lives in the /dev directory.
//
// To expose a Device to the filesystem, simply pass two unique numbers to the constructor,
// and then mknod a file in /dev with those numbers.
//
// There are two main subclasses:
//   - BlockDevice (random access)
//   - CharacterDevice (sequential)
#include <AK/DoublyLinkedList.h>
#include <AK/Function.h>
#include <AK/HashMap.h>
#include <Kernel/Devices/AsyncDeviceRequest.h>
#include <Kernel/FileSystem/File.h>
#include <Kernel/Lock.h>
#include <Kernel/UnixTypes.h>

namespace Kernel {

class Device : public File {
public:
    virtual ~Device() override;

    unsigned major() const { return m_major; }
    unsigned minor() const { return m_minor; }

    virtual String absolute_path(const FileDescription&) const override;
    virtual String absolute_path() const;

    uid_t uid() const { return m_uid; }
    uid_t gid() const { return m_gid; }

    virtual mode_t required_mode() const = 0;

    virtual bool is_device() const override { return true; }
    virtual bool is_disk_device() const { return false; }

    static void for_each(Function<void(Device&)>);
    static Device* get_device(unsigned major, unsigned minor);

    void process_next_queued_request(Badge<AsyncDeviceRequest>, const AsyncDeviceRequest&);

    template<typename AsyncRequestType, typename... Args>
    NonnullRefPtr<AsyncRequestType> make_request(Args&&... args)
    {
        auto request = adopt(*new AsyncRequestType(*this, forward<Args>(args)...));
        bool was_empty;
        {
            ScopedSpinLock lock(m_requests_lock);
            was_empty = m_requests.is_empty();
            m_requests.append(request);
        }
        if (was_empty)
            request->do_start({});
        return request;
    }

protected:
    Device(unsigned major, unsigned minor);
    void set_uid(uid_t uid) { m_uid = uid; }
    void set_gid(gid_t gid) { m_gid = gid; }

    static HashMap<u32, Device*>& all_devices();

private:
    unsigned m_major { 0 };
    unsigned m_minor { 0 };
    uid_t m_uid { 0 };
    gid_t m_gid { 0 };

    SpinLock<u8> m_requests_lock;
    DoublyLinkedList<RefPtr<AsyncDeviceRequest>> m_requests;
};

}