/*
 * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <AK/Singleton.h>
#include <Kernel/Devices/Device.h>
#include <Kernel/FileSystem/InodeMetadata.h>
#include <Kernel/FileSystem/SysFS.h>
#include <Kernel/Locking/MutexProtected.h>
#include <Kernel/Sections.h>

namespace Kernel {

static Singleton<MutexProtected<HashMap<u32, Device*>>> s_all_devices;

MutexProtected<HashMap<u32, Device*>>& Device::all_devices()
{
    return *s_all_devices;
}

NonnullRefPtr<SysFSDeviceComponent> SysFSDeviceComponent::must_create(Device const& device)
{
    return adopt_ref_if_nonnull(new SysFSDeviceComponent(device)).release_nonnull();
}
SysFSDeviceComponent::SysFSDeviceComponent(Device const& device)
    : SysFSComponent(String::formatted("{}:{}", device.major(), device.minor()))
    , m_block_device(device.is_block_device())
{
    VERIFY(device.is_block_device() || device.is_character_device());
}

UNMAP_AFTER_INIT NonnullRefPtr<SysFSDevicesDirectory> SysFSDevicesDirectory::must_create(SysFSRootDirectory const& root_directory)
{
    auto devices_directory = adopt_ref_if_nonnull(new SysFSDevicesDirectory(root_directory)).release_nonnull();
    devices_directory->m_components.append(SysFSBlockDevicesDirectory::must_create(*devices_directory));
    devices_directory->m_components.append(SysFSCharacterDevicesDirectory::must_create(*devices_directory));
    return devices_directory;
}
SysFSDevicesDirectory::SysFSDevicesDirectory(SysFSRootDirectory const& root_directory)
    : SysFSDirectory("dev"sv, root_directory)
{
}

NonnullRefPtr<SysFSBlockDevicesDirectory> SysFSBlockDevicesDirectory::must_create(SysFSDevicesDirectory const& devices_directory)
{
    return adopt_ref_if_nonnull(new SysFSBlockDevicesDirectory(devices_directory)).release_nonnull();
}
SysFSBlockDevicesDirectory::SysFSBlockDevicesDirectory(SysFSDevicesDirectory const& devices_directory)
    : SysFSDirectory("block"sv, devices_directory)
{
}
KResult SysFSBlockDevicesDirectory::traverse_as_directory(unsigned fsid, Function<bool(FileSystem::DirectoryEntryView const&)> callback) const
{
    VERIFY(m_parent_directory);
    callback({ ".", { fsid, component_index() }, 0 });
    callback({ "..", { fsid, m_parent_directory->component_index() }, 0 });

    SysFSComponentRegistry::the().devices_list().with_exclusive([&](auto& list) -> void {
        for (auto& exposed_device : list) {
            if (!exposed_device.is_block_device())
                continue;
            callback({ exposed_device.name(), { fsid, exposed_device.component_index() }, 0 });
        }
    });
    return KSuccess;
}
RefPtr<SysFSComponent> SysFSBlockDevicesDirectory::lookup(StringView name)
{
    return SysFSComponentRegistry::the().devices_list().with_exclusive([&](auto& list) -> RefPtr<SysFSComponent> {
        for (auto& exposed_device : list) {
            if (!exposed_device.is_block_device())
                continue;
            if (exposed_device.name() == name)
                return exposed_device;
        }
        return nullptr;
    });
}

NonnullRefPtr<SysFSCharacterDevicesDirectory> SysFSCharacterDevicesDirectory::must_create(SysFSDevicesDirectory const& devices_directory)
{
    return adopt_ref_if_nonnull(new SysFSCharacterDevicesDirectory(devices_directory)).release_nonnull();
}
SysFSCharacterDevicesDirectory::SysFSCharacterDevicesDirectory(SysFSDevicesDirectory const& devices_directory)
    : SysFSDirectory("char"sv, devices_directory)
{
}
KResult SysFSCharacterDevicesDirectory::traverse_as_directory(unsigned fsid, Function<bool(FileSystem::DirectoryEntryView const&)> callback) const
{
    VERIFY(m_parent_directory);
    callback({ ".", { fsid, component_index() }, 0 });
    callback({ "..", { fsid, m_parent_directory->component_index() }, 0 });

    SysFSComponentRegistry::the().devices_list().with_exclusive([&](auto& list) -> void {
        for (auto& exposed_device : list) {
            if (exposed_device.is_block_device())
                continue;
            callback({ exposed_device.name(), { fsid, exposed_device.component_index() }, 0 });
        }
    });
    return KSuccess;
}
RefPtr<SysFSComponent> SysFSCharacterDevicesDirectory::lookup(StringView name)
{
    return SysFSComponentRegistry::the().devices_list().with_exclusive([&](auto& list) -> RefPtr<SysFSComponent> {
        for (auto& exposed_device : list) {
            if (exposed_device.is_block_device())
                continue;
            if (exposed_device.name() == name)
                return exposed_device;
        }
        return nullptr;
    });
}

void Device::for_each(Function<void(Device&)> callback)
{
    all_devices().with_exclusive([&](auto& map) -> void {
        for (auto& entry : map)
            callback(*entry.value);
    });
}

Device* Device::get_device(unsigned major, unsigned minor)
{
    return all_devices().with_exclusive([&](auto& map) -> Device* {
        auto it = map.find(encoded_device(major, minor));
        if (it == map.end())
            return nullptr;
        return it->value;
    });
}

Device::Device(unsigned major, unsigned minor)
    : m_major(major)
    , m_minor(minor)
{
    u32 device_id = encoded_device(major, minor);
    all_devices().with_exclusive([&](auto& map) -> void {
        auto it = map.find(device_id);
        if (it != map.end()) {
            dbgln("Already registered {},{}: {}", major, minor, it->value->class_name());
        }
        VERIFY(!map.contains(device_id));
        map.set(device_id, this);
    });
}

void Device::after_inserting()
{
    VERIFY(!m_sysfs_component);
    auto sys_fs_component = SysFSDeviceComponent::must_create(*this);
    m_sysfs_component = sys_fs_component;
    SysFSComponentRegistry::the().devices_list().with_exclusive([&](auto& list) -> void {
        list.append(sys_fs_component);
    });
}

void Device::before_removing()
{
    m_state = State::BeingRemoved;
    VERIFY(m_sysfs_component);
    SysFSComponentRegistry::the().devices_list().with_exclusive([&](auto& list) -> void {
        list.remove(*m_sysfs_component);
    });
}

Device::~Device()
{
    VERIFY(m_state == State::BeingRemoved);
    u32 device_id = encoded_device(m_major, m_minor);
    all_devices().with_exclusive([&](auto& map) -> void {
        VERIFY(map.contains(device_id));
        map.remove(encoded_device(m_major, m_minor));
    });
}

String Device::absolute_path() const
{
    // FIXME: I assume we can't really provide a well known path in the kernel
    // because this is a violation of abstraction layers between userland and the
    // kernel, but maybe the whole name of "absolute_path" is just wrong as this
    // is really not an "absolute_path".
    return String::formatted("device:{},{}", major(), minor());
}

String Device::absolute_path(const OpenFileDescription&) const
{
    return absolute_path();
}

void Device::process_next_queued_request(Badge<AsyncDeviceRequest>, const AsyncDeviceRequest& completed_request)
{
    SpinlockLocker lock(m_requests_lock);
    VERIFY(!m_requests.is_empty());
    VERIFY(m_requests.first().ptr() == &completed_request);
    m_requests.remove(m_requests.begin());
    if (!m_requests.is_empty()) {
        auto* next_request = m_requests.first().ptr();
        next_request->do_start(move(lock));
    }

    evaluate_block_conditions();
}

}