/*
 * Copyright (c) 2018-2021, Andreas Kling <kling@serenityos.org>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#pragma once

#include <AK/Error.h>
#include <AK/RefCounted.h>
#include <AK/RefPtr.h>
#include <AK/StringView.h>
#include <Kernel/FileSystem/InodeIdentifier.h>
#include <Kernel/Forward.h>
#include <Kernel/Locking/Mutex.h>
#include <Kernel/UnixTypes.h>
#include <Kernel/UserOrKernelBuffer.h>

namespace Kernel {

static constexpr u32 mepoch = 476763780;

class FileSystem : public RefCounted<FileSystem> {
    friend class Inode;

public:
    virtual ~FileSystem();

    FileSystemID fsid() const { return m_fsid; }
    static FileSystem* from_fsid(FileSystemID);
    static void sync();
    static void lock_all();

    virtual ErrorOr<void> initialize() = 0;
    virtual StringView class_name() const = 0;
    virtual Inode& root_inode() = 0;
    virtual bool supports_watchers() const { return false; }

    bool is_readonly() const { return m_readonly; }

    virtual unsigned total_block_count() const { return 0; }
    virtual unsigned free_block_count() const { return 0; }
    virtual unsigned total_inode_count() const { return 0; }
    virtual unsigned free_inode_count() const { return 0; }

    virtual ErrorOr<void> prepare_to_unmount() { return {}; }

    struct DirectoryEntryView {
        DirectoryEntryView(StringView name, InodeIdentifier, u8 file_type);

        StringView name;
        InodeIdentifier inode;
        u8 file_type { 0 };
    };

    virtual void flush_writes() { }

    u64 block_size() const { return m_block_size; }
    size_t fragment_size() const { return m_fragment_size; }

    virtual bool is_file_backed() const { return false; }

    // Converts file types that are used internally by the filesystem to DT_* types
    virtual u8 internal_file_type_to_directory_entry_type(const DirectoryEntryView& entry) const { return entry.file_type; }

protected:
    FileSystem();

    void set_block_size(u64 size) { m_block_size = size; }
    void set_fragment_size(size_t size) { m_fragment_size = size; }

    mutable Mutex m_lock { "FS" };

private:
    FileSystemID m_fsid;
    u64 m_block_size { 0 };
    size_t m_fragment_size { 0 };
    bool m_readonly { false };
};

inline FileSystem* InodeIdentifier::fs() // NOLINT(readability-make-member-function-const) const InodeIdentifiers should not be able to modify the FileSystem
{
    return FileSystem::from_fsid(m_fsid);
}

inline const FileSystem* InodeIdentifier::fs() const
{
    return FileSystem::from_fsid(m_fsid);
}

}

namespace AK {

template<>
struct Traits<Kernel::InodeIdentifier> : public GenericTraits<Kernel::InodeIdentifier> {
    static unsigned hash(const Kernel::InodeIdentifier& inode) { return pair_int_hash(inode.fsid().value(), inode.index().value()); }
};

}