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

#pragma once

#include <AK/RefCounted.h>
#include <AK/RefPtr.h>
#include <AK/String.h>
#include <AK/StringView.h>
#include <Kernel/FileSystem/InodeIdentifier.h>
#include <Kernel/KResult.h>
#include <Kernel/Lock.h>
#include <Kernel/UnixTypes.h>
#include <Kernel/UserOrKernelBuffer.h>

namespace Kernel {

static const u32 mepoch = 476763780;

class Inode;
class FileDescription;
class LocalSocket;
class VMObject;

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

public:
    virtual ~FS();

    unsigned fsid() const { return m_fsid; }
    static FS* from_fsid(u32);
    static void sync();
    static void lock_all();

    virtual bool initialize() = 0;
    virtual const char* class_name() const = 0;
    virtual NonnullRefPtr<Inode> root_inode() const = 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 KResult prepare_to_unmount() const { return KSuccess; }

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

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

    virtual void flush_writes() { }

    size_t block_size() const { return m_block_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:
    FS();

    void set_block_size(size_t);

    mutable Lock m_lock { "FS" };

private:
    unsigned m_fsid { 0 };
    size_t m_block_size { 0 };
    bool m_readonly { false };
};

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

inline const FS* InodeIdentifier::fs() const
{
    return FS::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(), inode.index().value()); }
};

}