#pragma once

#include <AK/HashMap.h>
#include <AK/OwnPtr.h>
#include <AK/RetainPtr.h>
#include <AK/AKString.h>
#include <AK/Vector.h>
#include <AK/Function.h>
#include "InodeIdentifier.h"
#include "InodeMetadata.h"
#include "Limits.h"
#include "FileSystem.h"

#define O_RDONLY 0
#define O_WRONLY 1
#define O_RDWR 2
#define O_CREAT 0100
#define O_EXCL 0200
#define O_NOCTTY 0400
#define O_TRUNC 01000
#define O_APPEND 02000
#define O_NONBLOCK 04000
#define O_DIRECTORY 00200000
#define O_NOFOLLOW 00400000
#define O_CLOEXEC 02000000
#define O_NOFOLLOW_NOERROR 0x4000000
#define O_DONT_OPEN_DEVICE 0x8000000

class CharacterDevice;
class FileDescriptor;

inline constexpr dword encoded_device(unsigned major, unsigned minor)
{
    return (minor & 0xff) | (major << 8) | ((minor & ~0xff) << 12);
}

class VFS;

class VFS {
    AK_MAKE_ETERNAL
public:
    class Mount {
    public:
        Mount(InodeIdentifier host, RetainPtr<FS>&&);

        InodeIdentifier host() const { return m_host; }
        InodeIdentifier guest() const { return m_guest; }

        const FS& guest_fs() const { return *m_guest_fs; }

    private:
        InodeIdentifier m_host;
        InodeIdentifier m_guest;
        RetainPtr<FS> m_guest_fs;
    };

    static VFS& the() PURE;

    VFS();
    ~VFS();

    bool mount_root(RetainPtr<FS>&&);
    bool mount(RetainPtr<FS>&&, const String& path);

    RetainPtr<FileDescriptor> open(RetainPtr<CharacterDevice>&&, int& error, int options);
    RetainPtr<FileDescriptor> open(const String& path, int& error, int options, mode_t mode, Inode& base);
    RetainPtr<FileDescriptor> create(const String& path, int& error, int options, mode_t mode, Inode& base);
    bool mkdir(const String& path, mode_t mode, Inode& base, int& error);
    bool unlink(const String& path, Inode& base, int& error);
    bool rmdir(const String& path, Inode& base, int& error);
    bool chmod(const String& path, mode_t, Inode& base, int& error);

    void register_character_device(CharacterDevice&);
    void unregister_character_device(CharacterDevice&);

    size_t mount_count() const { return m_mounts.size(); }
    void for_each_mount(Function<void(const Mount&)>) const;

    String absolute_path(Inode&);
    String absolute_path(InodeIdentifier);

    InodeIdentifier root_inode_id() const;
    Inode* root_inode() { return m_root_inode.ptr(); }
    const Inode* root_inode() const { return m_root_inode.ptr(); }

    void sync();

    CharacterDevice* get_device(unsigned major, unsigned minor);

private:
    friend class FileDescriptor;

    RetainPtr<Inode> get_inode(InodeIdentifier);

    bool is_vfs_root(InodeIdentifier) const;

    void traverse_directory_inode(Inode&, Function<bool(const FS::DirectoryEntry&)>);
    InodeIdentifier resolve_path(const String& path, InodeIdentifier base, int& error, int options = 0, InodeIdentifier* parent_id = nullptr);
    InodeIdentifier resolve_symbolic_link(InodeIdentifier base, Inode& symlink_inode, int& error);

    Mount* find_mount_for_host(InodeIdentifier);
    Mount* find_mount_for_guest(InodeIdentifier);

    RetainPtr<Inode> m_root_inode;
    Vector<OwnPtr<Mount>> m_mounts;
    HashMap<dword, CharacterDevice*> m_character_devices;
};