Luna/kernel/src/fs/VFS.h

#pragma once
#include <luna/SharedPtr.h>
#include <luna/StaticString.h>
#include <luna/StringView.h>
#include <sys/types.h>

struct Credentials;

namespace VFS
{
    enum class InodeType
    {
        RegularFile,
        Directory,
        Device
    };

    class FileSystem;
    class Inode;

    struct DirectoryEntry
    {
      public:
        SharedPtr<Inode> inode;
        StaticString<128> name;
    };

    class Inode
    {
      public:
        virtual Result<u64> ioctl(int, void*)
        {
            return err(ENOTTY);
        }

        // Directory-specific methods
        virtual Result<SharedPtr<Inode>> find(const char* name) const = 0;

        virtual Option<DirectoryEntry> get(usize index) const = 0;

        virtual Result<SharedPtr<Inode>> create_file(const char* name) = 0;

        virtual Result<SharedPtr<Inode>> create_subdirectory(const char* name) = 0;

        virtual Result<void> add_entry(SharedPtr<Inode> inode, const char* name) = 0;

        virtual Result<void> remove_entry(const char* name) = 0;

        virtual usize entries() const = 0;

        // File-specific methods
        virtual Result<usize> read(u8* buf, usize offset, usize length) const = 0;

        virtual Result<usize> write(const u8* buf, usize offset, usize length) = 0;

        virtual Result<void> truncate(usize size) = 0;

        virtual bool blocking() const = 0;

        // Metadata accessors
        virtual usize size() const = 0;

        virtual mode_t mode() const = 0;

        virtual u32 uid() const
        {
            return 0;
        }

        virtual u32 gid() const
        {
            return 0;
        }

        virtual void did_link() = 0;
        virtual void did_unlink() = 0;

        // Metadata changers
        virtual Result<void> chmod(mode_t mode) = 0;

        virtual Result<void> chown(u32 uid, u32 gid) = 0;

        // Generic VFS-related methods
        virtual FileSystem* fs() const = 0;

        virtual ~Inode() = default;

        virtual InodeType type() const = 0;

        virtual usize inode_number() const = 0;
    };

    class FileInode : Inode
    {
      public:
        Result<SharedPtr<Inode>> find(const char*) const override
        {
            return err(ENOTDIR);
        }

        Option<DirectoryEntry> get(usize) const override
        {
            return {};
        }

        Result<SharedPtr<Inode>> create_file(const char*) override
        {
            return err(ENOTDIR);
        }

        Result<SharedPtr<Inode>> create_subdirectory(const char*) override
        {
            return err(ENOTDIR);
        }

        Result<void> add_entry(SharedPtr<Inode>, const char*) override
        {
            return err(ENOTDIR);
        }

        Result<void> remove_entry(const char*) override
        {
            return err(ENOTDIR);
        }

        usize entries() const override
        {
            return 0;
        }

        bool blocking() const override
        {
            return false;
        }

        InodeType type() const override
        {
            return InodeType::RegularFile;
        }

        virtual ~FileInode() = default;
    };

    class DeviceInode : Inode
    {
      public:
        Result<SharedPtr<Inode>> find(const char*) const override
        {
            return err(ENOTDIR);
        }

        Option<DirectoryEntry> get(usize) const override
        {
            return {};
        }

        Result<SharedPtr<Inode>> create_file(const char*) override
        {
            return err(ENOTDIR);
        }

        Result<SharedPtr<Inode>> create_subdirectory(const char*) override
        {
            return err(ENOTDIR);
        }

        Result<void> add_entry(SharedPtr<Inode>, const char*) override
        {
            return err(ENOTDIR);
        }

        Result<void> remove_entry(const char*) override
        {
            return err(ENOTDIR);
        }

        usize entries() const override
        {
            return 0;
        }

        InodeType type() const override
        {
            return InodeType::Device;
        }

        virtual ~DeviceInode() = default;
    };

    class FileSystem
    {
      public:
        virtual SharedPtr<Inode> root_inode() const = 0;

        virtual Result<SharedPtr<Inode>> create_file_inode() = 0;

        virtual Result<SharedPtr<Inode>> create_dir_inode(SharedPtr<Inode> parent) = 0;

        virtual Result<SharedPtr<Inode>> create_device_inode(u32 major, u32 minor) = 0;

        virtual ~FileSystem() = default;
    };

    extern SharedPtr<FileSystem> root_fs;

    Result<SharedPtr<Inode>> resolve_path(const char* path, Credentials auth,
                                          SharedPtr<VFS::Inode> working_directory = {});

    Result<SharedPtr<Inode>> create_directory(const char* path, Credentials auth,
                                              SharedPtr<VFS::Inode> working_directory = {});

    Result<SharedPtr<Inode>> create_file(const char* path, Credentials auth,
                                         SharedPtr<VFS::Inode> working_directory = {});

    Result<void> validate_filename(StringView name);

    bool can_execute(SharedPtr<Inode> inode, Credentials auth);
    bool can_read(SharedPtr<Inode> inode, Credentials auth);
    bool can_write(SharedPtr<Inode> inode, Credentials auth);
    bool is_setuid(SharedPtr<Inode> inode);
    bool is_setgid(SharedPtr<Inode> inode);

    Inode& root_inode();
}