Luna/kernel/src/fs/VFS.h

#pragma once
#include "arch/Timer.h"
#include <bits/makedev.h>
#include <bits/timespec.h>
#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,
        CharacterDevice,
        BlockDevice,
        Symlink,
        FIFO,
        Socket,
    };

    struct InodeMetadata
    {
        ino_t inum;
        size_t size { 0 };
        mode_t mode;
        nlink_t nlinks { 1 };
        uid_t uid { 0 };
        gid_t gid { 0 };
        dev_t devid { 0 };

        struct timespec atime;
        struct timespec mtime;
        struct timespec ctime;
    };

    class Inode;

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

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

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

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

        virtual Result<SharedPtr<Inode>> create_symlink_inode(StringView link) = 0;

        virtual Result<u64> allocate_inode_number()
        {
            return err(ENOTSUP);
        }

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

        virtual Result<void> reset_mount_dir() = 0;

        virtual bool is_readonly() const
        {
            return false;
        }

        virtual u64 handles() const
        {
            return m_handles;
        }

        virtual void add_handle()
        {
            m_handles++;
        }

        virtual void remove_handle()
        {
            m_handles--;
        }

        virtual dev_t host_device_id() const = 0;

        virtual ~FileSystem() = default;

      protected:
        u64 m_handles { 0 };
    };

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

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

        virtual Result<u64> isatty() const
        {
            return err(ENOTTY);
        }

        virtual void did_close()
        {
        }

        virtual Result<u64> query_shared_memory(off_t, usize)
        {
            return err(EACCES);
        }

        // 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, mode_t mode) = 0;

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

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

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

        virtual Result<void> replace_entry(SharedPtr<Inode> inode, 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 will_block_if_read() const = 0;

        // Symlink-specific methods
        virtual Result<StringView> readlink()
        {
            return StringView {};
        }

        virtual const InodeMetadata& metadata() const
        {
            return m_metadata;
        }

        virtual Result<void> set_metadata(const InodeMetadata& metadata)
        {
            m_metadata = metadata;
            m_metadata.ctime = *Timer::realtime_clock();
            return {};
        }

        virtual bool is_mountpoint() const
        {
            return false;
        }

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

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

        virtual ~Inode() = default;

        virtual InodeType type() const = 0;

        virtual void add_handle()
        {
            auto* f = fs();
            if (f) f->add_handle();
        }

        virtual void remove_handle()
        {
            auto* f = fs();
            if (f) f->remove_handle();
        }

      protected:
        mutable InodeMetadata m_metadata;
        Option<u64> m_shmid {};
    };

    class FileInode : public 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*, mode_t) override
        {
            return err(ENOTDIR);
        }

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

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

        Result<void> replace_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 will_block_if_read() const override
        {
            return false;
        }

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

        virtual ~FileInode() = default;
    };

    class DeviceInode : public 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*, mode_t) override
        {
            return err(ENOTDIR);
        }

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

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

        Result<void> replace_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::CharacterDevice;
        }

        virtual ~DeviceInode() = default;
    };

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

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

    Result<SharedPtr<Inode>> create_file(const char* path, mode_t mode, 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);
    bool is_sticky(SharedPtr<Inode> inode);

    bool is_seekable(SharedPtr<Inode> inode);

    Inode& root_inode();

    Result<void> mount_root(SharedPtr<VFS::FileSystem> fs);
    Result<void> pivot_root(const char* new_root, const char* put_old, SharedPtr<VFS::Inode> working_directory);
    Result<void> mount(const char* path, SharedPtr<VFS::FileSystem> fs, Credentials auth,
                       SharedPtr<Inode> working_directory = {});

    Result<void> umount(const char* path, Credentials auth, SharedPtr<Inode> working_directory = {});
}