gplib/include/gp/vfs/io/io_operation.hpp

#pragma once

#include "gp/array.hpp"

#include <cstddef>
#include <cstdint>

// TODO: File locking and fsync/fdatasync

/**
 * @brief this enum represents the types of operations available
 */
enum class operation_type {
	version, ///< this operation queries properties of the filesystem
	flush, ///< flushes any buffer for writing on the filesystem
	attach, ///< adds a filesystem to the system
	detach, ///< remove a filesystem from the system
	walk, ///< change the current directory
	create, ///< creates a file
	open, ///< opens a file, yielding a fid
	read, ///< reads from a file
	write, ///< writes to a file
	clunk, ///< relinquishes a fid
	remove, ///< removes a file
	stat, ///< reads a file metadata
	wstat ///< writes a file metadata
};

/**
 * @brief this enum represent the type of file handled
 */
enum class file_type {
	directory, ///< the file is a normal directory
	master_directory, ///< the file is the root directory of a non-root filesystem
	device_directory, ///< the file is a driver mapped to a directory
	root_directory, ///< the file is the root directory
	file, ///< the file is a normal file
	file_device, ///< the file is a driver mapped to a file
	message_pipe ///< the file is a channel to read and write messages to
};

/**
 * @brief represents file permissions
 */
struct permission_list {
	bool 
	read : 1,
	write : 1,
	execute : 1;
};

/**
 * @brief represents all levels of permissions in a file
 */
struct file_permissions {
	permission_list
		user, ///< list of permissions for the owner
		group, ///< list of permissions for the owning group
		others; ///< list of permissions for other users
};

/**
 * @brief represent a value that should be unique for every entity of the system
 */
using unique_node = uint64_t;

/**
 * @brief represent a timestamp in seconds
 */
using timestamp = uint64_t;

/**
 * @brief represent a value that represent an offset into a file
 */
using file_offset = uint64_t;

/**
 * @brief the expected return type of a stat query, as well as its writing counterpart
 */
struct f_stats {
	file_type type; ///< the type of file
	unique_node file_id; ///< the unique file id
	unique_node owner_user_id; ///< the user id of the owner of the file
	unique_node owner_group_id; ///< the group id of the file
	unique_node last_modifier_id; ///< the user id of the last user that wrote data to the file
	timestamp last_access; ///< the timestamp for the last time the file was opened or created. If the current user is not root, it is replaced by the system on wstat
	timestamp last_modification; ///< the last modification timestamp. If the current user is not root, it is replaced by the system on wstat
	file_offset file_size; ///< the filesize in bytes
	gp::array<char, 255> filename; ///< the filename, padded with null characters
};

/**
 * @brief Represent an IO operation as sent to the system, this is an abstract class.
 */
struct io_operation {
	const operation_type type; ///< the discriminant for the operation type
protected:
	io_operation(operation_type a) : type(a) {}
};

/**
 * @brief This operation obtains the version of the targeted filesystem
 */
struct version_operation : public io_operation {
	const gp::buffer<char> destination; ///< the destination where the data is written
	const gp::buffer<char> root_path; ///< the path of the file system to query for version
	const gp::optional<gp_config::file_descriptor_t> fd; ///< the relative root to use

	/**
	 * @brief Construct a new version operation object
	 * 
	 * @param dest the destination where the data is written
	 * @param path the path to the target filesystem
	 * @param v_fd a relative root that is used
	 */
	version_operation(
		gp::buffer<char> dest, 
		gp::buffer<char> path, 
		gp::optional<gp_config::file_descriptor_t> v_fd
	)
	: io_operation{operation_type::version}
	, destination(dest)
	, root_path(path)
	, fd(v_fd)
	{}
};

/**
 * @brief This operation flushes a filesystem, writing the data to the associated medium
 */
struct flush_operation : public io_operation {
	const gp::buffer<char> root_path; ///< the path that is going to be flushed
	const gp::optional<gp_config::file_descriptor_t> fd; ///< the relative root to use

	/**
	 * @brief Construct a new flush operation object
	 * 
	 * @param path the path to a file or to a master directory that is to be flushed
	 * @param v_fd a relative root that is used
	 */
	flush_operation(
		gp::buffer<char> path, 
		gp::optional<gp_config::file_descriptor_t> v_fd
	)
	: io_operation{operation_type::flush}
	, root_path(path)
	, fd(v_fd)
	{}
};

/**
 * @brief This operation mounts a filesystem given a format and a configuration data.
 *
 * It also mounts devices.
 */
struct attach_operation : public io_operation {
	const gp::buffer<char> target_path; ///< location where the filesystem is going to be attached
	const gp::buffer<char> format; ///< format string of the filesystem
	const gp::buffer<char> configuration; ///< configuration data
	const gp::optional<gp_config::file_descriptor_t> fd; ///< the relative root to use

	/**
	 * @brief Construct a new attach operation object
	 * 
	 * @param path path where the filesystem will be attached, must be either not existing or an empty directory
	 * @param v_format the format name that will be invoked with the config
	 * @param config the configuration to send
	 * @param v_fd a relative root that is used
	 */
	attach_operation(
		gp::buffer<char> path, 
		gp::buffer<char> v_format, 
		gp::buffer<char> config, 
		gp::optional<gp_config::file_descriptor_t> v_fd
	)
	: io_operation{operation_type::attach}
	, target_path(path)
	, format(v_format)
	, configuration(config)
	, fd(v_fd)
	{}
};

/**
 * @brief This operation removes the master status of a directory and dismounts the 
 * filesystem attached to it after flushing it. Will fail if any file is still attached 
 * in the filesystem.
 *
 * This applies to the devices too.
 */
struct detach_operation : public io_operation {
	const gp::buffer<char> target_path; ///< the target master directory
	const gp::optional<gp_config::file_descriptor_t> fd; ///< the relative root to use

	/**
	 * @brief Construct a new detach operation object
	 * 
	 * @param path the item to be detached
	 * @param v_fd a relative root that is used
	 */
	detach_operation(
		gp::buffer<char> path, 
		gp::optional<gp_config::file_descriptor_t> v_fd
	)
	: io_operation{operation_type::attach}
	, target_path(path)
	, fd(v_fd)
	{}
};

/**
 * @brief This operation will move the focus of the target directory relative to itself or absolutely
 */
struct walk_operation : public io_operation {
	const gp::buffer<char> target_path; ///< the target to move to
	const gp_config::file_descriptor_t fd_to_alter; ///< the fd that will be modified

	/**
	 * @brief Construct a new walk operation object
	 * 
	 * @param path the target to move to
	 * @param dir the original file descriptor
	 */
	walk_operation(
		gp::buffer<char> path, 
		gp_config::file_descriptor_t dir
	)
	: io_operation{operation_type::walk}
	, target_path(path)
	, fd_to_alter(dir)
	{}
};

/**
 * @brief selector for the type of file to be created in a given environment
 */
enum class create_type {
	file, ///< normal file
	directory, ///< directory file
	temporary, ///< file which is to be remove upon all of his descriptors being closed
	pipe_read_side, ///< pipe, read side returned
	pipe_write_side ///< pipe, write side returned
};

/**
 * @brief This operation will attempt to create a file at the specified destination
 */
struct create_operation : public io_operation {
	const gp::buffer<char> target_path;
	const create_type mode;
	const gp::optional<gp_config::file_descriptor_t> fd;

	/**
	 * @brief Create a new create operation object
	 * 
	 * @param path the new file that is created
	 * @param v_mode the type of file to create
	 * @param v_fd a relative root that is used
	 */
	create_operation(
		gp::buffer<char> path, 
		create_type v_mode,
		gp::optional<gp_config::file_descriptor_t> v_fd
	)
	: io_operation{operation_type::create}
	, target_path(path)
	, mode(v_mode)
	, fd(v_fd)
	{}
};

/**
 * @brief selector for the properties expected from an opened file descriptor
 */
enum class open_mode {
	read_only, ///< the descriptor will be read only, will fail if no read permissions
	read_write, ///< the descriptor is read-write, will fail if no write permissions, but not if no read permissions
	read_write_create ///< the descriptor is read-write, and has the same proterties as the read-write. The file will be created if it does not exist.
};

/**
 * @brief This operation will attempt to open a file at the specified destination
 */
struct open_operation : public io_operation {
	const gp::buffer<char> target_path; ///< the specified path
	open_mode mode; ///< the openning mode
	const gp::optional<gp_config::file_descriptor_t> fd; ///< the relative root to use

	/**
	 * @brief Construct a new open operation object
	 * 
	 * @param path the path where to open a file
	 * @param v_mode the mode of opening
	 * @param v_fd a relative root that is used
	 */
	open_operation(
		gp::buffer<char> path, 
		open_mode v_mode, 
		gp::optional<gp_config::file_descriptor_t> v_fd
	)
	: io_operation{operation_type::create}
	, target_path(path)
	, mode(v_mode)
	, fd(v_fd)
	{}
};

/**
 * @brief This operation will attempt to read a file into the destination starting at the specified offset in the file
 */
struct read_operation : public io_operation {
	const gp_config::file_descriptor_t fd; ///< the file to read
	const file_offset offset; ///< the offset to start reading at
	const gp::buffer<char> destination; ///< the destination where to write the data

	/**
	 * @brief Construct a new read operation object
	 * 
	 * @param v_fd the descriptor to read
	 * @param off the offset to read
	 * @param v_destination the location where the data will be written
	 */
	read_operation(
		gp_config::file_descriptor_t v_fd, 
		file_offset off, 
		gp::buffer<char> v_destination
	)
	: io_operation{operation_type::read}
	, fd{v_fd}
	, offset(off)
	, destination(v_destination)
	{}
};

/**
 * @brief This operation will attempt to write in file from the source starting at the specified offset in the file
 */
struct write_operation : public io_operation {
	const gp_config::file_descriptor_t fd; ///< the descriptor of the file where writing happens
	const file_offset offset; ///< the offset in the file where writing starts
	const gp::buffer<char> source; ///< the source data

	/**
	 * @brief Construct a new write operation object
	 * 
	 * @param v_fd the target file
	 * @param off the target offset
	 * @param v_source the data source buffer
	 */
	write_operation(
		gp_config::file_descriptor_t v_fd, 
		file_offset off, 
		gp::buffer<char> v_source
	)
	: io_operation{operation_type::write}
	, fd{v_fd}
	, offset(off)
	, source(v_source)
	{}
};

/**
 * @brief This operation closes a file by relinquishing its file descriptor
 */
struct clunk_operation : public io_operation {
	const gp_config::file_descriptor_t fd; ///< The descriptor that will be disposed of

	/**
	 * @brief Construct a new clunk operation object
	 * 
	 * @param v_fd the fd to close
	 */
	clunk_operation(gp_config::file_descriptor_t v_fd)
	: io_operation{operation_type::clunk}
	, fd{v_fd}
	{}
};

/**
 * @brief This operation removes a fileas soon as all its file descriptors are given back
 */
struct remove_operation : public io_operation {
	const gp::buffer<char*> target_path; ///< the target file
	const gp::optional<gp_config::file_descriptor_t> fd; ///< the relative root to use

	/**
	 * @brief Construct a new remove operation object
	 * 
	 * @param path the path to the file to remove
	 * @param v_fd a relative root that is used
	 */
	remove_operation(
		gp::buffer<char*> path, 
		gp::optional<gp_config::file_descriptor_t> v_fd
	)
	: io_operation{operation_type::remove}
	, target_path(path)
	, fd(v_fd)
	{}
};

/**
 * @brief This operation fetches metadata about a file
 */
struct stat_operation : public io_operation {
	const gp::buffer<char*> target_path; ///< the file to query metadata about
	const gp::optional<gp_config::file_descriptor_t> fd; ///< the relative root to use

	/**
	 * @brief Construct a new stat operation object
	 * 
	 * @param path the path to the file to query about
	 * @param v_fd a relative root that is used
	 */
	stat_operation(
		gp::buffer<char*> path, 
		gp::optional<gp_config::file_descriptor_t> v_fd
	)
	: io_operation{operation_type::stat}
	, target_path(path)
	, fd(v_fd)
	{}
};

/**
 * @brief This operation writes metadata about a file
 */
struct wstat_operation : public io_operation {
	const gp::buffer<char*> target_path; ///< the file to set metadata on
	const gp::optional<gp_config::file_descriptor_t> fd; ///< the relative root to use

	/**
	 * @brief Construct a new wstat operation object
	 * 
	 * @param path the path to the file to write about
	 * @param v_fd a relative root that is used
	 */
	wstat_operation(
		gp::buffer<char*> path, 
		gp::optional<gp_config::file_descriptor_t> v_fd
	)
	: io_operation{operation_type::wstat}
	, target_path(path)
	, fd(v_fd)
	{}
};