package os

foreign import dl   "system:dl"
foreign import libc "System.framework"
foreign import pthread "System.framework"

import "core:runtime"
import "core:strings"
import "core:strconv"
import "core:c"

Handle    :: distinct i32;
File_Time :: distinct u64;
Errno     :: distinct int;

INVALID_HANDLE :: ~Handle(0);

ERROR_NONE: Errno : 0;
EPERM:		Errno : 1;		/* Operation not permitted */
ENOENT:		Errno : 2;		/* No such file or directory */
ESRCH:		Errno : 3;		/* No such process */
EINTR:		Errno : 4;		/* Interrupted system call */
EIO:		Errno : 5;		/* Input/output error */
ENXIO:		Errno : 6;		/* Device not configured */
E2BIG:		Errno : 7;		/* Argument list too long */
ENOEXEC:	Errno : 8;		/* Exec format error */
EBADF:		Errno : 9;		/* Bad file descriptor */
ECHILD:		Errno : 10;		/* No child processes */
EDEADLK:	Errno : 11;		/* Resource deadlock avoided */
ENOMEM:		Errno : 12;		/* Cannot allocate memory */
EACCES:		Errno : 13;		/* Permission denied */
EFAULT:		Errno : 14;		/* Bad address */
ENOTBLK:	Errno : 15;		/* Block device required */
EBUSY:		Errno : 16;		/* Device / Resource busy */
EEXIST:		Errno : 17;		/* File exists */
EXDEV:		Errno : 18;		/* Cross-device link */
ENODEV:		Errno : 19;		/* Operation not supported by device */
ENOTDIR:	Errno : 20;		/* Not a directory */
EISDIR:		Errno : 21;		/* Is a directory */
EINVAL:		Errno : 22;		/* Invalid argument */
ENFILE:		Errno : 23;		/* Too many open files in system */
EMFILE:		Errno : 24;		/* Too many open files */
ENOTTY:		Errno : 25;		/* Inappropriate ioctl for device */
ETXTBSY:	Errno : 26;		/* Text file busy */
EFBIG:		Errno : 27;		/* File too large */
ENOSPC:		Errno : 28;		/* No space left on device */
ESPIPE:		Errno : 29;		/* Illegal seek */
EROFS:		Errno : 30;		/* Read-only file system */
EMLINK:		Errno : 31;		/* Too many links */
EPIPE:		Errno : 32;		/* Broken pipe */

/* math software */
EDOM:		Errno : 33;		/* Numerical argument out of domain */
ERANGE:		Errno : 34;		/* Result too large */

/* non-blocking and interrupt i/o */
EAGAIN:			Errno : 35;		/* Resource temporarily unavailable */
EWOULDBLOCK: 	Errno : EAGAIN;		/* Operation would block */
EINPROGRESS: 	Errno : 36;		/* Operation now in progress */
EALREADY:		Errno : 37;		/* Operation already in progress */

/* ipc/network software -- argument errors */
ENOTSOCK:			Errno : 38;		/* Socket operation on non-socket */
EDESTADDRREQ:		Errno : 39;		/* Destination address required */
EMSGSIZE:			Errno : 40;		/* Message too long */
EPROTOTYPE:			Errno : 41;		/* Protocol wrong type for socket */
ENOPROTOOPT:		Errno : 42;		/* Protocol not available */
EPROTONOSUPPORT:	Errno : 43;		/* Protocol not supported */
ESOCKTNOSUPPORT:	Errno : 44;		/* Socket type not supported */
ENOTSUP:			Errno : 45;		/* Operation not supported */
EPFNOSUPPORT:		Errno : 46;		/* Protocol family not supported */
EAFNOSUPPORT:		Errno : 47;		/* Address family not supported by protocol family */
EADDRINUSE:			Errno : 48;		/* Address already in use */
EADDRNOTAVAIL:		Errno : 49;		/* Can't assign requested address */

/* ipc/network software -- operational errors */
ENETDOWN:		Errno : 50;		/* Network is down */
ENETUNREACH:	Errno : 51;		/* Network is unreachable */
ENETRESET:		Errno : 52;		/* Network dropped connection on reset */
ECONNABORTED:	Errno : 53;		/* Software caused connection abort */
ECONNRESET:		Errno : 54;		/* Connection reset by peer */
ENOBUFS:		Errno : 55;		/* No buffer space available */
EISCONN:		Errno : 56;		/* Socket is already connected */
ENOTCONN:		Errno : 57;		/* Socket is not connected */
ESHUTDOWN:		Errno : 58;		/* Can't send after socket shutdown */
ETOOMANYREFS:	Errno : 59;		/* Too many references: can't splice */
ETIMEDOUT:		Errno : 60;		/* Operation timed out */
ECONNREFUSED:	Errno : 61;		/* Connection refused */

ELOOP:			Errno : 62;		/* Too many levels of symbolic links */
ENAMETOOLONG:	Errno : 63;		/* File name too long */

/* should be rearranged */
EHOSTDOWN:		Errno : 64;		/* Host is down */
EHOSTUNREACH:	Errno : 65;		/* No route to host */
ENOTEMPTY:		Errno : 66;		/* Directory not empty */

/* quotas & mush */
EPROCLIM:		Errno : 67;		/* Too many processes */
EUSERS:			Errno : 68;		/* Too many users */
EDQUOT:			Errno : 69;		/* Disc quota exceeded */

/* Network File System */
ESTALE:			Errno : 70;		/* Stale NFS file handle */
EREMOTE:		Errno : 71;		/* Too many levels of remote in path */
EBADRPC:		Errno : 72;		/* RPC struct is bad */
ERPCMISMATCH:	Errno : 73;		/* RPC version wrong */
EPROGUNAVAIL:	Errno : 74;		/* RPC prog. not avail */
EPROGMISMATCH:	Errno : 75;		/* Program version wrong */
EPROCUNAVAIL:	Errno : 76;		/* Bad procedure for program */

ENOLCK:	Errno : 77;		/* No locks available */
ENOSYS:	Errno : 78;		/* Function not implemented */

EFTYPE:	Errno : 79;		/* Inappropriate file type or format */
EAUTH:	Errno : 80;		/* Authentication error */
ENEEDAUTH:	Errno : 81;		/* Need authenticator */

/* Intelligent device errors */
EPWROFF:	Errno : 82;	/* Device power is off */
EDEVERR:	Errno : 83;	/* Device error, e.g. paper out */
EOVERFLOW:	Errno : 84;		/* Value too large to be stored in data type */

/* Program loading errors */
EBADEXEC:	Errno : 85;	/* Bad executable */
EBADARCH:	Errno : 86;	/* Bad CPU type in executable */
ESHLIBVERS:	Errno : 87;	/* Shared library version mismatch */
EBADMACHO:	Errno : 88;	/* Malformed Macho file */

ECANCELED:	Errno : 89;		/* Operation canceled */

EIDRM:		Errno : 90;		/* Identifier removed */
ENOMSG:		Errno : 91;		/* No message of desired type */
EILSEQ:		Errno : 92;		/* Illegal byte sequence */
ENOATTR:	Errno : 93;		/* Attribute not found */

EBADMSG:	Errno : 94;		/* Bad message */
EMULTIHOP:	Errno : 95;		/* Reserved */
ENODATA:	Errno : 96;		/* No message available on STREAM */
ENOLINK:	Errno : 97;		/* Reserved */
ENOSR:		Errno : 98;		/* No STREAM resources */
ENOSTR:		Errno : 99;		/* Not a STREAM */
EPROTO:		Errno : 100;		/* Protocol error */
ETIME:		Errno : 101;		/* STREAM ioctl timeout */

ENOPOLICY:	Errno : 103;		/* No such policy registered */

ENOTRECOVERABLE:	Errno : 104;		/* State not recoverable */
EOWNERDEAD:			Errno : 105;		/* Previous owner died */

EQFULL:	Errno : 106;		/* Interface output queue is full */
ELAST:	Errno : 106;		/* Must be equal largest errno */

O_RDONLY   :: 0x0000;
O_WRONLY   :: 0x0001;
O_RDWR     :: 0x0002;
O_CREATE   :: 0x0200;
O_EXCL     :: 0x0800;
O_NOCTTY   :: 0;
O_TRUNC    :: 0x0400;
O_NONBLOCK :: 0x0004;
O_APPEND   :: 0x0008;
O_SYNC     :: 0x0080;
O_ASYNC    :: 0x0040;
O_CLOEXEC  :: 0x1000000;

SEEK_SET   :: 0;
SEEK_CUR   :: 1;
SEEK_END   :: 2;
SEEK_DATA  :: 3;
SEEK_HOLE  :: 4;
SEEK_MAX   :: SEEK_HOLE;



// NOTE(zangent): These are OS specific!
// Do not mix these up!
RTLD_LAZY     :: 0x1;
RTLD_NOW      :: 0x2;
RTLD_LOCAL    :: 0x4;
RTLD_GLOBAL   :: 0x8;
RTLD_NODELETE :: 0x80;
RTLD_NOLOAD   :: 0x10;
RTLD_FIRST    :: 0x100;


// "Argv" arguments converted to Odin strings
args := _alloc_command_line_arguments();

Unix_File_Time :: struct {
	seconds: i64,
	nanoseconds: i64,
}

OS_Stat :: struct {
	device_id:     i32, // ID of device containing file
	mode:          u16, // Mode of the file
	nlink:         u16, // Number of hard links
	serial:        u64, // File serial number
	uid:           u32, // User ID of the file's owner
	gid:           u32, // Group ID of the file's group
	rdev:          i32, // Device ID, if device

	last_access:   Unix_File_Time, // Time of last access
	modified:      Unix_File_Time, // Time of last modification
	status_change: Unix_File_Time, // Time of last status change
	created:       Unix_File_Time, // Time of creation

	size:          i64,  // Size of the file, in bytes
	blocks:        i64,  // Number of blocks allocated for the file
	block_size:    i32,  // Optimal blocksize for I/O
	flags:         u32,  // User-defined flags for the file
	gen_num:       u32,  // File generation number ..?
	_spare:        i32,  // RESERVED
	_reserve1,
	_reserve2:     i64,  // RESERVED
};

// NOTE(laleksic, 2021-01-21): Comment and rename these to match OS_Stat above
Dirent :: struct {
	ino:    u64,
	off:    u64,
	reclen: u16,
	type:   u8,
	name:   [256]byte,
};

Dir :: distinct rawptr; // DIR*

// File type
S_IFMT   :: 0o170000; // Type of file mask
S_IFIFO  :: 0o010000; // Named pipe (fifo)
S_IFCHR  :: 0o020000; // Character special
S_IFDIR  :: 0o040000; // Directory
S_IFBLK  :: 0o060000; // Block special
S_IFREG  :: 0o100000; // Regular
S_IFLNK  :: 0o120000; // Symbolic link
S_IFSOCK :: 0o140000; // Socket

// File mode
// Read, write, execute/search by owner
S_IRWXU :: 0o0700; // RWX mask for owner
S_IRUSR :: 0o0400; // R for owner
S_IWUSR :: 0o0200; // W for owner
S_IXUSR :: 0o0100; // X for owner

// Read, write, execute/search by group
S_IRWXG :: 0o0070; // RWX mask for group
S_IRGRP :: 0o0040; // R for group
S_IWGRP :: 0o0020; // W for group
S_IXGRP :: 0o0010; // X for group

// Read, write, execute/search by others
S_IRWXO :: 0o0007; // RWX mask for other
S_IROTH :: 0o0004; // R for other
S_IWOTH :: 0o0002; // W for other
S_IXOTH :: 0o0001; // X for other

S_ISUID :: 0o4000; // Set user id on execution
S_ISGID :: 0o2000; // Set group id on execution
S_ISVTX :: 0o1000; // Directory restrcted delete

S_ISLNK  :: #force_inline proc(m: u32) -> bool { return (m & S_IFMT) == S_IFLNK;  }
S_ISREG  :: #force_inline proc(m: u32) -> bool { return (m & S_IFMT) == S_IFREG;  }
S_ISDIR  :: #force_inline proc(m: u32) -> bool { return (m & S_IFMT) == S_IFDIR;  }
S_ISCHR  :: #force_inline proc(m: u32) -> bool { return (m & S_IFMT) == S_IFCHR;  }
S_ISBLK  :: #force_inline proc(m: u32) -> bool { return (m & S_IFMT) == S_IFBLK;  }
S_ISFIFO :: #force_inline proc(m: u32) -> bool { return (m & S_IFMT) == S_IFIFO;  }
S_ISSOCK :: #force_inline proc(m: u32) -> bool { return (m & S_IFMT) == S_IFSOCK; }

R_OK :: 4; // Test for read permission
W_OK :: 2; // Test for write permission
X_OK :: 1; // Test for execute permission
F_OK :: 0; // Test for file existance

foreign libc {
	@(link_name="__error") __error :: proc() -> ^int ---;

	@(link_name="open")             _unix_open          :: proc(path: cstring, flags: i32, mode: u16) -> Handle ---;
	@(link_name="close")            _unix_close         :: proc(handle: Handle) ---;
	@(link_name="read")             _unix_read          :: proc(handle: Handle, buffer: rawptr, count: int) -> int ---;
	@(link_name="write")            _unix_write         :: proc(handle: Handle, buffer: rawptr, count: int) -> int ---;
	@(link_name="lseek")            _unix_lseek         :: proc(fs: Handle, offset: int, whence: int) -> int ---;
	@(link_name="gettid")           _unix_gettid        :: proc() -> u64 ---;
	@(link_name="getpagesize")      _unix_getpagesize   :: proc() -> i32 ---;
	@(link_name="stat64")           _unix_stat          :: proc(path: cstring, stat: ^OS_Stat) -> c.int ---;
	@(link_name="lstat")            _unix_lstat         :: proc(path: cstring, stat: ^OS_Stat) -> c.int ---;
	@(link_name="fstat")            _unix_fstat         :: proc(fd: Handle, stat: ^OS_Stat) -> c.int ---;
	@(link_name="readlink")         _unix_readlink      :: proc(path: cstring, buf: ^byte, bufsiz: c.size_t) -> c.ssize_t ---;
	@(link_name="access")           _unix_access        :: proc(path: cstring, mask: int) -> int ---;
	@(link_name="fdopendir")        _unix_fdopendir     :: proc(fd: Handle) -> Dir ---;
	@(link_name="closedir")         _unix_closedir      :: proc(dirp: Dir) -> c.int ---;
	@(link_name="rewinddir")        _unix_rewinddir     :: proc(dirp: Dir) ---;
	@(link_name="readdir_r")        _unix_readdir_r     :: proc(dirp: Dir, entry: ^Dirent, result: ^^Dirent) -> c.int ---;

	@(link_name="malloc")   _unix_malloc   :: proc(size: int) -> rawptr ---;
	@(link_name="calloc")   _unix_calloc   :: proc(num, size: int) -> rawptr ---;
	@(link_name="free")     _unix_free     :: proc(ptr: rawptr) ---;
	@(link_name="realloc")  _unix_realloc  :: proc(ptr: rawptr, size: int) -> rawptr ---;
	@(link_name="getenv")   _unix_getenv   :: proc(cstring) -> cstring ---;
	@(link_name="getcwd")   _unix_getcwd   :: proc(buf: cstring, len: c.size_t) -> cstring ---;
	@(link_name="chdir")    _unix_chdir    :: proc(buf: cstring) -> c.int ---;
	@(link_name="realpath") _unix_realpath :: proc(path: cstring, resolved_path: rawptr) -> rawptr ---;

	@(link_name="exit")    _unix_exit :: proc(status: int) -> ! ---;
}

foreign dl {
	@(link_name="dlopen")  _unix_dlopen  :: proc(filename: cstring, flags: int) -> rawptr ---;
	@(link_name="dlsym")   _unix_dlsym   :: proc(handle: rawptr, symbol: cstring) -> rawptr ---;
	@(link_name="dlclose") _unix_dlclose :: proc(handle: rawptr) -> int ---;
	@(link_name="dlerror") _unix_dlerror :: proc() -> cstring ---;
}

get_last_error :: proc() -> int {
	return __error()^;
}

open :: proc(path: string, flags: int = O_RDONLY, mode: int = 0) -> (Handle, Errno) {
	cstr := strings.clone_to_cstring(path);
	handle := _unix_open(cstr, i32(flags), u16(mode));
	delete(cstr);
	if handle == -1 {
		return INVALID_HANDLE, 1;
	}
	return handle, 0;
}

close :: proc(fd: Handle) {
	_unix_close(fd);
}

write :: proc(fd: Handle, data: []u8) -> (int, Errno) {
	assert(fd != -1);

	if len(data) == 0 {
		return 0, 0;
	}
	bytes_written := _unix_write(fd, raw_data(data), len(data));
	if bytes_written == -1 {
		return 0, 1;
	}
	return bytes_written, 0;
}

read :: proc(fd: Handle, data: []u8) -> (int, Errno) {
	assert(fd != -1);

	bytes_read := _unix_read(fd, raw_data(data), len(data));
	if bytes_read == -1 {
		return 0, 1;
	}
	return bytes_read, 0;
}

seek :: proc(fd: Handle, offset: i64, whence: int) -> (i64, Errno) {
	assert(fd != -1);

	final_offset := i64(_unix_lseek(fd, int(offset), whence));
	if final_offset == -1 {
		return 0, 1;
	}
	return final_offset, 0;
}

file_size :: proc(fd: Handle) -> (i64, Errno) {
	prev, _   := seek(fd, 0, SEEK_CUR);
	size, err := seek(fd, 0, SEEK_END);
	seek(fd, prev, SEEK_SET);
	return i64(size), err;
}



// NOTE(bill): Uses startup to initialize it
stdin:  Handle = 0; // get_std_handle(win32.STD_INPUT_HANDLE);
stdout: Handle = 1; // get_std_handle(win32.STD_OUTPUT_HANDLE);
stderr: Handle = 2; // get_std_handle(win32.STD_ERROR_HANDLE);

/* TODO(zangent): Implement these!
last_write_time :: proc(fd: Handle) -> File_Time {}
last_write_time_by_name :: proc(name: string) -> File_Time {}
*/

is_path_separator :: proc(r: rune) -> bool {
	return r == '/';
}


@private
_stat :: proc(path: string) -> (OS_Stat, Errno) {
	cstr := strings.clone_to_cstring(path, context.temp_allocator);

	s: OS_Stat;
	result := _unix_stat(cstr, &s);
	if result == -1 {
		return s, Errno(get_last_error());
	}
	return s, ERROR_NONE;
}

@private
_lstat :: proc(path: string) -> (OS_Stat, Errno) {
	cstr := strings.clone_to_cstring(path, context.temp_allocator);

	s: OS_Stat;
	result := _unix_lstat(cstr, &s);
	if result == -1 {
		return s, Errno(get_last_error());
	}
	return s, ERROR_NONE;
}

@private
_fstat :: proc(fd: Handle) -> (OS_Stat, Errno) {
	s: OS_Stat;
	result := _unix_fstat(fd, &s);
	if result == -1 {
		return s, Errno(get_last_error());
	}
	return s, ERROR_NONE;
}

@private
_fdopendir :: proc(fd: Handle) -> (Dir, Errno) {
	dirp := _unix_fdopendir(fd);
	if dirp == cast(Dir)nil {
		return nil, Errno(get_last_error());
	}
	return dirp, ERROR_NONE;
}

@private
_closedir :: proc(dirp: Dir) -> Errno {
	rc := _unix_closedir(dirp);
	if rc != 0 {
		return Errno(get_last_error());
	}
	return ERROR_NONE;
}

@private
_rewinddir :: proc(dirp: Dir) {
	_unix_rewinddir(dirp);
}

@private
_readdir :: proc(dirp: Dir) -> (entry: Dirent, err: Errno, end_of_stream: bool) {
	result: ^Dirent;
	rc := _unix_readdir_r(dirp, &entry, &result);

	if rc != 0 {
		err = Errno(get_last_error());
		return;
	}
	err = ERROR_NONE;

	if result == nil {
		end_of_stream = true;
		return;
	}
	end_of_stream = false;

	return;
}

@private
_readlink :: proc(path: string) -> (string, Errno) {
	path_cstr := strings.clone_to_cstring(path, context.temp_allocator);

	bufsz : uint = 256;
	buf := make([]byte, bufsz);
	for {
		rc := _unix_readlink(path_cstr, &(buf[0]), bufsz);
		if rc == -1 {
			delete(buf);
			return "", Errno(get_last_error());
		} else if rc == int(bufsz) {
			// NOTE(laleksic, 2021-01-21): Any cleaner way to resize the slice?
			bufsz *= 2;
			delete(buf);
			buf = make([]byte, bufsz);
		} else {
			return strings.string_from_ptr(&buf[0], rc), ERROR_NONE;
		}
	}
}

absolute_path_from_handle :: proc(fd: Handle) -> (string, Errno) {
	buf : [256]byte;
	fd_str := strconv.itoa( buf[:], cast(int)fd );

	procfs_path := strings.concatenate( []string{ "/proc/self/fd/", fd_str } );
	defer delete(procfs_path);

	return _readlink(procfs_path);
}

absolute_path_from_relative :: proc(rel: string) -> (path: string, err: Errno) {
	rel := rel;
	if rel == "" {
		rel = ".";
	}

	rel_cstr := strings.clone_to_cstring(rel, context.temp_allocator);

	path_ptr := _unix_realpath(rel_cstr, nil);
	if path_ptr == nil {
		return "", Errno(get_last_error());
	}
	defer _unix_free(path_ptr);

	path_cstr := transmute(cstring)path_ptr;
	path = strings.clone( string(path_cstr) );

	return path, ERROR_NONE;
}

access :: proc(path: string, mask: int) -> bool {
	cstr := strings.clone_to_cstring(path, context.temp_allocator);
	return _unix_access(cstr, mask) == 0;
}

heap_alloc :: proc(size: int) -> rawptr {
	assert(size > 0);
	return _unix_calloc(1, size);
}
heap_resize :: proc(ptr: rawptr, new_size: int) -> rawptr {
	return _unix_realloc(ptr, new_size);
}
heap_free :: proc(ptr: rawptr) {
	_unix_free(ptr);
}

getenv :: proc(name: string) -> (string, bool) {
	path_str := strings.clone_to_cstring(name, context.temp_allocator);
	cstr := _unix_getenv(path_str);
	if cstr == nil {
		return "", false;
	}
	return string(cstr), true;
}

get_current_directory :: proc() -> string {
	page_size := get_page_size(); // NOTE(tetra): See note in os_linux.odin/get_current_directory.
	buf := make([dynamic]u8, page_size);
	for {
		cwd := _unix_getcwd(cstring(raw_data(buf)), c.size_t(len(buf)));
		if cwd != nil {
			return string(cwd);
		}
		if Errno(get_last_error()) != ERANGE {
			return "";
		}
		resize(&buf, len(buf)+page_size);
	}
	unreachable();
}

set_current_directory :: proc(path: string) -> (err: Errno) {
	cstr := strings.clone_to_cstring(path, context.temp_allocator);
	res := _unix_chdir(cstr);
	if res == -1 {
		return Errno(get_last_error());
	}
	return ERROR_NONE;
}

exit :: proc "contextless" (code: int) -> ! {
	_unix_exit(code);
}

current_thread_id :: proc "contextless" () -> int {
	tid: u64;
	// NOTE(Oskar): available from OSX 10.6 and iOS 3.2.
	// For older versions there is `syscall(SYS_thread_selfid)`, but not really
	// the same thing apparently.
	foreign pthread { pthread_threadid_np :: proc "c" (rawptr, ^u64) -> c.int ---; }
	pthread_threadid_np(nil, &tid);
	return int(tid);
}

dlopen :: proc(filename: string, flags: int) -> rawptr {
	cstr := strings.clone_to_cstring(filename, context.temp_allocator);
	handle := _unix_dlopen(cstr, flags);
	return handle;
}
dlsym :: proc(handle: rawptr, symbol: string) -> rawptr {
	assert(handle != nil);
	cstr := strings.clone_to_cstring(symbol, context.temp_allocator);
	proc_handle := _unix_dlsym(handle, cstr);
	return proc_handle;
}
dlclose :: proc(handle: rawptr) -> bool {
	assert(handle != nil);
	return _unix_dlclose(handle) == 0;
}
dlerror :: proc() -> string {
	return string(_unix_dlerror());
}

get_page_size :: proc() -> int {
	// NOTE(tetra): The page size never changes, so why do anything complicated
	// if we don't have to.
	@static page_size := -1;
	if page_size != -1 {
		return page_size;
	}

	page_size = int(_unix_getpagesize());
	return page_size;
}


_alloc_command_line_arguments :: proc() -> []string {
	res := make([]string, len(runtime.args__));
	for arg, i in runtime.args__ {
		res[i] = string(arg);
	}
	return res;
}
