package os

foreign import dl "system:dl"
foreign import libc "system:c"

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

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

INVALID_HANDLE :: ~Handle(0);

ERROR_NONE:      Errno : 0;
EPERM:           Errno : 1;
ENOENT:          Errno : 2;
ESRCH:           Errno : 3;
EINTR:           Errno : 4;
EIO:             Errno : 5;
ENXIO:           Errno : 6;
E2BIG:           Errno : 7;
ENOEXEC:         Errno : 8;
EBADF:           Errno : 9;
ECHILD:          Errno : 10;
EBEADLK:         Errno : 11;
ENOMEM:          Errno : 12;
EACCESS:         Errno : 13;
EFAULT:          Errno : 14;
ENOTBLK:         Errno : 15;
EBUSY:           Errno : 16;
EEXIST:          Errno : 17;
EXDEV:           Errno : 18;
ENODEV:          Errno : 19;
ENOTDIR:         Errno : 20;
EISDIR:          Errno : 21;
EINVAL:          Errno : 22;
ENFILE:          Errno : 23;
EMFILE:          Errno : 24;
ENOTTY:          Errno : 25;
ETXTBSY:         Errno : 26;
EFBIG:           Errno : 27;
ENOSPC:          Errno : 28;
ESPIPE:          Errno : 29;
EROFS:           Errno : 30;
EMLINK:          Errno : 31;
EPIPE:           Errno : 32;
EDOM:            Errno : 33;
ERANGE:          Errno : 34; /* Result too large */
EAGAIN:          Errno : 35;
EINPROGRESS:     Errno : 36;
EALREADY:        Errno : 37;
ENOTSOCK:        Errno : 38;
EDESTADDRREQ:    Errno : 39;
EMSGSIZE:        Errno : 40;
EPROTOTYPE:      Errno : 41;
ENOPROTOOPT:     Errno : 42;
EPROTONOSUPPORT: Errno : 43;
ESOCKTNOSUPPORT: Errno : 44;
EOPNOTSUPP:      Errno : 45;
EPFNOSUPPORT:    Errno : 46;
EAFNOSUPPORT:    Errno : 47;
EADDRINUSE:      Errno : 48;
EADDRNOTAVAIL:   Errno : 49;
ENETDOWN:        Errno : 50;
ENETUNREACH:     Errno : 51;
ENETRESET:       Errno : 52;
ECONNABORTED:    Errno : 53;
ECONNRESET:      Errno : 54;
ENOBUFS:         Errno : 55;
EISCONN:         Errno : 56;
ENOTCONN:        Errno : 57;
ESHUTDOWN:       Errno : 58;
ETIMEDOUT:       Errno : 60;
ECONNREFUSED:    Errno : 61;
ELOOP:           Errno : 62;
ENAMETOOLING:    Errno : 63;
EHOSTDOWN:       Errno : 64;
EHOSTUNREACH:    Errno : 65;
ENOTEMPTY:       Errno : 66;
EPROCLIM:        Errno : 67;
EUSERS:          Errno : 68;
EDQUOT:          Errno : 69;
ESTALE:          Errno : 70;
EBADRPC:         Errno : 72;
ERPCMISMATCH:    Errno : 73;
EPROGUNAVAIL:    Errno : 74;
EPROGMISMATCH:   Errno : 75;
EPROCUNAVAIL:    Errno : 76;
ENOLCK:          Errno : 77;
ENOSYS:          Errno : 78;
EFTYPE:          Errno : 79;
EAUTH:           Errno : 80;
ENEEDAUTH:       Errno : 81;
EIDRM:           Errno : 82;
ENOMSG:          Errno : 83;
EOVERFLOW:       Errno : 84;
ECANCELED:       Errno : 85;
EILSEQ:          Errno : 86;
ENOATTR:         Errno : 87;
EDOOFUS:         Errno : 88;
EBADMSG:         Errno : 89;
EMULTIHOP:       Errno : 90;
ENOLINK:         Errno : 91;
EPROTO:          Errno : 92;
ENOTCAPABLE:     Errno : 93;
ECAPMODE:        Errno : 94;
ENOTRECOVERABLE: Errno : 95;
EOWNERDEAD:      Errno : 96;

O_RDONLY   :: 0x00000;
O_WRONLY   :: 0x00001;
O_RDWR     :: 0x00002;
O_CREATE   :: 0x00040;
O_EXCL     :: 0x00080;
O_NOCTTY   :: 0x00100;
O_TRUNC    :: 0x00200;
O_NONBLOCK :: 0x00800;
O_APPEND   :: 0x00400;
O_SYNC     :: 0x01000;
O_ASYNC    :: 0x02000;
O_CLOEXEC  :: 0x80000;


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

// NOTE: These are OS specific!
// Do not mix these up!
RTLD_LAZY         :: 0x001;
RTLD_NOW          :: 0x002;
//RTLD_BINDING_MASK :: 0x3; // Called MODEMASK in dlfcn.h
RTLD_GLOBAL       :: 0x100;
RTLD_LOCAL        :: 0x000;
RTLD_TRACE        :: 0x200;
RTLD_NODELETE     :: 0x01000;
RTLD_NOLOAD       :: 0x02000;

args := _alloc_command_line_arguments();

Unix_File_Time :: struct {
	seconds: i64,
	nanoseconds: c.long,
}

pid_t :: u32;

OS_Stat :: struct {
	device_id: u64,
	serial: u64,
	nlink: u64,
	mode: u32,
	_padding0: i16,
	uid: u32,
	gid: u32,
	_padding1: i32,
	rdev: u64,

	last_access: Unix_File_Time,
	modified: Unix_File_Time,
	status_change: Unix_File_Time,
	birthtime: Unix_File_Time,

	size: i64,
	blocks: i64,
	block_size: i32,

	flags: u32,
	gen: u64,
	lspare: i64,
}

// 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
//S_ISVTX  :: 0o001000; // Save swapped text even after use

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

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

foreign libc {
	@(link_name="__error") __errno_location :: proc() -> ^int ---;
	@(link_name="syscall")          syscall          :: proc(number: Syscall, #c_vararg args: ..any) -> int ---;

	@(link_name="open")             _unix_open       :: proc(path: cstring, flags: c.int, mode: c.int) -> Handle ---;
	@(link_name="close")            _unix_close         :: proc(fd: Handle) -> c.int ---;
	@(link_name="read")             _unix_read          :: proc(fd: Handle, buf: rawptr, size: c.size_t) -> c.ssize_t ---;
	@(link_name="write")            _unix_write         :: proc(fd: Handle, buf: rawptr, size: c.size_t) -> c.ssize_t ---;
	@(link_name="lseek64")          _unix_seek          :: proc(fd: Handle, offset: i64, whence: c.int) -> i64 ---;
	@(link_name="gettid")           _unix_gettid        :: proc() -> u64 ---;
	@(link_name="getpagesize")      _unix_getpagesize   :: proc() -> c.int ---;
	@(link_name="stat64")           _unix_stat          :: proc(path: cstring, stat: ^OS_Stat) -> c.int ---;
	@(link_name="fstat")            _unix_fstat         :: proc(fd: Handle, stat: ^OS_Stat) -> c.int ---;
	@(link_name="access")           _unix_access        :: proc(path: cstring, mask: c.int) -> c.int ---;

	@(link_name="malloc")           _unix_malloc        :: proc(size: c.size_t) -> rawptr ---;
	@(link_name="calloc")           _unix_calloc        :: proc(num, size: c.size_t) -> rawptr ---;
	@(link_name="free")             _unix_free          :: proc(ptr: rawptr) ---;
	@(link_name="realloc")          _unix_realloc       :: proc(ptr: rawptr, size: c.size_t) -> 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="exit")             _unix_exit          :: proc(status: c.int) -> ! ---;
}
foreign dl {
	@(link_name="dlopen")           _unix_dlopen        :: proc(filename: cstring, flags: c.int) -> rawptr ---;
	@(link_name="dlsym")            _unix_dlsym         :: proc(handle: rawptr, symbol: cstring) -> rawptr ---;
	@(link_name="dlclose")          _unix_dlclose       :: proc(handle: rawptr) -> c.int ---;
	@(link_name="dlerror")          _unix_dlerror       :: proc() -> cstring ---;

	@(link_name="pthread_getthreadid_np") pthread_getthreadid_np :: proc() -> c.int ---;
}

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

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

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

close :: proc(fd: Handle) -> Errno {
	result := _unix_close(fd);
	if result == -1 {
		return Errno(get_last_error());
	}
	return ERROR_NONE;
}

read :: proc(fd: Handle, data: []byte) -> (int, Errno) {
	bytes_read := _unix_read(fd, &data[0], c.size_t(len(data)));
	if bytes_read == -1 {
		return -1, Errno(get_last_error());
	}
	return int(bytes_read), ERROR_NONE;
}

write :: proc(fd: Handle, data: []byte) -> (int, Errno) {
	if len(data) == 0 {
		return 0, ERROR_NONE;
	}
	bytes_written := _unix_write(fd, &data[0], c.size_t(len(data)));
	if bytes_written == -1 {
		return -1, Errno(get_last_error());
	}
	return int(bytes_written), ERROR_NONE;
}

seek :: proc(fd: Handle, offset: i64, whence: int) -> (i64, Errno) {
	res := _unix_seek(fd, offset, c.int(whence));
	if res == -1 {
		return -1, Errno(get_last_error());
	}
	return res, ERROR_NONE;
}

file_size :: proc(fd: Handle) -> (i64, Errno) {
	s, err := fstat(fd);
	if err != ERROR_NONE {
		return -1, err;
	}
	return s.size, ERROR_NONE;
}

stdin: Handle = 0;
stdout: Handle = 1;
stderr: Handle = 2;

last_write_time :: proc(fd: Handle) -> (File_Time, Errno) {
	s, err := fstat(fd);
	if err != ERROR_NONE {
		return 0, err;
	}
	modified := s.modified.seconds * 1_000_000_000 + s.modified.nanoseconds;
	return File_Time(modified), ERROR_NONE;
}

last_write_time_by_name :: proc(name: string) -> (File_Time, Errno) {
	s, err := stat(name);
	if err != ERROR_NONE {
		return 0, err;
	}
	modified := s.modified.seconds * 1_000_000_000 + s.modified.nanoseconds;
	return File_Time(modified), ERROR_NONE;
}

stat :: proc(path: string) -> (OS_Stat, Errno) {
	cstr := strings.clone_to_cstring(path);
	defer delete(cstr);

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

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;
}

access :: proc(path: string, mask: int) -> (bool, Errno) {
	cstr := strings.clone_to_cstring(path);
	defer delete(cstr);
	result := _unix_access(cstr, c.int(mask));
	if result == -1 {
		return false, Errno(get_last_error());
	}
	return true, ERROR_NONE;
}

heap_alloc :: proc(size: int) -> rawptr {
	assert(size >= 0);
	return _unix_calloc(1, c.size_t(size));
}

heap_resize :: proc(ptr: rawptr, new_size: int) -> rawptr {
	return _unix_realloc(ptr, c.size_t(new_size));
}

heap_free :: proc(ptr: rawptr) {
	_unix_free(ptr);
}

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

get_current_directory :: proc() -> string {
	// NOTE(tetra): I would use PATH_MAX here, but I was not able to find
	// an authoritative value for it across all systems.
	// The largest value I could find was 4096, so might as well use the page size.
	page_size := get_page_size();
	buf := make([dynamic]u8, page_size);
	#no_bounds_check for {
		cwd := _unix_getcwd(cstring(&buf[0]), 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 do return Errno(get_last_error());
	return ERROR_NONE;
}

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

current_thread_id :: proc "contextless" () -> int {
	return cast(int) pthread_getthreadid_np();
}

dlopen :: proc(filename: string, flags: int) -> rawptr {
	cstr := strings.clone_to_cstring(filename);
	defer delete(cstr);
	handle := _unix_dlopen(cstr, c.int(flags));
	return handle;
}
dlsym :: proc(handle: rawptr, symbol: string) -> rawptr {
	assert(handle != nil);
	cstr := strings.clone_to_cstring(symbol);
	defer delete(cstr);
	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 do 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;
}