package os

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

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

OS :: "linux";

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


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(zangent): These are OS specific!
// Do not mix these up!
RTLD_LAZY         :: 0x001;
RTLD_NOW          :: 0x002;
RTLD_BINDING_MASK :: 0x3;
RTLD_GLOBAL       :: 0x100;

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

_File_Time :: struct {
	seconds:     i64,
	nanoseconds: i32,
	reserved:    i32,
}

// Translated from
//  https://android.googlesource.com/platform/prebuilts/gcc/linux-x86/host/x86_64-linux-glibc2.7-4.6/+/jb-dev/sysroot/usr/include/bits/stat.h
// Validity is not guaranteed.

Stat :: struct {
	device_id:     u64, // ID of device containing file
	serial:        u64, // File serial number
	nlink:         u32, // Number of hard links
	mode:          u32, // Mode of the file
	uid:           u32, // User ID of the file's owner
	gid:           u32, // Group ID of the file's group
	_padding:      i32, // 32 bits of padding
	rdev:          u64, // Device ID, if device
	size:          i64, // Size of the file, in bytes
	block_size:    i64, // Optimal bllocksize for I/O
	blocks:        i64, // Number of 512-byte blocks allocated

	last_access:   _File_Time, // Time of last access
	modified:      _File_Time, // Time of last modification
	status_change: _File_Time, // Time of last status change

	_reserve1,
	_reserve2,
	_reserve3:     i64,
	serial_numbe:  u64, // File serial number..? Maybe.
	_reserve4:     i64,
};

// File type
S_IFMT   :: 0170000; // Type of file mask
S_IFIFO  :: 0010000; // Named pipe (fifo)
S_IFCHR  :: 0020000; // Character special
S_IFDIR  :: 0040000; // Directory
S_IFBLK  :: 0060000; // Block special
S_IFREG  :: 0100000; // Regular
S_IFLNK  :: 0120000; // Symbolic link
S_IFSOCK :: 0140000; // Socket

// File mode
// Read, write, execute/search by owner
S_IRWXU :: 0000700; // RWX mask for owner
S_IRUSR :: 0000400; // R for owner
S_IWUSR :: 0000200; // W for owner
S_IXUSR :: 0000100; // X for owner

	// Read, write, execute/search by group
S_IRWXG :: 0000070; // RWX mask for group
S_IRGRP :: 0000040; // R for group
S_IWGRP :: 0000020; // W for group
S_IXGRP :: 0000010; // X for group

	// Read, write, execute/search by others
S_IRWXO :: 0000007; // RWX mask for other
S_IROTH :: 0000004; // R for other
S_IWOTH :: 0000002; // W for other
S_IXOTH :: 0000001; // X for other

S_ISUID :: 0004000; // Set user id on execution
S_ISGID :: 0002000; // Set group id on execution
S_ISVTX :: 0001000; // Directory restrcted delete


S_ISLNK  :: inline proc(m: u32) -> bool do return (m & S_IFMT) == S_IFLNK;
S_ISREG  :: inline proc(m: u32) -> bool do return (m & S_IFMT) == S_IFREG;
S_ISDIR  :: inline proc(m: u32) -> bool do return (m & S_IFMT) == S_IFDIR;
S_ISCHR  :: inline proc(m: u32) -> bool do return (m & S_IFMT) == S_IFCHR;
S_ISBLK  :: inline proc(m: u32) -> bool do return (m & S_IFMT) == S_IFBLK;
S_ISFIFO :: inline proc(m: u32) -> bool do return (m & S_IFMT) == S_IFIFO;
S_ISSOCK :: 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="open")    _unix_open    :: proc(path: cstring, mode: int) -> Handle ---;
	@(link_name="close")   _unix_close   :: proc(fd: Handle) -> i32 ---;
	@(link_name="read")    _unix_read    :: proc(fd: Handle, buf: rawptr, size: int) -> int ---;
	@(link_name="write")   _unix_write   :: proc(fd: Handle, buf: rawptr, size: int) -> int ---;
	@(link_name="lseek64") _unix_seek    :: proc(fd: Handle, offset: i64, whence: i32) -> i64 ---;
	@(link_name="gettid")  _unix_gettid  :: proc() -> u64 ---;
	@(link_name="stat")    _unix_stat    :: proc(path: cstring, stat: ^Stat) -> i32 ---;
	@(link_name="access")  _unix_access  :: proc(path: cstring, mask: int) -> i32 ---;

	@(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="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 ---;
}

// TODO(zangent): Change this to just `open` when Bill fixes overloading.
open_simple :: proc(path: string, mode: int) -> (Handle, Errno) {
	cstr := strings.new_cstring(path);
	handle := _unix_open(cstr, mode);
	delete(cstr);
	if(handle == -1) {
		return 0, 1;
	}
	return handle, 0;
}
// NOTE(zangent): This is here for compatability reasons. Should this be here?
open :: proc(path: string, mode: int = O_RDONLY, perm: u32 = 0) -> (Handle, Errno) {
	return open_simple(path, mode);
}

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

read :: proc(fd: Handle, data: []byte) -> (int, Errno) {
	sz := _unix_read(fd, &data[0], len(data));
	return sz, 0;
}

write :: proc(fd: Handle, data: []byte) -> (int, Errno) {
	sz := _unix_write(fd, &data[0], len(data));
	return sz, 0;
}

seek :: proc(fd: Handle, offset: i64, whence: int) -> (i64, Errno) {
	res := _unix_seek(fd, offset, i32(whence));
	return res, 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 size, err;
}


// NOTE(bill): Uses startup to initialize it

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

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

stat :: inline proc(path: string) -> (Stat, int) {
	cstr := strings.new_cstring(path);
	defer delete(cstr);

	s: Stat;
	ret_int := _unix_stat(cstr, &s);
	return s, int(ret_int);
}

access :: inline proc(path: string, mask: int) -> bool {
	cstr := strings.new_cstring(path);
	defer delete(cstr);
	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.new_cstring(name);
	defer delete(path_str);
	cstr := _unix_getenv(path_str);
	if cstr == nil {
		return "", false;
	}
	return string(cstr), true;
}

exit :: proc(code: int) {
	_unix_exit(code);
}

current_thread_id :: proc() -> int {
	// return int(_unix_gettid());
	return 0;
}

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


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