%include "src/constants.asm"

extern	__INTERNAL_fmt

extern	strlen
extern	umask_get

section .rodata
	; Open flags
	O_ACCMODE	equ	00000003q
	O_RDONLY	equ	00000000q
	O_WRONLY	equ	00000001q
	O_RDWR		equ	00000002q
	O_CREAT		equ	00000100q ;create if not exist
	O_EXCL		equ	00000200q ;fail if file exists and O_EXCL+O_CREAT set
	O_NOCTTY	equ	00000400q
	O_TRUNC		equ	00001000q
	O_APPEND	equ	00002000q
	O_NONBLOCK	equ	00004000q
	O_DSYNC		equ	00010000q
	FASYNC		equ	00020000q
	O_DIRECT	equ	00040000q
	O_LARGEFILE	equ	00100000q
	O_DIRECTORY	equ	00200000q
	O_NOFOLLOW	equ	00400000q
	O_NOATIME	equ	01000000q
	O_CLOEXEC	equ	02000000q
	__O_SYNC	equ	04000000q
	O_SYNC		equ	(__O_SYNC | O_DSYNC)
	O_PATH		equ	01000000q
	__O_TMPFILE	equ	02000000q
	O_TMPFILE	equ	(__O_TMPFILE | O_DIRECTORY)
	O_NDELAY	equ	O_NONBLOCK
	; Permission flags
	S_IXOTH		equ	00001q ;o=x
	S_IWOTH		equ	00002q ;o=w
	S_IROTH		equ	00004q ;o=r
	S_IRWXO		equ	00007q ;o=rwx
	S_IXGRP		equ	00010q ;g=x
	S_IWGRP		equ	00020q ;g=w
	S_IRGRP		equ	00040q ;g=r
	S_IRWXG		equ	00070q ;g=rwx
	S_IXUSR		equ	00100q ;u=x
	S_IWUSR		equ	00200q ;u=w
	S_IRUSR		equ	00400q ;u=r
	S_IRWXU		equ	00700q ;u=rwx
	S_ISVIX		equ	0001000q ;sticky bit
	S_ISGID		equ	0002000q ;set-group-ID bit
	S_ISUID		equ	0004000q ;set-user-ID bit

section .bss

section .text
	global	fopen
	global	fclose
	global	fexist
	global	fwrite

;----- fopen(*file[], char mode) -----;
; Opens a file
; Return value: Pointer to opened file pointer, -errno otherwise
; Possible modes:
;	'r'	Read-only, file must exist
;	'w'	Write-only. Creates empty file or truncates an existing file
;	'a'	Append. Creates file if it does not exist
;	'R'	Read+write, file must exist
;	'W'	Read+write. Creates empty file or truncates an existing file
;	'A'	Read+append. Creates file if it does not exist
;	<!>	Invalid mode will also return 0 (EOS)
; Used registers:
;	rax*	(ret)
;	rdi	(arg) Pointer to string holding (path+)file name
;	rsi	Mode to open the file with (see description above)
fopen:
	%macro createFile 1
	push	rdi
	push	rsi
	call	fexist
	pop	rsi
	pop	rdi
	test	rax, 1
	jz	%%createFile
	jmp	%1
	%%createFile:
	push	rsi
	push	rdi
	call	umask_get
	pop	rdi
	push	rdi
	not	rax
	mov	rsi, 0666q
	and	rsi, rax
	mov	rax, NR_creat
	syscall
	pop	rdi
	pop	rsi
	%endmacro
	;;;
	;;; ENTRY
	;;;
	sub	rsp, SIZE_QWORD

	cmp	sil, 'r'
	je	.setMode_r
	cmp	sil, 'w'
	je	.setMode_w
	cmp	sil, 'a'
	je	.setMode_a
	cmp	sil, 'R'
	je	.setMode_R
	cmp	sil, 'W'
	je	.setMode_W
	cmp	sil, 'A'
	je	.setMode_A
	mov	rax, -EINVAL
	jmp	.quit

	.setMode_r:
	mov	rsi, O_RDONLY
	jmp	.open
	.setMode_w:
		createFile .open_w
	.open_w:
	mov	rsi, O_WRONLY | O_TRUNC
	jmp	.open
	.setMode_a:
		createFile .open_a
	.open_a:
	mov	rsi, O_WRONLY | O_APPEND
	jmp	.open
	.setMode_R:
	mov	rsi, O_RDWR
	jmp	.open
	.setMode_W:
		createFile .open_W
	.open_W:
	mov	rsi, O_RDWR | O_TRUNC
	jmp	.open
	.setMode_A:
		createFile .open_A
	.open_A:
	mov	rsi, O_RDWR | O_APPEND
	jmp	.open

	.open:
	mov	rax, NR_open
	syscall

	.quit:
	add	rsp, SIZE_QWORD
	ret

;----- fclose(*filePointer) -----;
; Closes an opened file
; Return value: 0 if file closed. Negative error number if an error occured
; Used registers:
;	rax*	(ret)
;	rdi	(arg) Pointer to opened file
fclose:
	sub	rsp, SIZE_QWORD
	cmp	rdi, 3
	jl	.invalid_fd ;disallow closing stdin,stdout,stderr
	mov	rax, NR_close
	syscall
	jmp	.quit

	.invalid_fd:
	mov	rax, -EINVAL

	.quit:
	add	rsp, SIZE_QWORD
	ret

;----- fexist(*file[]) -----;
; Checks if given file exists (attempts to open the file)
; Return value: 1- File exists. 0- File does not exist or is a directory
; Used registers:
;	rax*	(ret)
;	rdi	(arg) Pointer to string holding (path+)file name
fexist:
	sub	rsp, SIZE_QWORD
	mov	rsi, 'r'
	call	fopen
	test	rax, rax
	js	.not_exist
	mov	rdi, rax
	call	fclose
	mov	rax, 1
	jmp	.quit
	.not_exist:
	xor	rax, rax
	.quit:
	add	rsp, SIZE_QWORD
	ret

;--- fwrite(*filePointer, *data[], ...) -----;
; Writes data to given file. Allows format specifiers and variable arguments (see `__INTERNAL_fmt` for supported specifiers)
; Return value: Length of given string(data[]), 0 if nothing was written (eg invalid file or file not writable, or data[] is empty)
; Used registers:
;	rax*	(ret)
;	rdi	(arg) Pointer to file
;	rsi	(arg) Data to write
fwrite:
	push	rbp
	mov	rbp, rsp
	cmp	rdi, 2
	jg	.cnt
	xor	rax, rax
	leave
	ret
	.cnt:
	mov	rax, rdi
	mov	rdi, rsi
	mov	rsi, rdx
	mov	rdx, rcx
	mov	rcx, r8
	mov	r8, r9
	mov	r9, [rbp + RBP_OFFSET_CALLER]
	call	__INTERNAL_fmt
	leave
	ret