global _start

section .data

format: db "%c %s", 10, 0
string: db "love", 10, 0
string_len: equ $ - string
buf: resb 64d

section .text

%define NEXT_PARAM R8
%define NEXT_FORMAT_SYMBOL RBP
%define BUFFER_SIZE RBX

%macro printf 1-*           ;macro with undefined qty of params
    %rep %0                 ;loop at all parameters
        %rotate -1          ;%1 now is the last parameter
        push %1             ;push last param into stack
    %endrep
    call handle
%endmacro

_start:
        xor BUFFER_SIZE, BUFFER_SIZE
        ;printf format, string, 3802, 100, '!', 127
        printf format, 'c', string
;------------------------------------------------------------\
;ENTRY:
;DESTR:
;------------------------------------------------------------|
handle:
        mov NEXT_PARAM, RSP
        add NEXT_PARAM, 8              ;[NEXT_PARAM] now is the last pushed arg -- format address
        mov NEXT_FORMAT_SYMBOL, [NEXT_PARAM]          ;NEXT_FORMAT_SYMBOL points to current format symbol
        add NEXT_PARAM, 8              ;NEXT_PARAM is current arg

        dec NEXT_FORMAT_SYMBOL
next:
        inc NEXT_FORMAT_SYMBOL

        cmp byte [NEXT_FORMAT_SYMBOL], 0       ;program ends by 0-symbol in format string
        je end_program

        cmp byte [NEXT_FORMAT_SYMBOL], '%'     ;if not '%' print source format symbol
        jne .simple

        inc NEXT_FORMAT_SYMBOL


        ;switch case
        cmp byte [NEXT_FORMAT_SYMBOL], '%'     ;case %%
        je .simple

        cmp byte [NEXT_FORMAT_SYMBOL], 'c'
        je .print_char

        cmp byte [NEXT_FORMAT_SYMBOL], 's'
        je .print_string

        cmp byte [NEXT_FORMAT_SYMBOL], 'd'
        je .print_decimal

        cmp byte [NEXT_FORMAT_SYMBOL], 'b'
        je .print_binary

        cmp byte [NEXT_FORMAT_SYMBOL], 'o'
        je .print_octal

        cmp byte [NEXT_FORMAT_SYMBOL], 'x'
        je .print_hex

.simple:
        mov RAX, [NEXT_FORMAT_SYMBOL]
        call to_buf
        jmp next

.print_char:
        mov RAX, [NEXT_PARAM]
        add NEXT_PARAM, 8
        call to_buf
        jmp next


.print_string:
        mov RSI, [NEXT_PARAM]
        add NEXT_PARAM, 8
.str_loop:
        mov RAX, [RSI]
        cmp RAX, 0
        je next

        call to_buf
        inc RSI
        jmp .str_loop


.print_decimal:
        mov RAX, [NEXT_PARAM]
        ;making the mask for last bit
        xor R9, R9
        inc R9
        shl R9, 31d

        ;looking for the sign of the number
        mov R10, [NEXT_PARAM]
        and R10, R9
        cmp R9, R10
        jne .positive_decimal

        ;print minus
        push RAX
        mov RAX, '-'
        call to_buf
        pop RAX

        ;get a positive value from negative
        not RAX
        inc RAX
.positive_decimal:
        mov R9, 10d
        call print_number
        add NEXT_PARAM, 8
        jmp next


.print_binary:
        call printf_symbols
        jmp next

.print_octal:
        call printf_symbols
        jmp next

.print_hex:
        call printf_symbols
        jmp next

;------------------------------------------------------------/


;------------------------------------------------------------\
;Prints a positive number
;ENTRY: R9 -- base
;       RAX -- number to print
;------------------------------------------------------------|
print_number:
        xor R10, R10            ;reversed value
        xor RDX, RDX
        xor RCX, RCX            ;number of digits
        mov R11, RAX

.reverse_loop:
        ;reverse digits in number
        mov RAX, R11
        div R9d

        shl R10, 4
        add R10, RDX

        mov R11, RAX
        inc RCX

        cmp R11, R9
        jae .reverse_loop

        shl R10, 4
        add R10, R11
        inc RCX

.print_loop:
        mov RAX, R10
        and RAX, 1111b
        add RAX, '0'
        call to_buf

        shr R10, 4
        dec RCX
        cmp RCX, 0
        jne .print_loop

        ret
;------------------------------------------------------------/


;------------------------------------------------------------\
;Puts a symbol into buf
;ENTRY: RAX - char to put
;------------------------------------------------------------|
to_buf:
        push RSI
        cmp BUFFER_SIZE, 64d
        jae from_buf

        mov RDI, buf
        add RDI, BUFFER_SIZE
        stosb
        inc BUFFER_SIZE

        pop RSI
        ret

;------------------------------------------------------------/

;------------------------------------------------------------\
;Prints a buffer's content on a screen
;------------------------------------------------------------|
from_buf:
        push RDX
        push RSI
        cmp BUFFER_SIZE, 0
        je .quit

        mov RDX, BUFFER_SIZE
        mov RSI, buf
        call printf_symbols
        xor BUFFER_SIZE, BUFFER_SIZE
.quit:
        pop RSI
        pop RDX
        ret
;------------------------------------------------------------/

;------------------------------------------------------------\
;ENTRY: RSI -- symbol address, RDX -- qty of symbols to print
;------------------------------------------------------------|
printf_symbols:
        push RAX
        push RDI

        xor RAX, RAX
        inc RAX

        xor RDI, RDI
        inc RDI

        syscall

        pop RDI
        pop RAX
        ret
;------------------------------------------------------------/

end_program:
        call from_buf
        mov RAX, 60
        xor RDI, RDI
        syscall