format ELF64 executable

macro genclass class, class_len
{
 	;; Generate 16 bits (smallest) of randomness from the cpu
 	rdrand ax
 
 	;; Modulo into len range to index in
	xor rdx, rdx
 	mov rbx, class_len
 	div bx

	;; Save output letter into out_buf, bump rcx
	add rdx, class
	mov rdx, [rdx]
	mov [rcx], rdx
	inc rcx

	inc rsi
}

segment readable executable

entry main
main:
	;; No arg preload case
	cmp [rsp], word 1
	jne argparse

	mov r8, qword 3
	mov r9, qword 2
	mov r10, qword 3

	jmp generate
	
argparse:
	;; Check args (need 3)
	cmp [rsp], word 3
	jle fail

	;; load arg1
	mov r8, [rsp+16]
	mov r8, [r8]
	and r8, 0xFF
	sub r8, 48

	;; load arg2
	mov r9, [rsp+24]
	mov r9, [r9]
	and r9, 0xFF
	sub r9, 48

	;; load arg3
	mov r10, [rsp+32]
	mov r10, [r10]
	and r10, 0xFF
	sub r10, 48

generate:
	;; Store which output byte we're up to in rcx
	mov rcx, out_buf
	;; Store chars generated in rsi
	xor rsi, rsi

tripleter:
	genclass consonants, consonants_len
	genclass vowels, vowels_len
	genclass consonants, consonants_len
	dec r8
	test r8, r8
	jnz tripleter
symboler:
	genclass symbols, symbols_len
	dec r9
	test r9, r9
	jnz symboler
numberer:
	genclass numbers, numbers_len
	dec r10
	test r10, r10
	jnz numberer

	;; Append new line to string
	mov [rcx], word 10
	inc rsi

	;; Special case to caps the first character
	xor rax, rax
	mov al, byte [out_buf]
	sub al, 32
	mov rbx, out_buf
	mov [rbx], al

 	;; Write
 	mov rdi, 1  ;; stdout
 	mov rdx, rsi
 	mov rsi, out_buf
 	mov rax, 0x01
 	syscall
 
 	;; Exit (code 0)
 	mov rdi, 0
 	mov rax, 0x3c
 	syscall

fail:
 	;; Write
 	mov rdi, 1  ;; stdout
 	mov rsi, usage
 	mov rdx, usage_len
 	mov rax, 0x01
 	syscall
 
 	;; Exit 1
 	mov rdi, 1
 	mov rax, 0x3c
 	syscall

 
segment readable writeable

usage db "usage: passmgen [<triplet#> <symbol#> <number#>]", 10
usage_len = $ - usage

numbers db "0123456789"
numbers_len = $ - numbers
vowels db "aeiou"
vowels_len = $ - vowels
consonants db "bcdfghjklmnpqrstvwxyz"
consonants_len = $ - consonants
symbols db "!@#$%&()-=_+[]{}\\|;<>/?."
symbols_len = $ - symbols

out_buf rb 64