//assemble rout.asm on mac with following command
//nasm -f macho64 rout.asm && clang rout.o -Wl,-no_pie -o a.out

use std::fs::File;
use std::io::Write;

fn savetofile(filename: &str, data: &str){
    let mut f = File::create(filename).expect("Unable to create file");
    f.write_all(data.as_bytes()).expect("Unable to write data");
}

fn main() {
    let header = "default rel

%macro fs 2
    push rax
    push rbx
    push rcx
    push rdx
    push rdi
    push rsi
    push rbp
    push %2
    %1
    pop rbp
    pop rsi
    pop rdi
    pop rdx
    pop rcx
    pop rbx
    pop rax
%endmacro

%macro outchar 0
    pop rsi
    push rbp
    mov rbp, rsp
    mov rdi, formatch
    xor rax, rax
    call _printf

    mov rsp, rbp
    pop rbp
%endmacro

extern _printf, _exit

section .data
    formatch db \"%c\", 0, 0
    tape times 1000 dq 0

section .text
    global _main
_main:
    push 0
    mov rbx, tape
    ";

    let mut output = "".to_string();
    output.push_str(header);
    let s = "++++++++++[>+++++++>++++++++++>+++>+<<<<-]>++.>+.+++++++..+++.>++.<<+++++++++++++++.>.+++.------.--------.>+.>.";
    let mut loopi = 0;
    let mut loopstack = Vec::new();
    for c in s.chars() {
        match c {
            '+' => {
                output.push_str("mov rax, qword [rbx]\n");
                output.push_str("add rax, 1\n");
                output.push_str("mov qword [rbx], rax\n");
            },
            '-' => {
                output.push_str("mov rax, qword [rbx]\n");
                output.push_str("sub rax, 1\n");
                output.push_str("mov qword [rbx], rax\n");
            },
            '>' => {
                output.push_str("add rbx, 8\n");
            },
            '<' => {
                output.push_str("sub rbx, 8\n");
            },
            '[' => {
                let name = format!("loop{}", loopi);
                output.push_str(&format!("{}:\n", name));
                loopstack.push(name);
                loopi += 1;
            },
            ']' => {
                output.push_str("cmp qword [rbx], 0\n");
                output.push_str(&format!("jne {}\n", loopstack.last().unwrap()));
                loopstack.pop();
            }
            '.' => {
                output.push_str("mov rcx, qword [rbx]\n");
                output.push_str("fs outchar, rcx\n");
            }
            _ => {},
        }
    }
    output.push_str("mov rdi, 0\n");
    output.push_str("call _exit\n");
    savetofile("rout.asm", &output);
}