sandwich/src/main.rs

use std::fs;
use std::env;
use std::fmt;
use std::usize;

struct Program {
    data: Vec<String>,
    pc: usize
}

impl Program {
    fn from_string(program: String) -> Program {
        let mut op_list: Vec<String> = Vec::new();
        
        for opcode in program.split(" ").collect::<Vec<&str>>() {
            let mut new_op = opcode.to_owned();
            new_op = new_op.replace("\n", "");

            if new_op.len() != 0 {
                op_list.push(new_op.to_owned());
            }
        }
        return Program{ data: op_list, pc: 0 };
    }

    fn eval(&self, instruction: &String) {
        let instruction_vec: Vec<char> = instruction.chars().collect();
        let opcode = instruction_vec[0];
        let arguments = &instruction[1..];

        match opcode {
            'p' => println!("{}", arguments),
            _ => panic!("SyntaxError at opcode {}!", self.pc)
        }
    }

    fn run(&mut self) {
        println!("{}", self);
        while self.pc < self.data.len() {
            let instruction = &self.data[self.pc];

            self.eval(instruction);

            self.pc = self.pc + 1;
        }
    }
}

impl fmt::Display for Program {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "Program ({:?})", self.data)
    }
}

fn main() {

    let args: Vec<String> = env::args().collect();
    if args.len() == 1 {
        panic!("You must provide an argument!");
    }

    let filename = &args[1];

    let contents = fs::read_to_string(filename).expect("Something went wrong reading the file");
    let mut prog = Program::from_string(contents);
    prog.run();
}