use crate::commands::is_piped;

/// Get the calculator vars (`math_op`, `first_number`, `second_number`) for calc.
pub fn get_calc_vars(problem: &str) -> (&str, i32, i32) {
    let math_op = if problem.contains('x') {
        "x"
    } else if problem.contains('*') {
        "*"
    } else if problem.contains('/') {
        "/"
    } else if problem.contains('%') {
        "%"
    } else if problem.contains('+') {
        "+"
    } else if problem.contains('-') {
        "-"
    } else {
        ""
    };
    let problem_vector: Vec<&str> = problem.split(math_op).collect();
    let first_number: i32 = problem_vector[0].parse().unwrap();
    let second_number: i32 = problem_vector[1].parse().unwrap();
    (math_op, first_number, second_number)
}

/// Takes the `args` part of a `ShellCommand` struct,
/// and tries to evaluate the given mathematical expression,
/// returning a String with the result.
pub fn calc(args: &[String]) -> String {
    let mut output = String::new();
    is_piped(args, "calc");
    let problem = args.concat();
    let (math_op, first_number, second_number) = get_calc_vars(&problem);
    match math_op {
        // Multiplication
        "x" | "*" => output.push_str(format!("{}", first_number * second_number).as_str()),
        // Division
        "/" => output.push_str(format!("{}", first_number / second_number).as_str()),
        // Division with remainder
        "%" => output.push_str(format!("{}", first_number % second_number).as_str()),
        // Addition
        "+" => output.push_str(format!("{}", first_number + second_number).as_str()),
        // Subtraction
        "-" => output.push_str(format!("{}", first_number - second_number).as_str()),
        _ => output.push_str(format!("Error, '{}' is an unsupported operation.", math_op).as_str()),
    }
    output
}